An in vitro liver model--assessing oxidative stress and genotoxicity following exposure of hepatocytes to a panel of engineered nanomaterials

Hepatotoxicity of titanium dioxide nanoparticles

The food additive E171 (titanium dioxide, TiO2), is widely used in foods, pharmaceuticals and cosmetics. It is a fine white powder, with at least one third of its particles sized in the nanoparticulate (˂100 nm range, TiO2 NPs). The use of E171 is controversial as its relevant risk assessment has never been satisfactorily accomplished. In vitro and in vivo studies have shown dose-dependent toxicity in various organs including the liver. TiO2 NPs have been shown to induce inflammation, cell death and structural and functional changes within the liver. The toxicity of TiO2 NPs in experimental models varies between organs and according to their physiochemical characteristics and parameters such as dosage and route of administration. Among these factors, ingestion is the most significant exposure route, and the liver is a key target organ. The aim of this review is to highlight the reported adverse effects of orally administered TiO2 NPs on the liver and to discuss the controversial state of its toxicity.

New methodological developments for testing the in vitro genotoxicity of nanomaterials: Comparison of 2D and 3D HepaRG liver cell models and classical and high throughput comet assay formats

Nanomaterials (NMs) are defined as materials with at least one external dimension below 100 nm. Their small size confers them interesting unique physico-chemical properties, hence NMs are increasingly used in a diversity of applications. However, the specific properties of NMs could also make them more harmful than their bulk counterparts. Therefore, there is a crucial need to deliver efficient NM hazard assessment in order to sustain the responsible development of nanotechnology. This study analysed the genotoxic potential of several NMs: one titanium dioxide (TiO2) and two zinc oxide NMs (ZnO) that were tested up to 100 μg/mL on 2D and 3D hepatic HepaRG models. Genotoxicity analysis was performed comparing the alkaline comet assay in classical and high throughput formats. Moreover, oxidative DNA lesions were investigated with the Fpg-modified comet assay. Results showed that TiO2 NMs were not cytotoxic and not genotoxic in either cell model, although a small increase in the % tail DNA was observed in 3D HepaRG cells at 100 μg/mL in the classical format. The two ZnO NMs (ZnO S. NMs a commercial suspension and NM110 provided by the European Union Joint Research Centre) induced a concentration-dependent increase in cytotoxicity that was more pronounced in the 2D (>20% cytotoxicity was observed for ZnO S. at concentrations greater than 25 μg/mL, and for NM 110 at 50 μg/mL) than in the 3D model (more than 20% cytotoxicity for ZnO S. NMs at 50 μg/mL). While ZnO S. NMs induced DNA damage associated with cytotoxicity (at 25 and 50 μg/mL in 2D and 50 μg/mL in 3D), NM110 showed a clear genotoxic effect at non-cytotoxic concentrations (25 μg/mL in 2D and at 25 and 50 μg/mL in 3D). No major differences could be observed in the comet assay in the presence or absence of the Fpg enzyme. High throughput analysis using CometChip® mostly confirmed the results obtained with the classical format, and even enhanced the detection of genotoxicity in the 3D model. In conclusion, this study demonstrated that new approach methodologies (NAMs), 3D models and the high throughput format for the comet assay, were more efficient in the detection of genotoxic effects, and are therefore promising approaches to improve hazard assessment of NMs.

Cellular and Molecular Activities of IP6 in Disease Prevention and Therapy

IP6 (phytic acid) is a naturally occurring compound in plant seeds and grains. It is a poly-phosphorylated inositol derivative that has been shown to exhibit many biological activities that accrue benefits in health and diseases (cancer, diabetes, renal lithiasis, cardiovascular diseases, etc.). IP6 has been shown to have several cellular and molecular activities associated with its potential role in disease prevention. These activities include anti-oxidant properties, chelation of metal ions, inhibition of inflammation, modulation of cell signaling pathways, and modulation of the activities of enzymes and hormones that are involved in carbohydrate and lipid metabolism. Studies have shown that IP6 has anti-oxidant properties and can scavenge free radicals known to cause cellular damage and contribute to the development of chronic diseases such as cancers and cardiovascular diseases, as well as diabetes mellitus. It has also been shown to possess anti-inflammatory properties that may modulate immune responses geared towards the prevention of inflammatory conditions. Moreover, IP6 exhibits anti-cancer properties through the induction of cell cycle arrest, promoting apoptosis and inhibiting cancer cell growth. Additionally, it has been shown to have anti-mutagenic properties, which reduce the risk of malignancies by preventing DNA damage and mutations. IP6 has also been reported to have a potential role in bone health. It inhibits bone resorption and promotes bone formation, which may help in the prevention of bone diseases such as osteoporosis. Overall, IP6's cellular and molecular activities make it a promising candidate for disease prevention. As reported in many studies, its anti-inflammatory, anti-oxidant, and anti-cancer properties support its inclusion as a dietary supplement that may protect against the development of chronic diseases. However, further studies are needed to understand the mechanisms of action of this dynamic molecule and its derivatives and determine the optimal doses and appropriate delivery methods for effective therapeutic use.

Oxidative stress-related canonical pyroptosis pathway, as a target of liver toxicity triggered by zinc oxide nanoparticles

Zinc oxide nanoparticles (ZnO NPs) have been widely used in the fields of daily necessities, clinical diagnosis, drug delivery and agricultural production. The improper use of ZnO NPs could pose a risk to ecological environment and public health. Liver has been known as a critical toxic target of ZnO NPs. However, the question whether ZnO NPs lead to hepatocyte death through pyroptosis has not been answered yet, and the effect of oxidative stress on ZnO NPs-induced pyroptosis remains a mystery. We revealed that ZnO NPs disrupted zinc homeostasis and induced oxidative stress impairment in rat liver. Meanwhile, ZnO NPs triggered the assembly of NLRP3-ASC-Caspase-1 inflammatory complex and pyroptosis in both rat liver and HepG2 cells, further causing the activation of GSDMD, promoting the leakage of inflammatory cytokines including IL-1β and IL-18. Importantly, the inhibition of oxidative stress was found to provide protection against pyroptosis in hepatocyte exposed to ZnO NPs. We identified a novel mechanism of liver damage induced by ZnO NPs, demonstrating the activation of canonical Caspase-1-dependent pyroptosis pathway and clarifying the protection of antioxidation against pyroptosis damage. Our discovery provided a support for risk assessment of ZnO NPs and target exploration for clinical treatment related to pyroptosis.

Grouping of orally ingested silica nanomaterials via use of an integrated approach to testing and assessment to streamline risk assessment

BACKGROUND

Nanomaterials can exist in different nanoforms (NFs). Their grouping may be supported by the formulation of hypotheses which can be interrogated via integrated approaches to testing and assessment (IATA). IATAs are decision trees that guide the user through tiered testing strategies (TTS) to collect the required evidence needed to accept or reject a grouping hypothesis. In the present paper, we investigated the applicability of IATAs for ingested NFs using a case study that includes different silicon dioxide, SiO₂ NFs. Two oral grouping hypotheses addressing local and systemic toxicity were identified relevant for the grouping of these NFs and verified through the application of oral IATAs. Following different Tier 1 and/or Tier 2 in vitro methods of the TTS (i.e., in vitro dissolution, barrier integrity and inflammation assays), we generated the NF datasets. Furthermore, similarity algorithms (e.g., Bayesian method and Cluster analysis) were utilized to identify similarities among the NFs and establish a provisional group(s). The grouping based on Tier 1 and/or Tier 2 testing was analyzed in relation to available Tier 3 in vivo data in order to verify if the read-across was possible and therefore support a grouping decision.

RESULTS

The measurement of the dissolution rate of the silica NFs in the oro-gastrointestinal tract and in the lysosome identified them as gradually dissolving and biopersistent NFs. For the local toxicity to intestinal epithelium (e.g. cytotoxicity, membrane integrity and inflammation), the biological results of the gastrointestinal tract models indicate that all of the silica NFs were similar with respect to the lack of local toxicity and, therefore, belong to the same group; in vivo data (although limited) confirmed the lack of local toxicity of NFs. For systemic toxicity, Tier 1 data did not identify similarity across the NFs, with results across different decision nodes being inconsistent in providing homogeneous group(s). Moreover, the available Tier 3 in vivo data were also insufficient to support decisions based upon the obtained in vitro results and relating to the toxicity of the tested NFs.

CONCLUSIONS

The information generated by the tested oral IATAs can be effectively used for similarity assessment to support a grouping decision upon the application of a hypothesis related to toxicity in the gastrointestinal tract. The IATAs facilitated a structured data analysis and, by means of the expert's interpretation, supported read-across with the available in vivo data. The IATAs also supported the users in decision making, for example, reducing the testing when the grouping was well supported by the evidence and/or moving forward to advanced testing (e.g., the use of more suitable cellular models or chronic exposure) to improve the confidence level of the data and obtain more focused information.

Assessing the transferability and reproducibility of 3D in vitro liver models from primary human multi-cellular microtissues to cell-line based HepG2 spheroids

To reduce, replace, and refine in vivo testing, there is increasing emphasis on the development of more physiologically relevant in vitro test systems to improve the reliability of non-animal-based methods for hazard assessment. When developing new approach methodologies, it is important to standardize the protocols and demonstrate the methods can be reproduced by multiple laboratories. The aim of this study was to assess the transferability and reproducibility of two advanced in vitro liver models, the Primary Human multicellular microtissue liver model (PHH) and the 3D HepG2 Spheroid Model, for nanomaterial (NM) and chemical hazard assessment purposes. The PHH model inter-laboratory trial showed strong consistency across the testing sites. All laboratories evaluated cytokine release and cytotoxicity following exposure to titanium dioxide (TiO₂) and zinc oxide (ZnO) nanoparticles. No significant difference was observed in cytotoxicity or IL-8 release for the test materials. The data were reproducible with all three laboratories with control readouts within a similar range. The PHH model ZnO induced the greatest cytotoxicity response at 50.0 μg/mL and a dose-dependent increase in IL-8 release. For the 3D HepG2 spheroid model, all test sites were able to construct the model and demonstrated good concordance in IL-8 cytokine release and genotoxicity data. This trial demonstrates the successful transfer of new approach methodologies across multiple laboratories, with good reproducibility for several hazard endpoints.

Adverse Outcome Pathways Associated with the Ingestion of Titanium Dioxide Nanoparticles-A Systematic Review

Titanium dioxide nanoparticles (TiO₂-NPs) are widely used, and humans are exposed through food (E171), cosmetics (e.g., toothpaste), and pharmaceuticals. The oral and gastrointestinal (GIT) tract are the first contact sites, but it may be systemically distributed. However, a robust adverse outcome pathway (AOP) has not been developed upon GIT exposure to TiO₂-NPs. The aim of this review was to provide an integrative analysis of the published data on cellular and molecular mechanisms triggered after the ingestion of TiO₂-NPs, proposing plausible AOPs that may drive policy decisions. A systematic review according to Prisma Methodology was performed in three databases of peer-reviewed literature: Pubmed, Scopus, and Web of Science. A total of 787 records were identified, screened in title/abstract, being 185 used for data extraction. The main endpoints identified were oxidative stress, cytotoxicity/apoptosis/cell death, inflammation, cellular and systemic uptake, genotoxicity, and carcinogenicity. From the results, AOPs were proposed where colorectal cancer, liver injury, reproductive toxicity, cardiac and kidney damage, as well as hematological effects stand out as possible adverse outcomes. The recent transgenerational studies also point to concerns with regard to population effects. Overall, the findings further support a limitation of the use of TiO₂-NPs in food, announced by the European Food Safety Authority (EFSA).

Chronic effects of two rutile TiO2 nanomaterials in human intestinal and hepatic cell lines

Background

TiO₂ nanomaterials (NMs) are present in a variety of food and personal hygiene products, and consumers are exposed daily to these NMs through oral exposition. While the bulk of ingested TiO₂ NMs are eliminated rapidly in stool, a fraction is able to cross the intestinal epithelial barrier and enter systemic circulation from where NMs can be distributed to tissues, primarily liver and spleen. Daily exposure to TiO₂ NMs, in combination with a slow rate of elimination from tissues, results in their accumulation within different tissues. Considerable evidence suggests that following oral exposure to TiO₂ NMs, the presence of NMs in tissues is associated with a number of adverse effects, both in intestine and liver. Although numerous studies have been performed in vitro investigating the acute effects of TiO₂ NMs in intestinal and hepatic cell models, considerably less is known about the effect of repeated exposure on these models. In this study, we investigated the cytotoxic effects of repeated exposure of relevant models of intestine and liver to two TiO₂ NMs differing in hydrophobicity for 24 h, 1 week and 2 weeks at concentrations ranging from 0.3 to 80 µg/cm². To study the persistence of these two NMs in cells, we included a 1-week recovery period following 24 h and 1-week treatments. Cellular uptake by TEM and ToF–SIMS analyses, as well as the viability and pro-inflammatory response were evaluated. Changes in the membrane composition in Caco-2 and HepaRG cells treated with TiO₂ NMs for up to 2 weeks were also studied.

Results

Despite the uptake of NM-103 and NM-104 in cells, no significant cytotoxic effects were observed in either Caco-2 or HepaRG cells treated for up to 2 weeks at NM concentrations up to 80 µg/cm²_. In addition, no significant effects on IL-8 secretion were observed. However, significant changes in membrane composition were observed in both cell lines. Interestingly, while most of these phospholipid modifications were reversed following a 1-week recovery, others were not affected by the recovery period.

Conclusion

These findings indicate that although no clear effects on cytotoxicity were observed following repeated exposure of differentiated Caco-2 and HepaRG cells to TiO₂ NMs, subtle effects on membrane composition could induce potential adverse effects in the long-term.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12989-022-00470-1.

Three-dimensional (3D) liver cell models - a tool for bridging the gap between animal studies and clinical trials when screening liver accumulation and toxicity of nanobiomaterials

Despite the exciting properties and wide-reaching applications of nanobiomaterials (NBMs) in human health and medicine, their translation from bench to bedside is slow, with a predominant issue being liver accumulation and toxicity following systemic administration. In vitro 2D cell-based assays and in vivo testing are the most popular and widely used methods for assessing liver toxicity at pre-clinical stages; however, these fall short in predicting toxicity for NBMs. Focusing on in vitro and in vivo assessment, the accurate prediction of human-specific hepatotoxicity is still a significant challenge to researchers. This review describes the relationship between NBMs and the liver, and the methods for assessing toxicity, focusing on the limitations they bring in the assessment of NBM hepatotoxicity as one of the reasons defining the poor translation for NBMs. We will then present some of the most recent advances towards the development of more biologically relevant in vitro liver methods based on tissue-mimetic 3D cell models and how these could facilitate the translation of NBMs going forward. Finally, we also discuss the low public acceptance and limited uptake of tissue-mimetic 3D models in pre-clinical assessment, despite the demonstrated technical and ethical advantages associated with them.

Damaging effects of TiO2 nanoparticles on the ovarian cells of Bombyx mori

As a new type of biologically compatible material, TiO₂ NPs are widely used in the industry as additives, drug carriers, and components of skin care products. Due to their wide use, residual TiO₂ NPs in the environment are a safety concern that has attracted extensive attention. In this study, the ovarian cell line BmN of the model organism Bombyx mori was used to reveal the damaging effects of TiO₂ NPs exposure. The results demonstrated that TiO₂ NPs exhibited a dose-dependent effect on the relative cell viability, with significant toxic effects being observed above 20 mg/L. Oxidative damage analysis showed that ROS accumulated significantly in BmN cells after exposure to TiO₂ NPs (P ≤ 0.05) and induced DNA damage. Further analysis revealed that the transcriptional levels of key superoxide dismutase genes (SOD) decreased significantly, while the transcriptions of key genes of the MAPK/NF-κB signaling pathway (P38, MEK, ERK and REL) and the downstream inflammatory factor genes (IL6 and TNFSF5) were all significantly up-regulated (P ≤ 0.05). Overall, our results indicate that exposure to TiO₂ NPs leads to reduced transcription of antioxidant genes, accumulation of peroxides, and inflammation. These findings provide valuable data for the safety evaluation of environmental residues of TiO₂ NPs.

An Integrated Approach to Testing and Assessment to Support Grouping and Read-Across of Nanomaterials After Inhalation Exposure

Introduction: Here, we describe the generation of hypotheses for grouping nanoforms (NFs) after inhalation exposure and the tailored Integrated Approaches to Testing and Assessment (IATA) with which each specific hypothesis can be tested. This is part of a state-of-the-art framework to support the hypothesis-driven grouping and read-across of NFs, as developed by the EU-funded Horizon 2020 project GRACIOUS.

Development of Grouping Hypotheses and IATA: Respirable NFs, depending on their physicochemical properties, may dissolve either in lung lining fluid or in acidic lysosomal fluid after uptake by cells. Alternatively, NFs may also persist in particulate form. Dissolution in the lung is, therefore, a decisive factor for the toxicokinetics of NFs. This has led to the development of four hypotheses, broadly grouping NFs as instantaneous, quickly, gradually, and very slowly dissolving NFs. For instantaneously dissolving NFs, hazard information can be derived by read-across from the ions. For quickly dissolving particles, as accumulation of particles is not expected, ion toxicity will drive the toxic profile. However, the particle aspect influences the location of the ion release. For gradually dissolving and very slowly dissolving NFs, particle-driven toxicity is of concern. These NFs may be grouped by their reactivity and inflammation potency. The hypotheses are substantiated by a tailored IATA, which describes the minimum information and laboratory assessments of NFs under investigation required to justify grouping.

Conclusion: The GRACIOUS hypotheses and tailored IATA for respiratory toxicity of inhaled NFs can be used to support decision making regarding Safe(r)-by-Design product development or adoption of precautionary measures to mitigate potential risks. It can also be used to support read-across of adverse effects such as pulmonary inflammation and subsequent downstream effects such as lung fibrosis and lung tumor formation after long-term exposure.

miR221 regulates cell migration by targeting annexin a1 expression in human mesothelial MeT-5A cells neoplastic-like transformed by multi-walled carbon nanotube

Background

Multi-walled carbon nanotube (MWCNT) is one of the most widely used manufactured nanomaterials, however, its potential harmful effect on human health is of great concern. Previously we have shown the acute and chronic exposure to MWCNT induced different responses in human mesothelial MeT-5A cells. In the current study, MeT-5A cells were continuously subjected to MWCNT exposure at 10 μg/cm² for 48 h per passage, up to a whole year, to further clarify the carcinogesis and its potential mechanisms of MWCNT.

Results

After one-year MWCNT treatment, MeT-5A cells exhibited neoplastic-like properties, including morphological changes, anchorage-independent growth, increased cell proliferation and cell migration. Further examination revealed the expression of microRNA 221 (miR221) was gradually decreased, while the annexin a1 expression was increased at both the mRNA and protein level during the exposure. Bioinformatic analysis indicated that annexin a1 is a target for miR221 regulation, and it was confirmed by transfecting cells with miR221 mimics, which resulted in the downregulation of annexin a1. Detailed analyses demonstrated miR221 was involved in the regulation of cell migration, e.g., downregulation of miR221 or overexpression of ANNEXIN A1, contributed to the increased cell migration. In contrast, overexpression of miR221 or downregulation of ANNEXIN A1 slowed cell migration.

Conclusions

Taken together, these results point to a neoplastic-transforming property of MWCNT, and the miR221-annexin a1 axis is involved in the regulation of cell migration in the transformed cells.

Supplementary Information

The online version contains supplementary material available at 10.1186/s41021-021-00209-y.

Genotoxicity of multi-walled carbon nanotube reference materials in mammalian cells and animals

Carbon nanotubes (CNTs) were the first nanomaterials to be evaluated by the International Agency for Research on Cancer (IARC). The categorization as possibly carcinogenic agent to humans was only applicable to multi-walled carbon nanotubes called MWCNT-7. Other types of CNTs were not classifiable because of missing data and it was not possible to pinpoint unique CNT characteristics that cause cancer. Importantly, the European Commission's Joint Research Centre (JRC) has established a repository of industrially manufactured nanomaterials that encompasses at least four well-characterized MWCNTs called NM-400 to NM-403 (original JRC code). This review summarizes the genotoxic effects of these JRC materials and MWCNT-7. The review consists of 36 publications with results on cell culture experiments (22 publications), animal models (9 publications) or both (5 publications). As compared to the publications in the IARC monograph on CNTs, the current database represents a significant increase as there is only an overlap of 8 publications. However, the results come mainly from cell cultures and/or measurements of DNA strand breaks by the comet assay and the micronucleus assay (82 out of 97 outcomes). A meta-analysis of cell culture studies on DNA strand breaks showed a genotoxic response by MWCNT-7, less consistent effect by NM-400 and NM-402, and least consistent effect by NM-401 and NM-403. Results from other in vitro tests indicate strongest evidence of genotoxicity for MWCNT-7. There are too few observations from animal models and humans to make general conclusions about genotoxicity.

Understanding the impact of more realistic low-dose, prolonged engineered nanomaterial exposure on genotoxicity using 3D models of the human liver

BACKGROUND

With the continued integration of engineered nanomaterials (ENMs) into everyday applications, it is important to understand their potential for inducing adverse human health effects. However, standard in vitro hazard characterisation approaches suffer limitations for evaluating ENM and so it is imperative to determine these potential hazards under more physiologically relevant and realistic exposure scenarios in target organ systems, to minimise the necessity for in vivo testing. The aim of this study was to determine if acute (24 h) and prolonged (120 h) exposures to five ENMs (TiO₂, ZnO, Ag, BaSO₄ and CeO₂) would have a significantly different toxicological outcome (cytotoxicity, (pro-)inflammatory and genotoxic response) upon 3D human HepG2 liver spheroids. In addition, this study evaluated whether a more realistic, prolonged fractionated and repeated ENM dosing regime induces a significantly different toxicity outcome in liver spheroids as compared to a single, bolus prolonged exposure.

RESULTS

Whilst it was found that the five ENMs did not impede liver functionality (e.g. albumin and urea production), induce cytotoxicity or an IL-8 (pro-)inflammatory response, all were found to cause significant genotoxicity following acute exposure. Most statistically significant genotoxic responses were not dose-dependent, with the exception of TiO₂. Interestingly, the DNA damage effects observed following acute exposures, were not mirrored in the prolonged exposures, where only 0.2-5.0 µg/mL of ZnO ENMs were found to elicit significant (p ≤ 0.05) genotoxicity. When fractionated, repeated exposure regimes were performed with the test ENMs, no significant (p ≥ 0.05) difference was observed when compared to the single, bolus exposure regime. There was < 5.0% cytotoxicity observed across all exposures, and the mean difference in IL-8 cytokine release and genotoxicity between exposure regimes was 3.425 pg/mL and 0.181%, respectively.

CONCLUSION

In conclusion, whilst there was no difference between a single, bolus or fractionated, repeated ENM prolonged exposure regimes upon the toxicological output of 3D HepG2 liver spheroids, there was a difference between acute and prolonged exposures. This study highlights the importance of evaluating more realistic ENM exposures, thereby providing a future in vitro approach to better support ENM hazard assessment in a routine and easily accessible manner.

Genotoxicity Evaluation of Titanium Dioxide Nanoparticles In Vitro: a Systematic Review of the Literature and Meta-analysis

With the wide use of titanium dioxide nanoparticles (TiO₂-NPs), the genotoxicity of TiO₂-NPs, which is a factor for safety assessment, has attracted people's attention. However, their genotoxic effects in vitro remain controversial due to inconsistent reports. Therefore, a systematic review was conducted followed by a meta-analysis to reveal whether TiO₂-NPs cause genotoxicity in vitro. A total of 59 studies were identified in this review through exhaustive database retrieval and exclusion. Meta-analysis results were presented based on different evaluation methods. The results showed that TiO₂-NP exposure considerably increased the percentage of DNA in tail and olive tail moment in comet assay. Gene mutation assay revealed that TiO₂-NPs could also induce gene mutation. However, TiO₂-NP exposure had no effect on micronucleus (MN) formation in the MN assay. Subgroup analysis showed that normal cells were more vulnerable to toxicity induced by TiO₂-NPs. Moreover, mixed form and small particles of TiO₂-NPs increased the percentage of DNA in tail. In addition, short-term exposure could detect more DNA damage. The size, coating, duration, and concentration of TiO₂-NPs influenced MN formation. This study presented that TiO₂-NP exposure could cause genotoxicity in vitro. The physicochemical properties of TiO₂-NPs and experimental protocols influence the genotoxic effects in vitro. Comet and gene mutation assays may be more sensitive to the detection of TiO₂-NP genotoxic effects.

Biosafety risk assessment of nanoparticles: Evidence from food case studies

Nanotechnology provides a wide range of benefits in the food industry in improving food tastes, textures, sensations, quality, shelf life, and food safety. Recently, potential adverse effects such as toxicity and safety concerns have been associated with the increasing use of engineered nanoparticles in food industry. Additionally, very limited information is known concerning the behavior, properties and effects of food nano-materials in the gastrointestinal tract. There is explores the current advances and provides insights of the potential risks of nanoparticles in the food industry. Specifically, characteristics of food nanoparticles and their absorption in the gastrointestinal tract, the effects of food nanoparticles against the gastrointestinal microflora, and the potential toxicity mechanisms in different organs and body systems are discussed. This review would provide references for further investigation of nano-materials toxicity effect in foods and their molecular mechanisms. It will help to develop safer foods and expand nano-materials applications in safe manner.

MSN, MWCNT and ZnO nanoparticle-induced CHO-K1 cell polarisation is linked to cytoskeleton ablation

BACKGROUND

The cellular response to nanoparticles (NPs) for the mechanical clue and biochemical changes are unexplored. Here, we provide the comprehensive analysis of the Chinese Hamster Ovary (CHO-K1) cell line to study cell behaviour following the exposure of mesoporous silica nanoparticle (MSN), multiwall carbon nanotubes (MWCNTs), and zinc oxide (ZnO) NPs.

RESULTS

Through the high-throughput proteomic study, we observed that the effect of NPs is alone not restricted to cell viability but also on cell polarisation. In the case of MSN, no drastic changes were observed in cellular morphology, but it upregulated chaperons that might prevent protein aggregation. However, MWCNT showed elongated cell appearance with numerous cytoplasmic vacuoles, and induce lamellipodia formation through actin polymerisation. The cytoskeleton remodelling was accompanied by the increased expression of Dlc-1, cofilin and Rac1 proteins. While ZnO NPs resulted in the rounded cell morphology along with nuclear abnormalities. The proteome analysis revealed that UBXN11 control cell roundness and DOCK3 leads to actin stress fibre formation and finally, loss of cell adhesion. It enhances the expression of catastrophic DNA damage and apoptotic proteins, which was unrecoverable even after 72 h, as confirmed by the colony formation assay. All three NPs trigger over-expression of the endocytic pathway, ubiquitination, and proteasomal complex proteins. The data indicate that ZnO and MSN entered into the cells through clathrin-mediated pathways; whereas, MWCNT invades through ER-mediated phagocytosis.

CONCLUSIONS

Based on the incubation and concentration of NPs, our work provides evidence for the activation of Rac-Rho signalling pathway to alter cytoskeleton dynamics. Our results assist as a sensitive early molecular readout for nanosafety assessment.

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.

Mechanistic Differences in Cell Death Responses to Metal-Based Engineered Nanomaterials in Kupffer Cells and Hepatocytes

The mononuclear phagocyte system in the liver is a frequent target for nanoparticles (NPs). A toxicological profiling of metal-based NPs is performed in Kupffer cell (KC) and hepatocyte cell lines. Sixteen NPs are provided by the Nanomaterial Health Implications Research Consortium of the National Institute of Environmental Health Sciences to study the toxicological effects in KUP5 (KC) and Hepa 1-6 cells. Five NPs (Ag, CuO, ZnO, SiO2 , and V2 O5 ) exhibit cytotoxicity in both cell types, while SiO2 and V2 O5 induce IL-1β production in KC. Ag, CuO, and ZnO induced caspase 3 generated apoptosis in both cell types is accompanied by ion shedding and generation of mitochondrial reactive oxygen species (ROS) in both cell types. However, the cell death response to SiO2 in KC differs by inducing pyroptosis as a result of potassium efflux, caspase 1 activation, NLRP3 inflammasome assembly, IL-1β release, and cleavage of gasdermin-D. This releases pore-performing peptide fragments responsible for pyroptotic cell swelling. Interestingly, although V2 O5 induces IL-1β release and delays caspase 1 activation by vanadium ion interference in membrane Na+ /K+ adenosine triphosphate (ATP)ase activity, the major cell death mechanism in KC (and Hepa 1-6) is caspase 3 mediated apoptosis. These findings improve the understanding of the mechanisms of metal-based engineered nanomaterial (ENM) toxicity in liver cells toward comprehensive safety evaluation.

An Integrated In Vitro-In Silico Approach for Silver Nanoparticle Dosimetry in Cell Cultures

Potential human and environmental hazards resulting from the exposure of living organisms to silver nanoparticles (Ag NPs) have been the subject of intensive discussion in the last decade. Despite the growing use of Ag NPs in biomedical applications, a quantification of the toxic effects as a function of the total silver mass reaching cells (namely, target cell dose) is still needed. To provide a more accurate dose-response analysis, we propose a novel integrated approach combining well-established computational and experimental methodologies. We first used a particokinetic model (ISD3) for providing experimental validation of computed Ag NP sedimentation in static-cuvette experiments. After validation, ISD3 was employed to predict the total mass of silver reaching human endothelial cells and hepatocytes cultured in 96 well plates. Cell viability measured after 24 h of culture was then related to this target cell dose. Our results show that the dose perceived by the cell monolayer after 24 h of exposure is around 85% lower than the administered nominal media concentration. Therefore, accurate dosimetry considering particle characteristics and experimental conditions (e.g., time, size and shape of wells) should be employed for better interpreting effects induced by the amount of silver reaching cells.

A unified in silico model based on perturbation theory for assessing the genotoxicity of metal oxide nanoparticles

Nanomaterials (NMs) are an ever-increasing field of interest, due to their wide range of applications in science and technology. However, despite providing solutions to many societal problems and challenges, NMs are associated with adverse effects with potential severe damages towards biological species and their ecosystems. Particularly, it has been confirmed that NMs may induce serious genotoxic effects on various biological targets. Given the difficulties of experimental assays for estimating the genotoxicity of many NMs on diverse biological targets, development of alternative methodologies is crucial to establish their level of safety. In silico modelling approaches, such as Quantitative Structure-Toxicity Relationships (QSTR), are now considered a promising solution for such purpose. In this work, a perturbation theory machine learning (PTML) based QSTR approach is proposed for predicting the genotoxicity of metal oxide NMs under various experimental assay conditions. The application of such perturbation approach to 6084 NM-NM pair cases, set up from 78 unique NMs, afforded a final PTML-QSTR model with an accuracy better than 96% for both training and test sets. This model was then used to predict the genotoxicity of some NMs not included in the modelling dataset. The results for this independent data set were in excellent agreement with the experimental ones. Overall, that thus suggests that the derived PTML-QSTR model is a reliable in silico tool to rapidly and cost-efficiently assess the genotoxicity of metal oxide NMs. Finally, and most importantly, the model provides important insights regarding the mechanism of the genotoxicity triggered by these NMs.

Influence of nanoparticles on liver tissue and hepatic functions: A review

Due to the increasing interest in nanotechnology in very large application fields, including biotechnology, electronics and food industries, humans are increasingly exposed to nanoparticles (NPs). Consequently, the question about the safety of these nanomaterials and their impact on human health is a legitimate concern. The liver is the primary organ of detoxification and is one of the tissues that is most exposed to NPs. When they reach the bloodstream, NPs are mainly internalized by liver cells. This review focuses on recent in vitro and in vivo studies addressing the effects of organic and inorganic NPs on the liver. Specifically, the impact of the NPs on hepatic enzyme activities, the inflammatory response and genotoxicity processes will be described. Depending on the physicochemical parameters of the NPs and the conditions of exposure, NPs could lead to global liver injury.

Application of ZnO-Based Nanocomposites for Vaccines and Cancer Immunotherapy

Engineering and application of nanomaterials have recently helped advance various biomedical fields. Zinc oxide (ZnO)-based nanocomposites have become one of the most promising candidates for biomedical applications due to their biocompatibility, unique physicochemical properties, and cost-effective mass production. In addition, recent advances in nano-engineering technologies enable the generation of ZnO nanocomposites with unique three-dimensional structures and surface characteristics that are optimally designed for in vivo applications. Here, we review recent advances in the application of diverse ZnO nanocomposites, with an especial focus on their development as vaccine adjuvant and cancer immunotherapeutics, as well as their intrinsic properties interacting with the immune system and potential toxic effect in vivo. Finally, we summarize promising proof-of-concept applications as prophylactic and therapeutic vaccines against infections and cancers. Understanding the nano-bio interfaces between ZnO-based nanocomposites and the immune system, together with bio-effective design of the nanomaterial using nano-architectonic technology, may open new avenues in expanding the biomedical application of ZnO nanocomposites as a novel vaccine platform.

Genotoxicity Assessment of Nanomaterials: Recommendations on Best Practices, Assays, and Methods

Nanomaterials (NMs) present unique challenges in safety evaluation. An international working group, the Genetic Toxicology Technical Committee of the International Life Sciences Institute's Health and Environmental Sciences Institute, has addressed issues related to the genotoxicity assessment of NMs. A critical review of published data has been followed by recommendations on methods alterations and best practices for the standard genotoxicity assays: bacterial reverse mutation (Ames); in vitro mammalian assays for mutations, chromosomal aberrations, micronucleus induction, or DNA strand breaks (comet); and in vivo assays for genetic damage (micronucleus, comet and transgenic mutation assays). The analysis found a great diversity of tests and systems used for in vitro assays; many did not meet criteria for a valid test, and/or did not use validated cells and methods in the Organization for Economic Co-operation and Development Test Guidelines, and so these results could not be interpreted. In vivo assays were less common but better performed. It was not possible to develop conclusions on test system agreement, NM activity, or mechanism of action. However, the limited responses observed for most NMs were consistent with indirect genotoxic effects, rather than direct interaction of NMs with DNA. We propose a revised genotoxicity test battery for NMs that includes in vitro mammalian cell mutagenicity and clastogenicity assessments; in vivo assessments would be added only if warranted by information on specific organ exposure or sequestration of NMs. The bacterial assays are generally uninformative for NMs due to limited particle uptake and possible lack of mechanistic relevance, and are thus omitted in our recommended test battery for NM assessment. Recommendations include NM characterization in the test medium, verification of uptake into target cells, and limited assay-specific methods alterations to avoid interference with uptake or endpoint analysis. These recommendations are summarized in a Roadmap guideline for testing.

The importance of inter-individual Kupffer cell variability in the governance of hepatic toxicity in a 3D primary human liver microtissue model

The potential for nanomaterial (NM) translocation to secondary organs is a realistic prospect, with the liver one of the most important target organs. Traditional in vitro or ex vivo hepatic toxicology models are often limiting and/or troublesome (i.e. short life-span reduced metabolic activity, lacking important cell populations, high inter-individual variability, etc.). Building on previous work, this study utilises a 3D human liver microtissue (MT) model (MT composed of mono-culture of hepatocytes or two different co-culture MT systems with non-parenchymal cell (NPC) fraction sourced from different donors) to investigate the importance of inter-donor variability of the non-parenchymal cell population in the overall governance of toxicological response following exposure to a panel of NMs. To the best of our knowledge, this is the first study of its kind to investigate inter-donor variability in hepatic NPC population. The data showed that the Kupffer cells were crucial in dictating the overall hepatic toxicity following exposure to the materials. Furthermore, a statistically significant difference was noted between the two co-culture MT models. However, the trend for particle-induced biological responses was similar between the co-cultures (cytotoxicity, cytokine production and caspase activity). Therefore, despite the recognition of some discrepancies in the absolute values between the co-culture models, the fact that the trends and patterns of biological responses were comparable between the multi-cellular models we propose the 3D liver MT to be a valuable tool in particle toxicology.

Nanomaterials induce DNA-protein crosslink and DNA oxidation: A mechanistic study with RTG-2 fish cell line and Comet assay modifications

Genotoxic effects of nanomaterials (NMs) have been controversially reported in literature, and the mode of action (MoA) via DNA oxidation is cited as the main damage caused by them. Evidence of nano-silver as a crosslinker has been previously reported by the present research team in an in vivo fish genotoxicity study. Thus, aiming to confirm the evidence about NMs as crosslinker agent, the present investigation elucidated the genotoxic potential of NMs and their genotoxic MoA through in vitro assay with RTG-2 cells line (rainbow trout gonadal) by exposure to nano-silver (PVP-coated) and nano-titanium. The types and levels of DNA damage were assessed by the Comet assay (standard alkaline, hOGG1-modified alkaline, and two crosslink-modified alkaline versions). It was demonstrated that the use of the standard alkaline Comet assay alone may inaccurately predict the genotoxicity of NMs since oxidative and crosslink DNA damages were also verified in RTG-2 cells when assessed by the modified versions of the alkaline protocol. More importantly, it was confirmed that both nano-silver and nano-titanium acted as DNA-protein crosslinkers through the Comet assay version with proteinase K. As both nano-silver and nano-titanium present a great risk to aquatic life, these findings reinforce the need of genotoxicity testing strategies that encompass the assessment of different types of DNA damage, in order to ensure an accurate prediction of the genotoxic potential of NMs.

Zinc Oxide Nanoparticle as a Novel Class of Antifungal Agents: Current Advances and Future Perspectives

Certain types of nanoparticles, especially zinc oxide nanoparticles (ZnONPs), are widely reported to be capable of the inhibition of harmful bacteria, yeasts, and filamentous fungi. The unique physicochemical and biological properties of ZnONPs also make them attractive to the food industry for use as a promising antifungal agent. This Review thoroughly introduces the preparation methods and antifungal properties of ZnONPs and analyzes their possible antifungal mechanisms. The applicability of ZnONPs in food packaging and nutritional supplements and as an antimicrobial additive is also documented. Moreover, evaluations for biological safety of ZnONPs are objectively reviewed in this paper. The discussions addressed in this Review not only have theoretical significance but also are conducive to the development of food safety, nutrition, and human health. The summarized knowledge and future perspectives outlined here are expected to promote and guide new research toward developing and optimizing the application of ZnONPs as a novel class of antifungal agents to help improve food quality as well as food safety in the near future.

Health Concerns of Various Nanoparticles: A Review of Their in Vitro and in Vivo Toxicity

Nanoparticles (NPs) are currently used in diagnosis and treatment of many human diseases, including autoimmune diseases and cancer. However, cytotoxic effects of NPs on normal cells and living organs is a severe limiting factor that hinders their use in clinic. In addition, diversity of NPs and their physico-chemical properties, including particle size, shape, surface area, dispersity and protein corona effects are considered as key factors that have a crucial impact on their safe or toxicological behaviors. Current studies on toxic effects of NPs are aimed to identify the targets and mechanisms of their side effects, with a focus on elucidating the patterns of NP transport, accumulation, degradation, and elimination, in both in vitro and in vitro models. NPs can enter the body through inhalation, skin and digestive routes. Consequently, there is a need for reliable information about effects of NPs on various organs in order to reveal their efficacy and impact on health. This review covers the existing knowledge base on the subject that hopefully prepares us better to address these challenges.

Hepatic Hazard Assessment of Silver Nanoparticle Exposure in Healthy and Chronically Alcohol Fed Mice

Silver (Ag) nanoparticles (NPs) are currently among one of the most widely used nanomaterials. This in turn, implies an increased risk of human and environmental exposure. Alcohol abuse is a global issue with millions of people in the general population affected by the associated adverse effects. The excessive consumption of alcohol is a prominent cause of chronic liver disease which manifest in multiple disorders. In this study, the adverse health effects of Ag NP exposure were investigated in models of alcoholic hepatic disease in vitro and in vivo. The data showed that Ag NP induced hepatic health effects were aggravated in the alcohol pretreated mice in comparison to controls with regards to an organ specific inflammatory response, changes in blood biochemistry, acute phase response and hepatic pathology. In addition, alcoholic disease influenced the organ's ability for recovery post-NP challenge. Additionally, it is demonstrated that the in vivo data correlated well with in vitro findings where ethanol pretreatment of hepatocytes resulted in significantly increased inflammatory response post-Ag NP exposure. To the best of our knowledge this is the first study of its kind to investigate nano-sized material-induced hepatic pathology in models representative of susceptible individuals (those with pre-existing alcohol liver disease) within the population. This is an area of research in the field of nanotoxicology, and in particular with regard to NP risk assessment that is almost entirely overlooked.

Schisandrin B alleviates acute oxidative stress via modulation of the Nrf2/Keap1-mediated antioxidant pathway

Schisandrin B (Sch B), one of the main effective components of the dried fruit of Schisandra chinensis, protects neurons from oxidative stress in the central nervous system. Here we investigated the neuroprotective effect of Sch B against damage caused by acute oxidative stress and attempted to define the possible mechanisms. Using the elevated plus maze and open field test, we found that forced swimming, an acute stressor, significantly induced anxiety-like behavior that was alleviated by oral Sch B treatment. In addition, the Sch B treatment reduced toxicity, malondialdehyde levels, and production of reactive oxygen species, an important factor for neuron damage. Antioxidants under the control of the nuclear factor erythroid 2-related factor 2 (Nrf2) pathway, such as superoxide dismutase and glutathione, were significantly increased by Sch B treatment. Moreover, a higher percentage of intact cells in the amygdala of treated mice, revealed by Nissl staining, further verified the neuroprotective effect of Sch B. Several proteins, such as Nrf2 and its endogenous inhibitor Kelch-like ECH-associated protein 1 (Keap1), were abnormally expressed in mice subjected to forced swimming, but this abnormal expression was significantly reversed by Sch B treatment. Our results suggest that Sch B may be a potential therapeutic agent against anxiety associated with oxidative stress. The possible mechanism is neuroprotection through enhanced antioxidant activity.

Toxicological Profiling of Metal Oxide Nanoparticles in Liver Context Reveals Pyroptosis in Kupffer Cells and Macrophages versus Apoptosis in Hepatocytes

The liver and the mononuclear phagocyte system are a frequent target for engineered nanomaterials, either as a result of particle uptake and spread from primary exposure sites or systemic administration of therapeutic and imaging nanoparticles. In this study, we performed a comparative analysis of the toxicological impact of 29 metal oxide nanoparticles (NPs), some commonly used in consumer products, in transformed or primary Kupffer cells (KCs) and hepatocytes. We not only observed differences between KCs and hepatocytes, but also differences in the toxicological profiles of transition-metal oxides (TMOs, e. g., Co₃O₄) versus rare-earth oxide (REO) NPs ( e. g., Gd₂O₃). While pro-oxidative TMOs induced the activation of caspases 3 and 7, resulting in apoptotic cell death in both cell types, REOs induced lysosomal damage, NLRP3 inflammasome activation, caspase 1 activation, and pyroptosis in KCs. Pyroptosis was accompanied by cell swelling, membrane blebbing, IL-1β release, and increased membrane permeability, which could be reversed by knockdown of the pore forming protein, gasdermin D. Though similar features were not seen in hepatocytes, the investigation of the cytotoxic effects of REO NPs could also be seen to affect macrophage cell lines such as J774A.1 and RAW 264.7 cells as well as bone marrow-derived macrophages. These phagocytic cell types also demonstrated features of pyroptosis and increased IL-1β production. Collectively, these findings demonstrate important mechanistic considerations that can be used for safety evaluation of metal oxides, including commercial products that are developed from these materials.

Differential Health Effects of Constant versus Intermittent Exposure to Formaldehyde in Mice: Implications for Building Ventilation Strategies

Formaldehyde, an air pollutant in the indoor environment, may have severe effects on human health. The aim of this study is to compare the health effects caused by intermittent exposure to formaldehyde (based on real monitoring) to those caused by exposures at constant concentration. Health effects explored in this study including the oxidative stress, histopathological changes, inflammatory responses, etc. Mice were divided into three groups and exposed to intermittent concentration formaldehyde (0.8 ppm for 12 h and 0 ppm for another 12 h), or constant concentration formaldehyde (0.4 ppm for 24 h) or zero concentration formaldehyde (reference) per day for 7, 14, and 28 days. Following these exposures, bronchoalveolar lavage fluid (BALF), lung tissue and lung tissue homogenate were prepared to measure biomarkers of oxidative stress (ROS, MDA, GSH), histopathological changes, inflammatory responses (EOS, NEU, LYM, IL-4, IL-5, IL-13, IL-6, IL-17A, NF-κB, IL-1β) and apoptosis (caspase-3). Compared to the constant exposure, intermittent exposure to fluctuating formaldehyde concentrations resulted in more profound increases in numbers of inflammatory cells in the BALF, greater biological alterations including apoptosis. The findings imply that with the same average indoor formaldehyde concentrations over the same time, a ventilation strategy to avoid higher peak concentrations would lead to lower health risks.

Primary genotoxicity in the liver following pulmonary exposure to carbon black nanoparticles in mice

Background

Little is known about the mechanism underlying the genotoxicity observed in the liver following pulmonary exposure to carbon black (CB) nanoparticles (NPs). The genotoxicity could be caused by the presence of translocated particles or by circulating inflammatory mediators released during pulmonary inflammation and acute-phase response. To address this, we evaluated induction of pulmonary inflammation, pulmonary and hepatic acute-phase response and genotoxicity following exposure to titanium dioxide (TiO₂), cerium oxide (CeO₂) or CB NPs. Female C57BL/6 mice were exposed by intratracheal instillation, intravenous injection or oral gavage to a single dose of 162 μg NPs/mouse and terminated 1, 28 or 180 days post-exposure alongside vehicle control.

Results

Liver DNA damage assessed by the Comet Assay was observed after intravenous injection and intratracheal instillation of CB NPs but not after exposure to TiO₂ or CeO₂. Intratracheal exposure to NPs resulted in pulmonary inflammation in terms of increased neutrophils influx for all NPs 1 and 28 days post-exposure. Persistent pulmonary acute phase response was detected for all NPs at all three time points while only a transient induction of hepatic acute phase response was observed. All 3 materials were detected in the liver by enhanced darkfield microscopy up to 180 days post-exposure. In contrast to TiO₂ and CeO₂ NPs, CB NPs generated ROS in an acellular assay.

Conclusions

Our results suggest that the observed hepatic DNA damage following intravenous and intratracheal dosing with CB NPs was caused by the presence of translocated, ROS-generating, particles detected in the liver rather than by the secondary effects of pulmonary inflammation or hepatic acute phase response.

Electronic supplementary material

The online version of this article (10.1186/s12989-017-0238-9) contains supplementary material, which is available to authorized users.

Molecular Mechanisms of Zinc Oxide Nanoparticle-Induced Genotoxicity Short Running Title: Genotoxicity of ZnO NPs

Background: Zinc oxide nanoparticles (ZnO NPs) are among the most frequently applied nanomaterials in consumer products. Evidence exists regarding the cytotoxic effects of ZnO NPs in mammalian cells; however, knowledge about the potential genotoxicity of ZnO NPs is rare, and results presented in the current literature are inconsistent. Objectives: The aim of this review is to summarize the existing data regarding the DNA damage that ZnO NPs induce, and focus on the possible molecular mechanisms underlying genotoxic events. Methods: Electronic literature databases were systematically searched for studies that report on the genotoxicity of ZnO NPs. Results: Several methods and different endpoints demonstrate the genotoxic potential of ZnO NPs. Most publications describe in vitro assessments of the oxidative DNA damage triggered by dissoluted Zn²⁺ ions. Most genotoxicological investigations of ZnO NPs address acute exposure situations. Conclusion: Existing evidence indicates that ZnO NPs possibly have the potential to damage DNA. However, there is a lack of long-term exposure experiments that clarify the intracellular bioaccumulation of ZnO NPs and the possible mechanisms of DNA repair and cell survival.

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

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

Sensitive detection of DNA oxidation damage induced by nanomaterials

From a toxicological point of view, nanomaterials are of interest; because - on account of their great surface area relative to mass - they tend to be more reactive than the bulk chemicals from which they are derived. They might in some cases have the potential to damage DNA directly, or could act via the induction of oxidative stress. The comet assay (single cell gel electrophoresis) is widely used to measure DNA strand breaks and also oxidised bases, by including in the procedure digestion with lesion-specific enzymes such as formamidopyrimidine DNA glycosylase (which converts oxidised purines to breaks) or endonuclease III (recognising oxidised pyrimidines). We summarise reports in which these enzymes have been used to study a variety of nanomaterials in diverse cell types. We also stress that it is important to carry out tests of cell viability alongside the genotoxicity assay, since cytotoxicity can lead to adventitious DNA damage. Different concentrations of nanomaterials should be investigated, concentrating on a non-cytotoxic range; and incubating for short and longer periods can give valuable information about the mode of damage induction. The use of lesion-specific enzymes can substantially enhance the sensitivity of the comet assay in detecting genotoxic effects.

Evaluating the mechanistic evidence and key data gaps in assessing the potential carcinogenicity of carbon nanotubes and nanofibers in humans

In an evaluation of carbon nanotubes (CNTs) for the IARC Monograph 111, the Mechanisms Subgroup was tasked with assessing the strength of evidence on the potential carcinogenicity of CNTs in humans. The mechanistic evidence was considered to be not strong enough to alter the evaluations based on the animal data. In this paper, we provide an extended, in-depth examination of the in vivo and in vitro experimental studies according to current hypotheses on the carcinogenicity of inhaled particles and fibers. We cite additional studies of CNTs that were not available at the time of the IARC meeting in October 2014, and extend our evaluation to include carbon nanofibers (CNFs). Finally, we identify key data gaps and suggest research needs to reduce uncertainty. The focus of this review is on the cancer risk to workers exposed to airborne CNT or CNF during the production and use of these materials. The findings of this review, in general, affirm those of the original evaluation on the inadequate or limited evidence of carcinogenicity for most types of CNTs and CNFs at this time, and possible carcinogenicity of one type of CNT (MWCNT-7). The key evidence gaps to be filled by research include: investigation of possible associations between in vitro and early-stage in vivo events that may be predictive of lung cancer or mesothelioma, and systematic analysis of dose-response relationships across materials, including evaluation of the influence of physico-chemical properties and experimental factors on the observation of nonmalignant and malignant endpoints.

Oxidant generation, DNA damage and cytotoxicity by a panel of engineered nanomaterials in three different human epithelial cell lines

Due to the steeply increased use of nanomaterials (NMs) for commercial and industrial applications, toxicological assessment of their potential harmful effects is urgently needed. In this study, we compared the DNA-damaging properties and concurrent cytotoxicity of a panel of 10 engineered NMs in three different cell lines in relation to their intrinsic oxidant generating properties. The human epithelial cell lines A549, HK-2 and HepG2 were chosen to represent relevant target organs for NMs in the lung, kidney and liver. Cytotoxicity, evaluated by WST-1 assay in the treatment concentration range of 0.3-80 µg/cm², was shown for Ag and ZnO NM in all three cell lines. Cytotoxicity was absent for all other NMs, i.e. five types of TiO₂ and two types of multiwalled carbon nanotubes. DNA damage, evaluated by the alkaline comet assay, was observed with Ag and ZnO, albeit only at cytotoxic concentrations. DNA damage varied considerably with the cell line. The oxidant generating properties of the NMs, evaluated by electron spin resonance spectroscopy in cell free conditions, did not correlate with their cytotoxic or DNA-damaging properties. DNA damage by the nanosilver could be partly attributed to its surfactant-containing dispersant. The coating of a TiO₂ sample with the commercial surfactant Curosurf augmented its DNA-damaging properties in A549 cells, while surface modification with serum tended to reduce damage. Our findings indicate that measurement of the intrinsic oxidant-generating capacity of NMs is a poor predictor of DNA damage and that the cytotoxic and DNA-damaging properties of NMs can vary substantially with experimental conditions. Our study also underlines the critical importance of selecting appropriate cell systems and aligned testing protocols. Selection of a cell line on the mere basis of its origin may provide only poor insight on organ-specific hazards of NMs.

Silver nanoparticles: Significance of physicochemical properties and assay interference on the interpretation of in vitro cytotoxicity studies

Silver nanoparticles (AgNPs) have generated a great deal of interest in the research, consumer product, and medical product communities due to their antimicrobial and anti-biofouling properties. However, in addition to their antimicrobial action, concerns have been expressed about the potential adverse human health effects of AgNPs. In vitro cytotoxicity studies often are used to characterize the biological response to AgNPs and the results of these studies may be used to identify hazards associated with exposure to AgNPs. Various factors, such as nanomaterial size (diameter), surface area, surface charge, redox potential, surface functionalization, and composition play a role in the development of toxicity in in vitro test systems. In addition, the interference of AgNPs with in vitro cytotoxicity assays may result in false negative or false positive results in some in vitro biological tests. The goal of this review is to: 1) summarize the impact of physical-chemical parameters, including size, shape, surface chemistry and aggregate formation on the in vitro cytotoxic effects of AgNPs; and 2) explore the nature of AgNPs interference in in vitro cytotoxicity assays.

Silver Nanoparticle-Mediated Cellular Responses in Various Cell Lines: An in Vitro Model

Silver nanoparticles (AgNPs) have attracted increased interest and are currently used in various industries including medicine, cosmetics, textiles, electronics, and pharmaceuticals, owing to their unique physical and chemical properties, particularly as antimicrobial and anticancer agents. Recently, several studies have reported both beneficial and toxic effects of AgNPs on various prokaryotic and eukaryotic systems. To develop nanoparticles for mediated therapy, several laboratories have used a variety of cell lines under in vitro conditions to evaluate the properties, mode of action, differential responses, and mechanisms of action of AgNPs. In vitro models are simple, cost-effective, rapid, and can be used to easily assess efficacy and performance. The cytotoxicity, genotoxicity, and biocompatibility of AgNPs depend on many factors such as size, shape, surface charge, surface coating, solubility, concentration, surface functionalization, distribution of particles, mode of entry, mode of action, growth media, exposure time, and cell type. Cellular responses to AgNPs are different in each cell type and depend on the physical and chemical nature of AgNPs. This review evaluates significant contributions to the literature on biological applications of AgNPs. It begins with an introduction to AgNPs, with particular attention to their overall impact on cellular effects. The main objective of this review is to elucidate the reasons for different cell types exhibiting differential responses to nanoparticles even when they possess similar size, shape, and other parameters. Firstly, we discuss the cellular effects of AgNPs on a variety of cell lines; Secondly, we discuss the mechanisms of action of AgNPs in various cellular systems, and try to elucidate how AgNPs interact with different mammalian cell lines and produce significant effects; Finally, we discuss the cellular activation of various signaling molecules in response to AgNPs, and conclude with future perspectives on research into AgNPs.