Grantee Research Project Results
2008 Progress Report: Ecotoxicology of Underivatized Fullerenes (C60) in Fish
EPA Grant Number: R833333Title: Ecotoxicology of Underivatized Fullerenes (C60) in Fish
Investigators: Henry, Theodore B. , Sayler, Gary S. , Menn, Fu-Min , Compton, Robert N.
Institution: University of Tennessee
EPA Project Officer: Aja, Hayley
Project Period: May 15, 2007 through May 14, 2010
Project Period Covered by this Report: May 15, 2008 through May 14,2009
Project Amount: $396,807
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: Safer Chemicals , Nanotechnology
Objective:
Objectives: Investigate characteristics of aqueous C60 aggregates and the impact of dissolved organic material on behavior of nanoparticles. Evaluate bioavailability and toxicity of C60 (both aqueous C60 aggregates and dietary C60) in fish by evaluating changes in gene expression, histopathology, and bioaccumulation of C60 in tissues. The species we will consider are zebrafish Danio rerio and channel catfish Ictalurus punctatus.
Hypotheses: 1) Bioavailability of aqueous C60 aggregates is impacted by nanoparticle characteristics and presence of dissolved organic material; 2) Exposure of fish to C60 can be detected by changes in expression of biomarker genes; and 3) Toxic effects of C60 in fish are evident only after long-term chronic exposure.
Progress Summary:
Results from our group (reported in the 2008 annual report) indicated that previously published research by others that reported toxicity of C60 in fish was likely a consequence of the tetrahydrofuran vehicle (used to make C60 aggregates) rather than the C60 itself. While one objective of this project is to investigate the relation of C60 aggregate characteristics and toxicity, the lack of observed toxicity (based on global array results, and toxicity assays) in the absence of vehicles has limited this particular direction of the research. However, the interaction of C60 aggregates and existing environmental contaminants (e.g., EDCs, PCBs, Me-Hg) has emerged as a highly relevant issue for the ecotoxicology of nanoparticles. The interaction of nanoparticles (NPs) with existing contaminants (termed here “co-contaminants) can occur during the manufacture of NPs, during NP disposal (e.g., through wastewater treatment plants), or after release into the environment (e.g., with existing highly persistent contaminants). During this project period we investigated the interaction C60 aggregates and the synthetic estrogen 17α-ethylnilestradiol (EE2) and evaluated changes in aggregate characteristics and bioavailability of EE2 in fish. EE2 is an environmental toxicant that has been linked to estrogenic effects in fish.
Aqueous aggregates of C60 were characterized by size, zeta-potential, and absorbance in the 300-900 nanometer range. Particle size and zeta-potential were measured with a Brookhaven ZetaPlus instrument, which uses dynamic light scattering to obtain size distributions of the nanoparticles and electrophoretic measurements to determine the zeta-potential. The absorbance measurements were made with a HP 845x UV-Visible spectrophotometer. We found that C60 aggregates sedimented out of the aqueous phase relatively rapidly and that the size of particles and amount of C60 that remained in the aqueous phase was influenced by the presence of EE2. The C60 aggregates accumulated EE2 and decreased the bioavailability of EE2 in larval zebrafish, and the association of EE2 with C60 aggregates increased over time. The ability of NP aggregates to sequester contaminants and remove them from the aqueous phase was demonstrated, and experiments are currently underway to evaluate whether the EE2 can become bioavailable when the C60 aggregates containing EE2 pass through the gut.
A significant component of this project is to evaluate the bioaccumulation and toxicity of C60 in fish and this objective requires use of fish larger than zebrafish to provide sufficient amounts of tissue for analysis. This component of the project was addressed by preparing the wet lab facilities at UT for channel catfish to be exposed to C60 through the diet. Twelve fiberglass tanks (115 cm diameter X 50 cm deep) were plumbed with flow-through water in preparation for experiments. Experimental design includes four conditions (three treatment and one control) each with three replicate tanks. Experiments to investigate the bioaccumulation and toxicity of C60 in channel catfish exposed through the diet will occur in August – September 2009.
The dietary toxicity of C60 was investigated in rainbow trout during a collaborative research project with the University of Plymouth during the previous reporting period. In this experiment juvenile rainbow trout were exposed (61 d) to 500 mg SWCNT/kg food, a 500 mg C60/kg food, or a control (no carbon nanoparticles CNPs). Samples were analyzed during the present reporting period and manuscripts are currently in review from this work. The feeding rate, growth, and condition factors were not influenced by exposure to either NP and a whole body systems toxicology approach to investigate effects of C60 did not resolve any toxic effects from this NP. These assays included enzyme activity tests, tissue metals concentrations, tissue histopathology, hematology, and disturbance of osmoregulation. In the liver of two of six fish exposed to C60 and examined by histopathology, a single focal lesion of necrosis and inflammatory cell infiltration were observed, but this observation was not attributable directly to exposure.
Future Activities:
The focus of this project does not deviate significantly from the original project objectives; however, we have added specific experiments that have become relevant during the course of our investigations. These include investigating the effects of aqueous C60 aggregates on the bioavailability and toxicity of co-contaminants and how these contaminants alter aggregate characteristics. We are presently adding the issue of co-contaminant toxicity to our dietary exposure experiments. We will continue to integrate our research with international nanotoxicology efforts, and in particular those that are ongoing and under development at the University of Plymouth. Our experiments with rainbow trout indicated that dietary exposure to C60 did not cause toxic effects for the effects we evaluated. Our experiments with channel catfish will be used to confirm these results and also to expand our understanding of co-contaminant toxicity. We anticipate continuing experiments with zebrafish for most of the next reporting period and experiments with channel catfish will begin shortly.
Journal Articles on this Report : 1 Displayed | Download in RIS Format
Other project views: | All 25 publications | 6 publications in selected types | All 6 journal articles |
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Type | Citation | ||
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Henry TB, Menn FM, Fleming JT, Wilgus J, Compton RN, Sayler GS. Attributing effects of aqueous C60 nano-aggregates to tetrahydrofuran decomposition products in larval zebrafish by assessment of gene expression. Environmental Health Perspectives. 2007;115(7):1059-65. |
R833333 (2007) R833333 (2008) |
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Supplemental Keywords:
co-contaminant, Health, PHYSICAL ASPECTS, Scientific Discipline, ENVIRONMENTAL MANAGEMENT, Health Risk Assessment, Risk Assessments, Physical Processes, Biochemistry, Risk Assessment, biological pathways, bioavailability, exposure, genetic analysis, nanotechnology, carbon fullerene, human exposure, nanomaterials, fish model, toxicologic assessment, histopathology, nanoparticle toxicity, carcinogenic, human health riskProgress 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.