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

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.