The toxicity of graphene quantum dots

Recently, there has been a rapidly expanding interest in a new nano material, graphene quantum dots, owing to its profound potential in various advanced applications. Despite its exciting application outlook, the toxicology of the material has to be well addressed before its practical use in the highly prospective areas-especially for bio-applications such as bio-sensing, bio-imaging and nanomedicine (e.g. drug delivery). This review provides a comprehensive account of the current research status regarding the toxicity of graphene quantum dots (GQDs), including raw GQDs, chemically doped GQDs and chemically functionalized GQDs. It summarises the existing tests on both in vivo and in vitro toxicity. Important topics including the uptake mechanism by cells and parameters governing the toxicity of GQDs (such as concentration, methods of synthesis, particle size, surface chemistry and chemical doping) are discussed. It also covers demonstrations on toxicity regulation of GQDs via chemical modification, as a toxicity mechanism via generation of reactive oxygen species (ROS) by some GQDs is also evident. Based on the evaluation of the current research status, possible future perspectives are also suggested.