The Bioavailability, Toxicity, and Trophic Transfer of Manufactured ZnO Nanoparticles: A View from the Bottom
|Principal Investigator||Paul Bertsch|
|Institution||University of Georgia|
|Relevance to Implications||High|
|Class of Nanomaterial||Engineered Nanomaterials|
|Broad Research Categories||
Generation, Dispersion, Transformation etc.
|Anticipated Total Funding||$363,680.00|
|Anticipated End Year||2008|
The overall objectives of the proposed research are to: 1) evaluate the bioavailability and toxicity of manufactured nanoparticles (ZnO) as a function of particle size to the model soil bacteria, Burkholderia cepacia and the model detritivore C. elegans as referenced against aqueous Zn2+; 2) evaluate the ability of manufactured ZnO nanoparticles to be transferred from one trophic level to the next as assessed in the simple food chain consisting of pre-exposed B. cepacia and C. elegans; and 3) evaluate the synergistic or antagonistic effects of manufactured ZnO nanoparticles on the toxicity of Cu2+ to B. cepacia and C. elegans. These three overall objectives will be approached in the context of the following four hypotheses:
Hypothesis 1: The bioavailability and toxicity of manufactured ZnO nanoparticles increases with decreasing particle size (i.e., 6 nm vs. 80 nm). Hypothesis 2: The toxicity of ZnO nanoparticles to B. cepacia and C. elegans is lower than an equivalent concentration of dissolved Zn2+. Hypothesis 3: The bioavailability and toxicity of ZnO nanoparticles introduced via trophic transfer differs from direct exposure. Hypothesis 4: ZnO nanoparticles alter the bioavailability and toxicity of dissolved metals
We will study the influence of particle size of ZnO nanoparticles, i.e. (3 nm vs. 80 nm) on bioavailability and toxicity (lethal and sub-lethal effects) and will compare these results with exposure to an equivalent concentration of aqueous Zn2+. Additionally, we will examine the effect of nanoparticles on the toxicity of a dissolved constituent (Cu2+). We will employ optical and fluorescent microscopy, element-specific synchrotron-based microspectroscopy, and hyphenated separations-ICPMS techniques to determine the distribution of nanoparticles within each organism and potential transformations of nanoparticles. Additionally, we will employ a transgenically-modified strain of C. elegans, in which we have incorporated a metal-specific promoter (metallothionein-2 [mtl-2]) that turns on expression of green fluorescent protein (GFP) in the presence of bioavailable metals. We expect that the nanoparticle will not switch on the GFP promoter but transformations (dissolution) of the nanoparticles that release the free metal will induce GFP expression. Additionally, this transgenic strain will be used to study the effect of the bioavailability of Cu2+ in the presence of ZnO nanoparticles and the potential that bioavailability will be lowered as indicated by lower GFP expression. These observations will be coupled with measurements of lethal and sub-lethal responses for C. elegans exposed directly and indirectly from grazing on preexposed B. cepacia, including behavior and reproduction. We speculate that C. elegans will bioaccumulate greater quantities of ZnO nanoparticles when feeding on pre-exposed B. cepacia compared to direct exposure as a result of the likelihood that intracellular ZnO nanoparticles will be surface modified by biocompatible molecules (e.g., peptides, proteins, other intracellular ligands) in B. cepacia.
These studies will provide among the first data on the bioavailability and toxicity of a widely used nanoparticle/nanocomposite (ZnO) to a model bacteria and detritivore and the first data available on potential for manufactured nanoparticles to be transferred through the food chain. The general lack of information on the bioavailability and toxicity of manufactured nanoparticles to microorganisms and higher organisms and on the ability of manufactured nanoparticles to be transferred from prey to predators leads to a number of very basic questions that will need to be resolved to ensure that the potential human health and ecological risks associated with the widespread use and disposal of manufactured nanoparticles are properly evaluated. The proposed research will provide critical information needed to begin to bridge these knowledge gaps.