Keywords: 
• graphene /
• biological toxicology /
• cytotoxicity /
• influencing factors /
• toxicity mechanism

Abstract: Graphene, which is an emerging nanomaterial with unique electrical and optical properties, large specific surface area and the potential biological compatibility, has been widely applied in various fields, including materials and electronic industries, energy source, environmental science and biomedicine. Meanwhile, the environmental behaviors and biological toxicity of graphene also have attracted extensive attentions. This review mainly made a summary about the biological toxicity, cytotoxicity, and related influence factors and toxicity mechanisms of graphene. For those researches about toxicity of graphene, the materials enter into the organisms mainly through intratracheal instillation, inhalation, intravenous injection, intraperitoneal injection and oral administration. The intracellular graphene can cross through the mechanical barrier, blood-brain barrier and blood-placental barrier, and thus accumulate in the lung, liver, spleen, or other organs, so ultimately cause acute or chronic injuries. To date, the researches about the toxicity mechanisms of graphene mainly focused on oxidative stress, mitochondrial damage, DNA damage, inflammation, apoptosis and associated signaling pathway. Besides, the physicochemical characteristics of graphene, including its size, surface structure and functional groups, also have been reported to be connected with its toxicity in biological systems. Finally, the limitation of researches on graphene toxicity is pointed out and the prospect and development of researches on graphene toxicity is put forward. In conclusion, this review provides theoretical guidance for the safe application of graphene materials.