A graphene quantum dot photodynamic therapy agent with high singlet oxygen generation

Clinical applications of current photodynamic therapy (PDT) agents are often limited by their low singlet oxygen ( 1 O 2 ) quantum yields, as well as by photobleaching and poor biocompatibility. Here we present a new PDT agent based on graphene quantum dots (GQDs) that can produce 1 O 2 via a multistate sensitization process, resulting in a quantum yield of ~1.3, the highest reported for PDT agents. The GQDs also exhibit a broad absorption band spanning the UV region and the entire visible region and a strong deep-red emission. Through in vitro and in vivo studies, we demonstrate that GQDs can be used as PDT agents, simultaneously allowing imaging and providing a highly efficient cancer therapy. The present work may lead to a new generation of carbon-based nanomaterial PDT agents with overall performance superior to conventional agents in terms of 1 O 2 quantum yield, water dispersibility, photo- and pH-stability, and biocompatibility. Photosensitisers are used in cancer therapy to promote the formation of reactive oxygen species on irradiation with light. Here, the authors present a graphene quantum dot photosensitiser with a singlet oxygen quantum yield of approximately 1.3, and investigate its in vitro and in vivo applications