Efficient Thermally Activated Delayed Fluorescence Materials with Aggregation-Induced Emission for Lipid Droplet Imaging

Thermally activated delayed fluorescence (TADF) materials with aggregation-induced emission (AIE) propertiesare promising for autofluorescence-free bioimaging. However, efficient AIE-TADF luminogens that can specifically target lipid droplets and enable high-quality fluorescence imaging are very limited. 3 new organic luminophores were successfully developed by introducing diphenylamine, 9,10-dihydro-9,9-diphenylanthracene, and 9,10-dihydro-9,9-dimethylanthracene, respectively, onto the phthalimide moiety, along with a lipid droplet-targeting group, morpholine. These compounds exhibitedexcellent AIE properties with fluorescence quantum yields up to 46.5% in the solid state. Moreover, 5-(diphenylamine)-2-(2-morpholinoethyl)isoindoline-1,3-dione (1) and 5-(9,9-diphenylacridine-10(9H)-yl)-2-(2-morpholinoethyl) isoindoline-1,3-dione (2) only displayed prompt fluorescence, while 5-(9,9-dimethylacridine-10(9H)-yl)-2-(2-morpholinoethyl)isoindoline-1,3-dione (3) demonstrated intense TADF. More importantly, 3 exhibited good biocompatibility and the ability to enter cells and specifically target lipid droplets, enabling high-brightness fluorescence imaging. The Pearson's correlation coefficient between 3 and the commercially available lipid droplet dye Bodipy reached 0.87 in the imaging area. This work provides a new approach for the development of high-performance AIE-TADF molecules for bioimaging applications