Elsevier

Journal of Hazardous Materials

Volume 347, 5 April 2018, Pages 89-94
Journal of Hazardous Materials

Ecotoxicity of different-shaped silver nanoparticles: Case of zebrafish embryos

https://doi.org/10.1016/j.jhazmat.2017.12.060Get rights and content

Highlights

  • Toxic effect of flat and spherical silver nanoparticles on zebrafish embryos was evaluated.

  • Both types of silver nanoparticles appeared toxic to Danio rerio embryos.

  • Silver nanoplates induced higher toxicity than nanospheres and Ag+ ions for embryos.

Abstract

As the worldwide application of silver nanomaterials in commercial products increases every year, and concern about the environmental risks of such nanoparticles also grows. A clear understanding of how different characteristics of nanoparticles contribute in their toxic behavior to organisms are imperative for predicting and control nanotoxicity. Within our research, we investigated the toxic effect of two types of silver nanoparticles (spherical and flat Ag nanoparticles) on zebrafish (Danio rerio) embryos. Particular interest was paid to proper characterization of Ag nanoparticles initially and during the experiment. A proper test medium was found and used for ecotoxicity evaluation. The behavior of flat silver nanoparticles with respect to embryos of zebrafish was analyzed and compared to the ecotoxicity of silver ionic form (AgNO3). Both types of nanoparticles showed a more pronounced toxic effect to Danio rerio embryos than silver ions (AgNO3), while silver nanoplates were more harmful than Ag nanospheres. While previous investigations showed that toxicity of Ag nanoparticles can be explained by the presence of Ag+ in solution of silver nanoparticles, our results demonstrate that the harmful effects of nanosilver may be associated with silver nanoparticles themselves than with ionic silver released into solution.

Graphical abstract

Ecotoxicity order (zebrafish emryos): Ag nanoplates > Ag nanospheres > Ag+ ions.

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Introduction

The field of nanomaterials has experienced unprecedented growth during the last few years. Due to the unique properties of nanoparticles (NPs), they found wide commercial applications [1,2]. According to Vance et al. [2], the number of the products with the prefix "nano" in 2012 exceeded 1500 and in 2014 this number came close to 2000 units, while the silver nanoparticles (Ag NPs) represent 24% of the total production in nanotechnology industry. Subsequently, this NPs had received a great attention from the public and scientific communities. Silver NPs have been widely investigated as toxic materials for numerous organisms and cell lines [[3], [4], [5]]. Toxicity of Ag NPs is usually correlated with silver ions emission from the surface of NPs [[6], [7], [8], [9]]. On the other hand, Ag NPs might cause themselves a negative effect on life system due to specific properties of Ag NPs or a combined mechanism of toxicity due to the presence of both Ag+ ions and Ag NPs may take place [10,11].

Due to a small size and high surface area to volume ratio of NPs, they can strongly interact with life cells and demonstrate high toxicity to cells and tested animals [12]. Size-dependent toxicity of Ag NPs was shown in a large number of publications [[13], [14], [15]], they usually postulate that the NPs with smaller sizes cause more harmful effects to tested organisms and cell lines compared with larger particles. The role of other physical and chemical parameters is often not taken into consideration. However, European Centre for Ecotoxicity and Toxicity Of Chemicals (ECETOC) and the Organization for Economic Cooperation and Development (OECD) recommend to consider also other physicochemical characteristics in case of toxicity of NPs [[16], [17], [18]]. The shape (or morphology) of NPs, their surface area, size distribution and other parameters of NPs are the most prominent key factors that may determine the activity of NPs.

In this paper, we evaluated the toxicity of flat and spherical Ag NPs using zebrafish (Danio rerio) embryos as test organisms. The influence of NPs on the survival, hatching rate and morphogenesis of zebrafish embryos was analyzed. Toxicity of NPs was compared with the data for Ag+ ions and toxic effect of a solution with supernatant and stabilizers.

Section snippets

Chemicals

Silver perchlorate hydrate (AgClO4·H2O, 99%), silver nitrate (AgNO3, 99%), sodium borohydride (NaBH4, 98%), sodium citrate tribasic dihydrate (Na3Cit, 99.5%), sodium polyphosphate (PPNa, 96%), and polyvinylpyrrolidone (PVP, Mw. 360000) were purchased from Sigma-Aldrich. Sodium formate (HCOONa, 99%) was purchased from Merck, and hydrogen peroxide (H2O2, 30% aqueous solution) was obtained from ZAO «Baza №1 Chimreactiv».

Characterization

The absorption spectra of silver colloidal solutions were measured using a

Characterization of nanoparticles

UV–vis absorption spectra for two types of silver NPs are shown in Fig. 1a. The peak at 400 nm is observed. It is typical for spherical nanosilver NPs, which have only one SPR peak at about 400 nm [20]. The hydrosol of spherical Ag NPs has a yellow color. Triangular prismatic Ag NPs exhibit several peaks which indicate presence two sectional planes in crystal [19]. The hydrosol of silver nanoprisms has an intense blue color. Fig. 1b and c show the optical absorption spectra of the obtained

Conclusions

The aim of this study was to evaluate the influence of characteristics of Ag NPs on their toxicity. In particular, we observed the effect of Ag NPs with different morphology for Danio rerio embryos. According to the data obtained in this work, we have shown that the toxic effects of Ag NP in aquatic systems are closely related to the particle characteristics. Not only the size, but also other factors can influence the toxicity of Ag NPs, such as the surface characteristics of the particle and

Acknowledgments

The toxicity evaluation part of this research was supported by Russian Science Foundation (grant no. 14-50-00126). The part of this research related to preparation of nanomaterials was financially supported by the Ministry of Education and Science of the Russian Federation in the framework of Increase Competitiveness Program of NUST «MISiS» (No. К1-2015-045). E.V. Abkhalimov was financially supported by the Russian Foundation for Basic Research (Project no. 15-03-04854-a).

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