Near-Infrared Ratiometric Fluorescent Probe for Monitoring Hypochlorous Acid in Ferroptosis Models

Ferroptosis is an iron-dependent, regulated cell death caused by the disruption of the oxidation–reduction balance. The hypochlorous acid (HClO) levels are closely correlated with the onset and progress of ferroptosis. Hence, investigating the underlying relationships between HClO changes and ferroptosis is particularly vital. To this end, we presented a new near-infrared (NIR) ratiometric fluorescent probe (BV-HD) based on the oxidation of the phenothiazine moiety for imaging HClO variations in ferroptosis models. Employing this BV-HD, the exogenous and endogenous HClO concentrations were consecutively detected in cells via ratiometric fluorescent intensity. Moreover, by virtue of NIR ratiometric fluorescent values, the up-regulated HClO fluxes were clearly observed in Erastin-induced ferroptosis cells. Upon exposure to ferrostatin-1 or glutathione or N-acetylcysteine, the ratiometric fluorescent intensity and NIR fluorescence intensity of Erastin-induced cells were both dramatically suppressed. Importantly, high levels of HClO were subsequently detected in drug-induced liver injury and ferroptosis mice. Therefore, this is an effective method based on this NIR ratiometric fluorescent probe, which was used for rapidly monitoring HClO concentrations and uncovering in-depth biological mechanisms in ferroptosis-related diseases.