Fabrication of an Amperometric Xanthine Biosensor Based on Polyvinylchloride Membrane

A method is described for fabrication of an amperometric xanthine biosensor based on polyvinylchloride (PVC) membrane bound xanthine oxidase (XOD). The membrane bound enzyme oxidizes xanthine into uric acid and H2O2, which is split into 2H++O2+2e- at high potential (0.4V) and measured as current (mA).Sensor showed optimum response within 30 s, at pH 7.0 and 35C. A linear relationship was observed between current and xanthine concentration ranging from 0.025 to 0.4 × 10-6 M, Km for xanthine and Imax were 0.45 × 10-6 M and 0.002 mA, respectively. Minimum detection limit of the biosensor was 2.5 × 10-8 M. Biosensor was utilized for determination of xanthine in fish meat cow and buffalos milk. Biosensor was used 100 times over a period of 45 days with only 30% loss of initial activity, when stored at 4C. PRACTICAL APPLICATIONS Evaluation of fish meat freshness is of great significance in food industries for the quality control of fish products. After the death of a fish, xanthine is a major metabolite in the degradation of adenosine triphosphate in the fish meat. Thus, xanthine attracts much attention as an indicator for estimating fish freshness. Moreover, the content of xanthine in human body fluids can also provide useful index for certain pathologic state, especially for xanthinuria.