Toxicity of mixtures of zinc oxide and graphene oxide nanoparticles to aquatic organisms of different trophic level: particles outperform dissolved ions

Concomitant releases of various engineered nanoparticles (NPs) into the environment have resulted in concerns regarding their combined toxicity to aquatic organisms. It is however, still elusive to distinguish the contribution to toxicity of components in NP mixtures. In the present study, we quantitatively evaluated the relative contribution of NPs in their particulate form (NP_(particle)) and of dissolved ions released from NPs (NP_(ion)) to the combined toxicity of binary mixtures of ZnO NPs and graphene oxide nanoplatelets (GO NPs) to three aquatic organisms of different trophic levels, including an alga species (Scenedesmus obliquus), a cladoceran species (Daphnia magna), and a freshwater fish larva (Danio rerio). Our results revealed that the effects of ZnO NPs and GO NPs were additive to S. obliquus and D. magna but antagonistic to D. rerio. The relative contribution to toxicity (RCT) of the mixture components to S. obliquus decreased in the order of RCT_{GO NP(particle)} >?RCT_{ZnO NP(particle)}?>?RCT_{ZnO NP(ion)}, while the RCT of the mixture components to D. magna and D. rerio decreased in the order of RCT_{ZnO NP(particle)}?>?RCT_{GO NP(particle)}?>?RCT_{ZnO NP(ion)}. This finding also implies that the suspended particles rather than the dissolved Zn-ions dictated the combined toxicity of binary mixtures of ZnO NPs and GO NPs to the aquatic organisms of different trophic level. The alleviation of the contribution to toxicity of the ionic form of ZnO NPs was caused by the adsorption of the dissolved ions on GO NPs. Furthermore, the ZnO NP_(particle) and GO NP_(particle) displayed a different contribution to the observed mixture toxicity, dependent on the trophic level of the aquatic organisms tested. The difference of the contributions between the two particulate forms was mainly associated with differences in the intracellular accumulation of reactive oxygen species. Our findings highlight the important role of particles in the ecological impact of multi-nanomaterial systems.     

Comparative study of ZnO and TiO2 nanoparticles: physicochemical characterisation and toxicological effects on human colon carcinoma cells

Abstract

Despite human gastrointestinal exposure to nanoparticles (NPs), data on NPs toxicity in intestinal cells are quite scanty. In this study we evaluated the toxicity induced by zinc oxide (ZnO) and titanium dioxide (TiO₂) NPs on Caco-2 cells. Only ZnO NPs produced significant cytotoxicity, evaluated by two different assays. The presence of foetal calf serum in culture medium significantly reduced ZnO NPs toxicity as well as ion leakage and NP-cell interaction. The two NPs increased the intracellular amount of reactive oxygen species (ROS) after 6 h treatment. However, only ZnO NPs increased ROS and induced IL-8 release both after 6 and 24 h. Experimental data indicate a main role of chemical composition and solubility in ZnO NPs toxicity. Moreover our results suggest a key role of oxidative stress in ZnO NPs cytotoxicity induction related both to ion leakage and to cell interaction with NPs in serum-free medium.     

Mechanisms of titanium dioxide nanoparticle‐induced oxidative stress and modulation of plasma glucose in mice

Titanium dioxide nanoparticles (TiO₂ NPs) are reported to increase plasma glucose levels in mice at specific doses. The production and accumulation of reactive oxygen species (ROS) is potentially the most important factor underlying the biological toxicity of TiO₂ NPs but the underlying mechanisms are unclear at present. Data from genome‐wide analyses showed that TiO₂ NPs induce endoplasmic reticulum (ER) stress and ROS generation, leading to the inference that TiO₂ NP‐induced ER stress contributes to enhancement of ROS in mice. Resveratrol (Res) effectively relieved TiO₂ NP‐induced ER stress and ROS generation by ameliorating expression of a common set of activated genes for both processes, signifying that ER stress and ROS are closely related. TiO₂ NP‐induced ER stress occurred earlier than ROS generation. Upon treatment with 4‐phenylbutyric acid to relieve ER stress, plasma glucose levels tended toward normal and TiO₂ NP increased ROS production was inhibited. These results suggest that TiO2 NP‐induced ER stress promotes the generation of ROS, in turn, triggering increased plasma glucose levels in mice. In addition, Res that displays the ability to reduce ER stress presents a dietary polyphenol antioxidant that can effectively prevent the toxicological effects of TiO₂ NPs on plasma glucose metabolism.     

Dissolution and bandgap paradigms for predicting the toxicity of metal oxide nanoparticles in the marine environment: an in vivo study with oyster embryos

Dissolution and bandgap paradigms have been proposed for predicting the ability of metal oxide nanoparticles (NPs) to induce oxidative stress in different in vitro and in vivo models. Here, we addressed the effectiveness of these paradigms in vivo and under conditions typical of the marine environment, a final sink for many NPs released through aquatic systems. We used ZnO and MnO₂ NPs as models for dissolution and bandgap paradigms, respectively, and CeO₂ NPs to assess reactive oxygen radical (ROS) production via Fenton-like reactions in vivo. Oyster embryos were exposed to 0.5–500?μM of each test NP over 24?h and oxidative stress was determined as a primary toxicity pathway across successive levels of biological complexity, with arrested development as the main pathological outcome. NPs were actively ingested by oyster larvae and entered cells. Dissolution was a viable paradigm for predicting the toxicity of NPs in the marine environment, whereas the surface reactivity based paradigms (i.e. bandgap and ROS generation via Fenton-like reaction) were not supported under seawater conditions. Bio-imaging identified potential cellular storage-disposal sites of solid particles that could ameliorate the toxicological behavior of non-dissolving NPs, whilst abiotic screening of surface reactivity suggested that the adsorption-complexation of surface active sites by seawater ions could provide a valuable hypothesis to explain the quenching of the intrinsic oxidation potential of MnO₂ NPs in seawater.     

Mechanism of TiO2 nanoparticle‐induced neurotoxicity in zebrafish (Danio rerio)

Zebrafish (Danio rerio) has been used historically for evaluating the toxicity of environmental and aqueous toxicants, and there is an emerging literature reporting toxic effects of manufactured nanoparticles (NPs) in zebrafish embryos. Few researches, however, are focused on the neurotoxicity on adult zebrafish after subchronic exposure to TiO₂ NPs. This study was designed to evaluate the morphological changes, alterations of neurochemical contents, and expressions of memory behavior‐related genes in zebrafish brains caused by exposures to 5, 10, 20, and 40 μg/L TiO₂ NPs for 45 consecutive days. Our data indicated that spatial recognition memory and levels of norepinephrine, dopamine, and 5‐hydroxytryptamine were significantly decreased and NO levels were markedly elevated, and over proliferation of glial cells, neuron apoptosis, and TiO₂ NP aggregation were observed after low dose exposures of TiO₂ NPs. Furthermore, the low dose exposures of TiO₂ NPs significantly activated expressions of C‐fos, C‐jun, and BDNF genes, and suppressed expressions of p38, NGF, CREB, NR1, NR2ab, and GluR2 genes. These findings imply that low dose exposures of TiO₂ NPs may result in the brain damages in zebrafish, provide a developmental basis for evaluating the neurotoxicity of subchronic exposure, and raise the caution of aquatic application of TiO₂ NPs. © 2014 Wiley Periodicals, Inc. Environ Toxicol 31: 163–175, 2016.     

Phoxim‐induced damages of Bombyx mori larval midgut and titanium dioxide nanoparticles protective role under phoxim‐induced toxicity

Phoxim (O,O‐diethyl O‐(alpha‐cyanobenzylideneamino) phosphorothioate) is a powerful organophosphorus pesticide with high potential for Bombyx mori larvae of silkworm exposure. However, it is possible that during the phoxim metabolism, there is generation of reactive oxygen species (ROS) and phoxim may produce oxidative stress and neurotoxicity in an intoxicated silkworm. Titanium dioxide nanoparticles (TiO₂ NPs) pretreatment has been demonstrated to increase antioxidant capacity and acetylcholinesterase (AChE) activity in organisms. This study was, therefore, undertaken to determine phoxim‐induced oxidative stress and neurotoxicity to determine whether phoxim intoxication alters the antioxidant system and AChE activity in the B. mori larval midgut, and to determine whether TiO₂ NPs pretreatment attenuates phoxim‐induced toxicity. The findings suggested that phoxim exposure decreased survival of B. mori larvae, increased malondialdehyde (MDA), carbonyl and 8‐OHdG levels, and ROS accumulation in the midgut. Furthermore, phoxim significantly decreased the activities of AChE, superoxide dismutase (SOD), ascorbate peroxidase (APX), glutathione reductase (GR), glutathione‐S‐transferase (GST), and levels of ascorbic acid (AsA), reduced glutathione (GSH), and thiol in the midgut. TiO₂ pretreatment, however, could increase AChE activity, and remove ROS via activating SOD, CAT, APX, GR, and GST, and accelerating AsA–GSH cycle, thus attenuated lipid, protein, and DNA peroxidation and improve B. mori larval survival under phoxim‐induced toxicity. Moreover, this experimental system would help nanomaterials to be applied in the sericulture. © 2013 Wiley Periodicals, Inc. Environ Toxicol 29: 1355–1366, 2014.     

Zinc oxide nanoparticles induced oxidative stress in mouse bone marrow mesenchymal stem cells

Engineered nanoparticles are developed for various applications in industrial, electrical, agricultural, pharmaceutical and medical fields due to their unique properties. Nanoparticles such as TiO₂ and ZnO are widely used in cosmetics for UV protection. The toxicological investigations of ZnO NPs are highly recommended because of the increasing use in various industrial and consumer products. The toxic potential of ZnO NPs was assumed to be caused by the release of free Zn+ ions in the medium. Many of the in vivo studies suggest the toxic nature of ZnO NPs, the in vitro studies are certainly important to elucidate the mechanism of toxicity. This study examined the toxicity of ZnO NPs with the average size of 6–8?nm on the isolated mice bone marrow mesenchymal stem cells. The study focuses on the cytotoxicity and oxidative stress-mediated cellular responses upon exposure to ZnO NPs. The results indicated that the exposure to ZnO NPs significantly affects cellular viability in a dose-dependent manner. Formation of reactive oxygen species (ROS) was found to be the mechanism of cellular toxicity. The release of Zn⁺ ions from the nanoparticles, due to the instability of ZnO NPs in the acidic compartment of lysosomes, also increases the ROS generation. In addition to increased ROS production, damage of lysosomal membrane and the activation of executioner caspase-3 and caspase-7 were observed, which eventually ends in apoptosis.     

The effects of endoplasmic reticulum stress inducer thapsigargin on the toxicity of ZnO or TiO2 nanoparticles to human endothelial cells

It was recently shown that ZnO nanoparticles (NPs) could induce endoplasmic reticulum (ER) stress in human umbilical vein endothelial cells (HUVECs). If ER stress is associated the toxicity of ZnO NPs, the presence of ER stress inducer thapsigargin (TG) should alter the response of HUVECs to ZnO NP exposure. In this study, we addressed this issue by assessing cytotoxicity, oxidative stress and inflammatory responses in ZnO NP exposed HUVECs with or without the presence of TG. Moreover, TiO₂ NPs were used to compare the effects. Exposure to 32?μg/mL ZnO NPs (p?2 NPs (p?>?0.05), significantly induced cytotoxicity as assessed by WST-1 and neutral red uptake assay, as well as intracellular ROS. ZnO NPs dose-dependently increased the accumulation of intracellular Zn ions, and ZnSO₄ induced similar cytotoxic effects as ZnO NPs, which indicated a role of Zn ions. The release of inflammatory proteins tumor necrosis factor α (TNFα) and interleukin-6 (IL-6) or the adhesion of THP-1 monocytes to HUVECs was not significantly affected by ZnO or TiO₂ NP exposure (p?>?0.05). The presence of 250?nM TG significantly induced cytotoxicity, release of IL-6 and THP-1 monocyte adhesion (p?p?>?0.05). ANOVA analysis indicated no interaction between exposure to ZnO NPs and the presence of TG on almost all the endpoints (p?>?0.05) except neutral red uptake assay (p?相似文献   

In vitro evaluation of the toxicity and underlying molecular mechanisms of Janus Fe3O4‐TiO2 nanoparticles in human liver cells

Recent studies show that Janus Fe₃O₄‐TiO₂ nanoparticles (NPs) have potential applications as a multifunctional agent of magnetic resonance imaging (MRI) and photodynamic therapy (PDT) for the diagnosis and therapy of cancer. However, little work has been done on their biological effects. To evaluate the toxicity and underlying molecular mechanisms of Janus Fe₃O₄‐TiO₂ nanoparticles, an in vitro study using a human liver cell line HL‐7702 cells was conducted. For comparison, the Janus Fe₃O₄‐TiO₂ NPs parent material TiO₂ NPs was also evaluated. Results showed that both Fe₃O₄‐TiO₂ NPs and TiO₂ NPs decreased cell viability and ATP levels when applied in treatment, but increased malonaldehyde (MDA) and reactive oxygen species (ROS) generation. Mitochondria JC‐1 staining assay showed that mitochondrial membrane permeability injury occurred in both NPs treated cells. Cell viability analysis showed that TiO₂ NPs induced slightly higher cytotoxicity than Fe₃O₄‐TiO₂ NPs in HL7702 cells. Western blotting indicated that both TiO₂ NPs and Fe₃O₄‐TiO₂ NPs could induce apoptosis, inflammation, and carcinogenesis related signal protein alterations. Comparatively, Fe₃O₄‐TiO₂ NPs induced higher signal protein expressions than TiO₂ NPs under a high treatment dose. However, under a low dose (6.25 μg/cm²), neither NPs had any significant toxicity on HL7702 cells. In addition, our results suggest both Fe₃O₄‐TiO₂ NPs and TiO₂ NPs could induce oxidative stress and have a potential carcinogenetic effect in vitro. Further studies are needed to elaborate the detailed mechanisms of toxicity induced by a high dose of Fe₃O₄‐TiO₂ NPs.     

No evidence of the genotoxic potential of gold,silver, zinc oxide and titanium dioxide nanoparticles in the SOS chromotest

Gold nanoparticles (Au NPs), silver nanoparticles (Ag NPs), zinc oxide nanoparticles (ZnO NPs) and titanium dioxide nanoparticles (TiO₂ NPs) are widely used in cosmetic products such as preservatives, colorants and sunscreens. This study investigated the genotoxicity of Au NPs, Ag NPs, ZnO NPs and TiO₂ NPs using the SOS chromotest with Escherichia coli PQ37. The maximum exposure concentrations for each nanoparticle were 3.23 mg l^–1 for Au NPs, 32.3 mg l^–1 for Ag NPs and 100 mg l^–1 for ZnO NPs and TiO₂ NPs. Additionally, in order to compare the genotoxicity of nanoparticles and corresponding dissolved ions, the ions were assessed in the same way as nanoparticles. The genotoxicity of the titanium ion was not assessed because of the extremely low solubility of TiO₂ NPs. Au NPs, Ag NPs, ZnO NPs, TiO₂ NPs and ions of Au, Ag and Zn, in a range of tested concentrations, exerted no effects in the SOS chromotest, evidenced by maximum IF (IFmax) values of below 1.5 for all chemicals. Owing to the results, nanosized Au NPs, Ag NPs, ZnO NPs, TiO₂ NPs and ions of Au, Ag and Zn are classified as non‐genotoxic on the basis of the SOS chromotest used in this study. To the best of our knowledge, this is the first study to evaluate the genotoxicity of Au NPs, Ag NPs, ZnO NPs and TiO₂ NPs using the SOS chromotest. Copyright © 2012 John Wiley & Sons, Ltd.     

3‐Hydroxyflavone enhances the toxicity of ZnO nanoparticles in vitro

It is recently shown that flavonoids might reduce the toxicity of nanoparticles (NPs) due to their antioxidative properties. In this study, the influence of 3‐hydroxyflavone (H3) on the toxicity of ZnO NPs was investigated. H3 increased hydrodynamic size, polydispersity index and absolute value of the zeta potential of ZnO NPs, which indicated that H3 could influence the colloidal aspects of NPs. Surprisingly, H3 markedly decreased the initial concentration of ZnO NPs required to induce cytotoxicity to Caco‐2, HepG2, THP‐1 and human umbilical vein endothelial cells, which suggested that H3 could promote the toxicity of ZnO NPs to both cancerous and normal cells. For comparison, 6‐hydroxyflavone did not show this effect. H3 remarkably increased cellular Zn elements and intracellular Zn ions in HepG2 cells following ZnO NP exposure, and co‐exposure to H3 and NPs induced a relatively higher intracellular reactive oxygen species. Exposure to ZnO NPs at 3 hours induced the expression of endoplasmic reticulum stress markers DDIT3 and XBP‐1 s, which was suppressed by H3. The expression of apoptotic genes BAX and CASP3 was significantly induced by ZnO NP exposure after 3 and 5 hours, respectively, and H3 further significantly promoted CASP3 expression at 5 hours. In combination, the results from this study suggested that H3 affected colloidal stability of ZnO NPs, promoted the interactions between NPs and cells, and altered the NP‐induced endoplasmic reticulum stress–apoptosis signaling pathway, which finally enhanced the cytotoxicity of ZnO NPs.     

Inflammatory response in human alveolar epithelial cells after TiO2 NPs or ZnO NPs exposure: Inhibition of surfactant protein A expression as an indicator for loss of lung function

The increasing use of metal oxide nanoparticles (MONPs) as TiO₂ NPs or ZnO NPs has led to environmental release and human exposure. The respiratory system, effects on lamellar bodies and surfactant protein A (SP-A) of pneumocytes, can be importantly affected. Exposure of human alveolar epithelial cells (A549) induced differential responses; a higher persistence of TiO₂ in cell surface and uptake (measured by Atomic Force Microscopy) and sustained inflammatory response (by means of TNF-α, IL-10, and IL-6 release) and ROS generation were observed, whereas ZnO showed a modest response and low numbers in cell surface. A reduction in SP-A levels at 24 h of exposure to TiO₂ NPs (concentration-dependent) or ZnO NPs (the higher concentration) was also observed, reversed by blocking the inflammatory response (by the inhibition of IL-6). Loss of SP-A represents a relevant target of MONPs-induced inflammatory response that could contribute to cellular damage and loss of lung function.     

Acute exposure to ZnO nanoparticles induces autophagic immune cell death

Abstract

The increasing risk of incidental exposure to nanomaterials has led to mounting concerns regarding nanotoxicity. Zinc oxide nanoparticles (ZnO NPs) are produced in large quantities and have come under scrutiny due to their capacity to cause cytotoxicity in vitro and potential to cause harm in vivo. Recent evidence has indicated that ZnO NPs promote autophagy in cells; however, the signaling pathways and the role of ion release inducing toxicity remain unclear. In this study, we report that ZnO NPs are immunotoxic to primary and immortalized immune cells. Importantly, such immunotoxicity is observed in mice in vivo, since death of splenocytes is seen after intranasal exposure to ZnO NPs. We determined that ZnO NPs release free Zn²⁺ that can be taken up by immune cells, resulting in cell death. Inhibiting free Zn²⁺ ions in solution with EDTA or their uptake with CaCl₂ abrogates ZnO NP-induced cell death. ZnO NP-mediated immune cell death was associated with increased levels of intracellular reactive oxygen species (ROS). ZnO NP death was not due to apoptosis, necroptosis or pyroptosis. Exposure of immune cells to ZnO NPs resulted in autophagic death and increased levels of LC3A, an essential component of autophagic vacuoles. Accordingly, ZnO NP-mediated upregulation of LC3A and induction of immune cell death were inhibited by blocking autophagy and ROS production. We conclude that release of Zn²⁺ from ZnO NPs triggers the production of excessive intracellular ROS, resulting in autophagic death of immune cells. Our findings suggest that exposure to ZnO NPs has the potential to impact host immunity.     

Comparative cytotoxicity induced by bulk and nanoparticulated ZnO in the fish and human hepatoma cell lines PLHC-1 and Hep G2

Abstract

The increasing presence of ZnO nanoparticles (NPs) in consumer products may be having a dramatic impact in aquatic environments. The evaluation of ZnO NP toxicity represents a great challenge. This study aimed at evaluating the cytotoxic effect of micro- and nanosized ZnO in a fish and a mammalian hepatoma cell line. A detailed characterisation of the particles in exposure media showed that ZnO NPs formed large aggregates. ZnO cytotoxicity was evaluated with a battery of in vitro assays including LUCS, a new approach based on DNA alteration measurements. In fish cells, ZnO NP aggregates contributed substantially to the cytotoxic effects whereas toxicity in the human cells appeared to be mainly produced by the dissolved fraction. ROS production did not contribute to the observed cytotoxicity. This work also showed that measuring concentrations of NPs is essential to understand the mechanisms underlying their toxicity.     

Evaluation of cytogenotoxicity and oxidative stress parameters in male Swiss mice co-exposed to titanium dioxide and zinc oxide nanoparticles

A number of studies have investigated the adverse toxic effects of titanium dioxide (TiO₂) nanoparticles (NPs) or zinc oxide (ZnO) NPs. Information on the potential genotoxic effects of the interactions of TiO₂ NPs and ZnO NPs in vivo is lacking. Therefore, this study was designed to investigate the cytogenotoxicity of TiO₂ NPs or ZnO NPs alone or their mixtures using the bone marrow micronucleus assay, and mechanism of damage through the evaluation of oxidative stress parameters in the liver and kidney tissues of Swiss mice. Intraperitoneal administration of doses between 9.38 and 150.00 mg/kg of TiO₂ NPs or ZnO NPs or TiO₂ NPs + ZnO NPs was performed for 5 and 10 days, respectively. TiO₂ NPs alone induced a significant (P < 0.05) increase in micronucleated (Mn) polychromatic erythrocytes (PCEs) at the applied doses compared with the negative controls, with a significant difference between 5 and 10 days for TiO₂ NPs alone and TiO₂ NPs + ZnO NPs. Concurrently, TiO₂ NPs alone for 5 days and TiO₂ NPs and TiO₂ NPs + ZnO NPs for 10 days significantly (P < 0.05) decreased the percentage PCE: normochromatic erythrocyte (NCE) indicating cytotoxicity; with a significant difference between the two periods. Significant (P < 0.001) changes in the activities of superoxide dismutase (SOD) and catalase (CAT), and levels of reduced glutathione (GSH) and malondialdehyde (MDA) were observed in the liver and kidney of mice exposed to TiO₂ NPs or ZnO NPs alone or their mixtures. These results suggest that TiO₂ NPs alone was genotoxic; TiO₂ NPs and TiO₂ NPs + ZnO NPs were noticeably cytotoxic while ZnO NPs was not cytogenotoxic. The individual NPs or their mixtures induced oxidative stress.     

Cytotoxicity,oxidative stress and inflammation induced by ZnO nanoparticles in endothelial cells: interaction with palmitate or lipopolysaccharide

Recent studies showed that ZnO nanoparticles (NPs) might induce the toxicity to human endothelial cells. However, little is known about the interaction between ZnO NPs and circulatory components, which is likely to occur when NPs enter the blood. In this study, we evaluated ZnO NP‐induced cytotoxicity, oxidative stress and inflammation in human umbilical vein endothelial cells (HUVECs), with the emphasis on the interaction with palmitate (PA) or lipopolysaccharide (LPS), because PA and LPS are normal components in human blood that increase in metabolic diseases. Overall, ZnO NPs induced cytotoxicity and intracellular reactive oxygen species (ROS) at a concentration of 32 μg ml⁻¹, but did not significantly affect the release of inflammatory cytokines or adhesion of THP‐1 monocytes to HUVECs. In addition, exposure to ZnO NPs dose‐dependently promoted intracellular Zn ions in HUVECs. PA and LPS have different effects. Two hundred μm PA significantly induced cytotoxicity and THP‐1 monocyte adhesion, but did not affect ROS or release of inflammatory cytokines. In contrast, 1 μg ml⁻¹ LPS significantly induced ROS, release of inflammatory cytokines and THP‐1 monocyte adhesion, but not cytotoxicity. The presence of ZnO NPs did not significantly affect the toxicity induced by PA or LPS. In addition, the accumulation of Zn ions after ZnO NP exposure was not significantly affected by the presence of PA or LPS. We concluded that there was no interaction between ZnO NPs and PA or LPS on toxicity to HUVECs in vitro . Copyright © 2016 John Wiley & Sons, Ltd.     

Gender difference in hepatic toxicity of titanium dioxide nanoparticles after subchronic oral exposure in Sprague‐Dawley rats

Existing literature pointed out that the liver may be the target organ of toxicity induced by titanium dioxide nanoparticles (TiO₂ NPs) via oral exposure. Gender differences in health effects widely exist and relevant toxicological research is important for safety assessment. To explore the gender susceptibility of TiO₂ NP‐induced hepatic toxicity and the underlying mechanism, we examined female and male Sprague‐Dawley rats administrated with TiO₂ NPs orally at doses of 0, 2, 10 and 50 mg/kg body weight per day for 90 days. The serum biochemical indicators and liver pathological observation were used to assess hepatic toxicity. We found significant hepatic toxicity could be induced by subchronic oral exposure to TiO₂ NPs, which was more obvious and severe in female rats. No accumulation of TiO₂ NPs in the liver was observed, indicating that hepatic toxicity may not be caused through direct pathways. Oxidized glutathione, lipid peroxidation products increased significantly and reduced glutathione decreased significantly in the liver of rats in repeated TiO₂ NP‐exposed groups. Hematological parameters of white blood cells and inflammatory cytokines in serum including interleukin 1α, interleukin 4 and tumor necrosis factor also increased significantly. Indirect pathways through initiating oxidative stress and inflammatory responses were suggested as the possible mechanism of the hepatic toxicity in this experiment. The higher sensitivity to redox homeostasis imbalance and inflammation of female rats may be the main reason for gender differences. Our research suggested that gender should be a susceptible factor for identifying and monitoring long‐term oral toxicity of TiO₂ NPs.     

Rat pancreatitis produced by 13‐week administration of zinc oxide nanoparticles: biopersistence of nanoparticles and possible solutions

Zinc oxide (ZnO) nanoparticles (NPs) are used in diverse applications ranging from paints and cosmetics to biomedicine and food. Although micron‐sized ZnO is a traditional food supplement, ZnO NPs are an unknown public health risk because of their unique physicochemical properties. Herein, we studied the 13‐week subchronic toxicity of ZnO NPs administered via the oral route according to Organization for Economic Cooperation and Development (OECD) test guideline 408. Well‐dispersed ZnO NPs were administered to Sprague–Dawley (SD) rats (11/sex/group) at doses of 67.1, 134.2, 268.4 or 536.8 mg kg^–1 per body weight over a 13‐week period. The mean body weight gain in males given 536.8 mg kg^–1 ZnO NPs was significantly lower than that of control male rats, whereas no significant differences were observed between the other treatment groups and the controls. Male and female rats dosed at 536.8 mg kg^–1 ZnO NPs had significant changes in anemia‐related hematologic parameters. Mild to moderate pancreatitis also developed in both sexes dosed at 536.8 mg kg^–1, whereas no histological changes were observed in the other treatment groups. To evaluate the mechanism of toxicity, we performed a bio‐persistence study and evaluated the effects of the ZnO NPs on cell proliferation. The treatment of a human gastric adenocarcinoma cell line with ZnO NPs resulted in a significant inhibition of cellular proliferation. The anti‐proliferative effect of ZnO NPs or Zn²⁺ was effectively blocked by treatment with chelators. These results indicate that the bio‐persistence of ZnO NPs after ingestion is key to their toxicity; the no‐observed‐adverse effect level (NOAEL) of ZnO NPs was found to be 268.4 mg kg^–1 per day for both sexes. Copyright © 2013 John Wiley & Sons, Ltd.     

The size‐dependent genotoxic potentials of titanium dioxide nanoparticles to endothelial cells

Despite intensive research activities, there are still many major knowledge gaps over the potential adverse effects of titanium dioxide nanoparticles (TiO₂‐NPs), one of the most widely produced and used nanoparticles, on human cardiovascular health and the underlying mechanisms. In the present study, alkaline comet assay and cytokinesis‐block micronucleus test were employed to determine the genotoxic potentials of four sizes (100, 50, 30, and 10 nm) of anatase TiO₂‐NPs to human umbilical vein endothelial cells (HUVECs) in culture. Also, the intracellular redox statuses were explored through the measurement of the levels of reactive oxygen species (ROS) and reduced glutathione (GSH) with kits, respectively. Meanwhile, the protein levels of nuclear factor erythroid 2‐related factor 2 (Nrf2) were also detected by western blot. The results showed that at the exposed levels (1, 5, and 25 μg/mL), all the four sizes of TiO₂‐NPs could elicit an increase of both DNA damage and MN frequency in HUVECs in culture, with a positive dose‐dependent and negative size‐dependent effect relationship (T100 < T50 < T30 < T10). Also, increased levels of intracellular ROS, but decreased levels of GSH, were found in all the TiO₂‐NP‐treated groups. Intriguingly, a very similar manner of dose‐dependent and size‐dependent effect relationship was observed between the ROS test and both comet assay and MN test, but contrary to that of GSH assay. Correspondingly, the levels of Nrf2 protein were also elevated in the TiO₂‐NP‐exposed HUVECs, with an inversely size‐dependent effect relationship. These findings indicated that induction of oxidative stress and subsequent genotoxicity might be an important biological mechanism by which TiO₂‐NP exposure would cause detrimental effects to human cardiovascular health.     

Comparison of subchronic immunotoxicity of four different types of aluminum‐based nanoparticles

Nanoparticles (NPs) have recently emerged as an inhalable pollutant, owing to their applications, aluminum‐based NPs (Al‐NPs) have been prioritized for toxicity testing. In the current study, we compared the pulmonary biopersistence and subsequent toxicity of four different types of Al‐NPs (two rod‐type aluminum oxide NPs [AlONPs] with different aspect ratios [short (S)‐ and long (L)‐AlONPs], spherical aluminum cerium oxide NPs [AlCeO₃, AlCeONPs] and spherical γ‐aluminum oxide hydroxide nanoparticles [AlOOHNPs]) 13weeks after a single intratracheal instillation, considering the importance of their properties in their toxicity. We found that the pulmonary biopersistence of Al‐NPs was strengthened by a high aspect ratio in the rod‐type AlONPs and by the presence of hydroxyl groups in the spherical‐type Al‐NPs. The highest toxicity was observed in the mice treated with AlOOHNPs, which showed low biostability. More importantly, we identified that the commercially available AlCeONPs were Al₂O₃‐coated CeO₂ NPs, but not AlCeO₃ NPs, although they have been sold under the trade name of AlCeONPs. In conclusion, the aspect ratio and biostability may be important factors in the determination of the biopersistence of NPs and the subsequent biological response. In addition, the physicochemical properties of NPs should be examined in detail before their release into the market to prevent unexpected adverse health effects.