Four important fluorescent building blocks (xanthene, cyanine, oxazine and BODIPY) for super-resolution bioimaging are judiciously assessed.

Mitochondria play a critical role in generating energy to support the entire lifecycle of biological cells, yet it is still unclear how their morphological structures evolve to regulate their functionality. Conventional fluorescence microscopy can only provide ~300 nm resolution, which is insufficient to visualize mitochondrial cristae. Here, we developed an enhanced squaraine variant dye (MitoESq-635) to study the dynamic structures of mitochondrial cristae in live cells with a superresolution technique. The low saturation intensity and high photostability of MitoESq-635 make it ideal for long-term, high-resolution (stimulated emission depletion) STED nanoscopy. We performed time-lapse imaging of the mitochondrial inner membrane over 50 min (3.9 s per frame, with 71.5 s dark recovery) in living HeLa cells with a resolution of 35.2 nm. The forms of the cristae during mitochondrial fusion and fission can be clearly observed. Our study demonstrates the emerging capability of optical STED nanoscopy to investigate intracellular physiological processes with nanoscale resolution for an extended period of time.

MXene and black phosphorus based 2D nanomaterials in bioimaging and biosensing applications.

The microviscosity change associated with reticulophagy is an important component for studying endoplasmic reticulum (ER) stress disorders. Here, a BODIPY-arsenicate conjugate 1-based fluorescent molecular rotor was designed to covalently bind vicinal dithiol-containing proteins in the ER, exhibiting a bifunction of reticulophagy initiation and microviscosity evaluation. Therefore, we could quantify the local viscosity changes during reticulophagy based on the fluorescence lifetime changes of probe 1.

Various strategies for TSQ-induced fluorophore stabilization and their application in sm-FRET as well as in super-resolution imaging microscopy are thoroughly reviewed.