High photostability probes for tagging mitochondrial cristae via STED microscopy

Mitochondrial cristae are the site of intracellular biochemical reactions that play important roles in many life activities, and the destruction of mitochondrial cristae will lead to mitochondrial dysfunction inducing related diseases. Therefore, the visualization of mitochondria cristae is of great significance for physiopathology and medicine. Herein, we reported a group of cyanine-based fluorescent probes (Cy-OH and Cy-Cl) for tagging mitochondrial cristae under STED microscopy. Cy-OH and Cy-Cl could gather in the inner mitochondrial membrane via electrostatic interaction. And the ability of Cy-OH to target mitochondria depending on mitochondrial membrane potential (MMP), while Cy-Cl could tightly immobilize in mitochondria benefiting by the reaction between its chloromethyl group and mitochondrial proteins, regardless of MMP. Moreover, Cy-Cl reacted fully with mitochondrial proteins during the staining process and exhibited superior performance than some commercial mitochondrial trackers. Importantly, profiting from the high photostability and high brightness of the two probes, they could clearly depict the mitochondrial cristae at a concentration of 200 nM under STED microscopy. We believe that Cy-OH and Cy-Cl could serve as vigoroso tools to study mitochondrial cristae changes in various physiological and pathological processes.