Nanoprobes and nanoswitches


Electrochemical tunneling spectroscopy and molecular dynamics simulations indicate that a reduced ionic density at the volume confined between redox protein partners hCc (left, orange) and pCc1 (right, green) causes an extended electric field (equipotential lines shown in the background) that allows long distance charge transport between them. Heme groups are highlighted in each protein (Lagunas et al., 2018). Image credit: Alba Nin-Hill.

The group’s research focuses on developing nanoscale tools to study biological systems. These tools include instrumentation based on proximity probes, such as electrochemical tunnelling microscopy and spectroscopy, that we apply to investigate electron transfer in metal oxides and individual redox proteins.

These studies are relevant to the development of biosensors and molecular electronics devices. In particular, based on our development of nanoscale field-effect transistors using individual redox protein, we have recently published a method to measure conductance switching in single redox proteins “wired” between two electrodes.

Rational structural modifications of the chemotherapy agent methotrexate enabled control of cytotoxic efficacy with light. In vitro and in vivo experiments showed that the new compound, named phototrexate, behaves as a potent antifolate in its photoactivated configuration, and that it is nearly inactive in its thermodynamically stable state. The insights provided by this work open up new possibilities for developing innovative agents for light-controlled precision chemotherapy. (Matera et al., 2018). Image credit: Carlo Matera &


Another set of nanotools that we are developing is based on molecular actuators that can be switched with light, such as azobenzene, which can be chemically attached to biomolecules in order to optically control their activity. We have demonstrated for the first time two-photon stimulation of neurons and astrocytes with azobenzene-based photoswitches. We have also developed several bioactive compounds that have been engineered to be regulated by light. These “optopharmacological” compounds include peptide inhibitors of protein-protein interactions involved in clathrin-mediated endocytosis, and two ligands of G protein-coupled receptors (adenosine and metabotropic glutamate receptors), which are important therapeutic targets.


Pau Gorostiza Langa | Group Leader / ICREA Research Professor
Ismael Díez Pérez | Senior Researcher
Marina Inés Giannotti | Senior Researcher
Mireia Oliva Herrera | Senior Researcher
Núria Camarero Palao | Postdoctoral Researcher
Rossella Castagna | Postdoctoral Researcher
Galyna Malieieva | Postdoctoral Researcher
Carlo Matera | Postdoctoral Researcher
Ricardo Zamora Brito | Postdoctoral Researcher
Luisa Camerin | PhD Student
Alexandre Gomila Juaneda | PhD Student
Manuel López Ortiz | PhD Student
Alejandro Martín Rodríguez | PhD Student
Davia Prischich | PhD Student
Fabio Riefolo | PhD Student
Rosalba Sortino | PhD Student
Beatriu Domingo Tafalla | Masters Student
Deborah Pirovano | Masters Student
Ramona Santini | Masters Student
Silvia Sodric Hidalgo | Masters Student
Silvia Gómez Coca | Visiting Researcher


EU-funded projects


Human Brain Project Specific Grant Agreement 2 (2018-2020) European Commission, FET FLAGSHIPS Pau Gorostiza
Human Brain Project Specific Grant Agreement 3 (2020-2023) European Commission, FET FLAGSHIPS Pau Gorostiza
National projects
Q-SPET Quantum-controlled Single Protein Electron Transport (2019-2020) BIST Ignite Program Pau Gorostiza
DECA CECH Cluster Emergente del Cerebro Humano (2019-2021) RIS3CAT – Tecnologies Emergents Pau Gorostiza
SGR Grups de recerca consolidats (2017-2020) AGAUR / SGR Pau Gorostiza
Privately funded projects
Drug4Sight Light-regulated drugs to restore sight (2019-2022) Obra Social La Caixa Pau Gorostiza
Finished projects
FOCUS Single Molecule Activation and Computing ICT Pau Gorostiza
THERALIGHT Therapeutic Applications of Light-Regulated Drugs ERC-PoC Pau Gorostiza
Single-BioET Single-molecule junction capabilities to map the electron pathways in redox bio-molecular architectures (2012-2016) MARIE CURIE – RG Ismael Díez
Optogenetic pacemaking to rewire neural circuits La Marató TV3 Pau Gorostiza
OPTOPHARMACOLOGY Aplicaciones terapéuticas de la optofarmacología MINECO (CTQ2013-43892-R) Pau Gorostiza
Milk fat globule membrane and periphera proteins: lipid-protein interactions (2016-2017) Fausto Sanz INRA
WaveScalES Human Brain Project Specific Grant Agreement 1 (2016-2018) European Commission, FET FLAGSHIPS Pau Gorostiza
OPTOFRAX Optopharmacological brain mapping of autism mouse (2015-2017) MARIE CURIE – IF Miquel Bosch
NANOPROSTHETICS Prótesis moleculares para restablecer la visión basadas en fotoconmutadores covalentes dirigidos (2016-2019) MINECO, Retos investigación: Proyectos I+D Pau Gorostiza
MODULIGHTOR Moduladores fotoconmutables sintéticos para manipular remotamente proteínas endógenas: fotocontrol in vivo de canales iónicos pentaméricos (2015-2018) MINECO Nacional /Acciones de Programación Conjunta Internacional Pau Gorostiza
nanoET-leukemia Nanoconductance of electron transfer proteins of the respiratory chain. Direct measurement at the single molecular level and therapeutic regulation in cancer stem cells (2015-2018) MINECO, Proyectos RETOS 2015 / CIBER Marina  Giannotti / Anna Lagunas
Inhibición fotoselectiva de interacciones proteína-proteína para el estudio de redes interactómicas y el desarrollo de nuevas terapias (2015-2018) Pau Gorostiza Fundación Ramon Areces
Fotoconmutadores covalentes para el control remoto de receptores endógenos (2017-2019) Pau Gorostiza Convocatoria de Ayudas a la Investigación FUNDALUCE


Rustler, Karin, Gomila, Alexandre, Maleeva, Galyna, Gorostiza, Pau, Bregestovski, Piotr, König, Burkhard, (2020). Optical Control of GABAA Receptors with a Fulgimide-Based Potentiator Chemistry - A European Journal Accepted Articles,

Optogenetic and photopharmacological tools to manipulate neuronal inhibition have limited efficacy and reversibility. We report the design, synthesis, and biological evaluation of Fulgazepam, a fulgimide derivative of benzodiazepine that behaves as a pure potentiator of ionotropic γ-aminobutyric acid receptors (GABA A Rs) and displays full and reversible photoswitching in vitro and in vivo. The compound enables high-resolution studies of GABAergic neurotransmission, and phototherapies based on localized, acute, and reversible neuroinhibition.

Maleeva, Galyna, Wutz, Daniel, Rustler, Karin, Nin-Hill, Alba, Rovira, Carme, Petukhova, Elena, Bautista-Barrufet, Antoni, Gomila-Juaneda, Alexandre, Scholze, Petra, Peiretti, Franck, Alfonso-Prieto, Mercedes, König, Burkhard, Gorostiza, Pau, Bregestovski, Piotr, (2019). A photoswitchable GABA receptor channel blocker British Journal of Pharmacology 176, (15), 2661-2677

BACKGROUND AND PURPOSE: Anion-selective Cys-loop receptors (GABA and glycine receptors) provide the main inhibitory drive in the CNS. Both types of receptor operate via chloride-selective ion channels, though with different kinetics, pharmacological profiles, and localization. Disequilibrium in their function leads to a variety of disorders, which are often treated with allosteric modulators. The few available GABA and glycine receptor channel blockers effectively suppress inhibitory currents in neurons, but their systemic administration is highly toxic. With the aim of developing an efficient light-controllable modulator of GABA receptors, we constructed azobenzene-nitrazepam (Azo-NZ1), which is composed of a nitrazepam moiety merged to an azobenzene photoisomerizable group. EXPERIMENTAL APPROACH: The experiments were carried out on cultured cells expressing Cys-loop receptors of known subunit composition and in brain slices using patch-clamp. Site-directed mutagenesis and molecular modelling approaches were applied to evaluate the mechanism of action of Azo-NZ1. KEY RESULTS: At visible light, being in trans‐configuration, Azo-NZ1 blocked heteromeric α1/β2/γ2 GABAA receptors, ρ2 GABAA (GABAC), and α2 glycine receptors, whereas switching the compound into cis-state by UV illumination restored the activity. Azo-NZ1 successfully photomodulated GABAergic currents recorded from dentate gyrus neurons. We demonstrated that in trans-configuration, Azo-NZ1 blocks the Cl-selective ion pore of GABA receptors interacting mainly with the 2′ level of the TM2 region. CONCLUSIONS AND IMPLICATIONS: Azo-NZ1 is a soluble light-driven Cl-channel blocker, which allows photo-modulation of the activity induced by anion-selective Cys-loop receptors. Azo-NZ1 is able to control GABAergic postsynaptic currents and provides new opportunities to study inhibitory neurotransmission using patterned illumination.

Cabré, Gisela, Garrido-Charles, Aida, Moreno, Miquel, Bosch, Miquel, Porta-de-la-Riva, Montserrat, Krieg, Michael, Gascón-Moya, Marta, Camarero, Núria, Gelabert, Ricard, Lluch, José M., Busqué, F., Hernando, Jordi, Gorostiza, Pau, Alibés, Ramon, (2019). Rationally designed azobenzene photoswitches for efficient two-photon neuronal excitation Nature Communications 10, (1), 907

Manipulation of neuronal activity using two-photon excitation of azobenzene photoswitches with near-infrared light has been recently demonstrated, but their practical use in neuronal tissue to photostimulate individual neurons with three-dimensional precision has been hampered by firstly, the low efficacy and reliability of NIR-induced azobenzene photoisomerization compared to one-photon excitation, and secondly, the short cis state lifetime of the two-photon responsive azo switches. Here we report the rational design based on theoretical calculations and the synthesis of azobenzene photoswitches endowed with both high two-photon absorption cross section and slow thermal back-isomerization. These compounds provide optimized and sustained two-photon neuronal stimulation both in light-scattering brain tissue and in Caenorhabditis elegans nematodes, displaying photoresponse intensities that are comparable to those achieved under one-photon excitation. This finding opens the way to use both genetically targeted and pharmacologically selective azobenzene photoswitches to dissect intact neuronal circuits in three dimensions.

Nevola, Laura, Varese, Monica, Martín-Quirós, Andrés, Mari, Giacomo, Eckelt, Kay, Gorostiza, Pau, Giralt, Ernest, (2019). Targeted nanoswitchable inhibitors of protein-protein interactions involved in apoptosis ChemMedChem 14, 100-106

Progress in drug delivery is hampered by the lack of efficient strategies to target drugs with high specificity and precise spatiotemporal regulation. The remote control of nanoparticles and drugs with light allows controlling their action site and dosage. Peptide-based drugs are very specific, non-immunogenic and can be designed to cross the plasma membrane. In order to combine target specificity and remote control of drug action, here we describe a versatile strategy based on a generalized template to design nanoswitchable peptides that modulate protein-protein interactions with light. This approach is demonstrated to photomodulate two important targets involved in apoptosis (the interactions Bcl-xL/Bak and MDM2/p53), but can be applied to a large pool of therapeutically relevant protein-protein interactions mediated by alpha helical motifs. The template can be adjusted using readily available information about the hot spots (residues contributing most to the binding energy) at the protein-protein interface of interest.

Lopez-Martinez, Montserrat, López-Ortiz, Manuel, Antinori, Maria Elena, Wientjes, Emilie, Nin-Hill, Alba, Rovira, Carme, Croce, Roberta, Díez-Pérez, Ismael, Gorostiza, Pau, (2019). Electrochemically gated long distance charge transport in photosystem I Angewandte Chemie International Edition 58, (38), 13280-13284

The transport of electrons along photosynthetic and respiratory chains involves a series of enzymatic reactions that are coupled through redox mediators, including proteins and small molecules. The use of native and synthetic redox probes is key to understand charge transport mechanisms, and to design bioelectronic sensors and solar energy conversion devices. However, redox probes have limited tunability to exchange charge at the desired electrochemical potentials (energy levels) and at different protein sites. Here, we take advantage of electrochemical scanning tunneling microscopy (ECSTM) to control the Fermi level and nanometric position of the ECSTM probe in order to study electron transport in individual photosystem I (PSI) complexes. Current-distance measurements at different potentiostatic conditions indicate that PSI supports long-distance transport that is electrochemically gated near the redox potential of P700, with current extending farther under hole injection conditions.

Keywords: Current decay, ECSTM, Electrochemical gate, Electron transfer, Photosynthesis

Agnetta, L., Bermudez, M., Riefolo, F., Matera, C., Claro, E., Messerer, R., Littmann, T., Wolber, G., Holzgrabe, U., Decker, M., (2019). Fluorination of photoswitchable muscarinic agonists tunes receptor pharmacology and photochromic properties Journal of Medicinal Chemistry 62, (6), 3009-3020

Red-shifted azobenzene scaffolds have emerged as useful molecular photoswitches to expand potential applications of photopharmacological tool compounds. As one of them, tetra-ortho-fluoro azobenzene is well compatible for the design of visible-light-responsive systems, providing stable and bidirectional photoconversions and tissue-compatible characteristics. Using the unsubstituted azobenzene core and its tetra-ortho-fluorinated analogue, we have developed a set of uni- and bivalent photoswitchable toolbox derivatives of the highly potent muscarinic acetylcholine receptor agonist iperoxo. We investigated the impact of the substitution pattern on receptor activity and evaluated the different binding modes. Compounds 9b and 15b show excellent photochemical properties and biological activity as fluorination of the azobenzene core alters not only the photochromic behavior but also the pharmacological profile at the muscarinic M1 receptor. These findings demonstrate that incorporation of fluorinated azobenzenes not just may alter photophysical properties but can exhibit a considerably different biological profile that has to be carefully investigated.

Riefolo, F., Matera, C., Garrido-Charles, A., Gomila, A., Sortino, R., Agnetta, L., Claro, E., Masgrau, R., Holzgrabe, U., Batlle, M., Decker, M., Guasch, E., Gorostiza, P., (2019). Optical control of cardiac function with a photoswitchable muscarinic agonist Journal of the American Chemical Society 141, (18), 7628-7636

Light-triggered reversible modulation of physiological functions offers the promise of enabling on-demand spatiotemporally controlled therapeutic interventions. Optogenetics has been successfully implemented in the heart, but significant barriers to its use in the clinic remain, such as the need for genetic transfection. Herein, we present a method to modulate cardiac function with light through a photoswitchable compound and without genetic manipulation. The molecule, named PAI, was designed by introduction of a photoswitch into the molecular structure of an M2 mAChR agonist. In vitro assays revealed that PAI enables light-dependent activation of M2 mAChRs. To validate the method, we show that PAI photoisomers display different cardiac effects in a mammalian animal model, and demonstrate reversible, real-time photocontrol of cardiac function in translucent wildtype tadpoles. PAI can also effectively activate M2 receptors using two-photon excitation with near-infrared light, which overcomes the scattering and low penetration of short-wave-length illumination, and offers new opportunities for intravital imaging and control of cardiac function.

Pittolo, Silvia, Lee, Hyojung, Lladó, Anna, Tosi, Sébastien, Bosch, Miquel, Bardia, Lídia, Gómez-Santacana, Xavier, Llebaria, Amadeu, Soriano, Eduardo, Colombelli, Julien, Poskanzer, Kira E., Perea, Gertrudis, Gorostiza, Pau, (2019). Reversible silencing of endogenous receptors in intact brain tissue using two-photon pharmacology Proceedings of the National Academy of Sciences of the United States of America 116, (27), 13680-13689

The physiological activity of proteins is often studied with loss-of-function genetic approaches, but the corresponding phenotypes develop slowly and can be confounding. Photopharmacology allows direct, fast, and reversible control of endogenous protein activity, with spatiotemporal resolution set by the illumination method. Here, we combine a photoswitchable allosteric modulator (alloswitch) and 2-photon excitation using pulsed near-infrared lasers to reversibly silence metabotropic glutamate 5 (mGlu5) receptor activity in intact brain tissue. Endogenous receptors can be photoactivated in neurons and astrocytes with pharmacological selectivity and with an axial resolution between 5 and 10 µm. Thus, 2-photon pharmacology using alloswitch allows investigating mGlu5-dependent processes in wild-type animals, including synaptic formation and plasticity, and signaling pathways from intracellular organelles.

Keywords: Photopharmacology, Photoactivation, Pharmacological selectivity, Functional silencing, 2-photon pharmacology

Cabré, Gisela, Garrido-Charles, Aida, González-Lafont, Àngels, Moormann, Widukind, Langbehn, Daniel, Egea, David, Lluch, José M., Herges, Rainer, Alibés, Ramon, Busqué, Félix, Gorostiza, Pau, Hernando, Jordi, (2019). Synthetic photoswitchable neurotransmitters based on bridged azobenzenes Organic Letters 21, (10), 3780-3784

Photoswitchable neurotransmitters of ionotropic kainate receptors were synthesized by tethering a glutamate moiety to disubstituted C2-bridged azobenzenes, which were prepared through a novel methodology that allows access to diazocines with higher yields and versatility. Because of the singular properties of these photochromes, photoisomerizable compounds were obtained with larger thermal stability for their inert cis isomer than for their biologically activity trans state. This enabled selective neuronal firing upon irradiation without background activity in the dark.

Gumí-Audenis, B., Giannotti, M. I., (2019). Structural and mechanical characterization of supported model membranes by AFM Biomimetic Lipid Membranes: Fundamentals, Applications, and Commercialization (ed. Kök, Fatma N., Arslan Yildiz, Ahu, Inci, Fatih), Springer International Publishing (Cham, Germany) , 1-27

Several cellular processes, including adhesion, signaling and transcription, endocytosis, and membrane resealing, among others, involve conformational changes such as bending, vesiculation, and tubulation. These mechanisms generally involve membrane separation from the cytoskeleton as well as strong bending, for which the membrane chemical composition and physicochemical properties, often highly localized and dynamic, are key players. The mechanical role of the lipid membrane in force triggered (or sensing) mechanisms in cells is important, and understanding the lipid bilayers’ physical and mechanical properties is essential to comprehend their contribution to the overall membrane. Atomic force microscopy (AFM)-based experimental approaches have been to date very valuable to deepen into these aspects. As a stand-alone, high-resolution imaging technique and force transducer with the possibility to operate in aqueous environment, it defies most other surface instrumentation in ease of use, sensitivity and versatility. In this chapter, we introduce the different AFM-based methods to assess topological and nanomechanical information on model membranes, specifically to supported lipid bilayers (SLBs), including several examples ranging from pure phospholipid homogeneous bilayers to multicomponent and phase-separated SLBs, increasing the bilayer complexity, in the direction of mimicking biological membranes.

Keywords: Atomic force microscopy, Force spectroscopy, Model membranes, Nanomechanics, Supported lipid bilayers

Sebastian, P., Giannotti, M. I., Gómez, E., Feliu, J. M., (2018). Surface sensitive nickel electrodeposition in deep eutectic solvent ACS Applied Energy Materials , 1, (3), 1016-1028

The first steps of nickel electrodeposition in a deep eutectic solvent (DES) are analyzed in detail. Several substrates from glassy carbon to Pt(111) were investigated pointing out the surface sensitivity of the nucleation and growth mechanism. For that, cyclic voltammetry and chronoamperometry, in combination with scanning electron microscopy (SEM), were employed. X-ray diffraction (XRD) and atomic force microscopy (AFM) were used to more deeply analyze the Ni deposition on Pt substrates. In a 0.1 M NiCl2 + DES solution (at 70 °C), the nickel deposition on glassy carbon takes place within the potential limits of the electrode in the blank solution. Although, the electrochemical window of Pt|DES is considerably shorter than on glassy carbon|DES, it was still sufficient for the nickel deposition. On the Pt electrode, the negative potential limit was enlarged while the nickel deposit grew, likely because of the lower catalytic activity of the nickel toward the reduction of the DES. At lower overpotentials, different hydrogenated Ni structures were favored, most likely because of the DES co-reduction on the Pt substrate. Nanometric metallic nickel grains of rounded shape were obtained on any substrate, as evidenced by the FE-SEM. Passivation phenomena, related to the formation of Ni oxide and Ni hydroxylated species, were observed at high applied overpotentials. At low deposited charge, on Pt(111) the AFM measurements showed the formation of rounded nanometric particles of Ni, which rearranged and formed small triangular arrays at sufficiently low applied overpotential. This particle pattern was induced by the (111) orientation and related to surface sensitivity of the nickel deposition in DES. The present work provides deep insights into the Ni electrodeposition mechanism in the selected deep eutectic solvent.

Keywords: AFM, Deep eutectic solvent, Glassy carbon, Nanostructures, Nickel electrodeposition, Platinum electrode, Pt(111), SEM, Surface sensitive

Matera, Carlo, Gomila-Juaneda, Alexandre, Camarero, Núria, Libergoli, Michela, Soler, Concepció, Gorostiza, Pau, (2018). A photoswitchable antimetabolite for targeted photoactivated chemotherapy Journal of the American Chemical Society 140, (46), 15764-15773

The efficacy and tolerability of systemically administered anticancer agents are limited by their off-target effects. Precise spatiotemporal control over their cytotoxic activity would allow improving chemotherapy treatments, and light-regulated drugs are well suited to this purpose. We have developed phototrexate, the first photoswitchable inhibitor of the human dihydrofolate reductase (DHFR), as a photochromic analog of methotrexate, a widely prescribed chemotherapeutic drug to treat cancer and psoriasis. Quantification of the light-regulated DHFR enzymatic activity, cell proliferation, and in vivo effects in zebrafish show that phototrexate behaves as a potent antifolate in its photoactivated cis configuration, and that it is nearly inactive in its dark-relaxed trans form. Thus, phototrexate constitutes a proof-of-concept to design light-regulated cytotoxic small molecules, and a step forward to develop targeted anticancer photochemotherapies with localized efficacy and reduced adverse effects.

Keywords: Photopharmacology, Photodynamic therapy, Antiproliferative, Arthritis, Psoriasis, Nanomedicine

Lagunas, A., Guerra-Castellano, A., Nin-Hill, A., Díaz-Moreno, I., De la Rosa, M. A., Samitier, J., Rovira, C., Gorostiza, P., (2018). Long distance electron transfer through the aqueous solution between redox partner proteins Nature Communications 9, (1), 5157

Despite the importance of electron transfer between redox proteins in photosynthesis and respiration, the inter-protein electron transfer rate between redox partner proteins has never been measured as a function of their separation in aqueous solution. Here, we use electrochemical tunneling spectroscopy to show that the current between two protein partners decays along more than 10 nm in the solution. Molecular dynamics simulations reveal a reduced ionic density and extended electric field in the volume confined between the proteins. The distance-decay factor and the calculated local barrier for electron transfer are regulated by the electrochemical potential applied to the proteins. Redox partners could use electrochemically gated, long distance electron transfer through the solution in order to conciliate high specificity with weak binding, thus keeping high turnover rates in the crowded environment of cells.

Gumi-Audenis, Berta, Costa, Luca, Redondo-Morata, Lorena, Milhiet, Pierre-Emmanuel, Sanz, Fausto, Felici, Roberto, Giannotti, M. I., Carla, Francesco, (2018). In-plane molecular organization of hydrated single lipid bilayers: DPPC:cholesterol Nanoscale 10, 87-92

Understanding the physical properties of the cholesterol-phospholipid systems is essential to get a better knowledge on the function of each membrane constituent. We present a novel, simple and user-friendly setup that allows for straightforward grazing incidence X-rays diffraction characterization of hydrated individual supported lipid bilayers. This configuration minimizes the scattering from the liquid and allows the detection of the extremely weak diffracted signal of the membrane, enabling the differentiation of coexisting domains in DPPC:cholesterol single bilayers.

Gumí-Audenis, Berta, Illa-Tuset, Sílvia, Grimaldi, Natascia, Pasquina-Lemonche, Laia, Ferrer-Tasies, Lidia, Sanz, Fausto, Veciana, Jaume, Ratera, Imma, Faraudo, Jordi, Ventosa, Nora, Giannotti, M. I., (2018). Insights into the structure and nanomechanics of a quatsome membrane by force spectroscopy measurements and molecular simulations Nanoscale 10, (48), 23001-23011

Quatsomes (QS) are unilamellar nanovesicles constituted by quaternary ammonium surfactants and sterols in defined molar ratios. Unlike conventional liposomes, QS are stable upon long storage such as for several years, they show outstanding vesicle-to-vesicle homogeneity regarding size and lamellarity, and they have the structural and physicochemical requirements to be a potential platform for site-specific delivery of hydrophilic and lipophilic molecules. Knowing in detail the structure and mechanical properties of the QS membrane is of great importance for the design of deformable and flexible nanovesicle alternatives, highly pursued in nanomedicine applications such as the transdermal administration route. In this work, we report the first study on the detailed structure of the cholesterol : CTAB QS membrane at the nanoscale, using atomic force microscopy (AFM) and spectroscopy (AFM-FS) in a controlled liquid environment (ionic medium and temperature) to assess the topography of supported QS membranes (SQMs) and to evaluate the local membrane mechanics. We further perform molecular dynamics (MD) simulations to provide an atomistic interpretation of the obtained results. Our results are direct evidence of the bilayer nature of the QS membrane, with characteristics of a fluid-like membrane, compact and homogeneous in composition, and with structural and mechanical properties that depend on the surrounding environment. We show how ions alter the lateral packing, modifying the membrane mechanics. We observe that according to the ionic environment and temperature, different domains may coexist in the QS membranes, ascribed to variations in molecular tilt angles. Our results indicate that QS membrane properties may be easily tuned by altering the lateral interactions with either different environmental ions or counterions.

Gumí-Audenis, Berta, Costa, Luca, Ferrer-Tasies, Lidia, Ratera, Imma, Ventosa, Nora, Sanz, Fausto, Giannotti, M. I., (2018). Pulling lipid tubes from supported bilayers unveils the underlying substrate contribution to the membrane mechanics Nanoscale 10, 14763-14770

Cell processes like endocytosis, membrane resealing, signaling and transcription involve conformational changes which depend on the chemical composition and the physicochemical properties of the lipid membrane. The better understanding of the mechanical role of lipids in cell membrane force-triggered and sensing mechanisms has recently become the focus of attention. Different membrane models and experimental methodologies are commonly explored. While general approaches involve controlled vesicle deformation using micropipettes or optical tweezers, due to the local and dynamic nature of the membrane, high spatial resolution atomic force microscopy (AFM) has been widely used to study the mechanical compression and indentation of supported lipid bilayers (SLBs). However, the substrate contribution remains unkown. Here, we demonstrate how pulling lipid tubes with an AFM out of model SLBs can be used to assess the nanomechanics of SLBs through the evaluation of the tube growing force (Ftube), allowing for very local evaluation with high spatial and force resolution of the lipid membrane tension. We first validate this approach to determine the contribution of different phospholipids, by varying the membrane composition, in both one-component and phase-segregated membranes. Finally, we successfully assess the contribution of the underlying substrate to the membrane mechanics, demonstrating that SLB models may represent an intermediate scenario between a free membrane (blebs) and a cytoskeleton supported membrane.

Bregestovski, Piotr, Maleeva, Galyna, Gorostiza, Pau, (2018). Light-induced regulation of ligand-gated channel activity British Journal of Pharmacology 175, (11), 1892-1902

The control of ligand-gated receptors with light using photochromic compounds has evolved from the first handcrafted examples to accurate, engineered receptors, whose development is supported by rational design, high-resolution protein structures, comparative pharmacology and molecular biology manipulations. Photoswitchable regulators have been designed and characterized for a large number of ligand-gated receptors in the mammalian nervous system, including nicotinic acetylcholine, glutamate and GABA receptors. They provide a well-equipped toolbox to investigate synaptic and neuronal circuits in all-optical experiments. This focused review discusses the design and properties of these photoswitches, their applications and shortcomings and future perspectives in the field.

Crespo-Villanueva, Adrián, Gumí-Audenis, Berta, Sanz, Fausto, Artzner, Franck, Mériadec, Cristelle, Rousseau, Florence, Lopez, Christelle, Giannotti, M. I., Guyomarc'h, Fanny, (2018). Casein interaction with lipid membranes: Are the phase state or charge density of the phospholipids affecting protein adsorption? Biochimica et Biophysica Acta (BBA) - Biomembranes 1860, (12), 2588-2598

Casein micelles are ~200 nm electronegative particles that constitute 80 wt% of the milk proteins. During synthesis in the lactating mammary cells, caseins are thought to interact in the form of ~20 nm assemblies, directly with the biological membranes of the endoplasmic reticulum and/or the Golgi apparatus. However, conditions that drive this interaction are not yet known. Atomic force microscopy imaging and force spectroscopy were used to directly observe the adsorption of casein particles on supported phospholipid bilayers with controlled compositions to vary their phase state and surface charge density, as verified by X-ray diffraction and zetametry. At pH 6.7, the casein particles adsorbed onto bilayer phases with zwitterionic and liquid-disordered phospholipid molecules, but not on phases with anionic or ordered phospholipids. Furthermore, the presence of adsorbed caseins altered the stability of the yet exposed bilayer. Considering their respective compositions and symmetry/asymmetry, these results cast light on the possible interactions of casein assemblies with the organelles’ membranes of the lactating mammary cells.

Keywords: Casein proteins, Phospholipid membrane, Supported lipid bilayer, Atomic force microscopy

Barón-Miranda, J.A., Calzadilla, O., San-Juan-Hernández, S., Diez-Perez, I., Díaz, J., Sanz, Fausto, Chále-Lara, F.F., Espinosa, F.J., Caballero-Briones, F., (2018). Influence of texture on the electrical properties of Al-doped ZnO films prepared by ultrasonic spray pyrolysis Journal of Materials Science: Materials in Electronics 29, (3), 2016-2025

ZnO: Al thin films were deposited by spray pyrolysis onto glass substrates with 0, 0.5, 1.0, 2.0, 5.0 and 10.0% [Al3+/Zn2+] ratios in the deposition solution. Films were characterized by scanning electron microscopy, energy dispersive X-ray spectroscopy, X-ray diffraction, UV–vis transmittance, conductive atomic force microscopy and the sheet resistance was measured. Aluminum contents in the films increases with the Al3+/Zn2+ ratio in the bath while the film deposition rate decreases due to the lower Al3+ surface mobility. Films were crystalline and display a varied morphology that evolves from flakes to mixtures between flakes and pencils and finally between triangles and hexagonal columns with increasing Al contents. Al3+ inclusion at the different sites within the ZnO lattice is proposed to direct the crystal habit and therefore the observed morphology and film texture. The optical band gap evolution and carrier density are related by the Burstein-Moss effect. The results show that film texture influences carrier mobility: increased presence of (112) planes originate a mobility increase while a predominant (110) or (100) texture reduces it. By Current sensing Atomic Force Microscopy (CAFM) the local surface current distribution was related with the observed film texture.

Casanellas, Ignasi, Lagunas, Anna, Tsintzou, Iro, Vida, Yolanda, Collado, Daniel, Pérez-Inestrosa, Ezequiel, Rodríguez-Pereira, Cristina, Magalhaes, Joana, Gorostiza, Pau, Andrades, José A., Becerra, José, Samitier, Josep, (2018). Dendrimer-based uneven nanopatterns to locally control surface adhesiveness: A method to direct chondrogenic differentiation Journal of Visualized Experiments Bioengineering, (131), e56347

Cellular adhesion and differentiation is conditioned by the nanoscale disposition of the extracellular matrix (ECM) components, with local concentrations having a major effect. Here we present a method to obtain large-scale uneven nanopatterns of arginine-glycine-aspartic acid (RGD)-functionalized dendrimers that permit the nanoscale control of local RGD surface density. Nanopatterns are formed by surface adsorption of dendrimers from solutions at different initial concentrations and are characterized by water contact angle (CA), X-ray photoelectron spectroscopy (XPS), and scanning probe microscopy techniques such as scanning tunneling microscopy (STM) and atomic force microscopy (AFM). The local surface density of RGD is measured using AFM images by means of probability contour maps of minimum interparticle distances and then correlated with cell adhesion response and differentiation. The nanopatterning method presented here is a simple procedure that can be scaled up in a straightforward manner to large surface areas. It is thus fully compatible with cell culture protocols and can be applied to other ligands that exert concentration-dependent effects on cells.

Keywords: Bioengineering, Dendrimer, Nanopattern, Arginine-Glycine-Aspartic Acid (RGD), Atomic Force Microscopy (AFM), Cell Adhesion, Mesenchymal Stem Cells (Mscs), Chondrogenesis

Calvé, Pablo, Gorostiza, Pau, (2017). Estrategias optogenéticas y fotofarmacológicas para restablecer la visión Visión , 51, 6-13

La mayoría de los casos de ceguera están causados por defectos en el ojo. Generalmente, estas alteraciones se producen por daños en las vías ópticas que conducen a la retina y son necesarias para el enfoque de las imágenes. A día de hoy, es posible tratar y curar estos impedimentos ópticos. Por ejemplo, la cirugía de cataratas para extraer una lente opaca y reemplazarla con una lente artificial se lleva a cabo rutinariamente en muchas partes del mundo y los trasplantes de córnea con córneas naturales o artificiales comúnmente tienen éxito. Sin embargo, existen casos de ceguera que afectan a un porcentaje considerable de la población y no disponen de tratamiento. La mayor parte de las cegueras incurables son debidas a las enfermedades neurodegenerativas de la retina, que se caracterizan, la mayoría de las veces, por pérdida de las células fotorreceptoras. En estas enfermedades, los fotorreceptores se dañan y mueren en un proceso de apoptosis que eventualmente provoca la ceguera. Sin embargo, las neuronas situadas en las capas internas de la retina permanecen intactas durante un periodo de tiempo prolongado, antes de que la retina sufra procesos de remodelización en las etapas finales de la enfermedad. Entre las enfermedades neurodegenerativas de la retina, la retinosis pigmentaria y la degeneración macular asociada a la edad son las más comunes. De este modo, debido a que las neurodegeneraciones retinianas provocan afectaciones en la visión y pueden inducir ceguera completa en los casos más graves, es necesario buscar y estudiar nuevos tratamientos terapéuticos. Hoy en día, muchos laboratorios de investigación están desarrollando terapias para este tipo de enfermedades, dirigidas a restaurar la función de las células fotorreceptoras en el ojo ciego o bien a sustituir la pérdida de la función fotorreceptora, pretendiendo que las neuronas retinianas restantes sean directamente sensibles a la luz. Estas aproximaciones terapéuticas engloban desde prótesis electrónicas hasta células madre y terapia génica.

Ruiz, Marta P., Aragones, Albert C., Camarero, Nuria, Vilhena, J. G., Ortega, Maria, Zotti, Linda Angela, Perez, Ruben, Cuevas, Juan Carlos, Gorostiza, Pau, Díez-Pérez, Ismael, (2017). Bioengineering a single-protein junction Journal of the American Chemical Society 139, (43), 15337–15346

Bioelectronics moves toward designing nanoscale electronic platforms that allow in vivo determinations. Such devices require interfacing complex biomolecular moieties as the sensing units to an electronic platform for signal transduction. Inevitably, a systematic design goes through a bottom-up understanding of the structurally related electrical signatures of the biomolecular circuit, which will ultimately lead us to tailor its electrical properties. Toward this aim, we show here the first example of bioengineered charge transport in a single-protein electrical contact. The results reveal that a single point-site mutation at the docking hydrophobic patch of a Cu-azurin causes minor structural distortion of the protein blue Cu site and a dramatic change in the charge transport regime of the single-protein contact, which goes from the classical Cu-mediated two-step transport in this system to a direct coherent tunneling. Our extensive spectroscopic studies and molecular-dynamics simulations show that the proteins’ folding structures are preserved in the single-protein junction. The DFT-computed frontier orbital of the relevant protein segments suggests that the Cu center participation in each protein variant accounts for the different observed charge transport behavior. This work is a direct evidence of charge transport control in a protein backbone through external mutagenesis and a unique nanoscale platform to study structurally related biological electron transfer.

Aragonès, A. C., Aravena, D., Valverde-Muñoz, F. J., Real, J. A., Sanz, F., Díez-Pérez, I., Ruiz, E., (2017). Metal-controlled magnetoresistance at room temperature in single-molecule devices Journal of the American Chemical Society 139, (16), 5768-5778

The appropriate choice of the transition metal complex and metal surface electronic structure opens the possibility to control the spin of the charge carriers through the resulting hybrid molecule/metal spinterface in a single-molecule electrical contact at room temperature. The single-molecule conductance of a Au/molecule/Ni junction can be switched by flipping the magnetization direction of the ferromagnetic electrode. The requirements of the molecule include not just the presence of unpaired electrons: the electronic configuration of the metal center has to provide occupied or empty orbitals that strongly interact with the junction metal electrodes and that are close in energy to their Fermi levels for one of the electronic spins only. The key ingredient for the metal surface is to provide an efficient spin texture induced by the spin-orbit coupling in the topological surface states that results in an efficient spin-dependent interaction with the orbitals of the molecule. The strong magnetoresistance effect found in this kind of single-molecule wire opens a new approach for the design of room-temperature nanoscale devices based on spin-polarized currents controlled at molecular level.

Carini, M., Ruiz, M. P., Usabiaga, I., Fernández, J. A., Cocinero, E. J., Melle-Franco, M., Diez-Perez, I., Mateo-Alonso, A., (2017). High conductance values in π-folded molecular junctions Nature Communications 8, 15195

Folding processes play a crucial role in the development of function in biomacromolecules. Recreating this feature on synthetic systems would not only allow understanding and reproducing biological functions but also developing new functions. This has inspired the development of conformationally ordered synthetic oligomers known as foldamers. Herein, a new family of foldamers, consisting of an increasing number of anthracene units that adopt a folded sigmoidal conformation by a combination of intramolecular hydrogen bonds and aromatic interactions, is reported. Such folding process opens up an efficient through-space charge transport channel across the interacting anthracene moieties. In fact, single-molecule conductance measurements carried out on this series of foldamers, using the scanning tunnelling microscopy-based break-junction technique, reveal exceptionally high conductance values in the order of 10-1 G0 and a low length decay constant of 0.02 Ã…-1 that exceed the values observed in molecular junctions that make use of through-space charge transport pathways.

Aragonès, A. C., Darwish, N., Ciampi, S., Sanz, F., Gooding, J. J., Díez-Pérez, I., (2017). Single-molecule electrical contacts on silicon electrodes under ambient conditions Nature Communications 8, 15056

The ultimate goal in molecular electronics is to use individual molecules as the active electronic component of a real-world sturdy device. For this concept to become reality, it will require the field of single-molecule electronics to shift towards the semiconducting platform of the current microelectronics industry. Here, we report silicon-based single-molecule contacts that are mechanically and electrically stable under ambient conditions. The single-molecule contacts are prepared on silicon electrodes using the scanning tunnelling microscopy break-junction approach using a top metallic probe. The molecular wires show remarkable current-voltage reproducibility, as compared to an open silicon/nano-gap/metal junction, with current rectification ratios exceeding 4,000 when a low-doped silicon is used. The extension of the single-molecule junction approach to a silicon substrate contributes to the next level of miniaturization of electronic components and it is anticipated it will pave the way to a new class of robust single-molecule circuits.

Gómez-Santacana, Xavier, Pittolo, Silvia, Rovira, Xavier, Lopez, Marc, Zussy, Charleine, Dalton, James A. R., Faucherre, Adèle, Jopling, Chris, Pin, Jean-Philippe, Ciruela, Francisco, Goudet, Cyril, Giraldo, Jesús, Gorostiza, Pau, Llebaria, Amadeu, (2017). Illuminating phenylazopyridines to photoswitch metabotropic glutamate receptors: From the flask to the animals ACS Central Science , 3, (1), 81-91

Phenylazopyridines are photoisomerizable compounds with high potential to control biological functions with light. We have obtained a series of phenylazopyridines with light dependent activity as negative allosteric modulators (NAM) of metabotropic glutamate receptor subtype 5 (mGlu5). Here we describe the factors needed to achieve an operational molecular photoisomerization and its effective translation into in vitro and in vivo receptor photoswitching, which includes zebrafish larva motility and the regulation of the antinociceptive effects in mice. The combination of light and some specific phenylazopyridine ligands displays atypical pharmacological profiles, including light-dependent receptor overactivation, which can be observed both in vitro and in vivo. Remarkably, the localized administration of light and a photoswitchable compound in the peripheral tissues of rodents or in the brain amygdalae results in an illumination-dependent analgesic effect. The results reveal a robust translation of the phenylazopyridine photoisomerization to a precise photoregulation of biological activity.

López-Martínez, Montserrat, Artés, Juan Manuel, Sarasso, Veronica, Carminati, Marco, Díez-Pérez, Ismael, Sanz, Fausto, Gorostiza, Pau, (2017). Differential electrochemical conductance imaging at the nanoscale Small 13, (36), 1700958

Electron transfer in proteins is essential in crucial biological processes. Although the fundamental aspects of biological electron transfer are well characterized, currently there are no experimental tools to determine the atomic-scale electronic pathways in redox proteins, and thus to fully understand their outstanding efficiency and environmental adaptability. This knowledge is also required to design and optimize biomolecular electronic devices. In order to measure the local conductance of an electrode surface immersed in an electrolyte, this study builds upon the current–potential spectroscopic capacity of electrochemical scanning tunneling microscopy, by adding an alternating current modulation technique. With this setup, spatially resolved, differential electrochemical conductance images under bipotentiostatic control are recorded. Differential electrochemical conductance imaging allows visualizing the reversible oxidation of an iron electrode in borate buffer and individual azurin proteins immobilized on atomically flat gold surfaces. In particular, this method reveals submolecular regions with high conductance within the protein. The direct observation of nanoscale conduction pathways in redox proteins and complexes enables important advances in biochemistry and bionanotechnology.

Keywords: Differential electrochemical conductance, ECSTM, Electron transport pathway, Iron passivation, Redox metalloproteins

Aragonès, Albert C., Medina, Ernesto, Ferrer-Huerta, Miriam, Gimeno, Nuria, Teixidó, Meritxell, Palma, Julio L., Tao, Nongjian, Ugalde, Jesus M., Giralt, Ernest, Díez-Pérez, Ismael, Mujica, Vladimiro, (2017). Measuring the spin-polarization power of a single chiral molecule Small 13, (2), 1602519

The electronic spin filtering capability of a single chiral helical peptide is measured. A ferromagnetic electrode source is employed to inject spin-polarized electrons in an asymmetric single-molecule junction bridging an α-helical peptide sequence of known chirality. The conductance comparison between both isomers allows the direct determination of the polarization power of an individual chiral molecule.

Keywords: Alpha-helical peptides, Chiral transport, Single-molecule wires, Spin-polarization power, Spin-polarized transmission

Santander-Nelli, M., Silva, C. P., Espinoza-Vergara, J., Silva, J. F., Olguín, C. F., Cortés-Arriagada, D., Zagal, J. H., Mendizabal, F., Díez-Pérez, I., Pavez, J., (2017). Tailoring electroactive surfaces by non-template molecular assembly. Towards electrooxidation of L-cysteine Electrochimica Acta , 254, 201-213

We have prepared a nanoelectrode ensemble containing vertically aligned single walled carbon nanotubes (SWCNTs) using a non-template molecular self-assembling strategy. We used a bottom-up construction approach to assemble amino functionalized SWCNTs (af-SWCNTs) in a well-defined architecture. These af-SWCNTs were linked and vertically aligned to pre-formed self-assembled monolayers of 4-MBA. A Cobalt(II) tetracarboxyphthalocyanine (Co(COOH)4Pc) complex was covalently bonded to external portion of af-SWCNTs to complete the final nanoelectrode ensemble. X-ray photoelectron spectroscopy (XPS) and Atomic Force Microcopy (AFM) confirmed the effectiveness of the assembling steps on the gold surface starting from the Au/MBA SAMs. The system Au/4-MBA/af-SWCNTs shows an interface with large ordered array, which exhibits a high activity for the electrooxidation of L-cysteine (L-cys). Theoretical calculations suggest that the incorporation of the af-SWCNTs increased the activity of the assembly to electronic transfer and it was observed that the electrooxidation reaction is energetically favorable.

Keywords: Bottom-up construction, DFT, Modified electrode, Molecular assembly, SAMs, Single walled carbon nanotube

Gómez-Santacana, Xavier, Dalton, James A. R., Rovira, Xavier, Pin, Jean Philippe, Goudet, Cyril, Gorostiza, Pau, Giraldo, Jesús, Llebaria, Amadeu, (2017). Positional isomers of bispyridine benzene derivatives induce efficacy changes on mGlu5 negative allosteric modulation European Journal of Medicinal Chemistry 127, 567-576

Modulation of metabotropic glutamate receptor 5 (mGlu5) with partial allosteric antagonists has received increased interest due to their favourable in vivo activity profiles compared to the unfavourable side-effects of full inverse agonists. Here we report on a series of bispyridine benzene derivatives with a functional molecular switch affecting antagonistic efficacy, shifting from inverse agonism to partial antagonism with only a single change in the substitution pattern of the benzene ring. These efficacy changes are explained through computational docking, revealing two different receptor conformations of different energetic stability and different positional isomer binding preferences.

Keywords: mGlu5, Isomers, Partial efficacy, NAM, Antagonist, Inverse agonist

Terni, Beatrice, Pacciolla, Paolo, Masanas, Helena, Gorostiza, Pau, Llobet, Artur, (2017). Tight temporal coupling between synaptic rewiring of olfactory glomeruli and the emergence of odor-guided behavior in Xenopus tadpoles Journal of Comparative Neurology , 525, (17), 3769-3783

Olfactory sensory neurons (OSNs) are chemoreceptors that establish excitatory synapses within glomeruli of the olfactory bulb. OSNs undergo continuous turnover throughout life, causing the constant replacement of their synaptic contacts. Using Xenopus tadpoles as an experimental system to investigate rewiring of glomerular connectivity, we show that novel OSN synapses can transfer information immediately after formation, mediating olfactory-guided behavior. Tadpoles recover the ability to detect amino acids 4 days after bilateral olfactory nerve transection. Restoration of olfactory-guided behavior depends on the efficient reinsertion of OSNs to the olfactory bulb. Presynaptic terminals of incipient synaptic contacts generate calcium transients in response to odors, triggering long lasting depolarization of olfactory glomeruli. The functionality of reconnected terminals relies on well-defined readily releasable and cytoplasmic vesicle pools. The continuous growth of non-compartmentalized axonal processes provides a vesicle reservoir to nascent release sites, which contrasts to the gradual development of cytoplasmic vesicle pools in conventional excitatory synapses. The immediate availability of fully functional synapses upon formation supports an age-independent contribution of OSNs to the generation of odor maps.

Keywords: Olfactory receptor neurons, Olfactory bulb, Presynaptic terminals, RRID:SCR_013731, RRID:SCR_007164, RRID: AB-887824, RRID: AB-221570, Synaptic vesicles

Obiols-Rabasa, M., Oncins, G., Sanz, F., Tadros, T. F., Solans, C., Levecke, B., Booten, K., Esquena, J., (2017). Investigation of the elastic and adhesion properties of adsorbed hydrophobically modified inulin films on latex particles using Atomic Force Microscopy (AFM) Colloids and Surfaces A: Physicochemical and Engineering Aspects , 524, 185-192

Graft polymer surfactants provide very good colloidal stability because of strong steric repulsions between adsorbed surfactant films. The elastic and adhesion properties of adsorbed hydrophobically modified inulin polymer surfactant (INUTEC NRA) have been directly measured using Atomic Force Microscopy (AFM) measurements. For this purpose, poly(methyl methacrylate/butyl acrylate), P(MMA/BuA), latexes prepared in the presence of the hydrophobically modified inulin (INUTEC NRA) were used. These latexes (diameter 118 nm and polydispersity index of 1.05) showed a very high colloidal stability in water and in the presence of electrolyte (up to 0.2 mol dm−3 KBr). The latexes were deposited on mica, which was silanated to enhance the adhesion of the latex particles to the surface. A silicon nitride tip with approximately 10 nm diameter that also contained an adsorbed layer of surfactant was used in the AFM apparatus. The tip was allowed to approach, contact thereafter the particles with an applied force of 12.5 nN, and finally detach from the film. Both elastic (Young’s) modulus of the film and adhesion force were studied. The results showed that the adsorbed surfactant films are highly elastic and their elastic modulus and adhesion force did not change significantly with the presence of Na2SO4 up to 0.05 mol dm−3. The high elastic contribution to the steric interaction ensures strong repulsion between the latex particles both in water and at high electrolyte concentrations. In addition, the lack of dependence of adhesion force on electrolyte concentration ensures uniform deposition of the latex particles on a flat substrate as for example in coating applications. These results show the advantages of using a graft polymer surfactant for enhancing the stability of particle suspensions, as illustrated in previous investigations.

Keywords: AFM, Colloidal stability, Interaction forces, Steric repulsion

Quadri, M., Matera, C., Silnovi, Pismataro, M. C., Horenstein, N. A., Stokes, C., Papke, R. L., Dallanoce, C., (2017). Identification of α7 nicotinic acetylcholine receptor silent agonists based on the spirocyclic quinuclidine-Δ2-isoxazoline scaffold: Synthesis and electrophysiological evaluation ChemMedChem XXIV National Meeting in Medicinal Chemistry (NMMC 2016) , Wiley Online Library (Perugia, Spain) 12, (16), 1335-1348

Compound 11 (3-(benzyloxy)-1′-methyl-1′-azonia-4H-1′-azaspiro[isoxazole-5,3′-bicyclo[2.2.2]octane] iodide) was selected from a previous set of nicotinic ligands as a suitable model compound for the design of new silent agonists of α7 nicotinic acetylcholine receptors (nAChRs). Silent agonists evoke little or no channel activation but can induce the α7 desensitized Ds state, which is sensitive to a type II positive allosteric modulator, such as PNU-120596. Introduction of meta substituents into the benzyloxy moiety of 11 led to two sets of tertiary amines and quaternary ammonium salts based on the spirocyclic quinuclidinyl-Δ2-isoxazoline scaffold. Electrophysiological assays performed on Xenopus laevis oocytes expressing human α7 nAChRs highlighted four compounds that are endowed with a significant silent-agonism profile. Structure–activity relationships of this group of analogues provided evidence of the crucial role of the positive charge at the quaternary quinuclidine nitrogen atom. Moreover, the present study indicates that meta substituents, in particular halogens, on the benzyloxy substructure direct specific interactions that stabilize a desensitized conformational state of the receptor and induce silent activity

Keywords: Agonists, Cycloaddition, Nitrogen heterocycles, Receptors, Spiro compounds

Bosch, M., Castro, J., Sur, M., Hayashi, Y., (2017). Photomarking relocalization technique for correlated two-photon and electron microcopy imaging of single stimulated synapses Synapse Development - Methods and Protocols (Methods in Molecular Biology) (ed. Poulopoulos , A.), Humana Press (New York, USA) 1538, 185-214

Synapses learn and remember by persistent modifications of their internal structures and composition but, due to their small size, it is difficult to observe these changes at the ultrastructural level in real time. Two-photon fluorescence microscopy (2PM) allows time-course live imaging of individual synapses but lacks ultrastructural resolution. Electron microscopy (EM) allows the ultrastructural imaging of subcellular components but cannot detect fluorescence and lacks temporal resolution. Here, we describe a combination of procedures designed to achieve the correlated imaging of the same individual synapse under both 2PM and EM. This technique permits the selective stimulation and live imaging of a single dendritic spine and the subsequent localization of the same spine in EM ultrathin serial sections. Landmarks created through a photomarking method based on the 2-photon-induced precipitation of an electrodense compound are used to unequivocally localize the stimulated synapse. This technique was developed to image, for the first time, the ultrastructure of the postsynaptic density in which long-term potentiation was selectively induced just seconds or minutes before, but it can be applied for the study of any biological process that requires the precise relocalization of micron-wide structures for their correlated imaging with 2PM and EM.

Keywords: Correlated imaging, DAB, Dendritic spine, Photobranding, Photoetching, Photomarking, Postsynaptic density, Serial-section transmission electron microscopy, Synapse, Time-lapse live two-photon fluorescence microscopy

Rovira, Xavier, Trapero, Ana, Pittolo, Silvia, Zussy, Charleine, Faucherre, Adèle, Jopling, Chris, Giraldo, Jesús, Pin, Jean-Philippe, Gorostiza, Pau, Goudet, Cyril, Llebaria, Amadeu, (2016). OptoGluNAM4.1, a Photoswitchable allosteric antagonist for real-time control of mGlu4 receptor activity Cell Chemical Biology , 23, (8), 929-934

OptoGluNAM4.1, a negative allosteric modulator (NAM) of metabotropic glutamate receptor 4 (mGlu4) contains a reactive group that covalently binds to the receptor and a blue-light-activated, fast-relaxing azobenzene group that allows reversible receptor activity photocontrol in vitro and in vivo. OptoGluNAM4.1 induces light-dependent behavior in zebrafish and reverses the activity of the mGlu4 agonist LSP4-2022 in a mice model of chronic pain, defining a photopharmacological tool to better elucidate the physiological roles of the mGlu4 receptor in the nervous system.

Gumí-Audenis, Berta, Costa, Luca, Carlá, Francesco, Comin, Fabio, Sanz, Fausto, Giannotti, M. I., (2016). Structure and nanomechanics of model membranes by atomic force microscopy and spectroscopy: Insights into the role of cholesterol and sphingolipids Membranes , 6, (4), 58

Biological membranes mediate several biological processes that are directly associated with their physical properties but sometimes difficult to evaluate. Supported lipid bilayers (SLBs) are model systems widely used to characterize the structure of biological membranes. Cholesterol (Chol) plays an essential role in the modulation of membrane physical properties. It directly influences the order and mechanical stability of the lipid bilayers, and it is known to laterally segregate in rafts in the outer leaflet of the membrane together with sphingolipids (SLs). Atomic force microscope (AFM) is a powerful tool as it is capable to sense and apply forces with high accuracy, with distance and force resolution at the nanoscale, and in a controlled environment. AFM-based force spectroscopy (AFM-FS) has become a crucial technique to study the nanomechanical stability of SLBs by controlling the liquid media and the temperature variations. In this contribution, we review recent AFM and AFM-FS studies on the effect of Chol on the morphology and mechanical properties of model SLBs, including complex bilayers containing SLs. We also introduce a promising combination of AFM and X-ray (XR) techniques that allows for in situ characterization of dynamic processes, providing structural, morphological, and nanomechanical information

Keywords: Atomic force microscopy, Force spectroscopy, Lipid membranes, Supported lipid bilayers, Nanomechanics, Cholesterol, Sphingolipids, Membrane structure, XR-AFM combination

Aragonès, Albert C., Haworth, Naomi L., Darwish, Nadim, Ciampi, Simone, Bloomfield, Nathaniel J., Wallace, Gordon G., Diez-Perez, Ismael, Coote, Michelle L., (2016). Electrostatic catalysis of a Diels–Alder reaction Nature 531, (7592), 88-91

It is often thought that the ability to control reaction rates with an applied electrical potential gradient is unique to redox systems. However, recent theoretical studies suggest that oriented electric fields could affect the outcomes of a range of chemical reactions, regardless of whether a redox system is involved1, 2, 3, 4. This possibility arises because many formally covalent species can be stabilized via minor charge-separated resonance contributors. When an applied electric field is aligned in such a way as to electrostatically stabilize one of these minor forms, the degree of resonance increases, resulting in the overall stabilization of the molecule or transition state. This means that it should be possible to manipulate the kinetics and thermodynamics of non-redox processes using an external electric field, as long as the orientation of the approaching reactants with respect to the field stimulus can be controlled. Here, we provide experimental evidence that the formation of carbon–carbon bonds is accelerated by an electric field. We have designed a surface model system to probe the Diels–Alder reaction, and coupled it with a scanning tunnelling microscopy break-junction approach5, 6, 7. This technique, performed at the single-molecule level, is perfectly suited to deliver an electric-field stimulus across approaching reactants. We find a fivefold increase in the frequency of formation of single-molecule junctions, resulting from the reaction that occurs when the electric field is present and aligned so as to favour electron flow from the dienophile to the diene. Our results are qualitatively consistent with those predicted by quantum-chemical calculations in a theoretical model of this system, and herald a new approach to chemical catalysis.

Keywords: Electrocatalysis, Scanning probe microscopy

Zhang, Long, Vogel, Yan Boris, Noble, Benjamin B., Gonçales, Vinicius R., Darwish, Nadim, Brun, Anton Le, Gooding, J. Justin, Wallace, Gordon G., Coote, Michelle L., Ciampi, Simone, (2016). TEMPO monolayers on Si(100) electrodes: Electrostatic effects by the electrolyte and semiconductor space-charge on the electroactivity of a persistent radical Journal of the American Chemical Society 138, (30), 9611-9619

This work demonstrates the effect of electrostatic interactions on the electroactivity of a persistent organic free radical. This was achieved by chemisorption of molecules of 4-azido-2,2,6,6-tetramethyl-1-piperdinyloxy (4-azido-TEMPO) onto monolayer-modified Si(100) electrodes using a two-step chemical procedure to preserve the open-shell state and hence the electroactivity of the nitroxide radical. Kinetic and thermodynamic parameters for the surface electrochemical reaction are investigated experimentally and analyzed with the aid of electrochemical digital simulations and quantum-chemical calculations of a theoretical model of the tethered TEMPO system. Interactions between the electrolyte anions and the TEMPO grafted on highly doped, i.e., metallic, electrodes can be tuned to predictably manipulate the oxidizing power of surface nitroxide/oxoammonium redox couple, hence showing the practical importance of the electrostatics on the electrolyte side of the radical monolayer. Conversely, for monolayers prepared on the poorly doped electrodes, the electrostatic interactions between the tethered TEMPO units and the semiconductor-side, i.e., space-charge, become dominant and result in drastic kinetic changes to the electroactivity of the radical monolayer as well as electrochemical nonidealities that can be explained as an increase in the self-interaction “a” parameter that leads to the Frumkin isotherm.

Aragonès, A. C., Aravena, D., Cerdá, J. I., Acís-Castillo, Z., Li, H., Real, J. A., Sanz, F., Hihath, J., Ruiz, E., Díez-Pérez, I., (2016). Large conductance switching in a single-molecule device through room temperature spin-dependent transport Nano Letters 16, (1), 218-226

Controlling the spin of electrons in nanoscale electronic devices is one of the most promising topics aiming at developing devices with rapid and high density information storage capabilities. The interface magnetism or spinterface resulting from the interaction between a magnetic molecule and a metal surface, or vice versa, has become a key ingredient in creating nanoscale molecular devices with novel functionalities. Here, we present a single-molecule wire that displays large (>10000%) conductance switching by controlling the spin-dependent transport under ambient conditions (room temperature in a liquid cell). The molecular wire is built by trapping individual spin crossover FeII complexes between one Au electrode and one ferromagnetic Ni electrode in an organic liquid medium. Large changes in the single-molecule conductance (>100-fold) are measured when the electrons flow from the Au electrode to either an α-up or a β-down spin-polarized Ni electrode. Our calculations show that the current flowing through such an interface appears to be strongly spin-polarized, thus resulting in the observed switching of the single-molecule wire conductance. The observation of such a high spin-dependent conductance switching in a single-molecule wire opens up a new door for the design and control of spin-polarized transport in nanoscale molecular devices at room temperature.

Keywords: Density functional calculations, Magnetoresistance, Single-molecule junctions, Spin orbit coupling, Spin-crossover complexes, Spinterface, STM break-junction

Izquierdo-Serra, M., Bautista-Barrufet, A., Trapero, A., Garrido-Charles, A., Diaz-Tahoces, A., Camarero, N., Pittolo, S., Valbuena, S., Perez-Jimenez, A., Gay, M., Garcia-Moll, A., Rodriguez-Escrich, C., Lerma, J., De La Villa, P., Fernandez, E., Pericas, M. A., Llebaria, A., Gorostiza, P., (2016). Optical control of endogenous receptors and cellular excitability using targeted covalent photoswitches Nature Communications 7, 12221

Light-regulated drugs allow remotely photoswitching biological activity and enable plausible therapies based on small molecules. However, only freely diffusible photochromic ligands have been shown to work directly in endogenous receptors and methods for covalent attachment depend on genetic manipulation. Here we introduce a chemical strategy to covalently conjugate and photoswitch the activity of endogenous proteins and demonstrate its application to the kainate receptor channel GluK1. The approach is based on photoswitchable ligands containing a short-lived, highly reactive anchoring group that is targeted at the protein of interest by ligand affinity. These targeted covalent photoswitches (TCPs) constitute a new class of light-regulated drugs and act as prosthetic molecules that photocontrol the activity of GluK1-expressing neurons, and restore photoresponses in degenerated retina. The modularity of TCPs enables the application to different ligands and opens the way to new therapeutic opportunities.

Giannotti, M. I., Abasolo, Ibane, Oliva, Mireia, Andrade, Fernanda, García-Aranda, Natalia, Melgarejo, Marta, Pulido, Daniel, Corchero, José Luis, Fernández, Yolanda, Villaverde, Antonio, Royo, Miriam, Garcia-Parajo, Maria F., Sanz, Fausto, Schwartz Jr, Simó, (2016). Highly versatile polyelectrolyte complexes for improving the enzyme replacement therapy of lysosomal storage disorders ACS Applied Materials & Interfaces 8, (39), 25741–25752

Lysosomal storage disorders are currently treated by enzyme replacement therapy (ERT) through the direct administration of the unprotected recombinant protein to the patients. Herein we present an ionically cross-linked polyelectrolyte complex (PEC) composed of trimethyl chitosan (TMC) and α-galactosidase A (GLA), the defective enzyme in Fabry disease, with the capability of directly targeting endothelial cells by incorporating peptide ligands containing the RGD sequence. We assessed the physicochemical properties, cytotoxicity, and hemocompatibility of RGD-targeted and untargeted PECs, the uptake by endothelial cells and the intracellular activity of PECs in cell culture models of Fabry disease. Moreover, we also explored the effect of different freeze-drying procedures in the overall activity of the PECs. Our results indicate that the use of integrin-binding RGD moiety within the PEC increases their uptake and the efficacy of the GLA enzyme, while the freeze-drying allows the activity of the therapeutic protein to remain intact. Overall, these results highlight the potential of TMC-based PECs as a highly versatile and feasible drug delivery system for improving the ERT of lysosomal storage disorders.

Keywords: Enzyme replacement therapy, Fabry disease, Lysosomal delivery, Nanomedicine, Polyelectrolyte complexes, Trimethyl chitosan, α-galactosidase A

Fernanda, Andrade, Pedro, Fonte, Ana, Costa, Cassilda Cunha, Reis, Rute, Nunes, Andreia, Almeida, Domingos, Ferreira, Mireia, Oliva, Bruno, Sarmento, (2016). Pharmacological and toxicological assessment of innovative self-assembled polymeric micelles as powders for insulin pulmonary delivery Nanomedicine 11, (17), 2305-2317

Aim: Explore the use of polymeric micelles in the development of powders intended for pulmonary delivery of biopharmaceuticals, using insulin as a model protein. Materials & methods: Formulations were assessed in vitro for aerosolization properties and in vivo for efficacy and safety using a streptozotocin-induced diabetic rat model. Results: Powders presented good aerosolization properties like fine particle fraction superior to 40% and a mass median aerodynamic diameter inferior of 6 μm. Endotracheally instilled powders have shown a faster onset of action than subcutaneous administration of insulin at a dose of 10 IU/kg, with pharmacological availabilities up to 32.5% of those achieved by subcutaneous route. Additionally, micelles improved the hypoglycemic effect of insulin. Bronchoalveolar lavage screening for toxicity markers (e.g., lactate dehydrogenase, cytokines) revealed no signs of lung inflammation and cytotoxicity 14 days postadministration. Conclusion: Developed powders showed promising safety and efficacy characteristics for the systemic delivery of insulin by pulmonary administration.

Keywords: Fine particle fraction, Inhalation, Insulin, In vivo, Pharmacological availability, Polymeric micelles, Pulmonary toxicity

Noori, M., Aragonès, A. C., Di Palma, G., Darwish, N., Bailey, S. W. D., Al-Galiby, Q., Grace, I., Amabilino, D. B., González-Campo, A., Díez-Pérez, I., Lambert, C. J., (2016). Tuning the electrical conductance of metalloporphyrin supramolecular wires Scientific Reports 6, 37352

In contrast with conventional single-molecule junctions, in which the current flows parallel to the long axis or plane of a molecule, we investigate the transport properties of M(II)-5,15-diphenylporphyrin (M-DPP) single-molecule junctions (M=Co, Ni, Cu, or Zn divalent metal ions), in which the current flows perpendicular to the plane of the porphyrin. Novel STM-based conductance measurements combined with quantum transport calculations demonstrate that current-perpendicular-to-the-plane (CPP) junctions have three-orders-of-magnitude higher electrical conductances than their current-in-plane (CIP) counterparts, ranging from 2.10-2 G0 for Ni-DPP up to 8.10-2 G0 for Zn-DPP. The metal ion in the center of the DPP skeletons is strongly coordinated with the nitrogens of the pyridyl coated electrodes, with a binding energy that is sensitive to the choice of metal ion. We find that the binding energies of Zn-DPP and Co-DPP are significantly higher than those of Ni-DPP and Cu-DPP. Therefore when combined with its higher conductance, we identify Zn-DPP as the favoured candidate for high-conductance CPP single-molecule devices.

A. R. Dalton, J., Lans, I., Rovira, X., Malhaire, F., Gómez-Santacana, X., Pittolo, S., Gorostiza, P., Llebaria, A., Goudet, C., Pin, J-P., Giraldo, J., (2016). Shining light on an mGlu5 photoswitchable NAM: A theoretical perspective Current Neuropharmacology , 14, (5), 441-454

Metabotropic glutamate receptors (mGluRs) are important drug targets because of their involvement in several neurological diseases. Among mGluRs, mGlu5 is a particularly high-profile target because its positive or negative allosteric modulation can potentially treat schizophrenia or anxiety and chronic pain, respectively. Here, we computationally and experimentally probe the functional binding of a novel photoswitchable mGlu5 NAM, termed alloswitch-1, which loses its NAM functionality under violet light. We show alloswitch-1 binds deep in the allosteric pocket in a similar fashion to mavoglurant, the co-crystallized NAM in the mGlu5 transmembrane domain crystal structure. Alloswitch-1, like NAM 2-Methyl-6-(phenylethynyl)pyridine (MPEP), is significantly affected by P655M mutation deep in the allosteric pocket, eradicating its functionality. In MD simulations, we show alloswitch-1 and MPEP stabilize the co-crystallized water molecule located at the bottom of the allosteric site that is seemingly characteristic of the inactive receptor state. Furthermore, both NAMs form H-bonds with S809 on helix 7, which may constitute an important stabilizing interaction for NAM-induced mGlu5 inactivation. Alloswitch-1, through isomerization of its amide group from trans to cis is able to form an additional interaction with N747 on helix 5. This may be an important interaction for amide-containing mGlu5 NAMs, helping to stabilize their binding in a potentially unusual cis-amide state. Simulated conformational switching of alloswitch-1 in silico suggests photoisomerization of its azo group from trans to cis may be possible within the allosteric pocket. However, photoexcited alloswitch-1 binds in an unstable fashion, breaking H-bonds with the protein and destabilizing the co-crystallized water molecule. This suggests photoswitching may have destabilizing effects on mGlu5 binding and functionality.

Keywords: Allosteric modulation, Docking, Metabotropic glutamate receptor, Molecular dynamics, Mutation, Protein structure, Transmembrane domain

Fonte, Pedro, Andrade, Fernanda, Azevedo, Cláudia, Pinto, João, Seabra, Vítor, van de Weert, Marco, Reis, Salette, Sarmento, Bruno, (2016). Effect of the freezing step in the stability and bioactivity of protein-loaded PLGA nanoparticles upon lyophilization Pharmaceutical Research , 33, (11), 2777-2793

The freezing step in lyophilization is the most determinant for the quality of biopharmaceutics. Using insulin as model of therapeutic protein, our aim was to evaluate the freezing effect in the stability and bioactivity of insulin-loaded PLGA nanoparticles. The performance of trehalose, sucrose and sorbitol as cryoprotectants was evaluated.

Martín-Quirós, Andrés, Nevola, Laura, Eckelt, Kay, Madurga, Sergio, Gorostiza, Pau, Giralt, Ernest, (2015). Absence of a stable secondary structure is not a limitation for photoswitchable inhibitors of β-Arrestin/β-Adaptin 2 protein-protein interaction Chemistry & Biology , 22, (1), 31-37

Many protein-protein interactions (PPIs) are mediated by short, often helical, linear peptides. Molecules mimicking these peptides have been used to inhibit their PPIs. Recently, photoswitchable peptides with little secondary structure have been developed as modulators of clathrin-mediated endocytosis. Here we perform a systematic analysis of a series of azobenzene-crosslinked peptides based on a β-arrestin P-long 20-mer peptide (BAP-long) sequence to assess the relevance of secondary structure in their interaction with β-adaptin 2 and to identify the design requirements for photoswitchable inhibitors of PPI (PIPPIs). We observe that flexible structures show a greater inhibitory capacity and enhanced photoswitching ability and that the absence of helical structures in free inhibitor peptide is not a limitation for PIPPI candidates. Therefore, our PIPPIs expand the field of potential inhibitors of PPIs to the wide group of flexible peptides, and we argue against using a stable secondary structure as a sole criterion when designing PIPPI candidates.

Aragonès, Albert C., Darwish, Nadim, Im, JongOne, Lim, Boram, Choi, Jeongae, Koo, Sangho, Díez-Pérez, Ismael, (2015). Fine-tuning of single-molecule conductance by tweaking both electronic structure and conformation of side substituents Chemistry – A European Journal , 21, (21), 7716-7720

Herein, we describe a method to fine-tune the conductivity of single-molecule wires by employing a combination of chemical composition and geometrical modifications of multiple phenyl side groups as conductance modulators embedded along the main axis of the electronic pathway. We have measured the single-molecule conductivity of a novel series of phenyl-substituted carotenoid wires whose conductivity can be tuned with high precision over an order of magnitude range by modulating both the electron-donating character of the phenyl substituent and its dihedral angle. It is demonstrated that the electronic communication between the phenyl side groups and the molecular wire is maximized when the phenyl groups are twisted closer to the plane of the conjugated molecular wire. These findings can be refined to a general technique for precisely tuning the conductivity of molecular wires.

Keywords: Carotenoids, Conductance, Self-assembly, Single-molecule studies, STM break junction

Andrade, F., Neves, J. D., Gener, P., Schwartz, S., Ferreira, D., Oliva, M., Sarmento, B., (2015). Biological assessment of self-assembled polymeric micelles for pulmonary administration of insulin Nanomedicine: Nanotechnology, Biology, and Medicine 11, (7), 1621-1631

Pulmonary delivery of drugs for both local and systemic action has gained new attention over the last decades. In this work, different amphiphilic polymers (Soluplus®, Pluronic® F68, Pluronic® F108 and Pluronic® F127) were used to produce lyophilized formulations for inhalation of insulin. Development of stimuli-responsive, namely glucose-sensitive, formulations was also attempted with the addition of phenylboronic acid (PBA). Despite influencing the in vitro release of insulin from micelles, PBA did not confer glucose-sensitive properties to formulations. Lyophilized powders with aerodynamic diameter (<. 6. μm) compatible with good deposition in the lungs did not present significant in vitro toxicity for respiratory cell lines. Additionally, some formulations, in particular Pluronic® F127-based formulations, enhanced the permeation of insulin through pulmonary epithelial models and underwent minimal internalization by macrophages in vitro. Overall, formulations based on polymeric micelles presenting promising characteristics were developed for the delivery of insulin by inhalation. From the Clinical Editor: The ability to deliver other systemic drugs via inhalation has received renewed interests in the clinical setting. This is especially true for drugs which usually require injections for delivery, like insulin. In this article, the authors investigated their previously developed amphiphilic polymers for inhalation of insulin in an in vitro model. The results should provide basis for future in vivo studies.

Keywords: Cytotoxicity, Inhalation, Permeability, Phagocytosis, Polymeric micelles, Protein delivery

Ponce, I., Aragonès, A. C., Darwish, Nadrim, Pla-Vilanova, P., Oñate, R., Rezende, M. C., Zagal, J. H., Sanz, F., Pavez, J., Díez-Pérez, I., (2015). Building nanoscale molecular wires exploiting electrocatalytic interactions Electrochimica Acta , 179, 611-167

Herein, we present a novel method to design nanoscale molecular wires by exploiting well-established electrocatalytic molecular platforms based on metallophthalocyanine blocks. Metallophthalocyanines exhibit high catalytic activity for a wide variety of electrochemical reactions of practical interests. To this aim, metallophthalocyanine molecules can be attached to an electrode surface via a conjugated mercaptopyridine axial ligand that provides (i) stable chemical binding to the metal surface through the thiol-anchoring group, and (ii) a good electrical communication between the metallophthalocyanine ring and the electrode surface. Our previous work demonstrates that long mercaptopyridinium blocks act as excellent linkers in such electrocatalytic platform, resulting in an optimal electrocatalytic activity of the metallophthalocyanine unit. Here we profit from this optimized electrocatalytic molecular platform to design new molecular wires that connect a metal nanoscale junction in a highly efficient and tunable way. To this aim, we use an STM break-junction approach to control the formation of a nanometric gap between two Au electrodes, both functionalized with mercaptopyridinium (bottom) and mercaptopyridine (top). When metallophthalocyanine is introduced into the functionalized metal nanojunction, stable molecular connections between the two electrodes are formed through axial coordination to the top and bottom pyridine moieties. We show that the highest conductance of the resulting nanoscale molecular wire corresponds to an Fe-phthalocyanine as compare to a Cu-phthalocyanine, which follows the electrocatalytic trend for such molecular systems. These results not only demonstrate a new strategy to design new families of highly conductive and tunable nanoscale molecular wires, but it also brings a new nanoscale electrical platform to help understanding some fundamental mechanistic aspects of molecular electrocatalysis.

Keywords: Single-molecule wires, Metallophthalocyanine, Electrocatalytic molecular platform, Molecular Electronics, STM break-junction

Gascón-Moya, Marta, Pejoan, Arnau, Izquierdo-Serra, M., Pittolo, Silvia, Cabrè, Gisela, Hernando, Jordi, Alibés, Ramon, Gorostiza, Pau, Busque, Felix, (2015). An optimized glutamate receptor photoswitch with sensitized azobenzene isomerization Journal of Organic Chemistry 80, (20), 9915-9925

A new azobenzene-based photoswitch, 2, has been designed to enable optical control of ionotropic glutamate receptors in neurons via sensitized two-photon excitation with NIR light. In order to develop an efficient and versatile synthetic route for this molecule, a modular strategy is described which relies on the use of a new linear fully protected glutamate derivative stable in basic media. The resulting compound undergoes one-photon trans-cis photoisomerization via two different mechanisms: direct excitation of its azoaromatic unit, and irradiation of the pyrene sensitizer, a well known two-photon sensitive chromophore. Moreover, 2 presents large thermal stability of its cis isomer, in contrast to other two-photon responsive switches relying on the intrinsic non-linear optical properties of push-pull substituted azobenzenes. As a result, the molecular system developed herein is a very promising candidate for evoking large photoinduced biological responses during the multiphoton operation of neuronal glutamate receptors with NIR light, which require accumulation of the protein-bound cis state of the switch upon repeated illumination. A new azobenzene-based photoswitch, 2, has been designed to enable optical control of ionotropic glutamate receptors in neurons via sensitized two-photon excitation with NIR light. In order to develop an efficient and versatile synthetic route for this molecule, a modular strategy is described which relies on the use of a new linear fully protected glutamate derivative stable in basic media. The resulting compound undergoes one-photon trans-cis photoisomerization via two different mechanisms: direct excitation of its azoaromatic unit, and irradiation of the pyrene sensitizer, a well known two-photon sensitive chromophore. Moreover, 2 presents large thermal stability of its cis isomer, in contrast to other two-photon responsive switches relying on the intrinsic non-linear optical properties of push-pull substituted azobenzenes. As a result, the molecular system developed herein is a very promising candidate for evoking large photoinduced biological responses during the multiphoton operation of neuronal glutamate receptors with NIR light, which require accumulation of the protein-bound cis state of the switch upon repeated illumination.

Andrade, F., Fonte, P., Oliva, M., Videira, M., Ferreira, D., Sarmento, B., (2015). Solid state formulations composed by amphiphilic polymers for delivery of proteins: Characterization and stability International Journal of Pharmaceutics 486, (1-2), 195-206

Abstract Nanocomposite powders composed by polymeric micelles as vehicles for delivery proteins were developed in this work, using insulin as model protein. Results showed that size and polydispersity of micelles were dependent on the amphiphilic polymer used, being all lower than 300 nm, while all the formulations displayed spherical shape and surface charge close to neutrality. Percentages of association efficiency and loading capacity up to 94.15 ± 3.92 and 8.56 ± 0.36, respectively, were obtained. X-ray photoelectron spectroscopy (XPS) measurements confirmed that insulin was partially present at the hydrophilic shell of the micelles. Lyophilization did not significantly change the physical characteristics of micelles, further providing easily dispersion when in contact to aqueous medium. The native-like conformation of insulin was maintained at high percentages (around 80%) after lyophilization as indicated by Fourier transform infrared spectroscopy (FTIR) and far-UV circular dichroism (CD). Moreover, Raman spectroscopy did not evidenced significant interactions among the formulation components. The formulations shown to be physically stable upon storage up to 6 months both at room-temperature (20 C) and fridge (4 C), with only a slight loss (maximum of 15%) of the secondary structure of the protein. Among the polymers tested, Pluronic® F127 produced the carrier formulations more promising for delivery of proteins.

Keywords: Amphiphilic polymers, Insulin, Lyophilization, Polymeric micelles, Stability

Abadías, Clara, Serés, Carme, Torrent-Burgués, J., (2015). AFM in peak force mode applied to worn siloxane-hydrogel contact lenses Colloids and Surfaces B: Biointerfaces 128, 61-66

The objective of this work is to apply Atomic Force Microscopy in Peak Force mode to obtain topographic characteristics (mean roughness, root-mean-square roughness, skewness and kurtosis) and mechanical characteristics (adhesion, elastic modulus) of Siloxane-Hydrogel Soft Contact Lenses (CLs) of two different materials, Lotrafilcon B of Air Optix (AO) and Asmofilcon A of PremiO (P), after use (worn CLs). Thus, the results obtained with both materials will be compared, as well as the changes produced by the wear at a nanoscopic level. The results show significant changes in the topographic and mechanical characteristics of the CLs, at a nanoscopic level, due to wear. The AO CL show values of the topographic parameters lower than those of the P CL after wear, which correlates with a better comfort qualification given to the former by the wearers. A significant correlation has also been obtained between the adhesion values found after the use of the CLs with tear quality tests, both break-up-time and Schirmer.

Keywords: Adhesion, Atomic force microscopy-peak force mode, Surface topography, Worn siloxane-hydrogel contact lenses, Young modulus

Gumi-Audenis, B., Sanz, F., Giannotti, M. I., (2015). Impact of galactosylceramides on the nanomechanical properties of lipid bilayer models: an AFM-force spectroscopy study Soft Matter 11, (27), 5447-5454

Galactosylceramides (GalCer) are glycosphingolipids bound to a monosaccharide group, responsible for inducing extensive hydrogen bonds that yield their alignment and accumulation in the outer leaflet of the biological membrane together with cholesterol (Chol) in rafts. In this work, the influence of GalCer on the nanomechanical properties of supported lipid bilayers (SLBs) based on DPPC (1,2-dipalmitoyl-sn-glycero-3-phosphocholine) and DLPC (1,2-didodecanoyl-sn-glycero-3-phosphocoline) as model systems was assessed. Phosphatidylcholine (PC):GalCer SLBs were characterized by means of differential scanning calorimetry (DSC) and atomic force microscopy (AFM), in both imaging and force spectroscopy (AFM-FS) modes. Comparing both PC systems, we determined that the behaviour of SLB mixtures is governed by the PC phase-like state at the working temperature. While a phase segregated system is observed for DLPC:GalCer SLBs, GalCer are found to be dissolved in DPPC SLBs for GalCer contents up to 20 mol%. In both systems, the incorporation of GalCer intensifies the nanomechanical properties of SLBs. Interestingly, segregated domains of exceptionally high mechanical stability are formed in DLPC:GalCer SLBs. Finally, the role of 20 mol% Chol in GalCer organization and function in the membranes was assessed. Both PC model systems displayed phase segregation and remarkable nanomechanical stability when GalCer and Chol coexist in SLBs.


Hoyo, J., Guaus, E., Torrent-Burgués, J., Sanz, F., (2015). Biomimetic monolayer films of digalactosyldiacylglycerol incorporating plastoquinone Biochimica et Biophysica Acta - Biomembranes , 1848, (6), 1341-1351

The photosynthesis is the process used by plants and bacteria cells to convert inorganic matter in organic thanks to the light energy. This process consist on several steps, being one of them the electronic transport from the photosystem II to the cytochrome thanks to plastoquinone-9 (PQ). Here we prepare membranes that mimic the characteristics and composition of natural photosynthetic cell membranes and we characterize them in order to obtain the PQ molecules position in the membrane and their electrochemical behaviour. The selected galactolipid is digalactosyldiacylglycerol (DGDG) that represents the 30% of the thylakoid membrane lipid content. The results obtained are worthful for several science fields due to the relevance of galactolipids as anti-algal, anti-viral, anti-tumor and anti-inflammatory agents and the antioxidant and free radical scavenger properties of prenylquinones. Both pure components (DGDG and PQ) and the DGDG:PQ mixtures have been studied using surface pressure-area isotherms. These isotherms give information about the film stability and indicate the thermodynamic behaviour of the mixture and their physical state. The Langmuir-Blodgett (LB) film has been transferred forming a monolayer that mimics the bottom layer of the biological membranes. This monolayer on mica has been topographically characterized using AFM and both the height and the physical state that they present have been obtained. Moreover, these monolayers have been transferred onto ITO that is a hydrophilic substrate with good optical and electrical features, so that, it is suitable for studying the electrochemical behaviour of these systems and it is a good candidate for energy producing devices.

Keywords: Biomimetic membrane, Digalactosyldiacylglycerol, Electron transfer, LangmuirBlodgett film, Modified ITO electrode, Plastoquinone

Pla-Vilanova, P., Aragonès, A. C., Ciampi, S., Sanz, F., Darwish, N., Diez-Perez, I., (2015). The spontaneous formation of single-molecule junctions via terminal alkynes Nanotechnology 26, 381001

Herein, we report the spontaneous formation of single-molecule junctions via terminal alkyne contact groups. Self-assembled monolayers that form spontaneously from diluted solutions of 1, 4-diethynylbenzene (DEB) were used to build single-molecule contacts and assessed using the scanning tunneling microscopy-break junction technique (STM-BJ). The STM-BJ technique in both its dynamic and static approaches was used to characterize the lifetime (stability) and the conductivity of a single-DEB wire. It is demonstrated that single-molecule junctions form spontaneously with terminal alkynes and require no electrochemical control or chemical deprotonation. The alkyne anchoring group was compared against typical contact groups exploited in single-molecule studies, i.e. amine (benzenediamine) and thiol (benzendithiol) contact groups. The alkyne contact showed a conductance magnitude comparable to that observed with amine and thiol groups. The lifetime of the junctions formed from alkynes were only slightly less than that of thiols and greater than that observed for amines. These findings are important as (a) they extend the repertoire of chemical contacts used in single-molecule measurements to 1-alkynes, which are synthetically accessible and stable and (b) alkynes have a remarkable affinity toward silicon surfaces, hence opening the door for the study of single-molecule transport on a semiconducting electronic platform.

Keywords: Ferrocene, Molecular electronics, Single-molecule electronics, Single-molecule junctions, Singlemolecule contacts, STM-break junction, Terminal alkyne

Hoyo, J., Guaus, E., Torrent-Burgués, J., Sanz, F., (2015). Electrochemistry of LB films of mixed MGDG: UQ on ITO Bioelectrochemistry , 104, 26-34

The electrochemical behaviour of biomimetic monolayers of monogalactosyldiacylglycerol (MGDG) incorporating ubiquinone-10 (UQ) has been investigated. MGDG is the principal component in the thylakoid membrane and UQ seems a good substitute for plastoquinone-9, involved in photosynthesis chain. The monolayers have been performed using the Langmuir and Langmuir-Blodgett (LB) techniques and the redox behaviour of the LB films, transferred at several surface pressures on a glass covered with indium-tin oxide (ITO), has been characterized by cyclic voltammetry. The cyclic voltammograms show that UQ molecules present two redox processes (I and II) at high UQ content and high surface pressures, and only one redox process (I) at low UQ content and low surface pressures. The apparent rate constants calculated for processes I and II indicate a different kinetic control for the reduction and the oxidation of UQ/UQH2 redox couple, being kRapp(I)=2.2·10-5s-1, kRapp(II)=5.1·10-14 kOapp(I)=3.3·10-3s-1 and kOapp(II)=6.1·10-6s-1, respectively. The correlation of the redox response with the physical states of the LB films allows determining the positions of the UQ molecules in the biomimetic monolayer, which change with the surface pressure and the UQ content. These positions are known as diving and swimming.

Keywords: Cyclic voltammetry, Electron transfer, Langmuir-Blodgett film, Modified ITO electrode, Monogalactosyldiacylglycerol, Ubiquinone

Hoyo, J., Guaus, E., Torrent-Burgués, J., Sanz, F., (2015). Biomimetic monolayer films of monogalactosyldiacylglycerol incorporating plastoquinone Journal of Physical Chemistry B , 119, (20), 6170-6178

Photosynthetic organisms use light to convert the inorganic matter in organic one. Photosynthetic process consists on several steps, and one of them involves plastoquinone (PQ) that acts as electron and proton shuttle between photosystem II and cytochrome. We prepared membranes that mimic the characteristics and composition of natural photosynthetic membranes and we characterized them using several techniques in order to obtain both the PQ molecules disposition in the membrane and their electrochemical behavior. The selected lipid was monogalactosyldiacylglycerol (MGDG) that represents the 50% of the lipid content of the thylakoid membrane. Both MGDG and PQ, and the MGDG:PQ mixtures have been studied using surface pressure-area isotherms and the presence of PQ alters the physical state and compactness of the MGDG matrix. Langmuir-Blodgett (LB) films have been obtained by transferring a monolayer that mimics half of the bilayer of a biological membrane. The AFM topographical characterization of the monolayers on mica indicates the presence of differentiated domains, corresponding to different physical states linked to the influence of the PQ content. Moreover, the electrochemical behavior of the monolayers has been studied when transferred on ITO, observing one main electrochemical process that is due to the diving position of PQ molecules in the lipid matrix.

Giannotti, M. I., Cabeza de Vaca, Israel, Artés, Juan Manuel, Sanz, Fausto, Guallar, Victor, Gorostiza, Pau, (2015). Direct measurement of the nanomechanical stability of a redox protein active site and its dependence upon metal binding Journal of Physical Chemistry B , 119, (36), 12050-12058

The structural basis of the low reorganization energy of cupredoxins has long been debated. These proteins reconcile a conformationally heterogeneous and exposed metal-chelating site with the highly rigid copper center required for efficient electron transfer. Here we combine single-molecule mechanical unfolding experiments with statistical analysis and computer simulations to show that the metal-binding region of apo-azurin is mechanically flexible and that high mechanical stability is imparted by copper binding. The unfolding pathway of the metal site depends on the pulling residue and suggests that partial unfolding of the metal binding site could be facilitated by the physical interaction with certain regions of the redox protein. The structural basis of the low reorganization energy of cupredoxins has long been debated. These proteins reconcile a conformationally heterogeneous and exposed metal-chelating site with the highly rigid copper center required for efficient electron transfer. Here we combine single-molecule mechanical unfolding experiments with statistical analysis and computer simulations to show that the metal-binding region of apo-azurin is mechanically flexible and that high mechanical stability is imparted by copper binding. The unfolding pathway of the metal site depends on the pulling residue and suggests that partial unfolding of the metal binding site could be facilitated by the physical interaction with certain regions of the redox protein.

Gumí-Audenis, B., Carlà, F., Vitorino, M. V., Panzarella, A., Porcar, L., Boilot, M., Guerber, S., Bernard, P., Rodrigues, M. S., Sanz, F., Giannotti, M. I., Costa, L., (2015). Custom AFM for X-ray beamlines: in situ biological investigations under physiological conditions Journal of Synchrotron Radiation , 22, 1364-1371

A fast atomic force microscope (AFM) has been developed that can be installed as a sample holder for grazing-incidence X-ray experiments at solid/gas or solid/liquid interfaces. It allows a wide range of possible investigations, including soft and biological samples under physiological conditions (hydrated specimens). The structural information obtained using the X-rays is combined with the data gathered with the AFM (morphology and mechanical properties), providing a unique characterization of the specimen and its dynamics in situ during an experiment. In this work, lipid monolayers and bilayers in air or liquid environment have been investigated by means of AFM, both with imaging and force spectroscopy, and X-ray reflectivity. In addition, this combination allows the radiation damage induced by the beam on the sample to be studied, as has been observed on DOPC and DPPC supported lipid bilayers under physiological conditions.

Keywords: In situ atomic force microscopy, Grazing-incidence scattering and reflectivity, Radiation damage, Model lipid membranes

El-Boubbou, Kheireddine, Al-Kaysi, Rabih O., Al-Muhanna, Muhanna K., Bahhari, Hassan M., Al-Romaeh, Abdulaziz I., Darwish, Nadim, Al-Saad, Khaled O., Al-Suwaidan, Salem D., (2015). Ultra-small fatty acid-stabilized magnetite nanocolloids synthesized by in situ hydrolytic precipitation Journal of Nanomaterials , 2015, 620672

Simple, fast, large-scale, and cost-effective preparation of uniform controlled magnetic nanoparticles remains a major hurdle on the way towards magnetically targeted applications at realistic technical conditions. Herein, we present a unique one-pot approach that relies on simple basic hydrolytic in situ coprecipitation of inexpensive metal salts (Fe2+ and Fe3+) compartmentalized by stabilizing fatty acids and aided by the presence of alkylamines. The synthesis was performed at relatively low temperatures (-80ºC) without the use of high-boiling point solvents and elevated temperatures. This method allowed for the production of ultra-small, colloidal, and hydrophobically stabilized magnetite metal oxide nanoparticles readily dispersed in organic solvents. The results reveal that the obtained magnetite nanoparticles exhibit narrow size distributions, good monodispersities, high saturation magnetizations, and excellent colloidal stabilities. When the [fatty acid] : [Fe] ratio was varied, control over nanoparticle diameters within the range of 2–10 nm was achieved. The amount of fatty acid and alkylamine used during the reaction proved critical in governing morphology, dispersity, uniformity, and colloidal stability. Upon exchange with water-soluble polymers, the ultra-small sized particles become biologically relevant, with great promise for theranostic applications as imaging and magnetically targeted delivery vehicles.

Arvizu-Rodríguez, L. E., Palacios-Padrós, A., Chalé-Lara, F., Fernández-Muñoz, J. L., Díez-Pérez, I., Sanz, F., Espinosa-Faller, F. J., Sandoval, J., Caballero-Briones, F., (2015). Phase and surface modification by electrochemical post deposition treatments in ultrasonic-assisted CuInSe2/Cu electrodeposited films Chalcogenide Letters , 12, (10), 537-545

CuInSe2 films were prepared onto Cu-cladded substrates by ultrasonic-assisted electrodeposition using different bath compositions and a fixed deposition potential of E=-1500 mV vs Ag/AgCl. In situ electrochemical treatments named selenization and electrocrystallization, in a Se4+ electrolyte were applied to modify the morphology, film structure and the phase composition. Films were characterized by scanning electron microscopy, X-ray diffraction, Raman spectroscopy and photocurrent response. A Cu2-xSe layer develops as the electrode is introduced into the electrolyte. The presence of Cu-In, In-Se, Cu-Se, cubic, hexagonal and tetragonal CuInSe2 phases as well as elemental In and Se was observed. After selenization, partial phase dissolution and Se deposition is observed and after the electrocrystallization treatment the secondary phases such as Cu-Se, Cu-In, In and Se reduce substantially and the grain sizes increase, as well as the photocurrent response. Phase diagrams are constructed for each set of films and reaction mechanisms are proposed to explain the phase evolution.

Keywords: CuInSe2, Electrodeposition, In situ electrochemical treatments, Phase composition, Surface modification

Brazil, R., (2015). Drugs on demand Chemistry & Industry , 79, (2), 36-39

Artés, Juan Manuel, Hihath, J., Diéz-Pérez, I., (2015). Biomolecular electronics Molecular Electronics: An Experimental and Theoretical Approach (ed. Baldea, I.), Pan Stanford Publishing (Singapore, Singapore) 325, 281-324

Molecular electronics, an emerging research field at the border of physics, chemistry, and material sciences, attracted a great interest in the last decade. To achieve the ultimate goal of designing molecular electronic devices with the desired functionality and experimental manipulation at the single-molecule level, theoretical understanding of electron transport at the nanoscale is an important prerequisite. This book, a multi-authored volume comprising reviews written by leading scientists, discusses recent advances in the field. It emphasizes the need for studies beyond the low-bias regime, a fact on which the scientific community became aware in the last years. To make the book useful for scientists of various disciplines interested in “learning by doing,” each chapter is written in a science/tutorial hybrid style, with its own introduction presenting fundamental concepts and frameworks. The content reflects the strong transdisciplinary efforts needed for substantial progress.

Eckelt, Kay, Masanas, Helena, Llobet, Artur, Gorostiza, P., (2014). Automated high-throughput measurement of body movements and cardiac activity of Xenopus tropicalis tadpoles Journal of Biological Methods , 1, (2), e9

Xenopus tadpoles are an emerging model for developmental, genetic and behavioral studies. A small size, optical accessibility of most of their organs, together with a close genetic and structural relationship to humans make them a convenient experimental model. However, there is only a limited toolset available to measure behavior and organ function of these animals at medium or high-throughput. Herein, we describe an imaging-based platform to quantify body and autonomic movements of Xenopus tropicalis tadpoles of advanced developmental stages. Animals alternate periods of quiescence and locomotor movements and display buccal pumping for oxygen uptake from water and rhythmic cardiac movements. We imaged up to 24 animals in parallel and automatically tracked and quantified their movements by using image analysis software. Animal trajectories, moved distances, activity time, buccal pumping rates and heart beat rates were calculated and used to characterize the effects of test compounds. We evaluated the effects of propranolol and atropine, observing a dose-dependent bradycardia and tachycardia, respectively. This imaging and analysis platform is a simple, cost-effective high-throughput in vivo assay system for genetic, toxicological or pharmacological characterizations.

Keywords: Xenopus tropicalis, Animal behavior, Cardiac imaging, Motion analysis, Animal tracking, Hhigh-throughput in vivo assay

Palacios-Padrós, Anna, Altomare, Marco, Lee, Kiyoung, Díez-Pérez, Ismael, Sanz, Fausto, Schmuki, Patrik, (2014). Controlled thermal annealing tunes the photoelectrochemical properties of nanochanneled tin-oxide structures ChemElectroChem , 1, (7), 1133-1137

We study the effect of thermal annealing conditions (up to 400 °C) and atmospheres (air, Arand O2) on a newly developed nanochannel tin‐oxide structure. The nanochanneled structures were prepared by self‐organized anodization of metallic tin. Thermal annealing conditions have a strong impact on the crystallinity and content of Sn2+ defects present in the structure, and thus have a strong influence on the photoresponse characteristics of the films. Photocurrent measurements show that films annealed at 200 °C in Ar atmosphere exhibit a band gap as low as 2.4 eV and a photoresponse in the visible range. This effect is ascribed to a large content of Sn2+ defects in the structure and the improved crystallinity of the films annealed at this temperature. On the contrary, the Sn2+ content is decreased when annealing at 400 °C under aerobic conditions, which correlates with a shift in the film band gap to 3.2 eV, closer to the reported value for pure SnO2 (3.6 eV).

Aragonès, Albert C., Darwish, Nadim, Saletra, Wojciech J., Pérez-García, Ll., Sanz, Fausto, Puigmartí-Luis, Josep, Amabilino, David B., Díez-Pérez, Ismael, (2014). Highly conductive single-molecule wires with controlled orientation by coordination of metalloporphyrins Nano Letters 14, (8), 4751-4756

Porphyrin-based molecular wires are promising candidates for nanoelectronic and photovoltaic devices due to the porphyrin chemical stability and unique optoelectronic properties. An important aim toward exploiting single porphyrin molecules in nanoscale devices is to possess the ability to control the electrical pathways across them. Herein, we demonstrate a method to build single-molecule wires with metalloporphyrins via their central metal ion by chemically modifying both an STM tip and surface electrodes with pyridin-4-yl-methanethiol, a molecule that has strong affinity for coordination with the metal ion of the porphyrin. The new flat configuration resulted in single-molecule junctions of exceedingly high lifetime and of conductance 3 orders of magnitude larger than that obtained previously for similar porphyrin molecules but wired from either end of the porphyrin ring. This work presents a new concept of building highly efficient single-molecule electrical contacts by exploiting metal coordination chemistry. Porphyrin-based molecular wires are promising candidates for nanoelectronic and photovoltaic devices due to the porphyrin chemical stability and unique optoelectronic properties. An important aim toward exploiting single porphyrin molecules in nanoscale devices is to possess the ability to control the electrical pathways across them. Herein, we demonstrate a method to build single-molecule wires with metalloporphyrins via their central metal ion by chemically modifying both an STM tip and surface electrodes with pyridin-4-yl-methanethiol, a molecule that has strong affinity for coordination with the metal ion of the porphyrin. The new flat configuration resulted in single-molecule junctions of exceedingly high lifetime and of conductance 3 orders of magnitude larger than that obtained previously for similar porphyrin molecules but wired from either end of the porphyrin ring. This work presents a new concept of building highly efficient single-molecule electrical contacts by exploiting metal coordination chemistry.

Darwish, Nadim., Aragonès, A. C., Darwish, T., Ciampi, S., Díez-Pérez, I., (2014). Multi-responsive photo- and chemo-electrical single-molecule switches Nano Letters 14, (12), 7064-7070

Incorporating molecular switches as the active components in nanoscale electrical devices represents a current challenge in molecular electronics. It demands key requirements that need to be simultaneously addressed including fast responses to external stimuli and stable attachment of the molecules to the electrodes while mimicking the operation of conventional electronic components. Here, we report a single-molecule switching device that responds electrically to optical and chemical stimuli. A light pointer or a chemical signal can rapidly and reversibly induce the isomerization of bifunctional spiropyran derivatives in the bulk reservoir and, consequently, switch the electrical conductivity of the single-molecule device between a low and a high level. The spiropyran derivatives employed are chemically functionalized such that they can respond in fast but practical time scales. The unique multistimuli response and the synthetic versatility to control the switching schemes of this single-molecule device suggest spiropyran derivatives as key candidates for molecular circuitry.

Keywords: Molecular Electronics, Multi-Responsive Molecular Switches, Photo- and Chemo-Switches Spiropyran, Single-Molecule Conductance, STM Break-Junction, Electronic equipment, Isomerization, Molecular electronics, Photochromism, Electrical conductivity, Electronic component, Molecular switches, Single-molecule conductances, Single-molecule devices, Spiropyran derivatives, Spiropyrans, STM Break-Junction, Molecules

Pittolo, Silvia, Gómez-Santacana, Xavier, Eckelt, Kay, Rovira, Xavier, Dalton, James, Goudet, Cyril, Pin, Jean-Philippe, Llobet, Artur, Giraldo, Jesús, Llebaria, Amadeu, Gorostiza, Pau, (2014). An allosteric modulator to control endogenous G protein-coupled receptors with light Nature Chemical Biology , 10, (10), 813-815

Controlling drug activity with light offers the possibility of enhancing pharmacological selectivity with spatial and temporal regulation, thus enabling highly localized therapeutic effects and precise dosing patterns. Here we report on the development and characterization of what is to our knowledge the first photoswitchable allosteric modulator of a G protein–coupled receptor. Alloswitch-1 is selective for the metabotropic glutamate receptor mGlu5 and enables the optical control of endogenous mGlu5 receptors.

Izquierdo-Serra, M., Gascón-Moya, Marta, Hirtz, Jan J., Pittolo, Silvia, Poskanzer, Kira E., Ferrer, Eric, Alibés, Ramon, Busque, Felix, Yuste, Rafael, Hernando, Jordi, Gorostiza, Pau, (2014). Two-photon neuronal and astrocytic stimulation of azobenzene-based photoswitches Journal of the American Chemical Society American Chemical Society 136, (24), 8693-8701

Synthetic photochromic compounds can be designed to control a variety of proteins and their biochemical functions in living cells, but the high spatiotemporal precision and tissue penetration of two-photon stimulation has never been investigated in these molecules. Here we demonstrate two-photon excitation of azobenzene-based protein switches, and versatile strategies to enhance their photochemical responses. This enables new applications to control the activation of neurons and astrocytes with cellular and subcellular resolution.

Bautista-Barrufet, A., López-Gallego, F., Rojas-Cervellera, V., Rovira, C., Pericàs, M. A., Guisán, J. M., Gorostiza, P., (2014). Optical control of enzyme enantioselectivity in solid phase ACS Catalysis , 4, (3), 1004-1009

A lipase was immobilized on transparent agarose microspheres and genetically engineered to specifically anchor photochromic molecules into its catalytic site. Several combinations of azobenzene and spiropyran groups were conjugated to cysteines introduced at different positions near the active center. Light modulated the catalytic properties of the resulting solid bioconjugates, and such modulation depended on both the nature of the photochromic compound and the anchoring position. Covalent anchoring of azobenzene derivatives to the residue 295 of the lipase 2 from Bacillus thermocathenolatus triggered lipase preference for the S isomer under UV light, whereas visible light promoted preference for the R isomer. Molecular dynamics simulations indicate that conjugating photochromic compounds into the catalytic cavity allows manipulating the steric hindrance and binding energy of the substrates, leading to an enantioselective molecular fit in certain cases. Using this approach, we report for the first time the control of enzyme properties using light in the solid phase. A lipase was immobilized on transparent agarose microspheres and genetically engineered to specifically anchor photochromic molecules into its catalytic site. Several combinations of azobenzene and spiropyran groups were conjugated to cysteines introduced at different positions near the active center. Light modulated the catalytic properties of the resulting solid bioconjugates, and such modulation depended on both the nature of the photochromic compound and the anchoring position. Covalent anchoring of azobenzene derivatives to the residue 295 of the lipase 2 from Bacillus thermocathenolatus triggered lipase preference for the S isomer under UV light, whereas visible light promoted preference for the R isomer. Molecular dynamics simulations indicate that conjugating photochromic compounds into the catalytic cavity allows manipulating the steric hindrance and binding energy of the substrates, leading to an enantioselective molecular fit in certain cases. Using this approach, we report for the first time the control of enzyme properties using light in the solid phase.

Artés, Juan M., López-Martínez, Montserrat, Díez-Pérez, Ismael, Sanz, Fausto, Gorostiza, Pau, (2014). Conductance switching in single wired redox proteins Small 10, (13), 2537-2541

Switching events in the current flowing through individual redox proteins, (azurin) spontaneously wired between two electrodes, are studied using an electrochemical scanning tunneling microscope (ECSTM). These switching events in the current–time trace are characterized using conductance histograms, and reflect the intrinsic redox thermodynamic dispersion in the azurin population. This conductance switching may pose limitations to miniaturizing redox protein-based devices.

Keywords: Bioelectronics, Protein transistors, Molecular junctions, Switches, STM

Palacios-Padrós, A., Altomare, M., Tighineanu, A., Kirchgeorg, R., Shrestha, N. K., Díez-Pérez, I., Caballero-Briones, F., Sanz, F., Schmuki, P., (2014). Growth of ordered anodic SnO2 nanochannel layers and their use for H2 gas sensing Journal of Materials Chemistry A , 2, (4), 915-920

In the current work, we present a new self-organizing anodization approach of metallic Sn layers to obtain vertically aligned tin oxide nanochannel structures. For this, we use a sulphide-containing electrolyte and a set of optimized anodizing parameters. The resulting high aspect ratio nanochannel morphologies can be converted into crystalline SnO2 by high temperature annealing and show highly promising H2 sensing properties. We show that these anodic layers can operate at relatively low temperatures (∼80 °C), detecting concentrations as low as 9 ppm, and with extremely fast response and recovery times. This excellent gas-sensing performance is ascribed to the advanced structure, characterized by a crack-free, straight and top-open nanochannel geometry.

Lagunas, A., Garcia, A., Artés, J. M., Vida, Y., Collado, D., Pérez-Inestrosa, E., Gorostiza, P., Claros, S., Andrades, J. A., Samitier, J., (2014). Large-scale dendrimer-based uneven nanopatterns for the study of local arginine-glycine-aspartic acid (RGD) density effects on cell adhesion Nano Research , 7, (3), 399-409

Cell adhesion processes are governed by the nanoscale arrangement of the extracellular matrix (ECM), being more affected by local rather than global concentrations of cell adhesive ligands. In many cell-based studies, grafting of dendrimers on surfaces has shown the benefits of the local increase in concentration provided by the dendritic configuration, although the lack of any reported surface characterization has limited any direct correlation between dendrimer disposition and cell response. In order to establish a proper correlation, some control over dendrimer surface deposition is desirable. Here, dendrimer nanopatterning has been employed to address arginine-glycine-aspartic acid (RGD) density effects on cell adhesion. Nanopatterned surfaces were fully characterized by atomic force microscopy (AFM), scanning tunneling microscopy (STM) and X-ray photoelectron spectroscopy (XPS), showing that tunable distributions of cell adhesive ligands on the surface are obtained as a function of the initial dendrimer bulk concentration. Cell experiments showed a clear correlation with dendrimer surface layout: Substrates presenting regions of high local ligand density resulted in a higher percentage of adhered cells and a higher degree of maturation of focal adhesions (FAs). Therefore, dendrimer nanopatterning is presented as a suitable and controlled approach to address the effect of local ligand density on cell response. Moreover, due to the easy modification of dendrimer peripheral groups, dendrimer nanopatterning can be further extended to other ECM ligands having density effects on cells.

Keywords: Arginine-glycine-aspartic acid, Atomic force microscopy, Cell adhesion, Dendrimer, Focal adhesions, Scanning tunneling microscopy

Pérez-Madrigal, M. M., Giannotti, M. I., Del Valle, L. J., Franco, L., Armelin, E., Puiggalí, J., Sanz, F., Alemán, C., (2014). Thermoplastic polyurethane:polythiophene nanomembranes for biomedical and biotechnological applications ACS Applied Materials & Interfaces 6, (12), 9719-9732

Nanomembranes have been prepared by spin-coating mixtures of a polythiophene (P3TMA) derivative and thermoplastic polyurethane (TPU) using 20:80, 40:60, and 60:40 TPU:P3TMA weight ratios. After structural, topographical, electrochemical, and thermal characterization, properties typically related with biomedical applications have been investigated: swelling, resistance to both hydrolytic and enzymatic degradation, biocompatibility, and adsorption of type I collagen, which is an extra cellular matrix protein that binds fibronectin favoring cell adhesion processes. The swelling ability and the hydrolytic and enzymatic degradability of TPU:P3TMA membranes increases with the concentration of P3TMA. Moreover, the degradation of the blends is considerably promoted by the presence of enzymes in the hydrolytic medium, TPU:P3TMA blends behaving as biodegradable materials. On the other hand, TPU:P3TMA nanomembranes behave as bioactive platforms stimulating cell adhesion and, especially, cell viability. Type I collagen adsorption largely depends on the substrate employed to support the nanomembrane, whereas it is practically independent of the chemical nature of the polymeric material used to fabricate the nanomembrane. However, detailed microscopy study of the morphology and topography of adsorbed collagen evidence the formation of different organizations, which range from fibrils to pseudoregular honeycomb networks depending on the composition of the nanomembrane that is in contact with the protein. Scaffolds made of electroactive TPU:P3TMA nanomembranes are potential candidates for tissue engineering biomedical applications.

Keywords: Bioactive platform, Biodegradable blend, Collaged adsorption, Scaffolds, Tissue engineering, Ultrathin films

Pérez-Madrigal, M. M., Giannotti, M. I., Armelin, E., Sanz, F., Alemán, C., (2014). Electronic, electric and electrochemical properties of bioactive nanomembranes made of polythiophene:thermoplastic polyurethane Polymer Chemistry 5, (4), 1248-1257

The electronic, electric and electrochemical response of nanomembranes prepared by using spin-coating mixtures of a semiconducting polythiophene derivative (P3TMA) and thermoplastic polyurethane (TPU) has been exhaustively examined by UV-vis spectroscopy, conductive AFM, current/voltage measurements and cyclic voltammetry. TPU:P3TMA nanomembranes were reported to be good substrates for applications related to tissue engineering, acting as a cellular matrix for cell adhesion and proliferation. Both TPU:P3TMA and P3TMA nanomembranes show semiconductor behavior with very similar band gap energy (2.35 and 2.32 eV, respectively), which has been attributed to the influence of the fabrication process on the π-conjugation length and packing interactions of P3TMA chains. This behavior is in opposition to the observations in THF solution, which indicates that the band gap energy of P3TMA is clearly lower than that of the mixture, independently of the concentration. The current and conductivity values determined for the nanomembranes, which range from 0.43 to 1.85 pA and from 2.23 × 10-5 to 5.19 × 10-6 S cm-1, respectively, evidence inhomogeneity in the P3TMA-rich domains. This has been associated with the irregular distribution of the doped chains and the presence of insulating TPU chains. The voltammetric response of TPU:P3TMA and P3TMA nanomembranes is similar in terms of ability to store charge and electrochemical stability. Overall results indicate that TPU:P3TMA nanomembranes are potential candidates for the fabrication of bioactive substrates able to promote cell regeneration through electrical or electrochemical stimulation.

Bahamonde, María Isabel, Taura, Jaume, Paoletta, Silvia, Gakh, Andrei Alexandrovich, Chakraborty, Saibal, Hernando, Jordi, Fernández-Dueñas, Víctor, Jacobson, Kenneth A., Gorostiza, Pau, Ciruela, Francisco, (2014). Photomodulation of G protein-coupled adenosine receptors by a novel light-switchable ligand Bioconjugate Chemistry , American Chemical Society 25, (10), 1847-1854

The adenosinergic system operates through G protein-coupled adenosine receptors, which have become promising therapeutic targets for a wide range of pathological conditions. However, the ubiquity of adenosine receptors and the eventual lack of selectivity of adenosine-based drugs have frequently diminished their therapeutic potential. Accordingly, here we aimed to develop a new generation of light-switchable adenosine receptor ligands that change their intrinsic activity upon irradiation, thus allowing the spatiotemporal control of receptor functioning (i.e. receptor activation/inactivation dependent on location and timing). Therefore, we synthesized an orthosteric, photoisomerizable and non-selective adenosine receptor agonist, nucleoside derivative MRS5543 containing an aryl diazo linkage on the N6 substituent, which in the dark (relaxed isomer) behaved as a full adenosine A3 receptor (A3R) and partial adenosine A2A receptor (A2AR) agonist. Conversely, upon photoisomerization with blue light (460 nm), it remained a full A3R agonist but became an A2AR antagonist. Interestingly, molecular modeling suggested that structural differences encountered within the third extracellular loop of each receptor could modulate the intrinsic, receptor subtype-dependent, activity. Overall, the development of adenosine receptor ligands with photoswitchable activity expands the pharmacological toolbox in support of research and possibly opens new pharmacotherapeutic opportunities. The adenosinergic system operates through G protein-coupled adenosine receptors, which have become promising therapeutic targets for a wide range of pathological conditions. However, the ubiquity of adenosine receptors and the eventual lack of selectivity of adenosine-based drugs have frequently diminished their therapeutic potential. Accordingly, here we aimed to develop a new generation of light-switchable adenosine receptor ligands that change their intrinsic activity upon irradiation, thus allowing the spatiotemporal control of receptor functioning (i.e. receptor activation/inactivation dependent on location and timing). Therefore, we synthesized an orthosteric, photoisomerizable and non-selective adenosine receptor agonist, nucleoside derivative MRS5543 containing an aryl diazo linkage on the N6 substituent, which in the dark (relaxed isomer) behaved as a full adenosine A3 receptor (A3R) and partial adenosine A2A receptor (A2AR) agonist. Conversely, upon photoisomerization with blue light (460 nm), it remained a full A3R agonist but became an A2AR antagonist. Interestingly, molecular modeling suggested that structural differences encountered within the third extracellular loop of each receptor could modulate the intrinsic, receptor subtype-dependent, activity. Overall, the development of adenosine receptor ligands with photoswitchable activity expands the pharmacological toolbox in support of research and possibly opens new pharmacotherapeutic opportunities.

Artés, J. M., López-Martínez, M., Díez-Pérez, I., Sanz, F., Gorostiza, P., (2014). Nanoscale charge transfer in redox proteins and DNA: Towards biomolecular electronics Electrochimica Acta , 140, 83-95

Understanding how charges move through and between biomolecules is a fundamental question that constitutes the basis for many biological processes. On the other hand, it has potential applications in the design of sensors based on biomolecules and single molecule devices. In this review we introduce the study of the electron transfer (ET) process in biomolecules, providing an overview of the fundamental theory behind it and the different experimental approaches. The ET in proteins is introduced by reviewing a complete electronic characterization of a redox protein (azurin) using electrochemical scanning tunnelling microscopy (ECSTM). The ET process in DNA is overviewed and results from different experimental approaches are discussed. Finally, future directions in the study of the ET process in biomolecules are introduced as well as examples of possible technological applications.

Keywords: Bioelectrochemistry, Biomolecular electronics, Charge transfer, Nanobiodevice, Single-molecule junction

Gomez-Santacana, X., Rovira, X., Dalton, J. A., Goudet, C., Pin, J. P., Gorostiza, P., Giraldo, J., Llebaria, A., (2014). A double effect molecular switch leads to a novel potent negative allosteric modulator of metabotropic glutamate receptor 5 MedChemComm , 5, (10), 1548-1554

Compounds that modulate the function of G-protein-coupled receptors (GPCRs) by binding to their allosteric sites are of potential interest for the treatment of multiple CNS and non-CNS disorders. Allosteric ligands can act either as positive (PAM), negative (NAM), or silent (SAM) receptor modulators and have numerous advantages over classic orthosteric compounds, including improved GPCR-subtype selectivity; the capacity to adapt to physiological conditions; and better safety profiles. Despite these benefits, allosteric modulators are difficult to design and optimize and are often prone to "molecular switching": a structural phenomenon by which very subtle chemical variations in the ligand result in unexpected changes in selectivity profiles or pharmacology, changing PAMs to NAMs or vice versa. Here, we report the discovery of a nanomolar and subtype selective NAM of metabotropic glutamate receptor 5 (mGlu5) through a targeted "double effect molecular switch" of a potent mGlu4 PAM, and suggests a promising approach towards the discovery of novel mGluR allosteric modulators.

Torrent-Burgués, J., Cea, P., Giner, I., Guaus, E., (2014). Characterization of Langmuir and Langmuir-Blodgett films of an octasubstituted zinc phthalocyanine Thin Solid Films , 556, 485-494

In this work we report the fabrication of Langmuir and Langmuir-Blodgett (LB) films of a substituted ZnPc (octakis(oxyoctyl)phthalocyanine of zinc), and their characterization by means of several techniques. These characterization techniques include surface pressure (π-A) and surface potential (ΔV-A) isotherms as well as UV-vis Reflection spectroscopy and Brewster Angle Microscopy (BAM) for the films at the air-water interface together with UV-vis absorption and IR spectroscopies and Atomic Force Microscopy (AFM) for the LB films. The π-A and ΔV-A isotherms and BAM images indicate a phase transition at a surface pressure of ca. 9 mN/m and a multilayer formation at surface pressures around 19-20 mN/m; at a surface pressure around 27 mN/m a disordered collapse of the film occurs. In addition, AFM images of LB films at π = 10 mN/m and π = 20 mN/m show a monomolecular and a multilayered film, respectively. The comparison of the UV-vis spectrum of ZnPc in solution, the reflection spectra of the Langmuir films and UV-vis spectra of LB films reveals a significant reduction in the Q band intensity for the films, indicative of an organization of ZnPc in the Langmuir and LB films versus the random distribution in solution. The UV-vis Reflection spectra are also consistent with multilayer formation at surface pressures around 19-20 mN/m. The relative intensities of the IR spectrum bands change from the KBr pellet to the LB film which is also attributable to orientation effects in the film. Cyclic voltammetric experiments of LB films incorporating the ZnPc derivative show peaks that can be correlated with redox processes occurring in the phthalocyanine ring. A small but significant influence of the surface pressure and the number of deposited layers in the electrochemical behaviour is observed. The electrochemical response of cast films exhibits some differences with respect to that of LB films which have been attributed to their different molecular organizations.

Keywords: Atomic Force Microscopy, Electrochemistry, Langmuir-Blodgett, Multilayers, Optical spectroscopy techniques, Zinc phthalocyanine, Atomic force microscopy, Electrochemistry, Interfaces (materials), Isotherms, Multilayers, Nitrogen compounds, Optical multilayers, Organic polymers, Zinc compounds, Brewster angle microscopy, Characterization techniques, Electrochemical behaviour, Langmuir and langmuir-blodgett films, Langmuir-blodgett, Optical spectroscopy techniques, UV-Vis Reflection Spectroscopy, Zinc phthalocyanines, Langmuir Blodgett films

Redondo-Morata, L., Giannotti, M. I., Sanz, F., (2014). Structural impact of cations on lipid bilayer models: Nanomechanical properties by AFM-force spectroscopy Molecular Membrane Biology , 31, (1), 17-28

Atomic Force Microscopy (AFM) has become an invaluable tool for studying the micro-and nanoworlds. As a stand-alone, high-resolution imaging technique and force transducer, it defies most other surface instrumentation in ease of use, sensitivity and versatility. The main strength of AFM relies on the possibility to operate in an aqueous environment on a wide variety of biological samples, from single molecules-DNA or proteins-to macromolecular assemblies like biological membranes. Understanding the effect of mechanical stress on membranes is of primary importance in biophysics, since cells are known to perform their function under a complex combination of forces. In the later years, AFM-based Force-Spectroscopy (AFM-FS) has provided a new vista on membrane mechanics in a confined area within the nanometer realm, where most of the specific molecular interactions take place. Lipid membranes are electrostatically charged entities that physiologically coexist with electrolyte solutions. Thus, specific interactions with ions are a matter of considerable interest. The distribution of ions in the solution and their interaction with the membranes are factors that substantially modify the structure and dynamics of the cell membranes. Furthermore, signaling processes are modified by the membrane capability of retaining ions. Supported Lipid Bilayers (SLBs) are a versatile tool to investigate phospholipid membranes mimicking biological surfaces. In the present contribution, we review selected experiments on the mechanical stability of SLBs as models of lipid membranes by means of AFM-FS, with special focus on the effect of cations and ionic strength in the overall nanomechanical stability.

Keywords: Atomic force microscopy, Cations, Force spectroscopy, Lipid bilayer, Mechanical stability

Eyleen, Araya, Marcelo J, Kogan, Aleix G, Guell, Carlos A, Escobar, Fausto, Sanz, (2014). Sensing immobilized molecules of streptavidin on a silicon surface by MALDI-TOF mass espectrometry and fluorescence microscopy Journal of the Chilean Chemical Society , 59, (2), 2458-2463

A hydrogen-terminated Si (111) surface was modified to form an aminoterminated monolayer for immobilization of streptavidin. Cleavage of an N-(ω-undecylenyl)-phthalimide covered surface using hidrazine yields an amino group-modified surface, which serves as a substrate for the attachment of biotin and subsequently streptavidin. We used surface analytical techniques to characterize the surface and to control the course of functionalization before the immobilization of streptavidin. To confirm the presence of the streptavidin Texas red on the surface two powerful techniques available in a standard biochemical laboratory are used, Fluorescence Microscopy and MALDI-TOF that allow us to detect and determine the immobilized streptavidin. This work provides an avenue for the development of devices in which the exquisite binding specificity of biomolecular recognition is directly coupled to a biosensor. In addition, we have demonstrated that MALDI-TOF and fluorescence microscopy are useful techniques for the characterization of silicon functionalized surfaces.

Bautista-Barrufet, Antoni, Izquierdo-Serra, M., Gorostiza, Pau, (2014). Photoswitchable Ion Channels and Receptors Advances in Atom and Single Molecule Machines Novel Approaches for Single Molecule Activation and Detection (ed. Benfenati, Fabio, Di Fabrizio, Enzo, Torre, Vincent), Springer Berlin Heidelberg , 169-188

The development of photochromic and photoswitchable ligands for ion channels and receptors has made important contributions to optopharmacology and optogenetic pharmacology. These compounds provide new tools to study ion channel proteins and to understand their function and pathological implications. Here, we describe the design, operation, and applications of the available photoswitches, with special emphasis on ligand- and voltage-gated channels.

Redondo-Morata, L., Giannotti, M. I., Sanz, F., (2013). AFM-based force-clamp indentation: Force-clamp monitors the lipid bilayer failure kinetics Imaging & Microscopy , 15, (4), 25-27

The lipid bilayer rupture was here explored by means of AFM-based force clamp. For the first time to our knowledge, this technique has been used to evaluate how lipid membranes respond when compressed under an external constant force in the range of nN. We were able to directly quantify the kinetics of the membrane rupture event and the associated energy barriers, in distinction to the classic studies performed at constant velocity.

Hines, T., Díez-Pérez, I., Nakamura, H., Shimazaki, T., Asai, Y., Tao, N., (2013). Controlling formation of single-molecule junctions by electrochemical reduction of diazonium terminal groups Journal of the American Chemical Society 135, (9), 3319-3322

We report controlling the formation of single-molecule junctions by means of electrochemically reducing two axialdiazonium terminal groups on a molecule, thereby producing direct Au-C covalent bonds in situ between the molecule and gold electrodes. We report a yield enhancement in molecular junction formation as the electrochemical potential of both junction electrodes approach the reduction potential of the diazonium terminal groups. Step length analysis shows that the molecular junction is significantly more stable, and can be pulled over a longer distance than a comparable junction created with amine anchoring bonds. The stability of the junction is explained by the calculated lower binding energy associated with the direct Au-C bond compared with the Au-N bond.

Nevola, L., Martín-Quirós, A., Eckelt, K., Camarero, N., Tosi, S., Llobet, A., Giralt, E., Gorostiza, P., (2013). Light-regulated stapled peptides to inhibit protein-protein interactions involved in clathrin-mediated endocytosis Angewandte Chemie - International Edition , 52, (30), 7704-7708

Control of membrane traffic: Photoswitchable inhibitors of protein-protein interactions were applied to photoregulate clathrin-mediated endocytosis (CME) in living cells. Traffic light (TL) peptides acting as "stop" and "go" signals for membrane traffic can be used to dissect the role of CME in receptor internalization and in cell growth, division, and differentiation.

Keywords: Clathrin-mediated endocytosis, Optopharmacology, Peptides, Photoswitches, Protein-protein interactions

Punet, X., Mauchauffé, R., Giannotti, M. I., Rodríguez-Cabello, J. C., Sanz, F., Engel, E., Mateos-Timoneda, M. A., Planell, J. A., (2013). Enhanced cell-material interactions through the biofunctionalization of polymeric surfaces with engineered peptides Biomacromolecules , 14, (8), 2690-2702

Research on surface modification of polymeric materials to guide the cellular activity in biomaterials designed for tissue engineering applications has mostly focused on the use of natural extracellular matrix (ECM) proteins and short peptides, such as RGD. However, the use of engineered proteins can gather the advantages of these strategies and avoid the main drawbacks. In this study, recombinant engineered proteins called elastin-like recombinamers (ELRs) have been used to functionalize poly(lactic) acid (PLA) model surfaces. The structure of the ELRs has been designed to include the integrin ligand RGDS and the cross-linking module VPGKG. Surface functionalization has been characterized and optimized by means of ELISA and atomic force microscopy (AFM). The results suggest that ELR functionalization creates a nonfouling canvas able to restrict unspecific adsorption of proteins. Moreover, AFM analysis reveals the conformation and disposition of ELRs on the surface. Biological performance of PLA surfaces functionalized with ELRs has been studied and compared with the use of short peptides. Cell response has been assessed for different functionalization conditions in the presence and absence of the bovine serum albumin (BSA) protein, which could interfere with the surface?cell interaction by adsorbing on the interface. Studies have shown that ELRs are able to elicit higher rates of cell attachment, stronger cell anchorages and faster levels of proliferation than peptides. This work has demonstrated that the use of engineered proteins is a more efficient strategy to guide the cellular activity than the use of short peptides, because they not only allow for better cell attachment and proliferation, but also can provide more complex properties such as the creation of nonfouling surfaces. Research on surface modification of polymeric materials to guide the cellular activity in biomaterials designed for tissue engineering applications has mostly focused on the use of natural extracellular matrix (ECM) proteins and short peptides, such as RGD. However, the use of engineered proteins can gather the advantages of these strategies and avoid the main drawbacks. In this study, recombinant engineered proteins called elastin-like recombinamers (ELRs) have been used to functionalize poly(lactic) acid (PLA) model surfaces. The structure of the ELRs has been designed to include the integrin ligand RGDS and the cross-linking module VPGKG. Surface functionalization has been characterized and optimized by means of ELISA and atomic force microscopy (AFM). The results suggest that ELR functionalization creates a nonfouling canvas able to restrict unspecific adsorption of proteins. Moreover, AFM analysis reveals the conformation and disposition of ELRs on the surface. Biological performance of PLA surfaces functionalized with ELRs has been studied and compared with the use of short peptides. Cell response has been assessed for different functionalization conditions in the presence and absence of the bovine serum albumin (BSA) protein, which could interfere with the surface?cell interaction by adsorbing on the interface. Studies have shown that ELRs are able to elicit higher rates of cell attachment, stronger cell anchorages and faster levels of proliferation than peptides. This work has demonstrated that the use of engineered proteins is a more efficient strategy to guide the cellular activity than the use of short peptides, because they not only allow for better cell attachment and proliferation, but also can provide more complex properties such as the creation of nonfouling surfaces.

Perez Madrigal, M. M., Giannotti, M. I., Oncins, G., Franco, L., Armelin, E., Puiggali, J., Sanz, F., del Valle, L. J., Aleman, C., (2013). Bioactive nanomembranes of semiconductor polythiophene and thermoplastic polyurethane: thermal, nanostructural and nanomechanical properties Polymer Chemistry 4, (3), 568-583

Free-standing and supported nanomembranes have been prepared by spin-coating mixtures of a semiconducting polythiophene (P3TMA) derivative and thermoplastic polyurethane (TPU). Thermal studies of TPU:P3TMA blends with 60 : 40, 50 : 50, 40 : 60 and 20 : 80 weight ratios indicate a partial miscibility of the two components. Analysis of the glass transition temperatures allowed us to identify the highest miscibility for the blend with a 40 : 60 weight ratio, this composition being used to prepare both self-standing and supported nanomembranes. The thickness of ultra-thin films made with the 40 : 60 blend ranged from 11 to 93 nm, while the average roughness was 16.3 +/- 0.8 nm. In these films the P3TMA-rich phase forms granules, which are dispersed throughout the rest of the film. Quantitative nanomechanical mapping has been used to determine the Young's modulus value by applying the Derjanguin-Muller-Toporov (DMT) contact mechanics model and the adhesion force of ultra-thin films. The modulus depends on the thickness of the films, values determined for the thicker (80-140 nm)/thinner (10-40 nm) regions of TPU, P3TMA and blend samples being 25/35 MPa, 3.5/12 GPa and 0.9/1.7 GPa, respectively. In contrast the adhesion force is homogeneous through the whole surface of the TPU and P3TMA films (average values: 7.2 and 5.0 nN, respectively), whereas for the blend it depends on the phase distribution. Thus, the adhesion force is higher for the TPU-rich domains than for the P3TMA-rich domains. Finally, the utility of the nanomembranes for tissue engineering applications has been proved by cellular proliferation assays. Results show that the blend is more active as a cellular matrix than each of the two individual polymers.

Lima, Lia M. C., Giannotti, M. I., Redondo-Morata, L., Vale, M. L. C., Marques, E. F., Sanz, F., (2013). Morphological and nanomechanical behavior of supported lipid bilayers on addition of cationic surfactants Langmuir 29, (30), 9352-9361

The addition of surfactants to lipid bilayers is important for the modulation of lipid bilayer properties (e.g., in protein reconstitution and development of nonviral gene delivery vehicles) and to provide insight on the properties of natural biomembranes. In this work, the thermal behavior, organization, and nanomechanical stability of model cationic lipid?surfactant bilayers have been investigated. Two different cationic surfactants, hexadecyltrimethylammonium bromide (CTAB) and a novel derivative of the amino acid serine (Ser16TFAc), have been added (up to 50 mol %) to both liposomes and supported lipid bilayers (SLBs) composed by the zwitterionic phospholipid DPPC. The thermal phase behavior of mixed liposomes has been probed by differential scanning calorimetry (DSC), and the morphology and nanomechanical properties of mixed SLBs by atomic force microscopy-based force spectroscopy (AFM-FS). Although DSC thermograms show different results for the two mixed liposomes, when both are deposited on mica substrates similar trends on the morphology and the mechanical response of the lipid?surfactant bilayers are observed. DSC thermograms indicate microdomain formation in both systems, but while CTAB decreases the degree of organization on the liposome bilayer, Ser16TFAc ultimately induces the opposite effect. Regarding the AFM-FS studies, they show that microphase segregation occurs for these systems and that the effect is dependent on the surfactant content. In both SLB systems, different microdomains characterized by their height and breakthrough force Fb are formed. The molecular organization and composition is critically discussed in the light of our experimental results and literature data on similar lipid?surfactant systems. The addition of surfactants to lipid bilayers is important for the modulation of lipid bilayer properties (e.g., in protein reconstitution and development of nonviral gene delivery vehicles) and to provide insight on the properties of natural biomembranes. In this work, the thermal behavior, organization, and nanomechanical stability of model cationic lipid?surfactant bilayers have been investigated. Two different cationic surfactants, hexadecyltrimethylammonium bromide (CTAB) and a novel derivative of the amino acid serine (Ser16TFAc), have been added (up to 50 mol %) to both liposomes and supported lipid bilayers (SLBs) composed by the zwitterionic phospholipid DPPC. The thermal phase behavior of mixed liposomes has been probed by differential scanning calorimetry (DSC), and the morphology and nanomechanical properties of mixed SLBs by atomic force microscopy-based force spectroscopy (AFM-FS). Although DSC thermograms show different results for the two mixed liposomes, when both are deposited on mica substrates similar trends on the morphology and the mechanical response of the lipid?surfactant bilayers are observed. DSC thermograms indicate microdomain formation in both systems, but while CTAB decreases the degree of organization on the liposome bilayer, Ser16TFAc ultimately induces the opposite effect. Regarding the AFM-FS studies, they show that microphase segregation occurs for these systems and that the effect is dependent on the surfactant content. In both SLB systems, different microdomains characterized by their height and breakthrough force Fb are formed. The molecular organization and composition is critically discussed in the light of our experimental results and literature data on similar lipid?surfactant systems.

Aragonès, A. C., Palacios-Padrós, A., Caballero-Briones, F., Sanz, F., (2013). Study and improvement of aluminium doped ZnO thin films: Limits and advantages Electrochimica Acta , 109, 117-124

ZnO:Al films were deposited at 70°C at a fixed -1.1V potential onto ITO substrates from a 0.01M Zn(NO3)2+x Al(NO3)3·9H2O electrochemical bath, with Al3+ concentrations between 0 and 2mM. Electrodeposition conditions were optimized to remove bubbles, increase grain size homogeneity and ensure adherence. Films were characterized by field emission scanning electron microscopy, X-ray diffraction, X-ray photoelectron spectroscopy, UV-vis transmittance, electrochemical impedance spectroscopy and photocurrent spectroscopy. Films were crystalline with the wurtzite structure and present a morphology made of hexagonal nano-pillars. It was found that Al incorporation increases gradually up to ~11at% for samples prepared within the concentration range 0.0-0.3mM Al3+ in the bath. For higher Al3+ contents (>0.4mM) an amorphous Al2O3-like compound develops on top of the films. In the grown films with Al contents up to 11at%, changes in the optical band gap from 2.88eV to 3.45eV and in the carrier densities from 1019 to 1020cm-3 were observed. The blue shift in the band gap energy was attributed to the Burstein-Moss effect. Changes in the photocurrent response and the electronic disorder were also discussed in the light of Al doping. Optical transmittances up to 60% at 550nm were obtained, thus making these films suitable as transparent and conductive oxide films.

Palacios-Padrós, A., Caballero-Briones, F., Díez-Pérez, I., Sanz, F., (2013). Tin passivation in alkaline media: Formation of SnO microcrystals as hydroxyl etching product Electrochimica Acta , 111, 837-845

The mechanism of the electrochemical passivation on Tin electrodes in 0.1 M NaOH is studied at low scan rates in a wide potential range. To this aim, tin oxide layers were grown on a polycrystalline tin surface under potentiostatic conditions in both the active and passive electrochemical potential ranges, and characterized by field emission scanning electron microscopy (FESEM), X-ray diffraction (XRD), Raman spectroscopy and electrochemical impedance spectroscopy (EIS). The results show that the first anodic process in the active region corresponds to the formation of a SnO·nH2O prepassive layer that is removed upon increasing the applied potential due to surface etching occurring at the metal/oxide interface. During the etching process, Sn 2+ ions supersaturate at the electrode vicinity thus forming a SnO crystalline phase on top of the electrode surface in the presence of the alkaline medium. At higher anodic potentials, near the passive plateau, the etching process ceases and the current drops due to the formation of a n-type Sn(IV)-based oxide at the metal/SnO interface that provides an efficient electronic passivation of the electrode.

Izquierdo-Serra, Mercè, Trauner, Dirk, Llobet, Artur, Gorostiza, Pau, (2013). Optical control of calcium-regulated exocytosis Biochimica et Biophysica Acta (BBA) - General Subjects , 1830, (3), 2853-2860

Background Neurons signal to each other and to non-neuronal cells as those in muscle or glands, by means of the secretion of neurotransmitters at chemical synapses. In order to dissect the molecular mechanisms of neurotransmission, new methods for directly and reversibly triggering neurosecretion at the presynaptic terminal are necessary. Here we exploit the calcium permeability of the light-gated channel LiGluR in order to reversibly manipulate cytosolic calcium concentration, thus controlling calcium-regulated exocytosis. Methods Bovine chromaffin cells expressing LiGluR were stimulated with light. Exocytic events were detected by amperometry or by whole-cell patch-clamp to quantify membrane capacitance and calcium influx. Results Amperometry reveals that optical stimulation consistently triggers exocytosis in chromaffin cells. Secretion of catecholamines can be adjusted between zero and several Hz by changing the wavelength of illumination. Differences in secretion efficacy are found between the activation of LiGluR and native voltage-gated calcium channels (VGCCs). Our results show that the distance between sites of calcium influx and vesicles ready to be released is longer when calcium influx is triggered by LiGluR instead of native VGCCs. Conclusion and general significance LiGluR activation directly and reversibly increases the intracellular calcium concentration. Light-gated calcium influx allows for the first time to control calcium-regulated exocytosis without the need of applying depolarizing solutions or voltage clamping in chromaffin cells. Thus, LiGluR is a useful tool to study the secretory mechanisms and their spatiotemporal patterns in neurotransmission, and opens a window to study other calcium-dependent processes such as muscular contraction or cell migration.

Keywords: Optical control, Calcium, Exocytosis, Light-gated glutamate receptor (LiGluR), Neurotransmission, Optogenetics

Hoyo, J., Guaus, E., Oncins, G., Torrent-Burgués, J., Sanz, F., (2013). Incorporation of Ubiquinone in supported lipid bilayers on ITO Journal of Physical Chemistry B , 117, (25), 7498-7506

Ubiquinone (UQ) is one of the main electron and proton shuttle molecules in biological systems, and dipalmitoylphosphatidylcholine (DPPC) is one of the most used model lipids. Supported planar bilayers (SPBs) are extensively accepted as biological model membranes. In this study, SPBs have been deposited on ITO, which is a semiconductor with good electrical and optical features. Specifically, topographic atomic force microscopy (AFM) images and force curves have been performed on SPBs with several DPPC:UQ ratios to study the location and the interaction of UQ in the SPB. Additionally, cyclic voltammetry has been used to understand the electrochemical behavior of DPPC:UQ SPBs. Obtained results show that, in our case, UQ is placed in two main different positions in SPBs. First, between the DPPC hydrophobic chains, fact that originates a decrease in the breakthrough force of the bilayer, and the second between the two leaflets that form the SPBs. This second position occurs when increasing the UQ content, fact that eventually forms UQ aggregates at high concentrations. The formation of aggregates produces an expansion of the SPB average height and a bimodal distribution of the breakthrough force. The voltammetric response of UQ depends on its position on the bilayer.

Keywords: Bimodal distribution, Biological models, Dipalmitoyl phosphatidylcholine, Electrochemical behaviors, Hydrophobic chains, Supported lipid bilayers, Supported planar bilayers, Voltammetric response

Raster, P., Späth, A., Bultakova, S., Gorostiza, P., König, B., Bregestovski, P., (2013). New GABA amides activating GABAA-receptors Beilstein Journal of Organic Chemistry , 9, 406-410

We have prepared a series of new and some literature-reported GABA-amides and determined their effect on the activation of GABA A-receptors expressed in CHO cells. Special attention was paid to the purification of the target compounds to remove even traces of GABA contaminations, which may arise from deprotection steps in the synthesis. GABA-amides were previously reported to be partial, full or superagonists. In our hands these compounds were not able to activate GABAA-receptor channels in whole-cell patch-clamp recordings. New GABA-amides, however, gave moderate activation responses with a clear structure-activity relationship suggesting some of these compounds as promising molecular tools for the functional analysis of GABAA-receptors.

Stocchi, A., Lauke, B., Giannotti, M. I., Vázquez, A., Bernal, C., (2013). Tensile response and fracture and failure behavior of jute fabrics-flyash-vinylester hybrid composites Fibers and Polymers , 14, (2), 285-291

In this work, hybrid materials consisting on a vinylester matrix simultaneaously reinforced with jute woven fabrics and flyash particles were prepared. The tensile response and the fracture and failure behavior of these hybrid composites were investigated. Thermal stability of these materials was also studied. The aim was to obtain an environmentally friendly hybrid material with a good balance of tensile and fracture properties at relatively low cost. The effect of a novel treatment for the jute fabrics on the hybrids mechanical and fracture properties was investigated. The best balance of tensile and fracture properties was obtained for the hybrid consisting of fabrics treated with alkali under stress and fly ashes which also exhibited relatively high thermal stability.

Keywords: Natural fibers, Fly ash, Hybrid composite, Mechanical properties, Fracture

Guo, S., Artés, J. M., Díez-Pérez, I., (2013). Electrochemically-gated single-molecule electrical devices Electrochimica Acta 63rd Annual Meeting of the International Society of Electrochemistry , Elsevier (Prague, Czech Republic) 110, 741-753

In the last decade, single-molecule electrical contacts have emerged as a new experimental platform that allows exploring charge transport phenomena in individual molecular blocks. This novel tool has evolved into an essential element within the Molecular Electronics field to understand charge transport processes in hybrid (bio)molecule/electrode interfaces at the nanoscale, and prospect the implementation of active molecular components into functional nanoscale optoelectronic devices. Within this area, three-terminal single-molecule devices have been sought, provided that they are highly desired to achieve full functionality in logic electronic circuits. Despite the latest experimental developments offer consistent methods to bridge a molecule between two electrodes (source and drain in a transistor notation), placing a third electrode (gate) close to the single-molecule electrical contact is still technically challenging. In this vein, electrochemically-gated single-molecule devices have emerged as an experimentally affordable alternative to overcome these technical limitations. In this review, the operating principle of an electrochemically-gated single-molecule device is presented together with the latest experimental methodologies to built them and characterize their charge transport characteristics. Then, an up-to-date comprehensive overview of the most prominent examples will be given, emphasizing on the relationship between the molecular structure and the final device electrical behaviour.

Keywords: Electrochemical gate, Electrochemical switches, NDR, Single-molecule junctions, Unipolar/ambipolar FETs

Oncins, G., Roa, J. J., Rayón, E., Díaz, J., Morales, M., Segarra, M., Sanz, F., (2013). Friction, hardness and elastic modulus determined by AFM-FS and nanoindentation techniques for advanced ceramics materials Recent Advances in Ceramic Materials Research (ed. Roa, J. J., Semino, C. E.), Nova Science Publishers Materials Science and Technologies, 215-249

In the last years, nanoindentation by means of Atomic Force Microscopy-Force Spectroscopy (AFM-FS) or Nanoindenters has become a powerful tool to study the nanomechanics of all type of materials at micro-, nano- and also picometric scale, from soft metals, like copper, to brittle materials, as ceramics. The experimental basis of these techniques is the evaluation of the response of a material to an applied vertical load (in order to obtain the hardness, H, and the elastic modulus, E) or to a shear force (Lateral Force Microscopy, LFM) so as to obtain the friction coefficient, μ. In this work, the different methods to analyze friction, hardness and elastic modulus by means of AFM are explained for several examples as diamond single crystals, SiC single crystals, titanium dioxide coatings, mica and silicon oxide. Besides, examples of elastic deformation using nanoindentation are included. Moreover, several examples of results obtained by means of a Nanoindenter are also described in detail. A particular emphasis on ceramic coatings and advanced ceramic materials, such as YBaCuO superconductors, Yttria-stabilized zirconia, doped ceria electrolytes for fuel cells and yttria stabilized polycrystalline tetragonal zirconia, are reported and commented. The interest of these techniques is evidenced by the increasing quantity of nanomechanics-related papers published in the last decades, near a thousand of which appeared during the last five years. Unfortunately, a lot of practical information about nanomechanics of hard materials is still scarce in the literature (only one percent of the above mentioned publications are related to ceramic materials). This chapter aims to present the basic principles and methods applied to extract the different mechanical properties and also to review and comment real examples related to the cited techniques.

Gorostiza, Pau, (2012). Control celular mediante luz Investigación y Ciencia , 433, 11-12

Artés, Juan M., Díez-Pérez, Ismael, Gorostiza, Pau, (2012). Transistor-like behavior of single metalloprotein junctions Nano Letters 12, (6), 2679-2684

Single protein junctions consisting of azurin bridged between a gold substrate and the probe of an electrochemical tunneling microscope (ECSTM) have been obtained by two independent methods that allowed statistical analysis over a large number of measured junctions. Conductance measurements yield (7.3 ± 1.5) ? 10–6G0 in agreement with reported estimates using other techniques. Redox gating of the protein with an on/off ratio of 20 was demonstrated and constitutes a proof-of-principle of a single redox protein field-effect transistor.

Díez-Pérez, I., Li, Z., Guo, S., Madden, C., Huang, H., Che, Y., Yang, X., Zang, L., Tao, N., (2012). Ambipolar transport in an electrochemically gated single-molecule field-effect transistor ACS Nano 6, (8), 7044-7052

Charge transport is studied in single-molecule junctions formed with a 1,7-pyrrolidine-substituted 3,4,9,10-perylenetetracarboxylic diimide (PTCDI) molecular block using an electrochemical gate. Compared to an unsubstituted-PTCDI block, spectroscopic and electrochemical measurements indicate a reduction in the highest occupied (HOMO)-lowest unoccupied (LUMO) molecular orbital energy gap associated with the electron donor character of the substituents. The small HOMO-LUMO energy gap allows for switching between electron- and hole-dominated charge transports as a function of gate voltage, thus demonstrating a single-molecule ambipolar field-effect transistor. Both the unsubstituted and substituted molecules display similar n-type behaviors, indicating that they share the same n-type conduction mechanism. However, the substituted-PTCDI block shows a peak in the source-drain current vs gate voltage characteristics for the p-type transport, which is attributed to a two-step incoherent transport via the HOMO of the molecule.

Artés, Juan M., López-Martínez, Montserrat, Giraudet, Arnaud, Díez-Pérez, Ismael, Sanz, Fausto, Gorostiza, Pau, (2012). Current–Voltage characteristics and transition voltage spectroscopy of individual redox proteins Journal of the American Chemical Society 134, (50), 20218-20221

Understanding how molecular conductance depends on voltage is essential for characterizing molecular electronics devices. We reproducibly measured current?voltage characteristics of individual redox-active proteins by scanning tunneling microscopy under potentiostatic control in both tunneling and wired configurations. From these results, transition voltage spectroscopy (TVS) data for individual redox molecules can be calculated and analyzed statistically, adding a new dimension to conductance measurements. The transition voltage (TV) is discussed in terms of the two-step electron transfer (ET) mechanism. Azurin displays the lowest TV measured to date (0.4 V), consistent with the previously reported distance decay factor. This low TV may be advantageous for fabricating and operating molecular electronic devices for different applications. Our measurements show that TVS is a helpful tool for single-molecule ET measurements and suggest a mechanism for gating of ET between partner redox proteins. Understanding how molecular conductance depends on voltage is essential for characterizing molecular electronics devices. We reproducibly measured current?voltage characteristics of individual redox-active proteins by scanning tunneling microscopy under potentiostatic control in both tunneling and wired configurations. From these results, transition voltage spectroscopy (TVS) data for individual redox molecules can be calculated and analyzed statistically, adding a new dimension to conductance measurements. The transition voltage (TV) is discussed in terms of the two-step electron transfer (ET) mechanism. Azurin displays the lowest TV measured to date (0.4 V), consistent with the previously reported distance decay factor. This low TV may be advantageous for fabricating and operating molecular electronic devices for different applications. Our measurements show that TVS is a helpful tool for single-molecule ET measurements and suggest a mechanism for gating of ET between partner redox proteins.

Caballero-Briones, F., Palacios-Padrós, A., Calzadilla, O., Moreira, I. D. P. R., Sanz, F., (2012). Disruption of the chemical environment and electronic structure in p-type Cu2O films by alkaline doping Journal of Physical Chemistry C 116, (25), 13524-13535

In this work we present an experimental and theoretical study of Cu 2O films doped with alkaline ions (Li +, Na +, K +, and Cs +) prepared by Cu anodization. By X-ray photoelectron spectroscopy we determined dopant incorporation as high as 1% for Na +. Three oxygen species were found: O 2- ions in the bulk cuprite structure, adsorbed OH - and oxygen in hydroxylated dopant sites. The main effects of the alkaline doping on the optical properties were a reduction in the direct band gap and an approach of the acceptor level edge to the maximum of the valence band. Electrochemical tunneling microscopy experiments confirmed that the valence band maximum energy position is almost invariant. Additional electrochemical impedance, photoelectrochemical activity, and current sensing atomic force microscopy measurements showed an increase of the carrier density and electrical conductivity and a reduction in the photocurrent response with the dopant ion size. Urbach tail parameter analysis suggested additional interaction between copper vacancy derived states and dopant states. From first-principles calculations with the B3LYP hybrid functional on models for the alkaline-doped Cu 2O systems we determined that the main effect of the alkaline substitution of copper atoms consists of polarizing the O states, which causes a reduction in the insulating gap and splitting of the density of states just below the Fermi level. The nature of the oxygen-dopant interaction was also calculated: there is a net attractive interaction for Li-O, a slightly repulsive interaction for Na-O, and a net repulsive interaction for K-O and Cs-O. The repulsive interactions between K + or Cs + and O cause an accumulation of the dopant at the surface of the crystallites, whereas for Na + and Li + the doping ions are more uniformly distributed in the film bulk. It was found that the surface accumulation of K + and Cs + hinders vacancy diffusion and therefore blocks film growth, leading to a reduction of roughness and thickness as the ion size increases.

Darwish, Nadim., Díez-Pérez, I., Guo, S., Tao, N., Gooding, J. J., Paddon-Row, M. N., (2012). Single molecular switches: Electrochemical gating of a single anthraquinone-based norbornylogous bridge molecule Journal of Physical Chemistry C 116, (39), 21093-21097

Herein we report the electrochemical gating of a single anthraquinone-based molecule bridged between two gold electrodes using the STM break-junction technique. Once a molecule is trapped between the STM gold tip and the gold substrate, the potential is swept in order to alternate between the oxidized anthraquinone (AQ) and the reduced hydroanthraquinone (H 2AQ) forms. It is shown that the conductance increases about an order of magnitude with a net conversion from the oxidized AQ form to the reduced H 2AQ form. The results obtained from sweeping the potential (dynamic approach) on a single molecule are compared to those obtained from measuring the conductance at several fixed potentials (static approach). By comparing the static and dynamic approach, qualitative information about the kinetics of the redox conversion was achieved. The threshold potential of the conductance enhancement was found to shift to more negative potentials when the potential is swept at a single molecule. This shift is attributed to a slow redox conversion between the AQ and the H 2AQ forms. The hypothesis, of slow redox kinetics being responsible for the observed differences in the single-molecule conductance studies, was supported by electron transfer kinetics studies of bulk self-assembled monolayers using both cyclic voltammetry at different sweeping rates and electrochemical impedance spectroscopy.

Arimon, M., Sanz, F., Giralt, E., Carulla, N., (2012). Template-assisted lateral growth of amyloid-β42 fibrils studied by differential labeling with gold nanoparticles Bioconjugate Chemistry , 23, (1), 27-32

Amyloid-β protein (Aβ) aggregation into amyloid fibrils is central to the origin and development of Alzheimer’s disease (AD), yet this highly complex process is poorly understood at the molecular level. Extensive studies have shown that Aβ fibril growth occurs through fibril elongation, whereby soluble molecules add to the fibril ends. Nevertheless, fibril morphology strongly depends on aggregation conditions. For example, at high ionic strength, Aβ fibrils laterally associate into bundles. To further study the mechanisms leading to fibril growth, we developed a single-fibril growth assay based on differential labeling of two Aβ42 variants with gold nanoparticles. We used this assay to study Aβ42 fibril growth under different conditions and observed that bundle formation is preceded by lateral interaction of soluble Aβ42 molecules with pre-existing fibrils. Based on this data, we propose template-assisted lateral fibril growth as an additional mechanism to elongation for Aβ42 fibril growth.

Keywords: AFM, Beta-Amyloid Fibrils, Polymorphism, Association, Elongation, Dynamics, State

Redondo-Morata, L., Giannotti, M. I., Sanz, F., (2012). AFM-based force-clamp monitors lipid bilayer failure kinetics Langmuir 28, (15), 6403-6410

The lipid bilayer rupture phenomenon is here explored by means of atomic force microscopy (AFM)-based force clamp, for the first time to our knowledge, to evaluate how lipid membranes respond when compressed under an external constant force, in the range of nanonewtons. Using this method, we were able to directly quantify the kinetics of the membrane rupture event and the associated energy barriers, for both single supported bilayers and multibilayers, in contradistinction to the classic studies performed at constant velocity. Moreover, the affected area of the membrane during the rupture process was calculated using an elastic deformation model. The elucidated information not only contributes to a better understanding of such relevant process, but also proves the suitability of AFM-based force clamp to study model structures as lipid bilayers. These findings on the kinetics of lipid bilayers rupture could be extended and applied to the study of other molecular thin films. Furthermore, systems of higher complexity such as models mimicking cell membranes could be studied by means of AFM-based force-clamp technique.

Keywords: Chain-Length, Spectroscopy, Nanomechanics, Microscopy, Elasticity, Stability, Membranes, Reveals, Fusion, Ions

Redondo-Morata, L., Giannotti, M. I., Sanz, F., (2012). Influence of cholesterol on the phase transition of lipid bilayers: A temperature-controlled force spectroscopy study Langmuir 28, (35), 12851-12860

Cholesterol (Chol) plays the essential function of regulating the physical properties of the cell membrane by controlling the lipid organization and phase behavior and, thus, managing the membrane fluidity and its mechanical strength. Here, we explore the model system DPPC:Chol by means of temperature-controlled atomic force microscopy (AFM) imaging and AFM-based force spectroscopy (AFM-FS) to assess the influence of Chol on the membrane ordering and stability. We analyze the system in a representative range of compositions up to 50 mol % Chol studying the phase evolution upon temperature increase (from room temperature to temperatures high above the T m of the DPPC bilayer) and the corresponding (nano)mechanical stability. By this means, we correlate the mechanical behavior and composition with the lateral order of each phase present in the bilayers. We prove that low Chol contents lead to a phase-segregated system, whereas high contents of Chol can give a homogeneous bilayer. In both cases, Chol enhances the mechanical stability of the membrane, and an extraordinarily stable system is observed for equimolar fractions (50 mol % Chol). In addition, even when no thermal transition is detected by the traditional bulk analysis techniques for liposomes with high Chol content (40 and 50 mol %), we demonstrate that temperature-controlled AFM-FS is capable of identifying a thermal transition for the supported lipid bilayers. Finally, our results validate the AFM-FS technique as an ideal platform to differentiate phase coexistence and transitions in lipid bilayers and bridge the gap between the results obtained by traditional methods for bulk analysis, the theoretical predictions, and the behavior of these systems at the nanoscale.

Redondo-Morata, Lorena, Oncins, Gerard, Sanz, Fausto, (2012). Force spectroscopy reveals the effect of different ions in the nanomechanical behavior of phospholipid model membranes: The case of potassium cation Biophysical Journal , 102, (1), 66-74

How do metal cations affect the stability and structure of phospholipid bilayers? What role does ion binding play in the insertion of proteins and the overall mechanical stability of biological membranes? Investigators have used different theoretical and microscopic approaches to study the mechanical properties of lipid bilayers. Although they are crucial for such studies, molecular-dynamics simulations cannot yet span the complexity of biological membranes. In addition, there are still some experimental difficulties when it comes to testing the ion binding to lipid bilayers in an accurate way. Hence, there is a need to establish a new approach from the perspective of the nanometric scale, where most of the specific molecular phenomena take place. Atomic force microscopy has become an essential tool for examining the structure and behavior of lipid bilayers. In this work, we used force spectroscopy to quantitatively characterize nanomechanical resistance as a function of the electrolyte composition by means of a reliable molecular fingerprint that reveals itself as a repetitive jump in the approaching force curve. By systematically probing a set of bilayers of different composition immersed in electrolytes composed of a variety of monovalent and divalent metal cations, we were able to obtain a wealth of information showing that each ion makes an independent and important contribution to the gross mechanical resistance and its plastic properties. This work addresses the need to assess the effects of different ions on the structure of phospholipid membranes, and opens new avenues for characterizing the (nano)mechanical stability of membranes.

Keywords: Molecular-dynamics simulation, Liquid expanded monolayers, Lipid-bilayers, Hofmeister series, Monovalent salt, Phosphatidylcholine, Microscopy, Binding, Surfaces, NaCl

Hoyo, J., Torrent-Burgués, J., Guaus, E., (2012). Biomimetic monolayer films of monogalactosyldiacylglycerol incorporating ubiquinone Journal of Colloid and Interface Science , 384, (1), 189-197

Ubiquinone and plastoquinone are two of the main electron and proton shuttle molecules in biological systems, and monogalactosyldiacylglycerol (MGDG) is the most abundant lipid in the thylakoid membrane of chloroplasts. Saturated MGDG, ubiquinone-10 (UQ) and MGDG:UQ mixed monolayers at the air/water interface have been studied using surface pressure-area isotherms and Brewster Angle Microscopy. Moreover, the transferred Langmuir-Blodgett films have been observed by Atomic Force Microscopy. The results show that MGDG:UQ mixtures present more fluid phase than pure MGDG, indicating a higher order degree for the later. It is also observed an important influence of UQ on the MGDG matrix before UQ collapse pressure and a low influence after this event, due to UQ expulsion from the MGDG matrix. This expulsion leads to a similar remaining UQ content for all the tested mixtures, indicating a limiting content of this molecule in the MGDG matrix at high surface pressures. The thermodynamic studies confirm the stability of the MGDG:UQ mixtures at low surface pressures, although presenting a non-ideal behaviour. Results point to consider UQ as a good candidate for studies of artificial photosynthesis.

Keywords: AFM, BAM, Biomimetic films, Langmuir-Blodgett film, Monogalactosyldiacylglycerol, Ubiquinone

Hoyo, J., Guaus, E., Torrent-Burgués, J., Sanz, F., (2012). Electrochemical behaviour of mixed LB films of ubiquinone - DPPC Journal of Electroanalytical Chemistry , 669, 6-13

The structure and the electrochemical behaviour of Langmuir and Langmuir-Blodgett (LB) films of the biological ubiquinone-10 (UQ) and a mixture of dipalmytoilphosphatidylcholine (DPPC) and UQ at the molar ratios DPPC:UQ 5:1 and 10:1 have been investigated. The surface pressure-area isotherms of the Langmuir films and the AFM images of the LB films show the formation of a monolayer in the DPPC:UQ mixture till a certain surface pressure is attained, and then at higher surface pressures the UQ is progressively expelled. The cyclic voltammograms of DPPC:UQ LB films formed on indium tin oxide, ITO, at different surface pressures show one reduction and one oxidation peak at low surface pressures, but two or even more reduction and oxidations peaks at medium and high surface pressures. The electrochemical behaviour is correlated with the film structure.

Keywords: Cyclic voltammetry, Electron transfer, Langmuir-Blodgett, Lipid monolayer, Modified ITO electrode, Ubiquinone

Redondo, L., Giannotti, M. I., Sanz, F., (2012). Stability of lipid bilayers as model membranes: Atomic force microscopy and spectroscopy approach Atomic force microscopy in liquid (ed. Baró, A. M., Reifenberger, R. G.), Wiley-VCH Verlag GmbH & Co.KGaA (Weinheim, Germany) Part I: General Atomic Force Microscopy, 259-284

Diez-Perez, Ismael, Hihath, Joshua, Hines, Thomas, Wang, Zhong-Sheng, Zhou, Gang, Mullen, Klaus, Tao, Nongjian, (2011). Controlling single-molecule conductance through lateral coupling of [pi] orbitals Nature Nanotechnology , 6, (4), 226-231

In recent years, various single-molecule electronic components have been demonstrated(1). However, it remains difficult to predict accurately the conductance of a single molecule and to control the lateral coupling between the pi orbitals of the molecule and the orbitals of the electrodes attached to it. This lateral coupling is well known to cause broadening and shifting of the energy levels of the molecule; this, in turn, is expected to greatly modify the conductance of an electrodemolecule- electrode junction(2-6). Here, we demonstrate a new method, based on lateral coupling, to mechanically and reversibly control the conductance of a single-molecule junction by mechanically modulating the angle between a single pentaphenylene molecule bridged between two metal electrodes. Changing the angle of the molecule from a highly tilted state to an orientation nearly perpendicular to the electrodes changes the conductance by an order of magnitude, which is in qualitative agreement with theoretical models of molecular pi-orbital coupling to a metal electrode. The lateral coupling is also directly measured by applying a fast mechanical perturbation in the horizontal plane, thus ruling out changes in the contact geometry or molecular conformation as the source for the conductance change.

Keywords: Junction conductance, Electron-transport, Interface, Dependence, Mechanism, Length

Simao, C., Mas-Torrent, M., Crivillers, N., Lloveras, V., Artés, Juan Manuel, Gorostiza, Pau, Veciana, Jaume, Rovira, C., (2011). A robust molecular platform for non-volatile memory devices with optical and magnetic responses Nature Chemistry , 3, (5), 359-364

Bistable molecules that behave as switches in solution have long been known. Systems that can be reversibly converted between two stable states that differ in their physical properties are particularly attractive in the development of memory devices when immobilized in substrates. Here, we report a highly robust surface-confined switch based on an electroactive, persistent organic radical immobilized on indium tin oxide substrates that can be electrochemically and reversibly converted to the anion form. This molecular bistable system behaves as an extremely robust redox switch in which an electrical input is transduced into optical as well as magnetic outputs under ambient conditions. The fact that this molecular surface switch, operating at very low voltages, can be patterned and addressed locally, and also has exceptionally high long-term stability and excellent reversibility and reproducibility, makes it a very promising platform for non-volatile memory devices.

Keywords: Self-assembled monolayers, Chromophore-based monolayers, Ultrathin platinum films, Carbon free-radicals, Per-million levels, Polychlorotriphenylmethyl radicals, Electron-transfer, Surface, Logic, Quantification

Artés, Juan M., Díez-Pérez, Ismael, Sanz, Fausto, Gorostiza, Pau, (2011). Direct measurement of electron transfer distance decay constants of single redox proteins by electrochemical tunneling spectroscopy ACS Nano 5, (3), 2060-2066

We present a method to measure directly and at the single-molecule level the distance decay constant that characterizes the rate of electron transfer (ET) in redox proteins. Using an electrochemical tunneling microscope under bipotentiostatic control, we obtained current-distance spectroscopic recordings of individual redox proteins confined within a nanometric tunneling gap at a well-defined molecular orientation. The tunneling current decays exponentially, and the corresponding decay constant (β) strongly supports a two-step tunneling ET mechanism. Statistical analysis of decay constant measurements reveals differences between the reduced and oxidized states that may be relevant to the control of ET rates in enzymes and biological electron transport chains.

Keywords: Long-range electron transfer (LRET), Distance decay constant, Single-molecule electrochemistry, Redox enzyme, Metalloprotein, Blue copper protein, Azurin, Electrochemical scanning tunneling microscopy and spectroscopy, Nanoelectrodes, Debye length, Electrochemical charge screening

Giannotti, M. I., Esteban, O., Oliva, M., Garcia-Parajo, M. F., Sanz, F., (2011). pH-Responsive polysaccharide-based polyelectrolyte complexes as nanocarriers for lysosomal delivery of therapeutic proteins Biomacromolecules , American Chemical Society 12, (7), 2524-2533

Nanopharmaceutics composed of a carrier and a protein have the potential to improve the activity of therapeutical proteins. Therapy for lysosomal diseases is limited by the lack of effective protein delivery systems that allow the controlled release of specific proteins to the lysosomes. Here we address this problem by developing functional polyelectrolyte-based nanoparticles able to promote acidic pH-triggered release of the loaded protein. Trimethyl chitosan (TMC) was synthesized and allowed to form polyelectrolyte complexes (PECs) with the lysosomal enzyme α-GAL through self-assembly and ionotropic gelation, with average particle size <200 nm, polydispersity index (PDI) <0.2, ζ potential of 20 mV, and a protein loading efficiency close to 65%. These polyelectrolyte nanoparticles were stable and active under physiological conditions and able to release the enzyme at acidic pH, as demonstrated by in situ atomic force microscopy (AFM). These nanoparticles were further functionalized with Atto 647N for single-particle characterization and tracking their cellular uptake and fate using high-resolution fluorescence microscopy. In contrast with their precursor, TMC, PECs were efficiently internalized by human endothelial cells and mostly accumulated in lysosomal compartments. The superior physicochemical characteristics of the TMC/α-GAL PECs together with their excellent cellular uptake properties indicate their enormous potential as advanced protein delivery systems for the treatment of lysosomal storage diseases.

Keywords: -----

Caballero-Briones, F., Palacios-Padrós, A., Sanz, Fausto, (2011). CuInSe2 films prepared by three step pulsed electrodeposition. Deposition mechanisms, optical and photoelectrochemical studies Electrochimica Acta , 56, (26), 9556-9567

p-Type semiconducting copper indium diselenide thin films have been prepared onto In2O3:Sn substrates by a recently developed pulse electrodeposition method that consists in repeated cycles of three potential application steps. The Cu–In–Se electrochemical system and the related single component electrolytes were studied by cyclic voltammetry to identify the electrode processes and study the deposition processes. In situ atomic force microscopy measurements during the first 100 deposition cycles denote a continuous nucleation and growth mechanism. Particles removed by film sonication from some of the films were characterized by transmission electron microscopy and determined to consist in nanoscopic and crystalline CuInSe2. The remaining film is still crystalline CuInSe2, as assessed by X-ray diffraction. The chemical characterization by combined X-ray photoelectron spectroscopy, X-ray fluorescence and inductively coupled plasma optical emission spectroscopy, showed that films were Cu-poor and Se-poor. Raman characterization of the as-grown films showed that film composition varies with film thickness; thinner films are Se-rich, while thicker ones have an increased Cu–Se content. Different optical absorption bands were identified by the analysis of the UV–NIR transmittance spectra that were related with the presence of CuInSe2, ordered vacancy compounds, Se, Cu2−xSe and In2Se3. The photoelectrochemical activity confirmed the p-type character and showed a better response for the films prepared with the pulse method.

Keywords: CuInSe2, Solar cells, Electrodeposition, Optical properties, As-deposited films, ITO substrate

Roa, J. J., Oncins, G., Diaz, J., Capdevila, X. G., Sanz, F., Segarra, M., (2011). Study of the friction, adhesion and mechanical properties of single crystals, ceramics and ceramic coatings by AFM Journal of the European Ceramic Society 31, (4), 429-449

This paper reviews commonly used methods of analyzing and interpreting friction, adhesion and nanoindentation with an AFM tip test data, with a particular emphasis of the testing of single crystals, metals, ceramics and ceramic coatings. Experimental results are reported on the friction, mechanical and adhesion properties of these materials. The popularity of AFM testing is evidenced by the large quantity of papers that report such measurements in the last decade. Unfortunately, a lot of information about these topics is scare in the literature. The present paper is aimed to present the basic physical modelling employed and also some examples using each technique.

Keywords: Mechanical properties, Plasticity, Biomedical applications, Engine components

Roa, J. J., Oncins, G., Diaz, J., Sanz, F., Segarra, M., (2011). Calculation of young's modulus value by means of AFM Recent Patents on Nanotechnology , 5, (1), 27-36

In the last years, Atomic Force Microscopy (AFM) has become a powerful tool not only to study the surface morphology but also the nanomechanics of all kind of samples. In this paper, the applicability of this technique is reviewed and its basic aspects of operation, advantages and drawbacks of using the AFM probe as a picoindenter (Force Spectroscopy mode, FS-AFM) are discussed. The patents concerning picoindentation measurements are discussed in the text and special attention is paid to measurements performed on hard materials as ceramics, as they have not been as thoroughly reviewed in the literature as in the case of soft matter. The possibilities of AFM in the nanomechanics field include the quantitative determination of the Young's modulus (E) and the transition force from elastic to plastic deformation regimes, the measurement of adhesion forces and deformation mechanisms while applying vertical forces in the range from tens of pN to mu N.

Keywords: Hard materials, Young's modulus, AFM-FS, Picoindentation technique

Gorostiza, P., Isacoff, E.Y., (2011). Photoswitchable ligand-gated ion channels Photosensitive molecules for controlling biological function (ed. Chambers, J. J. , Kramer, R. H.), Springer (Saskatoon, Canada) 55, 267-285

Ligand-activated proteins can be controlled with light by means of synthetic photoisomerizable tethered ligands (PTLs). The application of PTLs to ligand-gated ion channels, including the nicotinic acetylcholine receptor and ionotropic glutamate receptors, is reviewed with emphasis on rational photoswitch design and the mechanisms of optical switching. Recently reported molecular dynamic methods allow simulation with high reliability of novel PTLs for any ligand-activated protein whose structure is known.

Keywords: Nicotinic acetylcholine receptor, Kainate receptor, Glutamate receptor, Photoisomerizable tether ligand (PTL), Optical switch, Nanotoggle, Azobenzene, Neurobiology,, Nanoengineering, Nanomedicine

Garcia-Manyes, S., Redondo-Morata, L., Oncins, G., Sanz, F., (2010). Nanomechanics of lipid bilayers: Heads or tails? Journal of the American Chemical Society American Chemical Society 132, (37), 12874-12886

Understanding the effect of mechanical stress on membranes is of primary importance in biophysics. Here we use force spectroscopy AFM to quantitatively characterize the nanomechanical stability of supported lipid bilayers as a function of their chemical composition. The onset of plastic deformation reveals itself as a repetitive jump in the approaching force curve, which represents a molecular fingerprint for the bilayer mechanical stability. By systematically probing a set of chemically distinct supported lipid bilayers (SLBs), we first show that both the headgroup and tail have a decisive effect on their mechanical properties. While the mechanical stability of the probed SLBs linearly increases by 3.3 nN upon the introduction of each additional -CH2- in the chain, it exhibits a significant dependence on the phospholipid headgroup, ranging from 3 nN for DPPA to 66 nN for DPPG. Furthermore, we also quantify the reduction of the membrane mechanical stability as a function of the number of unsaturations and molecular branching in the chemical structure of the apolar tails. Finally, we demonstrate that, upon introduction of cholesterol and ergosterol, contrary to previous belief the mechanical stability of membranes not only increases linearly in the liquid phase (DLPC) but also for phospholipids present in the gel phase (DPPC). Our results are discussed in the framework of the continuum nucleation model. This work highlights the compelling effect of subtle variations in the chemical structure of phospholipid molecules on the membrane response when exposed to mechanical forces, a mechanism of common occurrence in nature.

Keywords: Atomic-force microscopy, Molecular-dynamics simulation, Aqueous-electrolyte solutions, Supported planar membranes, Phospholipid-bilayers, Biological-membranes, Physical-properties, Fluid membranes, Model membranes, Chain-length

Sisquella, X., de Pourcq, K., Alguacil, J., Robles, J., Sanz, F., Anselmetti, D., Imperial, S., Fernàndez-Busquets, X., (2010). A single-molecule force spectroscopy nanosensor for the identification of new antibiotics and antimalarials FASEB Journal , 24, (11), 4203-4217

An important goal of nanotechnology is the application of individual molecule handling techniques to the discovery of potential new therapeutic agents. Of particular interest is the search for new inhibitors of metabolic routes exclusive of human pathogens, such as the 2-C-methyl-D-erythritol-4-phosphate (MEP) pathway essential for the viability of most human pathogenic bacteria and of the malaria parasite. Using atomic force microscopy single-molecule force spectroscopy (SMFS), we have probed at the single-molecule level the interaction of 1-deoxy-D-xylulose 5-phosphate synthase (DXS), which catalyzes the first step of the MEP pathway, with its two substrates, pyruvate and glyceraldehyde-3-phosphate. The data obtained in this pioneering SMFS analysis of a bisubstrate enzymatic reaction illustrate the substrate sequentiality in DXS activity and allow for the calculation of catalytic parameters with single-molecule resolution. The DXS inhibitor fluoropyruvate has been detected in our SMFS competition experiments at a concentration of 10 mu M, improving by 2 orders of magnitude the sensitivity of conventional enzyme activity assays. The binding of DXS to pyruvate is a 2-step process with dissociation constants of k(off) = 6.1 x 10(-4) +/- 7.5 x 10(-3) and 1.3 x 10(-2) +/- 1.0 x 10(-2) s(-1), and reaction lengths of x(beta) = 3.98 +/- 0.33 and 0.52 +/- 0.23 angstrom. These results constitute the first quantitative report on the use of nanotechnology for the biodiscovery of new antimalarial enzyme inhibitors and open the field for the identification of compounds represented only by a few dozens of molecules in the sensor chamber.

Keywords: Malaria, 2-C-methyl-D-erythritol-4-phosphate pathway, 1-deoxy-D-xylulose 5-phosphate synthase, Pyruvate, Glyceraldehyde-3-phosphate, Drug discovery

Fernàndez-Busquets, X., Ponce, J., Bravo, R., Arimon, M., Martianez, T., Gella, A., Cladera, J., Durany, N., (2010). Modulation of amyloid beta peptide(1-42) cytotoxicity and aggregation in vitro by glucose and chondroitin sulfate Current Alzheimer Research , 7, (5), 428-438

One mechanism leading to neurodegeneration during Alzheimer's Disease (AD) is amyloid beta peptide (A beta)-induced neurotoxicity. Among the factors proposed to potentiate A beta toxicity is its covalent modification through carbohydrate-derived advanced glycation endproducts (AGEs). Other experimental evidence, though, indicates that certain polymeric carbohydrates like the glycosaminoglycan (GAG) chains found in proteoglycan molecules attenuate the neurotoxic effect of A beta in primary neuronal cultures. Pretreatment of the 42-residue A beta fragment (A beta(1-42)) with the ubiquitous brain carbohydrates, glucose, fructose, and the GAG chondroitin sulfate B (CSB) inhibits A beta beta(1-42)-induced apoptosis and reduces the peptide neurotoxicity on neuroblastoma cells, a cytoprotective effect that is partially reverted by AGE inhibitors such as pyridoxamine and L-carnosine. Thioflavin T fluorescence measurements indicate that at concentrations close to physiological, only CSB promotes the formation of A beta amyloid fibril structure. Atomic force microscopy imaging and Western blot analysis suggest that glucose favours the formation of globular oligomeric structures derived from aggregated species. Our data suggest that at short times carbohydrates reduce A beta(1-42) toxicity through different mechanisms both dependent and independent of AGE formation.

Keywords: Alzheimer's disease, Advanced glycation endproducts, Amyloid fibrils, Amyloid beta peptide, Apoptosis, Carbohydrates, Glycosaminoglycans

Garcia-Manyes, S., Sanz, F., (2010). Nanomechanics of lipid bilayers by force spectroscopy with AFM: A perspective Biochimica et Biophysica Acta - Biomembranes , 1798, (4), 741-749

Lipid bilayers determine the architecture of cell membranes and regulate a myriad of distinct processes that are highly dependent on the lateral organization of the phospholipid molecules that compose the membrane. Indeed, the mechanochemical properties of the membrane are strongly correlated with the function of several membrane proteins, which demand a very specific, highly localized physicochemical environment to perform their function. Several mesoscopic techniques have been used in the past to investigate the mechanical properties of lipid membranes. However, they were restricted to the study of the ensemble properties of giant bilayers. Force spectroscopy with AFM has emerged as a powerful technique able to provide valuable insights into the nanomechanical properties of supported lipid membranes at the nanometer/nanonewton scale in a wide variety of systems. In particular, these measurements have allowed direct measurement of the molecular interactions arising between neighboring phospholipid molecules and between the lipid molecules and the surrounding solvent environment. The goal of this review is to illustrate how these novel experiments have provided a new vista on membrane mechanics in a confined area within the nanometer realm, where most of the specific molecular interactions take place. Here we report in detail the main discoveries achieved by force spectroscopy with AFM on supported lipid bilayers, and we also discuss on the exciting future perspectives offered by this growing research field.

Keywords: Force spectroscopy, Atomic force microscopy, Lipid bilayer, Nanomechanics

Palacios-Padros, A., Caballero-Briones, F., Sanz, F., (2010). Enhancement in as-grown CuInSe2 film microstructure by a three potential pulsed electrodeposition method Electrochemistry Communications , 12, (8), 1025-1029

P-type copper indium diselenide (CuInSe2) films have been prepared onto ITO substrates by an electrodeposition method, that sequentially applies potential pulses at the deposition potential of each element Cu, Se and In, and then step it back in cyclically to induce the solid state reaction between the elements. Two electrolyte concentrations as well as three different pulse durations were assessed. The resulting films were compared with those deposited at fixed electrode potentials. As-grown films are nanocrystalline and have an E-g similar to 0.95 eV. Raman spectroscopy shows that Se and Cu-Se contents decrease while pulse duration increases and electrolyte concentration decreases. Cu-Se phases are even absent for films grown at the low electrolyte concentration. These results represent a great improvement in the film phase purity reducing the need of post-deposition treatments.

Keywords: CIS, Pulsed electrodeposition, Raman, Solar cells

Caballero-Briones, F., Palacios-Padros, A., Calzadilla, O., Sanz, F., (2010). Evidence and analysis of parallel growth mechanisms in Cu2O films prepared by Cu anodization Electrochimica Acta , 55, (14), 4353-4358

We have studied the preparation of Cu2O films by copper anodization in a 0.1 M NaOH electrolyte. We identified the potential range at which Cu dissolution takes place then we prepared films with different times of exposure to this potential. The morphology, crystalline structure, band gap. Urbach energy and thickness of the films were studied. Films prepared with the electrode unexposed to the dissolution potential have a pyramidal growth typical of potential driven processes, while samples prepared at increasing exposure times to dissolution potential present continuous nucleation, growth and grain coalescence. We observed a discrepancy in the respective film thicknesses calculated by coulometry, atomic force microscopy and optical reflectance. We propose that anodic Cu2O film formation involves three parallel mechanisms (i) Cu2O nucleation at the surface, (ii) Cu+ dissolution followed by heterogeneous nucleation and (iii) Cu+ and OH- diffusion through the forming oxide and subsequent reaction in the solid state.

Keywords: Cuprous oxide, Anodic films, Reflectance, Thickness, Band gap, Urbach tail parameter, Dissolution, Growth mechanism

Carulla, N., Zhou, M., Arimon, M., Gairi, M., Giralt, E., Robinson, C. V., Dobson, C. M., (2009). Experimental characterization of disordered and ordered aggregates populated during the process of amyloid fibril formation Proceedings of the National Academy of Sciences of the United States of America 106, (19), 7828-7833

Recent experimental evidence points to intermediates populated during the process of amyloid fibril formation as the toxic moieties primarily responsible for the development of increasingly common disorders such as Alzheimer's disease and type II diabetes. We describe here the application of a pulse-labeling hydrogendeuterium (HD) exchange strategy monitored by mass spectrometry (MS) and NMR spectroscopy (NMR) to characterize the aggregation process of an SH3 domain under 2 different conditions, both of which ultimately lead to well-defined amyloid fibrils. Under one condition, the intermediates appear to be largely amorphous in nature, whereas under the other condition protofibrillar species are clearly evident. Under the conditions favoring amorphous-like intermediates, only species having no protection against HD exchange can be detected in addition to the mature fibrils that show a high degree of protection. By contrast, under the conditions favoring protofibrillar-like intermediates, MS reveals that multiple species are present with different degrees of HD exchange protection, indicating that aggregation occurs initially through relatively disordered species that subsequently evolve to form ordered aggregates that eventually lead to amyloid fibrils. Further analysis using NMR provides residue-specific information on the structural reorganizations that take place during aggregation, as well as on the time scales by which they occur.

Keywords: Aggregation, HD exchange, Misfolding intermediates, PI3-SH3

Arteaga, O., Escudero, C., Oncins, G., El-Hachemic, Z., Llorens, J., Crusats, J., Canillas, A., Ribo, J. M., (2009). Reversible mechanical induction of optical activity in solutions of soft-matter nanophases Chemistry - An Asian Journal , 4, (11), 1687-1696

Nanophases of J-aggregates of several achiral amphiphilic porphyrins, which have thin long acicular shapes (nanoribbons), show the immediate and reversible formation of a stationary mechano-chiral state in the solution by vortex stirring, as detected by their circular dichroic signals measured by 2-modulator generallized ellipsometry. The results suggest that when a macroscopic chiral force creates supramolecular chirality, it also creates an enantiomeric excess of screw distortions, which may be detected by their excitonic absorption. An explanation on the effect of the shear flow gradients is proposed on the basis of the orientation of the rotating particles in the vortex and the size, shape, and mechanical properties of the nanoparticles.

Keywords: Chirality, Circular dichroism, Nanoparticles, Selfassembly, Supramolecular chemistry

Caballero-Briones, F., Artes, J. M., Diez-Perez, I., Gorostiza, P., Sanz, F., (2009). Direct observation of the valence band edge by in situ ECSTM-ECTS in p-type Cu2O layers prepared by copper anodization Journal of Physical Chemistry C 113, (3), 1028-1036

Polycrystalline Cu2O layers have been selectively grown by electrochemical anodization of polycrystalline Cu electrodes in an alkaline medium (pH 12.85). Uniform layers with thicknesses around 100 nm have been obtained. Using electrochemical impedance spectroscopy, it was concluded that the Cu2O films behave as a p-type semiconductor. The Mott-Schottky plot gives a value for the flat band potential of U-FB = -255 mV vs silver/silver chloride electrode (SSC), an estimated carrier density N-A = 6.1 x 10(17) cm(-3), and the space charge layer width was calculated to be W-SCL = 9 nm at a band bending of 120 mV. The electronic structure of the Cu vertical bar Cu2O vertical bar electrolyte interface was for the first time probed by in situ electrochemical tunneling spectroscopy. The use of in situ electrochemical scanning tunneling microscopy allows us to directly observed the valence band edge and determine its position against the absolute energy scale to be E-VB = -4.9 eV. Finally, we constructed a quantitative electronic diagram of the Cu vertical bar Cu2O vertical bar electrolyte interface, where the positions of the valence and conduction band edges are depicted, as well as the edge of the previously reported electronic subband.

Keywords: 0.1 m NaOH, Electrochemical tunneling spectroscopy, Cuprous-oxide films, Anodic-oxidation, Electronic-structure, Alkaline-solution, Aqueous-solution, Initial-stages, Passive film, Thin-films

Nussio, M. R., Oncins, G., Ridelis, I., Szili, E., Shapter, J. G., Sanz, F., Voelcker, N. H., (2009). Nanomechanical characterization of phospholipid bilayer islands on flat and porous substrates: A force spectroscopy study Journal of Physical Chemistry B , 113, (30), 10339-10347

In this study, we compare for the first time the nanomechanical properties of lipid bilayer islands on flat and porous surfaces. 1,2-Dimyzistoyl-sn-glycero-3-phosphatidylcholine (DMPC) and 1,2-dipalmitoyl-sn-glycero-3-phosphatidylcholine (DPPC) bilayers were deposited on flat (silicon and mica) and porous silicon (pSi) substrate surfaces and examined using atomic force spectroscopy and force volume imaging. Force spectroscopy measurements revealed the effects of the underlying substrate and of the lipid phase on the nanomechanical properties of bilayers islands. For mica and silicon, significant differences in breakthrough force between the center and the edges of bilayer islands were observed for both phospolipids. These differences were more pronounced for DMPC than for DPPC, presumably due to melting effects at the edges of DMPC bilayers. In contrast, bilayer islands deposited on pSi yielded similar breakthrough forces in the central region and along the perimeter of the islands, and those values in turn were similar to those measured along the perimeter of bilayer islands deposited on the flat substrates. The study also demonstrates that pSi is suitable solid support for the formation of pore-spanning phospholipid bilayers with potential applications in transmembrane protein studies, drug delivery, and biosensing.

Keywords: Black lipid-membranes, Gold surfaces, Supported bilayers, Channel activity, Micro-BLMS, Silicon, Proteins, Vesicles, AFM, Temperature measurement

Gorostiza, P., Isacoff, E. Y., (2008). Optical switches for remote and noninvasive control of cell signaling Science 322, (5900), 395-399

Although the identity and interactions of signaling proteins have been studied in great detail, the complexity of signaling networks cannot be fully understood without elucidating the timing and location of activity of individual proteins. To do this, one needs a means for detecting and controlling specific signaling events. An attractive approach is to use light, both to report on and control signaling proteins in cells, because light can probe cells in real time with minimal damage. Although optical detection of signaling events has been successful for some time, the development of the means for optical control has accelerated only recently. Of particular interest is the development of chemically engineered proteins that are directly sensitive to light.

Keywords: Ion channels, Acetylcholine receptor, Glutamate-receptor, Potassium channel, K+ channel, Light, Neurons, Channelrhodopsin-2, Manipulation, Activation

Gorostiza, P., Isacoff, E. Y., (2008). Nanoengineering ion channels for optical control Physiology , 23, (5), 238-247

Chemical modification with photoisomerizable tethered ligands endows proteins with sensitivity to light. These optically actuated proteins are revolutionizing research in biology by making it possible to manipulate biological processes noninvasively and with unprecedented spatiotemporal resolution.

Keywords: -----

Olmedo, Ivonne, Araya, Eyleen, Sanz, Fausto, Medina, Elias, Arbiol, Jordi, Toledo, Pedro, Àlvarez-Lueje, Alejandro, Giralt, Ernest, Kogan, Marcelo J., (2008). How changes in the sequence of the peptide CLPFFD-NH2 can modify the conjugation and stability of gold nanoparticles and their affinity for beta-amyloid fibrils Bioconjugate Chemistry , 19, (6), 1154-1163

In a previous work, we studied the interaction of β-amyloid fibrils (Aβ) with gold nanoparticles (AuNP) conjugated with the peptide CLPFFD-NH2. Here, we studied the effect of changing the residue sequence of the peptide CLPFFD-NH2 on the efficiency of conjugation to AuNP, the stability of the conjugates, and the affinity of the conjugates to the Aβ fibrils. We conjugated the AuNP with CLPFFD-NH2 isomeric peptides (CDLPFF-NH2 and CLPDFF-NH2) and characterized the resulting conjugates with different techniques including UV−Vis, TEM, EELS, XPS, analysis of amino acids, agarose gel electrophoresis, and CD. In addition, we determined the proportion of AuNP bonded to the Aβ fibrils by ICP-MS. AuNP-CLPFFD-NH2 was the most stable of the conjugates and presented more affinity for Aβ fibrils with respect to the other conjugates and bare AuNP. These findings help to better understand the way peptide sequences affect conjugation and stability of AuNP and their interaction with Aβ fibrils. The peptide sequence, the steric effects, and the charge and disposition of hydrophilic and hydrophobic residues are crucial parameters when considering the design of AuNP peptide conjugates for biomedical applications.

Keywords: Self-assembled monolayers, Aggregation, Dispersions, Adsorption, Particles, Design, Size

Caballero-Briones, F., Palacios-Padros, A., Pena, J. L., Sanz, F., (2008). Phase tailored, potentiodynamically grown P-Cu2-xTe/Cu layers Electrochemistry Communications , 10, (11), 1684-1687

In this work we successfully prepared p-type semiconducting Cu2-xTe layers on Cu substrates by applying a potential multistep signal. Spontaneously deposited tellurium layers were reduced in a single cathodic sweep. The X-ray diffraction characterization showed the presence of single-phased, crystalline Cu2-xTe in the weissite form. A further anodization step allows crystallization of several phases such as CU1.75Te, Cu0.664Te0.336 and CU7Te4. This type of sample was found to be photoactive. The prepared films are p-type and have carrier concentrations in the order of 10(21) CM-3, suitable for CdTe-CU2-xTe contacts.

Keywords: Copper telluride, Electrochemical signal, XRD, Morphology, EIS, Photocurrent, Telluride thin-films, Solar cells, Deposition, Cu

Arimon, M., Grimminger, V., Sanz, F., Lashuel, H. A., (2008). Hsp104 targets multiple intermediates on the amyloid pathway and suppresses the seeding capacity of A beta fibrils and protofibrils Journal of Molecular Biology , 384, (5), 1157-1173

The heat shock protein Hsp104 has been reported to possess the ability to. modulate protein aggregation and toxicity and to "catalyze" the disaggregation and recovery of protein aggregates, including amyloid fibrils, in yeast, Escherichia coli, mammalian cell cultures, and animal models of Huntington's disease and Parkinson's disease. To provide mechanistic insight into the molecular mechanisms by which Hsp104 modulates aggregation and fibrillogenesis, the effect of Hsp104 on the fibrillogenesis of amyloid beta (A(3) was investigated by characterizing its ability to interfere with oligomerization and fibrillogenesis of different species along the amyloid-formation pathway of A beta. To probe the disaggregation activity of Hsp104, its ability to dissociate preformed protofibrillar and fibrillar aggregates of A beta was assessed in the presence and in the absence of ATP. Our results show that Hsp104 inhibits the fibrillization of monomeric and protofibrillar forms of A beta in a concentration-dependent but ATP-independent manner. Inhibition of A beta fibrillization by Hsp104 is observable up to Hsp104/A beta stoichiometric ratios of 1:1000, suggesting a preferential interaction of Hsp104 with aggregation intermediates (e.g., oligomers, protofibrils, small fibrils) on the pathway of A beta amyloid formation. This hypothesis is consistent with our observations that Hsp104 (i) interacts with A beta protofibrils, (ii) inhibits conversion of protofibrils into amyloid fibrils, (iii) arrests fibril elongation and reassembly, and (iv) abolishes the capacity of protofibrils and sonicated fibrils to seed the fibrillization of monomeric A beta. Together, these findings suggest that the strong inhibition of A beta fibrillization by Hsp104 is mediated by its ability to act at different stages and target multiple intermediates on the pathway to amyloid formation.

Keywords: Amyloid formation A beta, Hsp104, Disaggregation, Alzheimer's diseases

Oncins, G., Torrent-Burgues, J., Sanz, F., (2008). Nanomechanical properties of arachidic acid Langmuir-Blodgett films Journal of Physical Chemistry C 112, (6), 1967-1974

The nanomechanical properties of Langmuir-Blodgett monolayers of arachidic acid extracted at surface pressures of 1, 15, and 35 mN/m and deposited on mica were investigated by atomic force microscopy, force spectroscopy, and lateral force microscopy. It was experimentally demonstrated that the arachidic acid molecular orientation depends on the extraction pressure. According to this, tilting angles of 50, 34, and 22 degrees with respect to the surface perpendicular were detected and identified as conformations that maximize van der Waals interactions between the arachidic acid alkyl chains. The vertical force needed to puncture the monolayers with the AFM tip strongly depends on the molecular tilting angles attained at different monolayer extraction surface pressures, obtaining values that range from 13.07 +/- 3.24 nN for 50 degrees to 22.94 +/- 5.49 nN for 22 degrees tilting angles. The different molecular interactions involved in the monolayer cohesion are discussed and quantitatively related to the experimental monolayer breakthrough forces. The friction measurements performed from low vertical forces up to monolayer disruption reveal the existence of three well-defined regimes: first, a low friction response due to the elastic deformation of the monolayer, which is followed by a sharp increase in the friction force due to the onset of a sudden plastic deformation. The last regime corresponds to the monolayer rupture and the contact between tip and substrate. The friction coefficient of the substrate is seen to depend on the monolayer extraction pressure, a fact that is discussed in terms of the relationship between the sample compactness and its rupture mechanism.

Keywords: AFM, SAM, Reflection-absortion spectroscopy, Lipid-bilayers, Frictional-properies, Molecular-structure, Thermal behavior, Nanometer-scale, Chain-length, LB films

Oncins, Gerard, Vericat, Carolina, Sanz, Fausto, (2008). Mechanical properties of alkanethiol monolayers studied by force spectroscopy Journal of Chemical Physics , 128, (4), 044701

The mechanical properties of alkanethiol monolayers on Au(111) in KOH solution have been studied by force spectroscopy. The analysis of the vertical force versus penetration curves showed that monolayer penetration is a stepped process that combines elastic regions with sudden penetration events. The structural meaning of these events can be explained both by the creation of gauche defects on the hydrocarbon chains and by a cooperative molecular tilting model proposed by Barrena et al. [J. Chem. Phys. 113, 2413 (2000)]. The validity of these models for alkanethiol monolayers of different compactness and chain length has been discussed. The Young's modulus (E) of the monolayers has been calculated by using a recently developed model which considers the thickness of the monolayer as a parameter, thus allowing a decoupling of the mechanical properties of the thiol layer from those of the Au(111) substrate. As a result, the calculated E values are in the range of 50-150 Pa, which are remarkably lower than those previously reported in the literature.

Keywords: Adsorbed layers, AFM, Gold, Monolayers, Organic compounds, Self-assemblyYoung's modulus

Torrent-Burgues, J., Oncins, G., Sanz, F., (2008). Study of mixed Langmuir and Langmuir-Blodgett films of dissimilar components by AFM and force spectroscopy Colloids and Surfaces a-Physicochemical and Engineering Aspects 12th International Conference on Organized Molecular Films , Elsevier Science (Krakow, Poland) 321, (1-3), 70-75

In this study the structure of mixed Langmuir-Blodgett (LB) monolayers has been investigated using atomic force microscopy, lateral force microscopy and force spectroscopy, as well as the characteristics of the Langmuir monolayers by surface pressure-area isotherms and Brewster angle microscopy. Mixed films were of dissimilar compounds, a fatty acid such as arachidic acid and a macrocyclic compound. The mixture forms separated phases, but some degree of partial miscibility occurs, with domains at the micro-scale that have different nanomechanical and nanotribological properties. LB films transferred at the same surface pressure show different characteristics depending on the composition. The higher domains correspond to arachidic acid and some of these domains show the presence of two phases, which have been identified as phases with discrete molecular tilting angles.

Keywords: Mixed monolayers, Pressure-area isotherm, Langmuir-Blodgett, AFM, Force spectroscopy

Díez-Pérez, Ismael, Guell, Aleix Garcia, Sanz, Fausto, Gorostiza, Pau, (2006). Conductance maps by electrochemical tunneling spectroscopy to fingerprint the electrode electronic structure Analytical Chemistry , 78, (20), 7325-7329

We describe a methodology to perform reliable tunneling spectroscopy in electrochemical media. Sequential in situ tunneling spectra are recorded while the electrochemical potential of the electrode is scanned. Spectroscopic data are presented as conductance maps or conductograms that show the in situ electronic structure of an electrode surface while it undergoes an electrochemical reaction. The conductance map or conductogram represents the redox fingerprint of an electrode/liquid interface in a specific medium and can serve to predict its electrochemical behavior in a quantitative energy scale. The methodology is validated studying the reversible oxidation and passivity of an iron electrode in borate buffer, and we describe the main quantitative information that can be extracted concerning the semiconducting properties of the Fe passive film. This methodology is useful to study heterogeneous catalysis, electrochemical sensing and bioelectronic systems.

Keywords: Passive film, Oxide-film, Stainless-steel, Iron, Microscope, Surfaces, STM, Probes

Díez-Pérez, Ismael, Sanz, Fausto, Gorostiza, Pau, (2006). Electronic barriers in the iron oxide film govern its passivity and redox behavior: Effect of electrode potential and solution pH Electrochemistry Communications , 8, (10), 1595-1602

We have measured in situ the electronic conductance spectra of the passive film formed on an Fe electrode immersed in a borate buffer solution using electrochemical tunneling spectroscopy (ECTS) and electrochemical impedance spectroscopy (EIS) techniques, and we have followed their changes as the electrode is electrochemically oxidized and reduced. We demonstrate that pre-passive Fe(II) oxide and the passive Fe(II)/Fe(III) film, behave as p- and n-type semiconductors, respectively and that their reversible inter-conversion is mediated by the availability of free charge carriers on the electrode surface. ECTS spectra have been also modeled to obtain the main electrochemical kinetic parameters of the electron transfer through both p-Fe(II) and n-Fe(III) oxides at different sample potentials and pHs values. We find that the electronic energy barrier in the oxide and its dependence with electrode potential and solution pH, determine the reactivity and passivity of iron.

Keywords: Electrochemical tunneling spectroscopy, Fe passivity Electronic energy barriers, pH effect on passivity

Díez-Pérez, Ismael, Vericat, Carolina, Gorostiza, Pau, Sanz, Fausto, (2006). The iron passive film breakdown in chloride media may be mediated by transient chloride-induced surface states located within the band gap Electrochemistry Communications , 8, (4), 627-632

Despite its tremendous scientific and economic impact, the mechanism that triggers metal passive film breakdown in the presence of aggressive ions remains under discussion. We have studied the iron passive film in chloride media using X-ray photoelectron spectroscopy (XPS), electrochemical impedance spectroscopy and electrochemical tunneling spectroscopy (ECTS). Ex situ XPS reveal that the film consists exclusively of an Fe(III) oxide without chloride content. In situ ECTS has been used to build up conductance maps of the Fe electrode during its electrochemical oxidation in a borate buffer solution and its breakdown when the film is grown in the presence of chloride. This conductograms provide direct and in situ experimental evidence of chloride-induced surface states within the band gap of the oxide film (~3.3eV). These states enable new charge exchange pathways that allow hole capture at the surface of the n-type Fe(III) oxide. The blocking of VB processes that occurs in the iron passive film is no longer present in chloride media, and electrode corrosion can proceed through these new states. We propose a simple 3-step mechanism for the process, in which chloride anions form an oxidizing Fe(II) surface intermediate but do not participate directly in the reaction.

Keywords: Electrochemical tunneling spectroscopy, Electronic band structure, Fe passive film, Aqueous chloride corrosion, Semiconductor decomposition, Interface states


  • iMic molecular imaging system
  • Electrochemical scanning tunnelling microscope (STM) for molecular imaging
  • Asylum Research Molecular Force Probe
  • Multimode SPM Nanoscope III (SCT-UB)
  • Autolab potentiostat
  • Patch clamp setup with Heka EPC10 amplifier
  • Molecular Imaging Electrochemical STM


  • Prof. Amadeu Llebaria
    Institut de Química Avançada de Catalunya (IQAC-CSIC)
  • Prof. Ernest Giralt
    Dept. de Química Orgànica, Universitat de Barcelona
  • Prof. Miquel Àngel Pericàs
    Institut Català d’Investigació Química (ICIQ), Tarragona
  • Dr. Piotr Bregestovski
    Institut de Neurobiologie de la Mediterraneé (INMED), Marseille
  • Dr. Mireia Oliva
    Dept. de Farmàcia i Tecnologia Farmacèutica, Universitat de Barcelona
  • Dr. Artur Llobet
    Dept. Patología y Terapéutica Experimental, Universitat de Barcelona
  • Dr. Joan Torrent
    Escola Universitària d’Òptica i Optometria de Terrassa, Spain
  • Prof. Dirk Trauner
    Chemistry Dept., UC Berkeley, USA
  • Prof. Carles Solsona
    Pathology and Experimental Therapeutics Dept, UB
  • Prof. Francisco Ciruela
    ICREA / Universitat de Barcelona, Spain
  • Prof. Jesús Giraldo & Dr. Jordi Hernando
    Universitat Autònoma de Barcelona, Spain



We are happy to receive CVs and enquiries from talented individuals. Prospective students and staff are encouraged to contact us to discuss possibilities. Please feel free to suggest new projects, areas of research or new ideas.

You can visit the jobs page to find currents job openings in all IBEC groups or administration positions.


New chemical lego blocks for health solutions

IBEC researchers develop new multi-responsive molecules able to self-assemble in water forming fiber-like structures. The so-called discotic molecules show responsiveness to temperature, light, pH, and ionic strength and they might show great potential for medical applications such as drug delivery systems, diagnosis or tissue engineering.

Edgar Fuentes is a PhD student in the Nanoscopy for Nanomedicine Group led by Lorenzo Albertazzi at the Institute for Bioengineering of Catalonia (IBEC). Within this group, Edgar and his colleagues focus on the synthesis of novel smart supramolecular materials for drug delivery.

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Rossella Castagna, postdoctoral researcher at IBEC wins the ISOP2019 prize

Rossella Castagna a postdoctoral researcher in the Nanoprobes and Nanowitches group at IBEC was awared with the ISOP2019 prize last week 9th International Symposium on Photochromism held in Paris. This recognition comes from her contribution to the field of photochromism and for the results that were collectively obtained in their group in the field of photopharmacology.

Rossella presented the group results on photoswitchable drugs at the reference international meeting for photochromism, held every 3 years, where she was awarded with the conference prize. According to the organizing committee, such a prize rewards the most talented young researchers whose contribution is expected to notably impact the field of photochromism.

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Three researchers from IBEC awarded with grants from “la Caixa” for their pioneering and high social impact research

José Antonio del Río, Pau Gorostiza, and Samuel Sánchez have been awarded in two of the “la Caixa” calls.

José Antonio del Río, principal investigator of the Molecular and Cellular Neurobiotechnology Group at IBEC, is one of the winners of the second edition of the call for applications in biomedicine and health. Del Río’s project focuses on analysing the molecular mechanisms involved in the genesis and propagation of tau protein in brain cells. This protein is linked with several neurodegenerative processes and is present in numerous diseases such as Alzheimer’s.

Pau Gorostiza, principal investigator of the Nanoprobes and Nanoswitches Group, also received an award at the second edition of the call for applications for research projects in biomedicine and health. In this case, for his project on degenerative eye conditions such as retinitis pigmentosa, which causes blindness due to the progressive degeneration of the cones and rods, which are the light sensitive cells.

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Closer to a functional atlas of the brain

Scientists from the Institute for Bioengineering of Catalonia develop a technique that enables them to work out the specific function of a neuronal receptor according to its location in the brain. The study, published in PNAS, is based on the activation of photoswitchable drugs with micrometric precision and offers new opportunities in neurobiology.

Schizophrenia, depression, myasthenia… Many neurological diseases are due to the malfunctioning of a neuronal receptor. These proteins, also known as neuroreceptors, are responsible for sending and detecting neurotransmitters, chemical substances that allow communication between neurons.

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ERC President visits IBEC

The President of the European Research Council, Jean-Pierre Bourguignon, visited last May 15th the Institute for Bioengineering of Catalonia (IBEC).

The event was inaugurated by IBEC’s Director, Josep Samitier, who presented an overview on the cutting-edge research carried out at the institute in the fields of bioengineering and nanomedicine.

Afterwards, ERC Grantees working at IBEC had the opportunity to explain the impact of ERC grants on their professional careers and established a dialogue with ERC President on the past, present and future of the European Research Council.

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A new technique allows researchers to focus the action of drugs via infrared light

A scientific team led by IBEC and UAB manages to efficiently activate molecules located inside cell tissues using two-photon excitation of with infrared light lasers. The results of the study has been published in Nature Communications.

Having absolute control of the activity of a molecule in an organism. Deciding when, where and how a drug is activated. These are some of the goals expected to be reached with the so-called photoswitchable molecules, compounds that, in the presence of certain light waves, change their properties. Today, thanks to the results of a study led by the Institute for Bioengineering of Catalonia (IBEC) together with the Universitat Autònoma de Barcelona (UAB), the scientific community is one step closer to achieving this objective.

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Proteins can transfer electrons at a distance

Collaborating IBEC groups have published a study in Nature Communications that reveals that electron transfer can take place while a protein is approaching its partner site, and not only when the proteins are engaged, as was previously thought.

The results open up a new way of thinking about how proteins interact, and can have implications in a better understanding of many processes – such as photosynthesis, respiration and detoxification – in which electron transfer plays an important role.

The relocation of an electron from one chemical entity to another – electron transfer (ET) – doesn’t happen passively: electrons are carried individually by redox proteins.

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IBEC researchers uncover strategy to reduce chemotherapy side effects

Researchers at IBEC and IDIBELL have developed a light-regulated molecule that could improve chemotherapy treatments by controlling the activity of anticancer agents.

Chemotherapy – the use of cytotoxic agents to kill the rapidly proliferating cells in tumors – is one of our main tools in the fight against cancer. However, its effectiveness and the body’s tolerance of it is often dramatically limited: it can affect healthy areas rather than just the cancerous ones, which causes side effects.

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