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.