Near-infrared AIEgens with high singlet-oxygen yields for mitochondria-specific imaging and antitumor photodynamic therapy.

AIE-active photosensitizers (PSs) are promising for antitumor therapy due to their advantages of aggregation-promoted photosensitizing properties and outstanding imaging ability. High singlet-oxygen (O) yield, near-infrared (NIR) emission, and organelle specificity are vital parameters to PSs for biomedical applications. Herein, three AIE-active PSs with D-π-A structures are rationally designed to realize efficient O generation, by reducing the electron-hole distribution overlap, enlarging the difference on the electron-cloud distribution at the HOMO and LUMO, and decreasing the Δ. The design principle has been expounded with the aid of time-dependent density functional theory (TD-DFT) calculations and the analysis of electron-hole distributions. The O quantum yields of AIE-PSs developed here can be up to 6.8 times that of the commercial photosensitizer Rose Bengal under white-light irradiation, thus among the ones with the highest O quantum yields reported so far. Moreover, the NIR AIE-PSs show mitochondria-targeting capability, low dark cytotoxicity but superb photo-cytotoxicity, and satisfactory biocompatibility. The experimental results demonstrate good antitumor efficacy for the mouse tumour model. Therefore, the present work will shed light on the development of more high-performance AIE-PSs with high PDT efficiency.