A Sensitive and Selective Fluorescent Probe for Real-Time Detection and Imaging of Hypochlorous Acid in Living Cells

[Image: see text] Hypochlorous acid (HClO), a reactive oxygen species, plays an essential role in the processes of physiology and pathology via reacting with most biological molecules. The abnormal level of HClO may cause inflammation, especially arthritis. To further understand its key role in inflammation, in situ detection of HClO is necessary. Herein, a water-soluble small molecule fluorescent probe (HDI-HClO) is employed to monitor and identify trace amounts of HClO in the biological system. In the presence of HClO, the probe releases a hydroxyl group emitting strong fluorescence because of the restoration of the intramolecular charge transfer process. Furthermore, this probe displays a 150-fold fluorescence enhancement accompanied by a large Stokes shift and a lower detection limit (8.3 nM). Moreover, the probe can make a rapid response to HClO within 8 s, which provides the possibility of real-time monitoring of intracellular HClO. Based on the advantages of rapid dynamics, good water solubility, and excellent biocompatibility, this probe could effectively monitor the fluctuations of exogenous and endogenous HClO in living cells. The fluorescence imaging of HDI-HClO indicated that it is an excellent potential approach for comprehending the relationship between inflammation and HClO.