Surface functionalization and biomolecule immobilization using plasma-generated free radicals on polypropylene

In this study are presented evidences for the functionalization of polypropylene surfaces accomplished in a sequential process: argon- or oxygen-plasma enhanced generation of free radical sites on polypropylene surfaces was followed by "in situ" gas phase derivatization in the absence of plasma using ethylene diamine, or propylene diamine; and an "in situ", gas phase derivatization using oxallyl chloride or "ex situ" derivatization in the presence of glutaraldehyde. The free radicals' presence on the plasma-exposed polypropylene surfaces was confirmed using "in situ" sulfur dioxide or nitric oxide labeling techniques. It was shown that the free radical sites readily react under "in situ" conditions with the stable chain-precursor components and generate the desired spacer-chain molecules revealed by ESCA analysis. Functionalized polypropylene substrates were used for immobilization of alpha-chymotrypsin in the presence of spacer-chain molecules. The activity of the immobilized alpha-chymotrypsin was found to be comparable to the activity of the free enzyme when the spacer molecules have been used.