Twisted Intramolecular Charge Transfer—Aggregation-Induced Emission Fluorogen with Polymer Encapsulation-Enhanced NearInfrared Emission for Bioimaging

Fluorescence probes with strong near-infrared(NIR)emission and water solubility are considered useful visualization tools for localization marking as well as investigating cell migration and transplantation.Here,we designed and synthesized a new donor–π–acceptor(D–π–A)fluorogen,2-(4-[(E)-4-(diphenylamino)styryl]phenyl)-3-(4′-[1,2,2-triphenylvinyl]-[1,1′-biphenyl]-4-yl)fumaronitrile(TB-TPE).TB-TPE exhibits twisted intramolecular charge transfer(TICT)and aggregation-induced emission(AIE)in the NIR region,with an emission peak at 714 nm and a fluorescence quantum yield(Qy)of 6.6%in the solid state.By encapsulating TB-TPE with polystyrene–polyethylene glycol(PS-PEG),watersoluble TB-TPE-PS-PEG nanoparticles(TP NPs)are fabricated,which display polymer encapsulationenhanced emission with a Qy of 46.5%due to the strong restriction effect on the TICT process and the destruction of H aggregation for TB-TPE by the polymer matrix.Au-coated Fe_(3)O_(4)(Fe_(3)O_(4)@Au)nanocrystals were then embedded in the TP NPs to form highly fluorescent TB-TPE-Fe_(3)O_(4)-Au-PS-PEG nanoparticles(TFAP NPs)with a Qy of 39.7%.Our demonstration of successful cellular imaging of TP NPs for Hep-G2 cells and multimodality imaging of TFAP NPs in mouse liver tumors indicates that polymer-encapsulated TB-TPE offers great prospects as a multifunctional fluorescence probe for bioimaging.