C60 Biotransformation and Bioaccumulation: Environmental Impact Implications

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CBET- 0829158 AlvarezRapid industrial scale production, coupled with unique material properties, underpin rising concerns of engineered nano-scale materials inadvertently impacting the health and function of natural systems. Carbon based nano-scale materials such as fullerenes and nanotubes in particular have been proposed for a variety of applications and are on track to be produced at industrial scales. Building a fundamental, quantitative understanding of material behavior in natural and engineered systems allows for accurate predictive behavior models which are critical for material life cycle assessment(s) necessary for risk mitigation and sustainability. Of particular interest is the biological interface at which these materials may interact as biologically mediated transformations of fullerenes could significantly influence their mobility, bioavailability, reactivity, toxicity and overall environmental impact. Yet, to date, no systematic evaluations of fullerene biotransformation has been conducted. They will seek to evaluate the susceptibility of aqueous available fullerene species to biochemical transformations and their biological significance. Specifically, they will: (1) characterize the rates and byproducts of biotransformation through, in part, the use of radio labeled P14PCB60B, (2) determine how biotransformation affects the toxicity of CB60B, and (3) quantify the bioavailability and bioaccumulation potential of P14PCB60B and its byproducts through model earthworm systems. They will test the hypotheses that: 1) CB60B can be oxidized by non-specific enzyme systems such as manganese peroxidase, which is involved in complex carbon macromolecules degradation via radical (OH) attack, and/or by other enzymes produced by cellulytic fungi or bacteria that degrade recalcitrant compounds; and (2) such biotransformations will decrease the toxicity and bioaccumulation potential of CB60B, but may increase its solubility and bioavailability. Using chemically unique CB60B with differential isotopic signatures, biotransformation investigations will be conducted with cell free (e.g. purified manganese peroxidase which catalyzes non-specific radical (OH) oxidation), and with whole cell, in vivo cultures of cellulytic fungi, PAH-degrading mixed cultures, and PAH-degrading pure cultures. Reaction kinetics and products will be characterized by a battery of analyses (Radiochromatography (HPLC), P13PC-NMR, MALDI-MS, UV/Vis, Scintillation Counting, among others). Corresponding toxicity studies will measure microbial heterotrophic activity before and after exposure to water available CB60B and bio-transformed derivatives. Bioaccumulation and availability of both C60 and corresponding derivatives will be evaluated through whole organism (model earthworm systems) and biomimetic sorbent experiments similar to previous studies done with polyaromatic hydrocarbons. This work responds to calls for reliable data on nanoparticle behavior in the environment that have come from environmental advocacy groups, the emerging nanotechnology industry and the regulatory community. Understanding how biotransformation affects the behavior of engineered nanomaterials in the environment is important to ensure that nanotechnology improves material and social conditions without exceeding the ecological capabilities that support them. Furthermore, students on this project will gain valuable interdisciplinary and collaborative experience with applications of nanochemistry and environmental engineering. This project will strengthen the nation?s research and human resource base in an emerging need area where qualified researchers are in short supply, and will contribute to the development of nanotechnology as a tool for sustainability rather than as an environmental liability.