Responsive Fluorescence Probe for Selective and Sensitive Detection of Hypochlorous Acid in Live Cells and Animals

Graphical Sensing and imaging of hypochlorous acid (HOCl) : A new responsive fluorescence probe, PQI , is reported for quantitative fluorescence detection of HOCl in aqueous solution and live organisms. Visualisation of HOCl in live cells and in vivo sensing and imaging of HOCl in zebrafish and nude mice were achieved by using PQI as the fluorescence probe. The development of effective bioanalytical methods for rapid, sensitive and specific detection of HOCl in vitro and in vivo plays a key role for better understanding the roles of this molecule in normal and diseased conditions, but remains challenging due to the highly reactive nature of HOCl and the complicated biological conditions. In this work, a new fluorescence probe, PQI , was developed for monitoring of the HOCl level in biological samples. PQI was easily synthesized by a one-step condensation reaction. Upon addition of HOCl, significant changes in the absorption spectra and the color of the solution were noticed, facilitating the “naked eye” detection of HOCl in PBS buffer. The fluorescence of PQI was found to be significantly increased within a few seconds, leading to “OFF-ON” fluorescence response towards HOCl. The sensing mechanism, oxidation of thioether by HOCl, was confirmed by HRMS titration analysis. PQI features a large Stokes shift, high sensitivity and selectivity, and rapid fluorescence response towards HOCl. Quantitative detection of HOCl in single live cells was demonstrated through fluorescence imaging and flow cytometry analysis. PQI was then successfully used in visualisation of HOCl in live zebrafish and nude mice.