Deep-Red Aggregation-Induced Emission Luminogen Based on Dithiofuvalene-Fused Benzothiadiazole for Lipid Droplet-Specific Imaging

Lipid droplets (LDs) actively participate in many biological processes whose abnormality will result in different diseases; thus, it is vital to study the bioactivities of LDs. Red/near-infrared (NIR) fluorescent materials with aggregation-induced emission (AIE) characteristics are suitable for LD imaging and tracking because of their noninvasiveness, large Stokes shift, low photodamage, and excellent photostability. Meanwhile, two-photon imaging emerges with advantages of higher resolution and deeper penetration depth. In this work, a new acceptor core, benzothiadiazol-7-ylidene malononitrile (BSM), is proposed to construct a deep-red AIE luminogen (AIEgen) with a D–A structure. The AIEgen shows a high solid-state quantum yield of 13%, whose emission spectrum covers the visible and NIR I region. Furthermore, this molecule exhibits an excellent two-photon imaging performance and high specificity toward lipid droplets in all levels of biosubstances, including cells, tissues, and living zebrafish embryos, showing high potential for LD imaging and tracking in biomedical research.