Construction of a novel xanthine biosensor using zinc oxide (ZnO) and the biotemplate method for detection of fish freshness

In the food industry, fish is a product that has a short shelf life, and xanthine has attracted significant attention as an indicator of the freshness of fish. In this study, we demonstrated a simple assay system containing zinc oxide (ZnO) and xanthine oxidase (XOD) for specific and quantitative detection of xanthine. ZnO nanomaterials have been successfully synthesized using a biotemplate method. The mechanism is based on the fluorescence quenching of ZnO via the electron transfer mechanism, which is caused by the hydrogen peroxide (H2O2) that is produced from the XOD-catalyzed oxidation of xanthine. By virtue of the specific response, the present assay allowed for the selective determination of xanthine in the range of 3.30 × 10−10–6.67 × 10−7 mol L−1 and 2.67 × 10−6–2.67 × 10−4 mol L−1 with a detection limit of 1.30 × 10−10 mol L−1. The proposed method was successfully applied to the determination of xanthine in real fish samples with satisfactory results.