The in vitro and in vivo toxicity of graphene quantum dots.

Graphene quantum dots (GQD) generate intrinsic fluorescence, and improves aqueous stability of graphene oxide (GO) while maintaining wide chemical adaptability and high adsorption capacity. Despite GO's remarkable advantages in bio-imaging, bio-sensing and other biomedical applications, its biosafety issues are still unclear. Here we report a detailed and systematic study on the in vitro and in vivo toxicity of GQD. The GQD sample was prepared through a facile oxidation approach and fully characterized by means of AFM, TEM, FTIR, XPS and elemental analysis. In vitro experiments showed that GQD exhibits very low cytotoxicity owing to its ultra-small size and high oxygen content. Then, the in vivo biodistribution experiment of GQD revealed no material accumulation in main organs of mice and fast clearance of GQD through kidney. In order to mimic clinic drug administration, mice were injected with GQD and GO (as comparison) multiple times for in vivo toxicity tests. We found that GQD showed no obvious influence on mice owing to its small size, while GO appeared toxic, even caused death to mice due to GO aggregation inside mice. In brief, GQD possesses no obvious in vitro and in vivo toxicity, even under multi-dosing situation.