Dual-targeted fluorescent probe for tracking polarity and phase transition processes during lipophagy.

Eukaryotic cells regulate various cellular processes through membrane-bound and membrane-less organelles, enabling active signal communication and material exchange. Lysosomes and lipid droplets are representative organelles, contributing to cell lipophagy when their interaction and metabolism are disrupted. Our limited understanding of the interacting behaviours and physicochemical properties of different organelles during lipophagy hinders accurate diagnosis and treatment of related diseases. In this contribution, we report a fluorescent probe, PTZ, engineered for dual-targeting of lipid droplets and lysosomes. PTZ can track liquid-liquid phase separation and respond to polarity shifts through ratiometric fluorescence emission, elucidating the lipophagy process from the perspective of organelle behavior and physicochemical properties. Leveraging on the multifunctionality of PTZ, we have successfully tracked the polarity and dynamic changes of lysosomes and lipid droplets during lipophagy. Furthermore, an unknown homogeneous transition of lipid droplets and lysosomes was discovered, which provided a new perspective for understanding lipophagy processes. And this work is expected to serve as a reference for diagnosis and treatment of lipophagy-related diseases.