A fluorescence probe for monitoring toxic hypochlorous acid in biosystems and environmental waters with a broad pH adaptation

Hypochlorous acid (HOCl) is commonly utilized in various daily applications. As a toxic reactive oxygen species (ROS) that generated from the industrial and pharmaceutical aspects, it plays a critical role in the mass cycle of environmental system and various biological processes. Understanding the complicated roles of HOCl in environment and biosystems requires the development of precise and efficient detection methods. Thus, in this work, a novel fluorescent probe, MQ-ClO, has been designed to detect hypochlorous acid by utilizing hypochlorous acid-triggered oxidative intramolecular cyclization. This probe exhibits rapid and sensitive response, with a detection limit as low as 35 nM. More importantly, the probe is capable of functioning under highly acidic or basic conditions, exhibiting a wide pH range adaptability from pH 2-11. Furthermore, MQ-ClO has been effectively used to detect HOCl in real water samples. Besides, the low toxicity of MQ-ClO enables its practical application in monitoring endogenous/exogenous HOCl levels in living cells as well as zebrafish.