A novel colorimetric and ratiometric fluorescent probe for monitoring lysosomal HOCl in real time

Hypochlorous acid (HOCl), a kind of reactive oxygen species (ROS), is involved in numerous lysosomal functions. Abnormal excess or deficiency of HOCl in lysosome could not only disrupt control of apoptosis, but also relates to numerous neurodegenerative diseases. However, monitoring the subtle concentration change of lysosomal HOCl in vivo is limited. Herein, a highly sensitive ratiometric fluorescent probe (NAP-RS) was rationally designed for measuring lysosomal HOCl fluctuations. NAP-RS provides a clear ratiometric fluorescence response to HOCl with large emission gap (186 nm), rapid maximum response time (<3 s) and ultrasensitivity (limit of detection = 36 nM) at biologically-relevant concentrations. In addition, NAP-RS can be efficiently employed to visualize exogenous and endogenous lysosomal HOCl. As a matter of fact, this work will provide a new way for the improved measurement of lysosomal HOCl, and a general molecular design methodology for the facile preparation of more refined fluorescent probes.