A novel lysosome-targeting fluorescent probe for intracellular HClO imaging and aqueous environment detection based on smartphone-assisted quantification.

Hypochlorous acid (HClO), a reactive oxygen species (ROS), regulates multiple physiological and pathological processes in humans. However, its excessive accumulation induces diseases such as inflammatory bowel disease, rheumatoid arthritis, cardiovascular diseases, and neurodegenerative diseases. Besides, HClO is employed for public disinfection in infectious disease outbreaks to block pathogen transmission, but its over-discharge causes water pollution, endangering aquatic organisms and triggering severe human respiratory and skin diseases. To clarify HClO's complex roles in environmental and biological systems, developing accurate detection methods is imperative. This study synthesized a novel naphthalene-derived fluorescent probe Z via acylation and substitution reactions, using 4-bromo-1,8-naphthalimide as the fluorophore, morpholine as the lysosome-targeting group, and dimethylthiocarbamoyl chloride as the recognition group. Probe Z exhibits prominent visualization advantages: upon HClO addition, it turns from pale yellow to fluorescent yellow under 365 nm UV light within 1 min, with a 13-fold fluorescence enhancement, high selectivity, high sensitivity, and a low detection limit of 0.52 nM. It can detect HClO in water samples and achieve fluorescent imaging of lysosomal HClO in cells. Notably, combined with the data processing function of smartphones, it enables reliable quantification of HClO, providing a new tool for exploring HClO's biological roles and on-site high-throughput visual detection.