Intracellular accumulation of indium ions released from nanoparticles induces oxidative stress, proinflammatory response and DNA damage

Mitochondrial Oxidative Stress Is the General Reason for Apoptosis Induced by Different-Valence Heavy Metals in Cells and Mitochondria

This review analyzes the causes and consequences of apoptosis resulting from oxidative stress that occurs in mitochondria and cells exposed to the toxic effects of different-valence heavy metals (Ag+, Tl+, Hg2+, Cd2+, Pb2+, Al3+, Ga3+, In3+, As3+, Sb3+, Cr6+, and U6+). The problems of the relationship between the integration of these toxic metals into molecular mechanisms with the subsequent development of pathophysiological processes and the appearance of diseases caused by the accumulation of these metals in the body are also addressed in this review. Such apoptosis is characterized by a reduction in cell viability, the activation of caspase-3 and caspase-9, the expression of pro-apoptotic genes (Bax and Bcl-2), and the activation of protein kinases (ERK, JNK, p53, and p38) by mitogens. Moreover, the oxidative stress manifests as the mitochondrial permeability transition pore (MPTP) opening, mitochondrial swelling, an increase in the production of reactive oxygen species (ROS) and H2O2, lipid peroxidation, cytochrome c release, a decline in the inner mitochondrial membrane potential (ΔΨmito), a decrease in ATP synthesis, and reduced glutathione and oxygen consumption as well as cytoplasm and matrix calcium overload due to Ca2+ release from the endoplasmic reticulum (ER). The apoptosis and respiratory dysfunction induced by these metals are discussed regarding their interaction with cellular and mitochondrial thiol groups and Fe2+ metabolism disturbance. Similarities and differences in the toxic effects of Tl+ from those of other heavy metals under review are discussed. Similarities may be due to the increase in the cytoplasmic calcium concentration induced by Tl+ and these metals. One difference discussed is the failure to decrease Tl+ toxicity through metallothionein-dependent mechanisms. Another difference could be the decrease in reduced glutathione in the matrix due to the reversible oxidation of Tl+ to Tl3+ near the centers of ROS generation in the respiratory chain. The latter may explain why thallium toxicity to humans turned out to be higher than the toxicity of mercury, lead, cadmium, copper, and zinc.

The Cytotoxicity of Tungsten Ions Derived from Nanoparticles Correlates with Pulmonary Toxicity

Tungsten carbide nanoparticles (nano-WC) are prevalent in composite materials, and are attributed to their physical and chemical properties. Due to their small size, nano-WC particles can readily infiltrate biological organisms via the respiratory tract, thereby posing potential health hazards. Despite this, the studies addressing the cytotoxicity of nano-WC remain notably limited. To this purpose, the BEAS-2B and U937 cells were cultured in the presence of nano-WC. The significant cytotoxicity of nano-WC suspension was evaluated using a cellular LDH assay. To investigate the cytotoxic impact of tungsten ions (W⁶⁺) on cells, the ion chelator (EDTA-2Na) was used to adsorb W⁶⁺ from nano-WC suspension. Subsequent to this treatment, the modified nano-WC suspension was subjected to flow cytometry analysis to evaluate the rates of cellular apoptosis. According to the results, a decrease in W⁶⁺ could mitigate the cellular damage and enhance cell viability, which indicated that W⁶⁺ indeed exerted a significant cytotoxic influence on the cells. Overall, the present study provides valuable insight into the toxicological mechanisms underlying the exposure of lung cells to nano-WC, thereby reducing the environmental toxicant risk to human health.

In-Vitro Study of Indium (III) Sulfate-Containing Medium on the Viability and Adhesion Behaviors of Human Dermal Fibroblast on Engineered Surfaces

Tissues and organs consist of cells organized in specified patterns that support their function, as exemplified by tissues such as skin, muscle, and cornea. It is, therefore, important to understand how external cues, such as engineered surfaces or chemical contaminants, can influence the organization and morphology of cells. In this work, we studied the impact of indium sulfate on human dermal fibroblast (GM5565) viability, production of reactive oxygen species (ROS), morphology, and alignment behavior on tantalum/silicon oxide parallel line/trench surface structures. The viability of cells was measured using the alamarBlue™ Cell Viability Reagent probe, while the ROS levels in cells were quantified using cell-permeant 2',7'-dichlorodihydrofluorescein diacetate. Cell morphology and orientation on the engineered surfaces were characterized using fluorescence confocal and scanning electron microscopy. When cells were cultured in media containing indium (III) sulfate, the average cell viability decreased by as much as ~32% and the concentration of cellular ROS increased. Cell geometry became more circular and compact in the presence of indium sulfate. Even though actin microfilaments continue to preferentially adhere to tantalum-coated trenches in the presence of indium sulfate, the cells are less able to orient along the line axes of the chips. Interestingly, the indium sulfate-induced changes in cell alignment behavior are pattern dependent-a larger proportion of adherent cells on structures with line/trench widths in the range of 1 μm and 10 μm lose the ability to orient themselves, compared to those grown on structures with line widths smaller than 0.5 μm. Our results show that indium sulfate impacts the response of human fibroblasts to the surface structure to which they adhere and underscores the importance of evaluating cell behaviors on textured surfaces, especially in the presence of potential chemical contaminants.

Nanomaterials for Fluorescence and Multimodal Bioimaging

Bioconjugated nanomaterials replace molecular probes in bioanalysis and bioimaging in vitro and in vivo. Nanoparticles of silica, metals, semiconductors, polymers, and supramolecular systems, conjugated with contrast agents and drugs for image-guided (MRI, fluorescence, PET, Raman, SPECT, photodynamic, photothermal, and photoacoustic) therapy infiltrate into preclinical and clinical settings. Small bioactive molecules like peptides, proteins, or DNA conjugated to the surfaces of drugs or probes help us to interface them with cells and tissues. Nevertheless, the toxicity and pharmacokinetics of nanodrugs, nanoprobes, and their components become the clinical barriers, underscoring the significance of developing biocompatible next-generation drugs and contrast agents. This account provides state-of-the-art advancements in the preparation and biological applications of bioconjugated nanomaterials and their molecular, cell, and in vivo applications. It focuses on the preparation, bioimaging, and bioanalytical applications of monomodal and multimodal nanoprobes composed of quantum dots, quantum clusters, iron oxide nanoparticles, and a few rare earth metal ion complexes.

Influence of Indium (III) Chloride on Human Dermal Fibroblast Cell Adhesion on Tantalum/Silicon Oxide Nano-Composites

Cell adhesion is an essential biological function for division, migration, signaling and tissue development. While it has been demonstrated that this cell function can be modified by using nanometer-scale surface topographic structures, it remains unknown how contaminants such as indium (III) ion might influence this specific cell behavior. Herein, the influence of indium chloride on human dermal fibroblast (GM5565) adhesion characteristics was investigated, given the frequent contact of contaminants with skin. The morphology of the adherent cells and their mitochondrial reticulum was characterized on cell culture dishes and nanopatterned surfaces by using fluorescence confocal microscopy and scanning electron microscopy. Results showed a significant proportion of cells lost their ability to align preferentially along the line axes of the nanopattern upon exposure to 3.2 mM indium chloride, with cells aligned within 10° of the pattern line axes reduced by as much as ~70%. Concurrent with the cell adhesion behaviors, the mitochondria in cells exposed to indium chloride exhibit a punctate staining that contrasts with the normal network of elongated tubular geometry seen in control cells. Our results demonstrate that exposure to indium chloride has detrimental effects on the behavior of human fibroblasts and adversely impacts their mitochondrial morphology. This shows the importance of evaluating the biological impacts of indium compounds.

Cellular Effects of Silver Nanoparticle Suspensions on Lung Epithelial Cells and Macrophages

Background: Silver nanoparticles (AgNPs) are used in industrial applications as catalysts, sanitary materials, and health supplements. Generally, AgNPs have shown cytotoxicity such as cell membrane damage. However, the mechanisms of their toxicity have not been completely elucidated. Methods: The cellular effects (cell viability, induction of chemokine and cellular oxidative stress) of two AgNP water suspensions (AgNP-A for cosmetic application and AgNP-B for industrial application) on epithelial-like A549 cells and macrophage-like differentiated THP-1 (dTHP-1) cells were examined. Results: AgNPs caused enhancement of IL-8 expression and oxidative stress. The cellular uptake of AgNP-A cells was observed. However, the cellular uptake of AgNP-B into A549 cells was hardly observed. Moreover, the intracellular Ag level was increased by AgNP suspensions exposure. Cell viability was not affected by AgNP suspensions exposure. Conclusions: AgNPs induce chemokine expression and cellular oxidative stress on culture cells. The intracellular Ag level may be important for these cellular effects.

Proinflammatory response caused by lead nanoparticles triggered by engulfed nanoparticles

In this study, the cellular effects of lead (Pb) nanoparticles with a primary particle size of 80 nm were evaluated in two types of cell lines: human lung carcinoma A549 and macrophage-differentiated THP-1 cells (dTHP-1). The cellular responses induced by the Pb nanoparticles varied among the cell types. Exposure to Pb nanoparticles for 24 h at a concentration of 100 μg/ml induced interleukin-8 (IL-8) expression in dTHP-1 cells. Induction of IL-8 expression in A549 was lower than dTHP-1 cells. Pb nanoparticles also induced the gene expression of heme oxygenase-1 in dTHP-1 cells but not in A549 cells. Though cellular uptake of Pb nanoparticles was observed in both the cell types, the amount of internalized Pb particles was lower in A549 cells than that in dTHP-1 cells. Gene expression of metallothionein 2A was remarkably enhanced by Pb nanoparticle exposure in dTHP-1 cells. Compared with Pb nanoparticles, induction of cytokines caused by lead nitrate (Pb[NO₃ ]₂ ), a water-soluble Pb compound, was smaller. In conclusion, the present study revealed that Pb nanoparticles induced a stronger cellular response than Pb(NO₃ )₂ , primarily by eliciting cytokine production, in a cell type-dependent manner.

Exploiting the biological response of two Serratia fonticola strains to the critical metals, gallium and indium

The use of microorganisms that allows the recovery of critical high-tech elements such as gallium (Ga) and indium (In) has been considered an excellent eco-strategy. In this perspective, it is relevant to understand the strategies of Ga and In resistant strains to cope with these critical metals. This study aimed to explore the effect of these metals on two Ga/In resistant strains and to scrutinize the biological processes behind the oxidative stress in response to exposure to these critical metals. Two strains of Serratia fonticola, A3242 and B2A1Ga1, with high resistance to Ga and In, were submitted to metal stress and their protein profiles showed an overexpressed Superoxide Dismutase (SOD) in presence of In. Results of inhibitor-protein native gel incubations identified the overexpressed enzyme as a Fe-SOD. Both strains exhibited a huge increase of oxidative stress when exposed to indium, visible by an extreme high amount of reactive oxygen species (ROS) production. The toxicity induced by indium triggered biological mechanisms of stress control namely, the decrease in reduced glutathione/total glutathione levels and an increase in the SOD activity. The effect of gallium in cells was not so boisterous, visible only by the decrease of reduced glutathione levels. Analysis of the cellular metabolic viability revealed that each strain was affected differently by the critical metals, which could be related to the distinct metal uptakes. Strain A3242 accumulated more Ga and In in comparison to strain B2A1Ga1, and showed lower metabolic activity. Understanding the biological response of the two metal resistant strains of S. fonticola to stress induced by Ga and In will tackle the current gap of information related with bacteria-critical metals interactions.

The toxicology of gallium oxide in comparison with gallium arsenide and indium oxide

Gallium arsenide (GaAs) and indium oxide (In₂O₃) are used in electronic industries at high and increasing tonnages since decades. Gallium oxide (Ga₂O₃) is an emerging wide-bandgap transparent conductive oxide with as yet little industrial use. Since GaAs has received critical attention due to the arsenic ion, it seemed reasonable to compare its toxicology with the respective endpoints of Ga₂O₃ and In₂O₃ toxicology in order to find out if and to what extent arsenic contributes. In addition, the toxicology of Ga₂O₃ has not yet been adequately reviewed, Therefore, this review provides the first evaluation of all available toxicity data on Ga₂O₃. The acute toxicity of all three compounds is rather low. Subchronic inhalation studies in rats and mice revealed persistent pulmonary alveolar proteinosis (PAP) and/or alveolar histiocytic infiltrates down to the lowest tested concentration in rats and mice, i.e. 0.16 mg Ga₂O₃/m³. These are also the predominant effects after GaAs and In₂O₃ exposure at similarly low levels, i.e. 0.1 mg/m³ each. Subchronic Ga₂O₃ exposure caused a minimal microcytic anemia with erythrocytosis in rats (at 6.4 mg/m³ and greater) and mice (at 32 and 64 mg/m³), a decrease in epididymal sperm motility and concentration as well as testicular degeneration at 64 mg/m³. At comparable concentrations the hematological effects and male fertility of GaAs were much stronger. The stronger effects of GaAs are due to its better solubility and presumed higher bioavailability. The database for In₂O₃ is too small and subchronic testing was at very low levels to allow conclusive judgements if blood/blood forming or degrading and male fertility organs/tissues would also be targets.

Toxicity of engineered nanomaterials with different physicochemical properties and the role of protein corona on cellular uptake and intrinsic ROS production

The Organisation for Economic Co-operation and Development has listed thirteen engineered nanomaterials (ENM) in order to investigate their toxicity on human health. Silicon dioxide (SiO₂) and titanium dioxide (TiO₂) are included on that list and we added indium tin oxide (ITO) nanoparticles (NPs) to our study, which is not listed on OECD suggested ENM to be investigated, however ITO NPs has a high potential of industrial production. We evaluate the physicochemical properties of SiO₂ NPs (10-20 nm), TiO₂ nanofibers (NFs; 3 μm length) and ITO NPs (<50 nm) and the impact of protein-corona formation on cell internalization. Then, we evaluated the toxicity of uncoated ENM on human lung epithelial cells exposed to 10 and 50 μg/cm² for 24 h. TiO₂ NFs showed the highest capability to adsorb proteins onto the particle surface followed by SiO₂ NPs and ITO NPs after acellular incubation with fetal bovine serum. The protein adsorption had no impact on Alizarin Red S conjugation, intrinsic properties for reactive oxygen (ROS) formation or cell uptake for all types of ENM. Moreover, TiO₂ NFs induced highest cell alterations in human lung epithelial cells exposed to 10 and 50 μg/cm² while ITO NPs induced moderated cytotoxicity and SiO₂ NPs caused even lower cytotoxicity under the same conditions. DNA, proteins and lipids were mainly affected by TiO₂ NFs followed by SiO₂ NPs with toxic effects in protein and lipids while limited variations were detected after exposure to ITO NPs on spectra analyzed by Fourier Transform Infrared Spectroscopy.

Indium oxide nanoparticles induce lung intercellular toxicity between bronchial epithelial cells and macrophages

Concerns have been raised over the safety and health of industrial workers exposed to indium oxide nanoparticles (IO-NPs) when working. IO-NPs were previously shown in vitro and in vivo to be cytotoxic, but the mechanism of pathogenesis was unclear. In this study, the effects of IO-NPs on lung cells associated with respiratory and immune barriers and the toxic effects of intercellular cascades were studied. Here IO-NPs had acute toxicity to Wistar rats over a time course (5 days post-intratracheal instillation). Following treatment epithelial cells (16HBE) or macrophages (RAW264.7) with IO-NPs or IO fine particles (IO-FPs), the damage of 16HBE cells caused by IO-NPs was serious, mainly in the mitochondrial and rough endoplasmic reticulum. The lactate dehydrogenase level also showed that cytotoxicity in vitro was more serious for IO-NPs compared with IO-FPs. The level of In³⁺ (examined by inductively coupled plasma mass spectrometry) in 16HBE cells was 10 times higher than that in RAW cells. In³⁺ , releasing from IO-NPs absorbed by 16HBE cells, could not only significantly inhibit the phagocytosis and migration of macrophages (P < .0001), but also stimulate RAW cells to secrete high levels of inflammatory cytokines. IO-NPs can directly damage pulmonary epithelial cells. The In³⁺ released by epithelial cells affect the phagocytosis and migration of macrophages, which may be a new point for the decrease in the clearance of alveolar surfactants and the development of IO-related pulmonary alveolar proteinosis.

Nitrative DNA damage in lung epithelial cells exposed to indium nanoparticles and indium ions

Indium compounds have been widely used in manufacturing displays of mobile phones, computers and televisions. However, inhalation exposure to indium compounds causes interstitial pneumonia in exposed workers and lung cancer in experimental animals. 8-Nitroguanine (8-nitroG) is a mutagenic DNA lesion formed under inflammatory conditions and may participate in indium-induced carcinogenesis. In this study, we examined 8-nitroG formation in A549 cultured human lung epithelial cells treated with indium compounds, including nanoparticles of indium oxide (In₂O₃) and indium-tin oxide (ITO), and indium chloride (InCl₃). We performed fluorescent immunocytochemistry to examine 8-nitroG formation in indium-exposed A549 cells. All indium compounds significantly increased 8-nitroG formation in A549 cells at 5 ng/ml after 4 h incubation. 8-NitroG formation was largely reduced by 1400 W, methyl-β-cyclodextrin (MBCD) and monodansylcadaverine (MDC), suggesting the involvement of nitric oxide synthase and endocytosis. 8-NitroG formation in A549 cells was also largely suppressed by small interfering RNA (siRNA) for high-mobility group box-1 (HMGB1), receptor for advanced glycation and end products (AGER, RAGE) and Toll-like receptor 9 (TLR9). These results suggest that indium compounds induce inflammation-mediated DNA damage in lung epithelial cells via the HMGB1-RAGE-TLR9 pathway. This mechanism may contribute to indium-induced genotoxicity in the respiratory system.

Low serum indium levels induce expression disorders of some inflammatory factors

OBJECTIVES

It has been reported that occupational exposure to indium compounds, including indium-tin oxide, can induce pulmonary inflammation resulting in serious indium lung disease. However, whether there is an early effect of indium exposure on inflammatory factor expression remains unclear.

METHODS

Twenty indium-tin oxide processing workers and 15 healthy volunteers were recruited to measure serum indium levels, respiratory symptoms, pulmonary function, and serum inflammatory factor levels.

RESULTS

Although low serum indium was detected in workers, lung abnormalities were not increased, compared with healthy population. However, serum G-CSF, IL-4, IL-5, TNF-alpha, and TNF-beta levels were significantly increased, while IL-16 and TIMP-1 were obviously down-regulated in indium-tin oxide processing workers. These inflammatory factor levels showed a significant correlation with serum indium levels.

CONCLUSIONS

Basing on our findings, we speculate that low serum indium levels may induce inflammatory responses, which may be an adaptive response or may cause lung diseases. Therefore, further experiments or follow-up is needed. However, better safeguard procedures and indium exposure reduction should be considered in ITO industry.

Evaluation of cytotoxicity, apoptosis, and genotoxicity induced by indium chloride in macrophages through mitochondrial dysfunction and reactive oxygen species generation

Due to rapid advances in the era of electronic technologies, indium has played the important material for the production of liquid crystal display screens in the semiconductor and optoelectronic industries. The present study focuses on evaluating the toxic effects and related mechanisms of indium chloride (InCl₃) on RAW264.7 macrophages. Cytotoxicity was induced by InCl₃ in a concentration- and time-dependent manner. InCl₃ had the ability to induce macrophage death through apoptosis rather than through necrosis. According to the cytokinesis-block micronucleus assay and alkaline single-cell gel electrophoresis assay, InCl₃ induced DNA damage, also called genotoxicity, in a concentration-dependent manner. Cysteine-dependent aspartate-directed protease (caspase)-3, -8, and -9 were activated by InCl₃ in a concentration-dependent manner. Mitochondria dysfunction and cytochrome c release from the mitochondria were induced by InCl₃ in a concentration-dependent manner. Downregulation of BCL2 and upregulation of BAD were induced by InCl₃ in a concentration-dependent manner. More, we proposed that InCl₃ treatment generated reactive oxygen species (ROS) in a concentration-dependent manner. In conclusion, the current study revealed that InCl₃ induced macrophage cytotoxicity, apoptosis, and genotoxicity via a mitochondria-dependent apoptotic pathway and ROS generation.

A proteome-wide assessment of the oxidative stress paradigm for metal and metal-oxide nanomaterials in human macrophages

Responsible implementation of engineered nanomaterials (ENMs) into commercial applications is an important societal issue, driving demand for new approaches for rapid and comprehensive evaluation of their bioactivity and safety. An essential part of any research focused on identifying potential hazards of ENMs is the appropriate selection of biological endpoints to evaluate. Herein, we use a tiered strategy employing both targeted biological assays and untargeted quantitative proteomics to elucidate the biological responses of human THP-1 derived macrophages across a library of metal/metal oxide ENMs, raised as priority ENMs for investigation by NIEHS's Nanomaterial Health Implications Research (NHIR) program. Our results show that quantitative cellular proteome profiles readily distinguish ENM types based on their cytotoxic potential according to induction of biological processes and pathways involved in the cellular antioxidant response, TCA cycle, oxidative stress, endoplasmic reticulum stress, and immune responses as major processes impacted. Interestingly, bioinformatics analysis of differentially expressed proteins also revealed new biological processes that were influenced by all ENMs independent of their cytotoxic potential. These included biological processes that were previously implicated as mechanisms cells employ as adaptive responses to low levels of oxidative stress, including cell adhesion, protein translation and protein targeting. Unsupervised clustering revealed the most striking proteome changes that differentiated ENM classes highlight a small subset of proteins involved in the oxidative stress response (HMOX1), protein chaperone functions (HS71B, DNJB1), and autophagy (SQSTM), providing a potential new panel of markers of ENM-induced cellular stress. To our knowledge, the results represent the most comprehensive profiling of the biological responses to a library of ENMs conducted using quantitative mass spectrometry-based proteomics. The results provide a basis to identify the patterns of a diverse set of cellular pathways and biological processes impacted by ENM exposure in an important immune cell type, laying the foundation for multivariate, pathway-level structure activity assessments of ENMs in the future.

Synthesis, Characterization, and Drug Delivery Application of Self-assembling Amphiphilic Cyclodextrin

The main aim of the research was to synthesize amphiphilic cyclodextrin (AMCD) by substituting C12 alkyl chain to a β-cyclodextrin (βCD) in a single step and to study its self-assembly in an aqueous medium. The drug delivery application of the AMCD was also evaluated by encapsulating tamoxifen citrate as a model hydrophobic drug. AMCD was able to self-assemble in aqueous media, forming nanovesicles of size < 200 nm, capable of encapsulating tamoxifen citrate (TMX). Molecular docking and MD simulation studies revealed the interaction between TMX and AMCD which formed a stable complex. TEM and AFM studies showed that nanovesicles were perfectly spherical having a smooth surface and a theoretical AMCD bilayer thickness of ~ 7.2 nm as observed from SANS studies. XRD and DSC studies revealed that TMX was amorphized and molecularly dispersed in AMCD bilayer which was released slowly following Fickian diffusion. AMCD has excellent hemocompatibility as opposed to βCD and no genotoxicity. IC₅₀ of TMX against MCF-7 cell lines was significantly reduced from 11.43 to 7.96 μg/ml after encapsulation in nanovesicle because of nanovesicles being endocytosed by the MCF-7 cells. AMCD was well tolerated by IV route at a dose of > 2000 mg/kg in rats. Pharmacokinetic profile of TMX after encapsulation was improved giving 3-fold higher AUC; extended mean residence time is improving chances of nanovesicle to extravasate in tumor via EPR effect.

The early onset and persistent worsening pulmonary alveolar proteinosis in rats by indium oxide nanoparticles

Workplace inhalation exposure to indium compounds has been reported to produce 'indium lung disease' characterized by pulmonary alveolar proteinosis (PAP), granulomas, and pulmonary fibrosis. However, there is little information about the pulmonary toxicity of nano-sized indium oxide (In₂O₃), which is widely used in various applications such as liquid crystal displays. In this study, we evaluated the time-course and dose-dependent lung injuries by In₂O₃ nanoparticles (NPs) after a single intratracheal instillation to rats. In₂O₃ NPs were instilled to female Wistar rats at 7.5, 30, and 90 cm²/rat and lung injuries were evaluated at day 1, 3, 7, 14, 30, 90, and 180 after a single intratracheal instillation. Treatment of In₂O₃ NPs induced worsening diverse pathological changes including PAP, persistent neutrophilic inflammation, type II cell hyperplasia, foamy macrophages, and granulomas in a time- and dose-dependent manner. PAP was induced from day 3 and worsened throughout the study. The concentrations of interleukin-1β, tumor necrosis factor-α, and monocyte chemoattractant protein-1 in bronchoalveolar lavage fluid (BALF) showed dose- and time-dependent increases and the levels of these inflammatory mediators are consistent with the data of inflammatory cells in BALF and progressive lung damages by In₂O₃ NPs. This study suggests that a single inhalation exposure to In₂O₃ NPs can produce worsening lung damages such as PAP, chronic active inflammation, infiltration of foamy macrophages, and granulomas. The early onset and persistent PAP even at the very low dose (7.5 cm²/rat) implies that the re-evaluation of occupational recommended exposure limit for In₂O₃ NPs is urgently needed to protect workers.

In Vivo Biotransformations of Indium Phosphide Quantum Dots Revealed by X-Ray Microspectroscopy

Many attempts have been made to synthesize cadmium-free quantum dots (QDs), using nontoxic materials, while preserving their unique optical properties. Despite impressive advances, gaps in knowledge of their intracellular fate, persistence, and excretion from the targeted cell or organism still exist, precluding clinical applications. In this study, we used a simple model organism (Hydra vulgaris) presenting a tissue grade of organization to determine the biodistribution of indium phosphide (InP)-based QDs by X-ray fluorescence imaging. By complementing elemental imaging with In L-edge X-ray absorption near edge structure, unique information on in situ chemical speciation was obtained. Unexpectedly, spectral profiles indicated the appearance of In-O species within the first hour post-treatment, suggesting a fast degradation of the InP QD core in vivo, induced mainly by carboxylate groups. Moreover, no significant difference in the behavior of bare core QDs and QDs capped with an inorganic Zn(Se,S) gradient shell was observed. The results paralleled those achieved by treating animals with an equivalent dose of indium salts, confirming the preferred bonding type of In³⁺ ions in Hydra tissues. In conclusion, by focusing on the chemical identity of indium along a 48 h long journey of QDs in Hydra, we describe a fast degradation process, in the absence of evident toxicity. These data pave the way to new paradigms to be considered in the biocompatibility assessment of QD-based biomedical applications, with greater emphasis on the dynamics of in vivo biotransformations, and suggest strategies to drive the design of future applied materials for nanotechnology-based diagnosis and therapeutics.

Validation of metallothionein, interleukin-8, and heme oxygenase-1 as markers for the evaluation of cytotoxicity caused by metal oxide nanoparticles

Metal oxide nanoparticles have an industrial value, although their harmful effects are also known. Induction of respiratory inflammation through their inhalation is a serious indicator of their toxicity. Although the phenomenon of metal ion release is involved in the induction of inflammation, all metal ions are not necessarily toxic. However, currently, no particular index to evaluate cytotoxicity caused by nanoparticles exists. An index based on biological response is critical. In the present study, we examined the gene expression-based index for nanoparticle-derived cytotoxicity. The cellular effects of six kinds of metal oxide nanoparticles, ZnO, NiO, CuO, MgO, Bi₂O₃, and MoO₃ on A549 cells were examined. It was seen that lactate dehydrogenase (LDH) assay, which is one of the most important assays for assessing cell membrane damage, is inhibited by metal ions released from the metal oxide nanoparticles. In some cases, enzyme activity-based assay was not suitable for the evaluation of cytotoxicity of nanoparticles. ZnO and CuO nanoparticles displayed severe cytotoxicity and enhanced gene expression of heme oxygenase-1 (HO-1) and interleukin-8 (IL-8). The IL-8 gene expression was also increased from Bi₂O₃ exposure. Additionally, the gene expression of metallothionein 2A (MT2A) was enhanced in the ZnO, CuO, and Bi₂O₃ exposed cells. These results suggest that these nanoparticles released metal ions in the cells. The enhancement of HO-1, IL-8, and MT2A gene expressions was related to the cytotoxic activity of metal oxide nanoparticles. Thus, the expression level of these genes is a good indicator of nanotoxicology of metal oxide nanoparticles.

Reactive oxygen species independent genotoxicity of indium tin oxide nanoparticles triggered by intracellular degradation

Indium tin oxide (ITO) is widely used as a transparent conducting electrode in photoelectron devices. Because ITO production has soared, the potential health hazards caused by occupational exposure to this material have attracted much attention. However, little is known about the mechanisms of the toxic action of ITO nanoparticles (NPs). The present study was designed to examine the genotoxic mechanisms of ITO NPs using human lung epithelial A549 cells. We found that exposing A549 cells to ITO NPs triggered the intracellular accumulation of ITO NPs, the generation of reactive oxygen species (ROS), and the induction of DNA damage. Treatment of the cells with N-acetyl-l-cysteine (NAC), an ROS quenching agent, decreased intracellular ROS levels but not DNA damage, indicating that the genotoxic effect of ITO NPs is not mediated by intracellular ROS. Interestingly, treatment with ammonium chloride, a lysosomotropic agent, decreased intracellular solubility of ITO NPs and attenuated DNA damage. Nuclear accumulation of indium ions in ITO-NP-exposed cells was confirmed by inductively coupled plasma-mass spectrometry. Our results indicate that the ITO-NP-mediated genotoxicity is caused by indium ions that are solubilized in the acidic lysosomal condition and accumulated in the nucleus where they damage DNA, without the involvement of ROS.

The toxicology of indium oxide

Indium oxide (In₂O₃) is a technologically important semiconductor essentially used, doped with tin oxide, to form indium tin oxide (ITO). It is poorly soluble in all so far tested physiologic media. After repeated inhalation, In₂O₃ particles accumulate in the lungs. Their mobilization can cause significant systemic exposure over long periods of time. An increasing number of cases of severe lung effects (characterized by pulmonary alveolar proteinosis, emphysema and/or interstitial fibrosis) in workers of the ITO industry warrants a review of the toxicological hazards also of In₂O₃. The database on acute and chronic toxicity/carcinogenicity/genotoxicity/reproductive toxicity as well skin/eye irritation and sensitization is very limited or even lacking. Short-term and subchronic inhalation studies in rats and mice revealed persistent alveolar proteinosis, inflammation and early indicators of fibrosis in the lungs down to concentrations of 1 mg/m³. Epidemiological and medical surveillance studies, serum/blood indium levels in workers as well as data on the exposure to airborne indium concentrations indicate a need for measures to reduce exposure at In₂O₃ workplaces.

Nitrative DNA damage in cultured macrophages exposed to indium oxide

Objectives:

Indium compounds are used in manufacturing displays of mobile phones and televisions. However, these materials cause interstitial pneumonia in exposed workers. Animal experiments demonstrated that indium compounds caused lung cancer. Chronic inflammation is considered to play a role in lung carcinogenesis and fibrosis induced by particulate matters. 8-Nitroguanine (8-nitroG) is a mutagenic DNA lesion formed during inflammation and may participate in carcinogenesis. To clarify the mechanism of carcinogenesis, we examined 8-nitroG formation in indium-exposed cultured cells.

Methods:

We treated RAW 264.7 mouse macrophages with indium oxide (In₂O₃) nanoparticles (primary diameter: 30-50 nm), and performed fluorescent immunocytochemistry to detect 8-nitroG. The extent of 8-nitroG formation was evaluated by quantitative image analysis. We measured the amount of nitric oxide (NO) in the culture supernatant of In₂O₃-treated cells by the Griess method. We also examined the effects of inhibitors of inducible NO synthase (iNOS) and endocytosis on In₂O₃-induced 8-nitroG formation.

Results:

In₂O₃ significantly increased the intensity of 8-nitroG formation in RAW 264.7 cells in a dose-dependent manner. In₂O₃-induced 8-nitroG formation was observed at 2 h and further increased at 4 h, and the amount of NO released from In₂O₃-exposed cells was significantly increased at 2-4 h compared with the control. 8-NitroG formation was suppressed by 1400W (an iNOS inhibitor), methyl-β-cyclodextrin and monodansylcadaverine (inhibitors of caveolae- and clathrin-mediated endocytosis, respectively).

Conclusions:

These results suggest that endocytosis and NO generation participate in indium-induced 8-nitroG formation. NO released from indium-exposed inflammatory cells may induce DNA damage in adjacent lung epithelial cells and contribute to carcinogenesis.

Cytotoxic effects of ZnO nanoparticles on mouse testicular cells

Background

Nanoscience and nanotechnology are developing rapidly, and the applications of nanoparticles (NPs) have been found in several fields. At present, NPs are widely used in traditional consumer and industrial products, however, the properties and safety of NPs are still unclear and there are concerns about their potential environmental and health effects. The aim of the present study was to investigate the potential toxicity of ZnO NPs on testicular cells using both in vitro and in vivo systems in a mouse experimental model.

Methods

ZnO NPs with a crystalline size of 70 nm were characterized with various analytical techniques, including ultraviolet-visible spectroscopy, Fourier transform infrared spectroscopy, X-ray diffraction, transmission electron microscopy, and atomic force microscopy. The cytotoxicity of the ZnO NPs was examined in vitro on Leydig cell and Sertoli cell lines, and in vivo on the testes of CD1 mice injected with single doses of ZnO NPs.

Results

ZnO NPs were internalized by Leydig cells and Sertoli cells, and this resulted in cytotoxicity in a time- and dose-dependent manner through the induction of apoptosis. Apoptosis likely occurred as a consequence of DNA damage (detected as γ-H2AX and RAD51 foci) caused by increase in reactive oxygen species associated with loss of mitochondrial membrane potential. In addition, injection of ZnO NPs in male mice caused structural alterations in the seminiferous epithelium and sperm abnormalities.

Conclusion

These results demonstrate that ZnO NPs have the potential to induce apoptosis in testicular cells likely through DNA damage caused by reactive oxygen species, with possible adverse consequences for spermatogenesis and therefore, male fertility. This suggests that evaluating the potential impacts of engineered NPs is essential prior to their mass production, to address both the environmental and human health concerns and also to develop sustainable and safer nanomaterials.

The toxicology of indium tin oxide

Indium tin oxide (ITO) is a technologically important semiconductor. An increasing number of cases of severe lung effects (characterized by pulmonary alveolar proteinosis and/or interstitial fibrosis) in ITO-exposed workers warrants a review of the toxicological hazards. Short- and long-term inhalation studies in rats and mice revealed persistent alveolar proteinosis, inflammation and fibrosis in the lungs down to concentrations as low as 0.01mg/m(3). In rats, the incidences of bronchiolo-alveolar adenomas and carcinomas were significantly increased at all concentrations. In mice, ITO was not carcinogenic. A few bronchiolo-alveolar adenomas occurring after repeated intratracheal instillation of ITO to hamsters have to be interpreted as treatment-related. In vitro and in vivo studies on the formation of reactive oxygen species suggest epigenetic effects as cause of the lung tumor development. Repeated intratracheal instillation of ITO to hamsters slightly affected the male sexual organs, which might be interpreted as a secondary effect of the lung damage. Epidemiological and medical surveillance studies, serum/blood indium levels in workers as well as data on the exposure to airborne indium concentrations indicate a need for measures to reduce exposure at ITO workplaces.

Applications and toxicity of graphene family nanomaterials and their composites

Graphene has attracted much attention of scientific community due to its enormous potential in different fields, including medical sciences, agriculture, food safety, cancer research, and tissue engineering. The potential for widespread human exposure raises safety concerns about graphene and its derivatives, referred to as graphene family nanomaterials (GFNs). Due to their unique chemical and physical properties, graphene and its derivatives have found important places in their respective application fields, yet they are being found to have cytotoxic and genotoxic effects too. Since the discovery of graphene, a number of researches are being conducted to find out the toxic potential of GFNs to different cell and animal models, finding their suitability for being used in new and varied innovative fields. This paper presents a systematic review of the research done on GFNs and gives an insight into the mode and action of these nanosized moieties. The paper also emphasizes on the recent and up-to-date developments in research on GFNs and their nanocomposites for their toxic effects.