Nanosilver-enhanced AIE photosensitizer for simultaneous bioimaging and photodynamic therapy

Theranostic photosensitizers which enable both disease diagnosis and effective treatment have recently received much attention towards personalized medicine. Herein, we report a multifunctional nanohybrid system using silver nanoparticles (AgNPs) to enhance the singlet oxygen generation (SOG) and fluorescence properties of a unique photosensitizer with aggregation-induced emission (AIE-PS) for simultaneous bioimaging and photodynamic therapy. To study the metal-enhancement effects, 4-mercaptobenzoic acid-capped AgNPs with well-controlled size (14, 40, and 80 nm) were synthesized to form nanohybrids with a specially designed red-emissive AIE-PS via simple electrostatic interactions. The careful control of the Ag nanoparticle concentration and the unique design of 80 nm AgNP@red-emissive AIE in this study resulted in a 10-fold enhancement in SOG, which is higher than other reported ME-SOG systems using similar plasmonic enhancers. Furthermore, the as-developed AgNP@AIE-PS nanohybrid exhibited improved photostability with negligible fluorescence quenching (5%), which is important for cell tracking. In addition, cytotoxity tests showed that these nanohybrids are biocompatibile with normal NIH-3T3 cells under dark conditions. Thus, they were employed for simultaneous imaging and photodynamic ablation of HeLa cancer cells. The results show that this brightly fluorescent AgNP@AIE-PS enabled about 4 times higher efficacy in PDT as compared to the control sample (i.e., 85% vs. 20% cell death) under low intensity white light irradiation (40 mW cm⁻²) for only 10 minutes, demonstrating its promising potential for advanced theranostic treatment in future nanomedicine.