An intelligent colorimetric paper-based hypoxanthine biosensor enabled by smartphone and dual-enzyme system for efficient shrimp freshness monitoring

Monitoring the freshness of aquatic foods is essential to ensure their quality and safety. Hypoxanthine (Hx), degraded from adenosine triphosphate, emerges as an early indicator during shrimp spoilage. There is no paper-based biosensor to monitor shrimp freshness via Hx detection. This study reports for the first time a colorimetric paper-based biosensor enabled by smartphone and a dual-enzyme system. NiPt nanoparticles (diameter of 2.45 ± 0.52 nm) was developed as peroxidase-mimic nanozyme and combined with xanthine oxidase as a dual-enzyme system, and then fabricated with chitosan-modified filter paper as test strip, assisted by smartphone for intelligent analysis. Linear detection range of 18.75 to 600 μM and limit of detection as 9.67 μM were obtained. During real-world applications, the biosensor realized high accuracy, good robustness against interference, and economic viability. This study provides reference for designing intelligent paper-based biosensor for Hx in shrimps as well as other targets in the food chain.