Analysis of fullerene‐C₆₀ and kinetic measurements for its accumulation and depuration in Daphnia magna

Abstract

A simple method for analyzing masses of water suspended fullerenes (nC60) in Daphnia magna by extracting to toluene and measuring by ultraviolet-vis spectrophotometry was developed. This method was used to assess bioaccumulation and depuration rates by daphnia after nC60 exposure in artificial freshwater. Accumulation was rapid during the first few hours, and based on accumulation modeling, 90% of the steady-state concentration was reached in 21 h. After exposure for 24 h to a 2 mg/L fullerene solution, the daphnia accumulated 4.5+/-0.7 g/kg wet weight, or 0.45% of the organism wet mass. Daphnids exposed to 2 mg/L fullerenes for 24 h eliminated 46 and 74% of the accumulated fullerenes after depuration in clean water for 24 and 48 h, respectively. Transmission electron microscopy revealed that the majority of the fullerenes present in the gut of daphnids were large agglomerates. The significant fullerene uptake and relatively slow depuration suggest that D. magna may play a role as a carrier of fullerene from one trophic level to another. Additionally, D. magna may impact the fate of suspended fullerene particles in aquatic ecosystems by their ability to pack fullerene agglomerates into larger particles than were found in the exposure water, and then excrete agglomerates that are not stable in water, causing them to settle out of solution. This process decreases fullerene exposure to other aquatic organisms in the water column but may increase exposure to benthic organisms in the sediment.

Methodological considerations for testing the ecotoxicity of carbon nanotubes and fullerenes: Review

“…Daphnia magna, for example, were shown previously to consume a lipid surface coating on SWNTs, thereby reducing the aqueous stability of the CNT [78]. Suspended fullerenes were also shown to be larger in the guts of Daphnia than in the initial solution, and the presence of Daphnia increased the fullerene settling rate during a 24-h interval [79]. Therefore, researchers are encouraged to assess the sizes of CNPs before and after experiments.…”

“…Given that settling of CNPs is common during aqueous exposures, researchers are encouraged to use Organisation for Economic Co-Operation and Development (OECD) methods to indicate a time-weighted mean if substantial settling has occurred [81]. Quantifying NPs in the aqueous phase has been conducted most commonly in experiments with C 60 fullerenes, because they can be measured readily after toluene extraction and then ultraviolet-visible (UV/vis) spectroscopy [79]. For CNTs, however, concentrations in the aqueous phase during ecotoxicity tests are often limited to nominal concentrations (the CNP mass that was sonicated initially).…”

“…Transmission electron microscopy has been used to identify fullerene aggregates in soil extracts from a soil spiked with 154 mg/kg fullerenes [91] and to investigate absorption of CNTs and fullerenes in Daphnia [69,79], Lumbriculus variegatus [92], and cells [93,94]. Numerous challenges are associated with using TEM to identify CNPs in tissues, including the lack of contrast for CNPs given that they are composed of the same element as the tissue and the resin used to make the samples; the challenge of finding these particles given their extremely low concentrations Identifies nanoparticles in tissues without additional sample processing Not specific to particle type, uncommon equipment [100] Chemothermal oxidation at 3758C x x Chemothermal oxidation at 3758C…”

“…Several procedures are available to identify fullerenes in Daphnia by extracting the fullerenes and then measuring absorbance of their characteristic peaks using UV/vis spectroscopy [79,102,103]. However, these approaches may not work with larger organisms in which these extraction techniques also remove large quantities of other biomolecules such as lipids, which may hinder the detection of the fullerenes by spectroscopic methods.…”

“…Uptake after oral administration in rats indicated that water-soluble 14 C 60 (generated by preparation of C 60 in saline containing 0.2% Tween 80) was minimal and that the administered C 60 was voided with feces [122]. Fullerenes were not readily absorbed by Daphnia magna based on microscopic examination of microvilli by TEM, and most fullerenes were present as large aggregates within the Daphnia gut lumen [79]. Additionally, fullerene accumulations within the gut lumen appeared to be limited by the size of the gut rather than the aqueous-phase concentration, again suggesting minimal systemic absorption into the organism.…”