Blacksburg, VA, United States
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Li S.,U.S. Environmental Protection Agency | Pan X.,Texas Tech University | Wallis L.K.,U.S. Environmental Protection Agency | Fan Z.,Texas Tech University | And 2 more authors.
Chemosphere | Year: 2014

With a dramatic rise in complexity, needs of nanotoxicology research go beyond simple forms of nanomaterials. This study compared the phototoxicity of nano-TiO2 and graphene-TiO2 nanocomposite (GNP). GNP was synthesized based on a hydrothermal method, which simultaneously performed the reduction of graphene oxide and nano-TiO2 loading. A series of acute toxicity tests of nano-TiO2, graphene and GNP was performed on two aquatic organisms, Daphnia magna and Oryzias latipes. Fast and substantial agglomeration and sedimentation of nanoparticles in test media and surface attachment of nano-TiO2 and GNP on D. magna surface was observed. Similar phototoxicity of nano-TiO2 and GNP for both species existed, though compared with nano-TiO2, GNP had a 2.3-fold increase in visible light photocatalytic ROS generation. In summary, this study demonstrated the significance of illumination spectrum, particle behavior, and species sensitivity on nanophototoxicity, and the needs for research on increasingly sophisticated functional materials. © 2014 Elsevier Ltd.


Feltis B.N.,RMIT University | Feltis B.N.,Monash University | Feltis B.N.,NanoSafe Inc. | O'Keefe S.J.,RMIT University | And 9 more authors.
Nanotoxicology | Year: 2012

Significant public and scientific concerns remain for the use of nanoparticles (NPs) in commercial products, particularly those applied topically for skin care. There are currently a range of metal oxides formulated into many sunscreens that are present at the nanoscale. In this study, we sought to determine the effect of the size and dispersion of one type of these NPs (zinc oxide) on immune cell function and cytotoxicity for human macrophages and monocytes, which are key cells for particle and debris clearance in the skin. We have found that particle size and coating, but surprisingly, not agglomeration, are key determinates of nanoparticle cytotoxicity in an in vitro culture system of human immune cells. Most importantly, we found that this nanoparticle-induced cellular immune signalling, can be decoupled from cytotoxicity and surface coating, so that at an equivalent cytotoxic load, smaller particles induce a greater cellular response. © 2012 Informa UK, Ltd.


Poda A.R.,U.S. Army | Bednar A.J.,U.S. Army | Kennedy A.J.,U.S. Army | Harmon A.,U.S. Army | And 5 more authors.
Journal of Chromatography A | Year: 2011

The ability to detect and identify the physiochemical form of contaminants in the environment is important for degradation, fate and transport, and toxicity studies. This is particularly true of nanomaterials that exist as discrete particles rather than dissolved or sorbed contaminant molecules in the environment. Nanoparticles will tend to agglomerate or dissolve, based on solution chemistry, which will drastically affect their environmental properties. The current study investigates the use of field flow fractionation (FFF) interfaced to inductively coupled plasma-mass spectrometry (ICP-MS) as a sensitive and selective method for detection and characterization of silver nanoparticles. Transmission electron microscopy (TEM) is used to verify the morphology and primary particle size and size distribution of precisely engineered silver nanoparticles. Subsequently, the hydrodynamic size measurements by FFF are compared to dynamic light scattering (DLS) to verify the accuracy of the size determination. Additionally, the sensitivity of the ICP-MS detector is demonstrated by fractionation of μg/L concentrations of mixed silver nanoparticle standards. The technique has been applied to nanoparticle suspensions prior to use in toxicity studies, and post-exposure biological tissue analysis. Silver nanoparticles extracted from tissues of the sediment-dwelling, freshwater oligochaete Lumbriculus variegatus increased in size from approximately 31-46. nm, indicating a significant change in the nanoparticle characteristics during exposure. © 2010.


Ma H.,Continent Development | Ma H.,University of Wisconsin - Milwaukee | Wallis L.K.,Continent Development | Diamond S.,NanoSafe Inc. | And 3 more authors.
Environmental Pollution | Year: 2014

The present study investigated the impact of solar UV radiation on ZnO nanoparticle toxicity through photocatalytic ROS generation and photo-induced dissolution. Toxicity of ZnO nanoparticles to Daphnia magna was examined under laboratory light versus simulated solar UV radiation (SSR). Photocatalytic ROS generation and particle dissolution were measured on a time-course basis. Two toxicity mitigation assays using CaCl2 and N-acetylcysteine were performed to differentiate the relative importance of these two modes of action. Enhanced ZnO nanoparticle toxicity under SSR was in parallel with photocatalytic ROS generation and enhanced particle dissolution. Toxicity mitigation by CaCl2 to a less extent under SSR than under lab light demonstrates the role of ROS generation in ZnO toxicity. Toxicity mitigation by N-acetylcysteine under both irradiation conditions confirms the role of particle dissolution and ROS generation. These findings demonstrate the importance of considering environmental solar UV radiation when assessing ZnO nanoparticle toxicity and risk in aquatic systems. © 2014 Elsevier Ltd. All rights reserved.


Wallis L.K.,U.S. Environmental Protection Agency | Diamond S.A.,NanoSafe Inc. | Ma H.,University of Wisconsin - Milwaukee | Hoff D.J.,U.S. Environmental Protection Agency | And 2 more authors.
Science of the Total Environment | Year: 2014

There is limited information on the chronic effects of nanomaterials to benthic organisms, as well as environmental mitigating factors that might influence this toxicity. The present study aimed to fill these data gaps by examining various growth endpoints (weight gain, instantaneous growth rate, and total protein content) for up to a 21 d sediment exposure of TiO2 nanoparticles (nano-TiO2) to a representative benthic species, Hyalella azteca. An uncoated standard, P25, and an Al(OH)3 coated nano-TiO2 used in commercial products were added to sediment at 20mg/L or 100 mg/L Under test conditions, UVexposure alonewas shown to be a greater cause of toxicity than even these high levels of nano-TiO2 exposure, indicating that different hazards need to be addressed in toxicity testing scenarios. In addition, this study showed the effectiveness of a surface coating on the decreased photoactivity of the material, as the addition of an Al(OH)3 coating showed a dramatic decrease in reactive oxygen species (ROS) production. However, this reduced photoactivity was found to be partially restored when the coating had been degraded, leading to the need for future toxicity testswhich examine the implications of weathering events on particle surface coatings. © 2014 Elsevier B.V.


PubMed | U.S. Environmental Protection Agency, NanoSafe Inc. and University of Wisconsin - Milwaukee
Type: Journal Article | Journal: The Science of the total environment | Year: 2015

Due to their inherent phototoxicity and inevitable environmental release, titanium dioxide nanoparticles (nano-TiO2) are increasingly studied in the field of aquatic toxicology. One of the particular interests is the interactions between nano-TiO2 and natural organic matter (NOM). In this study, a series of experiments was conducted to study the impacts of Suwannee River natural organic matter (SRNOM) on phototoxicity and particle behaviors of nano-TiO2. For Daphnia magna, after the addition of 5mg/L SRNOM, LC50 value decreased significantly from 1.03 (0.89-1.20) mg/L to 0.26 (0.22-0.31) mg/L. For zebrafish larvae, phototoxic LC50 values were 39.9 (95% CI, 25.9-61.2) mg/L and 26.3 (95% CI, 18.3-37.8) mg/L, with or without the presence of 5mg/L SRNOM, respectively. There was no statistically significant change of these LC50 values. The impact of SRNOM on phototoxicity of nano-TiO2 was highly dependent on test species, with D. magna being the more sensitive species. The impact on particle behavior was both qualitatively and quantitatively examined. A global predictive model for particle behavior was developed with a three-way interaction of SRNOM, TiO2 concentration, and time and an additive effect of ionic strength. Based on power analyses, 96-h exposure in bioassays was recommended for nanoparticle-NOM interaction studies. The importance of reactive oxygen species (ROS) quenching of SRNOM was also systematically studied using a novel exposure system that isolates the effects of environmental factors. These experiments were conducted with minimal impacts of other important interaction mechanisms (NOM particle stabilization, NOM UV attenuation, and NOM photosensitization). This study highlighted both the particle stabilization and ROS quenching effects of NOM on nano-TiO2 in an aquatic system. There is an urgent need for representative test materials, together with key environmental factors, for future risk assessment and regulations of nanomaterials.


Li S.,U.S. Environmental Protection Agency | Wallis L.K.,U.S. Environmental Protection Agency | Ma H.,U.S. Environmental Protection Agency | Diamond S.A.,NanoSafe Inc.
Science of the Total Environment | Year: 2014

This study investigated phototoxicity of TiO2 nanoparticles (nano-TiO2) to a freshwater benthic amphipod (Hyalella azteca) using 48-h and 96-h bioassays. Thorough monitoring of particle interactions with exposure media (Lake Superior water, LSW) and the surface of organisms was performed using dynamic light scattering, UV/Vis spectroscopy, and Scanning Electron Microscopy. Large agglomeration and sedimentation (>77%) in LSW was observed after 0.5h. A simulated solar radiation (SSR)-favored surface attachment of nanoparticles was observed, indicating enhanced phototoxicity with the increased attachment. A 96-h median lethal concentration (LC50) of 29.9mg/L in H. azteca was calculated, with a daily 4-h UV exposure of 2.2W/m2. Phototoxicity of nano-TiO2 under SSR had a 21-fold increase as compared to that under ambient laboratory light. This phototoxicity was also dependent on UV dose, with calculated LC50s around 22.9 (95% CI, 20.5-23.3)Wh/m2 when exposed to 20mg/L nano-TiO2. Also, H. azteca exhibited negative phototaxis in the presence of shelters, indicating that other factors might play a role in environmental systems. Finally, the environmental implications of nano-TiO2 to benthic organisms were illustrated, emphasizing the importance of various environmental factors in the ultimate phototoxicity. This increased phototoxicity and its complex interactions with various environmental factors suggest further investigations are needed for future risk assessment of photoactive nanomaterials to benthic organisms. © 2013 Elsevier B.V.


Ma H.,U.S. Environmental Protection Agency | Diamond S.A.,NanoSafe Inc.
Environmental Toxicology and Chemistry | Year: 2013

Zebrafish embryos have been used increasingly to evaluate nanomaterial toxicity. The present study compared phototoxicity of TiO2 nanoparticles with zebrafish at 4 life stages (embryos, yolk-sac larvae, free-swimming larvae, and juvenile) under simulated sunlight using the 96-h standard toxicity assay. Yolk-sac larvae were found to be the most sensitive to TiO2 phototoxicity, suggesting that the widely used zebrafish embryo test may not fully or accurately predict hazard and risk of these nanoparticles to small fish. © 2013 SETAC.


Grant
Agency: Department of Defense | Branch: Air Force | Program: SBIR | Phase: Phase I | Award Amount: 99.17K | Year: 2011

ABSTRACT: NANOSAFE INC. proposes the development and demonstration of the nanoparticle 3DPT3D Periodic Table which is an advanced database and software modeling tool for predicting nanoparticle toxicity, bioavailability, persistence, biological fate/transport, and life cycle risks from 1) quantitative structural properties used to characterize nanoscale particles (e.g., chemical composition, size, surface chemistry/reactivity, dissolution kinetics), 2) the media in which nanoparticles may be dispersed (e.g., serum, saliva, lung fluid, buffers), and 3) the assays used to quantify toxicological effects in vitro and in vivo, as well as acellularly (i.e., chemical methods). Results of Phase I development will yield a flexible electronic database that can be queried by end users to link, for example, physico-chemical properties of nanoscale materials with environmental outcomes predicted by nano-specific quantitative structure activity relationships (QSARs). The beta-version of the 3DPT will be populated with experimentally-derived data parameters for a limited set of nanoscale materials with demonstrated significance to emerging defense applications of nanotechnologies. BENEFIT: The proposed research offers the potential to significantly enhance Air Force ability to accurately identify and manage nanotechnology human health risks, with strong potential for extrapolation to general use by the greater research community. In particular, the proposed electronic database will integrate into a single location, information on basic properties of nanoscale materials (such as size, surface area, etc.) and their reported toxicological effects and fate/transport as measured in vitro and in vivo. This will facilitate efforts already underway at Air Force research laboratories to develop assays and characterization approaches suitable for assessing the human health risks of nanoscale materials. Ultimately, this work will contribute substantially to DOD efforts to improve military operations through applications of nanotechnology while simultaneously ensuring the safety and sustainability of these operations.


Li S.,U.S. Environmental Protection Agency | Wallis L.K.,U.S. Environmental Protection Agency | Diamond S.A.,NanoSafe Inc. | Ma H.,U.S. Environmental Protection Agency | Hoff D.J.,U.S. Environmental Protection Agency
Environmental Toxicology and Chemistry | Year: 2014

Toxicity of titanium dioxide nanoparticles (nano-TiO2) to aquatic organisms can be greatly increased after exposure to ultraviolet (UV) radiation. This phenomenon has received some attention for water column species; however, investigations of nano-TiO2 phototoxicity for benthic organisms are still limited. In the present study, bioassays of 3 representative benthic organisms (Hyalella azteca, Lumbriculus variegatus, and Chironomus dilutus) were conducted to evaluate nano-TiO2 phototoxicity. When exposed to 20mg/L of nano-TiO2 and various light intensities (0-30W/m2), H. azteca was the most sensitive, with a median lethal dose of 40.7 (95% confidence interval, 36.3-44.7) Wh/m2, and hence is a potential model organism in future toxicological guidelines for photoactive nanomaterials to freshwater benthos. Without the presence of nano-TiO2, no mortality was observed in L. variegatus and C. dilutus exposed to UV intensity ranging from 0W/m2 to 41W/m2. However, a sharp drop of H. azteca survival was observed when UV intensity was higher than 9.4W/m2, demonstrating the importance of UV-only effects on the ultimate phototoxicity of nanomaterials. Furthermore, both bioavailability and surface attachment of nano-TiO2 onto organisms were affected by the exposure scenario, supported by the exposure scenario-dependent phototoxicity seen in H. azteca and C. dilutus. Overall, the present study demonstrates the importance of species sensitivity and exposure scenarios in future test guidelines of nano-phototoxicity. © 2014 SETAC.

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