Graphene Oxide Nanosheets as Direct Photosensitizers for Photodynamic Therapy in a Size-Dependent Manner

Photodynamic therapy (PDT) has shown great potential in anticancer treatment. Photosensitizer is a key element determining the efficiency of PDT, but its practical use is highly limited by some critical problems, such as low photostability and poor solubility. As such, developing novel photosensitizers is of great significance and importance for PDT. In this work, we report the size-dependent photodynamic effect of graphene oxide (GO) nanosheets, which are commonly used as carriers for drug delivery. GO (200 µg/mL) with a large size up to ∼3500 nm showed little cytotoxicity to HSC-3 cells (oral squamous cell carcinoma cell line) but caused the cell viability down to 8% under NIR irradiation due to the robust generation of intracellular reactive oxygen species (ROS). Large GO-induced ROS generation is also significant even under hypoxia. Animal study shows that large GO even induced tumor ablation directly under a single NIR irradiation. Our findings indicate that GO is much more than a carrier but can also be a great photosensitizer when its size is large enough. This work paves the way for the potential applications of GO as the photosensitizer in PDT.