A mitochondria-targeting near-infrared multifunctional fluorescent probe based on carbazole and its application in biological imaging.

Polarity, viscosity and peroxynitrite (ONOO^-) are key factors in determining mitochondrial function and activity, and real-time monitoring of these parameters is important for gaining insight into the physiological mechanisms involved. In this study, we developed a new multifunctional fluorescent probe CNB-2 for monitoring mitochondrial polarity, viscosity, and ONOO^- level fluctuations. CNB-2 demonstrated robust responses to polarity and viscosity, with its fluorescence intensity exhibiting a strong linear correlation to the logarithm of polarity parameters and viscosity, increasing significantly as these parameters rise. Notably, for ONOO^- detection, CNB-2 is characterized by rapid response, high selectivity, a low detection limit (51.3 nM), and a large Stokes shift (130 nm). Moreover, CNB-2 can be used for live cell imaging of mitochondrial polarity, viscosity, and ONOO^-, as well as monitoring of changes in ONOO^- concentration in real-time during ferroptosis. Therefore, the prepared probe CNB-2 provides a reliable tool for better understanding the mitochondrial microenvironment and a new way for diagnosing ferroptosis-related diseases.