A novel platform for pulmonary and cardiovascular toxicological characterization of inhaled engineered nanomaterials

Effective density of inhaled environmental and engineered nanoparticles and its impact on the lung deposition and dosimetry

BACKGROUND

Airborne environmental and engineered nanoparticles (NPs) are inhaled and deposited in the respiratory system. The inhaled dose of such NPs and their deposition location in the lung determines their impact on health. When calculating NP deposition using particle inhalation models, a common approach is to use the bulk material density, ρb, rather than the effective density, ρeff. This neglects though the porous agglomerate structure of NPs and may result in a significant error of their lung-deposited dose and location.

RESULTS

Here, the deposition of various environmental NPs (aircraft and diesel black carbon, wood smoke) and engineered NPs (silica, zirconia) in the respiratory system of humans and mice is calculated using the Multiple-Path Particle Dosimetry model accounting for their realistic structure and effective density. This is done by measuring the NP ρeff which was found to be up to one order of magnitude smaller than ρb. Accounting for the realistic ρeff of NPs reduces their deposited mass in the pulmonary region of the respiratory system up to a factor of two in both human and mouse models. Neglecting the ρeff of NPs does not alter significantly the distribution of the deposited mass fractions in the human or mouse respiratory tract that are obtained by normalizing the mass deposited at the head, tracheobronchial and pulmonary regions by the total deposited mass. Finally, the total deposited mass fraction derived this way is in excellent agreement with those measured in human studies for diesel black carbon.

CONCLUSIONS

The doses of inhaled NPs are overestimated by inhalation particle deposition models when the ρb is used instead of the real-world effective density which can vary significantly due to the porous agglomerate structure of NPs. So the use of realistic ρeff, which can be measured as described here, is essential to determine the lung deposition and dosimetry of inhaled NPs and their impact on public health.

Silica encapsulation of ZnO nanoparticles reduces their toxicity for cumulus cell-oocyte-complex expansion

Background

Metal oxide nanoparticles (NPs) are increasingly used in many industrial and biomedical applications, hence their impact on occupational and public health has become a concern. In recent years, interest on the effect that exposure to NPs may exert on human reproduction has grown, however data are still scant. In the present work, we investigated whether different metal oxide NPs interfere with mouse cumulus cell-oocyte complex (COC) expansion.

Methods

Mouse COCs from pre-ovulatory follicles were cultured in vitro in the presence of various concentrations of two types of TiO₂ NPs (JRC NM-103 and NM-104) and four types of ZnO NPs (JRC NM-110, NM-111, and in-house prepared uncoated and SiO₂-coated NPs) and the organization of a muco-elastic extracellular matrix by cumulus cells during the process named cumulus expansion was investigated.

Results

We show that COC expansion was not affected by the presence of both types of TiO₂ NPs at all tested doses, while ZnO NM-110 and NM-111 induced strong toxicity and inhibited COCs expansion at relatively low concentration. Medium conditioned by these NPs showed lower toxicity, suggesting that, beside ion release, inhibition of COC expansion also depends on NPs per se. To further elucidate this, we compared COC expansion in the presence of uncoated or SiO₂-coated NPs. Differently from the uncoated NPs, SiO₂-coated NPs underwent slower dissolution, were not internalized by the cells, and showed an overall lower toxicity. Gene expression analysis demonstrated that ZnO NPs, but not SiO₂-coated ZnO NPs, affected the expression of genes fundamental for COC expansion. Dosimetry analysis revealed that the delivered-to-cell mass fractions for both NPs was very low.

Conclusions

Altogether, these results suggest that chemical composition, dissolution, and cell internalization are all responsible for the adverse effects of the tested NPs and support the importance of a tailored, safer-by-design production of NPs to reduce toxicity.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12989-021-00424-z.

Environmentally Relevant Iron Oxide Nanoparticles Produce Limited Acute Pulmonary Effects in Rats at Realistic Exposure Levels

Iron is typically the dominant metal in the ultrafine fraction of airborne particulate matter. Various studies have investigated the toxicity of inhaled nano-sized iron oxide particles (FeO_xNPs) but their results have been contradictory, with some indicating no or minor effects and others finding effects including oxidative stress and inflammation. Most studies, however, did not use materials reflecting the characteristics of FeO_xNPs present in the environment. We, therefore, analysed the potential toxicity of FeO_xNPs of different forms (Fe₃O₄, α-Fe₂O₃ and γ-Fe₂O₃) reflecting the characteristics of high iron content nano-sized particles sampled from the environment, both individually and in a mixture (FeO_x-mix). A preliminary in vitro study indicated Fe₃O₄ and FeO_x-mix were more cytotoxic than either form of Fe₂O₃ in human bronchial epithelial cells (BEAS-2B). Follow-up in vitro (0.003, 0.03, 0.3 µg/mL, 24 h) and in vivo (Sprague–Dawley rats, nose-only exposure, 50 µg/m³ and 500 µg/m³, 3 h/d × 3 d) studies therefore focused on these materials. Experiments in vitro explored responses at the molecular level via multi-omics analyses at concentrations below those at which significant cytotoxicity was evident to avoid detection of responses secondary to toxicity. Inhalation experiments used aerosol concentrations chosen to produce similar levels of particle deposition on the airway surface as were delivered in vitro. These were markedly higher than environmental concentrations. No clinical signs of toxicity were seen nor effects on BALF cell counts or LDH levels. There were also no significant changes in transcriptomic or metabolomic responses in lung or BEAS-2B cells to suggest adverse effects.

Human brain microvascular endothelial cell pairs model tissue-level blood-brain barrier function

The blood-brain barrier plays a critical role in delivering oxygen and nutrients to the brain while preventing the transport of neurotoxins. Predicting the ability of potential therapeutics and neurotoxicants to modulate brain barrier function remains a challenge due to limited spatial resolution and geometric constraints offered by existing in vitro models. Using soft lithography to control the shape of microvascular tissues, we predicted blood-brain barrier permeability states based on structural changes in human brain endothelial cells. We quantified morphological differences in nuclear, junction, and cytoskeletal proteins that influence, or indicate, barrier permeability. We established a correlation between brain endothelial cell pair structure and permeability by treating cell pairs and tissues with known cytoskeleton-modulating agents, including a Rho activator, a Rho inhibitor, and a cyclic adenosine monophosphate analog. Using this approach, we found that high-permeability cell pairs showed nuclear elongation, loss of junction proteins, and increased actin stress fiber formation, which were indicative of increased contractility. We measured traction forces generated by high- and low-permeability pairs, finding that higher stress at the intercellular junction contributes to barrier leakiness. We further tested the applicability of this platform to predict modulations in brain endothelial permeability by exposing cell pairs to engineered nanomaterials, including gold, silver-silica, and cerium oxide nanoparticles, thereby uncovering new insights into the mechanism of nanoparticle-mediated barrier disruption. Overall, we confirm the utility of this platform to assess the multiscale impact of pharmacological agents or environmental toxicants on blood-brain barrier integrity.

Integrated Transcriptomics, Metabolomics, and Lipidomics Profiling in Rat Lung, Blood, and Serum for Assessment of Laser Printer-Emitted Nanoparticle Inhalation Exposure-Induced Disease Risks

Laser printer-emitted nanoparticles (PEPs) generated from toners during printing represent one of the most common types of life cycle released particulate matter from nano-enabled products. Toxicological assessment of PEPs is therefore important for occupational and consumer health protection. Our group recently reported exposure to PEPs induces adverse cardiovascular responses including hypertension and arrythmia via monitoring left ventricular pressure and electrocardiogram in rats. This study employed genome-wide mRNA and miRNA profiling in rat lung and blood integrated with metabolomics and lipidomics profiling in rat serum to identify biomarkers for assessing PEPs-induced disease risks. Whole-body inhalation of PEPs perturbed transcriptional activities associated with cardiovascular dysfunction, metabolic syndrome, and neural disorders at every observed time point in both rat lung and blood during the 21 days of exposure. Furthermore, the systematic analysis revealed PEPs-induced transcriptomic changes linking to other disease risks in rats, including diabetes, congenital defects, auto-recessive disorders, physical deformation, and carcinogenesis. The results were also confirmed with global metabolomics profiling in rat serum. Among the validated metabolites and lipids, linoleic acid, arachidonic acid, docosahexanoic acid, and histidine showed significant variation in PEPs-exposed rat serum. Overall, the identified PEPs-induced dysregulated genes, molecular pathways and functions, and miRNA-mediated transcriptional activities provide important insights into the disease mechanisms. The discovered important mRNAs, miRNAs, lipids and metabolites may serve as candidate biomarkers for future occupational and medical surveillance studies. To the best of our knowledge, this is the first study systematically integrating in vivo, transcriptomics, metabolomics, and lipidomics to assess PEPs inhalation exposure-induced disease risks using a rat model.

A novel method for textile odor removal using engineered water nanostructures

The malodor attached to textiles not only causes indoor environmental pollution but also endangers people's health even at low concentrations. Existing technologies cannot effectively eliminate the odor. Herein, an effective and environmentally friendly technology was proposed to address this challenging issue. This technology utilizes electrospraying process to produce Engineered Water Nanostructures (EWNS) in a controllable manner. Upon application of a high voltage to the Taylor cone, EWNS can be generated from the condensed vapor water through a Peltier element. Smoking, cooking and perspiration, considered the typical indoor malodorous gases emitted from human activities, were studied in this paper. A headspace SPME method in conjunction with GC-MS was employed for the extraction, detection and quantification of any odor residues. Results indicated that EWNS played a significant role in the deodorization process with removal efficiencies for the three odors were 95.3 ± 0.1%, 100.0 ± 0.0% and 43.7 ± 2.3%, respectively. The Reactive Oxygen Species (ROS) contained in the EWNS, mainly hydroxyl (OH˙) and superoxide radicals are the possible mechanisms for the odor removal. These ROS are strong oxidative and highly reactive and have the ability to convert odorous compounds to non-odorous compounds through various chemical reaction mechanisms. This study showed clearly the potential of the proposed method in the field of odor removal and can be applied in the battle against indoor air pollution.

Development of reference metal and metal oxide engineered nanomaterials for nanotoxicology research using high throughput and precision flame spray synthesis approaches

There is a growing need to develop and characterize reference metal and metal oxide engineered nanomaterials (ENMs) of high purity and tunable intrinsic properties suitable for nanotoxicology research. Here a high throughput (volume) and precision flame spray pyrolysis (FSP) approach coupled with state-of-the-art characterization techniques are utilized to generate such reference ENMs. The lab-based and industrially relevant FSP system, termed as Versatile Engineered Nanomaterials Generation System (VENGES), synthesizes the metals and metal oxides, at high throughput manner with controlled properties, such as primary particle size, aggregate diameter, shape, crystallinity, stoichiometry and surface chemistry. A nanopanel of nine reference ENMs (silica, silver, silver supported on silica, alumina, ceria and iron oxide) was synthesized and characterized using combined electron microscopy, advanced spectroscopic techniques and physical analyses (e.g., BET, XRD, TEM, pycnometry, XPS, ICP-MS and FTIR). ENMs show a high degree of chemical purity and stoichiometry, and low content of carbon residuals, and are sterile and free of bacteria and endotoxins. Further, their colloidal properties and their implication in in-vitro dosimetry have been also investigated in both environmental and test biological media. The suitability of reference ENMs and protocols developed in this study brings forth new arenas to generate reliable and reproducible toxicological data in an effort to reduce conflicting and contradicting inter-laboratory data on relative toxic effects of ENMs.

Effective delivery of sonication energy to fast settling and agglomerating nanomaterial suspensions for cellular studies: Implications for stability, particle kinetics, dosimetry and toxicity

Typical in vitro assays used for high throughput toxicological screening and measuring nano-bio interactions are conducted by pipetting suspensions of engineered nanomaterials (ENMs) dispersed in nutrient-rich culture media directly onto cells. In order to achieve fairly monodisperse and stable suspensions of small agglomerates, ultrasonic energy is usually applied to break apart large agglomerates that can form upon suspension in liquid. Lack of standardized protocols and methods for delivering sonication energy can introduce variability in the ENM suspension properties (e.g. agglomerate size, polydispersity, suspension stability over time), and holds significant implications for in vitro dosimetry, toxicity, and other nano-bio interactions. Careful assessment of particle transformations during dispersion preparation and sonication is therefore critical for accurate interpretation of in vitro toxicity studies. In this short communication, the difficulties of preparing stable suspensions of rapidly settling ENMs are presented. Furthermore, methods to optimize the delivery of the critical sonication energy required to break large agglomerates and prepare stable, fairly monodispersed suspensions of fast settling ENMs are presented. A methodology for the efficient delivery of sonication energy in a discrete manner is presented and validated using various rapidly agglomerating and settling ENMs. The implications of continuous vs. discrete sonication on average hydrodynamic diameter, and polydispersity was also assessed for both fast and slow settling ENMs. For the rapidly agglomerating and settling ENMs (Ag15%/SiO2, Ag and CeO2), the proposed discrete sonication achieved a significant reduction in the agglomerate diameter and polydispersity. In contrast, the relatively slow agglomerating and settling Fe2O3 suspension did not exhibit statistically significant differences in average hydrodynamic diameter or polydispersity between the continuous and discrete sonication approaches. Our results highlight the importance of using the proposed material-specific discrete sonication method to effectively deliver the critical sonication energy necessary to reproducibly achieve stable and fairly monodispersed suspensions that are suitable for in vitro toxicity testing.

Nanofiller Presence Enhances Polycyclic Aromatic Hydrocarbon (PAH) Profile on Nanoparticles Released during Thermal Decomposition of Nano-enabled Thermoplastics: Potential Environmental Health Implications

Nano-enabled products are ultimately destined to reach end-of-life with an important fraction undergoing thermal degradation through waste incineration or accidental fires. Although previous studies have investigated the physicochemical properties of released lifecycle particulate matter (called LCPM) from thermal decomposition of nano-enabled thermoplastics, critical questions about the effect of nanofiller on the chemical composition of LCPM still persist. Here, we investigate the potential nanofiller effects on the profiles of 16 Environmental Protection Agency (EPA)-priority polycyclic aromatic hydrocarbons (PAHs) adsorbed on LCPM from thermal decomposition of nano-enabled thermoplastics. We found that nanofiller presence in thermoplastics significantly enhances not only the total PAH concentration in LCPM but most importantly also the high molecular weight (HMW, 4-6 ring) PAHs that are considerably more toxic than the low molecular weight (LMW, 2-3 ring) PAHs. This nano-specific effect was also confirmed during in vitro cellular toxicological evaluation of LCPM for the case of polyurethane thermoplastic enabled with carbon nanotubes (PU-CNT). LCPM from PU-CNT shows significantly higher cytotoxicity compared to PU which could be attributed to its higher HMW PAH concentration. These findings are crucial and make the case that nanofiller presence in thermoplastics can significantly affect the physicochemical and toxicological properties of LCPM released during thermal decomposition.

Evaluation of tumorigenic potential of CeO2 and Fe2O3 engineered nanoparticles by a human cell in vitro screening model

With rapid development of novel nanotechnologies that incorporate engineered nanomaterials (ENMs) into manufactured products, long-term, low dose ENM exposures in occupational settings is forecasted to occur with potential adverse outcomes to human health. Few ENM human health risk assessment efforts have evaluated tumorigenic potential of ENMs. Two widely used nano-scaled metal oxides (NMOs), cerium oxide (nCeO₂) and ferric oxide (nFe₂O₃) were screened in the current study using a sub-chronic exposure to human primary small airway epithelial cells (pSAECs). Multi-walled carbon nanotubes (MWCNT), a known ENM tumor promoter, was used as a positive control. Advanced dosimetry modeling was employed to ascertain delivered vs. administered dose in all experimental conditions. Cells were continuously exposed in vitro to deposited doses of 0.18 μg/cm² or 0.06 μg/cm² of each NMO or MWCNT, respectively, over 6 and 10 weeks, while saline- and dispersant-only exposed cells served as passage controls. Cells were evaluated for changes in several cancer hallmarks, as evidence for neoplastic transformation. At 10 weeks, nFe₂O₃- and MWCNT-exposed cells displayed a neoplastic-like transformation phenotype with significant increased proliferation, invasion and soft agar colony formation ability compared to controls. nCeO₂-exposed cells showed increased proliferative capacity only. Isolated nFe₂O₃ and MWCNT clones from soft agar colonies retained their respective neoplastic-like phenotypes. Interestingly, nFe₂O₃-exposed cells, but not MWCNT cells, exhibited immortalization and retention of the neoplastic phenotype after repeated passaging (12 - 30 passages) and after cryofreeze and thawing. High content screening and protein expression analyses in acute exposure ENM studies vs. immortalized nFe₂O₃ cells, and isolated ENM clones, suggested that long-term exposure to the tested ENMs resulted in iron homeostasis disruption, an increased labile ferrous iron pool, and subsequent reactive oxygen species generation, a well-established tumorigenesis promotor. In conclusion, sub-chronic exposure to human pSAECs with a cancer hallmark screening battery identified nFe₂O₃ as possessing neoplastic-like transformation ability, thus suggesting that further tumorigenic assessment is needed.

Anodically Grown Titania Nanotube Induced Cytotoxicity has Genotoxic Origins

Nanoarchitectures of titania (TiO₂) have been widely investigated for a number of medical applications including implants and drug delivery. Although titania is extensively used in the food, drug and cosmetic industries, biocompatibility of nanoscale titania is still under careful scrutiny due to the conflicting reports on its interaction with cellular matter. For an accurate insight, we performed in vitro studies on the response of human dermal fibroblast cells toward pristine titania nanotubes fabricated by anodic oxidation. The nanotubes at low concentrations were seen to induce toxicity to the cells, whereas at higher concentrations the cell vitality remained on par with controls. Further investigations revealed an increase in the G₀ phase cell population depicting that majority of cells were in the resting rather than active phase. Though the mitochondrial set-up did not exhibit any signs of stress, significantly enhanced reactive oxygen species production in the nuclear compartment was noted. The TiO₂ nanotubes were believed to have gained access to the nuclear machinery and caused increased stress leading to genotoxicity. This interesting property of the nanotubes could be utilized to kill cancer cells, especially if the nanotubes are functionalized for a specific target, thus eliminating the need for any chemotherapeutic agents.

Effects of engineered nanomaterial exposure on macrophage innate immune function

Increasing use of engineered nanomaterials (ENMs) means increased human exposures. Potential adverse effects include those on the immune system, ranging from direct toxicity to impairment of defenses against environmental pathogens and toxins. Effects on lung macrophages may be especially prominent, because they serve to clear foreign materials like ENMs and bacterial pathogens. We investigated the effects of 4 hour exposures over a range of concentrations, of a panel of industry-relevant ENMs, including SiO₂, Fe₂O₃, ZnO, CeO₂, TiO₂, and an Ag/SiO2 composite, on human THP-1 macrophages. Effects on phagocytosis of latex beads, and phagocytosis and killing of Francisella tularensis (FT), as well as viability, oxidative stress and mitochondrial integrity, were measured by automated scanning confocal microscopy and image analysis. Results revealed some notable patterns: 1) Phagocytosis of unopsonized beads was increased, whereas that of opsonized beads was decreased, by all ENMs, with the exception of ZnO, which reduced both opsonized and unopsonized uptake; 2) Uptake of opsonized and unopsonized FT was either impaired or unaffected by all ENMs, with the exception of CeO₂, which increased phagocytosis of unopsonized FT; 3) Macrophage killing of FT tended to improve with all ENMs; and 4) Viability was unaffected immediately following exposures with all ENMs tested, but was significantly decreased 24 hours after exposures to Ag/SiO₂ and ZnO ENMs. The results reveal a complex landscape of ENM effects on macrophage host defenses, including both enhanced and reduced capacities, and underscore the importance of robust hazard assessment, including immunotoxicity assessment, of ENMs.

Thermal decomposition of nano-enabled thermoplastics: Possible environmental health and safety implications

Nano-enabled products (NEPs) are currently part of our life prompting for detailed investigation of potential nano-release across their life-cycle. Particularly interesting is their end-of-life thermal decomposition scenario. Here, we examine the thermal decomposition of widely used NEPs, namely thermoplastic nanocomposites, and assess the properties of the byproducts (released aerosol and residual ash) and possible environmental health and safety implications. We focus on establishing a fundamental understanding on the effect of thermal decomposition parameters, such as polymer matrix, nanofiller properties, decomposition temperature, on the properties of byproducts using a recently-developed lab-based experimental integrated platform. Our results indicate that thermoplastic polymer matrix strongly influences size and morphology of released aerosol, while there was minimal but detectable nano-release, especially when inorganic nanofillers were used. The chemical composition of the released aerosol was found not to be strongly influenced by the presence of nanofiller at least for the low, industry-relevant loadings assessed here. Furthermore, the morphology and composition of residual ash was found to be strongly influenced by the presence of nanofiller. The findings presented here on thermal decomposition/incineration of NEPs raise important questions and concerns regarding the potential fate and transport of released engineered nanomaterials in environmental media and potential environmental health and safety implications.

Effects of Laser Printer-Emitted Engineered Nanoparticles on Cytotoxicity, Chemokine Expression, Reactive Oxygen Species, DNA Methylation, and DNA Damage: A Comprehensive in Vitro Analysis in Human Small Airway Epithelial Cells, Macrophages, and Lymphoblasts

BACKGROUND

Engineered nanomaterials (ENMs) incorporated into toner formulations of printing equipment become airborne during consumer use. Although information on the complex physicochemical and toxicological properties of both toner powders and printer-emitted particles (PEPs) continues to grow, most toxicological studies have not used the actual PEPs but rather have primarily used raw toner powders, which are not representative of current exposures experienced at the consumer level during printing.

OBJECTIVES

We assessed the biological responses of a panel of human cell lines to PEPs.

METHODS

Three physiologically relevant cell lines--small airway epithelial cells (SAECs), macrophages (THP-1 cells), and lymphoblasts (TK6 cells)--were exposed to PEPs at a wide range of doses (0.5-100 μg/mL) corresponding to human inhalation exposure durations at the consumer level of 8 hr or more. Following treatment, toxicological parameters reflecting distinct mechanisms were evaluated.

RESULTS

PEPs caused significant membrane integrity damage, an increase in reactive oxygen species (ROS) production, and an increase in pro-inflammatory cytokine release in different cell lines at doses equivalent to exposure durations from 7.8 to 1,500 hr. Furthermore, there were differences in methylation patterns that, although not statistically significant, demonstrate the potential effects of PEPs on the overall epigenome following exposure.

CONCLUSIONS

The in vitro findings obtained in this study suggest that laser printer-emitted engineered nanoparticles may be deleterious to lung cells and provide preliminary evidence of epigenetic modifications that might translate to pulmonary disorders.

Oxidative stress markers are elevated in exhaled breath condensate of workers exposed to nanoparticles during iron oxide pigment production

Markers of oxidative stress and inflammation were analysed in the exhaled breath condensate (EBC) and urine samples of 14 workers (mean age 43  ±  7 years) exposed to iron oxide aerosol for an average of 10  ±  4 years and 14 controls (mean age 39  ±  4 years) by liquid chromatography-electrospray ionization-mass spectrometry/mass spectrometry (LC-ESI-MS/MS) after solid-phase extraction. Aerosol exposure in the workplace was measured by particle size spectrometers, a scanning mobility particle sizer (SMPS) and an aerodynamic particle sizer (APS), and by aerosol concentration monitors, P-TRAK and DustTRAK DRX. Total aerosol concentrations in workplace locations varied greatly in both time and space. The median mass concentration was 0.083 mg m(-3) (IQR 0.063-0.133 mg m(-3)) and the median particle concentration was 66 800 particles cm(-3) (IQR 16,900-86,900 particles cm(-3)). In addition, more than 80% of particles were smaller than 100 nm in diameter. Markers of oxidative stress, malondialdehyde (MDA), 4-hydroxy-trans-hexenale (HHE), 4-hydroxy-trans-nonenale (HNE), 8-isoProstaglandin F2α (8-isoprostane) and aldehydes C6-C12, in addition to markers of nucleic acid oxidation, including 8-hydroxy-2-deoxyguanosine (8-OHdG), 8-hydroxyguanosine (8-OHG), 5-hydroxymethyl uracil (5-OHMeU), and of proteins, such as o-tyrosine (o-Tyr), 3-chlorotyrosine (3-ClTyr), and 3-nitrotyrosine (3-NOTyr) were analysed in EBC and urine by LC-ESI-MS/MS. Almost all markers of lipid, nucleic acid and protein oxidation were elevated in the EBC of workers comparing with control subjects. Elevated markers were MDA, HNE, HHE, C6-C10, 8-isoprostane, 8-OHdG, 8-OHG, 5-OHMeU, 3-ClTyr, 3-NOTyr, o-Tyr (all p  <  0.001), and C11 (p  <  0.05). Only aldehyde C12 and the pH of samples did not differ between groups. Markers in urine were not elevated. These findings suggest the adverse effects of nano iron oxide aerosol exposure and support the utility of oxidative stress biomarkers in EBC. The analysis of urine oxidative stress biomarkers does not support the presence of systemic oxidative stress in iron oxide pigment production workers.

Performance of Particulate Containment at Nanotechnology Workplaces

The evaluation of engineering controls for the production or use of carbon nanotubes (CNTs) was investigated at two facilities. These controls assessments are necessary to evaluate the current status of control performance and to develop proper control strategies for these workplaces. The control systems evaluated in these studies included ventilated enclosures, exterior hoods, and exhaust filtration systems. Activity-based monitoring with direct-reading instruments and filter sampling for microscopy analysis were used to evaluate the effectiveness of control measures at study sites. Our study results showed that weighing CNTs inside the biological safety cabinet can have a 37% reduction on the particle concentration in the worker's breathing zone, and produce a 42% lower area concentration outside the enclosure. The ventilated enclosures used to reduce fugitive emissions from the production furnaces exhibited good containment characteristics when closed, but they failed to contain emissions effectively when opened during product removal/harvesting. The exhaust filtration systems employed for exhausting these ventilated enclosures did not provide promised collection efficiencies for removing engineered nanomaterials from furnace exhaust. The exterior hoods were found to be a challenge for controlling emissions from machining nanocomposites: the downdraft hood effectively contained and removed particles released from the manual cutting process, but using the canopy hood for powered cutting of nanocomposites created 15%-20% higher ultrafine (<500 nm) particle concentrations at the source and at the worker's breathing zone. The microscopy analysis showed that CNTs can only be found at production sources but not at the worker breathing zones during the tasks monitored.

Advanced computational modeling for in vitro nanomaterial dosimetry

Background

Accurate and meaningful dose metrics are a basic requirement for in vitro screening to assess potential health risks of engineered nanomaterials (ENMs). Correctly and consistently quantifying what cells “see,” during an in vitro exposure requires standardized preparation of stable ENM suspensions, accurate characterizatoin of agglomerate sizes and effective densities, and predictive modeling of mass transport. Earlier transport models provided a marked improvement over administered concentration or total mass, but included assumptions that could produce sizable inaccuracies, most notably that all particles at the bottom of the well are adsorbed or taken up by cells, which would drive transport downward, resulting in overestimation of deposition.

Methods

Here we present development, validation and results of two robust computational transport models. Both three-dimensional computational fluid dynamics (CFD) and a newly-developed one-dimensional Distorted Grid (DG) model were used to estimate delivered dose metrics for industry-relevant metal oxide ENMs suspended in culture media. Both models allow simultaneous modeling of full size distributions for polydisperse ENM suspensions, and provide deposition metrics as well as concentration metrics over the extent of the well. The DG model also emulates the biokinetics at the particle-cell interface using a Langmuir isotherm, governed by a user-defined dissociation constant, K_D, and allows modeling of ENM dissolution over time.

Results

Dose metrics predicted by the two models were in remarkably close agreement. The DG model was also validated by quantitative analysis of flash-frozen, cryosectioned columns of ENM suspensions. Results of simulations based on agglomerate size distributions differed substantially from those obtained using mean sizes. The effect of cellular adsorption on delivered dose was negligible for K_D values consistent with non-specific binding (> 1 nM), whereas smaller values (≤ 1 nM) typical of specific high-affinity binding resulted in faster and eventual complete deposition of material.

Conclusions

The advanced models presented provide practical and robust tools for obtaining accurate dose metrics and concentration profiles across the well, for high-throughput screening of ENMs. The DG model allows rapid modeling that accommodates polydispersity, dissolution, and adsorption. Result of adsorption studies suggest that a reflective lower boundary condition is appropriate for modeling most in vitro ENM exposures.

Electronic supplementary material

The online version of this article (doi:10.1186/s12989-015-0109-1) contains supplementary material, which is available to authorized users.

A critical review of in vitro dosimetry for engineered nanomaterials

A major obstacle in the development of accurate cellular models for investigating nanobio interactions in vitro is determination of physiologically relevant measures of dose. Comparison of biological responses to nanoparticle exposure typically relies on administered dose metrics such as mass concentration of suspended particles, rather than the effective dose of particles that actually comes in contact with the cells over the time of exposure. Adoption of recently developed dosimetric methodologies will facilitate determination of effective dose delivered to cells in vitro, thereby improving the accuracy and reliability of in vitro screening data, validation of in vitro with in vivo data, and comparison across multiple datasets for the large variety of nanomaterials currently in the market.

An integrated methodology for the assessment of environmental health implications during thermal decomposition of nano-enabled products

The proliferation of nano-enabled products (NEPs) renders human exposure to engineered nanomaterials (ENMs) inevitable. Over the last decade, the risk assessment paradigm for nanomaterials focused primarily on potential adverse effect of pristine, as-prepared ENMs. However, the physicochemical properties of ENMs may be drastically altered across their life-cycle (LC), especially when they are embedded in various NEP matrices. Of a particular interest is the end-of-life scenario by thermal decomposition. The main objective of the current study is to develop a standardized, versatile and reproducible methodology that allows for the systematic physicochemical and toxicological characterization of the NEP thermal decomposition. The developed methodology was tested for an industry-relevant NEP in order to verify its versatility for such LC investigations. Results are indicative of potential environmental health risks associated with waste from specific NEP families and prompt for the development of safer-by-design approaches and exposure control strategies.

Short-term exposure to engineered nanomaterials affects cellular epigenome

Extensive incorporation of engineered nanomaterials (ENMs) into industrial and biomedical applications increases the risks of exposure to these potentially hazardous materials. While the geno- and cytotoxic effects of ENMs have been investigated, the potential of ENMs to target the cellular epigenome remains largely unknown. Our goal was to determine whether industry relevant ENMs can affect the epigenome at low cytotoxic doses. A panel of cells relevant to inhalation exposures such as human and murine macrophages (THP-1 and RAW264.7, respectively) and human small airway epithelial cells (SAEC) were exposed to printer-emitted engineered nanoparticles (PEPs), mild steel welding fumes (MS-WF), copper oxide (CuO) and titanium dioxide nanoparticles. Toxicological effects, including cytotoxicity, oxidative stress and inflammatory responses were assessed, taking into consideration in vitro dosimetry. The effects of ENMs on cellular epigenome were determined by addressing the global and transposable elements (TEs)-associated DNA methylation and expression of DNA methylation machinery and TEs. The percentage of ENMs-induced cytotoxicity for all cell lines was in the range of 0-15%. Oxidative stress was evident in SAEC after exposure to PEPs and in THP-1 when exposed to CuO. In addition, exposure to ENMs resulted in modest alterations in DNA methylation of two most abundant TEs in mammalian genomes, LINE-1 and Alu/SINE, their transcriptional reactivation, and decreased expression of DNA methylation machinery in a cell-, dose- and ENM-dependent manner. These results indicate that exposure to ENMs at environmentally relevant concentrations, aside from the geno- and cytotoxic effects, can also affect the epigenome of target cells.

Consumer exposures to laser printer-emitted engineered nanoparticles: A case study of life-cycle implications from nano-enabled products

It is well established that printers emit nanoparticles during their operation. To-date, however, the physicochemical and toxicological characterization of "real world" printer-emitted nanoparticles (PEPs) remains incomplete, hampering proper risk assessment efforts. Here, we investigate our earlier hypothesis that engineered nanomaterials (ENMs) are used in toners and ENMs are released during printing (consumer use). Furthermore, we conduct a detailed physicochemical and morphological characterization of PEPs in support of ongoing toxicological assessment. A comprehensive suite of state of the art analytical methods and tools was employed for the physicochemical and morphological characterization of 11 toners widely utilized in printers from major printer manufacturers and their PEPs. We confirmed that a number of ENMs incorporated into toner formulations (e.g. silica, alumina, titania, iron oxide, zinc oxide, copper oxide, cerium oxide, carbon black among others) and released into the air during printing. All evaluated toners contained large amounts of organic carbon (OC, 42-89%), metals/metal oxides (1-33%), and some elemental carbon (EC, 0.33-12%). The PEPs possess a composition similar to that of toner and contained 50-90% OC, 0.001-0.5% EC and 1-3% metals. While the chemistry of the PEPs generally reflected that of their toners, considerable differences are documented indicative of potential transformations taking place during consumer use (printing). We conclude that: (i) Routine incorporation of ENMs in toners classifies them as nano-enabled products (NEPs); (ii) These ENMs become airborne during printing; (iii) The chemistry of PEPs is complex and it reflects that of the toner and paper. This work highlights the importance of understanding life-cycle (LC) nano-EHS implications of NEPs and assessing real world exposures and associated toxicological properties rather than focusing on "raw" materials used in the synthesis of an NEP.

Small airway epithelial cells exposure to printer-emitted engineered nanoparticles induces cellular effects on human microvascular endothelial cells in an alveolar-capillary co-culture model

The printer is one of the most common office equipment. Recently, it was reported that toner formulations for printing equipment constitute nano-enabled products (NEPs) and contain engineered nanomaterials (ENMs) that become airborne during printing. To date, insufficient research has been performed to understand the potential toxicological properties of printer-emitted particles (PEPs) with several studies using bulk toner particles as test particles. These studies demonstrated the ability of toner particles to cause chronic inflammation and fibrosis in animal models. However, the toxicological implications of inhalation exposures to ENMs emitted from laser printing equipment remain largely unknown. The present study investigates the toxicological effects of PEPs using an in vitro alveolar-capillary co-culture model with Human Small Airway Epithelial Cells (SAEC) and Human Microvascular Endothelial Cells (HMVEC). Our data demonstrate that direct exposure of SAEC to low concentrations of PEPs (0.5 and 1.0 µg/mL) caused morphological changes of actin remodeling and gap formations within the endothelial monolayer. Furthermore, increased production of reactive oxygen species (ROS) and angiogenesis were observed in the HMVEC. Analysis of cytokine and chemokine levels demonstrates that interleukin (IL)-6 and MCP-1 may play a major role in the cellular communication observed between SAEC and HMVEC and the resultant responses in HMVEC. These data indicate that PEPs at low, non-cytotoxic exposure levels are bioactive and affect cellular responses in an alveolar-capillary co-culture model, which raises concerns for potential adverse health effects.

Capture, isolation and electrochemical detection of industrially-relevant engineered aerosol nanoparticles using poly (amic) acid, phase-inverted, nano-membranes

Workplace exposure to engineered nanoparticles (ENPs) is a potential health and environmental hazard. This paper reports a novel approach for tracking hazardous airborne ENPs by applying online poly (amic) acid membranes (PAA) with offline electrochemical detection. Test aerosol (Fe2O3, TiO2 and ZnO) nanoparticles were produced using the Harvard (Versatile Engineered Generation System) VENGES system. The particle morphology, size and elemental composition were determined using SEM, XRD and EDS. The PAA membrane electrodes used to capture the airborne ENPs were either stand-alone or with electron-beam gold-coated paper substrates. Cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS) were used to conceptually illustrate that exposure levels of industry-relevant classes of airborne nanoparticles could be captured and electrochemically detected at PAA membranes filter electrodes. CV parameters showed that PAA catalyzed the reduction of Fe2O3 to Fe(2+) with a size-dependent shift in reduction potential (E(0)). Using the proportionality of peak current to concentration, the amount of Fe2O3 was found to be 4.15×10(-17)mol/cm(3) PAA electrodes. Using EIS, the maximum phase angle (Φmax) and the interfacial charge transfer resistance (Rct) increased significantly using 100μg and 1000μg of TiO2 and ZnO respectively. The observed increase in Φmax and Rct at increasing concentration is consistent with the addition of an insulating layer of material on the electrode surface. The integrated VENGES/PAA filter sensor system has the potential to be used as a portable monitoring system.

Real-Time Nanoparticle-Cell Interactions in Physiological Media by Atomic Force Microscopy

Particle-cell interactions in physiological media are important in determining the fate and transport of nanoparticles and biological responses to them. In this work, these interactions are assessed in real time using a novel atomic force microscopy (AFM) based platform. Industry-relevant CeO2 and Fe2O3 engineered nanoparticles (ENPs) of two primary particle sizes were synthesized by the flame spray pyrolysis (FSP) based Harvard Versatile Engineering Nanomaterials Generation System (Harvard VENGES) and used in this study. The ENPs were attached on AFM tips, and the atomic force between the tip and lung epithelia cells (A549), adhered on a substrate, was measured in biological media, with and without the presence of serum proteins. Two metrics were used to assess the nanoparticle cell: the detachment force required to separate the ENP from the cell and the number of bonds formed between the cell and the ENPs. The results indicate that these atomic level ENP-cell interaction forces strongly depend on the physiological media. The presence of serum proteins reduced both the detachment force and the number of bonds by approximately 50% indicating the important role of the protein corona on the particle cell interactions. Additionally, it was shown that particle to cell interactions were size and material dependent.

An integrated approach for the in vitro dosimetry of engineered nanomaterials

BACKGROUND

There is a great need for screening tools capable of rapidly assessing nanomaterial toxicity. One impediment to the development of reliable in vitro screening methods is the need for accurate measures of cellular dose. We present here a methodology that enables accurate determination of delivered to cell dose metrics. This methodology includes (1) standardization of engineered nanomaterial (ENM) suspension preparation; (2) measurement of ENM characteristics controlling delivery to cells in culture; and (3) calculation of delivered dose as a function of exposure time using the ISDD model. The approach is validated against experimentally measured doses, and simplified analytical expressions for the delivered dose (Relevant In Vitro Dose (RID)f function) are derived for 20 ENMs. These functions can be used by nanotoxicologists to accurately calculate the total mass (RIDM), surface area (RIDSA), or particle number (RIDN) delivered to cells as a function of exposure time.

RESULTS

The proposed methodology was used to derive the effective density, agglomerate diameter and RID functions for 17 industrially-relevant metal and metal oxide ENMs, two carbonaceous nanoparticles, and non-agglomerating gold nanospheres, for two well plate configurations (96 and 384 well plates). For agglomerating ENMs, the measured effective density was on average 60% below the material density. We report great variability in delivered dose metrics, with some materials depositing within 24 hours while others require over 100 hours for delivery to cells. A neutron-activated tracer particle system was employed to validate the proposed in vitro dosimetry methodology for a number of ENMs (measured delivered to cell dose within 9% of estimated).

CONCLUSIONS

Our findings confirm and extend experimental and computational evidence that agglomerate characteristics affect the dose delivered to cells. Therefore measurement of these characteristics is critical for effective use of in vitro systems for nanotoxicology. The mixed experimental/computational approach to cellular dosimetry proposed and validated here can be used by nanotoxicologists to accurately calculate the delivered to cell dose metrics for various ENMs and in vitro conditions as a function of exposure time. The RID functions and characterization data for widely used ENMs presented here can together be used by experimentalists to design and interpret toxicity studies.

Quantitative assessment of inhalation exposure and deposited dose of aerosol from nanotechnology-based consumer sprays

This study provides a quantitative assessment of inhalation exposure and deposited aerosol dose in the 14 nm to 20 μm particle size range based on the aerosol measurements conducted during realistic usage simulation of five nanotechnology-based and five regular spray products matching the nano-products by purpose of application. The products were also examined using transmission electron microscopy. In seven out of ten sprays, the highest inhalation exposure was observed for the coarse (2.5-10 μm) particles while being minimal or below the detection limit for the remaining three sprays. Nanosized aerosol particles (14-100 nm) were released, which resulted in low but measurable inhalation exposures from all of the investigated consumer sprays. Eight out of ten products produced high total deposited aerosol doses on the order of 10¹-10³ ng kg^-1 bw per application, ~85-88% of which were in the head airways, only <10% in the alveolar region and <8% in the tracheobronchial region. One nano and one regular spray produced substantially lower total deposited doses (by 2-4 orders of magnitude less), only ~52-64% of which were in the head while ~29-40% in the alveolar region. The electron microscopy data showed nanosized objects in some products not labeled as nanotechnology-based and conversely did not find nano-objects in some nano-sprays. We found no correlation between nano-object presence and abundance as per the electron microscopy data and the determined inhalation exposures and deposited doses. The findings of this study and the reported quantitative exposure data will be valuable for the manufacturers of nanotechnology-based consumer sprays to minimize inhalation exposure from their products, as well as for the regulators focusing on protecting the public health.

Estimating the effective density of engineered nanomaterials for in vitro dosimetry

The need for accurate in vitro dosimetry remains a major obstacle to the development of cost-effective toxicological screening methods for engineered nanomaterials. An important key to accurate in vitro dosimetry is the characterization of sedimentation and diffusion rates of nanoparticles suspended in culture media, which largely depend upon the effective density and diameter of formed agglomerates in suspension. Here we present a rapid and inexpensive method for accurately measuring the effective density of nano-agglomerates in suspension. This novel method is based on the volume of the pellet obtained by bench-top centrifugation of nanomaterial suspensions in a packed cell volume tube, and is validated against gold-standard analytical ultracentrifugation data. This simple and cost-effective method allows nanotoxicologists to correctly model nanoparticle transport, and thus attain accurate dosimetry in cell culture systems, which will greatly advance the development of reliable and efficient methods for toxicological testing and investigation of nano-bio interactions in vitro.

High-throughput screening platform for engineered nanoparticle-mediated genotoxicity using CometChip technology

The likelihood of intentional and unintentional engineered nanoparticle (ENP) exposure has dramatically increased due to the use of nanoenabled products. Indeed, ENPs have been incorporated in many useful products and have enhanced our way of life. However, there are many unanswered questions about the consequences of nanoparticle exposures, in particular, with regard to their potential to damage the genome and thus potentially promote cancer. In this study, we present a high-throughput screening assay based upon the recently developed CometChip technology, which enables evaluation of single-stranded DNA breaks, abasic sites, and alkali-sensitive sites in cells exposed to ENPs. The strategic microfabricated, 96-well design and automated processing improves efficiency, reduces processing time, and suppresses user bias in comparison to the standard comet assay. We evaluated the versatility of this assay by screening five industrially relevant ENP exposures (SiO2, ZnO, Fe2O3, Ag, and CeO2) on both suspension human lymphoblastoid (TK6) and adherent Chinese hamster ovary (H9T3) cell lines. MTT and CyQuant NF assays were employed to assess cellular viability and proliferation after ENP exposure. Exposure to ENPs at a dose range of 5, 10, and 20 μg/mL induced dose-dependent increases in DNA damage and cytotoxicity. Genotoxicity profiles of ZnO>Ag>Fe2O3>CeO2>SiO2 in TK6 cells at 4 h and Ag>Fe2O3>ZnO>CeO2>SiO2 in H9T3 cells at 24 h were observed. The presented CometChip platform enabled efficient and reliable measurement of ENP-mediated DNA damage, therefore demonstrating the efficacy of this powerful tool in nanogenotoxicity studies.

Mycobacteria inactivation using Engineered Water Nanostructures (EWNS)

Airborne transmitted pathogens such as Mycobacterium tuberculosis (Mtb) cause serious, often fatal infectious disease with enormous global health implications. Due to their unique cell wall and slow growth, mycobacteria are among the most resilient microbial forms. Herein we evaluate the ability of an emerging, chemical-free, nanotechnology-based method to inactivate M. parafortuitum (Mtb surrogate). This method is based on the transformation of atmospheric water vapor into engineered water nano-structures (EWNS) via electrospray. We demonstrate that the EWNS can interact with and inactivate airborne mycobacteria, reducing their concentration levels significantly. Additionally, EWNS can inactivate M. parafortuitum on surfaces eight times faster than the control. The mechanism of mycobacteria inactivation was also investigated in this study. It was demonstrated that the EWNS effectively deliver the reactive oxygen species, encapsulated during the electrospray process, to the bacteria oxidizing their cell membrane resulting into inactivation. Overall, this is a method with the potential to become an effective intervention technology in the battle against airborne infections.

FROM THE CLINICAL EDITOR

This study demonstrates the feasibility of mycobacterium inactivation in airborne form or on contact surfaces using electrospray activated water nano-structures. Given that the method is free of toxic chemicals, this might become an important tool in the prevention of mycobacterial infections, which are notoriously hard to treat.

Tracking translocation of industrially relevant engineered nanomaterials (ENMs) across alveolar epithelial monolayers in vitro

Abstract Relatively little is known about the fate of industrially relevant engineered nanomaterials (ENMs) in the lungs that can be used to convert administered doses to delivered doses. Inhalation exposure and subsequent translocation of ENMs across the epithelial lining layer of the lung might contribute to clearance, toxic effects or both. To allow precise quantitation of translocation across lung epithelial cells, we developed a method for tracking industrially relevant metal oxide ENMs in vitro using neutron activation. The versatility and sensitivity of the proposed in vitro epithelial translocation (INVET) system was demonstrated using a variety of industry relevant ENMs including CeO2 of various primary particle diameter, ZnO, and SiO2-coated CeO2 and ZnO particles. ENMs were neutron activated, forming gamma emitting isotopes (141)Ce and (65)Zn, respectively. Calu-3 lung epithelial cells cultured to confluency on transwell inserts were exposed to neutron-activated ENM dispersions at sub-lethal doses to investigate the link between ENM properties and translocation potential. The effects of ENM exposure on monolayer integrity was monitored by various methods. ENM translocation across the cellular monolayer was assessed by gamma spectrometry following 2, 4 and 24 h of exposure. Our results demonstrate that ENMs translocated in small amounts (e.g. <0.01% of the delivered dose at 24 h), predominantly via transcellular pathways without compromising monolayer integrity or disrupting tight junctions. It was also demonstrated that the delivery of particles in suspension to cells in culture is proportional to translocation, emphasizing the importance of accurate dosimetry when comparing ENM-cellular interactions for large panels of materials. The reported INVET system for tracking industrially relevant ENMs while accounting for dosimetry can be a valuable tool for investigating nano-bio interactions in the future.

A chemical free, nanotechnology-based method for airborne bacterial inactivation using engineered water nanostructures

Airborne pathogens are associated with the spread of infectious diseases and increased morbidity and mortality. Herein we present an emerging chemical free, nanotechnology-based method for airborne pathogen inactivation. This technique is based on transforming atmospheric water vapor into Engineered Water Nano-Structures (EWNS) via electrospray. The generated EWNS possess a unique set of physical, chemical, morphological and biological properties. Their average size is 25 nm and they contain reactive oxygen species (ROS) such as hydroxyl and superoxide radicals. In addition, EWNS are highly electrically charged (10 electrons per particle on average). A link between their electric charge and the reduction of their evaporation rate was illustrated resulting in an extended lifetime (over an hour) at room conditions. Furthermore, it was clearly demonstrated that the EWNS have the ability to interact with and inactivate airborne bacteria. Finally, inhaled EWNS were found to have minimal toxicological effects, as illustrated in an acute in-vivo inhalation study using a mouse model. In conclusion, this novel, chemical free, nanotechnology-based method has the potential to be used in the battle against airborne infectious diseases.

An in vivo and in vitro toxicological characterisation of realistic nanoscale CeO₂ inhalation exposures

Nanoscale CeO₂ is increasingly used for industrial and commercial applications, including catalysis, UV-shielding and as an additive in various nanocomposites. Because of its increasing potential for consumer and occupational exposures, a comprehensive toxicological characterisation of this nanomaterial is needed. Preliminary results from intratracheal instillation studies in rats point to cytotoxicity and inflammation, though these studies may not accurately use realistic nanoscale exposure profiles. By contrast, published in vitro cellular studies have reported limited toxicological outcomes for the case of nano-ceria. Here, the authors present an integrative study evaluating the toxicity of nanoscale CeO₂ both in vitro, using the A549 lung epithelial cell line, and in vivo using an intact rat model. Realistic nano-ceria exposure atmospheres were generated using the Harvard Versatile Engineered Nanomaterial Generation System (VENGES), and rats were exposed via inhalation. Finally, the use of a nanothin amorphous SiO₂ encapsulation coating as a means of mitigating CeO₂ toxicity was assessed. Results from the inhalation experiments show lung injury and inflammation with increased PMN and LDH levels in the bronchoalveolar lavage fluid of the CeO₂-exposed rats. Moreover, exposure to SiO₂-coated CeO₂ did not induce any pulmonary toxicity to the animals, representing clear evidence for the safe by design SiO₂-encapsualtion concept.

Superparamagnetic iron oxide nanoparticles (SPIONs)-loaded Trojan microparticles for targeted aerosol delivery to the lung

Targeted aerosol delivery to specific regions of the lung may improve therapeutic efficiency and minimise unwanted side effects. Targeted delivery could potentially be achieved with porous microparticles loaded with superparamagnetic iron oxide nanoparticles (SPIONs)-in combination with a target-directed magnetic gradient field. The aim of this study was to formulate and evaluate the aerodynamic properties of SPIONs-loaded Trojan microparticles after delivery from a dry powder inhaler. Microparticles made of SPIONs, PEG and hydroxypropyl-β-cyclodextrin (HPβCD) were formulated by spray drying and characterised by various physicochemical methods. Aerodynamic properties were evaluated using a next generation cascade impactor (NGI), with or without a magnet positioned at stage 2. Mixing appropriate proportions of SPIONs, PEG and HPβCD allowed Trojan microparticle to be formulated. These particles had a median geometric diameter of 2.8±0.3μm and were shown to be sensitive to the magnetic field induced by a magnet having a maximum energy product of 413.8kJ/m(3). However, these particles, characterised by a mass median aerodynamic diameter (MMAD) of 10.2±2.0μm, were considered to be not inhalable. The poor aerodynamic properties resulted from aggregation of the particles. The addition of (NH4)2CO3 and magnesium stearate (MgST) to the formulation improved the aerodynamic properties of the Trojan particles and resulted in a MMAD of 2.2±0.8μm. In the presence of a magnetic field on stage 2 of the NGI, the amount of particles deposited at this stage increased 4-fold from 4.8±0.7% to 19.5±3.3%. These Trojan particles appeared highly sensitive to the magnetic field and their deposition on most of the stages of the NGI was changed in the presence compared to the absence of the magnet. If loaded with a pharmaceutical active ingredient, these particles may be useful for treating localised lung disease such as cancer nodules or bacterial infectious foci.

Nanoparticle-nanoparticle interactions in biological media by atomic force microscopy

Particle-particle interactions in physiological media are important determinants for nanoparticle fate and transport. Herein, such interactions are assessed by a novel atomic force microscopy (AFM)-based platform. Industry-relevant CeO2, Fe2O3, and SiO2 nanoparticles of various diameters were made by the flame spray pyrolysis (FSP)-based Harvard Versatile Engineering Nanomaterials Generation System (Harvard VENGES). The nanoparticles were fully characterized structurally and morphologically, and their properties in water and biological media were also assessed. The nanoparticles were attached on AFM tips and deposited on Si substrates to measure particle-particle interactions. The corresponding force was measured in air, water, and biological media that are widely used in toxicological studies. The presented AFM-based approach can be used to assess the agglomeration potential of nanoparticles in physiological fluids. The agglomeration potential of CeO2 nanoparticles in water and RPMI 1640 (Roswell Park Memorial Institute formulation 1640) was inversely proportional to their primary particle (PP) diameter, but for Fe2O3 nanoparticles, that potential is independent of PP diameter in these media. Moreover, in RPMI+10% Fetal Bovine Serum (FBS), the corona thickness and dispersibility of the CeO2 are independent of PP diameter, while for Fe2O3, the corona thickness and dispersibility were inversely proportional to PP diameter. The present method can be combined with dynamic light scattering (DLS), proteomics, and computer simulations to understand the nanobio interactions, with emphasis on the agglomeration potential of nanoparticles and their transport in physiological media.

Human inhalation exposure to iron oxide particles

In the past decade, many studies have been conducted to determine the health effects induced by exposure to engineered nanomaterials (NMs). Specifically for exposure via inhalation, numerous in vitro and animal in vivo inhalation toxicity studies on several types of NMs have been published. However, these results are not easily extrapolated to judge the effects of inhaling NMs in humans, and few published studies on the human response to inhalation of NMs exist. Given the emergence of more industries utilizing iron oxide nanoparticles as well as more nanomedicine applications of superparamagnetic iron oxide nanoparticles (SPIONs), this review presents an overview of the inhalation studies that have been conducted in humans on iron oxides. Both occupational exposure studies on complex iron oxide dusts and fumes, as well as human clinical studies on aerosolized, micron-size iron oxide particles are discussed. Iron oxide particles have not been described to elicit acute inhalation response nor promote lung disease after chronic exposure. The few human clinical studies comparing inhalation of fine and ultrafine metal oxide particles report no acute changes in the health parameters measured. Taken together existing evidence suggests that controlled human exposure to iron oxide nanoparticles, such as SPIONs, could be conducted safely.

Effects of copy center particles on the lungs: a toxicological characterization using a Balb/c mouse model

CONTEXT

Printers and photocopiers release respirable particles into the air. Engineered nanomaterials (ENMs) have been recently incorporated into toner formulations but their potential toxicological effects have not been well studied.

OBJECTIVE

To evaluate the biological responses to copier-emitted particles in the lungs using a mouse model.

METHODS

Particulate matter (PM) from a university copy center was sampled and fractionated into three distinct sizes, two of which (PM0.1 and PM0.1-2.5) were evaluated in this study. The particles were extracted and dispersed in deionized water and RPMI/10% FBS. Hydrodynamic diameter and zeta potential were evaluated by dynamic light scattering. The toxicological potential of these particles was studied using 8-week-old male Balb/c mice. Mice were intratracheally instilled with 0.2, 0.6, 2.0 mg/kg bw of either the PM0.1 and PM0.1-2.5 size fractions. Fe2O3 and welding fumes were used as comparative materials, while RPMI/10% FBS was used as the vehicle control. Bronchoalveolar lavage (BAL) was performed 24 hours post-instillation. The BAL fluid was analyzed for total and differential cell counts, and biochemical markers of injury and inflammation.

RESULTS

Particle size- and dose-dependent pulmonary effects were found. Specifically, mice instilled with PM0.1 (2.0 mg/kg bw) had significant increases in neutrophil number, lactate dehydrogenase and albumin compared to vehicle control. Likewise, pro-inflammatory cytokines were elevated in mice exposed to PM0.1 (2.0 mg/kg bw) compared to other groups.

CONCLUSION

Our results indicate that exposure to copier-emitted nanoparticles may induce lung injury and inflammation. Further exposure assessment and toxicological investigations are necessary to address this emerging environmental health pollutant.

A Safer Formulation Concept for Flame-Generated Engineered Nanomaterials

The likely success or failure of the nanotechnology industry depends on the environmental health and safety of engineered nanomaterials (ENMs). While efforts toward engineering safer ENMs are sparse, such efforts are considered crucial to the sustainability of the nanotech industry. A promising approach in this regard is to coat potentially toxic nanomaterials with a biologically inert layer of amorphous SiO₂. Core-shell particles exhibit the surface properties of their amorphous SiO₂ shell while maintaining specific functional properties of their core material. A major challenge in the development of functional core-shell particles is the design of scalable high-yield processes that can meet large-scale industrial demand. Here, we present a safer formulation concept for flame-generated ENMs based on a one-step, in flight SiO₂ encapsulation process, which was recently introduced by the authors as a means for a scalable manufacturing of SiO₂ coated ENMs. Firstly, the versatility of the SiO₂-coating process is demonstrated by applying it to four ENMs (CeO_2, ZnO, Fe₂O₃, Ag) marked by their prevalence in consumer products as well as their range in toxicity. The ENM-dependent coating fundamentals are assessed and process parameters are optimized for each ENM investigated. The effects of the SiO₂-coating on core material structure, composition and morphology, as well as the coating efficiency on each nanostructured material, are evaluated using state-of-the-art analytical methods (XRD, N₂ adsorption, TEM, XPS, isopropanol chemisorption). Finally, the biological interactions of SiO₂-coated vs. uncoated ENMs are evaluated using cellular bioassays, providing valuable evidence for reduced toxicity for the SiO₂-coated ENMs. Results indicate that the proposed 'safer by design' concept bears great promise for scaled-up application in industry in order to reduce the toxicological profile of ENMs for certain applications.

Novel lanthanide-labeled metal oxide nanoparticles improve the measurement of in vivo clearance and translocation

The deposition, clearance and translocation of europium-doped gadolinium oxide nanoparticles in a mouse lung were investigated experimentally. Nanoparticles were synthesized by spray flame pyrolysis. The particle size, crystallinity and surface properties were characterized. Following instillation, the concentrations of particles in organs were determined with inductively coupled plasma mass spectrometry. The protein corona coating the nanoparticles was found to be similar to the coating on more environmentally relevant nanoparticles such as iron oxide. Measurements of the solubility of the nanoparticles in surrogates of biological fluids indicated very little propensity for dissolution, and the elemental ratio of particle constituents did not change, adding further support to the contention that intact nanoparticles were measured. The particles were intratracheally instilled into the mouse lung. After 24 hours, the target organs were harvested, acid digested and the nanoparticle mass in each organ was measured by inductively coupled plasma mass spectrometry (ICP-MS). The nanoparticles were detected in all the studied organs at low ppb levels; 59% of the particles remained in the lung. A significant amount of particles was also detected in the feces, suggesting fast clearance mechanisms. The nanoparticle system used in this work is highly suitable for quantitatively determining deposition, transport and clearance of nanoparticles from the lung, providing a quantified measure of delivered dose.

Novel lanthanide-labeled metal oxide nanoparticles improve the measurement of in vivo clearance and translocation

The deposition, clearance and translocation of europium-doped gadolinium oxide nanoparticles in a mouse lung were investigated experimentally. Nanoparticles were synthesized by spray flame pyrolysis. The particle size, crystallinity and surface properties were characterized. Following instillation, the concentrations of particles in organs were determined with inductively coupled plasma mass spectrometry. The protein corona coating the nanoparticles was found to be similar to the coating on more environmentally relevant nanoparticles such as iron oxide. Measurements of the solubility of the nanoparticles in surrogates of biological fluids indicated very little propensity for dissolution, and the elemental ratio of particle constituents did not change, adding further support to the contention that intact nanoparticles were measured. The particles were intratracheally instilled into the mouse lung. After 24 hours, the target organs were harvested, acid digested and the nanoparticle mass in each organ was measured by inductively coupled plasma mass spectrometry (ICP-MS). The nanoparticles were detected in all the studied organs at low ppb levels; 59% of the particles remained in the lung. A significant amount of particles was also detected in the feces, suggesting fast clearance mechanisms. The nanoparticle system used in this work is highly suitable for quantitatively determining deposition, transport and clearance of nanoparticles from the lung, providing a quantified measure of delivered dose.

Evaluation of environmental filtration control of engineered nanoparticles using the Harvard Versatile Engineered Nanomaterial Generation System (VENGES)

Applying engineering controls to airborne engineered nanoparticles (ENPs) is critical to prevent environmental releases and worker exposure. This study evaluated the effectiveness of two air sampling and six air cleaning fabric filters at collecting ENPs using industrially relevant flame-made engineered nanoparticles generated using a versatile engineered nanomaterial generation system (VENGES), recently designed and constructed at Harvard University. VENGES has the ability to generate metal and metal oxide exposure atmospheres while controlling important particle properties such as primary particle size, aerosol size distribution, and agglomeration state. For this study, amorphous SiO(2) ENPs with a 15.4 nm primary particle size were generated and diluted with HEPA-filtered air. The aerosol was passed through the filter samples at two different filtration face velocities (2.3 and 3.5 m/min). Particle concentrations as a function of particle size were measured upstream and downstream of the filters using a specially designed filter test system to evaluate filtration efficiency. Real time instruments (FMPS and APS) were used to measure particle concentration for diameters from 5 to 20,000 nm. Membrane-coated fabric filters were found to have enhanced nanoparticle collection efficiency by 20-46 % points compared to non-coated fabric and could provide collection efficiency above 95 %.

Interactions of engineered nanomaterials in physiological media and implications for in vitro dosimetry

In vitro toxicity assays are efficient and inexpensive tools for screening the increasing number of engineered nanomaterials (ENMs) entering the consumer market. However, the data produced by in vitro studies often vary substantially among different studies and from in vivo data. In part, these discrepancies may be attributable to lack of standardisation in dispersion protocols and inadequate characterisation of particle-media interactions which may affect the particle kinetics and the dose delivered to cells. In this study, a novel approach for preparation of monodisperse, stabilised liquid suspensions is presented and coupled with a numerical model which estimates delivered dose values. Empirically derived material- and media-specific functions are presented for each media-ENM system that can be used to convert administered doses to delivered doses. The interactions of ENMs with a variety of physiologic media were investigated and the importance of this approach was demonstrated by in vitro cytotoxicity assays using THP-1 macrophages.