Uptake Route Altered the Bioavailability of Graphene in Misgurnus anguillicaudatus: Comparing Waterborne and Sediment Exposures

Numerous studies on the bioavailability of graphene-based nanomaterials relate to the water-only exposure route. However, the sediment exposure route should be the most important pathway for benthic organisms to ingest graphene, while to date little work on the bioavailability of graphene in benthic organisms has been explored. In this study, with the help of carbon-14-labeled few-layer graphene (14C-FLG), we quantificationally compared the bioaccumulation, biodistribution, and elimination kinetics of 14C-FLG in loaches via waterborne and sediment exposures. After 72 h of exposure, the accumulated 14C-FLG in loaches exposed via waterborne was 14.28 μg/g (dry mass), which was 3.18 times higher than that (4.49 μg/g) exposed via sediment. The biodistribution results showed that, compared to waterborne exposure, sediment exposure remarkably facilitated the transport of 14C-FLG from the gut into the liver, which made it difficult to be excreted. Although 14C-FLG did not cause significant hepatotoxicity, the disruption of intestinal microbiota homeostasis, immune response, and several key metabolic pathways in the gut were observed, which may be due to the majority of 14C-FLG being accumulated in the gut. Overall, this study reveals the different bioavailabilities of graphene in loaches via waterborne and sediment exposures, which is helpful in predicting its bioaccumulation capability and trophic transfer ability.