| Lipid droplets（LDs）,which are lipid storage organelles,surrounded by phospholipid monolayer shells and composed of neutral lipid cores which mainly contain cholesterol esters,triglycerides and protein.LDs mainly exist not only in the adipose tissue of eukaryotes,but also in other types of cells.In recent studies,researchers have found that LDs are associated with many pathological processes,such as neurodegeneration,fatty liver diseases,atherosclerosis,diabetes and even cancer.In addition,LDs must have a connection with other organelles as they are highly dynamic organelles such as mitochondria,lysosomes,and endoplasmic reticulum.Therefore,it is greatly meaningful to monitor the dynamic behaviors of LDs during some physiological processes.Based on this,through rational modification and design of fluorescent dyes,three novel small-molecule fluorescent probes for precisely targeting LDs were constructed and successfully applied to track the dynamic behaviors of LDs in living cells.1.By rational design,a series of novel AIE（aggregation-induced emission）fluorescent probes AIE-Cbz-LD-Cn（n=1,3,5,7 and OMe）were designed and synthesized for imaging LDs.They were constructed by conjugating the AIE group QM with the lipophilic part carbazole,and we adjusted the AIE properties and lipophilic of the probes by introducing different alkyl chains in the amino site of carbazole to promote intramolecular motions.To our delight,the five probes all show greatly excellent AIE effects,and AIE-Cbz-LD-C3,AIE-Cbz-LD-C5 and AIE-Cbz-LD-C7 can able to well aggregate in LDs and emit intense fluorescence.Among them,AIE-Cbz-LD-C7 was successfully applied to track the dynamic changes of LDs during lipophagy and ferroptosis in living cells,exhibiting great potential for monitoring the physiological activities related to LDs.2.We extended the conjugation of the fluorescent probe by introducing a thiophene group between the QM group and the carbazole group based on the last work.Through the related experiments,two fluorescent probes QS-Cbz-C7 and QS-Cbz-COMe were successfully synthesized.Spectral tests showed that the emission wavelength of the two fluorescent probes is located at 670 nm,and both of them have excellent AIE performance.The cell experiments show that the probe QS-Cbz-C7 can aggregate in LDs accurately and emit strong fluorescent signals.In addition,the probe QS-Cbz-C7 was successfully applied to track the dynamic changes of LDs during lipophagy in living cells,indicating that QS-Cbz-C7 can be used to track activities of LDs-related physiological behaviors.3.A novel NIR AIEgen QY-OH was constructed by linking QM and xanthene through a double bond.In the aggregated state of QY-OH,the fluorescence emission at 700 nm was extremely enhanced,and the absorption of the probe was red-shifted（520 nm to 650 nm）compared to the organic solvent.In contrast,the fluorescence intensity is very low and no fluorescence can be seen in the solvent.Therefore,QY-OH is more suitable for intracellular imaging because of lower background fluorescence interference and higher imaging fidelity. |
