Salinity-dependent silver nanoparticle uptake and transformation by Atlantic killifish (Fundulus heteroclitus) embryos

Abstract

We assessed the biodistribution and in situ speciation of sub-lethal concentrations of citrate-coated silver nanoparticles and dissolved silver within Fundulus heteroclitus embryos. Using a thorough physico-chemical characterization, we studied the role of salinity on both uptake and in situ speciation. The Ag uptake or adsorption on the chorion was reduced by 2.3-fold for Ag NPs, and 2.9-fold for AgNO₃ in estuarine water (10‰ ASW) compared to deionized water (0‰ ASW). Between 58% and 85% of the silver was localized on/in the chorion and formed patches between 20 and 80 µm. More than a physical barrier, the chorion was found to be a chemically reactive membrane controlling the in situ speciation of silver. A strong complexation of the Cit-Ag NPs with the thiolated groups of proteins or enzymes of the chorion was responsible for the oxidation of 48 ± 5% of the Ag⁰ into Ag^(I)-S species at 0‰ ASW. However, at 10‰ ASW, the presence of Cl⁻ ions at the surface of Ag NPs slow down this oxidation. For the dissolved silver, we observed that in deionized water 69 ± 7% of Ag⁺ taken up by the chorion was complexed by the thiolated molecules while the others 30 ± 3% were reduced into Ag⁰ likely via interaction with the hemiacetal-reducing ends of polysaccharides of the chorion.

• Chorion
• estuarine
• nanomaterial
• salinity
• speciation

Acknowledgements

The authors would like to thank Stella Marinakos for the NPs synthesis and characterization, Ty Lindberg for help with digestions, and Andreas Gondikas for ICP-MS assistance. The authors acknowledge the GDRi iCEINT (International Consortium for the Environmental implications of NanoTechnology) funded by the CNRS, as well as the ESRF and the French program committees for providing synchrotron beam time.

Declaration of interest

The authors report no conflicts of interest and are responsible for the content and writing of the paper. This material is based upon work supported by the NSF and the EPA under NSF Cooperative Agreement EF-0830093, CEINT. Any opinions, findings, conclusions or recommendations expressed in this material are those of the author(s) and do not necessarily reflect the views of the NSF, or the EPA. This work has not been subjected to EPA review and no official endorsement should be inferred. Additional financial supports were provided by the NSF CBET-1066781, and the EQUIPEX Nano-ID platform (ANR-10-EQPX-39-01).