Recent progress on small molecule-based fluorescent imaging probes for hypochlorous acid (HOCl)/hypochlorite (OCl⁻)

Reactive oxygen species (ROS) and nitrogen species (RNS) are very important in various pathological and physiological processes. In particular, hypochlorous acid/hypochlorite (HOCl/OCl⁻) is one of the most important reactive oxygen species (ROS), which is endogenously produced from H₂O₂ and Cl⁻ by myeloperoxidase (MPO) catalysis. HOCl is both beneficial and harmful to living species including humans. HOCl can destroy invasive bacteria as an immune defense system while, on the other hand, it can cause many diseases including cancers due to pathogenic oxidative stress injury. Accordingly, fluorescent imaging probes for HOCl have been actively investigated in recent years. In this review, we cover the recent progress from 2019 to 2021 on small molecule-based fluorescent imaging probes for hypochlorous acid (HOCl)/hypochlorite (OCl⁻).