Mitochondria are vital subcellular organelles which can generate energy to support the entire life cycle of biological cells. However, conventional fluorescence microscopy cannot provide a high enough resolution to visualize mitochondrial cristae. This study demonstrates the emerging capability of optical STED nanoscopy to investigate intracellular physiological processes with nanoscale resolution for an extended period of time.
Here, the authors developed an enhanced squaraine variant dye (MitoESq-635) to study the dynamic structures of mitochondrial cristae in live cells with a super-resolution technique. They performed time-lapse imaging of the mitochondrial inner membrane in living HeLa cells for over 50 min (3.9 sec per frame with 71.5 sec dark recovery) with a resolution of 35.2 nm. The forms and shapes of the cristae during mitochondrial fusion and fission can be clearly observed. The labelling specificity and performance of MitoESq-635 with low-power STED make it highly attractive as a next-generation standard for long-term super-resolution imaging of mitochondria.