Kinetics and dissolution of intratracheally administered nickel oxide nanomaterials in rats

A Systematic Genotoxicity Assessment of a Suite of Metal Oxide Nanoparticles Reveals Their DNA Damaging and Clastogenic Potential

Metal oxide nanoparticles (MONP/s) induce DNA damage, which is influenced by their physicochemical properties. In this study, the high-throughput CometChip and micronucleus (MicroFlow) assays were used to investigate DNA and chromosomal damage in mouse lung epithelial cells induced by nano and bulk sizes of zinc oxide, copper oxide, manganese oxide, nickel oxide, aluminum oxide, cerium oxide, titanium dioxide, and iron oxide. Ionic forms of MONPs were also included. The study evaluated the impact of solubility, surface coating, and particle size on response. Correlation analysis showed that solubility in the cell culture medium was positively associated with response in both assays, with the nano form showing the same or higher response than larger particles. A subtle reduction in DNA damage response was observed post-exposure to some surface-coated MONPs. The observed difference in genotoxicity highlighted the mechanistic differences in the MONP-induced response, possibly influenced by both particle stability and chemical composition. The results highlight that combinations of properties influence response to MONPs and that solubility alone, while playing an important role, is not enough to explain the observed toxicity. The results have implications on the potential application of read-across strategies in support of human health risk assessment of MONPs.

Toxicokinetic study of scandium oxide in rats

Canada has recently invested in the large-scale exploitation of scandium oxide. However, there are no studies available to date to understand its toxicokinetics in the animal or human body, which is necessary to assess exposure and health risks. The aim of this research was to investigate the toxicokinetics of absorbed scandium oxide (Sc2O3) using the rat as an experimental model. Male Sprague-Dawley rats were injected intravenously with 0.3 or 1 mg Sc2O3/kg body weight (bw). Blood and excreta (urine and feces) were collected sequentially during a 21-day period, and main organs (liver, spleen, lungs, kidneys, brain) were withdrawn at sacrifice on day 21. Inductively coupled plasma-mass spectrometry (ICP-MS) was used for the measurement of Sc element in the different samples. The mean residence time (MRTIV) calculated from the blood profile was 19.7 ± 5.9 h and 43.4 ± 24.6 h at the lower and higher doses, respectively. Highest tissue levels of Sc were found in the lungs and liver; respective lung values of 10.6 ± 6.2% and 3.4 ± 2.3% of the Sc dose were observed at the time of sacrifice while liver levels represented 8.9 ± 6.4% and 4.6 ± 1.1%. Elimination of Sc from the body was not complete after 21 days. Cumulative fecal excretion over the 21-day collection period represented 12.3 ± 1.3% and 5.9 ± 1.0% of the lower and higher Sc doses, respectively, and showed a significant effect of the dose on the excretion; only a small fraction of the Sc dose was recovered in urine (0.025 ± 0.016% and 0.011 ± 0.004% in total, respectively). In addition to an effect of the dose on the toxicokinetics, results highlight the importance of the lung as a site of accumulation and retention of Sc2O3, which raises the question of the risks of effects related to respiratory exposure in workers. The results also question the relevance of urine as a matrix for biological exposure monitoring. A more in-depth inhalation toxicokinetic study would be necessary.

Toxicity of Metal Oxide Nanoparticles: Looking through the Lens of Toxicogenomics

The impact of solubility on the toxicity of metal oxide nanoparticles (MONPs) requires further exploration to ascertain the impact of the dissolved and particulate species on response. In this study, FE1 mouse lung epithelial cells were exposed for 2-48 h to 4 MONPs of varying solubility: zinc oxide, nickel oxide, aluminum oxide, and titanium dioxide, in addition to microparticle analogues and metal chloride equivalents. Previously published data from FE1 cells exposed for 2-48 h to copper oxide and copper chloride were examined in the context of exposures in the present study. Viability was assessed using Trypan Blue staining and transcriptomic responses via microarray analysis. Results indicate material solubility is not the sole property governing MONP toxicity. Transcriptional signaling through the 'HIF-1α Signaling' pathway describes the response to hypoxia, which also includes genes associated with processes such as oxidative stress and unfolded protein responses and represents a conserved response across all MONPs tested. The number of differentially expressed genes (DEGs) in this pathway correlated with apical toxicity, and a panel of the top ten ranked DEGs was constructed (Hmox1, Hspa1a, Hspa1b, Mmp10, Adm, Serpine1, Slc2a1, Egln1, Rasd1, Hk2), highlighting mechanistic differences among tested MONPs. The HIF-1α pathway is proposed as a biomarker of MONP exposure and toxicity that can help prioritize MONPs for further evaluation and guide specific testing strategies.

Differential particle and ion kinetics of silver nanoparticles in the lungs and biotransformation to insoluble silver sulfide

The measurement of nanoparticles (NPs) in a biological matrix is essential in various toxicity studies. However, the current knowledge has limitations in differentiating particulate and ionic forms and further identification of their biotransformation. Herein, we evaluate the biotransformation and differential lung clearance kinetics of particulate and ionic forms using PEGylated silver NPs (AgNP-PEGs; 47.51 nm) and PEGylated gold NPs (AuNP-PEGs; 11.76 nm). At 0, 3, and 6 h and 1, 3, 7, and 14 days after a single pharyngeal aspiration in mice at 25 μg/mouse, half of the lung is digested by proteinase K (PK) to separate particulates and ions, and the other half is subjected to the acid digestion method for comparison. The quantitative and qualitative evaluation of lung clearance kinetics suggests that AgNP-PEGs are quickly dissolved and transformed into insoluble silver sulfide (Ag₂S), which shows a fast-clearing early phase (0 -6 h; particle T_1/2: 4.8 h) and slow-clearing late phase (1 -14 days; particle T_1/2: 13.20 days). In contrast, AuNP-PEGs were scarcely cleared or biotransformed in the lungs for 14 days. The lung clearance kinetics of AgNPs and biotransformation shown in this study can be informed by the PK digestion method and cannot be obtained using the acid digestion method.

A Comparative Study of the Biodurability and Persistence of Gold, Silver and Titanium Dioxide Nanoparticles Using the Continuous Flow through System

The potential for nanoparticles to cause harm to human health and the environment is correlated with their biodurability in the human body and persistence in the environment. Dissolution testing serves to predict biodurability and nanoparticle environmental persistence. In this study, dissolution testing using the continuous flow through system was used to investigate the biodurability and persistence of gold nanoparticles (AuNPs), silver nanoparticles (AgNPs) and titanium dioxide nanoparticles (TiO₂ NPs) in five different simulated biological fluids and two synthetic environmental media to predict their behaviour in real life situations. This study examined the physicochemical properties and agglomeration state of gold, silver and titanium dioxide nanoparticles before and after dissolution tests using three different techniques (UV-vis, XRD and TEM). The UV-vis spectra revealed that all three nanoparticles shifted to higher wavelengths after being exposed to simulated fluids. The titanium powder was found to be mixed with both rutile and anatase, according to XRD examination. The average diameter of gold nanoparticles was 14 nm, silver nanoparticles were 10 nm and titanium dioxide nanoparticles were 25 nm, according to TEM images. The gold and silver nanoparticles were observed to be spherical, but the titanium dioxide nanoparticles were irregular in shape, with some being spherical. The level of dissolved nanoparticles in simulated acidic media was higher in magnitude compared to that dissolved in simulated alkaline media. The results obtained via the continuous flow through dissolution system also displayed very significant dissolution rates. For TiO₂ NPs the calculated half-times were in the range of 13-14 days, followed by AuNPs ranging between 4-12 days, significantly longer if compared to the half-times of AgNPs ranging between 2-7 days. AuNPs and TiO₂ NPs were characterized by low dissolution rates therefore are expected to be (bio)durable in physiological surroundings and persistent in the environment thus, they might impose long-term effects on humans and the environment. In contrast, AgNPs have high dissolution rates and not (bio)durable and hence may cause short-term effects. The results suggest a hierarchy of biodurability and persistence of TiO₂ NPs > AuNPs > AgNPs. It is recommended that nanoparticle product developers should follow the test guidelines stipulated by the OECD to ensure product safety for use before it is taken to the market.

Time‐course analysis of pulmonary inflammation induced by intratracheal instillation of nanosized crystalline silica particles in F344 rats

Crystalline silica is an important cause of serious pulmonary diseases, and its toxic potential is known to be associated with its surface electrical properties. However, in vivo data clarifying the relevance of silica's toxic potential, especially its long-term effects, remain insufficient. To investigate the contribution of physico-chemical property including surface potential on the hazard of nanocrystalline silica, we performed single intratracheal instillation testing using five different crystalline silicas in a rat model and assessed time-course changes in pulmonary inflammation, lung burden, and thoracic lymph node loads. Silica-nanoparticles were prepared from two commercial products (Min-U-Sil5 [MS5] and SIO07PB [SPB]) using three different pretreatments: centrifugation (C), grinding (G), and surface dissolving (D). The five types of silica particles-MS5, MS5_C, SPB_C, SPB_G, and SPB_D-were intratracheally instilled into male F344 rats at doses of 0 mg/kg (purified water), 0.22 mg/kg (SPB), and 0.67, 2, or 6 mg/kg (MS5). Bronchoalveolar lavage, a lung burden analysis, and histopathological examination were performed at 3, 28, and 91 days after instillation. Granuloma formation was present in MS5 group at 91 days after instillation, although granuloma formation was suppressed in MS5_C group, which had a smaller particle size. SPB_C induced severe and progressive inflammation and kinetic lung overload, whereas SPB_G and SPB_D induced only slight and transient acute inflammation. Our results support that in vivo toxic potential of nanosilica by intratracheal instillation may involve with surface electrical properties leading to prolonged effect and may not be dependent not only on surface properties but also on other physico-chemical properties.

Dissolution of titanium dioxide nanoparticles in synthetic biological and environmental media to predict their biodurability and persistence

Investigating the biodurability and persistence of titanium dioxide nanoparticles (TiO₂ NPs) is of paramount importance because these parameters influence the particles' impact on human health and the environment. Contrary to most research conducted so far, the present study elucidates the dissolution kinetics, namely the dissolution rates, rate constants, order of reaction and half-times of TiO₂ NPs in five different simulated biological fluids and two synthetic environmental media to predict their behaviour in real life situations. Results have shown that the dissolution of TiO₂ NPs in all simulated fluids was limited. Of all the simulated biological media tested, acidic media such as phagolysosomal and gastric fluid produced the highest dissolution of TiO₂ NPs compared to alkaline media such as blood plasma, Gamble's fluid, and intestinal fluid. Furthermore, when the particles were exposed to simulated environmental conditions, the dissolution was higher in high ionic strength seawater compared to freshwater. The dissolution kinetics of titanium dioxide nanoparticles followed first order reaction kinetics and were generally characterized by low dissolution rates and long half-times. These findings indicate that TiO₂ NPs are very insoluble and will remain unchanged in the body and environment over long periods of time. Therefore, these particles are most likely to cause both short and long-term health effects and will remain persistent following release into the environment.

Dissolution Rate of Nanomaterials Determined by Ions and Particle Size under Lysosomal Conditions: Contributions to Standardization of Simulant Fluids and Analytical Methods

Dissolution of inhaled engineered nanomaterials (ENM) under physiological conditions is essential to predict the clearance of the ENM from the lungs and to assess their biodurability and the potential effects of released ions. Alveolar macrophage (AM) lysosomes contain a pH 4.5 saline brine with enzymes and other components. Different types of artificial phagolysosomal simulant fluids (PSFs) have been developed for dissolution testing, but the consequence of using different media is not known. In this study, we tested to which extent six fundamentally different PSFs affected the ENM dissolution kinetics and particle size as determined by a validated transmission electron microscopy (TEM) image analysis. Three lysosomal simulant media were consistent with each other and with in vivo clearance. These media predict the quick dissolution of ZnO, the partial dissolution of SiO2, and the very slow dissolution of TiO2. The valid media use either a mix of organic acids (with the total concentration below 0.5 g/L, thereof citric acid below 0.15 g/L) or another organic acid (KH phthalate). For several ENM, including ZnO, BaSO4, and CeO2, all these differences induce only minor modulation of the dissolution rates. Only for TiO2 and SiO2, the interaction with specific organic acids is highly sensitive, probably due to sequestration of the ions, and can lead to wrong predictions when compared to the in vivo behavior. The media that fail on TiO2 and SiO2 dissolution use citric acid at concentrations above 5 g/L (up to 28 g/L). In the present selection of ENM, fluids, and methods, the different lysosomal simulant fluids did not induce changes of particle morphology, except for small changes in SiO2 and BaSO4 particles most likely due to ion dissolution, reprecipitation, and coalescence between neighboring particles. Based on the current evidence, the particle size by TEM analysis is not a sufficiently sensitive analytical method to deduce the rate of ENM dissolution in physiological media. In summary, we recommend the standardization of ENM dissolution testing by one of the three valid lysosomal simulant fluids with determination of the dissolution rate and halftime by the quantification of ions. This recommendation was established for a continuous flow system but may be relevant as well for static (batch) solubility testing.

Exposure to Nickel Oxide Nanoparticles Induces Acute and Chronic Inflammatory Responses in Rat Lungs and Perturbs the Lung Microbiome

Nickel oxide nanoparticles (NiO NPs) are highly redox active nanoparticles. They can cause acute and chronic inflammation in rat lungs. Unlike the gut microbiome, the association between the lung microbiome's role and pulmonary inflammatory response to inhaled nanoparticles remains largely unexplored. We aimed to explore the interaction between the lung microbiome and inflammatory responses in rats exposed to NiO NPs. Thirty female Wistar rats were randomly categorized into control and low- (50 cm2/rat), and high- (150 cm2/rat) dose NiO NPs exposure groups. NiO NPs were intratracheally instilled, and cytological, biochemical, proinflammatory cytokine, and lung microbiome analyses of bronchoalveolar lavage fluid were performed at 1 day and 4 weeks after instillation. NiO NPs caused a neutrophilic and lymphocytic inflammatory response in rat lung. We demonstrated that exposure to NiO NPs can alter the lung microbial composition in rats. In particular, we found that more Burkholderiales are present in the NiO NPs exposure groups than in the control group at 1 day after instillation. Dysbiosis in the lung microbiome is thought to be associated with acute lung inflammation. We also suggested that Burkholderiales may be a key biomarker associated with lung neutrophilic inflammation after NiO NPs exposure.

Engineering surface patterns on nanoparticles: New insights on nano-bio interactions

The surface properties of nanoparticles affect their fates in biological systems. Based on nanotechnology and methodology, pioneering works have explored the effects of chemical surface patterns on the behavior of...

Oxidative metabolism in the cardiorespiratory system after an acute exposure to nickel-doped nanoparticles in mice

There is an increasing concern over the harmful effects that metallic nanoparticles (NP) may produce on human health. Due to their redox properties, nickel (Ni) and Ni-containing NP are particularly relevant. Hence, the aim of this study was to establish the toxicological mechanisms in the cardiorespiratory oxidative metabolism initiated by an acute exposure to Ni-doped-NP. Mice were intranasally instilled with silica NP containing Ni (II) (Ni-NP) (1 mg Ni (II)/kg body weight) or empty NP as control, and 1 h after exposure lung, plasma, and heart samples were obtained to assess the redox metabolism. Results showed that, NP were mainly retained in the lungs triggering a significantly increased tissue O₂ consumption rate, leading to Ni-NP-increased reactive oxygen species production by NOX activity, and mitochondrial H₂O₂ production rate. In addition, an oxidant redox status due to an altered antioxidant system showed by lung GSH/GSSG ratio decreased, and SOD activity increased, resulting in an increased phospholipid oxidation. Activation of circulating polymorphonuclear leukocytes, along with GSH/GSSG ratio decreased, and phospholipid oxidation were found in the Ni-NP-group plasma samples. Consequently, in distant organs such as heart, Ni-NP inhalation alters the tissue redox status. Our results showed that the O₂ metabolism analysis is a critical area of study following Ni-NP inhalation. Therefore, this work provides novel data linking the redox metabolisms alterations elicited by exposure to Ni (II) adsorbed to NP and cardiorespiratory toxicity.

A metabolomic-based study on disturbance of bile acids metabolism induced by intratracheal instillation of nickel oxide nanoparticles in rats

Nickel oxide nanoparticles (Nano NiO) evoke hepatotoxicity, while whether it affects the hepatic metabolism remains unclear. The aim of this study was to explore the differential metabolites and their metabolic pathways in rat serum and to further verify the potential mechanism of bile acids' (BAs) metabolism dysregulation after Nano NiO exposure. Sixteen male Wistar rats were intratracheally instilled with Nano NiO (0.24 mg/kg body weight) twice a week for 9 weeks. Liquid chromatography/mass spectrometry was applied to filter the differentially expressed metabolites in rat serum. Western blot was employed to detect the protein contents. Twenty-one differential metabolites that associated with BAs, lipid and phospholipid metabolism pathways were identified in rat serum after Nano NiO exposure. Decreased cholic acid and deoxycholic acid implied that the BAs metabolism was disturbed. The nickel content increased in liver after Nano NiO exposure. The protein expression of cholesterol 7α-hydroxylase (CYP7A1) was down-regulated, and the bile salt export pump was up-regulated after Nano NiO administration in rat liver. Moreover, dehydroepiandrosterone sulphotransferase (SULT2A1) and cytochrome P450 (CYP) 3A4 were elevated in the exposure group. In conclusion, Nano NiO might trigger the disturbances of BAs, lipid and phospholipid metabolism pathways in rats. The diminished serum BAs induced by Nano NiO might be related to the down-regulation of synthetase and to the overexpression of transmembrane protein and detoxification enzymes in BAs metabolism.

Simulated biological fluids - a systematic review of their biological relevance and use in relation to inhalation toxicology of particles and fibres

The use of simulated biological fluids (SBFs) is a promising in vitro technique to better understand the release mechanisms and possible in vivo behaviour of materials, including fibres, metal-containing particles and nanomaterials. Applications of SBFs in dissolution tests allow a measure of material biopersistence or, conversely, bioaccessibility that in turn can provide a useful inference of a materials biodistribution, its acute and long-term toxicity, as well as its pathogenicity. Given the wide range of SBFs reported in the literature, a review was conducted, with a focus on fluids used to replicate environments that may be encountered upon material inhalation, including extracellular and intracellular compartments. The review aims to identify when a fluid design can replicate realistic biological conditions, demonstrate operation validation, and/or provide robustness and reproducibility. The studies examined highlight simulated lung fluids (SLFs) that have been shown to suitably replicate physiological conditions, and identify specific components that play a pivotal role in dissolution mechanisms and biological activity; including organic molecules, redox-active species and chelating agents. Material dissolution was not always driven by pH, and likewise not only driven by SLF composition; specific materials and formulations correspond to specific dissolution mechanisms. It is recommended that SLF developments focus on biological predictivity and if not practical, on better biological mimicry, as such an approach ensures results are more likely to reflect in vivo behaviour regardless of the material under investigation.

Time dependent impact of copper oxide nanomaterials on the expression of genes associated with oxidative stress, metal binding, inflammation and mucus secretion in single and co-culture intestinal in vitro models

The potential for ingestion of copper oxide nanomaterials (CuO NMs) is increasing due to their increased exploitation. Investigation of changes in gene expression allows toxicity to be detected at an early stage of NM exposure and can enable investigation of the mechanism of toxicity. Here, undifferentiated Caco-2 cells, differentiated Caco-2 cells, Caco-2/HT29-MTX (mucus secreting) and Caco-2/Raji B (M cell model) co-cultures were exposed to CuO NMs and copper sulphate (CuSO₄) in order to determine their impacts. Cellular responses were measured in terms of production of reactive oxygen species (ROS), the gene expression of an antioxidant (haem oxygenase 1 (HMOX1)), the pro-inflammatory cytokine (interleukin 8 (IL8)), the metal binding (metallothionein 1A and 2A (MT1A and MT2A)) and the mucus secreting (mucin 2 (MUC2)), as well as HMOX-1 protein level. While CuSO₄ induced ROS production in cells, no such effect was observed for CuO NMs. However, these particles did induce an increase in the level of HMOX-1 protein and upregulation of HMOX1, MT2A, IL8 and MUC2 genes in all cell models. In conclusion, the expression of HMOX1, IL8 and MT2A were responsive to CuO NMs at 4 to 12 h post exposure when investigating the toxicity of NMs using intestinal in vitro models. These findings can inform the selection of endpoints, timepoints and models when investigating NM toxicity to the intestine in vitro in the future.

Review and Evaluation of the Potential Health Effects of Oxidic Nickel Nanoparticles

The exceptional physical and chemical properties of nickel nanomaterials have been exploited in a range of applications such as electrical conductors, batteries, and biomaterials. However, it has been suggested that these unique properties may allow for increased bioavailability, bio-reactivity, and potential adverse health effects. Thus, the purpose of this review was to critically evaluate data regarding the toxicity of oxidic nickel nanoparticles (nickel oxide (NiO) and nickel hydroxide (Ni(OH)2) nanoparticles) with respect to: (1) physico-chemistry properties; (2) nanomaterial characterization in the defined delivery media; (3) appropriateness of model system and translation to potential human effects; (4) biodistribution, retention, and clearance; (5) routes and relevance of exposure; and (6) current research data gaps and likely directions of future research. Inhalation studies were prioritized for review as this represents a potential exposure route in humans. Oxidic nickel particle size ranged from 5 to 100 nm in the 60 studies that were identified. Inflammatory responses induced by exposure of oxidic nickel nanoparticles via inhalation in rodent studies was characterized as acute in nature and only displayed chronic effects after relatively large (high concentration and long duration) exposures. Furthermore, there is no evidence, thus far, to suggest that the effects induced by oxidic nickel nanoparticles are related to preneoplastic events. There are some data to suggest that nano- and micron-sized NiO particles follow a similar dose response when normalized to surface area. However, future experiments need to be conducted to better characterize the exposure-dose-response relationship according to specific surface area and reactivity as a dose metric, which drives particle dissolution and potential biological responses.

Critical Choices in Predicting Stone Wool Biodurability: Lysosomal Fluid Compositions and Binder Effects

The hazard potential, including carcinogenicity, of inhaled man-made vitreous fibers (MMVFs) is correlated with their biodurability in the lung, as prerequisite for biopersistence. Abiotic dissolution testing serves to predict biodurability. We re-analyzed the International Agency for Research on Cancer Monograph on MMVFs and found that the correlation between in vivo biopersistence and abiotic dissolution presented therein confounded different simulant fluids and further confounded evaluation of leaching vs structural elements. These are critical choices for abiotic dissolution testing, as are binder removal and the rate of the flow that removes ions during testing. Therefore, we experimentally demonstrated how fluid composition and binder affect abiotic dissolution of a representative stone wool MMVF. We compared six simulant fluids (all pH 4.5, reflecting the environment of alveolar macrophage lysosomes) that differed in organic acids, which have a critical role in their ability to modulate the formation of Si-rich gels on the fiber surfaces. Removing the binder accelerates the average dissolution rate by +104% (max. + 273%) across the fluids by suppression of gel formation. Apart from the high-citrate fluid that predicted a 10-fold faster dissolution than is observed in vivo, none of the five other fluids resulted in dissolution rates above 400 ng/cm²/h, the limit associated with the exoneration from classification for carcinogenicity in the literature. These findings were confirmed with and without binder. For corroboration, five more stone wool MMVFs were assessed with and without binder in one specific fluid. Again, the presence of the binder caused gel formation and reduced dissolution rates. To enhance the reliability and robustness of abiotic predictions of biodurability, we recommend replacing the critically influential citric acid in pH 4.5 fluids with other organic acids. Also, future studies should consider structural transformations of the fibers, including changes in fiber length, fiber composition, and reprecipitation of gel layers.

Time-course comparison of pulmonary inflammation induced by intratracheal instillation of four different nickel oxide nanoparticles in male Fischer rats

Occupational exposure to nickel oxide (NiO) is an important cause of respiratory tract cancer. Toxicity is known to be associated with the dissociated component, i.e. nickel (II) ions. To address the relationship between physicochemical properties, including solubility in artificial lysosomal fluid, of NiO and time-course changes in the pulmonary response, we conducted an intratracheal instillation study in male Fischer rats using four different well-characterized NiO products, US3352 (NiO A), NovaWireNi01 (NiO B), I small particle (NiO C), and 637130 (NiO D). The NiOs were suspended in purified water and instilled once intratracheally into male F344 rats (12 weeks old) at 0 (vehicle control), 0.67, 2, and 6 mg/kg body weight. The animals were euthanized on days 3, 28, or 91 after instillation, and blood analysis, bronchoalveolar lavage fluid (BALF) testing, and histopathological examination were performed. The most soluble product, NiO B, caused the most severe systemic toxicity, leading to a high mortality rate, but the response was transient and surviving animals recovered. The second-most-soluble material, NiO D, and the third, NiO A, caused evident pulmonary inflammation, and the responses persisted for at least 91 days with collagen proliferation. In contrast, NiO C induced barely detectable inflammation in the BALF examination, and no marked changes were noted on histopathology. These results indicate that the early phase toxic potential of NiO products, but not the persistence of pulmonary inflammation, is associated with their solubility.

Cytotoxic, Genotoxic, and Apoptotic Effects of Nickel Oxide Nanoparticles in Intestinal Epithelial Cells

Objectives

The superior properties of nickel oxide-nanoparticles (NiO-NPs) have led to their wide use in various fields. However, there is little comprehensive knowledge about their toxicity, especially after oral exposure. The toxic effect of NiO-NPs of mean size 15.0 nm was investigated in Caco-2 (human intestinal epithelial) cells as no study has been performed on their intestinal toxicity.

Materials and Methods

Following identification of their particle size distribution and cellular uptake potential, the risk of exposure to NiO-NPs was evaluated by cellular morphologic changes, cyto- and genotoxic potentials, oxidative damage, and apoptotic induction.

Results

NiO-NPs induced a 50% reduction in cell viability at 351.6 μg/mL and caused DNA damage and oxidative damage at 30-150 μg/mL. It appears that apoptosis might be a main cell death mechanism in NiO-NP-exposed intestinal cells.

Conclusion

NiO-NPs might be hazardous to the gastrointestinal system. The results should raise concerns about using NiO-NPs in food-contact appliances and about NiO-NP-containing wastes. Further in vivo and in vitro research should be conducted to explain the specific toxicity mechanism of these particles and reduce their risk to humans.

Evaluating UiO-66 Metal-Organic Framework Nanoparticles as Acid-Sensitive Carriers for Pulmonary Drug Delivery Applications

Developing novel drug carriers for pulmonary delivery is necessary to achieve higher efficacy and consistency for treating pulmonary diseases while limiting off-target side effects that occur from alternative routes of administration. Metal-organic frameworks (MOFs) have recently emerged as a class of materials with characteristics well-suited for pulmonary drug delivery, with chemical tunability, high surface area, and pore size, which will allow for efficient loading of therapeutic cargo and deep lung penetration. UiO-66, a zirconium and terephthalic acid-based MOF, has displayed notable chemical and physical stability and potential biocompatibility; however, its feasibility for use as a pulmonary drug delivery vehicle has yet to be examined. Here, we evaluate the use of UiO-66 nanoparticles (NPs) as novel pulmonary drug delivery vehicles and assess the role of missing linker defects in their utility for this application. We determined that missing linker defects result in differences in NP aerodynamics but have minimal effects on the loading of model and therapeutic cargo, cargo release, biocompatibility, or biodistribution. This is a critical result, as it indicates the robust consistency of UiO-66, a critical feature for pulmonary drug delivery, which is plagued by inconsistent dosage because of variable properties. Not only that, but UiO-66 NPs also demonstrate pH-dependent stability, with resistance to degradation in extracellular conditions and breakdown in intracellular environments. Furthermore, the carriers exhibit high biocompatibility and low cytotoxicity in vitro and are well-tolerated in in vivo murine evaluations of orotracheally administered NPs. Following pulmonary delivery, UiO-66 NPs remain localized to the lungs before clearance over the course of seven days. Our results demonstrate the feasibility of using UiO-66 NPs as a novel platform for pulmonary drug delivery through their tunable NP properties, which allow for controlled aerodynamics and internalization-dependent cargo release while displaying remarkable pulmonary biocompatibility.

Peptide bond cleavage in the presence of Ni-containing particles

NiO nanoparticles and non-stoichiometric black NiO were shown to be effective sources of Ni2+ ions causing sequence-selective peptide bond hydrolysis. NiO nanoparticles were as effective in this reaction as their molar equivalent of soluble Ni(ii) salt. These findings highlight the efficacy of delivery of toxic Ni2+ by these environmentally available particles.

A review of hepatic nanotoxicology - summation of recent findings and considerations for the next generation of study designs

The liver is one of the most important multi-functional organs in the human body. Amongst various crucial functions, it is the main detoxification center and predominantly implicated in the clearance of xenobiotics potentially including particulates that reach this organ. It is now well established that a significant quantity of injected, ingested or inhaled nanomaterials (NMs) translocate from primary exposure sites and accumulate in liver. This review aimed to summarize and discuss the progress made in the field of hepatic nanotoxicology, and crucially highlight knowledge gaps that still exist.Key considerations include In vivo studies clearly demonstrate that low-solubility NMs predominantly accumulate in the liver macrophages the Kupffer cells (KC), rather than hepatocytes.KCs lining the liver sinusoids are the first cell type that comes in contact with NMs in vivo. Further, these macrophages govern overall inflammatory responses in a healthy liver. Therefore, interaction with of NM with KCs in vitro appears to be very important.Many acute in vivo studies demonstrated signs of toxicity induced by a variety of NMs. However, acute studies may not be that meaningful due to liver's unique and unparalleled ability to regenerate. In almost all investigations where a recovery period was included, the healthy liver was able to recover from NM challenge. This organ's ability to regenerate cannot be reproduced in vitro. However, recommendations and evidence is offered for the design of more physiologically relevant in vitro models.Models of hepatic disease enhance the NM-induced hepatotoxicity.The review offers a number of important suggestions for the future of hepatic nanotoxicology study design. This is of great significance as its findings are highly relevant due to the development of more advanced in vitro, and in silico models aiming to improve physiologically relevant toxicological testing strategies and bridging the gap between in vitro and in vivo experimentation.

The interaction between nanoparticles-protein corona complex and cells and its toxic effect on cells

Once nanoparticles (NPs) contact with the biological fluids, the proteins immediately adsorb onto their surface, forming a layer called protein corona (PC), which bestows the biological identity on NPs. Importantly, the NPs-PC complex is the true identity of NPs in physiological environment. Based on the affinity and the binding and dissociation rate, PC is classified into soft protein corona, hard protein corona, and interfacial protein corona. Especially, the hard PC, a protein layer relatively stable and closer to their surface, plays particularly important role in the biological effects of the complex. However, the abundant corona proteins rarely correspond to the most abundant proteins found in biological fluids. The composition profile, formation and conformational change of PC can be affected by many factors. Here, the influence factors, not only the nature of NPs, but also surface chemistry and biological medium, are discussed. Likewise, the formed PC influences the interaction between NPs and cells, and the associated subsequent cellular uptake and cytotoxicity. The uncontrolled PC formation may induce undesirable and sometimes opposite results: increasing or inhibiting cellular uptake, hindering active targeting or contributing to passive targeting, mitigating or aggravating cytotoxicity, and stimulating or mitigating the immune response. In the present review, we discuss these aspects and hope to provide a valuable reference for controlling protein adsorption, predicting their behavior in vivo experiments and designing lower toxicity and enhanced targeting nanomedical materials for nanomedicine.

Radiocesium concentration in indoor air during residential house cleaning in Fukushima Dai-ichi nuclear power plant evacuation areas

After the Fukushima Dai-ichi Nuclear Power Plant (FDNPP) accident, outdoor decontamination was conducted by the Japanese Government, whereas indoor contamination was the responsibility of individual residents. However, no data exist regarding ¹³⁷Cs exposure during indoor cleaning. Therefore, indoor ¹³⁷Cs radioactivity concentrations in indoor air were determined during cleaning in 60 houses within the evacuation area near the FDNPP, Fukushima Prefecture, Japan. Radiocesium activity concentrations per cubic meter of indoor air during dusting (mean ± SD (median)) was 6.8 ± 7.9 (4.7) and 1.6 ± 2.7 (0.78) Bq/m³ for all aerodynamic diameter of aerosol particle and PM2.5, respectively. Radiocesium activity concentrations in indoor air decreased with decreasing the aerodynamic diameter of aerosol particles (mean: 0.099, 0.22, 0.41, 0.92, 2.2, and 2.9 Bq/m³ for the aerodynamic diameter of <0.25, 0.25-0.5, 0.5-1.0, 1.0-2.5, 2.5-6.6, and >6.6 μm, respectively) and was inversely proportional to the square of the distance from the FDNPP. Indoor ¹³⁷Cs radioactivity concentrations were significantly higher during dusting than during vacuuming with either a cyclone handy cleaner or a normal vacuum cleaner. The mean deposited activities in tracheobronchial and alveolar regions was estimated to be 1.9 and 2.8 Bq, respectively, during a 2-h dusting period in the studied houses. For values below the detection limit, half of the detection limit was used for calculating the means and SDs.

Toxic effects and involved molecular pathways of nanoparticles on cells and subcellular organelles

Owing to the increasing application of engineered nanoparticles (NPs), besides the workplace, human beings are also exposed to NPs from nanoproducts through the skin, respiratory tract, digestive tract and vein injection. This review states pathways of cellular uptake, subcellular distribution and excretion of NPs. The uptake pathways commonly include phagocytosis, micropinocytosis, clathrin- and caveolae-mediated endocytosis, scavenger receptor-related pathway, clathrin- or caveolae-independent pathway, and direct penetration or insertion. Then the ability of NPs to decrease cell viability and metabolic activity, change cell morphology, and destroy cell membrane, cytoskeleton and cell function was presented. In addition, the lowest dose decreasing cell metabolic viability compared with the control or IC₅₀ of silver, titanium dioxide, zinc oxide, carbon black, carbon nanotubes, silica, silicon NPs and cadmium telluride quantum dots to some cell lines was gathered. Next, this review attempts to increase our understanding of NP-caused adverse effects on organelles, which have implications in mitochondrial dysfunction, endoplasmic reticulum stress and lysosomal rupture. In particular, the disturbance of mitochondrial biogenesis and mitochondrial dynamic fusion-fission, mitophagy and cytochrome c-dependent apoptosis are involved. In addition, prolonged endoplasmic reticulum stress will result in apoptosis. Rupture of the lysosomal membrane was associated with inflammation, and both induction of autophagy and blockade of autophagic flow can result in cytotoxicity. Finally, the network mechanism of the combined action of multiple organelle dysfunction, apoptosis, autophagy and oxidative stress was discussed.

Toxic Effects of Low-Level Long-Term Inhalation Exposures of Rats to Nickel Oxide Nanoparticles

Rats were exposed to nickel oxide nanoparticles (NiO-NP) inhalation at 0.23 ± 0.01 mg/m³ for 4 h a day 5 times a week for up to 10 months. The rat organism responded to this impact with changes in cytological and some biochemical characteristics of the bronchoalveolar lavage fluid along with a paradoxically little pronounced pulmonary pathology associated with a rather low chronic retention of nanoparticles in the lungs. There were various manifestations of systemic toxicity, including damage to the liver and kidneys; a likely allergic syndrome as indicated by some cytological signs; transient stimulation of erythropoiesis; and penetration of nickel into the brain from the nasal mucous membrane along the olfactory pathway. Against a picture of mild to moderate chronic toxicity of nickel, its in vivo genotoxic effect assessed by the degree of DNA fragmentation in nucleated blood cells (the RAPD test) was pronounced, tending to increasing with the length of the exposure period. When rats were given orally, in parallel with the toxic exposure, a set of innocuous substances with differing mechanisms of expected bioprotective action, the genotoxic effect of NiO-NPs was found to be substantially attenuated.

Calcium-dependent cyto- and genotoxicity of nickel metal and nickel oxide nanoparticles in human lung cells

Background

Genotoxicity is an important toxicological endpoint due to the link to diseases such as cancer. Therefore, an increased understanding regarding genotoxicity and underlying mechanisms is needed for assessing the risk with exposure to nanoparticles (NPs). The aim of this study was to perform an in-depth investigation regarding the genotoxicity of well-characterized Ni and NiO NPs in human bronchial epithelial BEAS-2B cells and to discern possible mechanisms. Comparisons were made with NiCl₂ in order to elucidate effects of ionic Ni.

Methods

BEAS-2B cells were exposed to Ni and NiO NPs, as well as NiCl₂, and uptake and cellular dose were investigated by transmission electron microscopy (TEM) and inductively coupled plasma mass spectrometry (ICP-MS). The NPs were characterized in terms of surface composition (X-ray photoelectron spectroscopy), agglomeration (photon cross correlation spectroscopy) and nickel release in cell medium (ICP-MS). Cell death (necrosis/apoptosis) was investigated by Annexin V-FITC/PI staining and genotoxicity by cytokinesis-block micronucleus (cytome) assay (OECD 487), chromosomal aberration (OECD 473) and comet assay. The involvement of intracellular reactive oxygen species (ROS) and calcium was explored using the fluorescent probes, DCFH-DA and Fluo-4.

Results

NPs were efficiently taken up by the BEAS-2B cells. In contrast, no or minor uptake was observed for ionic Ni from NiCl₂. Despite differences in uptake, all exposures (NiO, Ni NPs and NiCl₂) caused chromosomal damage. Furthermore, NiO NPs were most potent in causing DNA strand breaks and generating intracellular ROS. An increase in intracellular calcium was observed and modulation of intracellular calcium by using inhibitors and chelators clearly prevented the chromosomal damage. Chelation of iron also protected against induced damage, particularly for NiO and NiCl₂.

Conclusions

This study has revealed chromosomal damage by Ni and NiO NPs as well as Ni ionic species and provides novel evidence for a calcium-dependent mechanism of cyto- and genotoxicity.

Electronic supplementary material

The online version of this article (10.1186/s12989-018-0268-y) contains supplementary material, which is available to authorized users.