Novel Hypochlorous Acid (HClO) Recognition Mechanism Base on Chlorine Oxygen Bond (Cl-O) Formation

One of the most important endogenous reactive oxygen species, hypochlorous acid (HClO) was involved in numerous pathological and physiological processes. Herein, we designed and synthesized a near-infrared fluorescence probe (CyHR) for ultrafast (within 0.2 second), sensitive (LOD of 39.44 nM), and selective response to HClO. The reaction mechanism was systematically analyzed by MS, H-NMR, HPLC-MS, and theoretical calculation. Results indicated that HClO can be recognized through CyHR, which was based on chlorine oxygen (Cl-O) bond formation. To the best of our knowledge, this study is the first to find Cl-O bonds among organic aromatic compounds, given that Cl-O bonds are popular among inorganics. Through biological experiments, CyHR was successfully applied to image exogenous and endogenous HClO in macrophage cells (RAW 264.7). Thus, CyHR is a promising tool for HClO-related physiological and pathological studies and may provide a means for designing HClO-specific fluorescence probe.