A unique phenothiazine-based fluorescent probe using benzothiazolium as a reactivity regulator for the specific detection of hypochlorite in drinking water and living organisms

As a common disinfectant and an essential reactive oxygen species (ROS), hypochlorite (ClO^-) plays vital roles in both water treatment and cell metabolism, but its abnormal level can cause serious harm to human health. Therefore, quantifying ClO^- level in drinking water and living organisms is extremely significant. Herein, we decorated different cationic heterocycles on phenothiazine core to construct three fluorescent probes for ClO^-. According to the results, only benzothiazolium moiety reasonably adjusted the electron cloud density at sulfur atom of phenothiazine core for the specific oxidation with ClO^-, thus endowing the prepared probe PT-BT with a perfect selectivity for ClO^-. Meanwhile, PT-BT exhibited a low detection limit (38 nM) and a fast response (within 20 s) toward ClO^-. Furthermore, this probe was utilized to fabricate a ready-to-use test strip, which could quantitatively measure ClO^- level in real water samples by a portable smartphone sensing platform. Notably, PT-BT targeted mitochondria efficiently, and successfully visualized endogenous ClO^- in living cells and zebrafish larvae. Especially, PT-BT was able to monitor the dynamic change of ClO^- level in inflammatory mice. These results strongly manifested that probe PT-BT was a promising tool for detecting ClO^- in drinking water and living organisms.