The preparation of amperometric xanthine sensors based on multilayer thin films containing xanthine oxidase

An amperometric xanthine biosensor was prepared by immobilizing xanthine oxidase (XOx) on the surface of a platinum (Pt) disk electrode. The Pt electrode was first covered with a polyelectrolyte multilayer (PEM) film composed of poly(allylamine hydrochloride) (PAH) and poly(vinyl sulfate) (PVS) to block the Pt surface from the access of uric acid, a reaction product of the XOx-catalyzed oxidation reaction of xanthine, because uric acid can be electrochemically oxidized on the Pt electrode to induce interference. The PEM film-covered Pt electrode was further modified with a XOx-containing multilayer film composed of XOx and poly(dimethyldiallylammonium chloride) (PDDA). The xanthine biosensors thus prepared can be used successfully for detecting xanthine in the concentration range of 3–300 μM. The output current of the sensors depended on the number of the XOx/PDDA layers in the film. The PAH/PVS layer was effective to eliminate the uric acid interference.