Polyurethane support films: structure and cellular adhesion

It is desirable to examine the cytobiology of cell adhesion to the same materials which are contemplated for use in biomedical and biotechnological devices. It is also of fundamental interest to examine adhesion to substrates with properties which are likely to influence adhesion in controlled ways. In many of these applications the materials of choice are polyurethane elastomers due to their physical properties and resistance to biodegradation. Polyurethanes have a two phase microstructure consisting of hydrophilic hard segments and hydrophobic soft segment domains. Variations of both the chemistry and the morphology of these microdomains may be produced. It is well understood that the hydrophilic/hydrophobic nature of surfaces affects cellular adhesion and the adsorption of extracellular proteins. Since polyurethane microdomains have dimensions in the range of 10-100 nm, hence the size of proteins and cell-surface receptors, polyurethane microdomain structure could influence order at the cell-material interface. Polyurethanes may be prepared as thin films with excellent properties for use as specimen supports in High Voltage transmission Electron Microscopy (HVEM) at 1 MeV. This permits the imaging of the cytoskeleton and other internal features of whole mounts of adherent cells, rather than tedious thin sectioning required for conventional TEM. Subsequently the surface morphology of these preparations may be imaged with high resolution SEM. Finally, the polyurethane itself may be stained and imaged by either HVEM or high resolution SEM in order to relate polyurethane micro-morphology to cellular features.