Surface functionalization via in situ interaction of plasma-generated free radicals with stable precursor-molecules on cellulose

The surface functionalization process was accomplished in a consecutive 3 step process including: (1) Argon- and oxygen-plasma enhanced generation of free radical sites on cellophane surfaces; (2) “In situ” gas phase derivatization in the absence of plasma using hydrazine, ethylene diamine, or propylene diamine; (3) Second “in situ”, gas phase derivatization in the absence of plasma using oxallyl chloride or “ex situ” derivatization in the presence of glutaraldehyde. The presence of free radical sites on the plasma exposed cellophane surfaces was demonstrated using “in situ” sulfur dioxide and 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. ESCA, ATR-FTIR analysis and dying techniques were used to monitor the cellophane surface changes. A factorial design was used for selecting the optimal plasma parameters. Functionalized cellophane substrates were used for immobilization of α-chymotrypsin in the presence of spacer-chain molecules. The activity of the immobilized α-chymotrypsin was found to be lower in comparison to the activity of the free enzyme and the presence of virgin cellophane in the free enzyme solution also reduced significantly the activity of the enzyme. It is suggested that the swollen state of the cellophane plays a significant role in the decrease of the immobilized enzyme activity.