Design of chiral AIEgens for NIR-II luminescence imaging through structural modulation with multiple AIE units
Abstract
Near-infrared II fluorescence imaging holds great potential for in vivo imaging and imaging-guided surgery with deep penetration and high spatiotemporal resolution. However, most of the NIR-II luminescent dyes undergo luminescence quenching due to molecular aggregation in aqueous solutions, which greatly hinders their practical applications in living organisms. Herein, we propose a molecular design philosophy to explore pure organic NIR-II luminescent dyes with both redshifted emission and high quantum yield by integrating multiple AIE units. In this study, the chiral rosin NIR-II organic aggregation-induced emission (AIE) fluorophore (BTX), encapsulated as nanoparticles (BTX NPs) for in vivo biomedical imaging, was designed and synthesized. BTX integrates multiple AIE units, such as natural chiral rosin with a rigid structure, aromatic vinyl thiophene skeletons, and inner long alkyl chain thiophene units, which effectively enhance biocompatibility and the emission intensity in the NIR-II region. The fluorescence quantum efficiency of BTX NPs reached 4.7%, exhibiting excellent photostability and deeper penetration depth. The in vivo experimental results show that BTX NPs have a high signal-to-background ratio and exhibit significant NIR-II signal accumulation at the tumour site. The above results indicate that BTX demonstrates exceptional imaging quality, providing strong support for applications in imaging-guided therapies in the NIR-II field.