The Fate and Effects of Nanosized Metal Particles along a Simulated Terrestrial Food Chain Investigated Using Genomic and Microscopic Techniques
Project Information
| Principal Investigator | Jason Unrine |
| Institution | |
| Project URL | View |
| Relevance to Implications | High |
| Class of Nanomaterial | Engineered Nanomaterials |
| Impact Sector | Environment |
| Broad Research Categories |
Exposure Generation, Dispersion, Transformation etc. |
| NNI identifier |
Funding Information
| Country | USA |
| Anticipated Total Funding | $397,000.00 |
| Annual Funding | $132,333.33 |
| Funding Source | EPA |
| Funding Mechanism | Extramural |
| Funding Sector | Government |
| Start Year | 2007 |
| Anticipated End Year | 2010 |
Abstract/Summary
This project will investigate interactions between nanoparticle size and chemical composition for 5 and 100 nm Cu, Ag, and Au nanoparticles in determining bioavailability, tissue distribution and toxicity in a simulated terrestrial food chain consisting of soil, earthworms (Eisenia fetida), and bullfrogs (Rana catesbeiana). Genomic and microscpectroscopic techniques will be employed to determine the tissue distribution and cellular effects of the nanoparticles.
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 (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; 3) to investigate interactions among size and chemical composition of NSP conductors in determining bioavailability and toxic mode of action. These objectives will be met by testing the following hypotheses:
Hypothesis 1: The absorption and extent of redistribution of metal NSPs among organ systems as well as the extent of binding to macromolecules decreases with increasing particle size.
Hypothesis 2: Metal NSPs 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 NSPs is determined by interactions between chemical composition and particle size.
Hypothesis 4: Toxicity of metal NSPs can be unrelated to the release of free metal ions.
Approach:
We will address the above hypotheses using a simulated terrestrial food chain consisting of soil, earthworms (Eisenia fetida), and bullfrogs (Rana catesbeiana). Bioaccumulation of 5 and 100 nm Au, Ag, and Cu nano-sized particles (NSPs) as referenced against Au, Ag, and Cu ions will be assessed using a standard soil-earthworm protocol. Bioavailability of 5 and 100 nm NSPs will then be compared between trophic and direct exposure by exposing bullfrogs using either worms that have bioaccumulated NSPs or exposing them to equivalent doses using oral gavage. Uptake and elimination rates will be determined in each species along the food chain to assess the potential for biomagnification. The extent of redistribution of nanoparticles among organ systems in both species will be evaluated by examining dissected tissues using a synchrotron based x-ray microprobe (SXRF) and any transformations in oxidation state will be assessed using x-ray absorption near edge structure (XANES). Mode of uptake, sub-cellular disposition, and the state of aggregation of NSPs will be evaluated in both organisms by employing transmission electron microscopy (TEM) and energy dispersive x-ray spectroscopy (EDX). The extent of NSP and metal ion redistribution among macromolecules such as metallothionein will be evaluated using size exclusion chromatography with inductively coupled plasma mass spectrometry (ICP-MS) and will be referenced against exposure to metal ions. Toxicity of NSPs as compared to free metal ions will be determined using both ecologically relevant measures, such as lethality, growth, and reproduction, as well as changes in expression of genes related to metal regulation and oxidative stress using quantitative real time polymerase chain reactions (Q-RT-PCR). Transcriptomic responses will also be compared with changes on the proteome level to glean information about the mechanisms of toxicity.
Expected Results:
These studies will provide among the first data on the bioavailability of important basic nanomaterials that have broad industrial applicability (Cu, Au and Ag). The potential for food chain transport of nanomaterials represents a key knowledge gap that must be filled in order to assess the risks posed to human and ecological receptors by their release to the environment. The proposed research will also begin to build a systematic framework for predicting the distribution of nanoparticulate metals both in food webs, and at the sub-organismal, sub-cellular, and molecular levels. Further, it will test the feasibility of using genomic biomarkers to assess chronic toxicity of nanoparticles to ecological receptors. These have all been identified as priority research needs for the U.S. Environmental Protection Agency.
