Rational Design of Novel Lipophilic Aggregation-Induced Emission Probes for Revealing the Dynamics of Lipid Droplets during Lipophagy and Ferroptosis

Lipid droplets (LDs), as crucial organelles, play a significant role in some physiological processes. Monitoring the concentration of LDs and dynamic behaviors between LDs and other organelles during some physiological processes is important for studying their biological function and medical diagnosis. Herein, we report a series of aggregation-induced emission (AIE) probes AIE-Cbz-LD-Cn (n = 1, 3, 5, 7, OMe) based on the conjugation of quinoline-malononitrile (QM) and carbazole for tracking the dynamic changes of LDs and studying the association between LDs and lysosome/endoplasmic reticulum (ER). To our great delight, AIE-Cbz-LD-C3, AIE-Cbz-LD-C5, and AIE-Cbz-LD-C7 could aggregate in LDs accurately and light up the LDs with good photostability. Among them, AIE-Cbz-LD-C7 was used to visualize the interplay between LDs and lysosomes during lipophagy due to the excellent LD-specificity. We also succeeded in tracking the number of newborn LDs generated near the endoplasmic reticulum regions revealing that the number increased considerably during ferroptosis by using AIE-Cbz-LD-C7, which supplies useful evidence for the hypothesis that LDs generate from the ER. We expect the probe AIE-Cbz-LD-C7 would be a practical tool for tracking the physiological and pathological processes contacted with LDs.