A large Stokes shift NIR fluorescent probe for visual monitoring of mitochondrial peroxynitrite during inflammation and ferroptosis and in an Alzheimer's disease model.

The excessive formation of peroxynitrite (ONOO - ) in mitochondria has been implicated in various pathophysiological processes and diseases. However, owing to short emission wavelengths and small Stokes shifts, previously reported fluorescent probes pose significant challenges for mitochondrial ONOO - imaging in biological systems. In this study, a near-infrared (NIR) fluorescent probe, denoted as DCO-POT, is designed for the visual monitoring of mitochondrial ONOO - , displaying a remarkable Stokes shift of 170 nm. The NIR fluorophore of DCO-CHO is released by DCO-POT upon the addition of ONOO - , resulting in off-on NIR fluorescence at 670 nm. This phenomenon facilitates the high-resolution confocal laser scanning imaging of ONOO - generated in biological systems. The practical applications of DCO-POT as an efficient fluorescence imaging tool are verified in this study. DCO-POT enables the fluorometric visualization of ONOO - in organelles, cells, and organisms. In particular, ONOO - generation is analyzed during cellular and organism-level (zebrafish) inflammation during ferroptosis and in an Alzheimer's disease mouse model. The excellent visual monitoring performance of DCO-POT in vivo makes it a promising tool for exploring the pathophysiological effects of ONOO - .