Colorimetric detection of hypoxanthine for shrimp freshness monitoring using Hemin@BSA@ZIF-8 nanostructure.

A colorimetric platform was developed for hypoxanthine (HX) detection based on a biomimetic nanozyme, Hemin@BSA@ZIF-8, which was fabricated by conjugating hemin with bovine serum albumin (BSA) to enhance its stability, followed by encapsulation within a porous zeolitic imidazolate framework-8 (ZIF-8) structure. This hierarchical structure leveraged the synergistic effects resulting from the Hemin@BSA conjugation and ZIF-8’s porous confinement, yielding good catalytic performance. The morphology, elemental composition, and surface functional groups of Hemin@BSA@ZIF-8 were systematically characterized. HX was specifically oxidized by xanthine oxidase to generate an H2O2 intermediate, which subsequently catalyzed the oxidation of the 3,3’,5,5’-tetramethylbenzidine (TMB) to a blue product (oxidized TMB, TMB− ox) by the Hemin@BSA@ZIF-8 complex. Under optimal conditions, HX was selectively and sensitively detected within a range 0-200 µM, with a detection limit of 17.05 µM. The proposed method was successfully applied to monitor the freshness of shrimp stored at 4 °C and 30 °C for varying durations. This work provides a robust, stable, and readily implementable strategy for food safety and environmental monitoring.