Precise Molecular Engineering of Photosensitizers with Aggregation-Induced Emission over 800 nm for Photodynamic Therapy

Owing to efficient singlet oxygen (O-1(2)) generation in aggregate state, photosensitizers (PSs) with aggregation-induced emission (AIE) have attracted much research interests in photodynamic therapy (PDT). In addition to high O-1(2) generation efficiency, strong molar absorption in long-wavelength range and near-infrared (NIR) emission are also highly desirable, but difficult to achieve for AIE PSs since the twisted structures in AIE moieties usually lead to absorption and emission in short-wavelength range. In this contribution, through acceptor engineering, a new AIE PS of TBT is designed to show aggregation-induced NIR emission centered at 810 nm, broad absorption in the range between 300 and 700 nm with a large molar absorption coefficient and a high O-1(2) generation efficiency under white light irradiation. Further, donor engineering by attaching two branched flexible chains to TBT yielded TBTC8, which circumvented the strong intermolecular interactions of TBT in nanoparticles (NPs), yielding TBTC8 NPs with optimized overall performance in O-1(2) generation, absorption, and emission. Subsequent PDT results in both in vitro and in vivo studies indicate that TBTC8 NPs are promising candidates in practical application.