EFFECT OF ENZYME RATIO AND ENZYME LOADING ON THE PERFORMANCE OF A BIENZYMATIC ELECTROCHEMICAL PHOSPHATE BIOSENSOR

A membrane-bound bienzyme system involving purine nucleoside phosphorylase and xanthine oxidase for the design of an electrochemical biosensor for phosphate detection was studied. The effects on the performance of the biosensor of both the ratio of enzyme activities and the absolute activities in the enzyme loading solution were determined. Optimization of these parameters enabled the linear dynamic range and sensitivity to be improved. The relationship between sensitivity and immobilized activity was also investigated with the sensor equipped with xanthine oxidase alone. The resulting characteristics of the biosensor were compared with those obtained with either glucose oxidase or choline oxidase bound to the membrane.