Synthesis Of A Far Red/Near-Infrared Fluorescent Photosensitizer With Aggregation-Induced Emission Characteristics And Application In Imaging And Photodynamic Killing Of Bacteria

Photodynamic therapy(PDT),which utilizes photosensitizers(PSs)to kill bacteria by producing reactive oxygen species(ROS)in the presence of white light irradiation,appears to be an innovative approach for antibacterial treatment.PDT owns superiorities of low toxicity and minor side effects for bacterial therapy.Furthermore,PDT can avoid the development of resistant strains.PSs with aggregation-induced emission(AIE)characteristics have gained raising attention among researchers.Contrary to aggregation-caused quenching(ACQ),AIE luminogens(AIEgens)are hardly emissive in solution but intensely emissive in the aggregated state.AIEgens not only possess high fluorescence intensity,but also bring about enhanced ROS generation efficiency and kill bacteria upon light irradiation.Excellent attributes of AIEgens make them conducive as dual-functional probes for both imaging and image-guided PDT of bacteria.In this work,we developed a novel AIEgen,AIE-TEA,which can be applied to farred/near-infrared(FR/NIR)imaging and PDT of bacteria.AIE-TEA emits in the FR/NIR(600–800 nm)region.The fluorescence intensity of the AIE-TEA gradually builds up with the increase of water fraction in acetone/water mixtures,which indicates that the AIE-TEA possesses excellent AIE characteristics.AIE-TEA,which is with the positively charged quaternary ammonium salt structure,can bind to S.aureus via electrostatic interaction and conduct imaging of S.aureus selectively.E.coli own complicated envelope structure which acts as an available shield against the foreign materials,thus,AIE-TEA cannot bind to E.coli.On account of water solubility of the AIE-TEA,the background emission of unbound the AIE-TEA in water solution is considered negligible and the imaging of bacteria can be simplified by wash-free process.Moreover,AIE-TEA can generate ROS under white light irradiation with efficient ROS quantum yield of up to 83%,bring about damage and conduct PDT of bacteria.20 ?M of the AIE-TEA is able to kill the vast majority of S.aureus and 51% of E.coli under white light irradiation.The killing effect of the AIE-TEA on S.aureus is better than E.coli.Combined utilization of imaging and PDT of bacteria provides new opportunities for the treatment of bacterial infections.