Mechanism-based genotoxicity screening of metal oxide nanoparticles using the ToxTracker panel of reporter cell lines

Nano-priming of pea (Pisum sativum L.) seeds with CuO nanoparticles: Synthesis, stabilization, modeling, characterization, and comprehensive effect on germination and seedling parameters

CuO nanoparticles (NPs) can boost germination and seedling development of agricultural crops. However, it is either extremely contradictory or difficult to compare in terms of doses, dimension, nature, stability of CuO NPs and activity of stabilizing agents. This study focused on synthesis and characterization of CuO NPs stabilized with various polysaccharides. CuO NPs-hyaluronic acid complex was the most energetically favorable and stable. 0.1 mg/L CuO NPs led to the highest germination energy, germinability, and root and seedling lengths, while higher concentrations had growth suppression or inhibition effect on seedling and root development. Histological studies showed noticeable structural changes caused by intense Cu translocation and accumulation: Cu content reached 56.01 μg/L at 100 mg/L CuO NPs, which affected antioxidant activity and photosynthesis indicators. Interestingly, the growth-stimulating effect of CuO NPs stabilized with hyaluronic acid at a concentration of 0.1 mg/L, contrasted with a pronounced toxic effect observed at 100 mg/L.

Bridging the gap: Innovative human-based in vitro approaches for nanomaterials hazard assessment and their role in safe and sustainable by design, risk assessment, and life cycle assessment

The application of nanomaterials in industry and consumer products is growing exponentially, which has pressed the development and use of predictive human in vitro models in pre-clinical analysis to closely extrapolate potential toxic effects in vivo. The conventional cytotoxicity investigation of nanomaterials using cell lines from cancer origin and culturing them two-dimensionally in a monolayer without mimicking the proper pathophysiological microenvironment may affect a precise prediction of in vitro effects at in vivo level. In recent years, complex in vitro models (also belonging to the new approach methodologies, NAMs) have been established in unicellular to multicellular cultures either by using cell lines, primary cells or induced pluripotent stem cells (iPSCs), and reconstituted into relevant biological dimensions mimicking in vivo conditions. These advanced in vitro models retain physiologically reliant exposure scenarios particularly appropriate for oral, dermal, respiratory, and intravenous administration of nanomaterials, which have the potential to improve the in vivo predictability and lead to reliable outcomes. In this perspective, we discuss recent developments and breakthroughs in using advanced human in vitro models for hazard assessment of nanomaterials. We identified fit-for-purpose requirements and remaining challenges for the successful implementation of in vitro data into nanomaterials Safe and Sustainable by Design (SSbD), Risk Assessment (RA), and Life Cycle Assessment (LCA). By addressing the gap between in vitro data generation and the utility of in vitro data for nanomaterial safety assessments, a prerequisite for SSbD approaches, we outlined potential key areas for future development.

An in vitro toxicological assessment of two electronic cigarettes: E-liquid to aerosolisation

Interest in the toxicological assessment of iterations of e-cigarette devices, e-liquid formulations and flavour use is increasing. Here, we describe a multiple test matrix and in vitro approach to assess the biological impact of differing e-cigarette activation mechanism (button vs. puff-activated) and heating technology (cotton vs. ceramic wick). The e-liquids selected for each device contained the same nicotine concentration and flavourings. We tested both e-liquid and aqueous extract of e-liquid aerosol using a high throughput cytotoxicity and genotoxicity screen. We also conducted whole aerosol assessment both in a reconstituted human airway lung tissue (MucilAir) with associated endpoint assessment (cytotoxicity, TEER, cilia beat frequency and active area) and an Ames whole aerosol assay with up to 900 consecutive undiluted puffs. Following this testing it is shown that the biological impact of these devices is similar, taking into consideration the limitations and capturing efficiencies of the different testing matrices. We have contextualised these responses against previous published reference cigarette data to establish the comparative reduction in response consistent with reduced risk potential of the e-cigarette products tested in this study as compared to conventional cigarettes.

Nanotoxicity of multifunctional stoichiometric cobalt oxide nanoparticles (SCoONPs) with repercussions toward apoptosis, necrosis, and cancer necrosis factor (TNF-α) at nano-biointerfaces

Introduction

Apoptosis, necrosis, and cancer necrosis factor (TNF-a) are all impacted by the nanotoxicity of multifunctional stoichiometric cobalt oxide nanoparticles (SCoONPs) at nano-biointerfaces. The creation of multi-functional nanoparticles has had a considerable impact on the transport of drugs and genes, nanotheranostics (in-vivo imaging, concurrent diagnostics), interventions for external healing, the creation of nano-bio interfaces, and the instigation of desired changes in nanotherapeutics.

Objectives

The quantitative structure-activity relationships, chemical transformations, biological interactions as well as toxicological analyses are considered as main objectives. Discrete dimensions of SCoNPs-cell interaction interfaces, their characteristic physical features (size, shape, shell structure, and surface chemistry), impact on cell proliferation and differentiation are the key factors responsible for nanotoxicity.

Methods

The development of multi-functional nanoparticles has been significant in drug/gene delivery, nanotheranostics (in-vivo imaging, coinciding diagnostics), and external healing interventions, designing a nano-bio interface, as well as inciting desired alterations in nanotherapeutics. Every so often, the cellular uptake of multi-functional cobalt [Co, CoO, Co2(CO)8 and Co3O4] nanoparticles (SCoONPs) influences cellular mechanics and initiates numerous repercussions (oxidative stress, DNA damage, cytogenotoxicity, and chromosomal damage) in pathways, including the generation of dysregulating factors involved in biochemical transformations.

Results

The concerns and influences of multifunctional SCoNPs on different cell mechanisms (mitochondria impermeability, hydrolysis of ATP, the concentration of Ca2+, impaired calcium clearance, defective autophagy, apoptosis, and necrosis), and interlinked properties (adhesion, motility, and internalization dynamics, role in toxicity, surface hydrophilic and hydrophobicity, biokinetics and biomimetic behaviors of biochemical reactions) have also been summarized. SCoONPs have received a lot of interest among the nanocarriers family because of its advantageous qualities such as biodegradability, biocompatibility, nontoxicity, and nonimmunogenicity.

Conclusion

Various applications, such as bio-imaging, cell labeling, gene delivery, enhanced chemical stability, and increased biocompatibility, concerning apoptosis, necrosis, and nano-bio interfaces, along with suitable examples. In this analysis, the multi-functional cobalt [Co, CoO, Co2(CO)8 and Co3O4] nanoparticles (SCoNPs) intricacies (cytogenotoxicity, clastogenicity, and immunomodulatory), nanotoxicity, and associated repercussions have been highlighted and explained.

Heavily Gd-Doped Non-Toxic Cerium Oxide Nanoparticles for MRI Labelling of Stem Cells

Recently, human mesenchymal stem cells (hMSc) have attracted a great deal of attention as potential therapeutic agents in the treatment of socially significant diseases. Despite substantial advances in stem-cell therapy, the biological mechanisms of hMSc action after transplantation remain unclear. The use of magnetic resonance imaging (MRI) as a non-invasive method for tracking stem cells in the body is very important for analysing their distribution in tissues and organs, as well as for ensuring control of their lifetime after injection. Herein, detailed experimental data are reported on the biocompatibility towards hMSc of heavily gadolinium-doped cerium oxide nanoparticles (Ce_0.8Gd_0.2O_2-x) synthesised using two synthetic protocols. The relaxivity of the nanoparticles was measured in a magnetic field range from 1 mT to 16.4 T. The relaxivity values (r₁ = 11 ± 1.2 mM^-1 s^-1 and r₁ = 7 ± 1.2 mM^-1 s^-1 in magnetic fields typical of 1.5 and 3 T MRI scanners, respectively) are considerably higher than those of the commercial Omniscan MRI contrast agent. The low toxicity of gadolinium-doped ceria nanoparticles to hMSc enables their use as an effective theranostic tool with improved MRI-contrasting properties.

Silver nanoparticles with excellent biocompatibility block pseudotyped SARS-CoV-2 in the presence of lung surfactant

Silver (Ag) is known to possess antimicrobial properties which is commonly attributed to soluble Ag ions. Here, we showed that Ag nanoparticles (NPs) potently inhibited SARS-CoV-2 infection using two different pseudovirus neutralization assays. We also evaluated a set of Ag nanoparticles of different sizes with varying surface properties, including polyvinylpyrrolidone (PVP)-coated and poly (ethylene glycol) (PEG)-modified Ag nanoparticles, and found that only the bare (unmodified) nanoparticles were able to prevent virus infection. For comparison, TiO₂ nanoparticles failed to intercept the virus. Proteins and lipids may adsorb to nanoparticles forming a so-called bio-corona; however, Ag nanoparticles pre-incubated with pulmonary surfactant retained their ability to block virus infection in the present model. Furthermore, the secondary structure of the spike protein of SARS-CoV-2 was perturbed by the Ag nanoparticles, but not by the ionic control (AgNO₃) nor by the TiO₂ nanoparticles. Finally, Ag nanoparticles were shown to be non-cytotoxic towards the human lung epithelial cell line BEAS-2B and this was confirmed by using primary human nasal epithelial cells. These results further support that Ag nanoparticles may find use as anti-viral agents.

Chemically functionalized CuO/Sodium alginate grafted polyaniline for nonenzymatic potentiometric detection of chlorpyrifos

Non-enzymatic sensing of chlorpyrifos (CPF) has been demonstrated over structurally functionalized the ternary bio nanocomposite comprised of cupric oxide, sodium alginate, and polyaniline-based hybrid (CuO/SA-g-PANI) based electrode using a laboratory designed portable potentiometric set up. The prepared composite and constituents were characterized for structure, morphology, and physical properties with the help of fourier transform infrared, X-ray diffraction, Scanning electron microscope, and other relevant standard methods. The obtained results revealed the formation of porous, electrical conductivity, structurally functionalized, responsiveness composite due to molecular engineering, and structural synergism for sensing applications. Further, the film of the prepared composite was explored as the electrode for nonenzymatic potentiometric sensing of residual chlorpyrifos in synthetic and natural sample i.e., tap water, soil, mango, and cabbage. The sensor exhibits a wider sensing range 1.0-120.0 μM, improved sensitivity 1.8790 mV·μM-1·cm-2, detection limit 0.375 μM, response time 120 s, recovery time 16 s with 99.80 % accuracy, and stability of 72 days at neutral 7.0 pH and ambient temperature i.e. 25 °C. Further, the sensing mechanism has been also explained on the basis of structural change in CPF and electrode materials due to their surface interaction along with formation induced electrode potential.

Nanosafety: An Evolving Concept to Bring the Safest Possible Nanomaterials to Society and Environment

The use of nanomaterials has been increasing in recent times, and they are widely used in industries such as cosmetics, drugs, food, water treatment, and agriculture. The rapid development of new nanomaterials demands a set of approaches to evaluate the potential toxicity and risks related to them. In this regard, nanosafety has been using and adapting already existing methods (toxicological approach), but the unique characteristics of nanomaterials demand new approaches (nanotoxicology) to fully understand the potential toxicity, immunotoxicity, and (epi)genotoxicity. In addition, new technologies, such as organs-on-chips and sophisticated sensors, are under development and/or adaptation. All the information generated is used to develop new in silico approaches trying to predict the potential effects of newly developed materials. The overall evaluation of nanomaterials from their production to their final disposal chain is completed using the life cycle assessment (LCA), which is becoming an important element of nanosafety considering sustainability and environmental impact. In this review, we give an overview of all these elements of nanosafety.

Statement on the BfR opinion regarding the toxicity of 2-chloroethanol

In accordance with Art. 31(1) of Regulation (EC) No 178/2002, the Commission asked EFSA to provide a scientific review on the BfR opinion on the 'Health risk assessment of ethylene oxide residues in sesame seeds' (Opinion No 024/2021) regarding the toxicity of 2-chloroethanol. In addition, EFSA was asked to clarify under which circumstances the use of the MOE approach is considered appropriate. Based on the information available to EFSA, i.e. the studies assessed in the frame of the BfR opinion and additional data provided by stakeholders not assessed by BfR, EFSA considers the genotoxicity of 2-chloroethanol as inconclusive. On this basis, EFSA would not recommend setting reference points for risk assessment or health-based guidance values until the genotoxic potential of 2-chloroethanol is clarified. EFSA therefore recommends performing new in vitro gene mutation and in vitro micronucleus tests with 2-chloroethanol following the recommendations of the most recent OECD technical guidelines to clarify its genotoxic potential. If the result of any of the test is positive, the recommendations of the EFSA Scientific Committee (2011) should be followed. If the genotoxic potential of 2-chloroethanol is finally clarified and overall negative, EFSA would recommend setting the reference point for deriving health-based guidance values based on existing toxicity studies on 2-chloroethanol.

A tiered approach to investigate the inhalation toxicity of cobalt substances. Tier 2 b: Reactive cobalt substances induce oxidative stress in ToxTracker and activate hypoxia target genes

Cobalt metal and cobalt sulfate are carcinogenic in rodents following inhalation exposure. The pre-carcinogenic effects associated with exposure to these cobalt substances include oxidative stress and genotoxicity. Some, but not all, cobalt substances induce in vitro clastogenicity or an increase in micronuclei. As a result, these substances are classified genotoxic carcinogens, having major impacts on their risk assessment, e.g. assumption of a non-thresholded dose response. Here, we investigated the potential of nine cobalt substances to cause genotoxicity and oxidative stress using the ToxTracker assay, with an extension to measure biomarkers of hypoxia. None of the nine tested substances activated the DNA damage markers in ToxTracker, and five substances activated the oxidative stress response reporters. The same five substances also activated the expression of several hypoxia target genes. Consistent with the lower tier of testing found in the preceding paper of this series, these compounds can be grouped based on their ability to release bioavailable cobalt ion and to trigger subsequent key events.

Toxicity of stainless and mild steel particles generated from gas-metal arc welding in primary human small airway epithelial cells

Welding fumes induce lung toxicity and are carcinogenic to humans but the molecular mechanisms have yet to be clarified. The aim of this study was to evaluate the toxicity of stainless and mild steel particles generated via gas-metal arc welding using primary human small airway epithelial cells (hSAEC) and ToxTracker reporter murine stem cells, which track activation of six cancer-related pathways. Metal content (Fe, Mn, Ni, Cr) of the particles was relatively homogenous across particle size. The particles were not cytotoxic in reporter stem cells but stainless steel particles activated the Nrf2-dependent oxidative stress pathway. In hSAEC, both particle types induced time- and dose-dependent cytotoxicity, and stainless steel particles also increased generation of reactive oxygen species. The cellular metal content was higher for hSAEC compared to the reporter stem cells exposed to the same nominal dose. This was, in part, related to differences in particle agglomeration/sedimentation in the different cell media. Overall, our study showed differences in cytotoxicity and activation of cancer-related pathways between stainless and mild steel welding particles. Moreover, our data emphasizes the need for careful assessment of the cellular dose when comparing studies using different in vitro models.

The in vitro ToxTracker and Aneugen Clastogen Evaluation extension assay as a tool in the assessment of relative genotoxic potential of e-liquids and their aerosols

In vitro (geno)toxicity assessment of electronic vapour products (EVPs), relative to conventional cigarette, currently uses assays, including the micronucleus and Ames tests. Whilst informative on induction of a finite endpoint and relative risk posed by test articles, such assays could benefit from mechanistic supplementation. The ToxTracker and Aneugen Clastogen Evaluation analysis can indicate the activation of reporters associated with (geno)toxicity, including DNA damage, oxidative stress, the p53-related stress response and protein damage. Here, we tested for the different effects of a selection of neat e-liquids, EVP aerosols and Kentucky reference 1R6F cigarette smoke samples in the ToxTracker assay. The assay was initially validated to assess whether a mixture of e-liquid base components, propylene glycol (PG) and vegetable glycerine (VG) had interfering effects within the system. This was achieved by spiking three positive controls into the system with neat PG/VG or phosphate-buffered saline bubbled (bPBS) PG/VG aerosol (nicotine and flavour free). PG/VG did not greatly affect responses induced by the compounds. Next, when compared to cigarette smoke samples, neat e-liquids and bPBS aerosols (tobacco flavour; 1.6% freebase nicotine, 1.6% nicotine salt or 0% nicotine) exhibited reduced and less complex responses. Tested up to a 10% concentration, EVP aerosol bPBS did not induce any ToxTracker reporters. Neat e-liquids, tested up to 1%, induced oxidative stress reporters, thought to be due to their effects on osmolarity in vitro. E-liquid nicotine content did not affect responses induced. Additionally, spiking nicotine alone only induced an oxidative stress response at a supraphysiological level. In conclusion, the ToxTracker assay is a quick, informative screen for genotoxic potential and mechanisms of a variety of (compositionally complex) samples, derived from cigarettes and EVPs. This assay has the potential for future application in the assessment battery for next-generation (smoking alternative) products, including EVPs.

Adverse Outcome Pathway Development for Assessment of Lung Carcinogenicity by Nanoparticles

Lung cancer, one of the most common and deadly forms of cancer, is in some cases associated with exposure to certain types of particles. With the rise of nanotechnology, there is concern that some engineered nanoparticles may be among such particles. In the absence of epidemiological evidence, assessment of nanoparticle carcinogenicity is currently performed on a time-consuming case-by-case basis, relying mainly on animal experiments. Non-animal alternatives exist, including a few validated cell-based methods accepted for regulatory risk assessment of nanoparticles. Furthermore, new approach methodologies (NAMs), focused on carcinogenic mechanisms and capable of handling the increasing numbers of nanoparticles, have been developed. However, such alternative methods are mainly applied as weight-of-evidence linked to generally required animal data, since challenges remain regarding interpretation of the results. These challenges may be more easily overcome by the novel Adverse Outcome Pathway (AOP) framework, which provides a basis for validation and uptake of alternative mechanism-focused methods in risk assessment. Here, we propose an AOP for lung cancer induced by nanosized foreign matter, anchored to a selection of 18 standardized methods and NAMs for in silico- and in vitro-based integrated assessment of lung carcinogenicity. The potential for further refinement of the AOP and its components is discussed in relation to available nanosafety knowledge and data. Overall, this perspective provides a basis for development of AOP-aligned alternative methods-based integrated testing strategies for assessment of nanoparticle-induced lung cancer.

Silver nanoparticles: Correlating particle size and ionic Ag release with cytotoxicity, genotoxicity, and inflammatory responses in human cell lines

The widespread use of silver nanoparticles (AgNPs), their many sources for human exposure, and the ability of AgNPs to enter organisms and induce general toxicological responses have raised concerns regarding their public health and environmental safety. To elucidate the differential toxic effects of polyvinylpyrrolidone-capped AgNPs with different primary particle sizes (i.e. 5, 50, and 75 nm), we performed a battery of cytotoxicity and genotoxicity assays and examined the inflammatory responses in two human cell lines (i.e. HepG2 and A549). Concentration-dependent decreases in cell proliferation and mitochondrial membrane potential and increases in cytokine (i.e. interleukin-6 and interleukin-8) excretion indicated disruption of mitochondrial function and inflammation as the main mediating factors of AgNPs-induced cytotoxicity. An incremental increase in genotoxicity with decreasing AgNPs diameter was noted in HepG2 cells, which was associated with S and G2/M accumulation and transcriptional activation of the GADD45α promoter as reflected by luciferase activity. Dose-related genetic damage, as indicated by Olive tail moment and micronucleus formation, was also observed in A549 cells, but these effects as well as the AgNPs-induced cytotoxicity were more associated with ionic Ag release from nanoparticles (NPs). In summary, the present study addressed different toxicity mechanisms of AgNPs, depending on the cell model, toxicological endpoint, particle size, and degree of Ag+ release from NPs. The results suggest that the GADD45α promoter-driven luciferase reporter cell system provided a rapid screening tool for the identification of genotoxic properties of NPs across a range of different sizes and concentrations.

Phosphate Buffer Solubility and Oxidative Potential of Single Metals or Multielement Particles of Welding Fumes

To evaluate the chemical behavior and the health impact of welding fumes (WF), a complex and heterogeneous mixture of particulate metal oxides, two certified reference materials (CRMs) were tested: mild steel WF (MSWF-1) and stainless steel WF (SSWF-1). We determined their total chemical composition, their solubility, and their oxidative potential in a phosphate buffer (PB) solution under physiological conditions (pH 7.4 and 37 °C). The oxidative potential (OPDTT) of WF CRMs was evaluated using an acellular method by following the dithiothreitol (DTT) consumption rate (µmol DTT L−1 min−1). Pure metal salts present in the PB soluble fraction of the WF CRMs were tested individually at equivalent molarity to estimate their specific contribution to the total OPDTT. The metal composition of MSWF-1 consisted mainly of Fe, Zn, Mn, and Cu and the SSWF-1 composition consisted mainly of Fe, Mn, Cr, Ni, Cu, and Zn, in diminishing order. The metal PB solubility decreased from Cu (11%) to Fe (approximately 0.2%) for MSWF-1 and from Mn (9%) to Fe (<1%) for SSWF-1. The total OPDTT of SSWF-1 is 2.2 times the OPDTT of MSWF-1 due to the difference in oxidative capacity of soluble transition metals. Cu (II) and Mn (II) are the most sensitive towards DTT while Cr (VI), Fe (III), and Zn (II) are barely reactive, even at higher concentrations. The OPDTT measured for both WF CRMs extracts compare well with simulated extracts containing the main metals at their respective PB-soluble concentrations. The most soluble transition metals in the simulated extract, Mn (II) and Cu (II), were the main contributors to OPDTT in WF CRMs extracts. Mn (II), Cu (II), and Ni (II) might enhance the DTT oxidation by a redox catalytic reaction. However, summing the main individual soluble metal DTT response induces a large overestimation probably linked to modifications in the speciation of various metals when mixed. The complexation of metals with different ligands present in solution and the interaction between metals in the PB-soluble fraction are important phenomena that can influence OPDTT depletion and therefore the potential health effect of inhaled WF.

A novel assessment system of toxicity and stability of CuO nanoparticles via copper super sensitive Saccharomyces cerevisiae mutants

CuO nanoparticles (CuO-NPs) toxicity in organisms is contributed mainly through the copper uptake by both the ionic and nanoparticle form. However, the relative uptake ratio and bioavailability of the two different forms is not well known due to a lack of sensitive and effective assessment systems. We developed a series of both copper resistant and hyper sensitive Saccharomyces cerevisiae mutants to investigate and compare the effects of CuO-NPs and dissolved copper (CuCl₂), on the eukaryote with the purpose of quantitating the relative contributions of nanoparticles and dissolved species for Cu uptake. We observed the toxicity of 10 mM CuO-NPs for copper sensitive strains is equal to that of 0.5 mM CuCl₂ and the main toxic effect is most likely generated from oxidative stress through reactive oxygen species (ROS) production. About 95% CuO-NPs exist in nanoparticle form under neutral environmental conditions. Assessing the cellular metal content of wild type and copper transporter 1(CTR1) knock out cells showed that endocytosis is the major absorption style for CuO-NPs. This study also found a similar toxicity of Ag for both 10 mM Ag-NPs and 0.2 mM AgNO₃ in the copper super sensitive strains. Our study revealed the absorption mechanism of soluble metal based nanomaterials CuO-NPs and Ag-NPs as well as provided a sensitive and delicate system to precisely evaluate the toxicity and stability of nanoparticles.

In vitro copper oxide nanoparticle toxicity on intestinal barrier

The use of CuO nanoparticles (NPs) has increased greatly and their potential effects on human health need to be investigated. Differentiated Caco-2 cells were treated from the apical (Ap) and the basolateral (Bl) compartment with different concentrations (0, 10, 50 and 100 μg/mL) of commercial or sonochemically synthesized (sono) CuO NPs. Sono NPs were prepared in ethanol (CuOe) or in water (CuOw), obtaining CuO NPs differing in size and shape. The effects on the Caco-2 cell barrier were assessed via transepithelial electrical resistance (TEER) evaluation just before and after 1, 2 and 24 hours of exposure and through the analysis of cytokine release and biomarkers of oxidative damage to proteins after 24 hours. Sono CuOe and CuOw NPs induced a TEER decrease with a dose-dependent pattern after Bl exposure. Conversely, TEER values were not affected by the Ap exposure to commercial CuO NPs and, concerning the Bl exposure, only the lowest concentration tested (10 μg/mL) caused a TEER decrease after 24 hours of exposure. An increased release of interleukin-8 was induced by sono CuO NPs after the Ap exposure to 100 μg/mL and by sono and commercial CuO after the Bl exposure to all the concentrations. No effects of commercial and sono CuO NPs on interleukin-6 (with the only exception of 100 μg/mL Bl commercial CuO) and tumor necrosis factor-α release were observed. Ap treatment with commercial and CuOw NPs was able to induce significant alterations on specific biomarkers of protein oxidative damage (protein sulfhydryl group oxidation and protein carbonylation).

Genotoxicity of Nanomaterials: Advanced In Vitro Models and High Throughput Methods for Human Hazard Assessment-A Review

Changes in the genetic material can lead to serious human health defects, as mutations in somatic cells may cause cancer and can contribute to other chronic diseases. Genotoxic events can appear at both the DNA, chromosomal or (during mitosis) whole genome level. The study of mechanisms leading to genotoxicity is crucially important, as well as the detection of potentially genotoxic compounds. We consider the current state of the art and describe here the main endpoints applied in standard human in vitro models as well as new advanced 3D models that are closer to the in vivo situation. We performed a literature review of in vitro studies published from 2000-2020 (August) dedicated to the genotoxicity of nanomaterials (NMs) in new models. Methods suitable for detection of genotoxicity of NMs will be presented with a focus on advances in miniaturization, organ-on-a-chip and high throughput methods.

A Next-Generation Risk Assessment Case Study for Coumarin in Cosmetic Products

Next-Generation Risk Assessment is defined as an exposure-led, hypothesis-driven risk assessment approach that integrates new approach methodologies (NAMs) to assure safety without the use of animal testing. These principles were applied to a hypothetical safety assessment of 0.1% coumarin in face cream and body lotion. For the purpose of evaluating the use of NAMs, existing animal and human data on coumarin were excluded. Internal concentrations (plasma Cmax) were estimated using a physiologically based kinetic model for dermally applied coumarin. Systemic toxicity was assessed using a battery of in vitro NAMs to identify points of departure (PoDs) for a variety of biological effects such as receptor-mediated and immunomodulatory effects (Eurofins SafetyScreen44 and BioMap Diversity 8 Panel, respectively), and general bioactivity (ToxCast data, an in vitro cell stress panel and high-throughput transcriptomics). In addition, in silico alerts for genotoxicity were followed up with the ToxTracker tool. The PoDs from the in vitro assays were plotted against the calculated in vivo exposure to calculate a margin of safety with associated uncertainty. The predicted Cmax values for face cream and body lotion were lower than all PoDs with margin of safety higher than 100. Furthermore, coumarin was not genotoxic, did not bind to any of the 44 receptors tested and did not show any immunomodulatory effects at consumer-relevant exposures. In conclusion, this case study demonstrated the value of integrating exposure science, computational modeling and in vitro bioactivity data, to reach a safety decision without animal data.

Genotoxicity and cellular uptake of nanosized and fine copper oxide particles in human bronchial epithelial cells in vitro

We studied the genotoxicity and cellular uptake of nanosized (<50 nm) and fine (<10 μm) copper oxide (CuO) particles in vitro in human bronchial epithelial (BEAS-2B) cells. In addition, the effect of dispersing the particles using bovine serum albumin (BSA) on DNA damage induction was investigated. DNA damage was assessed by the alkaline comet (single cell gel electrophoresis) assay after 3-h, 6-h and 24-h exposures. The cytokinesis-block micronucleus assay was applied to study chromosome damage. Both fine- and nanosized CuO particles induced a dose-dependent increase in DNA damage at all timepoints tested. However, nanosized CuO damaged DNA at lower doses and higher levels compared with fine CuO. Dispersing the nanoparticles in the presence of BSA (0.6 mg/mL) resulted in a small and inconsistent decrease in DNA damage compared with dispersions in serum-free cell culture medium only. CuO nanoparticles induced a clear dose-dependent increase in micronucleated cells at doses that strongly increased cytostasis and were markedly cytotoxic at 24 and 48 h. Fine CuO showed a slight induction of micronuclei. Hyperspectral microscopy indicated a substantial cellular uptake of both types of particles after a 3-h exposure to a dose of 20 μg/cm². The number of particles internalized by the cells was higher for nanosized than fine CuO, as quantified by the frequency of spectral matches in the total cell area and by the number of spectrally matched visible particles or agglomerates per cell. The particle uptake was limited by particle size. The stronger genotoxic activity of nanosized than fine CuO particles is likely to derive from the higher cellular uptake and more effective intracellular dissolution of nanoparticles.

ToxTracker Reporter Cell Lines as a Tool for Mechanism-Based (geno)Toxicity Screening of Nanoparticles-Metals, Oxides and Quantum Dots

The increased use of nanoparticles (NPs) requires efficient testing of their potential toxic effects. A promising approach is to use reporter cell lines to quickly assess the activation of cellular stress response pathways. This study aimed to use the ToxTracker reporter cell lines to investigate (geno)toxicity of various metal- or metal oxide NPs and draw general conclusions on NP-induced effects, in combination with our previous findings. The NPs tested in this study (n = 18) also included quantum dots (QDs) in different sizes. The results showed a large variation in cytotoxicity of the NPs tested. Furthermore, whereas many induced oxidative stress only few activated reporters related to DNA damage. NPs of manganese (Mn and Mn₃O₄) induced the most remarkable ToxTracker response with activation of reporters for oxidative stress, DNA damage, protein unfolding and p53-related stress. The QDs (CdTe) were highly toxic showing clearly size-dependent effects and calculations suggest surface area as the most relevant dose metric. Of all NPs investigated in this and previous studies the following induce the DNA damage reporter; CuO, Co, CoO, CdTe QDs, Mn, Mn₃O₄, V₂O₅, and welding NPs. We suggest that these NPs are of particular concern when considering genotoxicity induced by metal- and metal oxide NPs.

Engineered metal oxide nanomaterials inhibit corneal epithelial wound healing in vitro and in vivo

Ocular exposure to metal oxide engineered nanomaterials (ENMs) is common as exemplified by zinc oxide (ZnO), a major constituent of sunscreens and cosmetics. The ocular surface that includes the transparent cornea and its protective tear film are common sites of exposure for metal ENMs. Despite the frequency of exposure of the ocular surface, there is a knowledge gap regarding the effects of metal oxide ENMs on the cornea in health and disease. Therefore, we studied the effects of metal oxide ENMs on the cornea in the presence or absence of injury. Cell viability of immortalized human corneal epithelial (hTCEpi) cells was assessed following treatment with 11 metal oxide ENMs with a concentration ranging from 0.5 to 250 μg/mL for 24 hours. An epithelial wound healing assay with a monolayer of hTCEpi cells was then performed using 11 metal oxide ENMs at select concentrations based on data from the viability assays. Subsequently, based on the in vitro results, in vivo testing of precorneal tear film (PTF) quantity and stability as well as a corneal epithelial wound healing were tested in the presence or absence ZnO or vanadium pentoxide (V₂O₅) at a concentration of 50 μg/mL. We found that WO₃, ZnO, V₂O₅ and CuO ENMs significantly reduced hTCEpi cell viability in comparison to vehicle control or the other metal oxide ENMs tested. Furthermore, ZnO and V₂O₅ ENMs also significantly decreased hTCEpi cell migration. Although ZnO and V₂O₅ did not alter PTF parameters of rabbits in vivo, corneal epithelial wound healing was significantly delayed by topical ZnO while V₂O₅ did not alter wound healing. Finally, hyperspectral images confirmed penetration of ZnO and V₂O₅ through all corneal layers and into the iris stroma. Considering the marked epithelial toxicity and corneal penetration of ZnO, further investigations on the impact of this ENM on the eye are warranted.

Beyond N and P: The impact of Ni on crude oil biodegradation

N and P are the key limiting nutrients considered most important for the stimulation of crude oil degradation but other trace nutrients may also be important. Experimental soil microcosms were setup to investigate crude oil degradation in the context of Ni amendments. Amended Nickel as NiO, NiCl₂, or, a porphyrin complex either inhibited, had no effect, or, enhanced aerobic hydrocarbon degradation in an oil-contaminated soil. Biodegradation was significantly (95% confidence) enhanced (70%) with low levels of Ni-Porph (12 mg/kg) relative to an oil-only control; whereas, NiO (200 and 350 mg/kg) significantly inhibited (36 and 87%) biodegradation consistent with oxide particle induced reactive oxygen stress. Microbial community compositions were also significantly affected by Ni. In 16S rRNA sequence libraries, the enriched hydrocarbon degrading genus, Rhodococcus, was partially replaced by a Nocardia sp. in the presence of low levels of NiO (12 and 50 mg/kg). In contrast, the highest relative and absolute Rhodococcus abundances were coincident with the maximal rates of oil degradation observed in the Ni-Porph-amended soils. Growth dependent constitutive requirements for Ni-dependent urease or perhaps Ni-dependent superoxide dismutase enzymes (found in Rhodococcus genomes) provided a mechanistic explanation for stimulation. These results suggest biostimulation technologies, in addition to N and P, should also consider trace nutrients such as Ni tacitly considered adequately supplied and available in a typical soil.

The mechanism-based toxicity screening of particles with use in the food and nutrition sector via the ToxTracker reporter system

The rapid expansion of the incorporation of nano-sized materials in consumer products overlaps with the necessity for high-throughput reliable screening tools for the identification of the potential hazardous properties of the nanomaterials. The ToxTracker assay (mechanism-based reporter assay based on embryonic stem cells that uses GFP-tagged biomarkers for detection of DNA damage, oxidative stress and general cellular stress) is one such tool, which could prove useful in the field of particle toxicology allowing for high throughput screening. Here, ToxTracker was utilised to evaluate the potential hazardous properties of two particulates currently used in the food industry (vegetable carbon (E153) and food-grade TiO₂ (E171)). Due to the fact that ToxTracker is based on a stem cell format, it is crucial that the data generated is assessed for its suitability and comparability to more conventionally used relevant source of cells - in this case cells from the gastrointestinal tract and the liver. Therefore, the cell reporter findings were compared to data from traditional assays (cytotoxicity, anti-oxidant depletion and DNA damage) and tissue relevant cell types. The data showed E171 to be the most cytotoxic, decreased intracellular glutathione and the most significant with regards to genotoxic effects. The ToxTracker data showed comparability to conventional toxicity and oxidative stress assays; however, some discrepancies were evident between the findings from ToxTracker and the comet assay.

Grouping of Poorly Soluble Low (Cyto)Toxic Particles: Example with 15 Selected Nanoparticles and A549 Human Lung Cells

Poorly soluble, low (cyto)toxic particles (PSLTs) are often regarded as one group, but it is important that these particles can be further differentiated based on their bioactivity. Currently, there are no biological endpoint based groupings for inhaled nanoparticles (NPs) that would allow us to subgroup PSLTs based on their mode of action. The aim of this study was to group NPs based on their cytotoxicity and by using the in vitro response of the endo-lysosomal system as a biological endpoint. The endo-lysosomal system is a main cellular loading site for NPs. An impaired endo-lysosomal system in alveolar type II cells may have serious adverse effects on the maintenance of pulmonary surfactant homeostasis. The 15 different NPs were tested with human lung adenocarcinoma (A549) cells. The highly soluble NPs were most cytotoxic. With respect to PSLTs, only three NPs increased the cellular load of acid and phospholipid rich organelles indicating particle biopersistence. All the rest PSLTs could be regarded as low hazardous. The presented in vitro test system could serve as a fast screening tool to group particles according to their ability to interfere with lung surfactant metabolism. We discuss the applicability of the suggested test system for bringing together substances with similar modes-of-action on lung epithelium. In addition, we discuss this approach as a benchmark test for the comparative assessment of biopersistence of PSLTs.

Preparation, characterizations and in vitro cytotoxic activity of nickel oxide nanoparticles on HT-29 and SW620 colon cancer cell lines

Despite the extensive implication of nickel oxide nanoparticles (NiO-NPs) in different fields such as biomedical science and industrial manufacturing, their effect on human cancer cells has not been elucidated. In this study, we report a simple process for the preparation of NiO-NPs. X-ray diffraction and transmission electron microscopy were used to characterize the surface architecture and dimension of the synthesized NiO-NPs. The average diameter of the NiO-NPs was approximately 20-25 nm. We used two human colon cancer cell lines, HT-29 and SW620, to assess the nanoparticles' cytotoxicity. The MTT assay showed that the NiO-NPs reduced cell viability of HT-29 and SW620 cell lines. The results of inverted microscopy showed the highest cytotoxic activity with 600 μg/ml concentration of NiO-NPs on HT-29 cells. Western blot assay showed the downregulation of anti-apoptotic Bcl2 and Bcl-xL proteins in HT-29 cells treated with NiO-NPs. Moreover the results demonstrated the induction of PARP (Cleaved) in NiO-NPs treated HT-29 cells which are considered the marker of apoptosis. The NiO-NPs were not demonstrated bactericidal effect on six different bacterial strains tested, implying that the NiO-NPs may not perturb the human normal gut microbiome. The results have showed the promising application of the NiO-NPs in management of cancer in near future.

Cytotoxicity and genotoxicity of cerium oxide micro and nanoparticles by Allium and Comet tests

Cerium oxide (CeO₂) is extensively used in a range of applications like in television tubes, glass/ceramic polishing agent, fuel cells, solar cells, gas sensor andultraviolet absorbents. In current study, Allium ana-telophase and comet assays were employed to evaluate the cytotoxic and genotoxic effects of CeO₂ microparticles (CMPs, <5 µm, bulk) and CeO₂ nanoparticles (CNPs, < 25 nm) on the root meristem cells of Allium cepa by using mitotic phases, mitotic index (MI), chromosomal aberrations (CAs), and DNA damage. A cepa roots were treated with the CMPs and CNPs at four different concentrations (12.5, 25, 50, and 100 ppm) for 4 h. Methyl methane sulphonate (MMS,10 ppm) and distilled water were used as positive and negative control groups, respectively. All the applied doses statistically decreased MIs. MI values of CMPs were found higher than CNPs. CMPs and CNPs significantly increased CAs such as chromosome laggards, disturbed anaphase-telophase, stickiness and bridges and also DNA damage. Characterization of CMPs and CNPs showed the particle size as 4.24 ± 0.7 µm and 20.28 ± 2.33 nm, respectively. The average diameter of CMPs and CNPs in solution were in the range of 372.75 ± 70.23 nm and 167.74 ± 38.7 nm, respectively. These results demonstrated that CMPs and CNPs had cytotoxic and genotoxic effects in A. cepa root meristematic cells.

Toxic effects of nickel oxide (NiO) nanoparticles on the freshwater alga Pseudokirchneriella subcapitata

Over the last decade, concerns have been raised regarding the potential health and environmental effects associated with the release of metal oxide nanoparticles (NPs) into ecosystems. In the present work, the potential hazards of nickel oxide (NiO) NPs were investigated using the ecologically relevant freshwater alga Pseudokirchneriella subcapitata. NiO NP suspensions in algal OECD medium were characterized with regard to their physicochemical properties: agglomeration, surface charge, stability (dissolution of the NPs) and abiotic reactive oxygen species (ROS) production. NiO NPs formed loose agglomerates and released Ni²⁺. NiO NPs presented a 72 h-EC₅₀ of 1.6 mg L^-1, which was evaluated using the algal growth inhibition assay and allowed this NP to be classified as toxic. NiO NPs caused the loss of esterase activity (metabolic activity), the bleaching of photosynthetic pigments and the intracellular accumulation of reactive oxygen species (ROS) in the absence of the disruption of plasma membrane integrity. NiO NPs also disturbed the photosynthetic process. A reduction in the photosynthetic efficiency (Φ_PSII) accompanied by a decrease in the flow rate of electrons through the photosynthetic chain was also observed. The leakage of electrons from the photosynthetic chain may be the origin of the ROS found in the algal cells. The exposure to NiO NPs led to the arrest of the cell cycle prior to the first cell division (primary mitosis), an increase in cell volume and the presence of aberrant morphology in the algal cells. In this work, the use of different approaches allowed new clues related to the toxicity mechanisms of NiO NPs to be obtained. This work also contributes to the characterization of the environmental and toxicological hazards of NiO NPs and provides information on the possible adverse effects of these NPs on aquatic systems.

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.

A Current Overview of the Biological and Cellular Effects of Nanosilver

Nanosilver plays an important role in nanoscience and nanotechnology, and is becoming increasingly used for applications in nanomedicine. Nanosilver ranges from 1 to 100 nanometers in diameter. Smaller particles more readily enter cells and interact with the cellular components. The exposure dose, particle size, coating, and aggregation state of the nanosilver, as well as the cell type or organism on which it is tested, are all large determining factors on the effect and potential toxicity of nanosilver. A high exposure dose to nanosilver alters the cellular stress responses and initiates cascades of signalling that can eventually trigger organelle autophagy and apoptosis. This review summarizes the current knowledge of the effects of nanosilver on cellular metabolic function and response to stress. Both the causative effects of nanosilver on oxidative stress, endoplasmic reticulum stress, and hypoxic stress—as well as the effects of nanosilver on the responses to such stresses—are outlined. The interactions and effects of nanosilver on cellular uptake, oxidative stress (reactive oxygen species), inflammation, hypoxic response, mitochondrial function, endoplasmic reticulum (ER) function and the unfolded protein response, autophagy and apoptosis, angiogenesis, epigenetics, genotoxicity, and cancer development and tumorigenesis—as well as other pathway alterations—are examined in this review.

Genotoxicity induced by metal oxide nanoparticles: a weight of evidence study and effect of particle surface and electronic properties

The genetic toxicology of nanomaterials is a crucial toxicology issue and one of the least investigated topics. Substantially, the genotoxicity of metal oxide nanomaterials' data is resulting from in vitro comet assay. Current contributions to the genotoxicity data assessed by the comet assay provide a case-by-case evaluation of different types of metal oxides. The existing inconsistency in the literature regarding the genotoxicity testing data requires intelligent assessment strategies, such as weight of evidence evaluation. Two main tasks were performed in the present study. First, the genotoxicity data from comet assay for 16 noncoated metal oxide nanomaterials with different core composition were collected. An evaluation criterion was applied to establish which of these individual lines of evidence were of sufficient quality and what weight could have been given to them in inferring genotoxic results. The collected data were surveyed on (1) minimum necessary characterization points for nanomaterials and (2) principals of correct comet assay testing for nanomaterials. Second, in this study the genotoxicity effect of metal oxide nanomaterials was investigated by quantitative nanostructure-activity relationship approach. A set of quantum-chemical descriptors was developed for all investigated metal oxide nanomaterials. A classification model based on decision tree was developed for the investigated dataset. Thus, three descriptors were identified as the most responsible factors for genotoxicity effect: heat of formation, molecular weight, and surface area of the oxide cluster based on the conductor-like screening model. Conclusively, the proposed genotoxicity assessment strategy is useful to prioritize the study of the nanomaterials for further risk assessment evaluations.

Evaluation of the genotoxic properties of nickel oxide nanoparticles in vitro and in vivo

Nickel-based nanoparticles (NPs) are new products with an increasing number of industrial applications that were developed in recent years. NiO NPs are present in several nanotechnological industrial products, and the characterization of their genotoxic potential is essential. The present study assessed the genotoxicity of NiO NPs in vivo and in vitro using the somatic mutation and recombination test in somatic cells of Drosophila melanogaster (SMART), the cytokinesis - block micronucleus assay (CBMN), and the comet assay in a V79 cell line. The NiO NPs used in this study were about 30 nm in mean size. Larvae of Drosophila melanogaster were exposed to 5 mL of five different concentrations (1.31, 2.62, 5.25, 10.5, and 21 mg/mL) of NiO NPs. In turn, V79 cells were treated with a concentration range of 15-2000 μg/mL NiO NPs. The SMART showed that all concentrations of NiO NPs are genotoxic to the standart (ST) cross when compared to the negative control. On the other hand, only the highest concentration (21 mg/mL) was genotoxic to the HB cross. Somatic recombination was the preferential mechanism lesions were induced in D. melanogaster. The results show that NiO NPs were mutagenic to V79 cells as assessed by the CBMN assay. Significant differences in the frequencies of micronuclei (MN) were observed using the highest NiO NP concentrations (250 and 500 μg/mL) in the 4- and 24-h treatments, but when 125 μg/mL NiO NPs was used, such difference was observed only in the 4-h exposure time. The comet assay revealed that 62, 125, 250 and 500 μg/mL NiO NPs induced a significant increase in DNA damage. The results observed in this study indicate that NiO NPs are genotoxic and mutagenic in vitro and in vivo.

An updated review of the genotoxicity of respirable crystalline silica

Human exposure to (certain forms of) crystalline silica (CS) potentially results in adverse effects on human health. Since 1997 IARC has classified CS as a Group 1 carcinogen [1], which was confirmed in a later review in 2012 [2]. The genotoxic potential and mode of genotoxic action of CS was not conclusive in either of the IARC reviews, although a proposal for mode of actions was made in an extensive review of the genotoxicity of CS by Borm, Tran and Donaldson in 2011 [3]. The present study identified 141 new papers from search strings related to genotoxicity of respirable CS (RCS) since 2011 and, of these, 17 relevant publications with genotoxicity data were included in this detailed review.

Studies on in vitro genotoxic endpoints primarily included micronucleus (MN) frequency and % fragmented DNA as measured in the comet assay, and were mostly negative, apart from two studies using primary or cultured macrophages. In vivo studies confirmed the role of persistent inflammation due to quartz surface toxicity leading to anti-oxidant responses in mice and rats, but DNA damage was only seen in rats. The role of surface characteristics was strengthened by in vitro and in vivo studies using aluminium or hydrophobic treatment to quench the silanol groups on the CS surface.

In conclusion, the different modes of action of RCS-induced genotoxicity have been evaluated in a series of independent, adequate studies since 2011. Earlier conclusions on the role of inflammation driven by quartz surface in genotoxic and carcinogenic effects after inhalation are confirmed and findings support a practical threshold. Whereas classic in vitro genotoxicity studies confirm an earlier no-observed effect level (NOEL) in cell cultures of 60-70 μg/cm², transformation frequency in SHE cells suggests a lower threshold around 5 μg/cm². Both levels are only achieved in vivo at doses (2–4 mg) beyond in vivo doses (> 200 μg) that cause persistent inflammation and tissue remodelling in the rat lung.

Genotoxic and mutagenic properties of Ni and NiO nanoparticles investigated by comet assay, γ-H2AX staining, Hprt mutation assay and ToxTracker reporter cell lines

Nickel (Ni) compounds are classified as carcinogenic to humans but the underlying mechanisms are still poorly understood. Furthermore, effects related to nanoparticles (NPs) of Ni have not been fully elucidated. The aim of this study was to investigate genotoxicity and mutagenicity of Ni and NiO NPs and compare the effect to soluble Ni from NiCl2 . We employed different models; i.e., exposure of (1) human bronchial epithelial cells (HBEC) followed by DNA strand break analysis (comet assay and γ-H2AX staining); (2) six different mouse embryonic stem (mES) reporter cell lines (ToxTracker) that are constructed to exhibit fluorescence upon the induction of various pathways of relevance for (geno)toxicity and cancer; and (3) mES cells followed by mutagenicity testing (Hprt assay). The results showed increased DNA strand breaks (comet assay) for the NiO NPs and at higher doses also for the Ni NPs whereas no effects were observed for Ni ions/complexes from NiCl2 . By employing the reporter cell lines, oxidative stress was observed as the main toxic mechanism and protein unfolding occurred at cytotoxic doses for all three Ni-containing materials. Oxidative stress was also detected in the HBEC cells following NP-exposure. None of these materials induced the reporter related to direct DNA damage and stalled replication forks. A small but statistically significant increase in Hprt mutations was observed for NiO but only at one dose. We conclude that Ni and NiO NPs show more pronounced (geno)toxic effects compared to Ni ions/complexes, indicating more serious health concerns. Environ. Mol. Mutagen. 59:211-222, 2018. © 2017 The Authors Environmental and Molecular Mutagenesis published by Wiley Periodicals, Inc. on behalf of Environmental Mutagen Society.

Nickel oxide (NiO) nanoparticles disturb physiology and induce cell death in the yeast Saccharomyces cerevisiae

The increasing use of nanoparticles (NPs) has spurred concerns about their toxic effects. This work aimed to assess the potential hazards of nickel oxide (NiO) NPs using the yeast Saccharomyces cerevisiae as a cell model. Yeast cells exposed for 6 h to 100 mg/L NiO NPs presented reduced metabolic activity (esterase activity and FUN-1 dye processing) and enhanced accumulation of reactive oxygen species. NiO NPs induced the loss of cell viability in a dose-dependent manner. Study of the dissolution of NiO NPs in aqueous media, together with the toxicological data, suggests that the nickel released by the NPs cannot explain all the toxic effects observed in S. cerevisiae caused by the NPs. Transmission electron microscopy observations revealed that NiO NPs were adsorbed onto cell surface but did not enter into yeast cells. Isogenic mutants (cwp1∆ and cwp2∆) with increased cell wall porosity did not display enhanced susceptibility to NiO NPs compared to the wild type strain. Our results suggest that NiO NPs exert their toxic effect by an indirect mechanism. This work contributes to knowledge of the potential hazards of NiO NPs and to the elucidation of their mechanisms of toxic action.

Graphene oxide is degraded by neutrophils and the degradation products are non-genotoxic

Neutrophils were previously shown to digest oxidized carbon nanotubes through a myeloperoxidase (MPO)-dependent mechanism, and graphene oxide (GO) was found to undergo degradation when incubated with purified MPO, but there are no studies to date showing degradation of GO by neutrophils. Here we produced endotoxin-free GO by a modified Hummers' method and asked whether primary human neutrophils stimulated to produce neutrophil extracellular traps or activated to undergo degranulation are capable of digesting GO. Biodegradation was assessed using a range of techniques including Raman spectroscopy, transmission electron microscopy, atomic force microscopy, and mass spectrometry. GO sheets of differing lateral dimensions were effectively degraded by neutrophils. As the degradation products could have toxicological implications, we also evaluated the impact of degraded GO on the bronchial epithelial cell line BEAS-2B. MPO-degraded GO was found to be non-cytotoxic and did not elicit any DNA damage. Taken together, these studies have shown that neutrophils can digest GO and that the biodegraded GO is non-toxic for human lung cells.

Silver Nanoparticles in the Lung: Toxic Effects and Focal Accumulation of Silver in Remote Organs

The distribution of silver (Ag) into remote organs secondary to the application of Ag nanoparticles (Ag-NP) to the lung is still incompletely understood and was investigated in the rat with imaging methods. Dose-finding experiments were carried out with 50 nm- or 200 nm-sized polyvinyl pyrrolidine (PVP)-coated Ag-NP using alveolar macrophages in vitro and female rats, which received Ag-NP via intratracheal instillation. In the main study, we administered 37.5–300 µg per rat lung of the more toxic Ag50-PVP and assessed the broncho-alveolar lavage fluid (BALF) for inflammatory cells, total protein and fibronectin after three and 21 days. In parallel, lung tissue was analysed for DNA double-strand breaks and altered cell proliferation. While 75–150 µg Ag50-PVP per rat lung caused a reversible inflammation, 300 µg led to DNA damage, accelerated cell proliferation and progressively increasing numbers of neutrophilic granulocytes. Ag accumulation was significant in homogenates of liver and other peripheral organs upon lung dose of ≥75 µg. Quantitative laser-ablation inductively-coupled plasma mass spectrometry (LA-ICP-MS) combined with enhanced dark field microscopy and autometallography revealed focal accumulations of Ag and/or Ag-NP in sections of peripheral organs: mediastinal lymph nodes contained Ag-NP especially in peripheral macrophages and Ag in argyrophilic fibres. In the kidney, Ag had accumulated within proximal tubuli, while renal filter structures contained no Ag. Discrete localizations were also observed in immune cells of liver and spleen. Overall, the study shows that concentrations of Ag-NP, which elicit a transient inflammation in the rat lung, lead to focal accumulations of Ag in peripheral organs, and this might pose a risk to particular cell populations in remote sites.

Role of oxidative stress in liver toxicity induced by nickel oxide nanoparticles in rats

The aim of the present study was to explore the role of oxidative stress in liver toxicity induced by nickel oxide nanoparticles (nano‑NiO) in rats. Male Wistar rats received saline (control), nano‑NiO [0.015, 0.06 or 0.24 mg/kg body weight (b.w.)] or micro‑NiO (0.24 mg/kg b.w.) by intratracheal instilling twice a week for 6 weeks. Liver tissues were then collected and examined for biomarkers of nitrative and oxidative stress, as well as mRNA expression of heme oxygenase (HO)‑1 and metallothionein (MT)‑1. The results demonstrated that the NiO exposure groups had increased liver wet weight and coefficient to body weight, as well as liver pathological changes, evidenced as cellular edema, hepatic sinus disappeara-nce and binucleated hepatocytes. The activities of total nitric oxide synthase and inducible nitric oxide synthase, and the nitric oxide content, were increased in the 0.24 mg/kg nano‑NiO group compared with the control group. The MT‑1 mRNA expression levels were downregulated, while HO‑1 mRNA was upregulated in the 0.24 mg/kg nano‑NiO exposure group compared with the control group. In addition, abnormal changes of hydroxyl radical, lipid peroxidation, catalase, glutathione peroxidase, total superoxide dismutase and total antioxidative capacity were observed in the liver tissues of the 0.24 mg/kg nano‑NiO exposure group, compared with the control group. The present results therefore indicated that nano‑NiO‑induced liver toxicity may be associated with nitrative and oxidative stress in rats.

Label-free and dynamic monitoring of cytotoxicity to the blood-brain barrier cells treated with nanometre copper oxide

A cytotoxicity study was conducted with a primary culture of the nervous system cells, including brain microvascular endothelial cells (BMECs) and astrocytes, which are important components of the blood-brain barrier. The real-time cell analysis (RTCA) was used to determine the cytotoxicity of copper-oxide nanoparticles (CuO NPs). The IC50 values of CuO NPs in astrocytes and BMECs were determined by the RTCA at different exposure times and were used as base values for further research. DNA damage after exposure to CuO NPs for 3 and 24 h was assessed using comet assay at the IC50 obtained from RTCA. The onset time of cytotoxicity induced by CuO NPs was 2 and 2-4 h post-exposure in BMECs and astrocytes, respectively. Furthermore, the degree of cytotoxicity induced by exposure to CuO NPs for 24-48 h in the BMECs and astrocytes was similar. Treatment with CuO NPs at 1/2*IC50 and 1/5*IC50 for 3 h induced genotoxicity in both cells as assessed by a measurement of DNA damage, although no cytotoxicity was observed. However, significant DNA damage was observed at all concentrations of CuO NPs used in this study, when the treatment time was 24 h.

Cobalt nanoparticles induce lung injury, DNA damage and mutations in mice

BACKGROUND

We and other groups have demonstrated that exposure to cobalt nanoparticles (Nano-Co) caused oxidative stress and inflammation, which have been shown to be strongly associated with genotoxic and carcinogenic effects. However, few studies have reported Nano-Co-induced genotoxic effects in vivo. Here, we propose that Nano-Co may have high genotoxic effects due to their small size and high surface area, which have high capacity for causing oxidative stress and inflammation.

METHODS

gpt delta transgenic mice were used as our in vivo study model. They were intratracheally instilled with 50 μg per mouse of Nano-Co. At day 1, 3, 7 and 28 after exposure, bronchoalveolar lavage (BAL) was performed and the number of neutrophils, CXCL1/KC level, LDH activity and concentration of total protein in the BAL fluid (BALF) were determined. Mouse lung tissues were collected for H&E staining, and Ki-67, PCNA and γ-H2AX immunohistochemical staining. 8-OHdG level in the genomic DNA of mouse lungs was determined by an OxiSelect™ Oxidative DNA Damage ELISA Kit, and mutant frequency and mutation spectrum in the gpt gene were also determined in mouse lungs at four months after Nano-Co exposure by 6-TG selection, colony PCR, and DNA sequencing.

RESULTS

Exposure of mice to Nano-Co (50 μg per mouse) resulted in extensive acute lung inflammation and lung injury which were reflected by increased number of neutrophils, CXCL1/KC level, LDH activity and concentration of total protein in the BALF, and infiltration of large amount of neutrophils and macrophages in the alveolar space and interstitial tissues. Increased immunostaining of cell proliferation markers, Ki-67 and PCNA, and the DNA damage marker, γ-H2AX, was also observed in bronchiolar epithelial cells and hyperplastic type II pneumocytes in mouse lungs at day 7 after Nano-Co exposure. At four months after exposure, extensive interstitial fibrosis and proliferation of interstitial cells with inflammatory cells infiltrating the alveolar septa were observed. Moreover, Nano-Co caused increased level of 8-OHdG in genomic DNA of mouse lung tissues. Nano-Co also induced a much higher mutant frequency as compared to controls, and the most common mutation was G:C to T:A transversion, which may be explained by Nano-Co-induced increased formation of 8-OHdG.

CONCLUSION

Our study demonstrated that exposure to Nano-Co caused oxidative stress, lung inflammation and injury, and cell proliferation, which further resulted in DNA damage and DNA mutation. These findings have important implications for understanding the potential health effects of nanoparticle exposure.

Cytotoxicity and genotoxicity of nanosilver in stable GADD45α promoter-driven luciferase reporter HepG2 and A549 cells

OBJECTIVES

The intense commercial application of silver nanoparticles (AgNPs) has been raising concerns about their potential adverse health effects to human. This study aimed to explore the potency of AgNPs to induce GADD45α gene, an important stress sensor, and its relationships with the cytotoxicity and genotoxicity elicited by AgNPs.

METHODS

Two established HepG2 and A549 cell lines containing the GADD45α promoter-driven luciferase reporter were treated with increasing concentrations of AgNPs for 48 hours. After the treatment, transcriptional activation of GADD45α indicated by luciferase activity, cell viability, cell cycle arrest, and levels of genotoxicity were determined. The uptake and intracellular localization of AgNPs, cellular Ag doses as well as Ag⁺ release were also detected.

RESULTS

AgNPs could activate GADD45α gene at the transcriptional level as demonstrated by the dose-dependent increases in luciferase activity in both the reporter cells. The relative luciferase activity was greater than 12× the control level in HepG2-luciferase cells at the highest concentration tested where the cell viability decreased to 17.0% of the control. These results was generally in accordance with the positive responses in cytotoxicity, cell cycle arrest of Sub G1 and G2/M phase, Olive tail moment, micronuclei frequency, and the cellular Ag content.

CONCLUSIONS

The cytotoxicity and genotoxicity of AgNPs seems to occur mainly via particles uptake and the subsequent liberation of ions inside the cells. And furthermore, the GADD45α promoter-driven luciferase reporter cells, especially the HepG2-luciferase cells, could provide a new and valuable tool for predicting nanomaterials genotoxicity in humans.

A Novel Exposure System Termed NAVETTA for In Vitro Laminar Flow Electrodeposition of Nanoaerosol and Evaluation of Immune Effects in Human Lung Reporter Cells

A new prototype air-liquid interface (ALI) exposure system, a flatbed aerosol exposure chamber termed NAVETTA, was developed to investigate deposition of engineered nanoparticles (NPs) on cultured human lung A549 cells directly from the gas phase. This device mimics human lung cell exposure to NPs due to a low horizontal gas flow combined with cells exposed at the ALI. Electrostatic field assistance is applied to improve NP deposition efficiency. As proof-of-principle, cell viability and immune responses after short-term exposure to nanocopper oxide (CuO)-aerosol were determined. We found that, due to the laminar aerosol flow and a specific orientation of inverted transwells, much higher deposition rates were obtained compared to the normal ALI setup. Cellular responses were monitored with postexposure incubation in submerged conditions, revealing CuO dissolution in a concentration-dependent manner. Cytotoxicity was the result of ionic and nonionic Cu fractions. Using the optimized inverted ALI/postincubation procedure, pro-inflammatory immune responses, in terms of interleukin (IL)-8 promoter and nuclear factor kappa B (NFκB) activity, were observed within short time, i.e. One hour exposure to ALI-deposited CuO-NPs and 2.5 h postincubation. NAVETTA is a novel option for mimicking human lung cell exposure to NPs, complementing existing ALI systems.

Green synthesis of silver nanoparticles using Anthemis atropatana extract: characterization and in vitro biological activities

This study aim to synthesize silver nanoparticles (AgNPs) using Anthemis atropatana extract and to evaluate their chemical characteristics and antimicrobial and cytotoxic effects. The biosynthesis of AgNPs is verified using UV-visible spectrum which showing maximum absorption in 430 nm wavelength. Transmission electron microscope (TEM) and scanning electron microscope (SEM) results revealed that AgNPs has a spherical shape with an average size of 38.89 nanometres. The crystalline structure of green synthesized AgNPs in optimal conditions was confirmed by XRD analysis. The pattern of XRD peaks related to face-centred cubic (fcc) (111), (200), (220), (311) and (222) observed. Also, FTIR results verified the AgNPs synthesis using plant extract. In biological tests, the MTT results indicate the dose dependence of cytotoxic effects of AgNPs on colon cancer cell lines (HT29). The AgNPs had maximum cytotoxicity on HT29 cancer cell line at 100 μg/ml concentration, which were statistically significant comparing control cells (p < .001). Moreover, real time PCR and flow cytometry results confirmed the apoptotic effects of AgNPs. According to the results, it seems that the green synthesis of AgNPs is an eco-friendly and cost effective approach. This research provides insight into the development of new anticancer and antibacterial agents.

Development of dual-fluorescence cell-based biosensors for detecting the influence of environmental factors on nanoparticle toxicity

With the expanding use of engineered nanoparticles (NPs), development of a high-throughput, sensitive method for evaluating NP safety is important. In this study, we developed cell-based biosensors to efficiently and conveniently monitor NP toxicity. The biosensor cells were obtained by transiently transfecting human cells with biosensor plasmids containing a mCherry gene regulated by an inducible promoter [an activator protein 1 (AP-1) promoter, an interleukin 8 (IL8) promoter, or a B cell translocation gene 2 (BTG2) promoter], with an enhanced green-fluorescent protein gene driven by the cytomegalovirus promoter as the internal control. After optimizing flow cytometric analysis, these dual-fluorescence cell-based biosensors were capable of accurately and rapidly detecting NP toxicity. We found that the responses of AP-1, BTG2, and IL8 biosensors in assessing the toxicity of silver nanoparticles (Ag NPs) showed good dose-related increases after exposure to Ag NPs and were consistent with data acquired by conventional assays, such as western blot, real-time polymerase chain reaction, and immunofluorescence. Further investigation of the effects of environmental factors on Ag NP toxicity revealed that aging in water, co-exposure with fulvic acid, and irradiation with ultraviolet A light could affect Ag NP-induced biosensor responses. These results indicated that these novel dual-fluorescence biosensors can be applied to accurately and sensitively monitor NP toxicity.

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.