Abstract
Engineered nanoparticles are becoming increasingly incorporated into technology and consumer products. In 2014, over 300 tons of copper oxide nanoparticles were manufactured in the United States. The increased production of nanoparticles raises concerns regarding the potential introduction into the environment or human exposure. Copper oxide nanoparticles commonly release copper ions into solutions, which contribute to their toxicity. We quantified the inhibitory effects of both copper oxide nanoparticles and copper sulfate on C. elegans toxicological endpoints to elucidate their biological effects. Several toxicological endpoints were analyzed in C. elegans, including nematode reproduction, feeding behavior, and average body length. We examined three wild C. elegans isolates together with the Bristol N2 laboratory strain to explore the influence of different genotypic backgrounds on the physiological response to copper challenge. All strains exhibited greater sensitivity to copper oxide nanoparticles compared to copper sulfate, as indicated by reduction of average body length and feeding behavior. Reproduction was significantly reduced only at the highest copper dose, though still more pronounced with copper oxide nanoparticles compared to copper sulfate treatment. Furthermore, we investigated the effects of copper oxide nanoparticles and copper sulfate on neurons, cells with known vulnerability to heavy metal toxicity. Degeneration of dopaminergic neurons was observed in up to 10% of the population after copper oxide nanoparticle exposure. Additionally, mutants in the divalent-metal transporters, smf-1 or smf-2, showed increased tolerance to copper exposure, implicating both transporters in copper-induced neurodegeneration. These results highlight the complex nature of CuO nanoparticle toxicity, in which a nanoparticle-specific effect was observed in some traits (average body length, feeding behavior) and a copper ion specific effect was observed for other traits (neurodegeneration, response to stress).
Highlights
Nanoparticles (NPs), microscopic particles, with at least one dimension less than 100 nm, are increasingly incorporated into commercial products
CuO NPs could be interacting with the organic bacterial lysate components, and these agglomerates can subsequently be ingested by the nematodes
No Cu ions were detected when the CuO NPs were suspended in water, suggesting the CuO NPs were not dissolving in water
Summary
Nanoparticles (NPs), microscopic particles, with at least one dimension less than 100 nm, are increasingly incorporated into commercial products. NPs have high surface area to size ratios, conferring unique material properties compared to micron particles with the same chemical composition. CuO NPs are incorporated into several personal care and household products because of their bactericidal properties. The risk of environmental contamination is especially important for copper materials as Cu ions and CuO nanoparticles display toxicological responses towards aquatic species [4] and earthworms [5]. Organic acids found in natural environments affect CuO NP mobility and aggregation behavior via ligand-promoted dissolution [6]. The adsorption of organic acids to NPs surface results in dissolution and the release of metal ions [4]
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