Jeffrey Schwartz

Cell attractive or non-attractive surface properties of polyurethane devices can be controlled by treating them with zirconium tetra(tert-butoxide). This gives reactive interfacial zirconium complex species that can be used subsequently to bond cell attractive peptides such as arg-gly-asp (RGD) or cell non-attractive organics such as polyethylene glycol (PEG) to the device surface. Control of the surface properties of the polyurethane occurs on the nanoscale, and does not compromise the physical properties of the polymer. Interfacial Zr complex formation occurs at N–H sites of the polyurethane; therefore surface loadings of the Zr complex depend on the spatial separation of these N–H groups in the polymer backbone. A complex loading of 110 ± 15 pmol cm^–2 is achieved on poly(hexamethylenehexylene)urethane, and 40 ± 10 pmol cm^{– 2} is bound on the medically relevant polyurethane, tecoflex®. About 25% and 10% of these polymer surfaces, respectively, can be covered by RGDvia the zirconium complex interface; because of its greater size, about 100% of both polymer surfaces is covered by PEG. The response of 3T3 fibroblasts to surface-treated and untreated tecoflex® is described.

Zirconium tetra(tert-butoxide) reacts with surface amide groups of polyamide nylon 6/6 to give (η²-amidate)zirconium complexes in high yield. These surface complexes react to bond the cell-adhesive peptide arginine-glycine-aspartic acid (RGD) to the polymer surface. A surface loading of 0.18 nmol/cm² of RGD is achieved, which is 20−1000 times higher than previously reported attainable on natural or synthetic polymers by other strategies. Approximately 40% of the nylon surface is covered by the RGD, which gives a surface that is both stable to hydrolysis and highly active for cell adhesion and spreading in vitro.