Size influences the cytotoxicity of poly (lactic-co-glycolic acid) (PLGA) and titanium dioxide (TiO2) nanoparticles

The aim of this study is to uncover the size influence of poly (lactic-co-glycolic acid) (PLGA) and titanium dioxide (TiO₂) nanoparticles on their potential cytotoxicity. PLGA and TiO₂ nanoparticles of three different sizes were thoroughly characterized before in vitro cytotoxic tests which included viability, generation of reactive oxygen species (ROS), mitochondrial depolarization, integrity of plasma membrane, intracellular calcium influx and cytokine release. Size-dependent cytotoxic effect was observed in both RAW264.7 cells and BEAS-2B cells after cells were incubated with PLGA or TiO₂ nanoparticles for 24 h. Although PLGA nanoparticles did not trigger significantly lethal toxicity up to a concentration of 300 μg/ml, the TNF-α release after the stimulation of PLGA nanoparticles should not be ignored especially in clinical applications. Relatively more toxic TiO₂ nanoparticles triggered cell death, ROS generation, mitochondrial depolarization, plasma membrane damage, intracellular calcium concentration increase and size-dependent TNF-α release, especially at a concentration higher than 100 μg/ml. These cytotoxic effects could be due to the size-dependent interaction between nanoparticles and biomolecules, as smaller particles tend to adsorb more biomolecules. In summary, we demonstrated that the ability of protein adsorption could be an important paradigm to predict the in vitro cytotoxicity of nanoparticles, especially for low toxic nanomaterials such as PLGA and TiO₂ nanoparticles.     

The effect of zinc oxide and titanium dioxide nanoparticles in the Comet assay with UVA photoactivation of human sperm and lymphocytes

A method to investigate the dependence of the physicochemical properties of nanoparticles (e.g., size, surface area and crystal phase) on their oxidant generating capacity is proposed and demonstrated for TiO₂ nanoparticles. Gas phase synthesis methods that allow for strict control of size and crystal phase were used to prepare TiO₂ nanoparticles. The reactive oxygen species (ROS) generating capacity of these particles was then measured. The size dependent ROS activity was established using TiO₂ nanoparticles of nine different sizes (4–195 nm) but the same crystal phase. For a fixed total surface area, an S-shaped curve for ROS generation per unit surface area was observed as a function of particle size. The highest ROS activity per unit area was observed for 30 nm particles, and observed to be constant above 30 nm. There was a decrease in activity per unit area as size decreased from 30–10 nm; and again constant for particles smaller than 10 nm. The correlation between crystal phase and oxidant capacity was established using TiO₂ nanoparticles of 11 different crystal phase combinations but similar size. The ability of different crystal phases of TiO₂ nanoparticles to generate ROS was highest for amorphous, followed by anatase, and then anatase/rutile mixtures, and lowest for rutile samples. Based on evaluation of the entire dataset, important dose metrics for ROS generation are established. The implications of these ROS studies on biological and toxicological studies using nanomaterials are discussed.     

The primary role of iron-mediated lipid peroxidation in the differential cytotoxicity caused by two varieties of talc nanoparticles on A549 cells and lipid peroxidation inhibitory effect exerted by ascorbic acid

Talc particles, the basic ingredient in different kinds of talc-based cosmetic and pharmaceutical products, pose a health risk to pulmonary and ovarian systems due to domestic and occupational exposures. Two types of talc nanoparticles depending on the source of geographical origin – indigenous- and commercial talc nanoparticles were assessed for their potential in vitro toxicity on A₅₄₉ cells; along with indigenous conventionally used microtalc particles. Cell viability, determined through live/dead staining and 3-(4,5-dimethyl thiazol-2-yl)-2,5-diphenyl tetrazolium bromide (MTT) assay, decreased as a function of concentration, origin and size of particles. Both varieties of talc nanoparticles differentially induced lipid peroxidation (LPO), which was correlated with the pattern of lactate dehydrogenase (LDH) leakage, reactive oxygen species (ROS) generation, and glutathione (GSH) depletion. Relatively higher cytotoxicity of indigenous nanotalc could be attributed to its higher content of iron as compared to commercial nanotalc. The known scavenger of ROS, l-ascorbic acid significantly inhibited LPO induction due to talc particles. Data suggest that nanotalc toxicity on A₅₄₉ cells was mediated through oxidative stress, wherein role of iron-mediated LPO was much pronounced in differential cytotoxicity.     

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.     

Toxicity of ZnO/TiO2‐conjugated carbon‐based nanohybrids on the coastal marine alga Thalassiosira pseudonana

Increasing consumption of metal‐oxide nanoparticles (NPs) and carbon‐based nanomaterials has caused significant concern about their potential hazards in aquatic environments. The release of NPs into aquatic environments could result in adsorption of NPs on microorganisms. While metal‐oxide NP‐conjugated carbon‐based nanohybrids (NHs) may exhibit enhanced toxicity toward microorganisms due to their large surface area and the generation of reactive oxygen species (ROS), there is a lack of information regarding the ecotoxicological effects of NHs on marine diatom algae, which are an indicator of marine pollution. Moreover, there is scant information on toxicity mechanisms of NHs on aquatic organisms. In this study, four NHs (ie, ZnO‐conjugated graphene oxide [GO], ZnO‐conjugated carbon nanotubes [CNTs], TiO₂‐conjugated GO, and TiO₂‐conjugated CNT) that were synthesized by a hydrothermal method were investigated for their toxicity effects on a Thalassiosira pseudonana marine diatom. The in vitro cellular viability and ROS formation employed at the concentration ranges of 50 and 100 mg/L of NHs over 72 hours revealed that ZnO‐GO had the most negative effect on T. pseudonana. The primary mechanism identified was the generation of ROS and GO‐induced dispersion that caused electrostatic repulsion, preventing aggregation, and an increase in surface areas of NHs. In contrast to GO‐induced dispersion, large aggregates were observed in ZnO/TiO₂‐conjugated CNT‐based NHs. The scanning electron microscopy images suggest that NHs covered algae cells and interacted with them (shading effects); this reduced light availability for photosynthesis. Detailed in vitro toxicity effects and mechanisms that cause high adverse acute toxicity on T. pseudonana were unveiled; this implied concerns about potential hazards of these mechanisms in aquatic ecosystems.     

Investigation on the mechanism of non‐photocatalytically TiO2‐induced reactive oxygen species and its significance on cell cycle and morphology

Titanium dioxide (TiO₂) nanoparticles are widely used in daily human life, and were reported to elicit biological effects such as oxidative stress either generating reactive oxygen species (ROS) or causing cell necrosis without generating ROS, whose underlying molecular mechanisms are not yet known. In this study, the role of dissolved oxygen in TiO₂ catalytic activity in dark environment, and long‐term cytotoxic effects of TiO₂ exposure were investigated. To determine the effect of dissolved oxygen, the anatase‐TiO₂ nanoparticle suspension was prepared both in deoxygenated and regular MilliQ water, and a ~ 9‐fold higher ROS in regular MilliQ samples was observed compared to deoxygenated samples while in the dark, which suggested dissolved oxygen as the driving agent behind the TiO₂ catalytic reaction. On the other hand, the differential cell viability and endogenous ROS activity was demonstrated through a sensitive macrophage‐based assay, on a dose‐ and time‐dependent manner. Both the cell number and endogenous ROS activity increased with increase in time till 48 h, followed by a reduction at 72 h exposure period. Long‐term exposures to these nanoparticles even at low concentrations were found detrimental to cells, where late apoptosis until 48 h and necrosis at 72 h leading to cell death were noted. Late apoptotic events and cell membrane cytoskeletal actin rearrangement observed were hypothesized to be induced by particle‐mediated cellular ROS. This in addition to radical generation ability of TiO₂ in the dark will help further in better understanding of the toxicity mechanism in cells beyond ROS generation. Copyright © 2016 John Wiley & Sons, Ltd.     

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.     

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.     

In vitro cytotoxicity and genotoxicity studies of titanium dioxide (TiO2) nanoparticles in Chinese hamster lung fibroblast cells

There are increasing safety concerns about the development and abundant use of nanoparticles. The unique physical and chemical characteristics of titanium dioxide (TiO₂) nanoparticles result in different chemical and biological activities compared to their larger micron-sized counterparts, and can subsequently play an important role in influencing toxicity. Therefore, our objective was to investigate the cytotoxicity and genotoxicity of commercially available TiO₂ nanoparticles with respect to their selected physicochemical properties, as well as the role of surface coating of these nanoparticles. While all types of tested TiO₂ samples decrease cell viability in a mass-based concentration- and size-dependent manner, the polyacrylate-coated nano-TiO₂ product was only cytotoxic at higher concentrations. A similar pattern of response was observed for induction of apoptosis/necrosis, and no DNA damage was detected in the polyacrylate-coated nano-TiO₂ model. Given the increasing production of TiO₂ nanoparticles, toxicological studies should take into account the physiochemical properties of these nanoparticles that may help researchers to develop new nanoparticles with minimum toxicity.     

Activation of the inflammasome by amorphous silica and TiO2 nanoparticles in murine dendritic cells

Abstract

Nanomaterials are increasingly used in various food applications. In particular, nanoparticulate amorphous SiO₂ is already contained, e.g., in spices. Since intestinal dendritic cells (DC) could be critical targets for ingested particles, we compared the in vitro effects of amorphous silica nanoparticles with fine crystalline silica, and micron-sized with nano-sized TiO₂ particles on DC. TiO₂- and SiO₂-nanoparticles, as well as crystalline silica led to an upregulation of MHC-II, CD80, and CD86 on DC. Furthermore, these particles activated the inflammasome, leading to significant IL-1β-secretion in wild-type (WT) but not Caspase-1- or NLRP3-deficient mice. Silica nanoparticles and crystalline silica induced apoptosis, while TiO₂ nanoparticles led to enhanced production of reactive oxygen species (ROS). Since amorphous silica and TiO₂ nanoparticles had strong effects on the activation-status of DC, we suggest that nanoparticles, used as food additives, should be intensively studied in vitro and in vivo, to ensure their safety for the consumer.     

Amplification of arsenic genotoxicity by TiO2 nanoparticles in mammalian cells: new insights from physicochemical interactions and mitochondria

Titanium dioxide nanoparticles (TiO₂ NPs) have shown great adsorption capacity for arsenic (As); however, the potential impact of TiO₂ NPs on the behavior and toxic responses of As remains largely unexplored. In the present study, we focused on the physicochemical interaction between TiO₂ NPs and As(III) to clarify the underlying mechanisms involved in their synergistic genotoxic effect on mammalian cells. Our data showed that As(III) mainly interacted with TiO₂ NPs by competitively occupying the sites of hydroxyl groups on the surface of TiO₂ NP aggregates, resulting in more aggregation of TiO₂ NPs. Although TiO₂ NPs at concentrations used here had no cytotoxic or genotoxic effects on cells, they efficiently increased the genotoxicity of As(III) in human-hamster hybrid (A_L) cells. The synergistic genotoxicity of TiO₂ NPs and As(III) was partially inhibited by various endocytosis pathway inhibitors while it was completely blocked by an As(III)-specific chelator. Using a mitochondrial membrane potential fluorescence probe, a reactive oxygen species (ROS) probe together with mitochondrial DNA-depleted ρ⁰ A_L cells, we discovered that mitochondria were essential for mediating the synergistic DNA-damaging effects of TiO₂ NPs and As(III). These data provide novel mechanistic proof that TiO₂ NPs enhanced the genotoxicity of As(III) via physicochemical interactions, which were mediated by mitochondria-dependent ROS.     

Reliable size determination of nanoparticles using dynamic light scattering method for in vitro toxicology assessment

Dynamic light scattering (DLS) is widely used for the evaluation of the particle size in the toxicity assessment of nanoparticles. However, the many types of DLS instruments and analytical procedures sometimes give different apparent sizes of particles and make it complicated to understand the size dependence on particles for the toxicity assay. In this study, we established an evaluation method of secondary nanoparticle sizes using a DLS analysis. First, we established a practical method for determining size with an appropriate evaluation of uncertainties. This proposed method could be a universal protocol for toxicity assessment that would allow researchers to achieve some degree of concordance on the size of nanoparticles for an assessment. Second, we investigated the processes associated with particles in suspension by examining the changes in the size and the light scattering intensity of secondary nanoparticles during an in vitro toxicity assessment, since the transport mode of particles to cells is significant in understanding in vitro nano-toxicity. In this study, these two points were investigated on TiO₂ nanoparticles suspension as an example. The secondary particles of TiO₂ with a light scattering intensity-averaged diameter (d_l) of 150–250 nm were characterized with appropriate uncertainties. The sizes were found to be comparable with values determined using other analytical procedures and other instruments. It is suggested that d_l could be an effective size parameter for toxicity assessments. Furthermore, TiO₂ secondary nanoparticle suspensions are well dispersed with slow gravity settling, no agglomeration, with the diffusion process as the primary transport mode of particles to cells.     

Comparison of toxicity between the different-type TiO2 nanowires in vivo and in vitro

In this study, we compared their toxicity in vivo and in vitro based on the physicochemical properties of three different types of TiO₂ nanowires, H₂Ti₃O₇ nanowires (1HTO), hydrothermal treatment (2HTO), and calcination (3HTO) of 1HTO. The surface of 1HTO was smooth, and the surface of 2HTO was much rougher. The negative charge on the surface increased in the order of 2HTO, 3HTO, and 1HTO, whereas the surface area increased in the order of 3HTO, 1HTO, and 2HTO. The lung is a main exposure route of nanoparticles. On day 28 after a single instillation (1 mg/kg), three nanowires induced a Th2-type inflammatory response together with the relative increase in CD4⁺ T cells, especially by 2HTO. In vitro, three TiO₂ nanowires (10 μg/ml) commonly induced the generation of cell debris in eight cell lines which may be the potential target organ of nanoparticles, especially by 2HTO. It seemed that the generation of cell debris coincides with the increase in autophagosome-like vacuoles in the cytosol. In further study using BEAS-2B cells originated from the lung, the protein amount from cells exposed to 2HTO decreased more clearly although the generation of reactive oxygen species (ROS) was less compared to 1HTO and 3HTO. Based on these results, we suggest that surface area may act as an important factor depends on the biological response by TiO₂ nanowires. Furthermore, the increase in autophagosome-like vacuoles may be an important cause of cell death by nanoparticles with ROS.     

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.     

Size-dependent toxicity of metal oxide particles—A comparison between nano- and micrometer size

Toxicological studies have shown increased toxicity of nanoparticles (<100 nm) compared to micrometer particles of the same composition, which has raised concern about the impact on human health from nanoparticles. However, if this is true for a wide range of particles with different chemical composition is not clear. The aim of this study was to compare the toxicity of nano- and micrometer particles of some metal oxides (Fe₂O₃, Fe₃O₄, TiO₂ and CuO). The ability of the particles to cause cell death, mitochondrial damage, DNA damage and oxidative DNA lesions were evaluated after exposure of the human cell line A549. This study showed that nanoparticles of CuO were much more toxic compared to CuO micrometer particles. One key mechanism may be the ability of CuO to damage the mitochondria. In contrast, the micrometer particles of TiO₂ caused more DNA damage compared to the nanoparticles, which is likely explained by the crystal structures. The iron oxides showed low toxicity and no clear difference between the different particle sizes. In conclusion, nanoparticles are not always more toxic than micrometer particles, but the high toxicity of CuO nanoparticles shows that the nanolevel gives rise to specific concern.     

载多柔比星二氧化钛纳米粒的制备及体外评价

目的制备载多柔比星（doxorubicin,DOX）的二氧化钛（Ti02）纳米粒,并考察其体外释放百分率及细胞毒性。方法通过水热法合成DOX的Ti02纳米粒,采用透射电镜及X-射线衍射仪对其进行表征,紫外可见分光光度法测定载药量及体外释放,采用MTT法分析其对MCF-7细胞和Hela细胞的细胞毒性。结果所制备的纳米粒分散均匀。外观呈梭状,长度约为200nm,在水中的载药量达10．85％,体外释放具有pH敏感性,空白纳米粒细胞毒性较低,载药纳米粒的细胞毒性与游离多柔比星相当。结论所制备的TiO2纳米粒具有较高的载药量及pH敏感的体外释放性能,可作为DOX的载体。     

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.     

Titanium dioxide nanoparticles impair lung mitochondrial function

Titanium dioxide nanoparticles (TiO₂ NPs) are used in an increasing number of human products such as cosmetics, sunscreen, toothpaste and paints. However, there is clear evidence about effects associated to TiO₂ NPs exposure, which include lung inflammation and tumor formation and these effects are related to reactive oxygen species (ROS) formation. The ROS generation could be attributed to a mitochondrial dysfunction. Even though, it has been shown that TiO₂ NPs exposure can induce some alterations in mitochondria including cytochrome c release to cytosol, change in mitochondrial permeability and decrease of mitochondrial membrane potential (ΔΨ_m), there is no information about the changes in mitochondrial function induced by TiO₂ NPs. We hypothesized that TiO₂ NPs effects are associated with mitochondrial dysfunction and redox unbalance. To test our hypothesis we isolated mitochondria from lung tissue of rats and exposed them to 10 (g TiO₂ NPs (particle size < 25 nm)/mg protein for 1 h. Our results showed that TiO₂ NPs decreases NADH levels and impairs ΔΨ_m and mitochondrial function accompanied by ROS generation during mitochondrial respiration.     

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