1064 nm-absorbing semiconducting polymer nanoparticles for multimodal photoacoustic and fluorescence imaging

Although second near-infrared (NIR-II) photoacoustic (PA) imaging affords deep tissue penetration, developing efficient contrast agents remains challenging due to a lack of suitable optical absorbers. Herein, we report semiconducting polymer nanoparticles (SPNs) for dual-modal PA and NIR fluorescence imaging, featuring a high optical absorption coefficient at 1064 nm that facilitates excitation via high-power Nd:YAG lasers. Phantom evaluations revealed a linear PA signal correlation, with a low detection limit of 0.05 cm^-1. In vivo studies in tumor-bearing mice demonstrated passive SPN accumulation in tumor tissue, successfully visualized by both PA and NIR fluorescence imaging. These results indicate that SPNs are promising contrast agents for dual-modal imaging.