Engineering a swich-on fluorescent probe for the visual detection of HOCl in envirnomental and living system

Normal levels of HOCl can resist pathogen invasion and maintain cellular redox balance. However, excessive HOCl can easily harm the ecological environment and human health. Establishing a reliable approach for detection of HOCl can help resolve controversial issues regarding HOCl in physiological systems and help detect HOCl in complex environmental water samples. This study presents the design and evaluation of a HOCl-specific self-immolative fluorescent probe (OX-OCl), which is based on the N-protected phenoxazine dye structure. In aqueous solution, the probe demonstrates a rapid and highly specific response to HOCl within a brief time frame of 15 s, exhibiting good sensitivity with a limit of detection (LOD) of 15.3 nM. Notably, the reaction of OX-OCl with HOCl results in substantial changes in both UV absorption and fluorescence emission. Benefit from this, smartphone-assisted colorimetric and fluorescent sensing platforms had been developed for real-time monitoring of HOCl. Furthermore, owing to its excellent biocompatibility, OX-OCl has been successfully utilized for near-infrared bioimaging of HOCl in live cells and mouse models of arthritis. In brief, this probe offers a new perspective for the convenient monitoring of HOCl in environmental contexts and provides a visual tool for the early clinical diagnosis of related diseases.