Stable Organic Photosensitizer Nanoparticles with Absorption Peak beyond 800 Nanometers and High Reactive Oxygen Species Yield for Multimodality Phototheranostics

Effective multimodality phototheranostics under deep-penetration laser excitation is highly desired for tumor medicine, which is still at a deadlock due to lack of versatile photosensitizers with absorption located in the long-wavelength region. Herein, we demonstrate a stable organic photosensitizer nanoparticle based on molecular engineering of benzo[c]-thiophene (BT)-based photoactivated molecules with strong wavelength-tunable absorption in the near-infrared region. Via molecular design, the absorption and singlet oxygen generation of BT molecules would be reliably tuned. Importantly, the nanoparticles with a red-shifted absorption peak of 843 nm not only show over 10-fold reactive oxygen species yield compared with indocyanine green but also demonstrate a notable photothermal effect and photoacoustic signal upon 808 nm excitation. The in vitro and in vivo experiments substantiate good multimodal anticancer efficacy and imaging performance of BT theranostics. This work provides an organic photosensitizer nanoparticle with long-wavelength excitation and high photoenergy conversion efficiency for multimodality phototherapy.