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.