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by Keyword: Gold


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Vukomanovic, M., Torrents, E., (2019). High time resolution and high signal-to-noise monitoring of the bacterial growth kinetics in the presence of plasmonic nanoparticles Journal of Nanobiotechnology 17, (1), 21

Background: Emerging concepts for designing innovative drugs (i.e., novel generations of antimicrobials) frequently include nanostructures, new materials, and nanoparticles (NPs). Along with numerous advantages, NPs bring limitations, partly because they can limit the analytical techniques used for their biological and in vivo validation. From that standpoint, designing innovative drug delivery systems requires advancements in the methods used for their testing and investigations. Considering the well-known ability of resazurin-based methods for rapid detection of bacterial metabolisms with very high sensitivity, in this work we report a novel optimization for tracking bacterial growth kinetics in the presence of NPs with specific characteristics, such as specific optical properties. Results: Arginine-functionalized gold composite (HAp/Au/arginine) NPs, used as the NP model for validation of the method, possess plasmonic properties and are characterized by intensive absorption in the UV/vis region with a surface plasmon resonance maximum at 540 nm. Due to the specific optical properties, the NP absorption intensively interferes with the light absorption measured during the evaluation of bacterial growth (optical density; OD600). The results confirm substantial nonspecific interference by NPs in the signal detected during a regular turbidity study used for tracking bacterial growth. Instead, during application of a resazurin-based method (Presto Blue), when a combination of absorption and fluorescence detection is applied, a substantial increase in the signal-to-noise ratio is obtained that leads to the improvement of the accuracy of the measurements as verified in three bacterial strains tested with different growth rates (E. coli, P. aeruginosa, and S. aureus). Conclusions: Here, we described a novel procedure that enables the kinetics of bacterial growth in the presence of NPs to be followed with high time resolution, high sensitivity, and without sampling during the kinetic study. We showed the applicability of the Presto Blue method for the case of HAp/Au/arginine NPs, which can be extended to various types of metallic NPs with similar characteristics. The method is a very easy, economical, and reliable option for testing NPs designed as novel antimicrobials.

Keywords: Antimicrobial nanoparticles, Arginine-functionalized gold, Bacterial growth kinetics, Plasmonic nanoparticles, Presto Blue


Silva, N., Riveros, A., Yutronic, N., Lang, E., Chornik, B., Guerrero, S., Samitier, J., Jara, P., Kogan, M. J., (2018). Photothermally controlled methotrexate release system using β-cyclodextrin and gold nanoparticles Nanomaterials 8, (12), 985

The inclusion compound (IC) of cyclodextrin (CD) containing the antitumor drug Methotrexate (MTX) as a guest molecule was obtained to increase the solubility of MTX and decrease its inherent toxic effects in nonspecific cells. The IC was conjugated with gold nanoparticles (AuNPs), obtained by a chemical method, creating a ternary intelligent delivery system for MTX molecules, based on the plasmonic properties of the AuNPs. Irradiation of the ternary system, with a laser wavelength tunable with the corresponding surface plasmon of AuNPs, causes local energy dissipation, producing the controlled release of the guest from CD cavities. Finally, cell viability was evaluated using MTS assays for β-CD/MTX and AuNPs + β-CD/MTX samples, with and without irradiation, against HeLa tumor cells. The irradiated sample of the ternary system AuNPs + β-CD/MTX produced a diminution in cell viability attributed to the photothermal release of MTX.

Keywords: Cyclodextrin, Delivery system, Gold nanoparticles, Inclusion compound, Irradiation, Laser, Methotrexate, Photothermal release


Gállego, Isaac, Manning, Brendan, Prades, Joan Daniel, Mir, Mònica, Samitier, Josep, Eritja, Ramon, (2017). DNA-origami-driven lithography for patterning on gold surfaces with sub-10 nm resolution Advanced Materials , 29, 1603233

Gállego, Isaac, Manning, Brendan, Prades, Joan Daniel, Mir, Mónica, Samitier, Josep, Eritja, Ramon, (2017). DNA-Origami-Aided Lithography for Sub-10 Nanometer Pattern Printing Proceedings Eurosensors 2017 , MDPI (Paris, France) 1, (4), 325

We report the first DNA-based origami technique that can print addressable patterns on surfaces with sub-10 nm resolution. Specifically, we have used a two-dimensional DNA origami as a template (DNA origami stamp) to transfer DNA with pre-programmed patterns (DNA ink) on gold surfaces. The DNA ink is composed of thiol-modified staple strands incorporated at specific positions of the DNA origami stamp to create patterns upon thiol-gold bond formation on the surface (DNA ink). The DNA pattern formed is composed of unique oligonucleotide sequences, each of which is individually addressable. As a proof-of-concept, we created a linear pattern of oligonucleotide-modified gold nanoparticles complementary to the DNA ink pattern. We have developed an in silico model to identify key elements in the formation of our DNA origami-driven lithography and nanoparticle patterning as well as simulate more complex nanoparticle patterns on surfaces.

Keywords: DNA nanotechnology, Lithography, Nanopatterning, Gold nanoparticles, Metasurfaces


Silva, N., Muñoz, C., Diaz-Marcos, J., Samitier, J., Yutronic, N., Kogan, M. J., Jara, P., (2016). In situ visualization of the local photothermal effect produced on α-cyclodextrin inclusion compound associated with gold nanoparticles Nanoscale Research Letters 11, 180

Evidence of guest migration in α-cyclodextrin-octylamine (α-CD-OA) inclusion compound (IC) generated via plasmonic heating of gold nanoparticles (AuNPs) has been studied. In this report, we demonstrate local effects generated by laser-mediated irradiation of a sample of AuNPs covered with inclusion compounds on surface-derivatized glass under liquid conditions by atomic force microscopy (AFM). Functionalized AuNPs on the glass and covered by the ICs were monitored by recording images by AFM during 5 h of irradiation, and images showed that after irradiation, a drastic decrease in the height of the AuNPs occurred. The absorption spectrum of the irradiated sample showed a hypsochromic shift from 542 to 536 nm, evidence suggesting that much of the population of nanoparticles lost all of the parts of the overlay of ICs due to the plasmonic heat generated by the irradiation. Mass spectrometry matrix-assisted laser desorption/ionization-time-of-flight (MALDI-TOF) performed on a sample containing a collection of drops obtained from the surface of the functionalized glass provided evidence that the irradiation lead to disintegration of the ICs and therefore exit of the octylamine molecule (the guest) from the cyclodextrin cavity (the matrix).

Keywords: Cyclodextrin inclusion compound, Gold nanoparticles, Guest migration, Plasmonic heating


Dols-Perez, A., Sisquella, X., Fumagalli, L., Gomila, G., (2013). Optical visualization of ultrathin mica flakes on semitransparent gold substrates Nanoscale Research Letters 8, (1), 1-5

We show that optical visualization of ultrathin mica flakes on metallic substrates is viable using semitransparent gold as substrates. This enables to easily localize mica flakes and rapidly estimate their thickness directly on gold substrates by conventional optical reflection microscopy. We experimentally demonstrate it by comparing optical images with atomic force microscopy images of mica flakes on semitransparent gold. Present results open the possibility for simple and rapid characterization of thin mica flakes as well as other thin sheets directly on metallic substrates.

Keywords: Atomic force, Conductive AFM, Gold substrates, Metallic substrate, Optical image, Optical reflection, Optical visualization, Ultrathin layers, Atomic force microscopy, Geometrical optics, Gold, Mica, Optical microscopy, Substrates


Gustavsson, J., Ginebra, M. P., Planell, J., Engel, E., (2012). Electrochemical microelectrodes for improved spatial and temporal characterization of aqueous environments around calcium phosphate cements Acta Biomaterialia 8, (1), 386-393

Calcium phosphate compounds can potentially influence cellular fate through ionic substitutions. However, to be able to turn such solution-mediated processes into successful directors of cellular response, a perfect understanding of the material-induced chemical reactions in situ is required. We therefore report on the application of home-made electrochemical microelectrodes, tested as pH and chloride sensors, for precise spatial and temporal characterization of different aqueous environments around calcium phosphate-based biomaterials prepared from α-tricalcium phosphate using clinically relevant liquid to powder ratios. The small size of the electrodes allowed for online measurements in traditionally inaccessible in vitro environments, such as the immediate material-liquid interface and the interior of curing bone cement. The kinetic data obtained has been compared to theoretical sorption models, confirming that the proposed setup can provide key information for improved understanding of the biochemical environment imposed by chemically reactive biomaterials.

Keywords: Calcium phosphate, Hydroxyapatite, Ion sorption, Iridium oxide, Sensors, Animals, Biocompatible Materials, Bone Cements, Calcium Phosphates, Cells, Cultured, Chlorides, Electrochemical Techniques, Gold, Hydrogen-Ion Concentration, Hydroxyapatites, Iridium, Materials Testing, Microelectrodes, Powders, Silver, Silver Compounds, Water


Toset, J., Gomila, G., (2010). Three-dimensional manipulation of gold nanoparticles with electro-enhanced capillary forces Applied Physics Letters , 96, (4), 043117

We demonstrate the possibility to manipulate 25 nm radius gold nanoparticles in the three spatial dimensions with an atomic force microscope with the use of electroenhanced capillary forces. We show that an enhanced water-bridge can be electrostatically induced between a conducting probe and a metallic nanoparticle by the application of a voltage pulse, which is able to exert a pulling capillary force on the nanoparticle strong enough to detach it from the substrate. The nanoparticle can then be moved, attached to the probe, and placed back to the desired location on the substrate simply by contacting it.

Keywords: Atomic force microscopy, Capillarity, Gold, Nanoparticles, Nanotechnology


Illa, X., Rodriguez-Trujillo, R., Ordeig, O., De Malsche, W., Homs-Corbera, A., Gardeniers, H., Desmet, G., Kutter, J. P., Samitier, J., Romano-Rodríguez, A., (2010). Simultaneous impedance and fluorescence detection of proteins in a cyclo olefin polymer chip containing a column with an ordered pillar array with integrated gold microelectrodes MicroTAS 2010 14th International Conference on Miniaturized Systems for Chemistry and Life Sciences , UoG (Gorningen, The Netherlands) 2, 1280-1282

In this work, we report the detection of proteins by means of simultaneous fluorescence and impedance measurements in a cyclo olefin polymer (COP) chip containing an ordered pillar array column, used for reversed-phase liquid chromatography, with integrated microband gold electrodes at the end of the channel.

Keywords: Cyclo olefin polymer, Gold microelectrodes, Impedance, Pillar array, Protein detection


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


Mir, M., Cameron, P. J., Zhong, X., Azzaroni, O., Alvarez, M., Knoll, W., (2009). Anti-fouling characteristics of surface-confined oligonucleotide strands bioconjugated on streptavidin platforms in the presence of nanomaterials Talanta , 78, (3), 1102-6

This work describes our studies on the molecular design of interfacial architectures suitable for DNA sensing which could resist non-specific binding of nanomaterials commonly used as labels for amplifying biorecognition events. We observed that the non-specific binding of bio-nanomaterials to surface-confined oligonucleotide strands is highly dependent on the characteristics of the interfacial architecture. Thiolated double stranded oligonucleotide arrays assembled on Au surfaces evidence significant fouling in the presence of nanoparticles (NPs) at the nanomolar level. The non-specific interaction between the oligonucleotide strands and the nanomaterials can be sensitively minimized by introducing streptavidin (SAv) as an underlayer conjugated to the DNA arrays. The role of the SAv layer was attributed to the significant hydrophilic repulsion between the SAv-modified surface and the nanomaterials in close proximity to the interface, thus conferring outstanding anti-fouling characteristics to the interfacial architecture. These results provide a simple and straightforward strategy to overcome the limitations introduced by the non-specific binding of labels to achieve reliable detection of DNA-based biorecognition events.

Keywords: DNA/ analysis, Gold, Nanostructures/ chemistry, Oligonucleotide Array Sequence Analysis/ instrumentation, Oligonucleotides/ chemistry, Streptavidin/ chemistry, Sulfhydryl Compounds


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