Grantee Research Project Results
2009 Progress 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
Current Investigators: Unrine, Jason M. , Bertsch, Paul M. , Tsyusko, Olga V. , Neal, Andrew
Institution: University of Georgia , Rothamsted Research , University of Kentucky
Current 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 Period Covered by this Report: May 1, 2009 through May 1,2010
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 are 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 nano-sized 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.
Progress Summary:
Progress towards testing the hypotheses:
Hypothesis 1: We have conditionally rejected this hypothesis. We have only observed this effect 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. 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.
Hypothesis 2: Not fully tested yet; however, based on very limited uptake (BAFs ~ 0.001-0.01) from soil by earthworms, we expect that metal NSPs do not biomagnify. We plan to test the second part that NSPs are more bioaccumulative through trophic exposure beginning in May 2010.
Hypothesis 3: We cannot reject this hypothesis. We have evidence for reproductive toxicity being determined by chemical composition, but so far we do not have strong evidence for an interaction with particle size. This might only be true for very small particles that are not commercially produced in very large quantities. It appears that the Ag nanoparticles are the most toxic of the three materials.
Hypothesis 4: This hypothesis appears to be correct. 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.
During the current reporting period, we have published two manuscripts in peer-reviewed journals (one published online, one accepted) and have submitted two additional manuscripts. We have also given numerous invited talks on our research. Given our findings from the previous reporting period 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 (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 (XAS) 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 using phospholipid fatty acid analysis (PFLA), thus providing the first evidence that organisms may actually sense nanomaterials.
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:
Health, Scientific Discipline, PHYSICAL ASPECTS, Health Risk Assessment, Physical Processes, Risk Assessments, Biology, Biochemistry, nanomaterials, exposure, nanotechnology, 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.