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      Effect of silver nanoparticles on the standard soil arthropod Folsomia candida ( Collembola) and the eukaryote model organism Saccharomyces cerevisiae

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          Abstract

          Background

          Because of their antimicrobial properties, silver nanoparticles (AgNPs) have been widely used and have come into contact with the environment. In the present work, an effect of AgNPs on a standard soil organism, Folsomia candida, was studied (in comparison to silver nitrate) focusing on molecular and cellular alterations as ecotoxicological endpoints.

          Results

          At the molecular level, an up-regulation of metallothionein-containing protein ( MTC) mRNA in AgNP-treated groups indicated toxic heavy metal stress effects caused by the release of silver ions from AgNPs, which is similar to animal groups treated with silver nitrate. Alteration of the steady-state level of glutathione S-transferase ( GST) mRNA was detected in animal treated with AgNPs and AgNO 3. At the cellular level, the relation between GST activity and the size of the glutathione (GSH) was examined. Change of GST activity from different animal groups was not significant, whereas the GSH pool (reduced and oxidized forms) decreased with increasing concentration of AgNPs. In order to obtain direct evidence whether AgNPs cause oxidative stress, treated animals were incubated with the non-fluorescent probe, 2′,7′-dichlorodihydrofluorescein diacetate (DCFH-DA). A fluorescence signal was observed in both AgNPs- and AgNO 3-treated groups pointing to the production of reactive species (RS). Since RS formation in F.candida is difficult to quantify, yeast strain BY4742 (wild-type) and mutants lacking of oxidative stress-related protective enzymes were exploited as a further eukaryote model organism. AgNPs and AgNO 3 were found to also affect growth of yeast and induced oxidative stress.

          Conclusions

          An effect of AgNPs on Collembola and yeast strains is similar to the one from AgNO 3. However, AgNPs is less toxic due to the slow release of silver ions. In summary, the toxic effect of AgNPs on F. candida is caused by the combination of the release of silver ions from AgNPs and the formation of reactive species.

          Electronic supplementary material

          The online version of this article (doi:10.1186/s12302-016-0095-4) contains supplementary material, which is available to authorized users.

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          Most cited references 34

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          Redox environment of the cell as viewed through the redox state of the glutathione disulfide/glutathione couple.

          Redox state is a term used widely in the research field of free radicals and oxidative stress. Unfortunately, it is used as a general term referring to relative changes that are not well defined or quantitated. In this review we provide a definition for the redox environment of biological fluids, cell organelles, cells, or tissue. We illustrate how the reduction potential of various redox couples can be estimated with the Nernst equation and show how pH and the concentrations of the species comprising different redox couples influence the reduction potential. We discuss how the redox state of the glutathione disulfide-glutathione couple (GSSG/2GSH) can serve as an important indicator of redox environment. There are many redox couples in a cell that work together to maintain the redox environment; the GSSG/2GSH couple is the most abundant redox couple in a cell. Changes of the half-cell reduction potential (E(hc)) of the GSSG/2GSH couple appear to correlate with the biological status of the cell: proliferation E(hc) approximately -240 mV; differentiation E(hc) approximately -200 mV; or apoptosis E(hc) approximately -170 mV. These estimates can be used to more fully understand the redox biochemistry that results from oxidative stress. These are the first steps toward a new quantitative biology, which hopefully will provide a rationale and understanding of the cellular mechanisms associated with cell growth and development, signaling, and reductive or oxidative stress.
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            Silver nanoparticles: partial oxidation and antibacterial activities.

            The physical and chemical properties of silver nanoparticles that are responsible for their antimicrobial activities have been studied with spherical silver nanoparticles (average diameter approximately 9 nm) synthesized by the borohydride reduction of Ag+ ions, in relation to their sensitivity to oxidation, activities towards silver-resistant bacteria, size-dependent activities, and dispersal in electrolytic solutions. Partially (surface) oxidized silver nanoparticles have antibacterial activities, but zero-valent nanoparticles do not. The levels of chemisorbed Ag+ that form on the particle's surface, as revealed by changes in the surface plasmon resonance absorption during oxidation and reduction, correlate well with the observed antibacterial activities. Silver nanoparticles, like Ag+ in the form of AgNO3 solution, are tolerated by the bacteria strains resistant to Ag+. The antibacterial activities of silver nanoparticles are related to their size, with the smaller particles having higher activities on the basis of equivalent silver mass content. The silver nanoparticles aggregate in media with a high electrolyte content, resulting in a loss of antibacterial activities. However, complexation with albumin can stabilize the silver nanoparticles against aggregation, leading to a retention of the antibacterial activities. Taken together, the results show that the antibacterial activities of silver nanoparticles are dependent on chemisorbed Ag+, which is readily formed owing to extreme sensitivity to oxygen. The antibacterial activities of silver nanoparticles are dependent on optimally displayed oxidized surfaces, which are present in well-dispersed suspensions.
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              Exposure Modeling of Engineered Nanoparticles in the Environment

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                Author and article information

                Contributors
                +49 2418027260 , panwad.sillapawattana@rwth-aachen.de
                Martin.Gruhlke@rwth-aachen.de
                andreas.schaeffer@bio5.rwth-aachen.de
                Journal
                Environ Sci Eur
                Environ Sci Eur
                Environmental Sciences Europe
                Springer Berlin Heidelberg (Berlin/Heidelberg )
                2190-4707
                2190-4715
                4 November 2016
                4 November 2016
                2016
                : 28
                : 1
                Affiliations
                [1 ]Institute for Environmental Research (Biology V), RWTH Aachen University, Worringerweg 1, D-52074 Aachen, Germany
                [2 ]Institute for Plant Physiology (Biology III), RWTH Aachen University, Worringerweg 1, D-52074 Aachen, Germany
                Article
                95
                10.1186/s12302-016-0095-4
                5097105
                © The Author(s) 2016

                Open AccessThis article is distributed under the terms of the Creative Commons Attribution 4.0 International License ( http://creativecommons.org/licenses/by/4.0/), which permits unrestricted use, distribution, and reproduction in any medium, provided you give appropriate credit to the original author(s) and the source, provide a link to the Creative Commons license, and indicate if changes were made.

                Funding
                Funded by: The Ministry of Science and Technology, Thailand
                Categories
                Research
                Custom metadata
                © The Author(s) 2016

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