A Colorimetric Fluorescent Probe Based on Benzothiazole for Highly Sensitive Detection of Tryptamine and Food Freshness

Tryptamine, as an important indole-based biogenic amine, is widely present in food and biological organisms. Its excessive accumulation is one of the key factors leading to food poisoning and health risks. Therefore, developing efficient and specific tryptamine detection methods is of great significance for food safety monitoring. In this study, based on the intramolecular charge transfer (ICT) mechanism, a novel ratio-type fluorescent probe NR-1 was designed and synthesized with a benzoyl ester as a specific recognition group. When reacting with tryptamine, the probe showed a ratio-type fluorescence response, with fluorescence weakening at 378 nm and significantly enhancing at 472 nm. The probe showed good selectivity and detection sensitivity for tryptamine, with a detection limit (3σ) of 0.26 μmol/L. Further, the probe NR-1 was loaded onto a cotton swab carrier and combined with smartphone fluorescence imaging to achieve real-time and visual monitoring of tryptamine release in shrimp, chicken wings, mangoes and other foods during storage, and a quantitative relationship between fluorescence signals and storage time was thus established. This method provided a reliable new strategy for in-situ and portable detection of food freshness.