Grantee Research Project Results
Final Report: The Fate And Effects Of Nanosized Metal Particles Examined Along A Simulated Terrestrial Food Chain Using Genomic And Microspectroscopic Techniques
EPA Grant Number: R833335Title: The Fate And Effects Of Nanosized Metal Particles Examined Along A Simulated Terrestrial Food Chain Using Genomic And Microspectroscopic Techniques
Investigators: Unrine, Jason M. , Bertsch, Paul M. , Tsyusko, Olga V. , Neal, Andrew
Institution: Biotechnology and Biological Sciences Research Council , University of Kentucky
EPA Project Officer: Hahn, Intaek
Project Period: May 1, 2007 through October 31, 2010
Project Amount: $317,897
RFA: Exploratory Research: Nanotechnology Research Grants Investigating Environmental and Human Health Effects of Manufactured Nanomaterials: a Joint Research Solicitation-EPA, NSF, NIOSH, NIEHS (2006) RFA Text | Recipients Lists
Research Category: Nanotechnology , Safer Chemicals
Objective:
The overall objectives of this research were to: 1) investigate the relative roles of particle size and chemical composition in a series of nanosized metal particles (NPs) (specifically Cu, Ag, Au) in determining soil bioavailability and oral uptake in a model soil detritivore; 2) elucidate mechanisms governing gastrointestinal uptake, tissue distribution, retention and trophic transfer of nanosized Cu, Ag, and Au along a simulated terrestrial food chain; and 3) investigate interactions among size and chemical composition of NPs in determining bioavailability and toxic mode of action. These objectives are being met by testing the following hypotheses.
Hypotheses to be tested:
Hypothesis 1: The absorption and extent of redistribution of metal NPs among organ systems, as well as the extent of binding to macromolecules, decreases with increasing particle size.
Hypothesis 2: Metal NPs do not biomagnify regardless of particle size, but the particles are more bioaccumulative through trophic exposure than they are through direct exposure.
Hypothesis 3: The inherent toxicity of metal NPs is determined by interactions between chemical composition and particle size.
Hypothesis 4: Toxicity of metal NPs can be unrelated to the release of free metal ions.
Summary/Accomplishments (Outputs/Outcomes):
Hypothesis 1: We conditionally rejected this hypothesis. We have observed this effect only for smaller particles (4 versus 18 nm Au); however, when comparing 15 nm Ag to 30 nm Ag, we observed increasing uptake with increasing particle size on a mass basis. There are no consistent differences when comparing 20 nm to 55 nm Au, Cu, and Ag particles. There may be an optimal diameter for uptake by cells so that sometimes larger particles can be more bioavailable than smaller particles. It also is important to note that on a particle number basis, we always observe greater uptake for smaller particles, even though on a particle mass concentration basis we did not.
Hypothesis 2: We conditionally failed to reject this hypothesis. Our studies with trophic transfer of Au nanoparticles from earthworms to frogs showed that there was trophic dilution rather than biomagnification and that the particles were indeed more bioaccumulative through trophic exposure than direct exposure. In another study, however, we observed biomagnification when particles were transferred from plants to insect larvae.
Hypothesis 3: We reject this hypothesis. We saw little evidence of dramatic differences in toxicity based on particle size; however, particle composition seemed to be the driving factor in determining toxicity.
Hypothesis 4: We failed to reject this hypothesis. We have observed some evidence of reproductive toxicity in Eisenia fetida from Au particles and there is evidence from gene expression studies and x-ray absorption microspectroscopy that no free Au ions are released. Additionally, we have demonstrated that behavioral avoidance of Ag nanoparticle-containing soils is related to intact particles and not free ions.
Conclusions:
We have published six peer-reviewed journal articles, one book chapter, and two peer-reviewed conference proceedings; we also have three additional manuscripts in preparation. We expect a total of 11 peer-reviewed publications and one book chapter resulting from this award. We also have given numerous invited talks on our research and published numerous abstracts. We provided the first solid evidence that nanomaterials are bioavailable from soils and can be transmitted from one trophic level to the next. Our studies were considered groundbreaking and received considerable attention in the scientific and popular media. One study also provided the first evidence for biomagnification of nanoparticles in a terrestrial food chain. Given our findings that Ag nanoparticles were the most toxic, we focused on additional endpoints for Ag particles as well as comparing different particle sizes (15 and 30 nm) and surface functionalities (citrate, PVP and oleic acid). We found that reproductive toxicity of Ag nanoparticles in earthworms is far less than for AgNO3 and that reproductive responses are related to the release of the free Ag ion rather than direct particle effects. On the other hand, we have found that the most sensitive endpoint is behavioral avoidance of soils containing Ag nanoparticles, which occurs at concentrations 100X lower than for reproductive toxicity. Based on X-ray absorption spectroscopy data, we concluded that the responses were due to intact particles and not Ag ions released as a result of dissolution. We also confirmed that the avoidance was not an indirect effect of changes in microbial composition, thus providing the first evidence that organisms can actually sense nanomaterials. We also demonstrated that Ag nanoparticles cause changes in gene expression and cause oxidative damage to proteins in earthworms exposed at relatively low concentrations in soil.
Journal Articles on this Report : 6 Displayed | Download in RIS Format
Other project views: | All 17 publications | 7 publications in selected types | All 6 journal articles |
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Judy JD, Unrine JM, Bertsch PM. Evidence for biomagnification of gold nanoparticles within a terrestrial food chain. Environmental Science & Technology 2011;45(2):776-781. |
R833335 (2009) R833335 (Final) R834574 (2011) R834574 (Final) |
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Shoults-Wilson WA, Zhurbich OI, McNear DH, Tsyusko OV, Bertsch PM, Unrine JM. Evidence for avoidance of Ag nanoparticles by earthworms (Eisenia fetida). Ecotoxicology 2011;20(2):385-396. |
R833335 (2009) R833335 (Final) |
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Shoults-Wilson WA, Reinsch BC, Tsyusko OV, Bertsch PM, Lowry GV, Unrine JM. Role of particle size and soil type in toxicity of silver nanoparticles to earthworms. Soil Science Society of America Journal 2011;75(2):365-377. |
R833335 (2009) R833335 (Final) |
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Shoults-Wilson WA, Reinsch BC, Tsyusko OV, Bertsch PM, Lowry GV, Unrine JM. Effect of silver nanoparticle surface coating on bioaccumulation and reproductive toxicity in earthworms (Eisenia fetida). Nanotoxicology 2011;5(3):432-444. |
R833335 (2009) R833335 (Final) |
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Unrine JM, Hunyadi SE, Tsyusko OV, Rao W, Shoults-Wilson WA, Bertsch PM. Evidence for bioavailability of Au nanoparticles from soil and biodistribution within earthworms (Eisenia fetida). Environmental Science & Technology 2010;44(21):8308-8313. |
R833335 (2009) R833335 (Final) |
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Unrine JM, Tsyusko OV, Hunyadi SE, Judy JD, Bertsch PM. Effects of particle size on chemical speciation and bioavailability of copper to earthworms (Eisenia fetida) exposed to copper nanoparticles. Journal of Environmental Quality 2010;39(6):1942-1953. |
R833335 (2009) R833335 (Final) |
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Supplemental Keywords:
soil, ecological effects, bioavailability, cellular, metals, heavy metals, environmental chemistry, biology, analytical, absorption, adsorption, bioaccumulation, biomagnification, enzyme activity, genomics, gene expression, growth, mechanisms, oxidative stress, pharmacokinetics, proteomics, reproduction, transcriptomics, trophic transfer, , Scientific Discipline, Health, PHYSICAL ASPECTS, Biology, Risk Assessments, Health Risk Assessment, Physical Processes, Biochemistry, nanotechnology, human health risk, nanomaterials, nanoparticle toxicity, Health, PHYSICAL ASPECTS, Scientific Discipline, Health Risk Assessment, Risk Assessments, Physical Processes, Biochemistry, Biology, exposure, nanotechnology, nanomaterials, nanoparticle toxicityProgress and Final Reports:
Original AbstractThe perspectives, information and conclusions conveyed in research project abstracts, progress reports, final reports, journal abstracts and journal publications convey the viewpoints of the principal investigator and may not represent the views and policies of ORD and EPA. Conclusions drawn by the principal investigators have not been reviewed by the Agency.