Effects of Aqueous Exposure to Silver Nanoparticles of Different Sizes in Rainbow Trout

Tessa M Scown,Charles R Tyler,Ronny Van Aerle,Teresa F Fernandes,Eduarda M Santos,Blair D Johnston,Vicki Stone,Mark Jepson,Jamie R Lead,Birgit Gaiser,Mohammed Baalousha,Svetlin Mitov

doi:10.1093/toxsci/kfq076

Abstract

Despite increasing application of silver nanoparticles (NPs) in industry and consumer products, there is still little known about their potential toxicity, particularly to organisms in aquatic environments. To investigate the fate and effects of silver NPs in fish, rainbow trout (Oncorhynchus mykiss) were exposed via the water to commercial silver particles of three nominal sizes: 10 nm (N(10)), 35 nm (N(35)), and 600-1600 nm (N(Bulk)), and to silver nitrate for 10 days. Uptake into the gills, liver, and kidneys was quantified by inductively coupled plasma-optical emission spectrometry, and levels of lipid peroxidation in gills, liver, and blood were determined by measurements of thiobarbituric acid reactive substances. Expression of a suite of genes, namely cyp1a2, cyp3a45, hsp70a, gpx, and g6pd, known to be involved in a range of toxicological response to xenobiotics was analyzed in the gills and liver using real-time PCR. Uptake of silver particles from the water into the tissues of exposed fish was low but nevertheless occurred for current estimated environmental exposures. Of the silver particles tested, N(10) were found to be the most highly concentrated within gill tissues and N(10) and N(Bulk) were the most highly concentrated in liver. There were no effects on lipid peroxidation in any of the tissues analyzed for any of the silver particles tested, and this is likely due to the low uptake rates. However, exposure to N(10) particles was found to induce expression of cyp1a2 in the gills, suggesting a possible increase in oxidative metabolism in this tissue.

Highlights

Current growth in the nanotechnology industry and the increasing numbers of products making use of the unusual properties of engineered nanoparticles (NPs) is becoming extremely important in the global economy
Zeta potential measurements of all silver particle types in HPLCgrade water suggested that the particles had a high propensity for aggregation (Table 1), which was confirmed by hydrodynamic diameter measurements of the particles
It is difficult to speculate on the mechanism of action of cyp1a2 in the gills as it is unknown whether the effects seen are as a result of exposure to the silver NPs, silver ions, or a combination of both

Summary

Introduction

Current growth in the nanotechnology industry and the increasing numbers of products making use of the unusual properties of engineered nanoparticles (NPs) is becoming extremely important in the global economy. Navarro et al (2008) examined the rate of photosynthesis in Chlamydomonas reinhardtii exposed to silver NPs or silver ions in both the presence and the absence of cysteine (which binds free silver ions) and showed that silver NPs were more toxic than silver ions, based on the concentration of ions present, requiring a higher concentration of cysteine to eliminate the toxicity These findings suggest that interactions between the algae and the NPs may enhance the release of silver ions, in turn suggesting that the NPs acted as an effective delivery vehicle for silver ions

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