Pyridinium-substituted tetraphenylethylene salt-based photosensitizers by varying counter anions: a highly efficient photodynamic therapy for cancer cell ablation and bacterial inactivation

Cancer and bacterial infection seriously threaten the health of human beings. The development of an image-guided photosensitizer with a "Two-in-One"function that can be simultaneously used for both efficient cancer cell ablation and rapid bacterial inactivation is highly in demand. In this project, we designed and prepared two aggregation-induced emission luminogens (AIEgens) (called TPEPy-I and TPEPy-PF6) with a strong electron push-pull effect. They have a near-infrared (NIR) emission, a high 1O2 quantum yield up to 0.93 and a fluorescence turn-on effect in mitochondria. Upon white light irradiation, the two mitochondria-targeting AIEgens exhibit a highly efficient photodynamic ablation of HeLa cells as well as excellent photodynamic inactivation of both Gram-positive S. aureus and Gram-negative E. coli. The time-dependent density functional theory (TD-DFT) results indicate that compared to TPEPy-PF6, TPEPy-I can easily produce the triplet state that is a prerequisite for 1O2 formation. Moreover, the positive effect of iodide anions gives TPEPy-I a higher photodynamic efficacy in cancer cell ablation and bacterial inactivation as compared with TPEPy-PF6.