Biological Uptake and Depuration of Radio-labeled Graphene byDaphnia magna

Abstract

Graphene layers are potential candidates in a large number of applications. However, little is known about their ecotoxicological risks largely as a result of a lack of quantification techniques in complex environmental matrices. In this study, graphene was synthesized by means of graphitization and exfoliation of sandwich-like FePO4/dodecylamine hybrid nanosheets, and (14)C was incorporated in the synthesis. (14)C-labeled graphene was spiked to artificial freshwater and the uptake and depuration of graphene by Daphnia magna were assessed. After exposure for 24 h to a 250 μg/L solution of graphene, the graphene concentration in the organism was nearly 1% of the organism dry mass. These organisms excreted the graphene to clean artificial freshwater and achieved roughly constant body burdens after 24 h depuration periods regardless of the initial graphene exposure concentration. Addition of algae and humic acid to water during the depuration period resulted in release of a significant fraction (>90%) of the accumulated graphene, but some still remained in the organism. Accumulated graphene in adult Daphnia was likely transferred to the neonates. The uptake and elimination results provided here support the environmental risk assessment of graphene and the graphene quantification method is a powerful tool for additional studies.

Degradation of 14C-labeled few layer graphene via Fenton reaction: Reaction rates, characterization of reaction products, and potential ecological effects

“…Synthesis, purification, and characterization of 14 C-labeled FLG 14 C-labeled FLG was synthesized as described in our previous study (Guo et al, 2013). A full description of synthesis process and characterization of 14 C-labeled FLG is provided in the Supplementary Information (SI) and summarized here.…”

“…To measure potential carbon-14 impurities in FLG, the dispersed FLG were extracted using dichloromethane and n-hexane mixtures. Analysis of the extracts using liquid scintillation counting (LSC) and gas chromatographymass spectrometry (GCeMS) did not show a significant increase in the radioactivity or obvious chemical peaks in GCeMS chromatograms of the extracted solutions, indicating that carbon-14 byproducts were not formed from the synthesis, purification, or dispersion processes of FLG (Guo et al, 2013).…”

“…This step was repeated three times. We demonstrated in our previous study that this procedure can effectively minimize the contributions from the attached FLG to the total mass of FLG associated with the D. magna (Guo et al, 2013). Then, the D. magna from each container were added to scintillation vials with 3 mL of Gold Star cocktail, ultrasonicated for 20 min (100 W, P ¼ 7.52 J s À1 ), allowed to sit for at least 24 h in the dark at room temperature, and then analyzed using LSC.…”

“…Since the application of graphene and its derivate has been greatly developed, it is inevitable that graphene will be released into the environment during the production and usage of graphene-enabled consumer products. It has been shown that graphene can induce cytotoxic effects such as cell membrane damage and bacterial toxicity and genotoxic effects on mammalian cells (Akhavan and Ghaderi, 2010;Bianco, 2013;Yang et al, 2013Yang et al, , 2010 and can accumulate in Daphnia magna (Guo et al, 2013).…”

“…In contrast, the 14 C isotope, a long-life radioactive isotope, is a sensitive tracer and 14 C-isotopic quantification methods can overcome the limitations described above for other techniques. 14 C-labeling has been applied to quantitatively measure the biodistribution of CNMs (Georgin et al, 2009;Guo et al, 2013;Petersen et al, 2009Petersen et al, , 2008Petersen et al, , 2011a. Recently, 14 C-labeling was also applied to study the microbial degradation of multiwall carbon nanotubes under complex reaction conditions (Zhang et al, 2013).…”