Respiratory toxicity of few-layer graphene (FLG)

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As the use of graphene and related materials is still expected to increase in terms of industrial applications, the potential toxicity of these nanomaterials remains a major issue, especially for workers. In this joint study [1]  from the University of Nanjing (China) and the National Institute of Standards and Technology (USA), radio-labeled Few-Layer Graphene (FLG) was used to investigate the in vivo biodistribution of this nanomaterial in mice.

Figure 1: Biodistribution and clearance of 14C-graphene in mice after A) intratracheal instillation or B) oral gavage at different time points. Reprinted with permission from Particle and Fibre Toxicology 13, 7 (2016). Creative Commons license.

The study [1] compared two routes of exposure, the respiratory one with a single intratracheal instillation and the ingestion route by gavage (-see Fig. 1). FLG was synthesized from a 14C-containing source, in order to ensure that the radioactive label was included in the carbon network, and not simply grafted. The results revealed that FLG was fully eliminated in the feces in 48 hrs after administration by gavage. However, Four weeks after pulmonary administration, 47% of the FLG was still present in the lungs, with only very limited transfer to different organs such as the liver. Authors reported the absence of pulmonary toxicity at day 28. These results confirm earlier work with intrinsically radio-labelled carbon nanotubes, including the absence of nanoparticles in the urine. However, this raises again the question of the possible detachment of the radio-label when the latter is not directly included in the carbon network, which could possibly alter the observed FLG biodistribution.