by Keyword: Nanoscale

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Fumagalli, Laura, Esteban-Ferrer, Daniel, Cuervo, Ana, Carrascosa, Jose L., Gomila, Gabriel, (2012). Label-free identification of single dielectric nanoparticles and viruses with ultraweak polarization forces Nature Materials Nature Publishing Group 11, (9), 743-826

Label-free detection of the material composition of nanoparticles could be enabled by the quantification of the nanoparticles’ inherent dielectric response to an applied electric field. However, the sensitivity of dielectric nanoscale objects to geometric and non-local effects makes the dielectric response extremely weak. Here we show that electrostatic force microscopy with sub-piconewton resolution can resolve the dielectric constants of single dielectric nanoparticles without the need for any reference material, as well as distinguish nanoparticles that have an identical surface but different inner composition. We unambiguously identified unlabelled ~10unm nanoparticles of similar morphology but different low-polarizable materials, and discriminated empty from DNA-containing virus capsids. Our approach should make the in situ characterization of nanoscale dielectrics and biological macromolecules possible.

Keywords: Biological materials, Nanoscale materials, Characterisation and analytical techniques, Computation, modelling and theory

van Zanten, T. S., Garcia-Parajo, M. F., (2012). Super-resolution near-field optical microscopy Comprehensive Biophysics (ed. Egelman, E. H.), Elsevier (Desdren, Germany) Volume 2: Biophysical Techniques for Characterization of Cells, 144-164

Near-field optical microscopy is a technique not limited by the laws of diffraction that enables simultaneous high-resolution fluorescence and topographic measurements at the nanometer scale. This chapter highlights the intrinsic advantages of near-field optics in the study of cellular structures. The first part of the chapter lays the foundations of the near-field concept and technical implementation of near-field scanning optical microscopy (NSOM), whereas the second part of the chapter focuses on applications of NSOM to the study of model membranes and cellular structures on the plasma membrane. The last part of the chapter discusses further directions of near-field optics, including optical antennas and fluorescence correlation spectroscopy approaches in the near-field regime.

Keywords: Biological membranes, Cell membrane nanoscale compartmentalization, Cellular nanodomains, Fluorescence correlation spectroscopy in reduced volumes, Immunoreceptor imaging, Lipid rafts, Near-field scanning optical microscopy, Optical nano-antennas, Shear force imaging, Single molecule detection, Super-resolution microscopy

Estevez, M., Fernandez-Ulibarri, I., Martinez, E., Egea, G., Samitier, J., (2010). Changes in the internal organization of the cell by microstructured substrates Soft Matter 6, (3), 582-590

Surface features at the micro and nanometre scale have been shown to influence and even determine cell behaviour and cytoskeleton organization through direct mechanotransductive pathways. Much less is known about the function and internal distribution of organelles of cells grown on topographically modified surfaces. In this study, the nanoimprint lithography technique was used to manufacture poly(methyl methacrylate) (PMMA) sheets with a variety of features in the micrometre size range. Normal rat kidney (NRK) fibroblasts were cultured on these substrates and immunofluorescence staining assays were performed to visualize cell adhesion, the organization of the cytoskeleton and the morphology and subcellular positioning of the Golgi complex. The results show that different topographic features at the micrometric scale induce different rearrangements of the cell cytoskeleton, which in turn alter the positioning and morphology of the Golgi complex. Microposts and microholes alter the mechanical stability of the Golgi complex by modifying the actin cytoskeleton organization leading to the compaction of the organelle. These findings prove that physically modified surfaces are a valuable tool with which to study the dynamics of cell cytoskeleton organization and its subsequent repercussion on internal cell organization and associated function.

Keywords: Actin stress fibers, Golgi-complex, Focal adhesions, Cytoskeletal organization, Osteoblast adhesion, Mammalian-cells, Micron-scale, Nanoscale, Dynamics, Rho