Nanosilver-enhanced AIE photosensitizer for simultaneous bioimaging and photodynamic therapy

Abstract

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.