by Keyword: Microscope

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Van Der Hofstadt, M., Hüttener, M., Juárez, A., Gomila, G., (2015). Nanoscale imaging of the growth and division of bacterial cells on planar substrates with the atomic force microscope Ultramicroscopy , 154, 29-36

Abstract With the use of the atomic force microscope (AFM), the Nanomicrobiology field has advanced drastically. Due to the complexity of imaging living bacterial processes in their natural growing environments, improvements have come to a standstill. Here we show the in situ nanoscale imaging of the growth and division of single bacterial cells on planar substrates with the atomic force microscope. To achieve this, we minimized the lateral shear forces responsible for the detachment of weakly adsorbed bacteria on planar substrates with the use of the so called dynamic jumping mode with very soft cantilever probes. With this approach, gentle imaging conditions can be maintained for long periods of time, enabling the continuous imaging of the bacterial cell growth and division, even on planar substrates. Present results offer the possibility to observe living processes of untrapped bacteria weakly attached to planar substrates.

Keywords: Atomic Force Microscope (AFM), Living cell imaging, Bacteria division, Gelatine immobilization, Dynamic jumping mode

Mir, Mònica , Tahirbegi, Islam Bogachan , Valle-Delgado, Juan José , Fernàndez-Busquets, X., Samitier, Josep , (2012). In vitro study of magnetite-amyloid β complex formation Nanomedicine: Nanotechnology, Biology, and Medicine , 8, (6), 974-980

Biogenic magnetite (Fe3O4) has been identified in human brain tissue. However, abnormal concentration of magnetite nanoparticles in the brain has been observed in different neurodegenerative pathologies. In the case of Alzheimer's disease (AD), these magnetic nanoparticles have been identified attached to the characteristic brain plaques, which are mainly formed by fibrils of amyloid β peptide (Aβ). However, few clues about the formation of the magnetite-Aβ complex have been reported. We have investigated the interaction between these important players in the AD with superconducting quantum interference, scanning electron microscope, surface plasmon resonance, and magnetic force microscopy. The results support the notion that the magnetite-Aβ complex is created before the synthesis of the magnetic nanoparticles, bringing a highly stable interaction of this couple.

Keywords: Alzheimer's disease, Biogenic magnetite, Amyloid β peptide (Aβ), Superconducting quantum interference, Scanning electron microscope, Surface plasmon resonance, Magnetic force microscopy

Caballero, D., Villanueva, G., Plaza, J. A., Mills, C. A., Samitier, J., Errachid, A., (2010). Sharp high-aspect-ratio AFM tips fabricated by a combination of deep reactive ion etching and focused ion beam techniques Journal of Nanoscience and Nanotechnology , 10, (1), 497-501

The shape and dimensions of an atomic force microscope tip are crucial factors to obtain high resolution images at the nanoscale. When measuring samples with narrow trenches, inclined sidewalls near 90 or nanoscaled structures, standard silicon atomic force microscopy (AFM) tips do not provide satisfactory results. We have combined deep reactive ion etching (DRIE) and focused ion beam (FIB) lithography techniques in order to produce probes with sharp rocket-shaped silicon AFM tips for high resolution imaging. The cantilevers were shaped and the bulk micromachining was performed using the same DRIE equipment. To improve the tip aspect ratio we used FIB nanolithography technique. The tips were tested on narrow silicon trenches and over biological samples showing a better resolution when compared with standard AFM tips, which enables nanocharacterization and nanometrology of high-aspect-ratio structures and nanoscaled biological elements to be completed, and provides an alternative to commercial high aspect ratio AFM tips.

Keywords: Atomic-Force Microscope, Carbon nanotube tips, Probes, Roughness, Cells, Microfabrication, Calibration, Surfaces

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