An easily synthesized AIE luminogen for lipid droplet-specific super-resolution imaging and two-photon imaging

To obtain lipid droplets (LDs)-specific super-resolution cellular imaging and deep-penetrated tissue imaging, an imaging platform of DTPA-BT-M with aggregation-induced emission (AIE) characteristics for stimulated emission depletion (STED) nanoscopy and two-photon fluorescence (TPF) microscopy was developed here. Benefiting from its excellent AIE properties, superior fluorescence properties in a deep-red region are observed for DTPA-BT-M with a high photoluminescence quantum yield of up to 33.96% in the solid state. In addition, DTPA-BT-M also exhibits large Stokes' shift, outstanding photostability, excellent biocompatibility and high LD specificity. Furthermore, a large two-photon absorption cross section of up to 1581 GM is also achieved in DTPA-BT-M due to its symmetrical D-A-D architecture. Therefore, the developed AIE luminogen is simultaneously applied in STED nanoscopy and TPF microscopy, leading to an ultra-high resolution (full width at half maximum value, FWHM = 95 nm) in DTPA-BT-M-stained LDs via STED nanoscopy and also a much deep penetration of ~300 µm for lung tissue in BALB/C nude mice by TPF microscopy. The results here indicate that the easily synthesized DTPA-BT-M can be an impressive imaging platform for LDs-specific super-resolution cell imaging and two-photon tissue imaging, thus providing the possibility to further understand LDs' roles in the metabolic process in biological research.