PARAMETERS WHICH INFLUENCE THE OPTIMAL IMMOBILIZATION OF OXIDASE TYPEENZYMES ON METHACRYLATE COPOLYMERS AS DEMONSTRATED FOR AMPEROMETRIC BIOSENSORS

Optimisation of the covalent attachment of enzymes to copolymers of me thyl and glycidyl methacrylates is explored. The importance of ionic s trength and pH were shown to influence the immobilisation efficiency, as well as enzyme concentration and immobilisation time. It was seen t hat for the case of glucose oxidase, the protein immobilisation effici ency correlated with the isoelectric point, whereas the immobilised en zyme activity, measured in terms of an amperometric response to glucos e correlated with an immobilisation pH of maximum enzyme activity. Con ditions for the maximum reactivity of the glycidyl group were also con sidered but found not to be the major determinant of an optimum immobi lised enzyme. The conditions were evaluated for five oxidase type enzy mes: glucose oxidase, lactate tyrosinase (polyphenol oxidase), cholest erol oxidase and alcohol oxidase in terms of their immobilisation effi ciency. The immobilisation process has also been shown to stabilise th e enzyme with respect to activity loss with time of storage, especiall y in the case of lactate oxidase.