The clinically important vancomycin antibiotic inhibits the growth of pathogens such as Staphylococcus aureus by blocking cell wall synthesis through specific recognition of nascent peptidoglycan terminating in D-Ala-D-Ala. Here, we demonstrate the ability of single-molecule atomic force microscopy with antibiotic-modified tips to measure the specific binding forces of vancomycin and to map individual ligands on living bacteria. The single-molecule approach presented here provides new opportunities for understanding the binding mechanisms of antibiotics and for exploring the architecture of bacterial cell walls.

The effects of tightly focused, higher-order laser beams on the photoinduced molecular migration and surface deformations in azobenzene polymer films are investigated. We demonstrate that the surface relief is principally triggered by longitudinal fields, i.e., electric fields polarized along the optical axis of the focused beam. Our findings can be explained by the translational diffusion of isomerized chromophores when the constraining effect of the polymer-air interface is considered.

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The local perturbation of a diffraction-limited spot by a nanometer sized gold tip in a popular apertureless scanning near-field optical microscopy (ASNOM) configuration is reproduced through topography changes in a photoresponsive polymer. Our method relies on the observation of the photochemical migration of azobenzene molecules grafted to a polymer placed beneath the tip. A local molecular displacement has been shown to be activated by a gold tip as a consequence of the lateral surface charge density present at the edges of the tip's end, resulting from a strong near-field depolarization predicted by theory.

In the past years, atomic force microscopy (AFM) has offered novel possibilities for exploring the nanoscale surface properties of fungal cells. For the first time, AFM imaging enables investigators to visualize fine surface structures, such as rodlets, directly on native hydrated cells. Moreover, real-time imaging can be used to follow cell surface dynamics during cell growth and to monitor the effect of molecules such as enzymes and drugs. In fact, AFM is much more than a microscope in that when used in the force spectroscopy mode, it allows measurement of physicochemical properties such as surface energy and surface charge, to probe the elasticity of cell wall components and macromolecules, and to analyse the force and localization of molecular recognition events.

According to near field theory, when irradiated in specific conditions, a metallic tip can give rise to a field enhancement (FE) at its apex and then be used as a nanosource to illuminate a photosensitive sample. In the case of polymers containing azobenzene groups, this exaltation process can lead to a displacement and rearrangement of chromophores in the vicinity of the tip. Contact mode atomic force microscopy (AFM) has been chosen to observe the photoinduced pattern. The use of semiconductor and dielectric probes as well as a normal incidence illumination mode, which minimizes the field enhancement (FE), still induces nanopatterns whatever the polarization state of the actinic light. In these conditions, the adhesion forces appear to be mainly responsible for the nanopattern process. The residual solvent contained in the bulk acts as a plasticizer. The height of the photoinduced nanoprotrusion can be modulated by adjusting the vertical deflection of the tip. Photoinduced nanopatterning obtained in AFM contact mode appears as a new and easy technique of high-resolution nanophotolithography.

Ⅺ Plasma enhanced chemical vapor deposition has been tested for the formation of hydrophobic perfluorinated coating on the surface of hydrophilic poly(2-hydroxyethyl methacrylate-co-methyl methacrylate) [poly(HEMA-co-MMA)] substrates, used for the fabrication of intraocular lenses (IOLs). The properties of the dry and hydrated surface modified by two plasma techniques, Radiofrequency (RF) and Microwave (MW), were investigated in parallel by contact angle measurements in the dry and hydrated state, X-ray photoelectron spectroscopy, and atomic force microscopy. The coating stability and hydrophobicity were challenged by swelling and sterilizing the samples in water. Investigation of the optical performances of the modified samples was performed by ultraviolet spectroscopy and diopter measurements. Since materials with biomedical application are considered, the performances of their surface in contact with lens epithelial cells were tested at in vitro conditions, and repulsion was not found to be enhanced upon modification. Generally, the results showed poor stability of the coating and bring in question its covalent grafting to the surface.

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