Adverse effects of industrial multiwalled carbon nanotubes on human pulmonary cells

Indirect mediators of systemic health outcomes following nanoparticle inhalation exposure

The growing field of nanoscience has shed light on the wide diversity of natural and anthropogenic sources of nano-scale particulates, raising concern as to their impacts on human health. Inhalation is the most robust route of entry, with nanoparticles (NPs) evading mucociliary clearance and depositing deep into the alveolar region. Yet, impacts from inhaled NPs are evident far outside the lung, particularly on the cardiovascular system and highly vascularized organs like the brain. Peripheral effects are partly explained by the translocation of some NPs from the lung into the circulation; however, other NPs largely confined to the lung are still accompanied by systemic outcomes. Omic research has only just begun to inform on the complex myriad of molecules released from the lung to the blood as byproducts of pulmonary pathology. These indirect mediators are diverse in their molecular make-up and activity in the periphery. The present review examines systemic outcomes attributed to pulmonary NP exposure and what is known about indirect pathological mediators released from the lung into the circulation. Further focus was directed to outcomes in the brain, a highly vascularized region susceptible to acute and longer-term outcomes. Findings here support the need for big-data toxicological studies to understand what drives these health outcomes and better predict, circumvent, and treat the potential health impacts arising from NP exposure scenarios.

Joint effects of carbon nanotubes and copper oxide nanoparticles on fermentation metabolism towards Saccharofermentans acetigenes: Enhancing environmental adaptability and transcriptional expression

In this study, the joint effects of widely used copper oxide nanoparticles (CuO NPs) and multi-walled carbon nanotubes (MWCNTs) on the fermentation metabolism of a model acetogenic bacterium Saccharofermentans acetigenes were investigated and the underlying mechanisms were further explored. The presence of sole CuO NPs or MWCNTs severely inhibited the acetate generation, while their co-existences did not further decrease the acetate yield as expected. Further analysis indicated the joint effects facilitated the enhancement of bacterial stimulus response to the environment and interspecies communication, which improved adaptive capacity to the adverse environment involved in nanomaterials. Meanwhile, the co-existence reduced inhibitory effects of sole nanomaterial on the gene expressions and catalytic activities of key enzymes involved in glycolysis and pyruvate metabolism. Therefore, the joint effects could enhance environmental adaptation of S. acetigenes and transcriptional expressions of key enzymes for acetic acid production-related processes, alleviating the inhibition of CuO NPs to acetate production.

Carbon Nanotube Exposure Triggers a Cerebral Peptidomic Response: Barrier Compromise, Neuroinflammation, and a Hyperexcited State

The unique physicochemical properties of carbon nanomaterials and their ever-growing utilization generate a serious concern for occupational risk. Pulmonary exposure to these nanoparticles induces local and systemic inflammation, cardiovascular dysfunction, and even cognitive deficits. Although multiple routes of extrapulmonary toxicity have been proposed, the mechanism for and manner of neurologic effects remain minimally understood. Here, we examine the cerebral spinal fluid (CSF)-derived peptidomic fraction as a reflection of neuropathological alterations induced by pulmonary carbon nanomaterial exposure. Male C57BL/6 mice were exposed to 10 or 40 µg of multiwalled carbon nanotubes (MWCNT) by oropharyngeal aspiration. Serum and CSFs were collected 4 h post exposure. An enriched peptide fraction of both biofluids was analyzed using ion mobility-enabled data-independent mass spectrometry for label-free quantification. MWCNT exposure induced a prominent peptidomic response in the blood and CSF; however, correlation between fluids was limited. Instead, we determined that a MWCNT-induced peptidomic shift occurred specific to the CSF with 292 significant responses found that were not in serum. Identified MWCNT-responsive peptides depicted a mechanism involving aberrant fibrinolysis (fibrinopeptide A), blood-brain barrier permeation (homeobox protein A4), neuroinflammation (transmembrane protein 131L) with reactivity by astrocytes and microglia, and a pro-degradative (signal transducing adapter molecule, phosphoglycerate kinase), antiplastic (AF4/FMR2 family member 1, vacuolar protein sorting-associated protein 18) state with the excitation-inhibition balance shifted to a hyperexcited (microtubule-associated protein 1B) phenotype. Overall, the significant pathologic changes observed were consistent with early neurodegenerative disease and were diagnostically reflected in the CSF peptidome.

The role of single- and multi-walled carbon nanotube in breast cancer treatment

Numerous studies have been conducted to design new strategies for breast cancer treatment. Past studies have shown a wide range of carbon-nanomaterials properties, such as single- and multi-walled carbon nanotubes (SWCNTs and MWCNTs) in breast cancer diagnosis and treatment. In this regard, the current study aims to review the role of both SWCNTs and MWCNTs in breast cancer treatment and diagnosis. For reaching this goal, we reviewed the literature by using various searching engines such as Scopus, PubMed, Google Scholar, Web of Science and MEDLINE. This comprehensive review showed that CNTs could dramatically improve breast cancer treatment and could be used as a novel modality to increase diagnostic accuracy; however, no clinical studies have been conducted based on CNTs. In addition, the literature review demonstrates a lack of enough studies to evaluate the side effects of using CNTs.

Far-reaching advances in the role of carbon nanotubes in cancer therapy

Cancer includes a group of diseases involving unregulated cell growth with the potential to invade or expand to other parts of the body, resulting in an estimate of 9.6 million deaths worldwide in 2018. Manifold studies have been conducted to design more efficacious techniques for cancer therapy due to the inadequacy of conventional treatments including chemotherapy, surgery, and radiation therapy. With the advances in the biomedical applications of nanotechnology-based systems, nanomaterials have gained increasing attention as promising vehicles for targeted cancer therapy and optimizing treatment outcomes. Owing to their outstanding thermal, electrical, optical and chemical properties, carbon nanotubes (CNTs) have been profoundly studied to explore the various perspectives of their application in cancer treatment. The current study aims to review the role of CNTs whether as a carrier or mediator in cancer treatment for enhancing the efficacy as well as the specificity of therapy and reducing adverse side effects. This comprehensive review indicates that CNTs have the capability to be the next generation nanomaterials to actualize noninvasive targeted eradication of tumors. However, further studies are needed to evaluate the consequences of their biomedical application before the transition into clinical trials, since possible adverse effects of CNTs on biological systems have not been clearly understood.

Novel mineralized electrospun chitosan/PVA/TiO2 nanofibrous composites for potential biomedical applications: computational and experimental insights

Electrospun nanofibrous materials serve as potential solutions for several biomedical applications as they possess the ability of mimicking the extracellular matrix (ECM) of tissues. Herein, we report on the fabrication of novel nanostructured composite materials for potential use in biomedical applications that require a suitable environment for cellular viability. Anodized TiO2 nanotubes (TiO2 NTs) in powder form, with different concentrations, were incorporated as a filler material into a blend of chitosan (Cs) and polyvinyl alcohol (PVA) to synthesize composite polymeric electrospun nanofibrous materials. Scanning electron microscopy (SEM), transmission electron microscopy (TEM), Raman spectroscopy, X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), nanoindentation, Brunauer-Emmett-Teller (BET) analysis, and MTT assay for cell viability techniques were used to characterize the architectural, structural, mechanical, physical, and biological properties of the fabricated materials. Additionally, molecular dynamics (MD) modelling was performed to evaluate the mechanical properties of the polymeric PVA/chitosan matrix upon reinforcing the structure with TiO2 anatase nanotubes. The Young's modulus, shear and bulk moduli, Poisson's ratio, Lame's constants, and compressibility of these composites have been computed using the COMPASS molecular mechanics force fields. The MD simulations demonstrated that the inclusion of anatase TiO2 improves the mechanical properties of the composite, which is consistent with our experimental findings. The results revealed that the mineralized material improved the mechanical strength and the physical properties of the composite. Hence, the composite material has potential for use in biomedical applications.

Pleural translocation and lesions by pulmonary exposed multi-walled carbon nanotubes

Carbon nanotubes (CNTs) are recently developed tubular nanomaterials, with diameters ranging from a few nanometers to tens of nanometers, and the length reaching up to several micrometers. They can be either single-walled carbon nanotubes (SWCNTs) or multi-walled carbon nanotubes (MWCNTs). Due to their nano-scaled structure, CNTs have a unique set of mechanical, electrical, and chemical properties that make them useful in information technologies, optoelectronics, energy technologies, material sciences, medical technologies, and other fields. However, with the wide application and increasing production of CNTs, their potential risks have led to concerns regarding their impact on environment and health. The shape of some types of CNTs is similar to asbestos fibers, which suggests that these CNTs may cause characteristic pleural diseases similar to those found in asbestos-exposed humans, such as pleural plaques and malignant mesothelioma. Experimental data indicate that CNTs can induce lung and pleural lesions, inflammation, pleural fibrosis, lung tumors, and malignant mesothelioma upon inhalation in the experimental animals. In this review, we focus on the potential of MWCNTs to induce diseases similar to those by asbestos, molecular and cellular mechanisms associated with these diseases, and we discuss a method for evaluating the pleural toxicity of MWCNTs.

A numerical investigation of the heat transfer characteristics of water-based mango bark nanofluid flowing in a double-pipe heat exchanger

In this study, the heat transfer characteristics of a new class of nanofluids made from mango bark was numerically simulated and studied during turbulent flow through a double pipe heat exchanger. A range of volume fractions was considered for a particle size of 100 nm. A two-phase flow was considered using the mixture model. The mixture model governing equations of continuity, momentum, energy and volume fraction were solved using the finite-volume method. The results showed an increase of the Nusselt number by 68% for a Reynolds number of 5,000 and 45% for a Reynolds number of 13 000, and the heat transfer coefficient of the nanofluid was about twice that of the base fluid. In addition, the Nusselt number decreased by an average value of 0.76 with an increase of volume fraction by 1%. It was also found that there was a range of Reynolds numbers in which the trend of the average heat transfer coefficient of the nanofluid was completely reversed, and several plots showing zones of higher heat transfer which if taken advantage of in design will lead to higher heat transfer while avoiding other zones that have low heat transfer. It is hoped that these results will influence the thermal design of new heat exchangers.

Induction of caspase-2 gene expression in carboxyl-functionalized carbon nanotube-treated human T-cell leukemia (Jurkat) cell line

Carbon nanotubes (CNTs) have great potential as novel diagnostic or therapeutic tools in biomedicine but, cellular toxicity must be well considered before widespread application of CNTs. Many chemical agents exert their toxicity through apoptotic pathways by induction of caspase biomolecules. In the current study, effects of carboxyl-functionalized single-walled (SW) and multi-walled (MW) CNTs at a single dose of 100 µg ml^-1 on the survival of Jurkat cells were examined using MTT assay. Additionally, the impacts of carboxylated CNTs on the gene expression levels of selected caspases were investigated. Jurkat cells were exposed to CNTs (100 µg ml^-1 for 72 h) and then expression levels of selected caspase genes (Cas) were evaluated by qRT-PCR analysis. Housekeeping genes, β-actin, and glyceraldehyde 3-phosphate dehydrogenase (GAPDH), were used as normalization controls. The results showed only a mild decrease in the viability of Jurkat cells treated with carboxylated MWCNT. The results of qRT-PCR analysis revealed the elevated level of Cas2 mRNA in the cells treated with carboxylated MWCNT (6.08-fold) and carboxylated SWCNT (1.20-fold). The expression levels of Cas4, Cas6, Cas8, and Cas10 genes were increased not significantly compared to the control untreated cells. Our findings suggested that exposure to carboxyl-functionalized CNTs could be resulted in up-regulation of the Cas2 gene and not initiator Cas8 and Cas10 genes. In addition, it seems that carboxylated MWCNT was more potent than SWCNT in activation of Cas2 gene expression and triggering cell death signal in a manner different from intrinsic or extrinsic apoptosis pathways.

Thermal Reduction of Graphene Oxide Mitigates Its In Vivo Genotoxicity Toward Xenopus laevis Tadpoles

The worldwide increase of graphene family materials raises the question of the potential consequences resulting from their release in the environment and future consequences on ecosystem health, especially in the aquatic environment in which they are likely to accumulate. Thus, there is a need to evaluate the biological and ecological risk but also to find innovative solutions leading to the production of safer materials. This work focuses on the evaluation of functional group-safety relationships regarding to graphene oxide (GO) in vivo genotoxic potential toward X. laevis tadpoles. For this purpose, thermal treatments in H₂ atmosphere were applied to produce reduced graphene oxide (rGOs) with different surface group compositions. Analysis performed indicated that GO induced disturbances in erythrocyte cell cycle leading to accumulation of cells in G0/G1 phase. Significant genotoxicity due to oxidative stress was observed in larvae exposed to low GO concentration (0.1 mg·L⁻¹). Reduction of GO at 200 °C and 1000 °C produced a material that was no longer genotoxic at low concentrations. X-ray photoelectron spectroscopy (XPS) analysis indicated that epoxide groups may constitute a good candidate to explain the genotoxic potential of the most oxidized form of the material. Thermal reduction of GO may constitute an appropriate “safer-by-design” strategy for the development of a safer material for environment.

The toxicity and therapeutic effects of single-and multi-wall carbon nanotubes on mice breast cancer

Herein, we have investigated the toxicity of SWCNTs and MWCNTs in vitro and in vivo, and assessed their therapeutic effects on a typical animal model of breast cancer in order to obtain: first, the cytotoxicity effects of CNTs on MC4L2 cell and mice, second the impact of CNTs on ablation of breast tumor. CNTs especially SWCNTs were toxic to organs and induced death at high dosages. In this case, some of the liver cells showed a relative shrinkage which was also confirmed by Annexin test in MC4L2 cells. Moreover, CNTs decreased the tumor volume. BCL2 gene was down-regulated, and BAX and Caspase-3 were also up-regulated in the treated groups with CNTs. As a result, CNTs especially MWCNT in lower dosages can be used as a promising drug delivery vehicle for targeted therapy of abnormal cells in breast cancer.

Mice pancreatic islets protection from oxidative stress induced by single-walled carbon nanotubes through naringin

The growing use of carbon nanotubes (CNTs) emphasizes the importance of its potential toxic effects on the human health. Previous studies proved that CNTs caused oxidative stress and decreased cell viability. On the other hand, reactive oxygen species (ROS) and oxidative stress impaired β-cell functions and reduced the insulin secretion. However, there is not any study on the effects of CNTs on islets and β-cells. Therefore, the present study aimed to evaluate the effects of single-walled CNTs (SWCNTs) on oxidative stress in islets in addition to the protective effects of naringin (NRG) as an antioxidant . We examined the effects of SWCNTs and naringin on islets by 3,4 3-(4,5-dimethylthiazol-2-yl)-2, 5-diphenyltetrazolium bromide (MTT) assay; measurement of insulin secretion, ROS, and malondialdehyde (MDA); activities of superoxide dismutase (SOD), catalase (CAT), and glutathione (GSH) peroxidase (GSH-Px); and content of GSH and mitochondrial membrane potential (MMP). The MTT assay demonstrated that decreased viability of islets cells was dose-dependent with exposure to SWCNTs. Further studies revealed that SWCNTs decreased insulin secretion and MMP, induced the formation of ROS, increased the level of MDA, and decreased the activities of SOD, GSH-Px, and CAT and content of GSH. Furthermore, the pretreatment of islets with naringin significantly reverted back these changes. These findings revealed that SWCNTs might induce the oxidative stress to pancreatic islets, causing the occurrence of diabetes, and the protective effects of naringin that was mediated by augmentation of the antioxidant defense system of islets. Our research indicated the necessity for further in vivo and in vitro researches on the effects of SWCNTs and naringin on diabetes.

Carbon Nanotubes and Other Engineered Nanoparticles Induced Pathophysiology on Mesothelial Cells and Mesothelial Membranes

Nanoparticles have great potential for numerous applications due to their unique physicochemical properties. However, concerns have been raised that they may induce deleterious effects on biological systems. There is accumulating evidence that, like asbestos, inhaled nanomaterials of >5 μm and high aspect ratio (3:1), particularly rod-like carbon nanotubes, may inflict pleural disease including mesothelioma. Additionally, a recent set of case reports suggests that inhalation of polyacrylate/nanosilica could in part be associated with inflammation and fibrosis of the pleura of factory workers. However, the adverse outcomes of nanoparticle exposure to mesothelial tissues are still largely unexplored. In that context, the present review aims to provide an overview of the relevant pathophysiological implications involving toxicological studies describing effects of engineered nanoparticles on mesothelial cells and membranes. In vitro studies primarily emphasize on simulating cellular uptake and toxicity of nanotubes on benign or malignant cell lines. On the other hand, in vivo studies focus on illustrating endpoints of serosal pathology in rodent animal models. From a molecular aspect, some nanoparticle categories are shown to be cytotoxic and genotoxic after acute treatment, whereas chronic incubation may lead to malignant-like transformation. At an organism level, a number of fibrous shaped nanotubes are related with features of chronic inflammation and MWCNT-7 is the only type to consistently inflict mesothelioma.

Relevance of Physicochemical Characterization of Nanomaterials for Understanding Nano-cellular Interactions

The manufactured nanomaterials (NMs) have specific physicochemical properties that confer unique mechanical, optical, electrical and magnetic characteristics that are beneficial for biomedical and industrial applications. However, recent studies have suggested that such specific physicochemical properties of the NMs may define nano-bio interactions thereby determining their toxic potential.One of the major concerns about NMs is the potential to induce cancer, suggested by some experimental studies, as seen for titanium dioxide nanomaterials or carbon nanotubes. To analyze in a short term the carcinogenic properties of a compound, genotoxicity assays in mammalian cell lines or animal models are frequently used. However, the investigation of the genotoxic properties of NMs has been inconclusive, up to date, since divergent results have been reported throughout the literature. While trying to understand how the NMs' characteristics may encompass increased toxicological effects that harbor uncertainties for public health, the use of correlation analysis highlights some physicochemical properties that influence the genotoxic potential of these NM.In this chapter, it is hypothesized that the different genotoxicity observed in closely related NMs may be due to subtle differences in their physicochemical characteristics. The present work provides an overview of the studies exploring the correlation between physicochemical properties of nanomaterials and their genotoxic effects in human cells, with focus on the toxicity of two groups of NMs, titanium dioxide nanomaterials and multiwalled-carbon nanotubes. It is suggested that, for tackling NMs' uncertainties, the in-depth investigation of the nano-bio interactions must be foreseen, where in vitro research must be integrated with in vivo and biomonitoring approaches, to cope with the complex dynamic behaviour of nanoscale materials.

Impact of biopersistent fibrous dusts on glycolysis, glutaminolysis and serine metabolism in A549 cells

The conversion rates of different metabolic pathways summarized as a metabolic signature mirror the physiological functions and the general physiological status of a cell. The present study compared the impact of crocidolite and chrysotile asbestos, glass fibers and multi‑walled carbon nanotubes (MWCN) of two different lengths (1‑2 µm and 5‑15 µm) on the conversion rates in glycolysis, glutaminolysis and serine metabolism of A549 cells. The concentration tested was 1 µg/cm2 for all fibers. A concentration of 5 µg/cm2 was additionally used for chrysotile and crocidolite, and 25 µg/cm2 for glass fibers and MWCN. With respect to the inhibitory effect on cell proliferation and the extent of metabolic alterations, the present study revealed the following ranking among the fibers tested: Chrysotile>crocidolite>glass fibers>MWCN 5‑15 µm>MWCN 1‑2 µm. For the asbestos and glass fibers this ranking correlated best with the number of fibers. It appeared that the results observed for MWCN did not match this correlation. However, electron microscopy revealed an agglomeration of MWCN. The agglomeration decreased the toxicologically relevant number of fibers by forming larger particle‑like shapes and explained the smaller effects of MWCN 5‑15 µm and 1‑2 µm on cell proliferation and metabolism.

Characteristics of Carbon Material Formation on SBA-15 and Ni-SBA-15 Templates by Acetylene Decomposition and Their Bioactivity Effects

Carbon spheres and tubes were formed from acetylene decomposition on SBA-15 and Ni-SBA-15 at 650-850 °C. At 650 °C, the decomposed carbons covered the surface of the support, and no carbon spheres and filament materials were formed. Carbon sphere formation occurred at 750 °C-850 °C; with diameters ranging from 0.8 μm-1.1 μm. For Ni-SBA-15, the diameters of the spheres and filaments were 0.8 μm and 62 nm, respectively, at 650 °C. At 750 °C, the diameter of the ball carbon materials ranged from 0.7 μm-0.8 μm, the diameter of the carbon tubes formed was 120-130 nm, and their pore diameter was 8.0 nm-11 nm. At 850 °C, the diameters of ball carbon materials and carbon tubes were similar to those of the materials at the formation temperature, 750 °C. Si, O and C were the main constituents of SBA-15; Ni-SBA-15 and carbon material formation supports. High-ring PAHs (such as BaP (five rings); IND (six rings); DBA (five rings) and B[ghi]P (six rings)) exist in carbon materials. SBA-15 revealed insignificant cytotoxicity, but Ni-SBA-15 inhibited the proliferation of human lung cancer cells (A549). Less inhibition on cell viability and reactive oxidative species (ROS) generation on A549 were determined for carbon material formation on the Ni-SBA-15 compared to the Ni-SBA-15.

Lung inflammation and lack of genotoxicity in the comet and micronucleus assays of industrial multiwalled carbon nanotubes Graphistrength(©) C100 after a 90-day nose-only inhalation exposure of rats

Background

Graphistrength^© C100 multiwalled carbon nanotubes (MWCNT) provide superior electrical and mechanical properties for various applications. The evaluation of the intrinsic hazard properties of Graphistrength^© C100 is an essential step for safe use. A general feature of multiwalled carbon nanotubes after inhalation or intratracheal exposures is the induction of an inflammatory reaction in the lungs sometimes associated with local genotoxic effects.

Methods

After investigating different parameters for the aerosol generation and performing a 5-day inhalation range finding study, male and female Wistar rats were exposed nose-only for 90 days to target concentrations of 0.05, 0.25 and 5.0 mg/m³ air of Graphistrength^© C100 and sacrificed 24 h and 90 days after the last exposure. Broncho-alveolar lavage fluid (BALF) was also collected and analyzed for inflammatory parameters. Twenty-four hours post-exposure, chromosomal aberrations in the bone marrow cells were evaluated by the micronucleus test and DNA damages in the lung, kidney and liver cells by both the standard and the human 8-oxoguanine DNA N-glycosylase 1 (hOGG1)-modified comet assay. All studies were performed according to the OECD test guidelines.

Results

An inflammatory lung reaction and the release of inflammatory factors in the BALF were observed in all rats exposed to 5.0 mg/m³, associated with changes in the differential white blood cells counts. The slight changes in BALF parameters at 0.25 mg/m³ recovered and signs of lung clearance of the MWCNT were observed. No pathological changes were observed on the pleura. Neither increase in the number of micronucleated polychromatic erythrocytes nor increase in percent DNA damage were observed at any concentration.

Conclusions

Lung inflammation characteristic of an overload with insoluble particles was observed after a 90-day exposure to 5.0 mg/m³ of Graphistrength^© C100. Clear signs of clearance and recovery were observed at 0.25 mg/m³. No genotoxicity was detected locally in lung and distally in bone marrow, liver and kidney. Therefore, Graphistrength^© C100 appears of low concern in term of local and systemic genotoxicity and a No-Observed Adverse Effect Concentration (NOAEC) of 0.25 mg/m³ (0.28 mg/m³ as actual concentration) was established for the repeated-dose toxicity.

Electronic supplementary material

The online version of this article (doi:10.1186/s12989-015-0096-2) contains supplementary material, which is available to authorized users.

MWCNTs Induce ROS Generation, ERK Phosphorylation, and SOD-2 Expression in Human Mesothelial Cells

Biological oxidative responses are involved in the toxicity of multiwall carbon nanotubes (MWCNTs), which may cause asbestos-like pathogenicity. Superoxide dismutase 2 (SOD-2) has been proposed as a biomarker of early responses to mesothelioma-inducing fibers. This study was conducted to investigate the alteration of SOD-2 expression in the human mesothelial cell lines Met-5A after exposure to nontoxic doses of MWCNTs and the potential signaling pathway. The parameters measured included the viability, morphological change, superoxide formation, extracellular signal-regulated kinase 1/2 (ERK1/2) phosphorylation, and messenger RNA (mRNA)/protein levels of SOD-2. Our results showed that MWCNTs upregulated SOD-2 expression at both mRNA and protein level. Coincidently, both superoxide formation and ERK1/2 phosphorylation were observed in Met-5A cells exposed to MWCNTs and were diminished by pretreatment with the reactive oxidative species (ROS) scavenger, N-acetyl-l-(+)-cysteine (NAC). To further investigate the role of ROS/ERK1/2 in MWCNTs-induced SOD-2 overexpression, prior to MWCNTs exposure, cells were pretreated with the Mitogen-activated protein kinase kinase 1/2 (MEK 1/2) inhibitor (U0126) or with NAC. Both pretreatments decreased the MWCNTs-induced overexpression of SOD-2. These results suggest that upregulation of SOD-2 in Met-5A cells exposed to MWCNTs is mediated by ROS formation and ERK1/2 activation.

Mechanism of induction of binucleated cells by multiwalled carbon nanotubes as revealed by live-cell imaging analysis

INTRODUCTION

Asbestos-induced formation of mesothelioma has been attributed to phenotypic and morphological changes in cells caused by polyploidization and aneuploidization, and multiwalled carbon nanotubes (MWCNTs) are suspected to have similar adverse effects due to the similarity in their physical form. MWCNTs and crocidolite, a kind of asbestos, show similar genotoxicity characteristics in vitro, including induction of binucleated cells. We here focused on the mechanisms underlying polyploidization during cell division on exposure to MWCNTs and conducted confocal live-cell imaging analysis using MDA-435 human breast cancer cells in which chromosomes and centromeres were visualized using fluorescent proteins.

FINDINGS

During anaphase, relatively short MWCNT fibers (approximately 5 μm) migrated rapidly to either of the daughter cells, whereas some long MWCNT fibers (approximately 20 μm) remained inside the contractile ring and induced the formation of binucleated cells through impairment of cytokinesis. This toxicity mechanism has also been observed with crocidolite.

CONCLUSIONS

Our findings indicate that the mechanism of polyploidization by MWCNTs is very similar to that observed with crocidolite.

Endocytosis of Multiwalled Carbon Nanotubes in Bronchial Epithelial and Mesothelial Cells

Bronchial epithelial cells and mesothelial cells are crucial targets for the safety assessment of inhalation of carbon nanotubes (CNTs), which resemble asbestos particles in shape. Intrinsic properties of multiwalled CNTs (MWCNTs) are known to cause potentially hazardous effects on intracellular and extracellular pathways. These interactions alter cellular signaling and affect major cell functions, resulting in cell death, lysosome injury, reactive oxygen species production, apoptosis, and cytokine release. Furthermore, CNTs are emerging as a novel class of autophagy inducers. Thus, in this study, we focused on the mechanisms of MWCNT uptake into the human bronchial epithelial cells (HBECs) and human mesothelial cells (HMCs). We verified that MWCNTs are actively internalized into HBECs and HMCs and were accumulated in the lysosomes of the cells after 24-hour treatment. Next, we determined which endocytosis pathways (clathrin-mediated, caveolae-mediated, and macropinocytosis) were associated with MWCNT internalization by using corresponding endocytosis inhibitors, in two nonphagocytic cell lines derived from bronchial epithelial cells and mesothelioma cells. Clathrin-mediated endocytosis inhibitors significantly suppressed MWCNT uptake, whereas caveolae-mediated endocytosis and macropinocytosis were also found to be involved in MWCNT uptake. Thus, MWCNTs were positively taken up by nonphagocytic cells, and their cytotoxicity was closely related to these three endocytosis pathways.

MDSC and TGFβ Are Required for Facilitation of Tumor Growth in the Lungs of Mice Exposed to Carbon Nanotubes

During the last decades, changes have been observed in the frequency of different histologic subtypes of lung cancer, one of the most common causes of morbidity and mortality, with a declining proportion of squamous cell carcinomas and an increasing proportion of adenocarcinomas, particularly in developed countries. This suggests the emergence of new etiologic factors and mechanisms, including those defining the lung microenvironment, promoting tumor growth. Assuming that the lung is the main portal of entry for broadly used nanomaterials and their established proinflammatory propensities, we hypothesized that nanomaterials may contribute to changes facilitating tumor growth. Here, we report that an acute exposure to single-walled carbon nanotubes (SWCNT) induces recruitment and accumulation of lung-associated myeloid-derived suppressor cells (MDSC) and MDSC-derived production of TGFβ, resulting in upregulated tumor burden in the lung. The production of TGFβ by MDSC requires their interaction with both SWCNT and tumor cells. We conclude that pulmonary exposure to SWCNT favors the formation of a niche that supports ingrowth of lung carcinoma in vivo via activation of TGFβ production by SWCNT-attracted and -presensitized MDSC.

Application of Carbon Nanotubes in Nanomedicine

Carbon Nanotubes (CNTs) have become a technological field with great potential since they can be applied in almost every aspect of modern life. One of the sectors where CNTs are expected to play a vital role is the field of medical science. This chapter focuses on the latest developments in applications of CNTs for nanomedicine. A brief history of CNTs and a general introduction to the field are presented. Then, the preparation of CNTs that makes them ideal for use in medical applications is highlighted. Examples of common applications, including cell penetration, drug delivery, and gene delivery and imaging are given. Finally, the toxicity of carbon nanotubes is discussed.

The role of p53 in lung macrophages following exposure to a panel of manufactured nanomaterials

Manufactured nanomaterials (MNMs) have the potential to improve everyday life as they can be utilised in numerous medical applications and day-to-day consumer products. However, this increased use has led to concerns about the potential environmental and human health impacts. The protein p53 is a key transcription factor implicated in cellular defence and reparative responses to various stress factors. Additionally, p53 has been implicated in cellular responses following exposure to some MNMs. Here, the role of the MNM mediated p53 induction and activation and its downstream effects following exposure to five well-characterised materials [namely two types of TiO2, two carbon black (CB), and one single-walled carbon nanotube (SWCNT)] were investigated. MNM internalisation, cellular viability, p53 protein induction and activation, oxidative stress, inflammation and apoptosis were measured in murine cell line and primary pulmonary macrophage models. It was observed that p53 was implicated in the biological responses to MNMs, with oxidative stress associated with p53 activation (only following exposure to the SWCNT). We demonstrate that p53 acted as an antioxidant and anti-inflammatory in macrophage responses to SWCNT and CB NMs. However, p53 was neither involved in MNM-induced cellular toxicity, nor in the apoptosis induced by these MNMs. Moreover, the physicochemical characteristics of MNMs seemed to influence their biological effects-SWCNT the materials with the largest surface area and a fibrous shape were the most cytotoxic in this study and were capable of the induction and activation of p53.

Inflammasome activation in airway epithelial cells after multi-walled carbon nanotube exposure mediates a profibrotic response in lung fibroblasts

Background

In vivo studies have demonstrated the ability of multi-walled carbon nanotubes (MWCNT) to induce airway remodeling, a key feature of chronic respiratory diseases like asthma and chronic obstructive pulmonary disease. However, the mechanism leading to remodeling is poorly understood. Particularly, there is limited insight about the role of airway epithelial injury in these changes.

Objectives

We investigated the mechanism of MWCNT-induced primary human bronchial epithelial (HBE) cell injury and its contribution in inducing a profibrotic response.

Methods

Primary HBE cells were exposed to thoroughly characterized MWCNTs (1.5-24 μg/mL equivalent to 0.37-6.0 μg/cm²) and MRC-5 human lung fibroblasts were exposed to 1:4 diluted conditioned medium from these cells. Flow cytometry, ELISA, immunostainings/immunoblots and PCR analyses were employed to study cellular mechanisms.

Results

MWCNT induced NLRP3 inflammasome dependent pyroptosis in HBE cells in a time- and dose-dependent manner. Cell death and cytokine production were significantly reduced by antioxidants, siRNA to NLRP3, a caspase-1 inhibitor (z-WEHD-FMK) or a cathepsin B inhibitor (CA-074Me). Conditioned medium from MWCNT-treated HBE cells induced significant increase in mRNA expression of pro-fibrotic markers (TIMP-1, Tenascin-C, Procollagen 1, and Osteopontin) in human lung fibroblasts, without a concomitant change in expression of TGF-beta. Induction of pro-fibrotic markers was significantly reduced when IL-1β, IL-18 and IL-8 neutralizing antibodies were added to the conditioned medium or when conditioned medium from NLRP3 siRNA transfected HBE cells was used.

Conclusions

Taken together these results demonstrate induction of a NLRP3 inflammasome dependent but TGF-beta independent pro-fibrotic response after MWCNT exposure.

Effect of fiber length on carbon nanotube-induced fibrogenesis

Given their extremely small size and light weight, carbon nanotubes (CNTs) can be readily inhaled by human lungs resulting in increased rates of pulmonary disorders, particularly fibrosis. Although the fibrogenic potential of CNTs is well established, there is a lack of consensus regarding the contribution of physicochemical attributes of CNTs on the underlying fibrotic outcome. We designed an experimentally validated in vitro fibroblast culture model aimed at investigating the effect of fiber length on single-walled CNT (SWCNT)-induced pulmonary fibrosis. The fibrogenic response to short and long SWCNTs was assessed via oxidative stress generation, collagen expression and transforming growth factor-beta (TGF-β) production as potential fibrosis biomarkers. Long SWCNTs were significantly more potent than short SWCNTs in terms of reactive oxygen species (ROS) response, collagen production and TGF-β release. Furthermore, our finding on the length-dependent in vitro fibrogenic response was validated by the in vivo lung fibrosis outcome, thus supporting the predictive value of the in vitro model. Our results also demonstrated the key role of ROS in SWCNT-induced collagen expression and TGF-β activation, indicating the potential mechanisms of length-dependent SWCNT-induced fibrosis. Together, our study provides new evidence for the role of fiber length in SWCNT-induced lung fibrosis and offers a rapid cell-based assay for fibrogenicity testing of nanomaterials with the ability to predict pulmonary fibrogenic response in vivo.

Biological responses according to the shape and size of carbon nanotubes in BEAS-2B and MESO-1 cells

This study aimed to investigate the influence of the shape and size of multi-walled carbon nanotubes (MWCNTs) and cup-stacked carbon nanotubes (CSCNTs) on biological responses in vitro. Three types of MWCNTs – VGCF^®-X, VGCF^®-S, and VGCF^® (vapor grown carbon fibers; with diameters of 15, 80, and 150 nm, respectively) – and three CSCNTs of different lengths (CS-L, 20–80 μm; CS-S, 0.5–20 μm; and CS-M, of intermediate length) were tested. Human bronchial epithelial (BEAS-2B) and malignant pleural mesothelioma cells were exposed to the CNTs (1–50 μg/mL), and cell viability, permeability, uptake, total reactive oxygen species/superoxide production, and intracellular acidity were measured. CSCNTs were less toxic than MWCNTs in both cell types over a 24-hour exposure period. The cytotoxicity of endocytosed MWCNTs varied according to cell type/size, while that of CSCNTs depended on tube length irrespective of cell type. CNT diameter and length influenced cell aggregation and injury extent. Intracellular acidity increased independently of lysosomal activity along with the number of vacuoles in BEAS-2B cells exposed for 24 hours to either CNT (concentration, 10 μg/mL). However, total reactive oxygen species/superoxide generation did not contribute to cytotoxicity. The results demonstrate that CSCNTs could be suitable for biological applications and that CNT shape and size can have differential effects depending on cell type, which can be exploited in the development of highly specialized, biocompatible CNTs.

Potential toxicity of differential functionalized multiwalled carbon nanotubes (MWCNT) in human cell line (BEAS2B) and Caenorhabditis elegans

The aim of this study was to evaluate in vitro (human bronchial epithelial cells, BEAS2B cells) and in vivo (the nematode Caenorhabditis elegans, C. elegans) toxicity outcomes following exposure to pristine as well as surface-functionalized multiwalled carbon nanotubes (MWCNT) following hydroxylation-oxygenation (O(+)), amination (NH2), or carboxylation (COOH) of the carbon nanotubes (CNT). Cell viability and proliferation were measured by Ez-Cytox, trypan blue exclusion, and colony formation assays. The genotoxic potential of the MWCNT was determined by using the alkaline comet assay. In addition, survival and reproduction were used as endpoints for detection of toxicity of MWCNT in C. elegans. The carboxylated (COOH)-MWCNT was found most toxic as evidenced by cytotoxic and genotoxic among all tested compounds. The order of sensitivity was COOH > O(+) > NH2 > pristine. There were almost no marked changes in survival following exposure of C. elegans to MWCNT. It is of interest that only pristine MWCNT exerted significant reduction in reproductive capacity of C. elegans. Surface functionalization significantly influenced the bioactivity of MWCNT, which displayed species as well as target-organ specificity. The mechanisms underlying these specific modes of nano-biological interactions need to be elucidated.

Size-dependent effect of zinc oxide on toxicity and inflammatory potential of human monocytes

With the rapid development of nanomedicines, it is important to understand their potential immunotoxicity. Zinc oxide (ZnO) nanoparticles have several applications in the pharmaceutical and biomedicine industries. This study investigates the effect of particles size (nano and micro) of ZnO on viability, phagocytosis, and cytokine induction in human monocytes, THP-1 cells, a model of the innate immune system. Cells were incubated with nano (approximately 100 nm) and micro (approximately 5 μm) sized ZnO particles in a concentration range of 10-100 μg/ml. The parameters measured included the MTT assay, phagocytosis assay, enzyme-linked immunosorbent assay (ELISA), gene expression, and DNA analysis. ZnO particles significantly decreased cell viability in a size- and concentration-dependent manner associated with significant alterations in phagocytic capacity of monocytes. Exposure of THP-1 cells to both sizes of ZnO stimulated and increased release of proinflammatory cytokines interleukin (IL)-1β, tumor necrosis factor (TNF)-α, and IL-6, as well as chemokine IL-8, and upregulated the expression of monocyte chemoattractant protein-1 and cyclooxygenase-2 genes. However, ZnO particles did not markedly affect monocytes DNA. Collectively, these results suggest higher propensity of nano ZnO particles in inducing cytotoxicity and inflammation in human monocytes regardless of micro size, and caution needs to be taken concerning their biological application.

Determinants of carbon nanotube toxicity

In the last few years questions have been raised regarding the potential toxicity of carbon nanotubes (CNTs) to humans and environment. It is believed that the physico-chemical characteristics of these materials are key determinants of CNT interaction with living organisms, and hence determine their toxicity. As for other nanomaterials, the most important of these characteristics are the length, diameter, surface area, tendency to agglomerate, bio-durability, presence and nature of catalyst residues as well as chemical functionalization of the CNT. This review highlights the recent advancements in the understanding of the CNT properties which are essential in determining CNT toxicity. Hence the focus is on CNT dimensions, surface properties, bio-durability and corona formation as these fields have evolved greatly in recent years. A deeper understanding of these events and their underlying mechanisms could provide a molecular explanation of the biological and physiological responses following CNT administration and therefore help in the development of safe by design materials.

Chronic exposure to carbon nanotubes induces invasion of human mesothelial cells through matrix metalloproteinase-2

Malignant mesothelioma is one of the most aggressive forms of cancer known. Recent studies have shown that carbon nanotubes (CNTs) are biopersistent and induce mesothelioma in animals, but the underlying mechanisms are not known. Here, we investigate the effect of long-term exposure to high aspect ratio CNTs on the aggressive behaviors of human pleural mesothelial cells, the primary cellular target of human lung mesothelioma. We show that chronic exposure (4 months) to single- and multiwalled CNTs induced proliferation, migration, and invasion of the cells similar to that observed in asbestos-exposed cells. An up-regulation of several key genes known to be important in cell invasion, notably matrix metalloproteinase-2 (MMP-2), was observed in the exposed mesothelial cells as determined by real-time PCR. Western blot and enzyme activity assays confirmed the increased expression and activity of MMP-2. Whole genome microarray analysis further indicated the importance of MMP-2 in the invasion gene signaling network of the exposed cells. Knockdown of MMP-2 in CNT and asbestos-exposed cells by shRNA-mediated gene silencing effectively inhibited the aggressive phenotypes. This study demonstrates CNT-induced cell invasion and indicates the role of MMP-2 in the process.

Progress on Cytotoxicity In Vitro of Carbon Nanotubes

According to recent references, the progress on cytotoxicity in vitro of carbon nanotubes (CNTs) including the factors such as size , residual metal catalysts,and detection methods influencing cytotoxicity of CNTs are summarized. The results shown that residual metal catalysts must be removed as much as possible and ensure CNTs in some concentration range before using them.Biocompatibility of CNTs must be considered and chemical modification of CNTs to improve their use safety and advantages is indispensable.

Lung alterations following single or multiple low-dose carbon black nanoparticle aspirations in mice

Carbon black nanoparticle (CBNP) applications in high doses have been shown to be harmful to the lung. It is postulated that even small, environmentally relevant concentrations induce changes on lung homeostasis. The present study determined the impact of low-dose single and multiple CBNP (Printex 90) applications on mouse alveolar cell metabolism, especially inflammatory and oxidative stress parameters. Nanoparticles were administered to mice by a single or 8 oropharyngeal aspirations at wk 1, 2, 3, 5, 7, 9, 11, and 12 using 7 μg Printex 90, 7 μg DQ12 quartz (positive control), with water vehicle and saline as negative controls. After 2 d or 3 mo lung function was analyzed. Further lung histology, bronchoalveolar lavage fluid (BALF) parameters, and mRNA expression of cytokines and antioxidants enzymes in type II pneumocytes were measured on d 3 or after 3 mo. Single low-dose Printex 90 application induced no marked alterations in lung functions or BALF phospholipid levels but significant decrease in superoxide dismutase 2 and numerically elevated glutathione peroxidase 3 mRNA expression levels in type II pneumocytes. Multiple CBNP applications produced reduced lung function, collagen accumulation, elevated phospholipid levels in BALF, and a massive infiltration of macrophages. Type II pneumocyte mRNA expression of antioxidative enzymes remained unchanged throughout the subchronic experiment, but showed a significant decrease in interleukin (IL)-6Rα mRNA expression. This study demonstrates that an environmentally relevant CBNP concentration induced an acute inflammatory response, an effect that is exacerbated throughout the subchronic duration.

Investigation of the pulmonary bioactivity of double-walled carbon nanotubes

Double-walled carbon nanotubes (DWCNT) are a rather new and unexplored variety of carbon nanotubes. Previously conducted studies established that exposure to a variety of carbon nanotubes produced lung inflammation and fibrosis in mice after pharyngeal aspiration. However, the bioactivity of double-walled carbon nanotubes (DWCNT) has not been determined. In this study, the hypothesis that DWCNT would induce pulmonary toxicity was explored by analyzing the pulmonary bioactivity of DWCNT. To test this hypothesis, C57Bl/6 mice were exposed to DWCNT by pharyngeal aspiration. Mice underwent whole-lung lavage (WLL) to assess pulmonary inflammation and injury, and lung tissue was examined histologically for development of pulmonary disease as a function of dose and time. The results showed that DWCNT exposure produced a dose-dependent increase in WLL polymorphonuclear leukocytes (PMN), indicating that DWCNT exposure initiated pulmonary inflammation. DWCNT exposure also produced a dose-dependent rise in lactate dehydrogenase (LDH) activity, as well as albumin levels, in WLL fluid, indicating that DWCNT exposure promoted cytotoxicity as well as decreases in the integrity of the blood-gas barrier in the lung, respectively. In addition, at 7 and 56 d postexposure, the presence of significant alveolitis and fibrosis was noted in mice exposed to 40 μg/mouse DWCNT. In conclusion, this study provides insight into previously uninvestigated pulmonary bioactivity of DWCNT exposure. Data indicate that DWCNT exposure promotes inflammation, injury, and fibrosis in the lung.

Respiratory toxicities of nanomaterials -- a focus on carbon nanotubes

Carbon nanotubes (CNT) are emblematic nanomaterials, presenting unique physico-chemical properties, such as mechanical, thermal, or electrical conductivity, that have led to a large number of actual applications and uses, as well as (future) developments in aerospace, automobiles, nanoelectronic, or nanomedicine. CNT are currently used in many devices (computers, aircraft airframe, and sporting goods such as tennis rackets, bicycles, golf irons) and have also emerged as efficient drug delivery carriers in the biomedical and drug delivery fields[1]. Because of these actual and future applications, there's an increasing concern regarding the consequences that could result from human exposure to CNT, particularly at the respiratory level, since it represents a major route of exposure to nanomaterials. This review will highlight the advancement in the actual knowledge on lung toxicities of CNT, and try to better understand the underlying biological mechanisms, as well as the importance of physico-chemical determinants directly related to CNT characteristics.