A Novel ESIPT-Based Probe for Sensitive Detection and Bioimaging of Hypochlorous Acid.

Hypochlorous acid (HOCl), a key reactive oxygen species in the innate immune system, is closely implicated in various inflammatory diseases and tissue injuries when its concentration becomes dysregulated. To enable highly selective and sensitive detection and imaging of HOCl, we developed a novel HOCl probe BCPT, engineered on an excited-state intramolecular proton transfer (ESIPT) fluorophore platform. BCPT is constructed by conjugating a 4-pyridineacetonitrile unit to a 2-(2′-hydroxyphenyl)benzothiazole (HBT) core, with its phenolic hydroxyl group protected by a highly specific dimethylthiocarbamate moiety. This design confers a significant dual-fluorescence enhancement upon reaction with HOCl, featuring simultaneous turn-on emissions at 452 nm (enol form) and 580 nm (keto form). The keto emission exhibits a large Stokes shift of 180 nm, effectively mitigating self-absorption and inner-filter effects. BCPT demonstrates excellent selectivity, high sensitivity (detection limit: 0.02 µM), and a rapid fluorescence response (12 s). We successfully applied the probe for visualizing elevated HOCl levels in liver tissue sections from acetaminophen (APAP)-induced injury models, highlighting its potential as a detection tool for drug-induced liver injury (DILI).