A highly selective two-photon probe with large turn-on signal for imaging endogenous HOCl in living cells

Abstract Hypochlorous acid (HOCl) is one of the typical reactive oxygen species (ROS), which plays a crucial role in the immune system, and is involved in many neurodegenerative disorders, such as ischemic stroke, Alzheimer's, and Parkinson's disease. A two-photon probe for sensing HOCl with high selectivity, fast response (within 30 s), good penetration depth and low cytotoxicity is reported. Under two-photon excitation, the probe exhibited a remarkable fluorescence ‘‘turn-on’’ response to HOCl. Furthermore, the probe was successfully applied to the monitoring of endogenous HOCl stimulated by lipopolysaccharide in living microglia BV-2 cells.