A highly selective AIE fluorogen for lipid droplet imaging in live cells and green algae

Lipid droplets (LDs) are subcellular organelles for energy storage and lipid metabolism regulation. Here we report an aggregation-induced emission-active fluorogen, TPE-AmAl, for specific LD imaging. TPE-AmAl is cell-permeable: upon entering the live cells, the dye molecules can selectively accumulate in the LDs and turn on the fluorescence. TPE-AmAl possesses twisted intramolecular charge transfer properties as well: the emission colour in the hydrophobic LDs is blue-shifted by >100 nm than that in aqueous buffers. Compared with the commercial lipid droplet dye, TPE-AmAl demonstrates the advantages of low background, short staining time, high selectivity, excellent biocompatibility, and good photostability. The utilization of TPE-AmAl for LD staining in green algae is also demonstrated, indicating their potential application in the high-throughput screening of high-value microalgae as a preferential biofuel source.