Super-resolution dynamic tracking of cellular lipid droplets employing with a photostable deep red fluorogenic probe

Lipid droplets (LDs) are critical organelles involved in many physiological processes in eukaryotic cells. To visualize and study LDs, particular the small/nascent LDs, the emerging super-resolution fluorescence imaging techniques with nanoscale resolution would be much more powerful in comparison to the conventional confocal/wide-field imaging techniques. However, directly limited by the availability of advanced LDs probes, super-resolution fluorescence imaging of LDs is a practically challenging task. In this context, a superior LDs fluorescent probe named Lipi-Deep Red is newly developed for structured illumination microscopy (SIM) super-resolution imaging. This fluorescent probe features with the advantages of strong deep red/NIR emission, fluorogenic character, high LDs specificity, and outstanding photostability. These advantages enable the fluorescent probe to be finely applied in SIM super-resolution imaging, e.g. time-lapse imaging (up to 1000 frames) to monitor the LDs dynamics at nanoscale (159 nm), two-color time-lapse imaging to discover the nearby contact/interaction between LDs and mitochondria. Consequently, the fusion processes of LDs are impressively visualized at a high spatial and temporal resolution. Two kinds of contact models between LDs and mitochondria (dynamic contact and stable contact) newly proposed in the recent literatures are successfully revealed.