Disposable amperometric biosensors based on xanthine oxidase immobilized in the Prussian blue modified screen-printed three-electrode system

The screen-printed three-electrode system was applied to fabricate a new type of disposable amperometric xanthine oxidase biosensor. Carbon-working, carbon-counter and Ag/AgCl reference electrodes were all manually printed on the polyethylene terephthalate substrate forming the screen-printed three-electrode system by the conventional screen-printing process. As a mediator, Prussian blue could not only catalyze the electrochemical reduction of hydrogen peroxide produced from the enzyme reaction, but also keep the favorable potential around 0 V. The optimum operational conditions, including pH, potential and temperature, were investigated. The sensitivities of xanthine and hypoxanthine detections were 13.83 mA/M and 25.56 mA/M, respectively. A linear relationship was obtained in the concentration range between 0.10 mu M and 4.98 mu M for xanthine and between 0.50 mu M and 3.98 mu M for hypoxanthine. The small Michaelis-menten constant value of the xanthine oxidase biosensor was calculated to be 3.90 mu M. The results indicate that the fabricated xanthine oxidase biosensor is effective and sensitive for the detection of xanthine and hypoxanthine.