A Versatile Near Infrared Light Triggered Dual-Photosensitizer for Synchronous Bioimaging and Photodynamic Therapy

Photodynamic therapy (PDT) based on Tm 3+ -activated up-conversion nanoparticles (UCNPs) can effectively eliminate tumor cells by triggering inorganic photosensitizers to generate cytotoxic reactive oxygen species (ROS) upon tissue penetrating near-infrared (NIR) light irradiation. However, the partial use of the emitted lights from UCNPs greatly hinders their application. Here we develop a novel dual-photosensitizer nanoplatform by coating mesoporous graphitic-phase carbon nitride (g-C 3 N 4 ) layer on UCNPs core, followed by attaching ultrasmall Au 25 nanoclusters and PEG molecules (named as [email protected] 3 N 4 –Au 25 -PEG). The ultraviolet–visible (UV–vis) light and the intensive near infrared (NIR) emission from UCNPs can activate g-C 3 N 4 and excite Au 25 nanoclusters to produce ROS, respectively, and thus realize the simultaneous activation of two kinds of photosensitizers for enhanced the efficiency of PDT mediated by a single NIR light excitation. A markedly higher PDT efficacy for the dual-photosensitizer system than any single modality has been verified by the enhanced ROS production and in vitro and in vivo results. By combining the inherent multi-imaging properties (up-conversion, CT, and MRI) of UCNPs, an imaging guided therapeutic platform has been built. As the first report of dual-inorganic-photosensitizer PDT agent, our developed system may be of high potential in future NIR light induced PDT application.