A fluorescent probe based on a coumarin-aurone moiety for visualizing polarity changes in lipid droplets under multiple modes

Lipid droplets (LDs) have a unique structure composed of a monolayer of phospholipids surrounding a neutral lipid core. Changes in lipid droplet polarity are closely associated with the development and progression of various diseases. Therefore, a fluorescent probe ( LD-CK ) based on coumarin-aurone moiety exhibiting excellent targeting towards LDs and sensitivity to polarity changes was developed. LDs have very low water content, and the probe LD-CK is highly sensitive to polarity changes induced by even minor fluctuations in water content from 0 % to 10 %, resulting in a significant red-shift of the probe's fluorescence peak by 58 nm. This highlights the probe's suitability for monitoring polarity fluctuations within LDs. Furthermore, compared to commercial lipid droplet probes, the probe LD-CK exhibits excellent photostability. The probe also successfully demonstrates lipid changes in zebrafish during the embryonic stage, normal larval stage, and after starvation treatment. Simultaneously, by employing confocal microscopy, LD-CK successfully monitors the accumulation of lipid droplets induced by oleic acid, as well as the enhanced polarity under oxidative stress conditions in cells. This demonstrates the probe's significant potential in diagnosing polarity-related lipid droplet disorders.