Grantee Research Project Results
2006 Progress Report: Microbial Impacts of Engineered Nanoparticles
EPA Grant Number: R832534Title: Microbial Impacts of Engineered Nanoparticles
Investigators: Alvarez, Pedro J. , Wiesner, Mark R.
Institution: Rice University
Current Institution: Rice University , Duke University
EPA Project Officer: Hahn, Intaek
Project Period: December 15, 2005 through December 14, 2008
Project Period Covered by this Report: December 15, 2005 through December 14, 2006
Project Amount: $375,000
RFA: Exploratory Research: Nanotechnology Research Grants Investigating Environmental and Human Health Effects of Manufactured Nanomaterials: A Joint Research Solicitation - EPA, NSF, NIOSH (2005) RFA Text | Recipients Lists
Research Category: Nanotechnology , Safer Chemicals
Objective:
Responsible usage of nanomaterials in commercial products and environmental applications, and prudent management of the associated risks, require an understanding of nanoparticle mobility, bioavailability and ecotoxicology. This project seeks to elucidate processes governing the transport and microbial impacts of two classes of catalytic nanomaterials in soil-water systems: fullerenes and metallic nanoparticles (e.g., TiO2). Specific tasks include to
- characterize nanomaterials size, shape, functionality, reactivity, aggregation, deposition potential, and bioavailability;
- screen nanomaterials of varying sizes and properties for bactericidal activity;
- discern bacterial physiologic characteristics that confer resistance (or susceptibility) to catalytic nanomaterials;
- evaluate the potential for fullerene biotransformation by reference bacteria and fungi; and
- assess the impact of simulated nanomaterial releases on microbial diversity and community structure.
The relevance of this work to the EPA mission is related to the fact that microorganisms are the foundation of all ecosystems and are often the basis for food chains and the main agents of biogeochemical cycles. Thus, understanding their interactions with engineered nanomaterials is important to ensure that nanotechnology improves material and social conditions without exceeding the ecological capabilities that support them. At the conclusion of this project, we will have an improved understanding of the chemical and physical factors that control nanoparticle mobility and bioavailability, and their impacts on microbial activities, diversity and community structure. This will benefit risk assessment and management efforts, and may contribute indirectly to the development of nanotechnology-based disinfection and biofouling control strategies.
Progress Summary:
Antibacterial activity of nC60: effects of preparation method and particle size
Fullerene research in biological systems has been hindered by the compound’s relative insolubility in water. However, C60 molecules can be made to aggregate, forming stable fullerene water suspensions (FWS) whose properties differ from those of bulk solid C60. There are many different protocols for making FWS. This project explored four of these methods and established the antibacterial activity of each resulting suspension, including a suspension made without intermediary solvents. The aggregates in each polydisperse suspension were separated by size using differential centrifugation and tested for antibacterial activity using Bacillus subtilis as a test organism. All suspensions exhibited relatively strong antibacterial activity. Fractions containing smaller aggregates had greater antibacterial activity, although the increase in toxicity was disproportionately higher than the associated increase in putative surface area. This suggests the need for improved understanding of the behavior of FWS in organisms and in the environment to determine how C60 can be safely used and disposed.
Effect of natural organic matter on the antibacterial activity of a fullerene water suspension
We investigated the association of a C60 water suspension (nC60) with natural organic matter, present as a soil constituent or dissolved in the water column, and its effect on the antibacterial activity of nC60. Sorption of nC60 to soil reduced its bioavailability and antibacterial activity, and the sorption capacity strongly depended on the organic content of the soil. Adsorption of aquatic dissolved humic substances onto nC60 and possible subsequent reactions were also found to eliminate nC60 toxicity at humic acid concentrations as low as 0.05 mg/L. These findings indicate that the potential impacts of nC60 on microbial activities that are important to ecosystem health can be significantly mitigated by natural organic matter in the environment.
Assessing a fullerene water suspension as an antibiofouling surface treatment
Antibacterial fullerene-based particles, termed nC60, were coated onto a polystyrene surface to evaluate their ability to prevent biofilm formation by Pseudomonas mendocina. Biofilm growth on this surface was assessed using ethidium bromide staining and SEM, and cell viability was determined using live/dead fluorescent cell staining. Unexpectedly, surfaces coated with nC60 developed a biofilm earlier than the uncoated control, and a higher percentage of live bacteria. The nC60 coating appeared to encourage rather than discourage biofilm formation. Additionally, the bacteria that adhered to the surface were not killed, implying that while nC60 would not perform well in this application, the electronic properties of fullerenes and apparent ability to encourage biofilm formation should be investigated for potential microbial fuel cell applications.
Effect of natural organic matter on the antibacterial activity of a fullerene water suspension
This study investigated the association of a C60 water suspension (nC60) with natural organic matter, present as a soil constituent or dissolved in the water column, and its effect on the antibacterial activity of nC60. Sorption of nC60 to soil reduced its bioavailability and antibacterial activity, and the sorption capacity strongly depended on the organic content of the soil. Adsorption of aquatic dissolved humic substances onto nC60, and possible subsequent reactions, was also found to eliminate nC60 toxicity at humic acid concentrations as low as 0.05 mg/L. These findings indicate that the potential impacts of nC60 on microbial activities that are important to ecosystem health can be significantly mitigated by natural organic matter in the environment.
Educational; Achievements:
This project has served as the basis for one PhD dissertation, which won the best dissertation award for the Brown School of Engineering at Rice University:
Delina Y.M. Lyon (2007). “Bacteria and C60: the microbial response to fullerene water suspensions.” PhD Thesis, Rice University.
This project also subsidized the following MS Thesis: Dong Li (2007). “Effect of Geosorbents on Antibacterial Activity of nC60” MSc. Thesis, Rice University
Journal Articles on this Report : 6 Displayed | Download in RIS Format
Other project views: | All 16 publications | 15 publications in selected types | All 13 journal articles |
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Brunet L, Lyon DY, Zodrow K, Rouch J-C, Caussat B, Serp P, Remigy J-C, Wiesner MR, Alvarez PJJ. Properties of membranes containing semi-dispersed carbon nanotubes. Environmental Engineering Science 2008;25(4):565-576. |
R832534 (2006) R832534 (2007) R832534 (Final) |
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Fang J, Lyon DY, Wiesner MR, Dong J, Alvarez PJJ. Effect of a fullerene water suspension on bacterial phospholipids and membrane phase behavior. Environmental Science & Technology 2007;41(7):2636-2642. |
R832534 (2006) R832534 (2007) R832534 (Final) |
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Lyon DY, Adams LK, Falkner JC, Alvarez PJJ. Antibacterial activity of fullerene water suspensions: effects of preparation method and particle size. Environmental Science & Technology 2006;40(14):4360-4366. |
R832534 (2006) R832534 (2007) R832534 (Final) |
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Lyon DY, Brown D, Sundstrom ER, Alvarez PJJ. Assessing the antibiofouling potential of a fullerene-coated surface. International Biodeterioration & Biodegradation 2008;62(4):475-478. |
R832534 (2006) |
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Lyon DY, Brown DA, Alvarez PJJ. Implications and potential applications of bactericidal fullerene water suspensions: effect of nC60 concentration, exposure conditions and shelf life. Water Science and Technology 2008;57(10):1533-1538. |
R832534 (2006) R832534 (Final) |
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Wiesner MR, Lowry GV, Alvarez P, Dionysiou D, Biswas P. Assessing the risks of manufactured nanomaterials. Environmental Science & Technology 2006;40(14):4336-4345. |
R832534 (2006) R832534 (Final) |
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Supplemental Keywords:
Health, Scientific Discipline, Health Risk Assessment, Environmental Chemistry, Risk Assessments, Ecological Risk Assessment, anthropogenic stress, ecotoxicogenomics, bioavailability, nanotechnology, nanomaterials, microbial 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.