Ultra-Photostable Fluorescent Boron-Bridged Near-Infrared Probes to Reveal New Mode of Lipid Droplet-Mitochondria Interaction at STED Super-Resolution

Interactions between lipid droplets (LDs) and mitochondria are vital for maintaining the cellular metabolism and energy homeostasis. However, visualizing these interaction dynamics at a high resolution in live cells is still very challenging. Here, a boron-bridged near-infrared probe (QI-BF) was developed specifically for low-power stimulated emission depletion (STED) super-resolution imaging of LDs. QI-BF exhibited excellent photostability and enabled continuous scanning of 1000+ frames using a STED laser (0.96 MW cm^-2, 775 nm), without significant fluorescence decay. Furthermore, dynamic dual-color STED super-resolution visualization of the morphological interactions between LDs and mitochondria was achieved with the aid of commercial mitochondrial dyes. For the first time, the dynamic process of mitochondrial wrapping around the LDs and LD-mediated mitochondria tubulation were successfully captured. This study sheds light on developing ultraphotostable organic fluorescent probes for versatile low-power STED nanoscopy.