Visualizing ClO^- fluctuations in drug-induced liver injury and bacterium via a robust ratiometric fluorescent probe

As a type of reactive oxygen species, hypochlorous acid (ClO^-) plays an important role in sterilization, disinfection and protection in organisms. However, excessive production of ClO^- is closely related to various diseases. In this work, we have designed a robust ratiometric fluorescent probe, RDB-ClO, using the excited-state intramolecular proton transfer (ESIPT) strategy. RDB-ClO was achieved by modifying 2-(2-(benzo[d]thiazol-2-yl)-6-(diethylamino)-3-oxo-3H-xanthen-9-yl) benzoic acid (RDB-OH) with a 1-naphthoyl chloride group, specifically for the sensitive detection of ClO^-. In the presence of ClO^-, RDB-ClO demonstrated relatively good performance, showing swift response time (35 s), low detection limit of 5.1 nM and high selectivity towards ClO^-. Notably, the convenience and accessibility detection of ClO^- has been implemented using test strip and agarose probe. RDB-ClO effectively tracked both endogenous and exogenous ClO^- in HeLa cells, HepG2 cells and zebrafish. Additionally, it is successfully applied to detect changes of exogenous ClO^- content in E. coli. and acetaminophen (APAP)-induced liver injury in mice. The development of RDB-ClO represents a promising molecular tool for studying the pathogenesis of DILI and biotransformation of ClO^- in bacteria.