Design of the chiral AIEgens for NIR-II luminescence imaging through structural modulation with multiple AIE units

Abstract

Near-infrared II fluorescence imaging holds great promise for in vivo imaging and imaging-guided surgery with deep penetration and high spatiotemporal resolution. However, most of 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 rigid structure, aromatic vinyl thiophene skeleton, 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.