Bright near-infrared α-tetraphenyletheneBODIPY nanoprobes with high aggregated state emission quantum yields in aqueous system for lipid droplet-specific imaging

Lipid droplets (LDs) have been found to be innate immune first-responders integrating cell metabolism and host defense. The abnormal changes of LDs have been believed to be highly associated with many diseases such as metabolic diseases, cardiovascular disease, viral infections and cancer. Two organic LD-specific nanoprobes have been self-assembled from α-tetraphenyletheneBODIPYs, which exhibited bright near-infrared aggregated state emission with high fluorescence quantum yields up to 0.81 in aqueous system and high photostability, as well as large Stokes shifts up to 130 nm. In the solid powder state, they showed strong NIR fluorescence with red-shifted emission peaks at 700 and 790 nm. The recorded high NIR fluorescence in solid state and in water-induced aggregates can be ascribed to the steric hindrance provided by the TPE groups, which prohibits the π–π interactions of BODIPY planes and avoids the aggregation-caused quenching (ACQ) effect in the BODIPY emission. More importantly, these NIR-emitting nanoprobes exhibit higher LD-specificity than commercial LD-specific BODIPY 493/503 and have been applied for the real-time imaging of intracellular LD and lipid-rich yolk sac of the zebrafish larvae, and monitoring of the LD–lysosome interplay in living cells, which is useful for the early diagnosis of LD-related diseases.