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

Ryo Sekine,Kanupriya Khurana,Krasimir Vasilev,Enzo Lombi,Erica Donner

doi:10.3109/17435390.2014.994570

Ryo Sekine, Kanupriya Khurana + Show 3 more

Open Access

https://doi.org/10.3109/17435390.2014.994570

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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 110mAg 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.

Highlights

Silver is a naturally occurring metal that has been widely used throughout history in the form of ornaments, coins and utensils (Purcell and Peters, 1998, Chernousova and Epple, 2013)
The P. subcapitata ecotoxicity test results for K2Cr2O7 and dissolved Ag determined following the standard OECD test protocol are shown in Figures S1 and S2, respectively
Standards prepared in acidified OECD media (2% HNO3 (v/v)) deviated by < 2% from the standards prepared in acidified water, which is within instrumental error

Summary

Introduction

Silver is a naturally occurring metal that has been widely used throughout history in the form of ornaments, coins and utensils (Purcell and Peters, 1998, Chernousova and Epple, 2013). It has found extensive applications in the photographic, electronic and medical industries and more recently, in a rapidly expanding range of silver nanotechnology based ‘antibacterial’ consumer products. 2013), silver nanoparticles (Ag-NPs) are the most commonly found NPs in consumer products; with a wide diversity of marketed applications in clothing, household appliances and personal care products for example. While previous research has significantly advanced our understanding of silver compounds in the environment (e.g. see editorials (Andren and Armstrong, 1999, Gorsuch and Klaine, 1998) and references therein), renewed concerns have been raised due to the increasing commercialization of Ag-based engineered nanomaterials (ENMs), in relation to the potential for nanoparticle-specific toxicity (Navarro et al, 2008)

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