Due to their small size, a very large fraction of the atoms making up nanoparticles are located on the particle surface. Thus, processes that affect nanoparticle surface chemistry will likely affect the transport, biouptake, and reactivity of these materials. Research on this project seeks to determine how nanoparticle surface chemistry affects their fate in the environment and how quickly these particles reach eco-receptors. This information is then used to populate a modeling framework for assessing the risks posed by nanomaterials to the environment based on the exposures (concentrations and availability) that are likely to occur and the long-term persistence of nanomaterials. Key physical-chemical pathways such as aggregation, deposition, and dissolution are examined. Additional transformations to nanoparticles and their surfaces resulting from oxidation, reduction, and adsorption are studied. Students will be fully involved in the execution of research investigating a wide range of materials including metal nanoparticles, metal oxides, fullerenes, carbon nanotubes and composites of these and other materials. We will examine the relative affinity of these materials for various environmentally-relevant solid phases as a basis for predicting where nanoparticles will likely reside in the environment, and how nanoparticle transformation may affect bio-uptake and availability. The role of aggregation and adsorption in altering nanoparticle reactivity, particularly as measured by the production of reactive oxygen species, is to be quantified.
Assessment of the fate, transport, and effects of nanomaterials in environmental systems will require sensitive and selective analytical methods for determining the concentrations and physicochemical characteristics of these materials in complex mixtures. Such trace analytical methods are generally unavailable for nanomaterials in the environment, as typical environmental analytical chemistry techniques (e.g. GC-MS and HPLC) are often of limited utility for detection and quantitation of nanoparticles in complex mixtures, and method development activity has lagged behind laboratory fate & transport studies. The objective of work in the Ferguson laboratory is to utilize a sensitive and selective spectroscopy (near-infrared fluorescence, NIRF) in combination with high resolution particle separation methods (e.g. asymmetric field flow fractionation and density gradient ultracentrifugation) to provide both quantitative and qualitative information about single-walled carbon nanotubes in estuarine sediment, water, and deposit-feeding organisms. The REU undergraduate researchers participating in this project will learn fundamental analytical chemistry principles (e.g. calibration of instruments, quantitative analysis, evaluation of analytical data) and gain experience in trace quantitative method development for environmental samples.
Silver nanoparticles are increasingly being incorporated in consumer products ranging from baby pacifiers to washing machines. Thus, it is important to determine their potential ecological impacts. Silver nanoparticles are likely to share similar attributes with ionic silver, which is known to have antimicrobial qualities. An important research question is to determine the role of silver nanoparticles in the development of microbial resistance to silver. Recent work in whole genome sequencing and bioinformatics has shown that many different types of mobile genetic elements have been exchanged between microbial species over time. It is believed that genetic adaptation results from a specific combination of exposure to physical environmental conditions, intrinsic microbial characteristics, and stress conditions. The goal of this project is to determine the cause and effect relationship between horizontal genetic adaptation and microbial exposure to silver nanoparticles. The specific research objectives are to: 1) Identify key internal and external factors which control horizontal genet ic adaptation and; 2) Induce in situ genetic adaptation in a lab-scale soil column. The success of the research will be measured by elucidating conditions that enable measurable transfer of silver-resistance plasmids. This fundamental research will lead to a better understanding of silver- and antibiotic-resistance development in microorganisms.
Work in the Bernhardt lab primarily deals with elucidating controls on carbon, nitrogen, and phosphorus cycling in soils and sediments. Through research in a variety of degraded ecosystems (agricultural fields and urban streams) the research group has recently grown interested in understanding how environmental contaminants affect the community composition and activity of the microbes that drive many ecosystem processes (nutrient and carbon cycling). This laboratory is currently examining the effects of manufactured nanomaterials on microbial community structure and function in the water and sediments of wetlands and streams. Environmental conditions can dramatically alter particle behavior, fate, and transportation and thus a key interest is examination of mechanisms by which nanomaterial toxicity may change among various environmental media and under differing chemical conditions. Students will investigate patterns and mechanisms of nanoparticle toxicity in both lab and field experiments and will have opportunities to master a variety of biogeochemical techniques.
The Hsu-Kim research group studies chemical processes that govern the fate of contaminant metals in natural and engineered ecosystems. This research primarily focuses on mercury, a toxic metal that can bioaccumulate in the food chain, and thus, impose health risks to people who eat contaminated fish. The current project examines the ability of mercury and other metals to persist as sulfide particles, the most stable form of mercury in aquatic and sediment ecosystems. In particular, this research group is investigating interfacial surface reactions that enable mercury nanoparticles to persist naturally in polluted sediments. Research goals are to understand the implications of this process for controlling bioavailability of mercury to sediment microorganisms and, ultimately, to develop models that can predict ecosystem 'hotspots' that are vulnerable to mercury bioaccumulation. Students working on this research project will gain experience in conducting environmental biogeochemistry research in laboratory and the field setting.
The Vikesland research group examines the interfacial chemistry of environmental surfaces. A current theme across the group is to develop an improved understanding of nanoparticle-water interfaces. The overall goal of the research is to gain fundamental insights into nanoparticle stability by systematically adjusting the identity of the nanoparticles under examination, the size of the nanoparticles, the surface functionality of the particles, and the chemistry of the solutions. Work on this project will involve laboratory experiments to examine the chemistry responsible for the abiotic dissolution of nanoparticles. Using both laboratory reactors and the fluid cell of an atomic force microscope, students will gain insight into the roles of solution and surface chemistry in nanoparticle dissolution. Upon completion of this internship, the student(s) will have an appreciation of the environmental chemistry of interfaces and their importance in biotic and abiotic processes.
It is well established that inhalation exposure to nanoscale particles in the atmosphere, such as those composed of soot and/or organic compounds, is associated with adverse health effects including cardiovascular disease, lung cancer, and respiratory disease. The introduction of engineered nanoparticles to the already existing potpourri of naturally occurring and incidental particles in the atmosphere presents new potential health and environmental risks. In the Marr laboratory, students will work on projects quantifying emissions of airborne particles from nanotechnology-based products, measuring human exposure to airborne engineered nanoparticles, improving techniques for physicochemical characterization of nanoparticles in the atmosphere, and/or determining the rates and products of reactions of engineered nanoparticles with pollutants in the atmosphere.
Although limited experimentation has resulted in a basic understanding of the toxicity of a small number of nanomaterials to fish, very little research has been done under environmentally-realistic conditions. Research in the DiGiulio laboratory is focused on understanding the mechanisms of nanoparticle toxicity and how the environment may alter this toxicity. Surface transformations may significantly increase or (more likely) decrease nanoparticle toxicity. Environmental conditions may also dramatically alter nanoparticle behavior, fate, and transport. Changes in particle behavior can subsequently affect bioavailability and toxicity. Students will investigate patterns and mechanisms of nanoparticle toxicity in standard fish models (e.g. killifish). The research will involve standard toxicity tests and more advanced genetic techniques. By investigating how various conditions and transformations affect nanoparticle toxicity, students will gain a better understanding of potential environmental and human health risks.
The nematode worm Caenorhabditis elegans is a versatile model organism for research, as it is characterized by a well-annotated genome, powerful genetic and molecular tools, and straightforward laboratory culturing. Although traditionally used for genetics and developmental biology, the Meyer lab is using this small nematode to test the toxicity of a range of nanoparticles. The research objective is to examine uptake and toxicity measured as growth inhibition in wild-type as well as a variety of stress-sensitive and transgenic strains of C. elegans. Students working on this project will gain experience in understanding mechanisms of impacts of nanoparticles on C. elegans, basic principles of toxicology, laboratory skills, and C. elegans biology.
The transport and fate of nanoparticles in the environment will be strongly influenced by their interactions with microorganisms. The Gregory research group studies the fate and toxicity of nanoparticles when exposed to microorganisms in natural systems such as soil and groundwater. Work on this project will involve laboratory experiments with common, non-pathogenic, soil bacteria. Student(s) will use biological reactors and various analytical biology and chemistry techniques to determine the impact of nanomaterials on microorganisms. In addition students will evaluate the biodegradation of organic coatings on nanoparticles. Student(s) will gain insights into the biological determinants of nanoparticle fate and transport as well as exposure to cutting-edge environmental science and engineering research.
Embryos and eleutheroembryos (free swimming forms with yolk sac attached) are sensitive life stages of fish. Using the aquarium model fish, medaka (Oryzias latipes) and the transparent mutant, ST II medaka, the Hinton lab is able to image uptake, tissue distribution, and response of host cells and tissues to nanomaterials. The research group coordinates with other teams to make sure that exposures to real world nanomaterials are adequately evaluated for potential unwanted effects. If students are interested in seeing life function through the body wall of these fish (medaka), they will learn cutting-edge techniques to evaluate toxicity. The results of these assays can be used to understand structural and functional alterations in a dynamic lab setting. These are biomedical type approaches in environmentally relevant life forms.
The fate of nanomaterials after releasing into the environment is a complex process. One critical aspect of the complex process is the photochemistry of nanoparticles. How the structure of the nanoparticles evolve under sunlight and UV light is a very interesting problem that needs to be studied carefully. The understanding of these changes will provide important information for understanding the pathway of nanoparticles in the environment and for researchers to design methods of treatment that can limit the effect of nanomaterials to the environment. The students involved in this study will synthesize different nanoparticles and subsequently characterize them before and after phototransformation using surface analytical and microscopy instrumentation. They will work cooperatively with other REU students in environmental science and biology to discover the effects of nanoparticles in cells, animals, and plants.
This research project will investigate the role of electrosteric repulsive forces afforded by adsorbed macromolecules on nanoparticles. These coatings have been shown to control the interactions of nanomaterials with both environmental surfaces and biological tissues (e.g. cell walls of microorganisms). However, the impact of geochemistry, i.e. pH, ionic strength, and ionic composition, on the ability of these macromolecular coatings to continue to inhibit interactions between nanomaterials and bacteria and other environmental surfaces requires further examination in order to create appropriate conceptual models for the effects of these coatings on their toxicity to organisms under various environmental conditions. The student will conduct laboratory research investigating the effect of pH, ionic strength, and ionic composition on the attachment of polymer and NOM coated nanoparticles to bacteria, and the bactericidal effects of those nanoparticles. Participating students will learn physicochemical characterization techniques for nanomaterials in water, as well as basic microbiology skills.
Organic biomacromolecules such as proteins, DNA, and natural organic matter (NOM) will adsorb to nanoparticle surfaces. These adsorbed molecules will affect their behavior in the environment as well as in an organism. Adsorption of macromolecules is not an equilibrium process so the order to exposure to various organic macromolecules will affect the overall impact of the adsorbed layer. Understanding the potential for displacement of adsorbed NOM by proteins or enzymes in the body is needed to determine the impact of nanoparticles once inside the body. Students working in the Tilton laboratory will perform experiments with carbon and metal oxide nanoparticles and various organic macromolecules including NOM, bovine serum albumin, and polysaccharides. Adsorption isotherms and displacement of previously adsorbed macromolecules will be measured to assess the potential for proteins and sugars to displace NOM, and vice versa. The modified nanoparticles will be characterized to understand the impacts of such displacements on the nanoparticle surface properties. Students will learn a variety of surface chemistry principles and become practiced in techniques for probing adsorptive interaction of molecules with nanoparticles.
This project addresses multiple aspects of the environmental impact of nanotechnology ranging from from ecotoxicity to dispersion in aquatic media. We focus on the assessment of nanomaterials and nanomaterial-containing matrices that are currently commercialized for which little or no data exist. The lack of data on the effects produced by nanomaterial-containing commercial products is underscored in a recent review paper that among the 428 papers listed dealing with the biological effects (toxicity and ecotoxicity) related to nanotechnology/nanomaterials thus far, the predominant effects documented were for free nanoparticles. However for most applications nanoparticles can be surface modified and generally are embedded in the final product and therefore do not come into direct contact with consumers or the environment. The aim of this research project within the framework of the NEPHH European project will be to study the physico-chemical properties of by-products and end-of-life silicon based nano-composites. An additional research focus will be the study of long-term effects of atmospheric exposure of the nano-SiO2 composite and the release of nano-by-product from aging experiments, to evaluate the possibility to separate SiO2-nano particles and nano-fibers from polymer by-products recover during aging experiments. Size, shape, and surface properties of nano compounds will be determined during long-term evolution of the nanomaterials. Students will gain experience in analytical techniques for measuring nanomaterials in more complex matrices, and in evaluating their effects in vitro.
There are naturally occurring mineral materials that represent interesting structural analogs for manufactured nanomaterials and/or carbon-based materials. Research at the CEREGE has considered the environmental fate of natural Al-Si nanotubes (imogolite) from volcanic soils. Indeed nanotubes (carbon or inorganic) are promising systems with many potential applications from gas storage to micro-electronic application and composite reinforcement among others. Research on this topic addresses the synthesis and effects of imogolites as they may be produced in mass production through self-assembling methods. These nanotubes possess the same structure as the natural imogolite encountered in volcanic soils. In natural soil they are strongly related to organic matter and trace metals. Student researchers will be involved with research comparing imogolite extracted from natural system to synthetic ones in terms of surface reactivity and biological effects. In addition to learning methods for characterization of nanomaterials, students will study methods for large scale nanomaterial fabrication.
Our risk assessment work addresses both hazard and exposure but places an accent on exposure assessment. To this end we consider exposure at consecutive stages in the value chain of nanomaterials production and incorporation into products, and the potential "leakage" from each node in the value chain and end-of useful life practices. This approach to estimating exposure requires considerable amounts of (currently unavailable) information concerning practices over a wide range of activities and great speculation. As an alternative, we are also developing “inventories” of nanomaterials production for key materials and predictions of nanomaterial production based on indices of commercialization and innovation. The details of this approach have been recently published by our group for the case of nano TiO2. Based on an estimated “reservoir” of nanomaterial production, first-order estimates of can be obtained that employ explicit, easily understood assumptions regarding the quantities of nanomaterials that enter the environment integrated over the entire life cycle of production through disposal. Estimates of “unconstrained” nanomaterial production based on indices of innovation and commercialization will be compared with estimated reserves of critical elements as a basis for identifying shortfalls or limitations to forecasted production levels of critical nanomaterials. A key question we are examining concerns the potential for “collateral damage” i.e. environmental impacts that arise from the production of nanomaterials rather than the nanomaterials themselves. Students working on this project will work in an interdisciplinary context between basic sciences, business, and policy as they examine methods for forecasting nanomaterial production and use. They will learn elements of risk assessment under uncertainty and become familiar with trends in nanomaterials fabrication, use, disposal, and reuse.
