Immobilized biomolecules on plasma functionalized cellophane. I. Covalently attached alpha-chymotrypsin

Surface: morphology changes of hydrazine-RF-plasma-exposed cellophane surfa ces were monitored under 40 Hz and 13.56 MHz CW and pulsed discharge enviro nments and the immobilization of alpha-chymotrypsin onto plasma-modified su bstrates was studied. It has bran shown, using SEM and AFM techniques, that significantly different cellophane topographies are generated under differ ent frequency and pulsing parameter conditions. ESCA and ATR-FTIR analyses of plasma-modified surfaces indicated the presence of primary amide and pr imary amine Functionalities. It was found that the relative ratios of cryst alline vs amorphous zones of the nascent surface layers can also be control led by properly selected plasma parameters, including the duty cycles of pu lsed plasma environments. Enzyme immobilization reactions with alpha-chymot rypsin were accomplished both from oxygen-plasma-generated carbonyl and hyd razine-plasma-created primary amine functionalities by anchoring the biomol ecules tither directly to the cellophane surface or by involving spacer mol ecules. It was found with the cellulose substrates that fairly good enzyme activity was retained without the necessity of intercalated spacer chains. It appears that the ability of the cellulose substrate to swell in the aque ous environment allows sufficient freedom of mobility for the immobilized e nzyme to retain a significant part of its activity on the cellulose. Howeve r, the activities both of the free enzyme in the presence of cellophane, an d that of the immobilized enzyme molecules are significantly diminished in comparison to the activity of the free enzyme, as a result of the incorpora tion of these molecules into the swollen network. Potential applications of immobilized enzymes from cold-plasma-functionalized surfaces are discussed .