Light-up lipid droplets dynamic behaviors using rationally designed carbon dots

Lipid droplets (LDs) are essential organelles used to store lipids and participate in cellular lipid metabolism. Imaging LDs is an intuitive approach to comprehend their biological functions. Herein, the LDs-targeted CDs (LD-CDs) featuring robust solvatochromic emission were elaborately designed by a Schiff base reaction using 1, 2-diamino-4-fluorobenzene, 3-dimethylaminophenol, and thiourea as precursors. The LD-CDs exhibited a remarkable sensitivity to polarity changes over a broad linear range (0.0205-0.3213), owing to its unique intramolecular charge transfer effect (ICT). Moreover, the favorable lipophilicity of LD-CDs endows it with the capability to light up LDs with high specificity. Due to their good lipophilicity and biocompatibility, the LD-CDs were able to differentiate cancer cells from normal cells and keep real-time track of LDs dynamic behaviors, including dissociation, migration, and fusion. Leveraging the multifunctionality of LD-CDs, we have also observed the dynamic changes of lysosomes and LDs during lipophagy. Additionally, the LD-CDs were employed to reveal the polarity change of LDs in living cells and zebrafish under oleic acid stimulation and to visualize lipid metabolism in zebrafish. We deem that this work will expand the applications of CDs in biological imaging and make further contributions to the field of LDs-associated metabolism and diseases.