Biological\nUptake, Distribution, and Depuration of\nRadio-Labeled Graphene in Adult Zebrafish: Effects of Graphene Size\nand Natural Organic Matter

The\nexciting commercial application potential of graphene materials\nmay inevitably lead to their increasing release into the environment\nwhere they may pose ecological risks. This study focused on using\ncarbon-14-labeled few-layer graphene (FLG) to determine whether the\nsize of graphene plays a role in its uptake, depuration, and biodistribution\nin adult zebrafish. After 48 h exposure to larger FLG (L-FLG) at 250\nμg/L, the amount of graphene in the organism was close to 48\nmg/kg fish dry mass, which was more than 170-fold greater than the\nbody burden of those exposed to the same concentration of smaller\nFLG (S-FLG). The amount of uptake for both L-FLG and S-FLG increased\nby a factor of 2.5 and 16, respectively, when natural organic matter\n(NOM) was added in the exposure suspension. While the L-FLG mainly\naccumulated in the gut of adult zebrafish, the S-FLG was found in\nboth the gut and liver after exposure with or without NOM. Strikingly,\nthe S-FLG was able to pass through the intestinal wall and enter the\nintestinal epithelial cells and blood. The presence of NOM increased\nthe quantity of S-FLG in these cells. Exposure to L-FLG or S-FLG also\nhad a significantly different impact on the intestinal microbial community\nstructure.