Immobilization of glucose oxidase by acrylonitrile copolymer coated silica supports

New polymer/silica gel hybrid supports were prepared by coating high surface area of silica gel with eight different copolymers of acrylonitrile: acrylonitrile-vinyl pyridine, acrylonitrile-vinylimidazole, acrylonitrile-N,N-dimethylaminoethylmethacrylate, acrylonitrile-acrylic acid, acrylonitrile-2,6-dichlorphenilmaleimide, acrylonitrile-maleic anhydride, acrylonitrile-hydroxyethylmethacrylate and acrylonitrile-methylmethacrylate and Na-vinylsulfonate. Glucose oxidase was covalently immobilized on six types of acrylonitrile copolymer/silica gel hybrid supports. Glutaraldehyde was used as coupling agent between the support treated with hexamethylenediamine (spacer) and the enzyme in the case of SAN-MA, SAN-HEMA, SAN-AAc(HMDA) and SPAN. The carboxylic groups of SAN-AAc support were activated with N,N′-dicyclohexylcarbodiimide – SAN-AAc(CDI), for covalent immobilization of glucose oxidase. Direct covalent immobilization was achieved on SAN-DCPMI via the reactive Cl-ions of the support and the ɛ-amino group of lysine residue of the enzyme. Glucose oxidase was immobilized on SAN-VP, SAN-VI and SAN-DMAEM by adsorption via ionic bonding. The greatest amount of bound protein and relative enzyme activity was presented among the covalently immobilized glucose oxidase on SAN-HEMA, SPAN and SAN-MA. The relative activity of the immobilized glucose oxidase via ionic bonding is also high since no conformation changes in enzyme molecules could be noticed. SPAN immobilized system showed the highest thermal stability at 60 °C (78% residual activity at the fifth hour), followed by GOD immobilized on SAN-HEMA and SAN-DCPMI (72 and 70%). The most stable for 50 days storage time is GOD covalently immobilized on SPAN (80% residual activity) followed by GOD immobilized on SAN-HEMA (73%).