New Application of the Commercially Available Dye Celestine Blue B as a Sensitive and Selective Fluorescent Turn-On Probe for Endogenous Detection of HOCl and Reactive Halogenated Species

Hypochlorous acid (HOCl) derived from hydrogen peroxide and chloride anion by myeloperoxidase (MPO) plays a significant role in physiological and pathological processes. Herein we report a phenoxazine-based fluorescent probe Celestine Blue B (CB) that is applicable for HOCl detection in living cells and for assaying the chlorinating activity of MPO. A remarkable selectivity and sensitivity (limit of detection is 32 nM), along with a rapid turn-on response of CB to HOCl was demonstrated. Furthermore, the probe was able to detect endogenous HOCl and reactive halogenated species by fluorescence spectroscopy, confocal microscopy, and flow cytometry techniques. Hence, CB is a promising tool for investigating the role of HOCl in health and disease and for screening the drugs capable of regulating MPO activity.

Automated summary

This paper introduces a fluorescent probe called Celestine Blue B (CB), which can be used for HOCl detection in living cells and for assaying the chlorinating activity of MPO. The probe shows remarkable selectivity and sensitivity, and has a rapid response to HOCl. It can also detect endogenous HOCl and reactive halogenated species using various techniques.