The development and application of a fluorescence lifetime imaging-based probe for monitoring cellular lipid droplet polarity

The polarity of cellular lipid droplets is implicated in a range of diseases, but there is a scarcity of fluorescent probes specifically designed to monitor these polarity changes. In this study, we present the development of a novel fluorescence lifetime probe, designated as PLDP, aimed at tracking polarity changes in intracellular lipid droplets. This probe exhibits high specificity and sensitivity to variations in polarity and can be detected using fluorescence lifetime imaging technology. We successfully applied the PLDP probe for live cell imaging, enabling the detection of polarity changes induced by various conditions, including LPS treatment, starvation, and ferroptosis. Furthermore, it was revealed that the PLDP probe colocalize with the established lipid droplet probe BODIPY, underscoring their specific affinity for lipid droplets. FLIM imaging results indicate that the PLDP probe can monitor the dynamic changes in the polarity of intracellular lipid droplets in real-time, particularly following oleic acid treatment. In the imaging of fatty liver sections, PLDP probe revealed abnormal lipid droplet polarity, offering novel insights into the underlying of fatty liver pathogenesis. The PLDP probe developed in this study serves as a robust tool for investigating the polarity of lipid droplets in cell and enhances our understanding of cell polarity, lipid droplet biology, and associated diseases.