Immobilization of glucose oxidase by acrylonitrile copolymer coated silica supports

Abstract

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 S AN-MA, S AN-HEMA, S AN-AAc(HMDA) and S PAN. The carboxylic groups of S AN-AAc support were activated with N, N′-dicyclohexylcarbodiimide – S AN-AAc(CDI), for covalent immobilization of glucose oxidase. Direct covalent immobilization was achieved on S AN-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 S AN-VP, S AN-VI and S AN-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 S AN-HEMA, S PAN and S AN-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. S PAN immobilized system showed the highest thermal stability at 60 °C (78% residual activity at the fifth hour), followed by GOD immobilized on S AN-HEMA and S AN-DCPMI (72 and 70%). The most stable for 50 days storage time is GOD covalently immobilized on S PAN (80% residual activity) followed by GOD immobilized on S AN-HEMA (73%).