A Small-Molecule Fluorescent Probe for the Detection of Mitochondrial Peroxynitrite

Reactive oxygen species (ROS) are pivotal signaling molecules that control a variety of physiological functions. As a member of the ROS family, peroxynitrite (ONOO^-) possesses strong oxidation and nitrification abilities. Abnormally elevated levels of ONOO^- can lead to cellular oxidative stress, which may cause several diseases. In this work, based on the rhodamine fluorophore, we designed and synthesized a novel small-molecule fluorescent probe (DH-1) for ONOO^-. Upon reaction with ONOO^-, DH-1 exhibited a significant fluorescence signal enhancement (approximately 34-fold). Moreover, DH-1 showed an excellent mitochondria-targeting capability. Confocal fluorescence imaging validated its ability to detect ONOO^- changes in HeLa and RAW264.7 cells. Notably, we observed the ONOO^- generation during the ferroptosis process by taking advantage of the probe. DH-1 displayed good biocompatibility, facile synthesis, and high selectivity, and may have potential applications in the study of ONOO^--associated diseases in biosystems.