Retention of enzyme by electropolymerized film: a new approach in developing a hypoxanthine biosensor

An amperometric biosensor for hypoxanthine was constructed by forming a layer of crosslinked xanthine oxidase on a platinum electrode, followed by electropolymerization of a submonolayer film of resorcinol and para-diaminobenzene. The fabricated electrodes were evaluated for speed of response, sensitivity, and reusability. Optimal performance was obtained with enzyme-based electrodes sparsely covered with film which was formed by electropolymerization in less than 6 min. The resulting electrodes exhibited linear response to hypoxanthine in the. range 5-300 microM with a response time of 2 min. Application of the biosensor in monitoring hypoxanthine content of fish extracts yielded results which agreed well with spectrophotometric assays using soluble xanthine oxidase. The biosensor was stable for 60 days when stored at 4 degrees C in phosphate buffer and it could be used continuously for 6 h with over 50 assays.