A Self-degrading and NIR-II emissive type I/II photosensitizer with synergistic photodynamic and photothermal properties for antibacterial and anticancer

Effective and degradable photosensitizers are crucial for promoting the clinical application and improving the safety of phototherapy. Herein, we report a novel photosensitizer with an A–D–A molecular backbone, TIDT, obtained by centering an electron-donating indacenodithiophene group between two electron-withdrawing tricyanofurans. TIDT could form nanoparticles (NPs) by self-assembly or co-assembly with an amphiphilic hydrogel (DSPE-PEG2000) and exhibited excellent photosensitivity and photothermal performance with NIR-II fluorescence and photoacoustic signal. This photosensitivity originated from simultaneous type I and type II processes. TIDT NPs can also be effectively photodegraded owing to oxidation by the ROS generated by its photosensitivity, which would reduce their phototoxicity during metabolic processes. The result also show TIDT NPs can also be used for NIR-II fluorescence and photoacoustic imaging of tumor sites in vivo. Moreover, combined photodynamic and photothermal therapy using TIDT NPs was successfully applied to antibacterial and antitumor treatments.