A BF ₂ -bridged J-aggregate on a donor–acceptor conjugated oligomer with NIR-emissive theranostics for efficient bioimaging and cancer therapy

The design and synthesis of integrated diagnostic and therapeutic materials are urgently needed to enhance the precise phototherapy (PTT) of tumors. However, there is still an urgent need to develop high-performance organic photothermal agents with suitable theranostic properties, especially those with near-infrared second window (NIR-II) emissive potency. In this study, a BF₂-bridged J-aggregates on the donor-acceptor (D-A) conjugated oligomer CH-1 was designed and synthesized. With the J-aggregate strategy, D-A-type CH-1 in nanoparticles (NPs) achieved enhanced intramolecular charge transfer and thus redshifted the absorption. Under 808 nm laser illumination, the CH-1 NPs achieved a high photothermal conversion efficiency of 66.8% for PTT, resulting in sufficient NIR-II fluorescence emission. <i>In vitro</i> experiments demonstrated that CH-1 NPs could produce enough local heat upon continuous laser illumination, resulting in apoptosis-mediated tumor cell death. <i>In vivo</i> experiments demonstrated the effectiveness of CH-1 NPs in high-resolution NIR-II imaging <i>via</i> whole-body angiography and tumor accumulation beyond 1400 nm. Subsequently, tumor homing and the performance of CH-1 NPs in tumor elimination were further demonstrated in a tumor-bearing mouse model. This study provides a paradigm for the development of NIR J-aggregate nanomedicines, achieving high-performance tumor phototheranostics with good biosafety.