Optical Microscopy in the Nano-World

Scanning near-field optical microscopy (SNOM) is an optical microscopy whose resolution is not bound to the diffraction limit. It provides chemical information based upon spectral, polarization and/or fluorescence contrast images. Details as small as 20 nm can be recognized. Photophysical and photochemical effects can be studied with SNOM on a similar scale. This article reviews a good deal of the experimental and theoretical work on SNOM in Switzerland

Nanoscale Probing of Biocompatibility of Materials

After a brief introduction to the concept of biocompatibility of materials, scanning tunneling microscopy (STM) and atomic force microscopy (AFM) are discussed with respect to their application to biomaterial surfaces through practical examples: Titanium, polyurethane and gold surface functionalized with self-assembly monolayers

Effect of toluene extraction on Biomer™ surface: II. An atomic force microscopy study

The surface characterization of Biomer™ and extracted Biomer™ has been investigated using atomic force microscopy (AFM) in order to show the influence of extraction process on the morphology and local interactions which monitor surface properties at a molecular scale. The high viscoelasticity of these polymers provided by the soft segments makes AFM imaging in contact mode quite difficult, the scanning of the tip inducing artifacts on the surface. The rate, direction, and number of scans strongly influence this friction effect. The recording of force curves has shown that the extraction and conditions of drying can modify the interaction forces present at the polymer surface. Imaging of the extracted Biomer™ obtained with AFM in non-contact mode has revealed inclusion nodules embedded in an amorphous phase. This may be attributed to the migration at the surface of the non-eliminated poly(aminomethacrylate) additive

Atomic force microscopy under liquid: A comparative study of three different AC mode operations

The image contrast mechanism of three newly proposed AC mode operations under liquid in three different frequency ranges is presented. They all rely on a strong repulsive force to damp the cantilever and the tip still ‘touches’ the sample surface. A direct comparison of the three different modes of operation with the conventional DC mode technique using the same gold sample under isopropanol was conducted. It was found that all the three AC modes exerted a much smaller lateral force than the DC mode although the normal loads were of the same order of magnitude. The suitability of such techniques in imaging physisorbed systems on hard substrates (such as soft biological samples) and the prospect of a true non‐contact repulsive mode operation are discussed

Crystallographic properties and mechanical behaviour of titanium hydride layers grown on titanium implants

International audienceCommercially pure titanium for bone-anchored dental implants, subjected to a sand-blasting and acid-etching surface treatment, has been mechanically tested and analysed by scanning electron microscopy and transmission electron microscopy observations. A fcc titanium hydride layer grows on the polycrystalline titanium substrate with various epitaxial relationships, whose grains also show epitaxial relationships with each other. Indentations, flexion tests and dislocation analyses indicate that this hydride layer can be plastically deformed

Influence of surface treatments developed for oral implants on the physical and biological properties of titanium. (II) Adsorption isotherms and biological activity of immobilized fibronectin

The influence of titanium surface properties on in vitro adsorption isotherms of fibronectin, promotion of Staphylococcus aureus adhesion, and binding of a monoclonal antibody to the cell-binding domain of fibronectin was examined. Treatments producing different surface roughness were applied to a single side of commercially pure titanium coverslips, which was either mechanically polished (P), or polished and then acid attacked with H2SO4/HCl (PA), or sandblasted and then acid attacked (SLA), whereas the untreated side was blocked by an albumin coating layer. Incubation of the coverslips with concentrations of soluble 3H-labelled fibronectin increasing from 1 to 16 micrograms/ml led to the saturation of all surfaces with immobilized protein from 4 to 16 micrograms/ml. Promotion of S. aureus adhesion by fibronectin adsorbed on all surfaces and binding of the monoclonal antibody to its cell-binding domain was to some extent proportional to the amount of immobilized protein but also showed some minor differences between surfaces. More important material-related differences were observed when fibronectin adsorption isotherms were expressed as a function of the effective, roughness-corrected surface area, yielding amounts of immobilized fibronectin on the rough PA and SLA titanium surfaces which were 50% lower than those adsorbed on either smooth P or polymethylmethacrylate coverslips used as controls. In conclusion, surface treatments increasing the surface roughness of titanium do not increase, but may partly decrease in vitro adsorption of fibronectin. Despite adsorbing different amounts of fibronectin, both rough and smooth titanium surfaces promote normal expression of 2 major functional domains of this protein

Hydroxylation and crystallization of electropolished titanium surface

Surface properties and dissociative chemisorption of water on titanium-oxide surfaces are of particular interest for the biocompatibility of this material. Scanning force microscopy images of electropolished titanium samples and of thin films of titanium evaporated under vacuum show a similar topography with a grain size of 30 nm. Mass spectrometer thermal desorption spectroscopy displays two peaks for e/m = 18, at 380 and 520 K corresponding to adsorbed water molecules and hydroxyl groups, respectively. Auger spectra show the segregation toward the surface of chlorine from the metal-oxide interface upon heating at 720 K and of sulphur from the bulk after annealing at 950 K. The oxygen diffusion from the surface toward the bulk during the heating process induces a metallic behaviour of the surface layer which is revealed by tunneling spectroscopy: the semiconducting gap present in dI/dV curves for the air-exposed sample vanishes upon annealing. STM images of the annealed surface show the presence of tiny crystallites of a few nm in size