Quantifying the adsorption of ionic silver and functionalized nanoparticles during ecotoxicity testing: Test container effects and recommendations

Abstract

Silver nanoparticles (Ag-NPs) are used in a wide variety of products, prompting concerns regarding their potential environmental impacts. To accurately determine the toxicity of Ag-NPs it is necessary to differentiate between the toxicity of the nanoparticles themselves and the toxicity of ionic silver (Ag) released from them. This is not a trivial task given the reactive nature of Ag in solution, and its propensity for both adsorption and photoreduction. In the experiments reported here, we quantified the loss of silver from test solutions during standard ecotoxicity testing conducted using a variety of different test container materials and geometries. This sensitive (110m)Ag isotope tracing method revealed a substantial underestimation of the toxicity of dissolved Ag to the green algae Pseudokirchneriella subcapitata when calculated only on the basis of the initial test concentrations. Furthermore, experiments with surface-functionalized Ag-NPs under standard algal growth inhibition test conditions also demonstrated extensive losses of Ag-NPs from the solution due to adsorption to the container walls, and the extent of loss was dependent on Ag-NP surface-functionality. These results hold important messages for researchers engaged in both environmental and human nanotoxicology testing, not only for Ag-NPs but also for other NPs with various tailored surface chemistries, where these phenomena are recognized but are also frequently disregarded in the experimental design and reporting.

Overcoming challenges in single particle inductively coupled plasma mass spectrometry measurement of silver nanoparticles

“…The initial signal drift in water was improved by increasing the sample stabilization time from 30 s to 90 s, but at Ag mass fractions ≤ 1 ng g −1 the response for Ag + in water was reduced compared to acidified standards (Fig. S3), possibly due to nonspecific analyte adsorption onto the sample vessel or sample introduction system of the ICP- MS [45, 46]. The response of Ag + in water was comparable to that in 2 % HNO 3 for mass fractions 2 ng g −1 Ag and greater.…”

Natural water as the test medium for Ag and CuO nanoparticle hazard evaluation: An interlaboratory case study

“…These losses may be attributable to sorption to the test vessel or to changes in silver speciation due to the influence of light (Kos et al, 2016;Malysheva et al, 2016;Sekine et al, 2015).…”

Influence of polyethylene microplastic beads on the uptake and localization of silver in zebrafish (Danio rerio)

“…The potential for metals to interact with MPs has been largely overlooked as plastics surfaces are considered to be relatively inert to aqueous metal cations (Ashton et al, 2010;Holmes et al, 2012). However, the adsorption of metal ions by plastic containers has been reported in ecotoxicological studies (Giusti et al, 1994;Fischer et al, 2007) and silver (Ag, used in the present study as a model metal contaminant), in particular, exhibits strong surface-binding characteristics which requires recognition and mitigation in experimental design (West et al, 1967;Sekine et al, 2015). Commonly used plastic pellets, including polyethylene (PE), polypropylene (PP) and polyvinyl chloride (PVC), deployed in the San Diego Bay area for up to one year accumulated different amounts of nine metals, with some metals (including Ni, Zn and Pb) not reaching saturation within the given timeframe (Rochman et al, 2014).…”