Mitochondrion-Specific Blinking Fluorescent Bioprobe for Nanoscopic Monitoring of Mitophagy.

Dynamic changes of mitochondrial morphology play an important role in cellular metabolism. Real-time monitoring mitochondrial ultrastructural dynamics at nanometer-scale resolution is crucially desired for further understanding of the mitochondria-based cellular function. In this work, we introduce a fluorescent carbon dot, which can selectively target mitochondria in live cells (named as MitoCD). MitoCD can effectively accumulate in mitochondria regardless of the decrease or vanishing of mitochondrial membrane potential (MMP), enabling the exploration of MMP-independent mitochondrial process. Moreover, the MitoCD is a thiol-based reaction-free probe that target mitochondria without consuming the thiol groups from mitochondrial proteins. Additionally, the MitoCD possesses good photophysical properties under physiological conditions, such as burst-like blinking, high photon counts, and low "on"/"off" ratio, which are specifically suitable for localization-based nanoscopic imaging. According to the optical microscopic imaging results, dynamical fission and fusion processes from mitochondria have been observed in live cells. During mitophagy, it is found that reticular formation of the mitochondria gradually collapsed, and then a portion of mitochondria split and vanished. Owing to the attractive biological and special photophysical properties, this probe displays promising application in a variety of super-resolution based biological studies and will provide deep insight in mitochondrial metabolism.