Modeling the influence of physicochemical properties on gold nanoparticle uptake and elimination by Daphnia magna

Abstract

Monitoring the distribution and subsequent effects of nanoparticle contaminants in aquatic ecosystems will be pivotal to developing regulations that minimize their environmental footprint. The present study focused on the link between nanoparticle characteristics and Daphnia magna body burden using gold nanoparticles (AuNPs) with different size, shape, and surface charge configurations as model particles. Uptake followed first-order kinetics across the entire concentration range for all particles except the cationic rods, which demonstrated 2 distinct uptake patterns. Elimination followed the 2-compartment model for all particle configurations. Multiple regression analysis identified size and surface charge as controlling influences over AuNP uptake and elimination, whereas shape was regarded as inconsequential to both processes. Examination of the lumen-microvilli interface produced no evidence to indicate assimilation of the AuNPs used in the present study. Instead, these nanoparticles were restricted to the gut lumen and the carapace, where ingestion efficiency and adsorption were the primary determinants of total body burden. Models developed from the present data predict that D. magna will amass a higher body burden of larger cationic AuNPs at high concentration exposures and larger anionic AuNPs at low concentration exposures. A survey of the nanoparticle literature revealed that these trends were consistent with observations for certain nanomaterial exposures but could not be applied indiscriminately to all nanoparticle types and species.

An assessment of applicability of existing approaches to predicting the bioaccumulation of conventional substances in nanomaterials

“…However, TiO 2 NPs were shown to be bioaccumulative in D. magna in another kinetic modeling study in which the BCFs ranged from 2.40 Â 10 5 to 1.52 Â 10 6 L/kg. Our predicted BCF values for D. magna were also analogous to those predicted by others (Wray and Klaine 2015), who have implemented a similar kinetic approach producing BCF values ranging from 1460 to 47 700 L/kg in the same species. Our predicted BCF values for D. magna were also analogous to those predicted by others (Wray and Klaine 2015), who have implemented a similar kinetic approach producing BCF values ranging from 1460 to 47 700 L/kg in the same species.…”

Increasing evidence indicates low bioaccumulation of carbon nanotubes

“…However, absorption of nanomaterials by daphnids into tissues other than the gut tract has been observed for quantum dots 78 , carboxylated polystyrene beads 79 , and silver nanowires 80 . It is important to point out that a larger number of studies have not identified absorption of nanomaterials through the GI tract and into other tissues by daphnids: quantum dots 81 , fullerenes 82 , and gold nanoparticles 83, 84 . It is currently unclear why absorption into systemic circulation is observed in some studies but not others for tests with similar nanomaterials (e.g., quantum dots).…”

Nanomaterials in the aquatic environment: A European Union–United States perspective on the status of ecotoxicity testing, research priorities, and challenges ahead

“…Overall, NMs do not readily pass through the epithelial tissues in the gut tract or the surface skin [33], or may be slower to absorb compared with solutes, so further work on the time scales of such tests will be needed. Wray and Klaine [34] examined the influence of particle characteristics (AuNP surface charge, size, and shape) on total body burden in D. magna and found no evidence that AuNPs were absorbed across epithelial membranes, a result similar to other studies with carbon nanomaterial [23,35,36]. These authors discuss the possibility that a part of the ingested NPs may adsorb to gut structures (e.g., microvilli) and that these have a slower transport out of the gut compared with NPs that are not in contact with gut structures.…”