Cerium oxide-based hypoxanthine biosensor for Fish spoilage monitoring

Food monitoring has become an essential need for assessing food quality and safety. However, most currently available methods for food monitoring are not portable which limit their applicability in the field. Herein, we report a novel portable all-in-one nanoenzyme-based biosensor for fish freshness monitoring that measures the release of hypoxanthine (HX), a product of nucleotide degradation in meat and fish. The biosensor uses ceria nanoparticles (CeNPs), an enzyme mimetic material with a plurality function, as peroxidase mimetic, redox amplifier and chromogenic indicator, along with xanthine oxidase (XOD) to quantify the product of the HX oxidation. The biosensor is fabricated by immobilizing both the XOD and the CeNPs onto the surface of silanized paper, producing a reagentless platform for HX detection. In this configuration, the CeNPs replace the peroxidase enzyme and the soluble dye in conventional assays for HX detection, reducing the number of reagents, decreasing cost and increasing portability. A detection limit of 15 mu M and 89 mu M with a linear range up to 800 and 597 mu M for the CeNPs based solution and the paper biosensor, respectively were obtained. The results confirm the potential of this technology as an inexpensive approach to monitor HX levels in contrast to the conventional multistep enzyme-based solution assays. This study may advance the development of next generation portable biosensing technologies for food safety monitoring.