Nano Technology Abstracts, H -NAcute and Chronic Toxicity
of TiO2 to Freshwater Aquatic Organisms, and Effects of Organic
Carbon on TiO2 Bioavailability Four species of freshwater aquatic organisms representing three trophic levels (primary producer, invertebrate, and fish) were exposed to titanium dioxide (TiO2) with a nominal particle size of 10 nm. Powder X-ray diffraction (XRD) and Scherrer’s analysis were successfully used to confirm particle sizes in aqueous media used in toxicity testing. Conventional metals analysis was shown to be inadequate to quantify aqueous Ti concentrations when Ti was present in nano forms. Powder XRD scans of test solutions indicated that the only detectable TiO2 phase present was the anatase form, with an average particle size of 11.2 ± 3.0 nm. Acute toxicity testing indicated that invertebrates (Ceriodaphnia and Daphnia pulex) were more sensitive to TiO2 than fish. Invertebrate LC50 values ranged from 3 to 100 mg/L as compared to fish LC50 values of 500 mg/L to greater than 1,000 mg/L. Chronic toxicity values indicated the same trend of higher invertebrate sensitivity, with respective invertebrate and fish IC25 values of 2.5 to 26.4 mg/L and 342 to 597 mg/L. Chronic testing with the green algae Raphidocelis subcapitata (formerly Selenastrum capricornutum) indicated that this organism was more sensitive to TiO2 than fish and C. dubia. R. subcapitata IC25 values ranged from 1 to 2 mg/L TiO2. Addition of an inorganic substrate (kaolinte clay) somewhat decreased TiO2 toxicity to C. dubia (LC50 38.6 mg/L), whereas organic carbon additions to test waters dramatically decreased TiO2 toxicity (LC50s 57.6 to > 100 mg/L). This likely contributed to the low acute to chronic ratios (ACR) observed. The presentation provides an overview of these data with respect to other data and species sensitivity trends reported in the literature on the aquatic toxicity of TiO2. Detection, Analysis and Characterization of Engineered Nanoparticles in Environmental Samples To ensure sustainable development of nanotechnology, risk assessments of engineered nanoparticles (ENP) from various applications are required and for that it is essential to have the tools to carry out both effect and exposure assessment. That requires thorough characterization of nanoparticles and their aggregates. The characterization needs include initial detailed material characterization and dispersion properties and exposure characterization during effect experiments. Conventionally, exposure assessment is recommended to include both a modeling and a measurement approach, and both approaches require instrumentation and methodology of nanoparticle analysis. Prediction of environmental concentrations through modeling is mainly founded on emission scenarios and distribution parameters (fate and behavior). Presently, fate and behavior parameters of ENP are not known, and use of suitable analytical methods to determine the concentrations and nanoparticle characteristics in lab and field experiments is a prerequisite to acquire such distribution parameters. As the complementing approach to modeling, it has been emphasized that one of the main challenges for safe implementation of nanotechnology is the development of methods to monitor nanoparticles in the environment. Pilot-testing Carboxymethyl Cellulose Stabilized
Nanoiron Technology for In-situ Destruction of Chlorinated Solvents
at an Alabama Site This study pilot-tested the carboxymethyl cellulose (CMC) stabilized nanoiron technology for in-situ destruction of chlorinated hydrocarbons such as PCE, TCE and PCBs at an Alabama site. The test area was located in a well-characterized contaminant source zone. Four testing wells were installed along the groundwater flow direction (spaced 5 ft apart), including one injection well (IW), one up-gradient monitoring well and two down-gradient monitoring wells (MW-1 and MW-2). The stabilized nanoiron was successfully prepared on site before it was injected into the 50-ft deep, unconfined aquifer. Approximately 150 gallon of 0.2 g/L Fe-Pd (CMC = 0.1 wt%, Pd/Fe = 0.1 wt%) nanoparticle suspension was synthesized and gravity-fed into the injection well IW-1 over a 4-h period. Compared to tracer Br-, ~37.4% and ~9.0% of the injected Fe was observed in a 5 ft and 10 ft down-gradient monitoring wells MW-1 and MW-2, respectively, confirming the soil mobility of the nanoparticles through the aquifer. Rapid degradation of primary contaminants PCE, TCE, and PCBs was observed in both MW-1 and MW-2, with the maximum degradation being observed in 4 days. The contaminant concentrations gradually increased back to their pre-injection levels in about 12 days. However, a second phase degradation of PCE and TCE was then started again thereafter. For example, on the 29th day after the injection, the concentrations of TCE in MW-1 and MW-2 were lowered to 72 ppb and < 10 ppb, respectively, from the original concentrations of 1655 ppb and 3710 ppb. It is proposed that the H2 from the Fe corrosion in the presence of trace levels of a metal catalyst (Pd) facilitated the early stage rapid abiotic degradation, and thereafter, a biological degradation process was boosted through the abiotic process and with CMC as a fine carbon source, resulting in the sustained enhanced destruction of the chlorinated organic contaminants in the subsurface. One month later, another 150 gallon of 1.0 g/L Fe-Pd (CMC = 0.6 wt%, Pd/Fe = 0.1 wt%) was injected into IW-1 at injection pressure < 5psi. Similar pattern of PCE, TCE, and PCB degradation was observed in both monitoring wells. The concentrations of PCE and TCE remain as low as less than 150 ppb in both MW-1 and MW-2 nearly 600 days after the first injection. Furthermore, an independent analysis shows that the VC and cis-DCE didn’t accumulate during the process, and were degraded by about 20% and 40% in MW-1and MW-2, respectively Single-Particle ICPMS for Characterizing
Metal-Based Nanoparticles in the Environment: Advances and Challenges As engineered metal-based nanomaterials become widely used in consumer and industrial products, the amount of these materials introduced into the environment by a variety of paths will increase. The concentration of metal associated with these engineered nanoparticles will be superimposed on the metal concentration from other natural and anthropogenic nanoparticles of the same or different chemical composition. Therefore, in order to evaluate potential exposure of ecosystems to engineered nanomaterials, methods must be available for measuring spatial and temporal trends in the concentration, size distribution, and metal content of nanoparticles in environmental compartments. Approaches for these types of measurements have been either single-particle methods such as electron microscopy, or ensemble techniques that measure properties of the population of particles. The ensemble methods are less specific than single-particle imaging, but can produce statistically representative characterization of the environmental sample. Ensemble techniques include filtration and ultrafiltration followed by elemental determination by inductively coupled plasma mass spectrometry (ICPMS) to estimate metal concentration in operationally defined size fractions. Hyphenated instrumental techniques, such as flow-field flow fractionation (FFF) coupled with ICPMS, provide better defined size distributions. This presentation describes a third approach, ICPMS in the single particle (SP) mode. SP-ICPMS can provide number density of particles, as well as mass of the measured metal in the particles. It can therefore be used without any accompanying separatory method to screen metal-containing nanoparticle concentrations. Coupled with a size separation method, SP-ICPMS can provide the fractional metal content of particles, thus discriminating between metal-based nanoparticles and background nanoparticles with only minor metal content (e.g., minerals and metal sorbed on natural organic matter). We describe and demonstrate the theory of SP-ICPMS and its application as a stand-alone screening method and in combination with size separation. We discuss current challenges to its wide application in environmental characterization of metal-based nanoparticles and potential solutions to these challenges. Notice: The U.S. Environmental Protection Agency (EPA), through its Office of Research and Development (ORD), prepared this abstract for a proposed oral presentation. It does not necessarily reflect the views of the EPA or ORD. Interaction of Aqueous C60 Aggregates
with Environmental Contaminants and Toxicological Consequences in Fish Establishing the toxicity of nanoparticles (NPs) is essential to protect human and environmental health and to appropriately guide the development of nanotechnology. In addition to the toxicological effects of NPs in organisms, it is also important to consider the interactions of NPs on the bioavailability and toxicology of other environmental contaminants including persistent organic compounds and endocrine disrupting substances. Our investigations consider interactions of specific toxicants with aqueous C60 aggregates and the influence of this interaction on NP characteristics and on the bioavailability of toxicants in zebrafish. Toxicity/bioavailability was assessed by changes in global gene expression (Affymetrix GeneChip® Zebrafish Genome Array) and changes in expression of specific genes (quantitative reverse transcriptase PCR, qRT-PCR). Changes in global gene expression in larval zebrafish after 75-h exposure to 1) C60 aggregates generated by stirring and sonciation (72 h) of C60 in water (12.5 mg C60/500 mL water), 2) C60 aggregates generated by established methods with tetrahydrofuran (THF) vehicle, 3) THF vehicle (i.e., method 2 without C60 added), and 4) “fish water” control; indicated no toxicological effects of C60 generated by C60 stirred in water (i.e., method 1, (no vehicle)) whereas toxicity was evident from decomposition products of THF vehicle. Mixtures of aqueous C60 aggregates (method 1 above) and the synthetic estrogen, 17α-ethinylestradiol (EE2), led to a reduction in charge (zeta potential) and a decrease in the size of aggregates in the aqueous phase. Decreased aggregate size appeared to be a consequence of increased rate of sedimentation/settling of larger C60 aggregates when mixed with EE2. The bioavailability of EE2 in larval zebrafish exposed to EE2, mixtures of EE2 and aqueous C60 aggregates, or vehicle control (EtOH) was assessed by changes in expression of the estrogen sensitive vitellogenin gene (VTG) by qRT-PCR. The presence of aqueous C60 aggregates decreased EE2-induced VTG expression in a dose-dependent manner and indicated a strong association between EE2 and C60 aggregates. The reduction in the bioavailability of EE2 when mixed with aqueous aggregates of C60 is an interesting result with implications for the environmental fate of toxicants if C60 is ultimately released into the environment. Isolation and Characterization of Products
From Nano Energetic Composites Nano materials are currently being investigated by the DOD for numerous
applications such as primers for ammunition, igniters, flares, explosive
additives, propellant additives, flash bang grenades, and other weapon
systems. As an environmentally friendly alternative to ammunition
containing lead styphnate or lead azide based primers, nano energetic
composites (NEC) based primers are under development for DOD application
to eliminate airborne lead. The NEC based primers could potentially
replace billions of standard lead primers used in small and medium caliber
ammunition by the DOD. However, the question is, “What are the environmental
ramifications of utilizing nanomaterials in weapon systems?” What
are the short and long term environmental problems that could arise from
the release of man-made nanomaterials? The production and release
of nanomaterials into the environment is a controversial issue with no
current answers. A Comprehensive Approach to Nanotechnology
Policy The emergent nanotechnology industry is at a crossroads, and faces three significant challenges. First, the industry faces economic challenges due to increasing risk uncertainty, inefficient commercialization, and environmental, health, and safety (EHS) externalities. Secondly, legal challenges stem from a legal framework that fails to adequately address unique nanomaterial properties and a lack of scientific research to adequately define risk and to inform more effective regulation. Finally, the U.S. and the EU have built a strong consensus that current frameworks are sufficient, yet there is an increasing likelihood of standards disharmonization. The current regulatory literature fails to comprehensively analyze all existing regulatory forms. Such limited analysis leads to an improper focus on specific regulatory sectors, a failure to recognize private risk management as an important tool, and a call for incremental change to the existing framework. Each of these outcomes fails to leverage maximum efficiency and risk management opportunities. In response, this assessment flows from a detailed and comprehensive analysis of the existing regulatory framework in the U.S. and the EU, focusing on a systematic comparison of 29 U.S and 26 EU consumer, worker, environmental, intellectual property, and standards and measurements laws. Additionally, we have analyzed all U.S. and EU industry self-regulation in the form of codes of conduct and risk management tools, as well as special interest group calls for increased regulation. The resulting work creates a clear picture of the current challenges and the need for an integrated public-private regulatory framework in order to manage risk efficiently in the face of insufficient scientific data to properly develop new regulation. There is also a lack of economic analysis to augment the legal and political analysis conducted to date. Understanding the 1st-order economic impact of various policy options is critical for building more effective and efficient policy to maximize market potential safely and responsibly. Our analysis will include 1st-order analysis of all potential policy options in order to demonstrate the most efficient options. Our goal is to provide a toolkit of policy options that refine the existing system until science can provide answers regarding risk, costs, and benefits. This toolkit includes public policies that reduce information asymmetry and incentivize private risk management practices to better protect consumers, workers, the environment, and industry. This work will address a wide range of questions, including industry self-regulation efficacy, types (including insurance), the interplay with private and public investors and government regulation, the timing and extent of new regulation based on scientific support, and the role of the precautionary principle. Manufacturing with Nanoparticles: Results from Exposure Monitoring in Air Progress in the Design of Carbon Nanotubes for
Environmental Health and Safety Recent research has led to serious societal concern about the potential impacts of carbon nanotubes on human health. Nanotubes are complex materials, however, and there is significant potential to influence both hazard and risk by intelligent engineering of nanotube structure, purity, and surface properties. This presentation examines the underlying mechanisms through which nanotubes interact with biological structures and the role of specific material features that include length, biopersistence, surface chemical activity, and metals content and release behavior. A major concern for carbon nanotubes is their postulated adherence to the fiber pathogenicity paradigm, whose key material features are diameter, length, and biopersistence. New experiments will be described, in which nanotubes are undergo long-term exposure to oxidant-generating physiological simulants in a new assay designed to assess biopersistence. The assay is being used to search for covalent functionalization schemes that improve nanotube safety by promoting physiological degradation. The possibilities for length and aggregation control in nanotubes will also be discussed as additional methods for avoiding the pathogenic fiber classification. A number of nanotoxicology studies have reported that carbon nanotubes
induce oxidative stress, which is an imbalance between the generation
and destruction of intracellular reactive oxygen species (ROS). One source
of ROS is the release of redox-active metals into solution. In
the absence of metal ions, carbon materials are not intrinsic oxidants,
and the fundamental origin of ROS in highly purified nanotubes is unclear. Here
we study the fundamental chemical interactions between nanotubes and
the key antioxidant, glutathione. It is found that single-wall nanotubes
deplete GSH in buffers, and that GSH can be regenerated by addition of
the physiological reducing reagent NADPH along with glutathione reductase,
which provides strong evidence for an oxidation mechanism. The GSH reaction
is significantly inhibited under conditions of low dissolved dioxygen,
further suggesting that the graphenic nanotube surface reduces molecular
oxygen to reactive peroxide intermediates, which are the direct oxidants
for GSH. The behavior of a variety of carbon nanomaterials will
be presented and compared, and the implications for the development of
safe carbon nanotubes are discussed. SWNTs Inhibit Normal Physiological
Function of Calcium Ion Channels Through Yttrium Release The calcium ion channel is a voltage gated channel that enables calcium to enter electrically active cells. Proper function of these channels is essential for gene expression, neuronal excitability, muscle contraction and the release of neurotransmitters and hormones. As carbon nanotubes are electrically conductive and hydrophobic, they may interact with cell membranes and ion channels and adversely affect cells that rely on membrane potential for proper function. In this study, tsA201 cells were transfected with the CaV2.2 neuronal calcium ion channel and exposed to aryl sulfonated SWNTs prior to electrophysiological characterization. Here we show that CNTs inhibit neuronal voltage-gated calcium-ion channels in a dose dependent manner. Inhibition does not involve tubular graphene, but can be traced to soluble yttrium released from the growth catalyst. Yttrium cation is a potent inhibitor of the calcium ion pore of the channel with efficacy at 0.07 ppm w/w. Unpurified and even some CNT samples considered purified, contain sufficient bioavailable yttrium to prevent the flow of calcium through the channel. Bacterial Toxicity of Oxide Nanoparticles
and Their Adhesion to Bacteria Cell Walls Oxide nanoparticles (NPs) are a large group of nanomaterials widely
applied in insulators, catalyzers, paints, cosmetic products, textiles
and semiconductors. Because of their widespread application and production,
NPs will eventually enter the environment where their fate and behavior
are largely unknown. In this study, toxicity of nano-scaled aluminum,
silicon, titanium, and zinc oxides to bacteria (Bacillus subtilis, Escherichia
coli and Pseudomonas fluorescence) was examined and compared to that
of bulk (micro-scaled) materials of the same composition. All nano-scaled
particles but titanium oxide showed higher toxicity (at 20 mg/L) than
their bulk counterparts. Toxicity of released metal ions was differentiated
from that of the oxide particles. Our results indicated that the responses
of bacteria to engineered NPs are different from bulk materials of the
same composition, hence NPs toxicity mechanism need to be studied thoroughly.
TEM images showed attachment of nanoparticles to the bacteria, which
can be ascribed to electrostatic force and surface bonding, suggesting
that toxicity of nanoparticles was affected by their attachment to the
bacteria. Zeta potential of particles and bacteria were measured to verify
the role of electrostatic force in nanoparticle attachment to bacteria.
FTIR technique provided the data on phosphate group binding and changes
in bacteria amide groups. The protein secondary structure changes were
also identified by second derivatives of FTIR spectra. Therefore the
NPs interaction with carboxyl, amide, phosphate, hydroxyl functional
groups on bacteria cell wall may play an important role on the bacterial
toxicity. Emission of Silver Nanoparticles from
Exterior Facade Coatings This study investigated the release of silver nano (nAg) - particles from paints for exterior facades. nAg particles are increasingly applied due to their known antimicrobial effect. In paints used for exterior applications nAg particles are incorporated to protect the facade against growth of algae and fungi. Thus, nAg particles are considered an alternative to biocides. However, the fate of the nAg particles is not clear yet; especially whether these particles remain in the paint, or whether they are washed out during rain events needs to be investigated. In a recent study Kaegi et al. (2008) demonstrated that nano-scale TiO2 particles are released from facades and transported by stormwater directly to surface waters. A similar behavior of nAg particles is likely. In order to test whether nAg particles are released and - if so - to quantify the amount of nAg particles, we performed experiments in a simulation chamber, where a facade with the nAg containing paint was artificially weathered. One weathering cycle consisted of three hours of UV irradiation followed by one hour of irrigation and two hours of drying (according to European test cycle, ETAG 004). The runoff of the facade was collected and investigated for the presence of nAg particles. A suite of different electron-microscopic methods such as HR-SEM (high resolution scanning electron microscopy), TEM-EDX (transmission electron microscopy coupled with an energy dispersive x-ray system), and HAADF (high angular annular dark field detector), were applied to identify the nAg in the runoff samples. The total Ag content of the samples was quantified using ICP-MS (inductively coupled plasma mass spectrometry). The results from the microscopic analyses clearly demonstrate that nAg particles are released from the facade during rain events. The particles are about 10nm in diameter and occur as individual, spherical entities. The results of the ICP-MS measurements show that Ag concentrations in the range of a few micrograms per liter are released. Morones et al. (2005) demonstrated that nAg particles smaller than 10nm can enter bacterial cells. In our experimental study we have found nAg particles of exactly that size range released from paints on facades. The use of nAg particles in outdoor applications with a direct path to the aquatic environment therefore needs to be evaluated carefully. Potential Human Health Impacts of Nanotechnology Nanotechnology has been described as the next industrial revolution. Approximately 600 commercial nanoproducts are already on the market. Many more novel applications are anticipated in electronics, energy, nanoengineered devices, environmental remediation, and nanomedicine. Nanomaterials are defined as engineered materials with a least one dimension in the range of 1-100nm. Engineered nanomaterials have unique chemical and physical properties compared with micron-sized or bulk materials. Some nanomaterials have been shown to have highly reactive surfaces that may induce toxicity upon interaction with biological systems; however, predicting the exact properties of these materials that may be linked with adverse environmental and human health impacts is technically challenging. Identification of specific chemical and physical properties of nanomaterials responsible for cellular toxicity will enable development of manufacturing methods and post processing steps to eliminate intrinsic toxicity. Physical and chemical properties of asbestos fibers and carbon nanotubes relevant for toxicity include fiber length, bioavailable metals, and biopersistence. This interdisciplinary research collaboration establishes interim nanosafety precautions for research in nanotechnology based on administrative, personal protection, and engineering controls to avoid inhalation or dermal exposure. Some nanomaterials pose additional safety concerns related to chemical catalytic and explosive properties. This research was supported by a Superfund Basic Research Program Grant (NIEHS P42 ES013660), an NSF NIRT Grant (DMI-050661), an NIH Grant R01 ES016178, and an EPA Grant (RD-83386201). Microbial Cytotoxicity of Carbon-Based
Nanomaterials: Implications for River Water and Wastewater Effluent This study evaluates the cytotoxicity of four carbon-based nanomaterials (CBNs) - single-walled carbon nanotubes (SWNTs), multiwalled carbon nanotubes (MWNTs), aqueous phase C60 nanoparticles (aq-nC60), and colloidal graphite - in gram negative and gram positive bacteria. The potential impacts of CBNs on microorganisms in natural and engineered aquatic systems are also evaluated. SWNTs inactivate the highest percentage of cells in monocultures of Escherichia coli, Pseudomonas aeruginosa, Bacillus subtilis, and Staphylococcus epidermis, as well as in the diverse microbial communities of river water and wastewater effluent. Bacterial cytotoxicity displays time dependence in these systems, with longer exposure times accentuating toxicity in monocultures with initial tolerance for SWNTs. NOM adsorbed to SWNT aggregates reduces bacterial attachment but does not mitigate toxicity toward attached cells. CBN toxicity in bacterial monocultures was a poor predictor of microbial inactivation in chemically and biologically complex environmental samples. Green Nanotechnology: It's the
Right Thing to Do This paper will present an overview of the state of Green Nanotechnology. Drawing on the principles of Green Chemistry, Green Engineering and sustainability, Green Nanotechnology offers a way to responsibly develop this new industrial technology. Green Nanotechnology has two main components; one addresses processes and the other addresses products. Processes primarily include synthesis methods to make nanomaterials
in a manner that is environmentally benign. Included in these methods
are use of alternative solvents such as CO2 or water, catalytic
vs. stoichiometric reactions, self-assembly, lowered energy methods such
as use of microwaves or biological templating, and use of renewable materials.
Processes also include improving the environmental footprint of current
means of synthesis and manufacturing such as using nanoscale membranes
for chemical separations or using nanoscale (particularly heterogeneous)
catalysts in current chemical or material processes. Fate of Synthetic Nanomaterials in Plants
and Aquatic Systems The rapid development of nanotechnology in the past decade has revolutionalized the landscape of modern science and engineering and raised public concerns about the potential adverse effects of synthetic nanomaterials on human health and environmental sustainability. Maynard et al. have recently devised a ten-year query into safe nanotechnology. At the center of this investigation lies the fundamental issue of hydrophobicity of nanomaterials in the liquid phase. When discharged into the environment through laboratory or industry outlets, nanomaterials likely encounter a vast amount of organic matter and biological molecules and species to initiate interactions. Consequently covalently or noncovalently modified nanomaterials may become suspended to gain bioavailability and biocompatibility. When transported from the freshwater to seawater, nanomaterials may further transform resulting from a change of salinity and the intricate biomodifications by aquatic organisms. Less mobile nanomaterials may settle into soils to interact with bacteria, microbial, and plankton. This presentation describes recent studies on the fate of nanomaterials in ecological systems. Specifically we show the uptake of fullerene-natural organic matter complexes by rice and pepper plants, ingestion of micro- and nanoplastic beads by brine shrimp in saltwater, and translocation of quantum dots across the cell walls of algae. Through these studies we wish to convey our observation that the physical properties of nanomaterials are a major determinant for their fates in biological and ecological systems. We also wish to illustrate the rich biophysics and biology at the interfaces of nanotechnology and biophysics, biology, materials, and environmental science and engineering. Amphiphilic Polymer Nanotubes for Separation and Sensing We have introduced a new class of amphiphilic macromolecules that comprises hydrophilic and hydrophobic functionalities in each repeat unit of the polymer. These polymers form micelle type assemblies in polar solvents and inverse micelle type assemblies in apolar solvents. We have also synthesized polymers having two hydrophilic functionalities in each repeat unit of the polymer. These polymers have been found to form vesicle type assemblies in water. We have explored the possibility of utilizing these micelle and vesicle type assemblies in separation of small molecules and large biomolecules. We hypothesized that high throughput separation is feasible, if we convert the micelles and vesicles into nanotubes. Towards this objective, we decorated the nanopores of polycarbonate membranes using micelle and vesicle forming polymers synthesized by us. We anticipated that the vesicles formed from our amphiphilic polymer will functionalize the nanopores and concurrently reduce the pore diameter of the polycarbonate membranes. Such functionalization preferably results in the formation of polymer nanotubes due to polyvalent interaction. The functionalization was carried out by treating the commercially available polycarbonate membrane with SnCl2, which imparted positive charge on the membrane surface. Then, a solution containing vesicle type assemblies was filtered through the membrane. To find out whether the filtration process modified the nanopores, the polycarbonate template was dissolved to liberate the nanostructures. TEM images of the liberated nanostructures were found to be polymer nanotubes. The inner diameter of the polymer nanotubes were measured by diffusion of water through the polymer nanotubes embedded in the polycarbonate membranes. By carrying out ion transport experiments using the functionalized polycarbonate membranes, we could ascertain the charge of the polymer nanotubes’ interior. Further, by filtering a polymer with complementary charge through the polymer nanotubes, we could modulate the pore size as well as the interior charge of the polymer nanotubes. Such modified membranes were used to separate small molecules based on size, charge and hydrophobicity. We also demonstrated that the amphiphilic polymer functionalized membranes can separate biomolecules such as proteins, based on size and pI. Realizing the Potential of Nanotechnology
for Environmental Applications Nanotechnology has the ability to improve our ability to prevent, detect, and remove environmental contaminants in air, water, and soil in a cost effective and environmentally friendly manner. Particles of “nano” size have been shown to exhibit enhanced or novel properties including reactivity, greater sensing capability, increased mechanical strength, and stronger redox potential. Recent research has also shown that alteration of surface accompanied by the induction of new functions can enable the manipulation of nanomaterial properties and fine-tuning for specific environmental applications including remediation and treatment, detection and monitoring, and catalysis. To facilitate the responsible development of nanotechnology for environmental applications, the U.S. Environmental Protection Agency, through the Science to Achieve Results (STAR) grants program, has developed an extramural research program. The research associated with the 2001 and 2002 solicitations has concluded. This presentation will discuss the impact of STAR research results on the state of science of environmental applications of nanotechnology and assess the extent to which this research addressed research priorities identified in these solicitations. Highlights from the International
Environmental Nanotechnology Conference: Applications and Implications
October 7-9, 2008 in Chicago, IL On October 7-9, 2008 the U.S. Environmental Protection Agency held its first International Environmental Nanotechnology Conference in Region 5. This landmark conference featured state of the art research on the use of nanotechnology to detect, control and remove environmental pollutants and the measurement of the effects of the release of engineered nanomaterials into the environment on the ecosystem and human health. This Information was shared with over130 scientists from Africa, Australia, Asia, Europe, and North America. Region 5 EPA and Headquarters cosponsored the event with the National; Science Foundation, the U.S. Army, the U. S. Navy, The U.S. Department of Energy, the Agency for Toxic Substance and Disease Registry, the National Institute of Environmental Health Sciences, and the University of Illinois at Chicago’s Great Lakes Center for Occupational and Environmental Safety and Health. The two and a half day conference began with opening remarks from Bharat Mathur, Deputy Regional Administrator of the U.S. EPA Region 5, an address on the nanotechnology perspective and activity at the U.S. EPA Office of Research and Development (ORD) by George Gray, U.S. EPA Assistant Administrator for Research and Development and U.S. Federal Interagency and International Perspectives on Nanotechnology. Topics included nanomaterial use for water, soil, and sediment remediation using nanoparticulate zerovalent iron, air and water pollution control and the use of chemically functionalized nanomaterials such thiol self-assembled monolayered mesoporous silica (thiol-SAMMS) for mercury removal from ground water. Current, emerging and future technologies for sensing and monitoring environmental pollutants, exposure and toxicity of nanomaterials to the ecosystem including bacteria, microbes, animals, and humans were discussed. The environmental fate and transport of man made nanoparticles and materials containing manufactured nanoparticles such as carbon nanotubes and other fullerenes, iron oxide and quantum dots were discussed. New information was presented on remediation, sensing of environmental pollutants and air and water pollution control such the use of on-site prepared nanozerovalent iron remove chlorinated organic solvents, information from environmental applications of nanocrystaline metal oxides to air and water pollution control and metal oxide nanoparticles use as biosensors. The toxicity, exposure, fate and transport of engineered nanomaterials such as the interactions and of multiwalled carbon nanotubes and other fullerenes with natural organic matter and life cycle impacts of quantum dots in nanosensors for monitoring pollutants were presented. Reaching for the Stars? The EU's New Chemicals
Policy as a Test Bed for Nanotechnology Regulation There is currently no dedicated body of law which regulates nanotechnologies at the EU level. Instead, there are a patchwork of potentially relevant pieces of legislation (including, but not limited to, employee health and safety, product liability and environmental controls). At the same time, the EU accepts that existing laws may require modification as the body of scientific knowledge on nanotechnologies increases. Having entered into force in June 2007, the EU Regulation on the Registration, Evaluation and Authorization of Chemicals (commonly known as “REACH”) will require the scrutiny of some 30,000 of the more than 100,000 chemical substances currently on the EU market. Replacing around 40 pieces of existing legislation, REACH requires producers and other users of chemicals to register, and potentially test, substances manufactured in or imported into the EU in quantities greater than one tonne per annum. Registration with the newly formed European Chemicals Agency is also required for chemical substances in certain ‘articles’, where the chemical substances in those articles are intended to be released during normal conditions of use. Although there is no reference in REACH to nanomaterials (or nanosubstances or nanotechnology), ECHA has stated that the provisions of the Regulation apply equally to substances at the nano and non-nano levels. There is a wealth of current debate between the chemical industry, the nanotechnology sector and EU regulators (including the EU Commission) as to exactly how and in what manner REACH will apply to nanomaterials. What is certain, however, is that this Regulation will work as a test bed for the wider governance of nanomaterials in the EU. At the same time, the nanotechnology sector is likely to represent a significant test of effectiveness for the REACH Regulation. Will it really live up to its ambitious aims in an area where there is a distinct paucity of both toxicity information and accepted scientific testing methodologies? It is anticipated that REACH is likely to lead to the generation of significant amounts of data on the intrinsic properties (at micro and macro levels) of 30,000 chemical substances. This information is, in turn, likely to have a wider, equally significant, knock-on impact on how nanotechnologies are regulated. This paper will address the regulation of nanotechnologies under REACH and discuss potential consequences in the context of wider EU nanotechnology governance issues. Stabilization of Carbon Nanotubes in Fresh
Surface Waters Carbon nanotubes (CNTs) will be introduced into aqueous environments due to their increasing production and application. Therefore, there is increasing concern over their environmental behavior and fate, which is greatly dependent on their stability in the aqueous phase. In this study, eight types of fresh surface waters sampled from Hangzhou City (Zhejiang Province, China) were examined to stabilize multiwalled CNTs (MWCNTs). The MWCNTs in particulate aggregates could not be stabilized in the waters either by shaking (140 rpm, one week) or by sonication (40 KHz, 150 W, 1 h). Stabilities of surfactant-facilitated MWCNT suspensions in the waters were significantly dependent on the type of surfactant and water. SDBS-stabilized MWCNTs suspended well in the waters. For TX100-facilitated MWCNT suspension, only the influent water of the municipal sewage treatment plant could partly precipitate the MWCNTs at the suspension-water ratios of 3:7 and 1:9. For CTAB-facilitated MWCNT suspension, all the waters used could completely destabilize the suspended MWCNTs at the suspension-water ratios of 3:7 and 1:9. Negatively-charged colloids and anions in the waters were speculated to coagulate and precipitate the CTAB-stabilized MWCNTs. The cations and pH may not play an important role in the destabilization of MWCNTs in the waters in this study. Local Nanotechnology Policymaking In 2007 Cambridge, MA began a public policy process to address concerns about the manufacturing or processing of nanomaterials within the community. This effort was initiated by the City Council, but carried out by the Public Health Department. Utilizing rich local expertise and interest the Cambridge Nanomaterial Advisory Committee was convened in August of 2007, met monthly for six months thereafter, and contributed to a policy recommendation that was assembled by the Public Health Department. These recommendations supported four actions on the part of the City of Cambridge, but did not advocate for local regulations to specifically govern nanomaterials use in the community. The four recommendations were 1) to develop a survey, in cooperation with the fire department and the local emergency planning committee, to determine the extent and nature of nanomaterials used in the community; 2) to seek collaboration necessary to outline a set of “best practices” for healthy and safe management of nanomaterials in research and manufacturing; 3) to develop consumer-friendly information on the department website that will provide basic background on nanomaterials, their uses and benefits, the areas of uncertainty about health effects, and some general information on the presence of these nanomaterials in products that are available for consumer purchase and; 4) to submit an update on the status of health information, Cambridge-based nanomaterials usage, and regulatory oversight at the state and federal levels. A presentation to discuss this process and the implementation of these recommendations will include an overview of the toxicological, political, philosophical, and regulatory questions that were raised by the advisory committee and the department. Further discussion of the challenges that emerged during implementation will be discussed. Finally, comparisons with efforts to regulate the biotech industry in Cambridge will be presented as a possible blueprint for other emerging technologies. New ‘Green’, Scalable Approaches
for Purification and Size Separation of Carbon Nanotubes Carbon nanotube (CNT) fabrication methods require metal catalysts, which are invariably present in the end product. Additional by-products of high-temperature fabrication include graphitic and amorphous carbon species and fullerenes. While raw carbon nanotube materials can be generated relatively inexpensively, there still remains a lack of low cost, scalable purification techniques to produce high purity, homogenous CNT fractions. Drawbacks to existing purification methods include scale-up efficiencies, incomplete contaminate removal and defect generation in the side-walls of CNTs. To address the bottleneck in post-production, scalable CNT processing we have developed a series of novel aqueous-based methods: (1) mechanical processing of crude CNT materials, (2) continuous micron-scale and nano-scale hydrodynamic size separation of CNTs with self-cleaning mesh filters, (3) magnetic gradient fractionation in a glycerol gradient and; (4) power-dialysis/electrophoresis to remove < 0.5 nm amorphous carbon species (Provisional Patent, NIST docket #07-0027, "Scalable descaling, debulking, debundling, catalyst removal and shortening of carbon nanotubes using grit shear methods."). In this presentation, we describe step-wise enrichment and fractionation of commercially obtained AP CNT materials as monitored using spectroscopic methods. We also address issues of uniformity in sample preparation and measurement protocols that are required to enable quantitative comparison of low-to-high grade AP CNTs in their raw, intermediate and purified states. Aggregation Behavior of
C60 Fullerene Water Suspension in the Presence of Natural Organic Materials C60 fullerene is a new allotrope of carbon and one of the most studied engineered nanoparticles with a wide range of applications in electronics, biomedics, and pharmaceutics. Even though C60 fullerene is virtually insoluble in water, but it forms a colloidal suspension upon contacting with water, which is quite stable at low ionic strength. The stability of C60 aggregates in water affects their mobility, bioavailability and toxicity to the living organisms. Previous studies showed that natural organic materials (NOM) have pronounced effects on the aggregation behavior of C60 fullerene. The objective of this study was to examine the effects of NOM structural properties on the aggregation behavior of fullerene water suspension (FWS). Fulvic acid (FA), tannic acid (TA), and two structurally different humic acids (HA1 and HA7) were used in this study as model NOMs. HA1 and HA7 were the 1st and 7th sequentially extracted fractions of HA from an organic soil and were significantly different in their polarities and molecular sizes. FWS was prepared by sonicating a benzene solution of C60 in pure water, then completely evaporating the benzene from water. Aggregation was induced by addition of varying amounts of Ca2+ to the FWS at the presence of 5 mg/L of each NOM sample. Zeta potential (ζ) and size of the fullerene aggregates were measured using laser Doppler velocimetry (LDV) and dynamic light scattering (DLS) techniques. The rate of aggregate size growth was measured by consecutive DLS measurements for 1000 seconds after addition of Ca2+ to the FWS. The ζ of pure FWS decreased to a more negative value after addition of any type of NOMs, leading to a more stable colloidal system. Addition of Ca2+ to the FWS + NOM system caused an increase in the ζ of aggregates almost uniformly for all types of NOM. Critical coagulation concentration (CCC) was calculated equal to 14.5, 6.5, 5.4, and 3.7 mM Ca2+ for HA7, HA1, FA, and TA, respectively. The order of increasing CCCs was positively correlated to the NOMs molecular size. Thus NOM promoted the colloidal stability of FWS, suggesting that steric stability was probably the mechanism of stability. This study highlights the role of NOM in the fate of manufactured nanoparticles in the environment and links the structural properties of NOM to their interaction with manufactured nanoparticles. Engineered Applications of Carbon
Nanotubes in Reverse Osmosis Membranes Decline in water quantity and quality has accelerated the adoption of desalination as a reliable source of potable water. Widespread implementation of membrane-based water treatment technologies, however, is constrained by the energy requirements of conventional membrane desalination. A fundamental redesign of reverse osmosis (RO) membranes will be needed to meet water resource needs in an energy constrained environment. The overarching aim of the proposed research is to reduce the energy demands of membrane-based desalination by increasing membrane permeability and reducing fouling. This project exploits the unique properties of single walled carbon nanotubes (SWNTs) to advance the design of novel RO membranes with improved flux and delayed biofouling. Quantum Dot Transformation under Simulated Environmental Conditions Preliminary Characterization of the Interaction Mechanisms of Engineered Nanomaterials with DNA Exposure to engineered nanomaterials through normal manufacturing processes (via inhalation or skin absorption) or through intentional therapeutic or diagnostic procedures (via oral ingestion or subcutaneous injection) is an immediate and significant concern for human health and safety. This concern derives from the observation that certain nanomaterials have the potential to generate reactive oxygen species (ROS) in biological environments. ROS in the form of free radicals are naturally present in the body, however, an overabundance of free radicals can overwhelm the body’s natural antioxidant defense system and lead to oxidative stress. Oxidative damage to the body’s genomic DNA is one of the consequences of oxidative stress. It is not known at a fundamental molecular level if engineered nanomaterials promote or hinder the formation of free radicals in the body or how these nanomaterials might interact with specific molecular targets such as DNA. By using simple solutions of calf thymus DNA and various types of gold nanoparticles (Au-NPs) as preliminary model systems, the present work aims to elucidate the fundamental interaction mechanisms of nanomaterials with DNA that will enable continued and deeper research into the potential mechanisms of nanomaterial interactions (if any) with the DNA in mammalian cells. Probabilistic Exposure Modeling
of Engineered Nanoparticles in the Environment An elementary step towards a quantitative assessment of the risks of new compounds to the environment is to calculate their predicted environmental concentrations (PEC). The aim of this study was to use a life-cycle perspective to model the quantities of engineered nanoparticles released into the environment. The quantification was based on a substance flow analysis of nanoparticles from products to air, soil and water. To cope with uncertainties concerning the estimation of the model parameters (e.g. transfer and partitioning coefficients or emission factors) as well as uncertainties about the exposure causal mechanisms (e.g. level of compound production and application), we utilized and combined probabilistic methods and sensitivity and uncertainty analysis. The method was applied to the engineered nanoparticles titanium dioxide, silver, carbon nanotubes, fullerenes, ZnO and carbon black. The PEC-values obtained with this modeling were then compared to the predicted no effect concentrations (PNEC) derived from the ecotoxicological literature to estimate a possible risk. The expected concentrations of the three nanoparticles in the different environmental compartments vary widely, caused by the different life cycles of the nanoparticle-containing products. The PEC values for nano-TiO2 in water are 0.7 - 16 μg/l and close to or higher than the PNEC value for nano-TiO2 (<1 μg/l). The risk quotients (PEC/PNEC) for CNT and nano-Ag were much smaller than one, therefore comprising no reason to expect adverse effects from those particles. The results of this study make it possible for the first time to carry out a quantitative risk assessment of nanoparticles in the environment and suggest further detailed studies of nano-titanium dioxide. Assessment of the Impact of PEGylated Single-walled Nanotubes (SWNT) in an Anaerobic Environment Research and development of applications for nanoparticles continues to outpace scientific investigations of potential environmental impacts of these new materials. Carbon nanotubes are being explored for biomedical applications because of their theoretical capability to penetrate cell membranes. Their low solubility makes them challenging to work with in biological systems; however, introduction of polar functional groups increases their solubility and their bioavailability. One example is SWNT functionalized with polyethylene glycol chains (SWNT- PEG). SWNT-PEG is potentially bioreactive in the environment. Nontoxic PEG chains are already released to the environment in significant quantities and are rapidly degraded. We assessed microbial community function in response to SWNT-PEG by monitoring methanogenesis, functional gene primers for mcrA gene, and PEG diol dehydratase assay. We assessed microbial community structure using PCR-DGGE and domain-level, as well as group specific primers. Preliminary data show an affect on microbial community structure and function after exposure over a few months.
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