Oxidative stress-induced cytotoxic and genotoxic effects of nano-sized titanium dioxide particles in human HaCaT keratinocytes

Environmental risk induced by TiO2 dispersions in waters and sediments: a case study

A southern Italian area that is characterized by large outcrops of rocks that are rich in titanium oxide (TiO2) phases were investigated to determine the mineralogical risk induced by the natural dispersion of TiO2 minerals. Rock, sediment and surface water samples were collected to determine the physicochemical and mineralogical factors (i.e., size distribution, morphology and alteration) indicative of potential TiO2 toxicity. X-ray diffraction data suggested that titanium oxides were present as rutile and anatase. Scanning electron microscopy images showed elongated TiO2 morphologies; fibres were found as either isolated or embedded/enclosed in flake-like phyllosilicates. The concentration of fibres in stream water ranged from 1.7 to 4.6 million fibres per litre. The highest fibre amounts in the sediments were in the <8-µm fraction, while single fibres were primarily concentrated in the <2-µm fraction. The results indicate that titanium oxide minerals represent a natural source of environmental risk and that the geomineralogical characterization of rich TiO2 areas is indispensable for understanding their geoavailability, dispersion and distribution.

Cerium oxide nanoparticles, combining antioxidant and UV shielding properties, prevent UV-induced cell damage and mutagenesis

Efficient inorganic UV shields, mostly based on refracting TiO2 particles, have dramatically changed the sun exposure habits. Unfortunately, health concerns have emerged from the pro-oxidant photocatalytic effect of UV-irradiated TiO2, which mediates toxic effects on cells. Therefore, improvements in cosmetic solar shield technology are a strong priority. CeO2 nanoparticles are not only UV refractors but also potent biological antioxidants due to the surface 3+/4+ valency switch, which confers anti-inflammatory, anti-ageing and therapeutic properties. Herein, UV irradiation protocols were set up, allowing selective study of the extra-shielding effects of CeO2vs. TiO2 nanoparticles on reporter cells. TiO2 irradiated with UV (especially UVA) exerted strong photocatalytic effects, superimposing their pro-oxidant, cell-damaging and mutagenic action when induced by UV, thereby worsening the UV toxicity. On the contrary, irradiated CeO2 nanoparticles, via their Ce(3+)/Ce(4+) redox couple, exerted impressive protection on UV-treated cells, by buffering oxidation, preserving viability and proliferation, reducing DNA damage and accelerating repair; strikingly, they almost eliminated mutagenesis, thus acting as an important tool to prevent skin cancer. Interestingly, CeO2 nanoparticles also protect cells from the damage induced by irradiated TiO2, suggesting that these two particles may also complement their effects in solar lotions. CeO2 nanoparticles, which intrinsically couple UV shielding with biological and genetic protection, appear to be ideal candidates for next-generation sun shields.

Assessment of cytotoxicity and oxidative stress induced by titanium oxide nanoparticles on Chinook salmon cells

Titanium oxide nanoparticles (TiO2 NPs) have received wide attention in diverse application, but the potential impact of these nanomaterials on the environment, aquatic life and especially on fish cell lines is lacking. The present study aimed to investigate the cytotoxicity and oxidative stress induced by TiO2 NPs on Chinook salmon cells derived from Oncorhynchus tshawytscha embryos (CHSE-214). The The MTT [3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazoliumbromide] and neutral red (NR) assays in CHSE-214 cells exposed to TiO2 NPs revealed concentration-dependent cytotoxic effect in the range of 10 to 60 μg/ml for 24 h. CHSE-214 cells exposed to TiO2 NPs (10-60 μg/ml) exhibited significant decline in superoxide dismutase (SOD), catalase (CAT) glutathione (GSH) content and increased lipid peroxidation (LPO) in a concentration-dependent manner. TiO2 NPs induced cytotoxicity and oxidative stress in CHSE-214 cells which serve as a base line studies for future studies.

Comparative toxicities of bismuth oxybromide and titanium dioxide exposure on human skin keratinocyte cells

Nano-sized bismuth oxybromide (BiOBr) particles are being considered for applications within the semiconductor industry. However, little is known about their potential impact on human health. In this study, we comparatively investigated the cytotoxicity of BiOBr and titanium dioxide (TiO2) nanoparticles (NPs) using human skin keratinocyte cell line (HaCaT) as a research model. Results indicate that lamellar-shaped BiOBr (length: 200 nm, width: 150 nm, and an average thickness: around 15 nm) has less toxic effects on cell viability and intracellular organelles than TiO2 (P25) NPs. BiOBr mainly induced late cell apoptosis, while for TiO2, both early apoptosis and late apoptosis were involved. Cell cycle arrest was found in cells on both NPs exposure, and more prominent in TiO2-treated cells. More cellular uptake was achieved after TiO2 exposure, particularly at 10 μg mL(-1), presence of TiO2 resulted in more than 2-fold increase in cellular granularity compared with BiOBr. Furthermore, TiO2 had a high potential to generate intracellular reactive oxygen species (ROS) in cells, where a 2.7-fold increase in TiO2 group and 2.0-fold increase in BiOBr group at the same concentration of 25 μg mL(-1). Higher cellular uptake and ROS stimulation should contribute to the more hazards of TiO2 than BiOBr NPs. This knowledge is a crucial component in the environmental and human hazard assessment of BiOBr and TiO2 NPs.

Titanium Dioxide Nanoparticle Penetration into the Skin and Effects on HaCaT Cells

Titanium dioxide nanoparticles (TiO₂NPs) suspensions (concentration 1.0 g/L) in synthetic sweat solution were applied on Franz cells for 24 h using intact and needle-abraded human skin. Titanium content into skin and receiving phases was determined. Cytotoxicity (MTT, AlamarBlue^® and propidium iodide, PI, uptake assays) was evaluated on HaCat keratinocytes after 24 h, 48 h, and seven days of exposure. After 24 h of exposure, no titanium was detectable in receiving solutions for both intact and damaged skin. Titanium was found in the epidermal layer after 24 h of exposure (0.47 ± 0.33 μg/cm²) while in the dermal layer, the concentration was below the limit of detection. Damaged skin, in its whole, has shown a similar concentration (0.53 ± 0.26 μg/cm²). Cytotoxicity studies on HaCaT cells demonstrated that TiO₂NPs induced cytotoxic effects only at very high concentrations, reducing cell viability after seven days of exposure with EC₅₀s of 8.8 × 10⁻⁴ M (MTT assay), 3.8 × 10⁻⁵ M (AlamarBlue^® assay), and 7.6 × 10⁻⁴ M (PI uptake, index of a necrotic cell death). Our study demonstrated that TiO₂NPs cannot permeate intact and damaged skin and can be found only in the stratum corneum and epidermis. Moreover, the low cytotoxic effect observed on human HaCaT keratinocytes suggests that these nano-compounds have a potential toxic effect at the skin level only after long-term exposure.

ZnO Nanoparticles Treatment Induces Apoptosis by Increasing Intracellular ROS Levels in LTEP-a-2 Cells

Owing to the wide use of novel nanoparticles (NPs) such as zinc oxide (ZnO) in all aspects of life, toxicological research on ZnO NPs is receiving increasing attention in these days. In this study, the toxicity of ZnO NPs in a human pulmonary adenocarcinoma cell line LTEP-a-2 was tested in vitro. Log-phase cells were exposed to different levels of ZnO NPs for hours, followed by colorimetric cell viability assay using tetrazolium salt and cell survival rate assay using trypan blue dye. Cell morphological changes were observed by Giemsa staining and light microscopy. Apoptosis was detected by using fluorescence microscopy and caspase-3 activity assay. Both intracellular reactive oxygen species (ROS) and reduced glutathione (GSH) were examined by a microplate-reader method. Results showed that ZnO NPs (≥ 0.01 μg/mL) significantly inhibited proliferation (P < 0.05) and induced substantial apoptosis in LTEP-a-2 cells after 4 h of exposure. The intracellular ROS level rose up to 30-40% corresponding to significant depletion (approximately 70-80%) in GSH content in LTEP-a-2 cells (P < 0.05), suggesting that ZnO NPs induced apoptosis mainly through increased ROS production. This study elucidates the toxicological mechanism of ZnO NPs in human pulmonary adenocarcinoma cells and provides reference data for application of nanomaterials in the environment.

Analysis of cytotoxic effects of silver nanoclusters on human peripheral blood mononuclear cells 'in vitro'

The antimicrobial properties of silver nanoparticles (AgNPs) have made these particles one of the most used nanomaterials in consumer products. Therefore, an understanding of the interactions (unwanted toxicity) between nanoparticles and human cells is of significant interest. The aim of this study was to assess the in vitro cytotoxicity effects of silver nanoclusters (AgNC, < 2 nm diameter) on peripheral blood mononuclear cells (PBMC). Using flow cytometry and comet assay methods, we demonstrate that exposure of PBMC to AgNC induced intracellular reactive oxygen species (ROS) generation, DNA damage and apoptosis at 3, 6 and 12 h, with a dose-dependent response (0.1, 1, 3, 5 and 30 µg ml(-1)). Advanced electron microscopy imaging of complete and ultrathin-sections of PBMC confirmed the cytotoxic effects and cell damage caused by AgNC. The present study showed that AgNC produced without coating agents induced significant cytotoxic effects on PBMC owing to their high aspect ratio and active surface area, even at much lower concentrations (<1 µg ml(-1)) than those applied in previous studies, resembling what would occur under real exposure conditions to nanosilver-functionalized consumer products.

Electronic platform for real-time multi-parametric analysis of cellular behavior post-exposure to single-walled carbon nanotubes

Single-walled carbon nanotubes (SWCNTs) implementation in a variety of biomedical applications from bioimaging, to controlled drug delivery and cellular-directed alignment for muscle myofiber fabrication, has raised awareness of their potential toxicity. Nanotubes structural aspects which resemble asbestos, as well as their ability to induce cyto and genotoxicity upon interaction with biological systems by generating reactive oxygen species or inducing membrane damage, just to name a few, have led to focused efforts aimed to assess associated risks prior their user implementation. In this study, we employed a non-invasive and real-time electric cell impedance sensing (ECIS) platform to monitor behavior of lung epithelial cells upon exposure to a library of SWCNTs with user-defined physico-chemical properties. Using the natural sensitivity of the cells, we evaluated SWCNT-induced cellular changes in relation to cell attachment, cell-cell interactions and cell viability respectively. Our methods have the potential to lead to the development of standardized assays for risk assessment of other nanomaterials as well as risk differentiation based on the nanomaterials surface chemistry, purity and agglomeration state.

An in vitro study on the cytotoxicity of bismuth oxychloride nanosheets in human HaCaT keratinocytes

As an emerging nanomaterial, bismuth oxychloride (BiOCl) has attracted explosive interests in diverse areas. However, how it interfaces with biological systems, particularly its interaction with human cells and the resulting effects are completely unknown. In this paper, the cytotoxicity of BiOCl nanosheets (NSs) was investigated toward a human skin derived cell line (HaCaT). It was found that BiOCl-NSs had no cytotoxicity at low concentrations (<0.5 µg/mL), whereas higher concentrations (5-100 µg/mL) of BiOCl-NSs could trigger toxic effects on HaCaT cells, with changes in cell morphology and impairment of intracellular structures (mitochondria and cytoskeleton). BiOCl-NSs also led to cell apoptosis and cells cycle arrest in G0/G1 phase. Flow cytometric data showed that BiOCl-NSs were effectively incorporated into HaCaT cells. Transmission electron microscope (TEM) images further revealed that BiOCl-NSs sequestered in the lysosomes, mitochondria, nuclei, and vesicles. Results of DCFH-DA assay and nutritional antioxidant N-acetylcysteine (NAC) experiments suggested that an oxidative stress mechanism was involved in the cytotoxic effects of BiOCl-NSs. Taken together, this work represents the first study on the behavior of BiOCl-NSs on human cells, and constitutes the first and essential step for the risk assessment of BiOCl nanomaterials.

Genotoxic and cell-transforming effects of titanium dioxide nanoparticles

The in vitro genotoxic and the soft-agar anchorage independent cell transformation ability of titanium dioxide nanoparticles (nano-TiO2) and its microparticulated form has been evaluated in human embryonic kidney (HEK293) and in mouse embryonic fibroblast (NIH/3T3) cells. Nano-TiO2 of two different sizes (21 and 50 nm) were used in this study. The comet assay, with and without the use of FPG enzyme, the micronucleus assay and the soft-agar colony assay were used. For both the comet assay and the frequency of micronuclei a statistically significant induction of DNA damage, was observed at the highest dose tested (1000 µg/mL). No oxidative DNA damage induction was observed when the comet assay was complemented with the use of FPG enzyme. Furthermore, long-term exposure to nano-TiO2 has also proved to induce cell-transformation promoting cell-anchorage independent growth in soft-agar. Results were similar for the two nano-TiO2 sizes. Negative results were obtained when the microparticulated form of TiO2 was tested, indicating the existence of important differences between the microparticulated and nanoparticulated forms. As a conclusion it should be indicated that the observed genotoxic/tranforming effects were only detected at the higher dose tested (1000 µg/mL) what play down the real risk of environmental exposures to this nanomaterial.

Titanium nanoparticle inhalation induces renal fibrosis in mice via an oxidative stress upregulated transforming growth factor-β pathway

Titanium dioxide nanoparticles (Nano-TiO2) are gradually being used extensively in clinical settings, industry, and daily life. Accumulation studies showed that Nano-TiO2 exposure is able to cause injuries in various animal organs, including the lung, liver, spleen, and kidney. However, it remains unclear whether exposure of Nano-TiO2 by inhalation causes renal fibrosis. Here, we investigated the role of reactive oxygen species (ROS)/reactive nitrogen species (RNS) related signaling molecules in chronic renal damage after Nano-TiO2 inhalation in mice. Mice were treated with Nano-TiO2 (0.1, 0.25, and 0.5 mg/week) or microparticle-TiO2 (0.5 mg/week) by nonsurgical intratracheal instillation for 4 weeks. The results showed that Nano-TiO2 inhalation increased renal pathological changes in a dose-dependent manner. No renal pathological changes were observed in microparticle-TiO2-instilled mice. Nano-TiO2 (0.5 mg/week) possessed the ability to precipitate in the kidneys, determined by transmission electron microscopy and increased serum levels of blood urea nitrogen. The expressions of markers of ROS/RNS and renal fibrosis markers, including nitrotyrosine, inducible nitric oxide synthase, hypoxia inducible factor-1α (HIF-1α), heme oxygenase 1, transforming growth factor-β (TGFβ), and collagen I, determined by immunohistochemical staining were increased in the kidneys. Furthermore, Nano-TiO2-induced renal injury could be mitigated by iNOS inhibitor aminoguanidine and ROS scavenger N-acetylcysteine treatment in transcription level. The in vitro experiments showed that Nano-TiO2 significantly and dose-dependently increased the ROS production and the expressions of HIF-1α and TGFβ in human renal proximal tubular cells, which could be reversed by N-acetylcysteine treatment. Taken together, these results suggest Nano-TiO2 inhalation might induce renal fibrosis through a ROS/RNS-related HIF-1α-upregulated TGF-β signaling pathway.

Impact of photocatalysis on fungal cells: depiction of cellular and molecular effects on Saccharomyces cerevisiae

We have investigated the antimicrobial effects of photocatalysis on the yeast model Saccharomyces cerevisiae. To accurately study the antimicrobial mechanisms of the photocatalytic process, we focused our investigations on two questions: the entry of the nanoparticles in treated cells and the fate of the intracellular environment. Transmission electronic microscopy did not reveal any entry of nanoparticles within the cells, even for long exposure times, despite degradation of the cell wall space and deconstruction of cellular compartments. In contrast to proteins located at the periphery of the cells, intracellular proteins did not disappear uniformly. Disappearance or persistence of proteins from the pool of oxidized intracellular isoforms was not correlated to their functions. Altogether, our data suggested that photocatalysis induces the establishment of an intracellular oxidative environment. This hypothesis was sustained by the detection of an increased level of superoxide ions (O2°(-)) in treated cells and by greater cell cultivability for cells expressing oxidant stress response genes during photocatalytic exposure. The increase in intracellular ROS, which was not connected to the entry of nanoparticles within the cells or to a direct contact with the plasma membrane, could be the result of an imbalance in redox status amplified by chain reactions. Moreover, we expanded our study to other yeast and filamentous fungi and pointed out that, in contrast to the laboratory model S. cerevisiae, some environmental strains are very resistant to photocatalysis. This could be related to the cell wall composition and structure.

UVB irradiation enhances TiO2 nanoparticle-induced disruption of calcium homeostasis in human lens epithelial cells

Currently, titanium dioxide nanoparticles (TiO2 NPs) have been widely used in various applications including cosmetics, food additives and biomedicine. However, there are few reports available using TiO2 NPs to treat ocular diseases. Posterior capsular opacification (PCO) is the most frequent complication after cataract surgery, which is induced by the proliferation and migration of lens epithelial cells. Thus, inhibiting the proliferation of lens epithelial cells will efficiently reduce the occurrence of PCO. In this study, we investigated the effects of TiO2 NPs on HLE B-3 cells with or without ultraviolet B (UVB) irradiation in vitro. We found that TiO2 NPs can inhibit HLE B-3 cell growth, cause the elevation of intracellular [Ca(2+)], produce excessive reactive oxygen species (ROS), further reduce Ca(2+)-ATPase activity and decrease the expression of plasma membrane calcium ATPase 1 (PMCA1), finally disrupt the intracellular calcium homeostasis and induce cell damage. Importantly, UVB irradiation can apparently enhance these effects on HLE B-3 cells in the presence of TiO2 NPs. Taken together, the generation of excessive ROS and the disruption of intracellular calcium homeostasis may be both involved in TiO2 nanoparticle-induced HLE B-3 cell damage under UVB irradiation.

Titanium dioxide nanoparticles induce strong oxidative stress and mitochondrial damage in glial cells

Titanium dioxide nanoparticles (TiO2 NPs) are widely used in the chemical, electrical, and electronic industries. TiO2 NPs can enter directly into the brain through the olfactory bulb and can be deposited in the hippocampus region; therefore, we determined the toxic effect of TiO2 NPs on rat and human glial cells, C6 and U373, respectively. We evaluated some events related to oxidative stress: (1) redox-signaling mechanisms by oxidation of 2',7'-dichlorodihydrofluorescein diacetate; (2) peroxidation of lipids by cis-parinaric acid; (3) antioxidant enzyme expression by PCR in real time; and (4) mitochondrial damage by MitoTracker Green FM staining and Rh123. TiO2 NPs induced a strong oxidative stress in both glial cell lines by mediating changes in the cellular redox state and lipid peroxidation associated with a rise in the expression of glutathione peroxidase, catalase, and superoxide dismutase 2. TiO2 NPs also produced morphological changes, damage of mitochondria, and an increase in mitochondrial membrane potential, indicating toxicity. TiO2 NPs had a cytotoxic effect on glial cells; however, more in vitro and in vivo studies are required to ascertain that exposure to TiO2 NPs can cause brain injury and be hazardous to health.

Effects of silica and titanium oxide particles on a human neural stem cell line: morphology, mitochondrial activity, and gene expression of differentiation markers

Several in vivo studies suggest that nanoparticles (smaller than 100 nm) have the ability to reach the brain tissue. Moreover, some nanoparticles can penetrate into the brains of murine fetuses through the placenta by intravenous administration to pregnant mice. However, it is not clear whether the penetrated nanoparticles affect neurogenesis or brain function. To evaluate its effects on neural stem cells, we assayed a human neural stem cell (hNSCs) line exposed in vitro to three types of silica particles (30 nm, 70 nm, and <44 μm) and two types of titanium oxide particles (80 nm and < 44 μm). Our results show that hNSCs aggregated and exhibited abnormal morphology when exposed to the particles at concentrations ≥ 0.1 mg/mL for 7 days. Moreover, all the particles affected the gene expression of Nestin (stem cell marker) and neurofilament heavy polypeptide (NF-H, neuron marker) at 0.1 mg/mL. In contrast, only 30-nm silica particles at 1.0 mg/mL significantly reduced mitochondrial activity. Notably, 30-nm silica particles exhibited acute membrane permeability at concentrations ≥62.5 μg/mL in 24 h. Although these concentrations are higher than the expected concentrations of nanoparticles in the brain from in vivo experiments in a short period, these thresholds may indicate the potential toxicity of accumulated particles for long-term usage or continuous exposure.

Cell uptake and oral absorption of titanium dioxide nanoparticles

Large efforts are invested on the development of in vitro tests to evaluate nanomaterial (NM) toxicity. In order to assess the relevance of the adverse effects identified in in vitro toxicity tests a thorough understanding of the biokinetics of NMs is critical. We used different in vitro and in vivo test methods to evaluate cell uptake and oral absorption of titanium dioxide nanoparticles (TiO2 NPs). These NPs were readily uptaken by A549 cells (carcinomic human alveolar basal epithelial cells) in vitro. Such rapid uptake contrasted with a very low oral absorption in a differentiated Caco-2 monolayer system (human epithelial colorectal adenocarcinoma cells) and after oral gavage administration to rats. In this oral study, no significant increase in the levels of titanium was recorded by ICP-MS in any of the tissues evaluated (including among other: small intestine, Peyer's patches, mesenteric lymph nodes, liver, and spleen). No NPs were observed by TEM in sections of the small intestine, except for several particles in the cytoplasm of a cell from a Peyer's Patch area. The observation of NPs in Peyer's Patch suggests that the Caco-2 monolayer system is likely to underestimate the potential for oral absorption of NPs and that the model could be improved by including M-cells in co-culture.

Mechanistic characterization of titanium dioxide nanoparticle-induced toxicity using electron spin resonance

Titanium dioxide nanoparticles (TiO₂ NPs) are one of the most widely used nanomaterials that have been manufactured worldwide and applied in different commercial realms. The well-recognized ability of TiO₂ to promote the formation of reactive oxygen species (ROS) has been extensively studied as one of the important mechanisms underlying TiO₂ NPs toxicity. As the “gold standard” method to quantify and identify ROS, electron spin resonance (ESR) spectroscopy has been employed in many studies aimed at evaluating TiO₂ NPs safety. This review aims to provide a thorough discussion of current studies using ESR as the primary method to unravel the mechanism of TiO₂ NPs toxicity. ESR spin label oximetry and immune-spin trapping techniques are also briefly introduced, because the combination of spin trapping/labeling techniques offers a promising tool for studying the oxidative damage caused by TiO₂ NPs.

Singlet oxygen plays a key role in the toxicity and DNA damage caused by nanometric TiO2 in human keratinocytes

Nanometric TiO2 has been reported to be cytotoxic and genotoxic in different in vitro models when activated by UV light. However, a clear picture of the species mediating the observed toxic effects is still missing. Here, a nanometric TiO2 powder has been modified at the surface to completely inhibit its photo-catalytic activity and to inhibit the generation of all reactive species except for singlet oxygen. The prepared powders have been tested for their ability to induce strand breaks in plasmid DNA and for their cytotoxicity and genotoxicity toward human keratinocyte (HaCaT) cells (100-500 μg mL(-1), 15 min UVA/B exposure at 216-36 mJ m(-2) respectively). The data reported herein indicate that the photo-toxicity of TiO2 is mainly triggered by particle-derived singlet oxygen. The data presented herein contribute to the knowledge of structure-activity relationships which are needed for the design of safe nanomaterials.

Use patterns of leave-on personal care products among Swiss-German children, adolescents, and adults

In order to model exposure to ingredients contained in personal care products (PCPs) and assess their potential risks to human health, access to reliable PCP use data, including co-use patterns, is essential. A postal questionnaire survey was conducted to determine the use patterns of eight leave-on PCP categories among the German-speaking population of Switzerland (N = 1,196; ages 0–97 years), providing for the first time in Europe PCP use data for children <12 years of age. The majority of respondents (99%) reported having used at least one of the investigated PCP categories in the past year. Co-use of two or more PCP categories at the same time was common and more complex amongst adults. Regular use of face cream and body lotion was very high in the youngest group of children aged 0–4 years (more than 79% respondents) who may be more vulnerable to certain adverse effects of some PCP ingredients. A comparison with previously collected information on PCP use patterns in Germany and the Netherlands indicates differences in PCP use patterns among European consumers and suggests that surrogate PCP use data from other countries must be used with caution. This work extends the existing knowledge of PCP use patterns and will be useful for new exposure assessments for ingredients contained in PCPs used by the young consumers.

Mitochondrial injury induced by nanosized titanium dioxide in A549 cells and rats

The nanosized titanium dioxide (nano-TiO2) is an important nanoscale compound applied in many different fields because of its superior performance. Here, an anatase nano-TiO2 showed cytotoxicity in a dosage-dependent manner, which was in accordance with changes of A549 cell ultrastructure, A549 cell viability and intracellular ATP level. The lungs of rats treated with single intratracheal instillation of nano-TiO2 were injured, which was demonstrated by changes of alveolar epithelial cell ultrastructure, lung tissue pathology and lung tissue MDA level. The results of this study indicated that nano-TiO2 should be related to the generation of intracellular reactive oxygen species (ROS), which injured mitochondria and prevented the synthesis of ATP. The cells were approaching to apoptosis eventually. In macroscopic view, the lungs inevitably suffered.

Assessment of in vitro cellular responses of monocytes and keratinocytes to tannic acid modified silver nanoparticles

Hydrolyzable tannins are known to exhibit diverse biological effects, which can be used in combination with silver nanoparticles (AgNPs). In this study, we tested toxic and inflammatory properties of tannic-acid modified 13, 33, 46 nm and unmodified 10-65 nm AgNPs using murine 291.03C keratinocyte and RAW 264.7 monocyte cell lines. Both cell lines exposed for 24h to 1-10 μg/ml of 13 nm, 33 nm, 46 nm and unmodified AgNPs showed dose-dependent toxicity and decreased cell proliferation. Only small-sized AgNPs induced production of ROS by monocytes, but not keratinocytes. Monocytes internalized large aggregates of 33, 46 nm and 10-65 nm AgNPs in cytoplasmic vacuoles, whereas keratinocytes accumulated less particles. AgNPs of 13 nm were localized ubiquitously within both cell types. The tested AgNPs strongly down-regulated production of tumor necrosis factor-α (TNF-α) by monocytes, whereas keratinocytes exposed to AgNPs showed an opposite effect. Unmodified but not tannic acid-modified AgNPs increased production of the pro-inflammatory MCP-1 by monocytes and keratinocytes. In summary, low inflammatory potential and lack of ROS production by tannic-acid modified AgNPs sized above 30 nm suggests that tannic acid modification of large silver nanoparticles may help to increase AgNPs biosafety.

Characterization and preliminary toxicity assay of nano-titanium dioxide additive in sugar-coated chewing gum

Nanotechnology shows great potential for producing food with higher quality and better taste through including new additives, improving nutrient delivery, and using better packaging. However, lack of investigations on safety issues of nanofood has resulted in public fears. How to characterize engineered nanomaterials in food and assess the toxicity and health impact of nanofood remains a big challenge. Herein, a facile and highly reliable separation method of TiO2 particles from food products (focusing on sugar-coated chewing gum) is reported, and the first comprehensive characterization study on food nanoparticles by multiple qualitative and quantitative methods is provided. The detailed information on nanoparticles in gum includes chemical composition, morphology, size distribution, crystalline phase, particle and mass concentration, surface charge, and aggregation state. Surprisingly, the results show that the number of food products containing nano-TiO2 (<200 nm) is much larger than known, and consumers have already often been exposed to engineered nanoparticles in daily life. Over 93% of TiO2 in gum is nano-TiO2 , and it is unexpectedly easy to come out and be swallowed by a person who chews gum. Preliminary cytotoxicity assays show that the gum nano-TiO2 particles are relatively safe for gastrointestinal cells within 24 h even at a concentration of 200 μg mL(-1) . This comprehensive study demonstrates accurate physicochemical property, exposure, and cytotoxicity information on engineered nanoparticles in food, which is a prerequisite for the successful safety assessment of nanofood products.

Titanium dioxide nanoparticles: a review of current toxicological data

Titanium dioxide (TiO2) nanoparticles (NPs) are manufactured worldwide in large quantities for use in a wide range of applications. TiO2 NPs possess different physicochemical properties compared to their fine particle (FP) analogs, which might alter their bioactivity. Most of the literature cited here has focused on the respiratory system, showing the importance of inhalation as the primary route for TiO2 NP exposure in the workplace. TiO2 NPs may translocate to systemic organs from the lung and gastrointestinal tract (GIT) although the rate of translocation appears low. There have also been studies focusing on other potential routes of human exposure. Oral exposure mainly occurs through food products containing TiO2 NP-additives. Most dermal exposure studies, whether in vivo or in vitro, report that TiO2 NPs do not penetrate the stratum corneum (SC). In the field of nanomedicine, intravenous injection can deliver TiO2 nanoparticulate carriers directly into the human body. Upon intravenous exposure, TiO2 NPs can induce pathological lesions of the liver, spleen, kidneys, and brain. We have also shown here that most of these effects may be due to the use of very high doses of TiO2 NPs. There is also an enormous lack of epidemiological data regarding TiO2 NPs in spite of its increased production and use. However, long-term inhalation studies in rats have reported lung tumors. This review summarizes the current knowledge on the toxicology of TiO2 NPs and points out areas where further information is needed.

Titanium dioxide nanoparticles: a review of current toxicological data

Titanium dioxide (TiO2) nanoparticles (NPs) are manufactured worldwide in large quantities for use in a wide range of applications. TiO2 NPs possess different physicochemical properties compared to their fine particle (FP) analogs, which might alter their bioactivity. Most of the literature cited here has focused on the respiratory system, showing the importance of inhalation as the primary route for TiO2 NP exposure in the workplace. TiO2 NPs may translocate to systemic organs from the lung and gastrointestinal tract (GIT) although the rate of translocation appears low. There have also been studies focusing on other potential routes of human exposure. Oral exposure mainly occurs through food products containing TiO2 NP-additives. Most dermal exposure studies, whether in vivo or in vitro, report that TiO2 NPs do not penetrate the stratum corneum (SC). In the field of nanomedicine, intravenous injection can deliver TiO2 nanoparticulate carriers directly into the human body. Upon intravenous exposure, TiO2 NPs can induce pathological lesions of the liver, spleen, kidneys, and brain. We have also shown here that most of these effects may be due to the use of very high doses of TiO2 NPs. There is also an enormous lack of epidemiological data regarding TiO2 NPs in spite of its increased production and use. However, long-term inhalation studies in rats have reported lung tumors. This review summarizes the current knowledge on the toxicology of TiO2 NPs and points out areas where further information is needed.

Comparative study on effects of two different types of titanium dioxide nanoparticles on human neuronal cells

Titanium dioxide (TiO2) are among most frequently used nanoparticles (NPs). They are present in a variety of consumer products, including food industry in which they are employed as an additive. The potential toxic effects of these NPs on mammal cells have been extensively studied. However, studies regarding neurotoxicity and specific effects on neuronal systems are very scarce and, to our knowledge, no studies on human neuronal cells have been reported so far. Therefore, the main objective of this work was to investigate the effects of two types of TiO₂ NPs, with different crystalline structure, on human SHSY5Y neuronal cells. After NPs characterization, a battery of assays was performed to evaluate the viability, cytotoxicity, genotoxicity and oxidative damage in TiO₂ NP-exposed SHSY5Y cells. Results obtained showed that the behaviour of both types of NPs resulted quite comparable. They did not reduce the viability of neuronal cells but were effectively internalized by the cells and induced dose-dependent cell cycle alterations, apoptosis by intrinsic pathway, and genotoxicity not related with double strand break production. Furthermore, all these effects were not associated with oxidative damage production and, consequently, further investigations on the specific mechanisms underlying the effects observed in this study are required.

Effect of treatment media on the agglomeration of titanium dioxide nanoparticles: impact on genotoxicity, cellular interaction, and cell cycle

The widespread use of titanium dioxide (TiO2) nanoparticles in consumer products increases the probability of exposure to humans and the environment. Although TiO2 nanoparticles have been shown to induce DNA damage (comet assay) and chromosome damage (micronucleus assay, MN) in vitro, no study has systematically assessed the influence of medium composition on the physicochemical characteristics and genotoxicity of TiO2 nanoparticles. We assessed TiO2 nanoparticle agglomeration, cellular interaction, induction of genotoxicity, and influence on cell cycle in human lung epithelial cells using three different nanoparticle-treatment media: keratinocyte growth medium (KGM) plus 0.1% bovine serum albumin (KB); a synthetic broncheoalveolar lavage fluid containing PBS, 0.6% bovine serum albumin and 0.001% surfactant (DM); or KGM with 10% fetal bovine serum (KF). The comet assay showed that TiO2 nanoparticles induced similar amounts of DNA damage in all three media, independent of the amount of agglomeration, cellular interaction, or cell-cycle changes measured by flow cytometry. In contrast, TiO2 nanoparticles induced MN only in KF, which is the medium that facilitated the lowest amount of agglomeration, the greatest amount of nanoparticle cellular interaction, and the highest population of cells accumulating in S phase. These results with TiO2 nanoparticles in KF demonstrate an association between medium composition, particle uptake, and nanoparticle interaction with cells, leading to chromosomal damage as measured by the MN assay.

Exposure to titanium dioxide nanoparticles induces autophagy in primary human keratinocytes

Understanding the mechanisms of cell-nanomaterial interactions is vital in harnessing the potential of using nanomaterials in biomedical applications. By immuno-labeling of LC3 and TEM analysis, it is found that titanium dioxide nanoparticles are internalized by human keratinocytes and induce autophagy. Autophagy appears to play a cytoprotective role in response to toxicity influence exerted by the nanoparticles.

Ganoderma tsugae hepatoprotection against exhaustive exercise-induced liver injury in rats

Several studies have been shown that accelerated apoptosis is involved in post-exercise lymphocytopenia and tissue damage after high-intensity exercise. Ganoderma tsugae (GT) is one of the well-known medicinal mushrooms that possess various pharmacological functions. This mushroom has traditionally been used for health promotion purposes. This study investigates the hepatoprotective effects of GT on exhaustive exercise-induced liver damage. Twenty-four male Sprague-Dawley rats were randomly divided into four groups and designated as exhaustive exercise only (E), exhaustive exercise with low dosage (EL), medium dosage (EM) and high dosage (EH) GT at 0, 0.1875, 0.9375 and 1.875 g/kg/day, respectively. After 30 days all rats were euthanized immediately after an exhaustive running challenge on a motorized treadmill. The rat livers were immediately harvested. Evidence of apoptotic liver cell death was revealed using terminal deoxynucleotidyl transferase dUTP nick end labeling (TUNEL) assay and caspases mediated cascade events. DNA fragmentation, an apoptosis process, can be examined using TUNEL assay. A few TUNEL-positive hepatocytes, compared to the exercise only group, were observed in the livers from exhaustive animals supplemented with GT. Immunoblot analysis also showed that caspase-6-mediated specific cleavage of lamin A/C was increased significantly in the livers of group E, but was significantly decreased in the EM and EH groups. Our observations demonstrate that GT possesses anti-apoptotic and hepatoprotective potential after exhaustive exercise.

Spectral cross-correlation as a supervised approach for the analysis of complex Raman datasets: the case of nanoparticles in biological cells

Spectral cross-correlation is introduced as a methodology to identify the presence and subcellular distribution of nanoparticles in cells. Raman microscopy is employed to spectroscopically image biological cells previously exposed to polystyrene nanoparticles, as a model for the study of nano-bio interactions. The limitations of previously deployed strategies of K-means clustering analysis and principal component analysis are discussed and a novel methodology of spectral cross-correlation analysis is introduced and compared with the performance of classical least squares analysis, in both unsupervised and supervised modes. The previous study demonstrated the feasibility of using Raman spectroscopy to map cells and identify polystyrene nanoparticles in a lipid rich environment, which is suggestive of the membrane rich endoplasmic reticulum. However, short comings in identification of all nanoparticle signatures in the cell using K-means clustering are apparent, as highlighted by principal component analysis of the identified clusters which demonstrates that K-means clustering does not identify all regions where spectral signatures of the nanoparticles are evident. Thus, two more sophisticated analytical approaches to the extraction of the nanoparticle signatures from the Raman spectral datasets, namely classical least squares analysis and cross-correlation analysis, were employed and are demonstrated to improve the identification of spectroscopic signatures characteristic of polystyrene nanoparticles in a cellular environment. Additionally, to investigate the local biochemical environment in which the nanoparticles are trafficked, a pure spectrum of 3-sn-phosphatidyl ethanolamine was cross-correlated against the Raman dataset, further suggesting the particles are indeed localized in a lipid rich environment. Furthermore, to demonstrate the robustness and versatility of the analysis method, a spectrum of pure RNA was used to demonstrate that a differentiation could be made between DNA of the nucleus and RNA of the nucleolus using the supervised spectral cross-correlation technique.

Small sizes of TiO2-NPs exhibit adverse effects at predicted environmental relevant concentrations on nematodes in a modified chronic toxicity assay system

In Caenorhabditis elegans, although acute toxicity of TiO(2) nanoparticles (TiO(2)-NPs) at high concentrations has been investigated, we still know little about chronic toxicity of TiO(2)-NPs. Our data here showed that acute TiO(2)-NPs exposure in the range of μg/L had no obviously adverse effects on nematodes, but the chronic toxicities of large sizes (60 nm and 90 nm) of TiO(2)-NPs in the range of μg/L were detected in nematodes in a modified chronic toxicity assay system. Moreover, chronic toxicities of small sizes (4 nm and 10nm) of TiO(2)-NPs in the range of ng/L were observed in nematodes with locomotion behavior and ROS production as endpoints. In nematodes chronically exposed to small sizes of TiO(2)-NPs at predicted environmental relevant concentrations, locomotion behavior was significantly (P<0.01) correlated with ROS production. Furthermore, treatment with antioxidants (ascorbate and N-acetyl-l-cysteine) inhibited both the induction of ROS production and the decrease of locomotion behaviors observed in nematodes chronically exposed to small sizes of TiO(2)-NPs at predicted environmental relevant concentrations. Therefore, chronic exposure to small sizes of TiO(2)-NPs at predicted environmental relevant concentrations can cause adverse effects on nematodes, and formation of such adverse effects may be largely due to the induction of oxidative stress.