Construction of heteroaryl-bridged NIR AIEgens for specific imaging of lipid droplets and its application in photodynamic therapy.

As a kind of subcellular organelle, lipid droplets (LDs) play a critical role in the body's normal metabolism. LDs have gained increasing attention as a fluorescent photodynamic target site. Near-infrared (NIR) organic light-emitting luminescent materials, with aggregation-induced emission (AIE)-active feature, preeminent LD-imaging ability, and effective reactive oxygen species (ROS) production property, have been widely used for photodynamic therapy (PDT) in diagnostic therapeutics, but its application remains challenging. In the present work, three novel NIR organic compounds with AIE-active feature, namely, TPET-Is, TPET-Fu, and TPEF-Is, were developed and synthesized. These heteroaryl-bridged molecules possess a donor-donor-π-acceptor structure and strong intramolecular charge transfer character. These AIEgens are capable of high-fidelity LD imaging in living cells (Pearson's coefficient values: 0.94, 0.96, 0.97) due to their biocompatibility, good photostability, and strong lipophilicity (LogP values: 9.39, 7.89, 8.03), respectively. Moreover, they can be also applied in bright imaging the LDs of oil-rich plant tissues, such as those of sunflower seeds. The respective AIEgens TPET-Fu of these compounds can also produce ROS in the condition of white light to effectively kill live Hela cells. The present study thus provides a potential strategy through heteroaryl-bridged molecular engineering for LD-targeted imaging and PDT application.