Mitochondria-targeting phenothiazine-based ratiometric fluorescent probe for visual and rapid detection of hypochlorous acid in living cells and zebrafish

Hypochlorous acid (HClO) as a reactive oxygen species (ROS) plays an important role in many pathological and physiological processes. Abnormal concentrations of HClO in vivo have close contact with many diseases, including inflammatory diseases and cancer. Due to the measurement deviation caused by changes in external factors, a ratiometric fluorescent probe can effectively avoid this phenomenon. In this work, a ratiometric fluorescent probe PTB was synthesized based on phenothiazine for rapid and specific detection of HClO. PTB showed good selectivity, good biocompatibility, and a low detection limit (21.4 nM). Moreover, this ratiometric fluorescent nanoprobe was subsequently developed for visual on-site detection of HClO with the naked eyes under an ultraviolet lamp. In biology, PTB showed good mitochondrial targeting and was capable of rapidly detecting endogenous HClO within 10 s in living cells and in vivo, which makes it have broad application potential in the life sciences.