A deep-red emission AIE fluorescent probes based on coumarin for imaging lipid droplets in living cells

In this work, we constructed two novel fluorescent probes based on coumarin derivatives for imaging lipid droplets. The photophysical properties indicated that probe LD-HJZ1 exhibited an aggregation-caused quenching (ACQ) feature, while probe LD-HJZ2 showed obviously aggregation-induced emission (AIE) behavior. In addition, the maximum emission wavelength of probe LD-HJZ2 was localized around 687 nm with 90% water content. Cell imaging experiments demonstrated that the fluorescence images of probes LD-HJZ1 and LD-HJZ2 were overlapped well with the commercial lipid droplet dyes. Interestingly, probe LD-HJZ2 was capable of targeting lipid droplets within a short time (< 1 min) with or without wash-free procedure. Furthermore, probe LD-HJZ2 could be used to detect the changes in the number of lipid droplets under starvation conditions and oleic acid stimulation. This work provides a new perspective for the development of fluorescent probes with deep-red emission for targeting lipid droplets.