COVALENTLY IMMOBILIZED ENZYMES ON BIOCOMPATIBLE POLYMERS FOR AMPEROMETRIC SENSOR APPLICATIONS

Glucose oxidase or choline oxidase were covalently immobilized on the surface of 2-hydroxyethyl and glycidyl methacrylate copolymer membrane s. The polymerization was induced by gamma irradiation at low temperat ure. The enzyme modified polymers were applied on Clark-type or platin um electrodes to form amperometric sensors based on the electrochemica l measurements of oxygen or hydrogen peroxide. Glucose and choline con tent in standard solutions were measured and linear calibration curves were determined. The sensors studied showed a response time of less t han 2 min and the observed linear ranges were increased with respect t o usual biosensors owing to the diffusion-limiting effects of the memb ranes used. The influence of the copolymer composition on the electroc hemical response and on the retained enzyme activity were explored for verifying the optimum analytical performance. The immobilized enzyme membranes stored in suitable buffers were very stable and showed a dec rease up to 20% in the electrode response after 3 months of constant u se.