Surface functionalization of degradable polymers by covalent grafting.

With a new non-destructive and solvent-free photografting technique, N-vinylpyrrolidone was covalently grafted onto the surfaces of degradable polymers; poly(l-lactide), poly(epsilon-caprolactone), poly(lactide-co-glycolide), and poly(trimethylene carbonate). The modified surfaces were characterized by XPS, ATR-FTIR, SEM, and cell growth tests. The wettability was markedly improved, as static contact angles changed from about 80 degrees for the pristine substrates to around 30 degrees after 30min of grafting. Well-defined surface topographies, such as micro-patterns, are preserved in the process since the graft layers are thin. The biological response, measured as cytotoxicity, showed that the modified films provide good substrates, comparable with optimized cell culture plastics, for the adhesion and proliferation of normal human keratinocytes and skin fibroblasts.