Modulating the biocompatibility of polymer surfaces with poly(ethylene glycol): Effect of fibronectin

A novel approach described earlier for improving polymer substratum biocomp atibility(1) is further elucidated. Polysulfone (PSf) spin-coating films we re modified by covalent end-on grafting of hydrophilic and sterically deman ding photo-reactive poly(ethylene glycol) (PEG) conjugates (ABMPEG; 10 kDa) . The degree of grafting density was varied systematically, yielding a wide spectrum of attained surface characteristics monitored by air-water contac t angles (captive bubble method). Fibronectin (FN) adsorption was studied b y in situ ellipsometry and found to decrease monotonically as ABMPEG grafti ng density increased. The adhesive interaction of human skin fibroblasts wi th these substrata and, in particular, the effect of FN precoating were inv estigated in detail. A clear optimum of cell-substratum interactions was fo und for mildly modified substrata, employing well established microscopic a nd immunofluorescence techniques, namely the monitoring of cell adhesion an d spreading, overall cell morphology, organization of FN receptors, and foc al adhesions as well as FN matrix formation. The results suggest that cell interactions with hydrophobic polymer substrata are enhanced considerably w hen modified with hydrophilic and sterically demanding PEG moieties at a lo w surface coverage due to enhanced biologic activity of adsorbed and interc alated adhesive proteins such as FN. (C) 2000 John Wiley & Sons, Inc.