MnO2 in-situ coated upconversion nanosystem for turn-on fluorescence detection of hypoxanthine in aquatic products.

Hypoxanthine concentration is a potential indicator to evaluate the freshness in the early post-mortem of several aquatic products. Based on MnO2 in-situ coated upconversion nanoparticles (UCNPs) and xanthine oxidase (XOD), a novel sensor was conducted for the efficient, sensitive determination of hypoxanthine. In this strategy, upconversion fluorescence quenched by MnO2 would be restored by H2O2 and uric acid (UA), two products from the XOD-catalyzed reactions of hypoxanthine. Through pretreatment with short-time heating and alkylation by N-ethylmaleimide (NEM) to avoid potential interference from reducing substances in the food matrix, this method exhibited satisfactory selectivity. The fluorescence intensity of green emission Igreen was positively proportional to hypoxanthine concentration at a wide range of 0.5-50 mg/L with a detection limit of 0.14 mg/L. Moreover, this convenient method was employed to quantify the hypoxanthine in fish, shrimp, and shellfish samples, showing excellent potential for the application in quality control of aquatic products.