Development of near-infrared mitochondrial polarity fluorescent probe for evaluating mitophagy in mice heart and potential cancer diagnosis

Mitophagy is a process that selectively removes excess or damaged mitochondria, and regulates the number of mitochondria in the cell to maintain the normal mitochondrial function. According to reports, mitophagy can cause significant changes to the intracellular microenvironment, such as affecting cell polarity. Therefore, detecting changes in polarity in the intracellular microenvironment is an effective means to monitor the autophagy process. Herein, we synthesized a polarity-sensitive fluorescent probe NIR-BT-P with a strong ICT mechanism and 900 nm near infrared region. The probe was constructed by an onium salt as the electron-deficient parent fluorophore and triphenylamine as a strong electron donating group. Studies indicated that the fluorescence intensity of NIR-BT-P increases with decreasing environmental polarity, accompanied by a redshift (812 nm-853 nm) of the maximum emission wavelength. In addition, NIR-BT-P did not interfere by viscosity, pH, or common active substances. Notably, the probe NIR-BT-P can monitor starvation and drug-induced mitophagy in real time, and successfully distinguished normal cells from cancer cells. More importantly, by visualizing the cardiomyocytes of the heart of the starvation mice group, it was found that mitophagy occurred during heart starvation. Consequently, we anticipate that NIR-BT-P could not only provide insight into the relationship between mitophagy and heart disease, but may also emerge as a potential tool for the clinical diagnosis of cancer.