Protein-resistant polyurethane prepared by surface-initiated atom transfer radical graft polymerization (ATRgP) of water-soluble polymers: Effects of main chain and side chain lengths of grafts

Water-soluble poly(oligo(ethylene glycol) methacrylate) (poly(OEGMA)) with various main chain and side chain lengths were grafted to polyurethane (PU) surface by surface-initiated atom transfer radical graft polymerization (s-ATRgP). The polymer main chain length was varied by varying the molar ratio of monomer to free initiator in solution (typically 5:1, 50:1, 100:1). Three different side chain lengths were obtained using different OEGMA monomers (MW 300, 475, 1100 g/mol). Water contact angle and X-ray photoelectron spectroscopy (XPS) were used to characterize the modified PU surfaces. The respective effects of poly(OEGMA) main chain and side chain lengths on fibrinogen (Fg) and lysozyme (Lys) adsorption were investigated in single protein systems at room temperature in TBS, pH 7.4. The poly(OEGMA)-grafted PU surfaces were found to be highly protein-resistant, with reductions of Fg and Lys adsorption in the range of 84-98% and 67-91%, respectively, compared to the unmodified PU surface. The adsorption of both proteins decreased with increasing poly(OEGMA) main chain length for a given side chain length (number of EO units). For a given main chain length, the Fg adsorption level did not change significantly with increasing side chain length. However, Lys adsorption increased with increasing side chain length, possibly due to decreasing graft density as monomer size and footprint on the surface increase. Adsorption resistance was generally greater for the bigger protein.