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USGS · 70206149

Three-layered silver nanoparticles to trace dissolution and association to a green alga

Dominic Ponton·Marie Noele Croteau·Samuel N Luoma·Sahar Pourhoseini·Ruth Merrifield·Jamie Lead
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Abstract

Core-shell silver nanoparticles (NPs) consisting of an inner Ag core and successive layers of Au and Ag (Ag@Au@Ag) were used to measure the simultaneous association of Ag NPs and ionic Ag by the green alga Chlamydomonas (C.) reinhardtii. Dissolution of the inner Ag core was prevented by a gold (Au) layer, while the outer Ag layer was free to dissolve. In short term experiments, we exposed C. reinhardtii to a range of environmentally realistic Ag concentrations added as AgNO3 or as NPs. Results provide three lines of evidence for the greater cell-association of NPs compared to dissolved Ag over the concentration range tested, assuming that cell-association comprises both uptake and adsorption. First, the cell-association rate constants (kuw) for total Ag (AgNP+D), NPs (AgNP) and AuNP were similar and 2.2-fold higher than the one from AgD exposure, suggesting predominant association of the particles over the dissolved form. Second, model calculations based upon Ag fluxes suggested that only 6-33% of algal burden was from AgD. Thirdly, the significantly lower AgNP/Au ratio measured with the algae after exposure (2.1 ± 0.1) compared to the AgNP/Au ratio of the NPs in the media (2.47 ± 0.05) suggests cell-association of NPs depleted in Ag. Core-shell NPs provide an innovative tool to understand NP behavior and to directly delineate Ag accumulation from ion and NPs in aquatic systems.

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Dominic Ponton, Marie Noele Croteau, Samuel N Luoma, Sahar Pourhoseini, Ruth Merrifield, Jamie Lead. 2019-07-26. Three-layered silver nanoparticles to trace dissolution and association to a green alga. https://doi.org/10.1080/17435390.2019.1640912

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