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.