A Phenazine-Based Fluorescent Probe with Imidazoline-2-Thione for Rapid and Selective Detection of HOCl in Living...

Hypochlorous acid (HOCl) is a reactive oxygen species involved in both host defense and pathological processes, making its detection in biological systems of critical importance. Herein, we report the design and synthesis of a phenazine-based fluorescent probe, PNN, incorporating an imidazoline-2-thione recognition unit for selective HOCl detection. PNN exhibits a distinct "turn-on" fluorescence at 555 nm upon reaction with HOCl, with an enhancement of approximately 108-fold, surpassing that of previously reported thione-based probes, which typically emit in the 445-505 nm range. PNN also shows high sensitivity, rapid response, and excellent selectivity over other reactive oxygen and nitrogen species. Furthermore, PNN displays negligible cytotoxicity in HeLa cells and enables concentration-dependent visualization of exogenous HOCl in living cells. These features position PNN as a robust and reliable tool for monitoring HOCl in complex biological environments, providing a versatile platform for investigating its physiological and pathological functions.