Toxicity of binary mixtures of Al2O3 and ZnO nanoparticles toward fibroblast and bronchial epithelium cells

ABSTRACT

The objective of this study was to examine the cytotoxic effects of binary mixtures of Al₂O₃ and ZnO NPs using mouse fibroblast cells (L929) and human bronchial epithelial cells (BEAS-2B) as biological test systems. The synergistic, additive, or antagonistic behavior of the binary mixture was also investigated. In toxicity experiments, cellular morphology, mitochondrial function (MTT assay), apoptosis, nuclear size and shape, clonogenic assays, and damage based upon oxidative stress parameters were assessed under control and NPs exposure conditions. Although Abbott modeling results provided no clear evidence of the binary mixture of Al₂O₃ and ZnO NPs exhibiting synergistic toxicity, some specific assays such as apoptosis, nuclear size and shape, clonogenic assay, activities of antioxidant enzymatic enzymes catalase, superoxide dismutase, and levels of glutathione resulted in enhanced toxicity for the mixtures with 1 and 1.75 toxic units (TU) toward both cell types. Data demonstrated that co-presence of Al₂O₃ and ZnO NPs in the same environment might lead to more realistic environmental conditions. Our findings indicate cytotoxicity of binary mixtures of Al₂O₃ and ZnO NPs produced greater effects compared to toxicity of either individual compound.     

Acute exposure to ZnO nanoparticles induces autophagic immune cell death

Abstract

The increasing risk of incidental exposure to nanomaterials has led to mounting concerns regarding nanotoxicity. Zinc oxide nanoparticles (ZnO NPs) are produced in large quantities and have come under scrutiny due to their capacity to cause cytotoxicity in vitro and potential to cause harm in vivo. Recent evidence has indicated that ZnO NPs promote autophagy in cells; however, the signaling pathways and the role of ion release inducing toxicity remain unclear. In this study, we report that ZnO NPs are immunotoxic to primary and immortalized immune cells. Importantly, such immunotoxicity is observed in mice in vivo, since death of splenocytes is seen after intranasal exposure to ZnO NPs. We determined that ZnO NPs release free Zn²⁺ that can be taken up by immune cells, resulting in cell death. Inhibiting free Zn²⁺ ions in solution with EDTA or their uptake with CaCl₂ abrogates ZnO NP-induced cell death. ZnO NP-mediated immune cell death was associated with increased levels of intracellular reactive oxygen species (ROS). ZnO NP death was not due to apoptosis, necroptosis or pyroptosis. Exposure of immune cells to ZnO NPs resulted in autophagic death and increased levels of LC3A, an essential component of autophagic vacuoles. Accordingly, ZnO NP-mediated upregulation of LC3A and induction of immune cell death were inhibited by blocking autophagy and ROS production. We conclude that release of Zn²⁺ from ZnO NPs triggers the production of excessive intracellular ROS, resulting in autophagic death of immune cells. Our findings suggest that exposure to ZnO NPs has the potential to impact host immunity.     

Evaluation of newly developed nose-only inhalation exposure chamber for nanoparticles

In this study, a direct-flow-type nose-only exposure chamber developed for inhalation toxicity experiments using a numerical analysis and experiments is evaluated. Maintaining a uniform flow rate and test article concentration are the critical factors when designing an inhalation exposure chamber. Therefore, this study evaluated whether the flow rate and particle size distribution at the injection nozzles at each port could be maintained with a deviation below 10%. To achieve this requirement, a nose-only exposure chamber flow field was simulated using a numerical analysis method, i.e. computational fluid dynamics (CFD) code FLUENT 6.3.26. Based on the simulation results, a test chamber was built and tested. The flow velocity was measured at the injection nozzle of the chamber and the aerosol particle size distribution was also measured at each port while inserting the test material into the exposure chamber. The results indicated that a uniform flow field distribution at each stage and port, the deviation of the flow velocity, and particle size distribution were all within 10%. Thus, the resulting nose-only exposure chamber could be described as well-designed.     

Inflammatory response of mice following inhalation exposure to iron and copper nanoparticles

We examined pulmonary inflammatory responses of mice following whole-body inhalation exposure to copper and iron nanoparticles in acute and sub-acute studies. Concentrations for sub-acute copper and iron exposures were 3.6 mg m^?3. No significant pathology was found following acute exposure. Immediately following sub-acute exposure, both iron- and copper-exposed mice showed increased inflammation compared to sentinels. Copper nanoparticle-exposed mice had significantly higher lavage cytokines as well as perivasculitis and alveolitis. Three weeks post-exposure, all inflammatory markers decreased for iron nanoparticle-exposed mice, however, some remained elevated for copper-exposed mice. At biologically relevant pHs, in vitro studies showed that copper nanoparticles displayed a greater propensity for dissolution compared to iron. We conclude that the presence of dissolved ions, the concomitant formation of smaller nanoparticles and the absence of particles in stained lung sections immediately postexposure (inferring either translocation or more dispersed aerosol distribution) contributed to the increased inflammation observed in copper nanoparticle-exposed mice.     

Cardiopulmonary response to inhalation of secondary organic aerosol derived from gas-phase oxidation of toluene

The biological response to inhalation of secondary organic aerosol (SOA) was determined in rodents exposed to SOA derived from the oxidation of toluene, a precursor emitted from anthropogenic sources. SOA atmospheres were produced to yield 300 µg·m^?3 of particulate matter (PM) plus accompanying gases. Whole-body exposures were conducted in mice to assess both pulmonary and cardiovascular effects. ApoE^?/? mice were exposed for 7 days and measurements of TBARS and gene expression of heme-oxygenase-1 (HO-1), endothelin-1 (ET-1), and matrix metalloproteinase-9 (MMP-9) were made in aorta. Pulmonary inflammatory responses in both species were measured by bronchoalveolar lavage fluid (BALF) cell counts. No pulmonary inflammation was observed. A mild response was observed in mouse aorta for the upregulation of ET-1 and HO-1, with a trend for increased MMP-9 and TBARS, and. Overall, toluene-derived SOA revealed limited biological response compared with previous studies using this exposure protocol with other environmental pollutants.     

NMR-based metabolomics to determine acute inhalation effects of nano- and fine-sized ZnO particles in the rat lung

Zinc oxide (ZnO) particles induce acute occupational inhalation illness in humans and rats. However, the possible molecular mechanisms of ZnO particles on the respiratory system remain unclear. In this study, metabolic responses of the respiratory system of rats inhaled ZnO particles were investigated by a nuclear magnetic resonance (NMR)-based metabolomic approach. Male Sprague–Dawley rats were treated with a series of doses of nano-sized (35?nm) or fine-sized (250?nm) ZnO particles. The corresponding control groups inhaled filtered air. After 24?h, bronchoalveolar lavage fluid (BALF) and lung tissues were collected, extracted and prepared for ¹H and J-resolved NMR analysis, followed by principal component analysis (PCA) and partial least squares discriminant analysis (PLS-DA). PCA and PLSDA models from analysis of BALF and hydrophilic lung NMR spectra demonstrated that dose response trends were restricted to the 250?nm ZnO particle exposure group and were not observed in the 35?nm ZnO particle exposure group. Increased isoleucine and valine, as well as decreased acetate, trimethylamine n-oxide, taurine, glycine, formate, ascorbate and glycerophosphocholine, were recorded in the BALF of rats treated with moderate and high dose 250?nm ZnO exposures. Decreases in taurine and glucose, as well as an increase of phosphorylcholine-containing lipids and fatty acyl chains, were detected in the lung tissues from 250?nm ZnO-treated rats. These metabolic changes may be associated with cell anti-oxidation, energy metabolism, DNA damage and membrane stability. We also concluded that a metabolic approach provides more complete measurements and suggests potential molecular mechanisms of adverse effects.     

Complete transformation of ZnO and CuO nanoparticles in culture medium and lymphocyte cells during toxicity testing

Here, we present evidence on complete transformation of ZnO and CuO nanoparticles, which are among the most heavily studied metal oxide particles, during 24?h in vitro toxicological testing with human T-lymphocytes. Synchrotron radiation-based X-ray absorption near edge structure (XANES) spectroscopy results revealed that Zn speciation profiles of 30?nm and 80?nm ZnO nanoparticles, and ZnSO₄- exposed cells were almost identical with the prevailing species being Zn-cysteine. This suggests that ZnO nanoparticles are rapidly transformed during a standard in vitro toxicological assay, and are sequestered intracellularly, analogously to soluble Zn. Complete transformation of ZnO in the test conditions was further supported by almost identical Zn spectra in medium to which ZnO nanoparticles or ZnSO₄ was added. Likewise, Cu XANES spectra for CuO and CuSO₄-exposed cells and cell culture media were similar. These results together with our observation on similar toxicological profiles of ZnO and soluble Zn, and CuO and soluble Cu, underline the importance of dissolution and subsequent transformation of ZnO and CuO nanoparticles during toxicological testing and provide evidence that the nano-specific effect of ZnO and CuO nanoparticles is negligible in this system. We strongly suggest to account for this aspect when interpreting the toxicological results of ZnO and CuO nanoparticles.     

纳米氧化锌对人正常肝细胞DNA及染色体的损伤作用

目的探讨纳米氧化锌对人正常肝细胞HL7702的细胞毒性和遗传毒性作用。方法纳米氧化锌10,25,50,75和100 mg.L-1培养HL7702细胞12,24和48 h。MTT法检测进行毒性评级(RGR)。单细胞凝胶电泳测定细胞头部DNA百分率、尾部DNA百分率、尾矩和Olive尾矩;微核试验测定微核率。结果纳米氧化锌对HL7702肝细胞的半数抑制浓度(IC50)为29.81 mg.L-1。纳米氧化锌10,25,50,75和100 mg.L-1作用细胞24 h,RGR分别为(96±3)%,(83±3)%,(52±4)%,(41±3)%和(21±2)%,毒性级别从1级升到4级。与正常对照组相比,纳米氧化锌10,25,50,75和100 mg.L-1组细胞DNA均有不同程度损伤,HL7702细胞的尾矩和Olive尾矩均呈逐渐显著升高趋势,头部DNA百分率降低,尾部DNA百分率增加。微核试验结果显示,12 h时纳米氧化锌≥50 mg.L-1微核率显著升高,24 h时,纳米氧化锌≥25 mg.L-1微核率显著升高;48 h时,纳米氧化锌10,25,50,75和100 mg.L-1微核率分别升高到8.3%,9.2%,17.3%和21.7%(P<0.05)。结论纳米氧化锌对HL7702肝细胞具有细胞毒性和遗传毒性。     

Developmental toxic effects of ethylbenzene or toluene alone and in combination with butyl acetate in rats after inhalation exposure

First, the developmental toxic potential of n-butyl acetate (BA) was examined in Sprague-Dawley rats following whole body inhalation exposure, 6 h day(-1), from day 6 to 20 of gestation, at concentrations of 0, 500, 1000, 2000 and 3000 ppm. Maternal toxicity was evidenced by significant decreases in body weight gain at 2000 and 3000 ppm, and by reduced food consumption at 1000 ppm and higher concentrations. The effects on prenatal development were limited to a significant decrease in fetal weight at 3000 ppm. Thus, inhaled BA was not a selective developmental toxicant. In the second part of this study, the developmental toxic effects of simultaneous exposures to ethylbenzene (EB) and BA, or to toluene (TOL) and BA were evaluated. Pregnant rats were administered EB (0, 250 or 1000 ppm) and BA (0, 500 or 1500 ppm), or TOL (0, 500 or 1500 ppm) and BA (0, 500, 1500 ppm), separately and in combinations, using a 2 x 2 factorial design. The maternal weight gain was reduced after exposure to 1000 ppm EB, to 1500 ppm BA, or to 1500 ppm TOL, either alone or in binary combinations. A significant reduction of fetal weight was associated with exposure to 1000 ppm EB alone, to either mixtures of EB with BA, or to 1500 ppm TOL alone or combined with BA at either concentration. No embryolethal or teratogenic effects were observed whatever the exposure. There was no evidence of interaction between EB and BA or between TOL and BA in causing maternal or developmental effects.     

Applications of green synthesized Ag,ZnO and Ag/ZnO nanoparticles for making clinical antimicrobial wound-healing bandages

An expeditious, environmentally-friendly and affordable synthesis of silver (Ag) and zinc oxide (ZnO) nanoparticles was attained using Prosophis fracta and coffee; ensuing Ag and ZnO nanoparticles were physicochemically characterized by UV–visible spectroscopic, X-ray diffraction, and scanning electron microscopy. The green synthesized Ag and ZnO nanoparticles comprise of an average size of about 16 and 26 nm, respectively. The minimum inhibitory concentrations (MIC) of these Ag and ZnO nanoparticles and mixture thereof, Ag/ZnO, were determined on Acinetobacter baumannii and Pseudomonas aeruginosa cultures. Cotton wound bandages were impregnated with nanoparticles of Ag and ZnO and mixed Ag/ZnO nanoparticles in the neighborhood of calculated MIC and their antimicrobial activity was studied in vitro; both types of nanoparticles showed a high antibacterial activity of bandages. Antimicrobial effect of bandages impregnated with liquid solution of Ag nanoparticles was more than that observed for ZnO and mixed Ag/ZnO nanoparticles; however, this difference was not very significant. These antibacterial bandages can potentially be used for treating and covering infection-sensitive wounds namely diabetic or burns wounds.     

Acute toxicity of zinc oxide nanoparticles to the rat olfactory system after intranasal instillation

With the increased applications of zinc oxide (ZnO) nanoparticles (NPs), the toxicity of ZnO NPs arouses great concerns from the nano community and the general public. In this study, we report the toxicity of ZnO NPs (30 nm) to the rat olfactory system after intranasal instillation revealed by non‐invasive magnetic resonance imaging (MRI). MRI scans were performed on a 4.7‐T scanner at 1, 2, 3 and 7 days post‐exposure, and the histological changes of the rat olfactory epithelium were evaluated. The influences of chemical component and dispersant of the NPs were also investigated. In addition, an olfactory behavior test was performed. The MRI and histological results indicated that ZnO NPs induced significant damages to the olfactory epithelium, including disruption of the olfactory epithelial structures and inflammation. The destruction of mitochondria in epithelial cells was observed under transmission electron microscopy (TEM), suggesting that the possible toxicological mechanism might involve cellular energy metabolic dysfunction. Further, the lesion of the olfactory epithelium disturbed sniffing behaviors of the treated animals. The results suggest that MRI is potentially useful as a screening tool to assess the consequence of occupational exposure of ZnO NPs. Caution should therefore be taken during the use and disposal of ZnO NPs to prevent the unintended public health impacts. Copyright © 2012 John Wiley & Sons, Ltd.     

Silica nanoparticles and lead acetate co-exposure triggered synergistic cytotoxicity in A549 cells through potentiation of mitochondria-dependent apoptosis induction

The adverse effects of PM2.5 are the results of combined toxicities of finer particles and their adsorbed toxic pollutants. Nevertheless, the combined toxicity of finer particles and air pollutants still remains unclear. The present study was therefore undertaken to investigate the combined cytotoxicity of silica nanoparticles (nano-SiO₂, a typical atmospheric ultrafine particle) and lead acetate (Pb, a representative air pollutant) in A549 cells focusing on mitochondria-dependent apoptosis induction. The results showed that Pb exposure alone induced mitochondria-dependent apoptosis in A549 cells, as evidenced by increased apoptotic rate and Bax/Bcl-2 ratio, up-regulated caspases 3 and 9 expressions as well as decreased mitochondrial membrane potential. Non-cytotoxic concentration of nano-SiO₂ exposure alone did not trigger apoptosis in A549 cells, but potentialized the apoptotic changes when co-exposure with Pb. Factorial analyses revealed synergistic interactions were responsible for the potentiation of joint apoptotic responses.     

Biodistribution and toxicity of spherical aluminum oxide nanoparticles

With the rapid development of the nano‐industry, concerns about their potential adverse health effects have been raised. Thus, ranking accurately their toxicity and prioritizing for in vivo testing through in vitro toxicity test is needed. In this study, we used three types of synthesized aluminum oxide nanoparticles (AlONPs): γ‐aluminum oxide hydroxide nanoparticles (γ‐AlOHNPs), γ‐ and α‐AlONPs. All three AlONPs were spherical, and the surface area was the greatest for γ‐AlONPs, followed by the α‐AlONPs and γ‐AlOHNPs. In mice, γ‐AlOHNPs accumulated the most 24 h after a single oral dose. Additionally, the decreased number of white blood cells (WBC), the increased ratio of neutrophils and the enhanced secretion of interleukin (IL)‐8 were observed in the blood of mice dosed with γ‐AlOHNPs (10 mg kg^?1). We also compared their toxicity using four different in vitro test methods using six cell lines, which were derived from their potential target organs, BEAS‐2B (lung), Chang (liver), HACAT (skin), H9C2 (heart), T98G (brain) and HEK‐293 (kidney). The results showed γ‐AlOHNPs induced the greatest toxicity. Moreover, separation of particles was observed in a transmission electron microscope (TEM) image of cells treated with γ‐AlOHNPs, but not γ‐AlONPs or α‐AlONPs. In conclusion, our results suggest that the accumulation and toxicity of AlONPs are stronger in γ‐AlOHNPs compared with γ‐AlONPs and α‐AlONPs owing their low stability within biological system, and the presence of hydroxyl group may be an important factor in determining the distribution and toxicity of spherical AlONPs. Copyright © 2015 John Wiley & Sons, Ltd.     

Hematological abnormalities of acute exposure to hexachloroethane smoke inhalation

There has been no human epidemiological data regarding potential hematological effects of hexachloroethane–zinc oxide (HC/ZnO) inhalation. This is the first epidemiological study to investigate whether HC/ZnO inhalation exposure can induce hematological abnormalities in exposed soldiers. Twenty soldiers, who were exposed to a high concentration of HC/ZnO smoke for 3–10?min in a narrow tunnel (0.6 m in width) during military training, were recruited as the exposed group (n?=?20). Another 64 soldiers, who were not visiting the explosion areas, were recruited as controls. Venous blood was collected from all participants for analyses of hematological parameters. After adjustment for potential confounders, there were significant differences in weekly mean hemoglobin (HB), red blood cell count (RBC), and hematocrit (HCT) between exposed soldiers and controls (p?<?.01) at the first follow-up through the first 4 weeks following exposure. In addition, mean white blood cell count (WBC) of exposed soldiers was significantly higher than that of controls at the 4-week follow-up. Further analysis showed HB, RBC, and HCT changes during the 1st week after exposure and reach lowest levels during the 2nd week. HB, RBC, HCT, and WBC returned to normal within 11 weeks after the HC/ZnO smoke exposure. All other hematological parameters remained unchanged at 72 weeks after the event. The authors concluded that inhalation of HC/ZnO smoke can induce acute, temporally related hematological abnormalities.     

Pulmonary toxicity and global gene expression changes in response to sub-chronic inhalation exposure to crystalline silica in rats

Exposure to crystalline silica results in serious adverse health effects, most notably, silicosis. An understanding of the mechanism(s) underlying silica-induced pulmonary toxicity is critical for the intervention and/or prevention of its adverse health effects. Rats were exposed by inhalation to crystalline silica at a concentration of 15 mg/m³, 6 hr/day, 5 days/week for 3, 6 or 12 weeks. Pulmonary toxicity and global gene expression profiles were determined in lungs at the end of each exposure period. Crystalline silica was visible in lungs of rats especially in the 12-week group. Pulmonary toxicity, as evidenced by an increase in lactate dehydrogenase (LDH) activity and albumin content and accumulation of macrophages and neutrophils in the bronchoalveolar lavage (BAL), was seen in animals depending upon silica exposure duration. The most severe histological changes, noted in the 12-week exposure group, consisted of chronic active inflammation, type II pneumocyte hyperplasia, and fibrosis. Microarray analysis of lung gene expression profiles detected significant differential expression of 38, 77, and 99 genes in rats exposed to silica for 3-, 6-, or 12-weeks, respectively, compared to time-matched controls. Among the significantly differentially expressed genes (SDEG), 32 genes were common in all exposure groups. Bioinformatics analysis of the SDEG identified enrichment of functions, networks and canonical pathways related to inflammation, cancer, oxidative stress, fibrosis, and tissue remodeling in response to silica exposure. Collectively, these results provided insights into the molecular mechanisms underlying pulmonary toxicity following sub-chronic inhalation exposure to crystalline silica in rats.     

LC-MS-based lipidomics to examine acute rat pulmonary responses after nano- and fine-sized ZnO particle inhalation exposure

Zinc oxide (ZnO) nano- and fine-sized particles are associated with respiratory toxicity in humans, but the underlying molecular mechanisms remain unclear. Our previous nuclear magnetic resonance-based metabolomic study demonstrated that changes in phosphorylcholine-containing lipids (PC-CLs) in the respiratory system were associated with ZnO particle-induced respiratory toxicity. However, the details of the lipid species associated with adverse effects and possible biomarker signatures have not been identified. Thus, a liquid chromatography-mass spectrometry (LC-MS)-based lipidomics platform was applied to examine the alterations of PC-CL species in the lungs of rats treated with a series of concentrations of nano-sized (35?nm) or fine-sized (250?nm) ZnO particles via inhalation. Principal component analysis (PCA), partial least squares discriminant analysis (PLS-DA), and the Mann–Whitney U (MWU) test with false discovery rate (FDR) control were conducted to explore the perturbed lipid species and to discriminate a potential pulmonary biomarker signature after ZnO particle exposure. The PCA and PLS-DA models revealed that the fine-sized ZnO particle-treated groups and the high-concentration nano-sized group were separated from the control groups as well as from the low and moderate nano-sized groups. The results from the MWU test further suggested that after FDR adjustment, numerous PC-CL species were altered in the high-concentration and moderate-concentration fine-sized groups. Furthermore, our results suggested that lipids involved in anti-oxidation, membrane conformation, and cellular signal transduction were altered in response to ZnO-induced oxidative stress and inflammation. One lipid, PC(18:0/18:1), exhibited good performance (AUC?>?0.8) of discriminative ability in distinguishing ZnO particle exposure from the control. These findings not only provide a foundation for the exploration of possible ZnO particle-mediated mechanisms but also suggest a lipid biomarker for ZnO particle exposure.     

Health hazards of nanoparticles: understanding the toxicity mechanism of nanosized ZnO in cosmetic products

In recent years, nanoparticles are being used extensively in personal healthcare products such as cosmetics, sunscreens, soaps, and shampoos. Particularly, metal oxide nanoparticles are gaining competence as key industrial constituents, progressing toward a remarkable rise in their applications. Zinc oxide and titanium oxide nanoparticles are the most commonly employed metal oxide nanoparticles in sunscreens, ointments, foot care, and over the counter topical products. Dermal exposure to these metal oxides predominantly occurs through explicit use of cosmetic products and airway exposure to nanoparticle dusts is primarily mediated via occupational exposure. There is a compelling need to understand the toxicity effects of nanoparticles which can easily enter the cells and induce oxidative stress. Consequently, these products have become a direct source of pollution in the environment and thereby greatly impact our ecosystem. A complete understanding of the toxicity mechanism of nano-ZnO is intended to resolve whether and to what extent such nanoparticles may pose a threat to the environment and to human beings. In this review article, we have discussed the characteristics of metal oxide nanoparticles and its applications in the cosmetic industry. We have also highlighted about their toxicity effects and their impact on human health.     

Organ burden and pulmonary toxicity of nano-sized copper (II) oxide particles after short-term inhalation exposure

Introduction: Increased use of nanomaterials has raised concerns about the potential for undesirable human health and environmental effects. Releases into the air may occur and, therefore, the inhalation route is of specific interest. Here we tested copper oxide nanoparticles (CuO NPs) after repeated inhalation as hazard data for this material and exposure route is currently lacking for risk assessment.

Methods: Rats were exposed nose-only to a single exposure concentration and by varying the exposure time, different dose levels were obtained (C?×?T protocol). The dose is expressed as 6?h-concentration equivalents of 0, 0.6, 2.4, 3.3, 6.3, and 13.2?mg/m³ CuO NPs, with a primary particle size of 10 9.2–14?nm and an MMAD of 1.5?μm.

Results: Twenty-four hours after a 5-d exposure, dose-dependent lung inflammation and cytotoxicity were observed. Histopathological examinations indicated alveolitis, bronchiolitis, vacuolation of the respiratory epithelium, and emphysema in the lung starting at 2.4?mg/m³. After a recovery period of 22 d, limited inflammation was still observed, but only at the highest dose of 13.2?mg/m³. The olfactory epithelium in the nose degenerated 24?h after exposure to 6.3 and 13.2?mg/m³, but this was restored after 22 d. No histopathological changes were detected in the brain, olfactory bulb, spleen, kidney and liver.

Conclusion: A 5-d, 6-h/day exposure equivalent to an aerosol of agglomerated CuO NPs resulted in a dose-dependent toxicity in rats, which almost completely resolved during a 3-week post-exposure period.     

Pulmonary toxicity of inhaled nanoscale and fine zinc oxide particles: Mass and surface area as an exposure metric

The total surface area is known to be an effective exposure metric for predicting the lung toxicity of low solubility nanoparticles (NPs). However, if NPs are dissolved quickly enough in the lungs, the mass may be correlated with the toxicity. Recent studies have found that the toxicity of zinc oxide (ZnO) NPs was caused by the release of zinc ions. Thus, we hypothesized that mass could be used as an exposure metric for the toxicity of ZnO NPs. Healthy Sprague-Dawley rats were exposed to a low, moderate, or high dose of 35 and 250?nm ZnO particles or filtered air. Bronchoalveolar lavage fluid was collected to determine lung inflammation, injury and oxidative stress. The lung inflammation induced by ZnO particles according to different concentration metrics, including number, mass and surface area, was compared. The mass concentration was significantly correlated with the percentage of neutrophils (R²?=?0.84), number of neutrophils (R²?=?0.84) and total cells (R²?=?0.73). Similarly, surface area concentration was significantly correlated with the percentage of neutrophils (R²?=?0.94), number of neutrophils (R²?=?0.81) and total cells (R²?=?0.76). There was no correlation between the number and lung inflammation. We found that both mass and surface area were effective as metrics for the toxicity of ZnO NPs, although only surface area was previously indicated to be an effective metric. Our results are also consistent with recent study results that ZnO NPs and released zinc ions may play a role mediating the toxicity of NPs.     

Toxicity of copper oxide and basic copper carbonate nanoparticles after short-term oral exposure in rats

Copper oxide (CuO) nanoparticles (NPs) and copper carbonate nanoparticles (Cu₂CO₃(OH)₂ NPs have applications as antimicrobial agents and wood preservatives: an application that may lead to oral ingestion via hand to mouth transfer. Rats were exposed by oral gavage to CuO NPs and Cu₂CO₃(OH)₂ NPs for five consecutive days with doses from 1 to 512?mg/kg and 4 to 128?mg/kg per day, respectively, and toxicity was evaluated at days 6 and 26. Both CuO NPs and Cu₂CO₃(OH)₂ NPs induced changes in hematology parameters, as well as clinical chemistry markers (e.g. increased alanine aminotransferase, ALT) indicative of liver damage For CuO NPs histopathological alterations were observed in bone marrow, stomach and liver mainly consisting of an inflammatory response, ulceration, and degeneration. Cu₂CO₃(OH)₂ NPs induced morphological alterations in the stomach, liver, intestines, spleen, thymus, kidneys, and bone marrow. In spleen and thymus lymphoid, depletion was noted that warrants further immunotoxicological evaluation. The NPs showed partial dissolution in artificial simulated stomach fluids, while in intestinal conditions, the primary particles simultaneously shrank and agglomerated into large structures. This means that both copper ions and the particulate nanoforms should be considered as potential causal agents for the observed toxicity. For risk assessment, the lowest bench mark dose (BMD) was similar for both NPs for the serum liver enzyme AST (an indication of liver toxicity), being 26.2?mg/kg for CuO NPs and 30.8?mg/kg for Cu₂CO₃(OH)₂ NPs. This was surprising since the histopathology evidence demonstrates more severe organ damage for Cu₂CO₃(OH)₂ NPs than for CuO NPs.