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Ageing, dissolution and biogenic formation of nanoparticles, how do these factors affect uptake kinetics of silver nanoparticles in earthworm?

Abstract

The soil represents an important environmental compartment that can be regarded as a final sink for metal nanoparticles including silver particles (Ag-NPs). Assessing realistic exposure scenarios, including bioavailability of Ag-NPs for soil organisms requires taking into account that Ag-NPs can undergo physico-chemical transformations, such as sulphidisation, before interacting with organisms. However, differentiating between uptake of true metal NPs and released ions is essential to assess the actual role of these two metal forms in toxicity overtime. The present study quantified toxicokinetic rate constants of particulate and ionic Ag in Eisenia fetida exposed to soil treated with pristine Ag-NP (50 nm), Ag2S-NP (20 nm), as an environmentally relevant form, and AgNO3 as an ionic control. Results showed that uptake and elimination rate constants of Ag in earthworms exposed to Ag-NP and AgNO3 were not significantly different from each other, whereas uptake of Ag2S-NPs was significantly lower. Interestingly, the biogenic formation of particulate Ag (~10 % of the total Ag accumulated overtime) in earthworms exposed to AgNO3 led to a kinetic pattern of particulate Ag similar to pristine Ag-NPs. SEM-EDX analysis confirmed the presence of particulate Ag in earthworms exposed to both Ag-NP and AgNO3, showing that these particles were different than those to which earthworms were exposed. We demonstrated that around 85 % of the Ag accumulated in the worms after exposure to Ag-NPs and AgNO3 was present as ions or as particles with size < 20 nm. Additionally, the low accumulation of the non-soluble, sulphidised form of nano-Ag, reflecting aged particles in the environment, confirms the importance of ionic uptake of Ag. This study clearly shows that the main form of uptake for Ag in earthworms is the ionic species, which stresses the fundamental need to use environmental relevant forms of metal NPs in performing ecotoxicological tests, because pristine NPs may behave completely different.

  • This article is part of the themed collection: ICEENN 2017
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Publication details

The article was received on 15 Dec 2017, accepted on 03 Apr 2018 and first published on 05 Apr 2018


Article type: Paper
DOI: 10.1039/C7EN01212H
Citation: Environ. Sci.: Nano, 2018, Accepted Manuscript
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    Ageing, dissolution and biogenic formation of nanoparticles, how do these factors affect uptake kinetics of silver nanoparticles in earthworm?

    M. Baccaro, A. K. Undas, J. de Vriendt, H. J. van den Berg, R. J. B. Peters and N. van den Brink, Environ. Sci.: Nano, 2018, Accepted Manuscript , DOI: 10.1039/C7EN01212H

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