A water-soluble phenothiazine-based fluorescent probe for selective detection and bioimaging of hypochlorite

A hydrophilic phenothiazine-based fluorescent probe (PTZMN) was developed for the selective and sensitive detection of hypochlorite (ClO^-) in pure water. Upon ClO^- stimulation, PTZMN exhibited a distinct colorimetric shift and a "turn-on" fluorescence response at 496 nm, with a low detection limit of 5.2 × 10^-7 mol/L and excellent linearity (R² = 0.9956) within the 0-60 μL range. ESI-MS, ¹H NMR, and DFT studies confirmed that ClO^- induces oxidative cleavage of the imine (C=N) bond, disrupting intramolecular charge transfer process (ICT). The probe showed high selectivity and strong anti-interference capability, and was successfully applied to ClO^- detection in disinfectants and water samples, as well as on test strips for naked-eye colorimetric detection and fluorescence detection (LOD < 10^-5 mol/L). Moreover, PTZMN was successfully applied to high-resolution fluorescence imaging in live HeLa cells and zebrafish embryos, with no observable toxicity. These findings highlight PTZMN's potential as a powerful platform for environmental analysis, portable detection and biological redox imaging.