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| 2. |
- Kroll, A., et al.
(författare)
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Mixed messages from benthic microbial communities exposed to nanoparticulate and ionic silver: 3D structure picks up nano-specific effects, while EPS and traditional endpoints indicate a concentration-dependent impact of silver ions
- 2016
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Ingår i: Environmental Science and Pollution Research. - : Springer Science and Business Media LLC. - 0944-1344 .- 1614-7499. ; 23:5, s. 4218-4234
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Tidskriftsartikel (refereegranskat)abstract
- Silver nanoparticles (AgNP) are currently defined as emerging pollutants in surface water ecosystems. Whether the toxic effects of AgNP towards freshwater organisms are fully explainable by the release of ionic silver (Ag+) has not been conclusively elucidated. Long-term effects to benthic microbial communities (periphyton) that provide essential functions in stream ecosystems are unknown. The effects of exposure of periphyton to 2 and 20 mu g/L Ag+ (AgNO3) and AgNP (polyvinylpyrrolidone stabilised) were investigated in artificial indoor streams. The extracellular polymeric substances (EPS) and 3D biofilm structure, biomass, algae species, Ag concentrations in the water phase and bioassociated Ag were analysed. A strong decrease in total Ag was observed within 4 days. Bioassociated Ag was proportional to dissolved Ag indicating a rate limitation by diffusion across the diffusive boundary layer. Two micrograms per liter of AgNO3 or AgNP did not induce significant effects despite detectable bioassociation of Ag. The 20-mu g/L AgNO3 affected green algae and diatom communities, biomass and the ratio of polysaccharides to proteins in EPS. The 20-mu g/L AgNO3 and AgNP decreased biofilm volume to about 50 %, while the decrease of biomass was lower in 20 mu g/L AgNP samples than the 20-mu g/L AgNO3 indicating a compaction of the NP-exposed biofilms. Roughness coefficients were lower in 20 mu g/L AgNP-treated samples. The more traditional endpoints (biomass and diversity) indicated silver ion concentration-dependent effects, while the newly introduced parameters (3D structure and EPS) indicated both silver ion concentration-dependent effects and effects related to the silver species applied.
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- Matzke, Marianne, et al.
(författare)
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Toxicity of differently sized and coated silver nanoparticles to the bacterium Pseudomonas putida: risks for the aquatic environment?
- 2014
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Ingår i: Ecotoxicology. - : Springer Science and Business Media LLC. - 0963-9292 .- 1573-3017. ; 23:5, s. 818-829
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Tidskriftsartikel (refereegranskat)abstract
- Aim of this study was to describe the toxicity of a set of different commercially available silver nanoparticles (AgNPs) to the gram-negative bacterium Pseudomonas putida (growth inhibition assay, ISO 10712) in order to contribute to their environmental hazard and risk assessment. Different AgNP sizes and coatings were selected in order to analyze whether those characteristics are determinants of nanoparticle toxicity. Silver nitrate was tested for comparison. In general Pseudomonas putida reacted very sensitive towards the exposure to silver, with an EC05 value of 0.043 mu g L-1 for AgNO3 and between 0.13 and 3.41 mu g L-1 for the different AgNPs (EC50 values 0.16 mu g L-1 for AgNO3, resp. between 0.25 and 13.4 mu g L-1 for AgNPs). As the ionic form of silver is clearly the most toxic, an environmental hazard assessment for microorganisms based on total silver concentration and the assumption that AgNPs dissolve is sufficiently protective. Neither specific coatings nor certain sizes could be linked to increasing or decreasing toxicity. The characterization of particle behavior as well as the total and dissolved silver content in the medium during the exposures was not possible due to the high sensitivity of Pseudomonas (test concentrations were below detection limits), indicating the need for further development in the analytical domain. Monitored silver concentrations in the aquatic environment span six orders of magnitude (0.1-120,000 ng L-1), which falls into the span of observed EC05 values and might hence indicate a risk to environmental bacteria.
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| 4. |
- Ribeiro, F., et al.
(författare)
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Silver nanoparticles and silver nitrate induce high toxicity to Pseudokirchneriella subcapitata, Daphnia magna and Danio rerio
- 2014
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Ingår i: Science of the Total Environment. - : Elsevier BV. - 0048-9697. ; 466, s. 232-241
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Tidskriftsartikel (refereegranskat)abstract
- Silver nanoparticles (AgNP) have gained attention over the years due to the antimicrobial function of silver, which has been exploited industrially to produce consumer goods that vary in type and application. Undoubtedly the increase of production and consumption of these silver-containing products will lead to the entry of silver compounds into the environment. In this study we have used Pseudokirchneriella subcapitata, Daphnia magna and Danio rerio as model organisms to investigate the toxicity of AgNP and AgNO3 by assessing different biological endpoints and exposure periods. Organisms were exposed following specific and standardized protocols for each species/endpoints, with modifications when necessary. AgNP were characterized in each test-media by Transmission Electron Microscopy (TEM) and experiments were performed by Dynamic Light Scattering (DIS) to investigate the aggregation and agglomeration behavior of AgNP under different media chemical composition and test-period. TEM images of AgNP in the different test-media showed dissimilar patterns of agglomeration, with some agglomerates inside an organic layer, some loosely associated particles and also the presence of some individual particles. The toxicity of both AgNO3 and AgNP differ significantly based on the test species: we found no differences in toxicity for algae, a small difference for zebrafish and a major difference in toxicity for Daphnia magna, (C) 2013 Elsevier B.V. All rights reserved.
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