A Lightweight and Low-Voltage-Operating Linear Actuator Based on the Electroactive Polymer Polypyrrole.

In recent decades, significant research efforts have been devoted to studying various types of actuators. Of particular interest are soft actuators based on electroactive polymers, which offer low operating voltage, light weight, and fast response. In this study, we demonstrate the feasibility of a soft linear actuator fabricated from polypyrrole (PPy), an electroactive polymer that is easy to synthesize, cost-effective, and biocompatible. By optimizing the polymerization conditions, the operation condition and environment, we were able to achieve improved and stable actuator performance. Furthermore, we developed a new actuator-contained component with a flexible counter electrode to build an actuator that operates in air. This approach enabled us to build small and lightweight actuators that operate in air, with a diameter of 5 mm, resembling artificial muscles. Our resulting miniaturized and integrated linear PPy-based actuators can be driven at low voltages (±1.5 V), making them suitable for use in various parts of the body. As such, this actuator holds significant potential for a wide range of applications in the fields of soft electronics, drug delivery, artificial organs, and muscles, as well as a component material for portable medical sensors and devices.

In Situ Electrical Monitoring of Methylated DNA Based on Its Conformational Change to G-Quadruplex Using a Solution-Gated Field-Effect Transistor.

Methylated DNA is not only a diagnostic but also a prognostic biomarker for early-stage cancer. However, sodium bisulfite sequencing as a "gold standard" method for detection of methylation markers has some drawbacks such as its time-consuming and labor-intensive procedures. Therefore, simple and reliable methods are required to analyze DNA sequences with or without methylated residues. Herein, we propose a simple and direct method for detecting DNA methylation through its conformation transition to G-quadruplex using a solution-gated field-effect transistor (SG-FET) without using labeled materials. The BCL-2 gene, which is involved in the development of various human tumors, contains G-rich segments and undergoes a conformational change to G-quadruplex depending on the K+ concentration. Stacked G-quadruplex strands move close to the SG-FET sensor surface, resulting in large electrical signals based on intrinsic molecular charges. In addition, a dense hydrophilic polymer brush is grafted using surface-initiated atom transfer radical polymerization onto the SG-FET sensor surface to reduce electrical noise based on nonspecific adsorption of interfering species. In particular, control of the polymer brush thickness induces electrical signals based on DNA molecular charges in the diffusion layer, according to the Debye length limit. A platform based on the SG-FET sensor with a well-defined polymer brush is suitable for in situ monitoring of methylated DNA and realizes a point-of-care device with a high signal-to-noise ratio and without the requirement for additional processes such as bisulfite conversion and polymerase chain reaction.

Quantitative kinetics of intracellular singlet oxygen generation using a fluorescence probe.

Singlet oxygen (1O2) is a type of reactive oxygen species involved in numerous physiological activities. We previously reported that 1O2-specific oxidation products are increased in patients with prediabetes, suggesting that measurement of 1O2 may be an important indicator of physiological and pathological conditions. The turnover in the generation and quenching of 1O2 is extremely rapid during biological activities owing to it high reactivity and short lifetime in solution. However, the dynamic changes in 1O2 generation in living cells have not been fully explored. In this study, we investigated whether the kinetics of 1O2 generation can be quantified using a far-red fluorescent probe for mitochondrial 1O2, Si-DMA, following addition of the 1O2 generator, endoperoxide, to mammalian cells. The kinetics of Si-DMA fluorescence intensity dose-dependently increased following treatment of mammalian living cells with endoperoxide. Alternatively, treatment with 1O2 quenchers decreased the fluorescence intensities following endoperoxide treatment. Our results indicate that the kinetics of intracellular 1O2 can be readily obtained using Si-DMA and time-lapse imaging, which provides new insights into the mechanism of 1O2 generation in mammalian cells and the exploration of 1O2 generators and quenchers.

Yuzu (Citrus junos Tanaka) Peel Attenuates Dextran Sulfate Sodium-induced Murine Experimental Colitis.

Ulcerative colitis is a well-known inflammatory bowel disease. Although there are drugs that are effective against this disease, the prevention and attenuation of ulcerative colitis by food rich in functional ingredients without side effects is desired because some drugs have side effects. In this study, we investigated the effects of yuzu (Citrus junos Tanaka), a citrus fruit native to northeast Asia, on a mouse dextran sulfate sodium (DSS)-induced colitis model. Mice given drinking water containing DSS showed significant weight loss, colon shortening, diarrhea, and visible fecal blood. In contrast, mice fed a diet containing 5% yuzu peel for 14 d before receiving DSS showed significant attenuation of these phenotypes. To clarify the mechanism underlying the attenuation, we investigated the anti-inflammatory and antioxidant effects of yuzu peel. We found that yuzu peel extract suppressed tumor necrosis factor-α (TNF-α) production in lipopolysaccharide (LPS)-stimulated mice and murine macrophage cell line through suppression of nuclear factor-κB (NF-κB) activation. In addition, we confirmed that yuzu peel extract had a moderate antioxidant effect. These results suggest that yuzu peel attenuates the pathologies of DSS-induced colitis by coordinately suppressing inflammation and oxidative stress against lipids in vivo.

Ascorbic acid prevents zinc oxide nanoparticle-induced intracellular oxidative stress and inflammatory responses.

Exposure to zinc oxide nanoparticles (ZnO NPs) promotes acute pulmonary toxicity through oxidative stress and inflammation. Furthermore, dissolved zinc from ZnO NPs induces the formation of intracellular reactive oxygen species (ROS). We previously reported that supplemental ascorbic acid (AA) inhibits ZnO NP-induced acute pulmonary toxicity in a rat model; however, the mechanism of this action remains unclear. Therefore, we investigated the effects of AA on ZnO NP-induced cytotoxicity in human lung carcinoma A549 cells. AA was found to suppress intracellular production of ROS, and thus reduce the subsequent inflammation of ZnO NPs. However, intracellular Zn2+ concentrations were higher in AA-treated cells than in AA-untreated cells. AA was found to react with Zn2+ but not with the ZnO NPs themselves. These results suggest the possibility that AA-chelated extracellular Zn2+ and the Zn-AA complex was readily taken up into cell. Even if the intracellular Zn2+ level was high, cytotoxicity might be reduced because the Zn-AA complex was stable. Co-treatment of AA to A549 inhibited ROS production and subsequent intracellular inflammatory responses. These results are consistent with those previously reported from an in vivo model. Thus, two possibilities can be considered about the cytotoxicity-reducing the effect of AA: antioxidant efficacy and chelating effect.

Comparison of antioxidant activities among four kinds of Japanese traditional fermented tea.

Antioxidant activities of four kinds of Japanese traditional fermented tea, Gishi-cha, Ishizuchi-kurocha, Awa-bancha, and Batabatacha, were compared. Antioxidant activity was evaluated by three parameters: copper ion reduction ability, radical trapping ability, and oxygen consumption rate. Processes of fermentation of these fermented teas are different. Goichi-cha and Ishizuchi-kurocha are produced by a two-stage fermentation process, aerobic fermentation and subsequent anaerobic fermentation. Awa-bancha is produced by anaerobic fermentation. And batabata-cha is produced by aerobic fermentation. Additionally, unfermented green tea was also employed as control. These tea leaves were extracted by boiling water and measured antioxidant activities. And concentrations of caffeine and catechins were measured in green tea and in the four kinds of fermented tea: Ishizuchi-kurocha, Goishi-cha, Awa-Bancha, and Batabata-cha. Concentrations of caffeine and catechins were lower in the fermented teas than in green tea. Among the fermented teas, epigallocatechin content was the highest in Ishizuchi-kurocha, whereas Batabata-cha hardly contained any epigallocatechin. Goichi-cha, Ishizuchi-kurocha, and Awa-bancha showed antioxidative activity regardless of measurement method. Batabatacha had hardly any antioxidative activity. Among the fermented teas, Ishizuchi-kurocha had the strongest antioxidant activity. The antioxidative activities of green tea and the four kinds of fermented tea were significantly different among each other (p < .01). Implication of this study is as follows: although contents of catechins were lower than that of green tea, three kinds of fermented tea showed antioxidative activity comparable to green tea. The results suggest that anaerobic fermentation process is beneficial at least for antioxidative activity.

Antioxidant properties of 5-hydroxy-4-phenyl-butenolide via activation of Nrf2/ARE signaling pathway.

5-Hydroxy-4-phenyl-butenolide (5H4PB) is a bioactive compound with antifungal and anti-obesity properties. Although it has recently been shown that 5H4PB activates peroxisome proliferator-activated receptor-gamma (PPARγ), the effect of 5H4PB on intracellular signaling pathways has not been clarified. In this study, we found that 5H4PB activated the nuclear factor erythroid 2-related factor 2 (Nrf2)/antioxidant response element (ARE) signaling pathway, which plays an important role in cellular defense against oxidative stress, and the subsequent upregulation of ARE-dependent cytoprotective genes, including the heme oxygenase-1, catalase, and superoxide dismutase genes, without exhibiting cytotoxicity. In addition, 5H4PB significantly attenuated intracellular ROS generation, glutathione oxidation, and DNA damage induced by hydrogen peroxide (H2O2) exposure in mouse fibroblast cells. Furthermore, we demonstrated that pretreatment with 5H4PB confers a significant cytoprotective effect against H2O2-induced cell death in mouse cultured fibroblasts and primary hepatocytes. Thus, our study demonstrated that 5H4PB enhanced cellular resistance to oxidative damage via activation of the Nrf2/ARE signaling pathway.

In vivo ROS production and use of oxidative stress-derived biomarkers to detect the onset of diseases such as Alzheimer's disease, Parkinson's disease, and diabetes.

Breakthroughs in biochemistry have furthered our understanding of the onset and progression of various diseases, and have advanced the development of new therapeutics. Oxidative stress and reactive oxygen species (ROS) are ubiquitous in biological systems. ROS can be formed non-enzymatically by chemical, photochemical and electron transfer reactions, or as the byproducts of endogenous enzymatic reactions, phagocytosis, and inflammation. Imbalances in ROS homeostasis, caused by impairments in antioxidant enzymes or non-enzymatic antioxidant networks, increase oxidative stress, leading to the deleterious oxidation and chemical modification of biomacromolecules such as lipids, DNA, and proteins. While many ROS are intracellular signaling messengers and most products of oxidative metabolisms are beneficial for normal cellular function, the elevation of ROS levels by light, hyperglycemia, peroxisomes, and certain enzymes causes oxidative stress-sensitive signaling, toxicity, oncogenesis, neurodegenerative diseases, and diabetes. Although the underlying mechanisms of these diseases are manifold, oxidative stress caused by ROS is a major contributing factor in their onset. This review summarizes the relationship between ROS and oxidative stress, with special reference to recent advancements in the detection of biomarkers related to oxidative stress. Further, we will introduce biomarkers for the early detection of neurodegenerative diseases and diabetes, with a focus on our recent work.

An open sandwich immunoassay for detection of 13(R,S)-hydroxy-9(E),11(E)-octadecadienoic acid.

Lipid peroxidation is involved in many disorders and diseases such as cardiovascular disease, cancers, neurodegenerative diseases, and even aging. Lipid peroxidation products existing in blood or bodily fluids are very important biomarkers for the diagnosis of such diseases. In particular, 13(R,S)-hydroxy-9(E),11(E)-octadecadienoic acid (13-(E,E)-HODE) is an oxidiation product of linoleic acid, which is an important biomarker for many diseases such as diabetes and Alzheimer's disease. In this study, we successfully displayed the antigen-binding fragment of an antibody produced by hybridoma 1213-1 on the M13 phage and performed analysis of the antibody variable region genes. The blast results suggested that it is a novel antibody. We also developed a phage-antibody-based competitive ELISA and a novel Open Sandwich ELISA (OS ELISA) for the detection of 13-(E,E)-HODE. The OS ELISA showed a limit of detection (LOD) of 15.6 nM of 13-(E,E)-HODE and low cross-reactivity with other HODE such as 9-(E,E)-HODE. Another format of the open sandwich ELISA with purified maltose binding protein-fused VL and VH-phage showed a lower LOD of 2.2 nM of 13-(E,E)-HODE, which may be sensitive enough to detect the concentration of 13-(E,E)-HODE in patients' blood samples. This is the first OS ELISA for the detection of lipids, and we believe it also represents the first molecular cloning of anti-HODE antibody genes.

Oxidation and interaction of DJ-1 with 20S proteasome in the erythrocytes of early stage Parkinson's disease patients.

Parkinson's disease (PD) is a progressive, age-related, neurodegenerative disorder, and oxidative stress is an important mediator in its pathogenesis. DJ-1, the product of the causative gene of a familial form of PD, plays a significant role in anti-oxidative defence to protect cells from oxidative stress. DJ-1 undergoes preferential oxidation at the cysteine residue at position 106 (Cys-106) under oxidative stress. Here, using specific antibodies against Cys-106-oxidized DJ-1 (oxDJ-1), it was found that the levels of oxDJ-1 in the erythrocytes of unmedicated PD patients (n = 88) were higher than in those of medicated PD patients (n = 62) and healthy control subjects (n = 33). Elevated oxDJ-1 levels were also observed in a non-human primate PD model. Biochemical analysis of oxDJ-1 in erythrocyte lysates showed that oxDJ-1 formed dimer and polymer forms, and that the latter interacts with 20S proteasome. These results clearly indicate a biochemical alteration in the blood of PD patients, which could be utilized as an early diagnosis marker for PD.

Antioxidative and Antidiabetic Effects of Natural Polyphenols and Isoflavones.

Many polyphenols that contain more than two phenolic hydroxyl groups are natural antioxidants and can provide health benefits to humans. These polyphenols include, for example, oleuropein, hydroxytyrosol, catechin, chlorogenic acids, hesperidin, nobiletin, and isoflavones. These have been studied widely because of their strong radical-scavenging and antioxidative effects. These effects may contribute to the prevention of diseases, such as diabetes. Insulin secretion, insulin resistance, and homeostasis are important factors in the onset of diabetes, a disease that is associated with dysfunction of pancreatic ß-cells. Oxidative stress is thought to contribute to this dysfunction and the effects of antioxidants on the pathogenesis of diabetes have, therefore, been investigated. Here, we summarize the antioxidative effects of polyphenols from the perspective of their radical-scavenging activities as well as their effects on signal transduction pathways. We also describe the preventative effects of polyphenols on diabetes by referring to recent studies including those reported by us. Appropriate analytical approaches for evaluating antioxidants in studies on the prevention of diabetes are comprehensively reviewed.

Trichloroethylene exposure aggravates behavioral abnormalities in mice that are deficient in superoxide dismutase.

Trichloroethylene (TCE) has been implicated as a causative agent for Parkinson's disease (PD). The administration of TCE to rodents induces neurotoxicity associated with dopaminergic neuron death, and evidence suggests that oxidative stress as a major player in the progression of PD. Here we report on TCE-induced behavioral abnormality in mice that are deficient in superoxide dismutase 1 (SOD1). Wild-type (WT) and SOD1-deficient (Sod1(-/-)) mice were intraperitoneally administered TCE (500 mg/kg) over a period of 4 weeks. Although the TCE-administrated Sod1(-/-) mice showed marked abnormal motor behavior, no significant differences were observed among the experimental groups by biochemical and histopathological analyses. However, treating mouse neuroblastoma-derived NB2a cells with TCE resulted in the down regulation of the SOD1 protein and elevated oxidative stress under conditions where SOD1 production was suppressed. Taken together, these data indicate that SOD1 plays a pivotal role in protecting motor neuron function against TCE toxicity.

Involvement of splenic iron accumulation in the development of nonalcoholic steatohepatitis in Tsumura Suzuki Obese Diabetes mice.

Nonalcoholic steatohepatitis (NASH) is a common hepatic manifestation of metabolic syndrome and can lead to hepatic cirrhosis and cancer. It is considered that NASH is caused by multiple parallel events, including abnormal lipid metabolism, gut-derived-endotoxin-induced inflammation, and adipocytokines derived from adipose tissue, suggesting that other tissues are involved in NASH development. Previous studies demonstrated that spleen enlargement is observed during the course of NASH pathogenesis. However, the involvement of splenic status in the progression of NASH remains unclear. In this study, we examined hepatic and splenic histopathological findings in the early stage of NASH using the Tsumura Suzuki Obese Diabetes (TSOD) mouse model established for assessing NASH. We found that 12-week-old TSOD mice clearly exhibited the histopathological features of NASH in the early stage. At this age, the spleen of TSOD mice showed markedly higher iron level than that of control Tsumura Suzuki Non Obesity (TSNO) mice. The level of accumulated iron was significantly decreased by feeding a diet with glucosyl hesperidin, a bioactive flavonoid, accompanied with alleviation of hepatic lesions. Furthermore, we found that splenic iron level was positively correlated with the severity of NASH manifestations, suggesting that abnormalities in the spleen are involved in the development of NASH.

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

Due to the widespread use of indium tin oxide (ITO), it is important to investigate its effect on human health. In this study, we evaluated the cellular effects of ITO nanoparticles (NPs), indium chloride (InCl3) and tin chloride (SnCl3) using human lung epithelial A549 cells. Transmission electron microscopy and inductively coupled plasma mass spectrometry were employed to study cellular ITO NP uptake. Interestingly, greater uptake of ITO NPs was observed, as compared with soluble salts. ITO NP species released could be divided into two types: 'indium release ITO' or 'tin release ITO'. We incubated A549 cells with indium release ITO, tin release ITO, InCl3 or SnCl2 and investigated oxidative stress, proinflammatory response, cytotoxicity and DNA damage. We found that intracellular reactive oxygen species were increased in cells incubated with indium release ITO, but not tin release ITO, InCl3 or SnCl2. Messenger RNA and protein levels of the inflammatory marker, interleukin-8, also increased following exposure to indium release ITO. Furthermore, the alkaline comet assay revealed that intracellular accumulation of indium ions induced DNA damage. Our results demonstrate that the accumulation of ionic indium, but not ionic tin, from ITO NPs in the intracellular matrix has extensive cellular effects.

The induction of lipid peroxidation during the acute oxidative stress response induced by intratracheal instillation of fine crystalline silica particles in rats.

Crystalline silica (SiO2) is an important material for industry but is considered potentially carcinogenic. Inhalation of a crystalline SiO2 aerosol may contribute to serious lung diseases. Crystalline SiO2 particles are commonly used as a positive control in toxicity assays of particulate materials (e.g. nanoparticles). Crystalline SiO2 induces oxidative stress resulting in lipid peroxidation, but the acute oxidative stress response in the lung is not well understood. Lipid peroxidation during the acute stage of oxidative stress after instillation of crystalline SiO2 into rats was examined by bronchoalveolar lavage fluid (BALF) analysis. The levels of 8-iso-prostaglandin F2α and hydroxyoctadecadienoic acid (HODE) in the BALF were measured using liquid chromatography coupled to quadrupole mass spectrometry. The concentration of the antioxidant protein heme oxygenase-1 (HO-1) in the BALF was determined using enzyme-linked immunosorbent assay. Intratracheal instillation of crystalline SiO2 increased the level of HODE and HO-1 in BALF at 24 h after administration. The levels of HODE and HO-1 returned to baseline at 72 h after instillation. Lactate dehydrogenase leakage was observed only after 1 h instillation. These results suggest that the contribution of oxidative stress to the pulmonary toxicity of crystalline SiO2 is minimal in the early acute stage after exposure.

Ascorbic acid attenuates acute pulmonary oxidative stress and inflammation caused by zinc oxide nanoparticles.

OBJECTIVES: It is known that inhalation of zinc oxide nanoparticles (ZnO NPs) induces acute pulmonary dysfunction, including oxidative stress, inflammation, and injury, but there are no reports on how to prevent these adverse effects. We have previously reported that the pulmonary symptoms caused by ZnO NPs were associated with oxidative stress; in the present study, we therefore investigated the use of ascorbic acid (AA), which is known as vitamin C, to prevent these toxic effects. METHODS: A ZnO NP dispersion was introduced into rat lungs by intratracheal injection, and thereafter a 1% aqueous AA solution was given as drinking water. Bronchoalveolar lavage fluid was collected at 1 day and 1 week after injection, and lactate dehydrogenase (LDH) activity, heme oxygenase-1 (HO-1), and interleukin-6 (IL-6) levels were measured. In addition, expression of the chemokine cytokine-induced neutrophil chemoattractants (CINCs), HO-1, and metallothionein-1 (MT-1) genes in the lungs were determined. RESULTS: Acute oxidative stress induced by ZnO NPs was suppressed by supplying AA. Increases in LDH activity and IL-6 concentration were also suppressed by AA, as was the expression of the CINC-1, CINC-3, and HO-1 genes. CONCLUSIONS: Oral intake of AA prevents acute pulmonary oxidative stress and inflammation caused by ZnO NPs. Intake of AA after unanticipated exposure to ZnO NPs is possibly the first effective treatment for the acute pulmonary dysfunction they cause.

In vitro evaluation of the cellular effect of indium tin oxide nanoparticles using the human lung adenocarcinoma A549 cells.

Indium tin oxide (ITO) is widely used in liquid crystal displays (LCDs) or plasma and mobile phone displays. Elevated production and usage of ITO in such displays have led to increased concerns over the safety of industrial workers exposed to particulate aerosols produced during cutting, grinding and polishing of these materials. However, the cellular effects of ITO nanoparticles (NPs) are still unclear, although it has been reported that micro-scale ITO particles induce cytotoxicity. The aim of this study was to examine the potential of ITO NPs to induce cytotoxicity, oxidative stress, and DNA damage using human lung adenocarcinoma A549 cells. Here, stable dispersions of a medium containing ITO NPs were obtained using pre-adsorption and centrifugal fractionation methods, and the A549 cells were incubated in this medium. The ITO NPs showed low cytotoxic effects as shown by the WST-1 and LDH assays. Transmission electron microscopy observations showed the cellular uptake of ITO NPs. The ITO NPs increased the intracellular level of reactive oxygen species and the expression of the heme oxygenase 1 gene. Further, the results of alkaline comet assays showed that ITO NPs induced DNA damage. Thus, these results suggest that ITO NPs possess a genotoxic potential on human lung adenocarcinoma A549 cells.

Singlet-oxygen-derived products from linoleate activate Nrf2 signaling in skin cells.

Linoleates are required for normal mammalian health and development, but they are also prone to oxidation, resulting in biologically active metabolites such as hydroxyoctadecadienoic acids (HODEs). To investigate the biological activity of 9-EZ-HODE, 10-EZ-HODE, 12-ZE-HODE, and 13-ZE-HODE, the metabolites of singlet-oxygen-derived products from linoleates, we assessed adaptive cytoprotection in HaCaT skin cells. Treating HaCaT cells with sublethal concentrations of 10-EZ-HODE and 12-ZE-HODE, which are singlet-oxygen-mediated specific oxidation metabolites of linoleates, but not 9-EZ-HODE and 13-ZE-HODE, caused resistance to hydrogen peroxide-induced oxidative damage. Microarray analysis of HaCaT cells revealed that 10-EZ-HODE and 12-ZE-HODE induced cellular antioxidant genes that are responsive to nuclear factor-erythroid 2 p45-related factor 2 (Nrf2), such as heme oxygenase-1 and glutathione synthesis enzymes. Although 10-EZ-HODE and 12-ZE-HODE did not induce Nrf2 mRNA, treatment with these metabolites increased the intranuclear expression of Nrf2. These results suggest that 10-EZ-HODE and 12-ZE-HODE initiate adaptive responses that reduce the damage caused by oxidative stress.

Type 2 diabetes model TSOD mouse is exposed to oxidative stress at young age.

Tsumura Suzuki Obese Diabetes (TSOD) mouse, a model of obese type 2 diabetes, older than around 11 weeks of age develops diabetic phenotypes. Previous studies have indicated that the development of diabetes is partly due to three loci associated with body weight and glucose homeostasis. However, little is known about the initial events triggering the development of the diabetic phenotypes in TSOD mouse. Here, we investigated the alteration of diabetes-related parameters, including the levels of blood glucose and inflammatory cytokines, and the oxidative stress status, in young TSOD mice. TSOD mice at 5 weeks of age showed increases in body weight and plasma total cholesterol level, but not hyperglycemia or impaired glucose tolerance, compared with age-matched control Tsumura Suzuki Non-Obese (TSNO) mice. Plasma tumor necrosis factor (TNF)-α and interleukin (IL)-6 were not detected in TSOD mice at 5 weeks of age. However, plasma total hydroxyoctadecadienoic acid (tHODE), a biomarker of oxidative stress, was increased in TSOD mice relative to TSNO mice at same age. The results demonstrated that young TSOD mice are exposed to oxidative stress before developing the diabetic phenotypes, and suggested that oxidative stress is an initial event triggering the development of diabetes in TSOD mice.

Cellular effects of industrial metal nanoparticles and hydrophilic carbon black dispersion.

The effects of five types of metal nanoparticles, gold (Au), silver (Ag), platinum (Pt), Au-polyvinylpyrrolidone (PVP) colloid, and Pt-PVP colloid, and two types of hydrophilic carbon black on cell behavior were examined. Stable nanoparticle dispersions were prepared and applied to the culture medium of human keratinocyte (HaCaT) and human lung carcinoma (A549) cells for 6 and 24 hr. Then, the mitochondrial activity (MTT assay) and the induction of cellular oxidative stress were examined. The exposure to Au and Ag decreased mitochondrial activity. The exposure to Pt nanoparticles induced an increase in the intracellular reactive oxygen species (ROS) level. In contrast, Au-PVP, Pt-PVP, and hydrophilic carbon black did not exhibit any effects. The observed increase in the ROS level induced by the Pt nanoparticles in this study contradicted our previous findings, in which Pt did not produce chemically reactive molecules. Some nanoparticle dispersions included chemicals as the dispersant, which is used in industrial applications. In some cases, the dispersing agent may have caused some cellular effects. Adsorption of agents on the surface of the nanoparticles may be an important factor here. Hence, the cellular effects of industrial nanoparticles should be evaluated carefully.