Types Of Engineered Nanomaterials Research Articles

Importance of exposure dynamics of metal-based nano-ZnO, -Cu and -Pb governing the metabolic potential of soil bacterial communities

Metal-based engineered nanomaterials (ENMs) are known to affect bacterial processes and metabolic activities. While testing their negative effects on biological components, studies traditionally rely on initial exposure concentrations and thereby do not take into consideration the dynamic behavior of ENMs that ultimately determines exposure and toxicity (e.g. ion release). Moreover, functional responses of soil microbial communities to ENMs exposure can be caused by both the particulate forms and the ionic forms, yet their relative contributions remain poorly understood. Therefore, we investigated the dynamic changes of exposure concentrations of three different types of ENMs (nano-ZnO, -Cu and -Pb) and submicron particles (SMPs) in relation to their impact on the capacity of soil bacterial communities to utilize carbon substrates. The different ENMs were chosen to differ in dissolution potential. The dynamic exposures of ENMs were considered using a time weighted average (TWA) approach. The joint toxicity of the particulate forms and the ionic forms of ENMs was evaluated using a response addition model. Our results showed that the effect concentrations of spherical nano-ZnO, -Cu and SMPs, and Pb-based perovskites expressed as TWA were lower than expressed as initial concentrations. Both particulate forms and ionic forms of spherical 18nm, 43nm nano-ZnO and 50nm, 100nm nano-Cu contribute to the overall response at the EC50 levels. The particulate forms for 150nm, 200nm and 900nm ZnO SMPs and rod-shaped 78nm nano-Cu mainly affected the soil microbial metabolic potential, while the Cu ions released from spherical 25nm nano-Cu, 500nm Cu SMPs and Pb ions released from perovskites mainly described the effects to bacterial communities. Our results indicate that the dynamic exposure of ENMs and relative contributions of particles and ions require consideration in order to pursue a naturally realistic assessment of environmental risks of metal-based ENMs.

Stability of co-existing ZnO and TiO2 nanomaterials in natural water: Aggregation and sedimentation mechanisms

The use of diverse engineered nanomaterials (ENMs) potentially leads to the coexistence of multiple ENMs in the natural environment. The fate such as colloidal stability, transport, and transformation of individual ENMs are dedicated to the coexistence of other types of ENMs in the environment. Here, we for the first time investigated the sedimentation behaviors of two most widely used ENMs (i.e. ZnO and TiO2 nanomaterials, nZnO and nTiO2) copresented in the natural water of China. Sedimentation rates (Vs), homo-aggregation (khom, crit) and hetero-aggregation (khet, crit) rate of nZnO and nTiO2 were calculated based on Von Smoluchowski–Stokes equation and the sedimentation mechanisms were systematically analyzed. The results showed that the coexistence of like negative charge nZnO and nTiO2 effectively enhanced the stability of either ENM by competing hetero-aggregation with natural colloids (NCs) and reducing to form homo-aggregates by the hindrance effect on particle collision. In the natural water, homo-aggregation, hetero-aggregation between ENMs and NCs, as well as the hetero-aggregation between nZnO and nTiO2 were the main aggregation and sedimentation mechanisms. The coexistence of nZnO and nTiO2 made Vs of nZnO decreased by 30.7–49.1% and Vs of nTiO2 decreased by a factor of 42.4%. Value of khet.crit between nZnO and NCs was 0.084–0.132 L mg−1 day−1, was 0.038 L mg−1 day−1 between nTiO2 and NCs, and was 0.011–0.014 L mg−1 day−1 between nZnO and nTiO2.

Fate of metallic engineered nanomaterials in constructed wetlands: prospection and future research perspectives

Metallic engineered nanomaterials (ENMs) undergo various transformations in the environment which affect their fate, toxicity and bioavailability. Although constructed wetlands (CWs) are applied as treatment systems for waste streams potentially containing metallic ENMs, little is known about the fate and effects of ENMs in CWs. Hence, literature data from related fields such as activated sludge wastewater treatment and natural wetlands is used to predict the fate and effects of ENMs in CWs and to analyze the risk of nanomaterials being released from CWs into surface waters. The ENMs are likely to reach the CW (partly) transformed and the transformations will continue in the CW. The main transformation processes depend on the type of ENM and the ambient environmental conditions in the CW. In general, ENMs are expected to undergo sorption onto (suspended) organic matter and plant roots. Although the risk of ENMs being released at high concentrations from CWs is estimated low, caution is warranted because of the estimated rise in the production of these materials. As discharge of (transformed) ENMs from CWs during normal operation is predicted to be low, future research should rather focus on the effects of system malfunctions (e.g. short-circuiting). Efficient retention in the CW and increasing production volumes in the future entail increasing concentrations within the CW substrate and further research needs to address possible adverse effects caused.

A model for screening and prioritizing consumer nanoproduct risks: A case study from South Africa

The potential risks of the increasing variety and volume of engineered nanomaterials (ENMs) entering into the ecosystem remain poorly quantified. In recent years, information essential to evaluate the ecological risks of ENMs has increased. However, the data are highly fragmented, limited, or severely lacking. This limits the usefulness of the information to support holistic screening and prioritization of potentially harmful ENMs. To screen and prioritize ENMs risks, we adopted a two-phased approach. First, a holistic framework model was developed to integrate a diverse set of factors aimed to assess the potential hazard, exposure, and in turn, risk to the ecosystem of ENMs from a given consumer nanoproduct. Secondly, using published literature we created a database of consumer nanoproduct categories, and types based on embedded ENMs type. The database consisted of eight consumer product categories, eleven different types of ENMs, and twenty-three nanoproduct types. The model results indicates the largest quantities of ENMs were released from sunscreens, textiles, cosmetics and paints with dominant ENMs quantities in descending order (based on quantity) as nTiO2>nZnO>nSiO2>nAg, and nFe2O3. In addition, according to the results from this study, nAg from washing machine were found to likely the highest risk to the environment. Overall, our model-derived results based on the case study illustrated: (i) the holistic framework's ability to screen, prioritize, rank, and compare ENMs potential exposure and risks among different nanoproducts categories and types, (ii) the derived risk estimations could support nanowastes classification with likelihood of non-uniformity of nanowastes classes even from the same nanoproduct category (e.g. cosmetics), and (iii) the lack of a mass-based criteria specific for EMNs impedes realistic exposure and risk evaluation in the ecological systems.

Interaction of engineered nanomaterials with hydrophobic organic pollutants

As nanomaterials become an increasing part of everyday consumer products, it is imperative to monitor their potential release during production, use and disposal, and to assess their impact on the health of humans and the ecosystem. This necessitates research to better understand how the properties of engineered nanomaterials (ENMs) lead to their accumulation and redistribution in the environment, and to assess whether they could become novel pollutants or if they can affect the mobility and bioavailability of other toxins. This study focuses on understanding the influence of nanostructured-TiO2 and the interaction of multi-walled carbon nanotubes with organic pollutants in water. We studied the adsorption and water phase dispersion of model pollutants with relatively small water solubility (i.e., two- and three-ring polyaromatic hydrocarbons and insecticides) with respect to ENMs. The sorption of pollutants was measured based on water phase analysis, and by separating suspended particles from the water phase and analyzing dried samples using integrated thermal–chromatographic–mass spectroscopic (TGA/GC/MS) techniques. Solid phase analysis using a combination of TGA/GC/MS is a novel technique that can provide real-time quantitative analysis and which helps to understand the interaction of hydrophobic organic pollutants and ENMs. The adsorption of these contaminants to nanomaterials increased the concentration of the contaminants in the aqueous phase as compared to the ‘real’ partitioning due to the octanol–water partitioning. The study showed that ENMs can significantly influence the adsorption and dispersion of hydrophobic/low water soluble contaminants. The type of ENM, the exposure to light, and the water pH have a significant influence on the partitioning of pollutants.

Gravity-driven transport of three engineered nanomaterials in unsaturated soils and their effects on soil pH and nutrient release

The gravity-driven transport of TiO2, CeO2, and Cu(OH)2 engineered nanomaterials (ENMs) and their effects on soil pH and nutrient release were measured in three unsaturated soils. ENM transport was found to be highly limited in natural soils collected from farmland and grasslands, with the majority of particles being retained in the upper 0–3 cm of the soil profile, while greater transport depth was seen in a commercial potting soil. Physical straining appeared to be the primary mechanism of retention in natural soils as ENMs immediately formed micron-scale aggregates, which was exacerbated by coating particles with Suwannee River natural organic matter (NOM) which promote steric hindrance. Small changes in soil pH were observed in natural soils contaminated with ENMs that were largely independent of ENM type and concentration, but differed from controls. These changes may have been due to enhanced release of naturally present pH-altering ions (Mg2+, H+) in the soil via substitution processes. These results suggest ENMs introduced into soil will likely be highly retained near the source zone.

Applications of the comet assay in particle toxicology: air pollution and engineered nanomaterials exposure.

Exposure to ambient air particles is associated with elevated levels of DNA strand breaks (SBs) and endonuclease III, formamidopyrimidine DNA glycosylase (FPG) and oxoguanine DNA glycosylase-sensitive sites in cell cultures, animals and humans. In both animals and cell cultures, increases in SB and in oxidatively damaged DNA are seen after exposure to a range of engineered nanomaterials (ENMs), including carbon black, carbon nanotubes, fullerene C60, ZnO, silver and gold. Exposure to TiO2 has generated mixed data with regard to SB and oxidatively damaged DNA in cell cultures. Nanosilica does not seem to be associated with generation of FPG-sensitive sites in cell cultures, while large differences in SB generation between studies have been noted. Single-dose airway exposure to nanosized carbon black and multi-walled carbon nanotubes in animal models seems to be associated with elevated DNA damage levels in lung tissue in comparison to similar exposure to TiO2 and fullerene C60. Oral exposure has been associated with augmented DNA damage levels in cells of internal organs, although the doses have been typically very high. Intraveneous and intraperitoneal injection of ENMs have shown contradictory results dependent on the type of ENM and dose in each set of experiments. In conclusion, the exposure to both combustion-derived particles and ENMs is associated with increased levels of DNA damage in the comet assay. Particle size, composition and crystal structure of ENM are considered important determinants of toxicity, whereas their combined contributions to genotoxicity in the comet assay are yet to be thoroughly investigated.

Modeling physicochemical interactions affecting in vitro cellular dosimetry of engineered nanomaterials: application to nanosilver.

Engineered nanomaterials (ENMs) possess unique characteristics affecting their interactions in biological media and biological tissues. Systematic investigation of the effects of particle properties on biological toxicity requires a comprehensive modeling framework which can be used to predict ENM particokinetics in a variety of media. The Agglomeration-diffusion-sedimentation-reaction model (ADSRM) described here is stochastic, using a direct simulation Monte Carlo method to study the evolution of nanoparticles in biological media, as they interact with each other and with the media over time. Nanoparticle diffusion, gravitational settling, agglomeration, and dissolution are treated in a mechanistic manner with focus on silver ENMs (AgNPs). The ADSRM model utilizes particle properties such as size, density, zeta potential, and coating material, along with medium properties like density, viscosity, ionic strength, and pH, to model evolving patterns in a population of ENMs along with their interaction with associated ions and molecules. The model predictions for agglomeration and dissolution are compared with in vitro measurements for various types of ENMs, coating materials, and incubation media, and are found to be overall consistent with measurements. The model has been implemented for an in vitro case in cell culture systems to inform in vitro dosimetry for toxicology studies, and can be directly extended to other biological systems, including in vivo tissue subsystems by suitably modifying system geometry.

Examining the Cellular Uptake of Engineered Nanomaterials

Nanomaterials have attracted great attention for numerous applications in chemical, biological, and industrial world because of their fascinating physicochemical properties. In particular, understanding the mechanism of engineered nanomaterials (ENs) uptake by cells is important for various biomedical applications including for biosensors, imaging, intracellular drug and gene delivery, and toxicity studies (Han et al. 2007). Spontaneous penetration of functionalized cationic Au NPs has shown cell membrane disruption and cytotoxicity, thus limiting their utility (Chen et al. 2009). The objective of this work is to study and quantify the cellular uptake of three types of ENs (CNTs, Au nanoparticles (NPs), Silica and ZnO NPs) and their corresponding mechanism of action using immunofluorescence staining, ultrastructural characterization (HRTEM), Electrochemical Cell-substrate Impedance Sensing (ECIS) and bioanalytical analysis (ICP-OES). Another recent literature have indicated that Au NPs (5 nm diameter with “special” surface chemistries or arrangements) protected by an amphiphilic monolayer can non-disruptively penetrate cell membrane to deliver drugs, nutrients or biosensors (Verma et al. 2008). Although it seems that ENs can be taken up by cells, the evidence is disparate and the mechanism of uptake is either unclear or in their infancy. This is because of lack of accurate data on the physicochemical properties such as size including surface area, size distribution, chemical composition (purity crystallinity, electronic properties, etc.), solubility, shape and aggregation; and surface structure including surface reactivity, groups and protein corona and their relationship to cellular uptake. Of particular importance is the protein corona, which affects how nanoparticles are internalized by cells and cleared from the body. When NPs are exposed to biological fluid such as media in a cell culture, proteins can bind to the surface of the nanoparticle to form a protein corona. In this study, we first comprehensively characterized the starting EN dispersed in cell media (using DLS, BET, FTIR, Raman, XRD and HRSEM). Next, NPs were exposed to different cell types (A549, NIH 3T3 and PC12 cells) for either 1 or 2 days. The goal here is to address three questions – (a) Do ENs penetrate into cells and how does intracellular trafficking of ENs occur? (b) Does uptake of ENs vary with cell type? (c) Is uptake driven by physiochemical factors such as size, aggregation, shape, functionalization, corona, composition, dose and time? Figure 1 shows typical studies of cellular uptake of EN analyzed using VP-SEM, ICP-OES, immunofluorescence, and ECIS. Our initial evidence shows nanoparticle transport and uptake (see ICP-OES) and cell morphological disruptions. Furthermore, ECIS studies indicate the ability to longitudinally monitor impedance data of exposed cells over 5 days. In the paper, we will present detailed investigation on the influence of other EN physicochemical properties on cellular transport and uptake.

Nanotechnology patenting trends through an environmental lens: analysis of materials and applications

Many international groups study environmental health and safety (EHS) concerns surrounding the use of engineered nanomaterials (ENMs). These researchers frequently use the “Project on Emerging Nanotechnologies” (PEN) inventory of nano-enabled consumer products to prioritize types of ENMs to study because estimates of life-cycle ENM releases to the environment can be extrapolated from the database. An alternative “snapshot” of nanomaterials likely to enter commerce can be determined from the patent literature. The goal of this research was to provide an overview of nanotechnology intellectual property trends, complementary to the PEN consumer product database, to help identify potentially “risky” nanomaterials for study by the nano-EHS community. Ten years of nanotechnology patents were examined to determine the types of nano-functional materials being patented, the chemical compositions of the ENMs, and the products in which they are likely to appear. Patenting trends indicated different distributions of nano-enabled products and materials compared to the PEN database. Recent nanotechnology patenting is dominated by electrical and information technology applications rather than the hygienic and anti-fouling applications shown by PEN. There is an increasing emphasis on patenting of nano-scale layers, coatings, and other surface modifications rather than traditional nanoparticles, and there is widespread use of nano-functional semiconductor, ceramic, magnetic, and biological materials that are currently less studied by EHS professionals. These commonly patented products and the nano-functional materials they contain may warrant life-cycle evaluations to determine the potential for environmental exposure and toxicity. The patent and consumer product lists contribute different and complementary insights into the emerging nanotechnology industry and its potential for introducing nanomaterials into the environment.

Searching for global descriptors of engineered nanomaterial fate and transport in the environment.

Engineered nanomaterials (ENMs) are a new class of environmental pollutants. Researchers are beginning to debate whether new modeling paradigms and experimental tests to obtain model parameters are required for ENMs or if approaches for existing pollutants are robust enough to predict ENM distribution between environmental compartments. This Account outlines how experimental research can yield quantitative data for use in ENM fate and exposure models. We first review experimental testing approaches that are employed with ENMs. Then we compare and contrast ENMs against other pollutants. Finally, we summarize the findings and identify research needs that may yield global descriptors for ENMs that are suitable for use in fate and transport modeling. Over the past decade, researchers have made significant progress in understanding factors that influence the fate and transport of ENMs. In some cases, researchers have developed approaches toward global descriptor models (experimental, conceptual, and quantitative). We suggest the following global descriptors for ENMs: octanol-water partition coefficients, solid-water partition coefficients, attachment coefficients, and rate constants describing reactions such as dissolution, sedimentation, and degradation. ENMs appear to accumulate at the octanol-water interface and readily interact with other interfaces, such as lipid-water interfaces. Batch experiments to investigate factors that influence retention of ENMs on solid phases are very promising. However, ENMs probably do not behave in the same way as dissolved chemicals, and therefore, researchers need to use measurement techniques and concepts more commonly associated with colloids. Despite several years of research with ENMs in column studies, available summaries tend to discuss the effects of ionic strength, pH, organic matter, ENM type, packing media, or other parameters qualitatively rather than reporting quantitative values, such as attachment efficiencies, that would facilitate comparison across studies. Only a few structure-activity relationships have been developed for ENMs so far, but such evaluations will facilitate the understanding of the reactivities of different forms of a single ENM. The establishment of predictive capabilities for ENMs in the environment would enable accurate exposure assessments that would assist in ENM risk management. Such information is also critical for understanding the ultimate disposition of ENMs and may provide a framework for improved engineering of nanomaterials that are more environmentally benign.

Electrophysiology Methods to Investigate Molecular Interactions Between Nanoparticles and Lipid Bilayers

A diverse range of molecular interactions can occur between engineered nanomaterials (ENM) and cell membranes, some of which could lead to toxic outcomes. The ability to measure, predict, and control these molecular interactions would enable ENM to be designed to be both effective and safe. While some classes of ENM-membrane interactions involve participation of proteins or other membrane-associated macromolecules, ENM can also interact directly with the membrane's lipid bilayer. This latter class of interactions can be characterized using electrophysiology methods, in which transient ionic currents through a synthetic bilayer lipid membrane (BLM) are measured to obtain a rapid and sensitive signature of BLM disruption. In this study, we describe application of electrophysiology methods to investigate molecular interactions between a variety of ENM and BLM. To explore the effect of ENM surface properties on ENM-BLM interactions, BLM were challenged with custom-fabricated polypropargyl glycolide nanoparticles having a variety of surface functional groups. Polyethylene glycol functionalized ENM triggered ionic current spikes having a duration of milliseconds, while carboxyl-functionalized ENM generated both rapid current spikes and extended integral conductance. Ion selectivity of the ENM-generated conductance was investigated by measuring reversal potential of transmembrane currents at various applied potentials in the presence of a 10:1 KCl gradient. Reversal potentials for different types of ENM varied from 0 mV, indicating no ion preference, to 37 mV, indicating preference for K+. To explore the effect of BLM composition on ENM-BLM interactions, two BLM compositions were tested: pure DOPC, and a 3:1 ratio of POPC:POPE. For a variety of ENM, the DOPC BLM consistently exhibited ion currents at lower concentrations and lower transmembrane voltages than did the POPC:POPE BLM. These results demonstrate the utility and versatility of electrophysiology methods to characterize molecular interactions between ENM and BLM.

Workplace practices for engineered nanomaterial manufacturers

The growth in nanotechnology has prompted a focus on the development of occupational health and safety recommendations for those working with engineered nanomaterials (ENM) at both the laboratory and the manufacturing levels. Although the nascent field of nanotoxicology has shown that some nanoparticles may present a health hazard to humans, risk assessments for all types of ENM are not possible. Hence, a precautionary approach to handling of these materials is recommended along with the development of a comprehensive health and safety program for the workplace. The traditional hierarchy of exposure controls emphasizes reducing the hazard as close to the source as possible by using elimination or substitution. Alternative control methods include engineering controls, administrative or work practice controls, and finally personal protective equipment, in order of decreasing priority. There is now ample evidence that some degree of exposure control can be achieved with each of these control methods, so that a comprehensive program will incorporate each, depending on the circumstances of the engineered nanomaterial use.

Endotoxin contamination of engineered nanomaterials

Endotoxin has established health impacts and may be a potential confounding factor in toxicity studies of engineered nanomaterials (ENM). We aimed to characterize endotoxin contamination for a representative set of carbon-based ENM. The established method for quantifying endotoxin relies on its activity in a complex biochemical assay system. Because of their physical and chemical properties, measurement of endotoxin associated with many ENM presents non-trivial technical challenges. We have made progress in identifying and implementing methods for ENM analysis with respect to endotoxin content, revealing varying levels of endotoxin contamination in the ENM examined here. The physical association of ENM and endotoxin and their shared physiological effects suggest the possibility that contaminating endotoxin may contribute to the toxicity that is ascribed to ENM. We found in this small number of samples that endotoxin levels were not related to type of ENM or surface area but may be introduced randomly during manufacture.

P019 Perception and reproduction of whole body rotation in standing subjects

Metal-based engineered nanomaterials (ENMs) are known to affect bacterial processes and metabolic activities. While testing their negative effects on biological components, studies traditionally rely on initial exposure concentrations and thereby do not take into consideration the dynamic behavior of ENMs that ultimately determines exposure and toxicity (e.g. ion release). Moreover, functional responses of soil microbial communities to ENMs exposure can be caused by both the particulate forms and the ionic forms, yet their relative contributions remain poorly understood. Therefore, we investigated the dynamic changes of exposure concentrations of three different types of ENMs (nano-ZnO, -Cu and -Pb) and submicron particles (SMPs) in relation to their impact on the capacity of soil bacterial communities to utilize carbon substrates. The different ENMs were chosen to differ in dissolution potential. The dynamic exposures of ENMs were considered using a time weighted average (TWA) approach. The joint toxicity of the particulate forms and the ionic forms of ENMs was evaluated using a response addition model. Our results showed that the effect concentrations of spherical nano-ZnO, -Cu and SMPs, and Pb-based perovskites expressed as TWA were lower than expressed as initial concentrations. Both particulate forms and ionic forms of spherical 18 nm, 43 nm nano-ZnO and 50 nm, 100 nm nano-Cu contribute to the overall response at the EC50 levels. The particulate forms for 150 nm, 200 nm and 900 nm ZnO SMPs and rod-shaped 78 nm nano-Cu mainly affected the soil microbial metabolic potential, while the Cu ions released from spherical 25 nm nano-Cu, 500 nm Cu SMPs and Pb ions released from perovskites mainly described the effects to bacterial communities. Our results indicate that the dynamic exposure of ENMs and relative contributions of particles and ions require consideration in order to pursue a naturally realistic assessment of environmental risks of metal-based ENMs.