纳米二氧化钛的毒理学研究进展

纳米二氧化钛与人体有广泛的接触。不同粒径的纳米二氧化钛随产品以各种不同的途径进入人体,对其毒性的研究迫在眉睫。纳米二氧化钛一旦进入机体后,可以导致各个脏器不同程度的损伤,对肺部的损伤表现为炎症、纤维化甚至导致肿瘤的发生;纳米二氧化钛还可以导致血管内皮细胞的损伤,脑组织的脂肪变性,肝脏水肿和肝小叶坏死,肾小球肿胀等;二氧化钛进入细胞后,细胞对它的清除能力会随着二氧化钛粒径缩小而下降,并且会对细胞造成细胞膜的破坏,细胞核DNA的损伤和断裂,以及有关蛋白质的含量和酶活性的变化。     

Bioaccumulation of ionic titanium and titanium dioxide nanoparticles in zebrafish eleutheroembryos

Abstract

The production of titanium dioxide nanoparticles (TiO₂ NPs) for commercial applications has greatly increased over the last years and consequently the potential risk for human health. There is a growing awareness of the need to understand the behavior and influence these nanoparticles exert on the environment. Bioaccumulation serves as a good integrator to assess chemical exposure in aquatic systems and is dependent on factors, such as the exposure routes, diet and the aqueous medium. We analyzed the experimental bioaccumulation capability of ionic titanium and TiO₂ NPs by zebrafish (Danio rerio) eleutheroembryos through bioconcentration factors (BCFs), after 48 or 72?h of exposure. The stability of both chemical forms in an aquatic medium was fully characterized for further bioaccumulation studies. Several stabilizing agents (humic acids, soluble starch, polyethylene glycol, Na₄P₂O₇ and Na₂HPO₄) for anatase and rutile, the two allotrophs of TiO₂ NPs, were evaluated to check the evolution of the aggregation process. Around 60% of TiO₂ NPs remained disaggregated under simulated environmental conditions with the addition of 50?mg?L^?1 of humic acids. However, the presence of eleutheroembryos in the exposure medium increased TiO₂ NPs aggregation in the experimental tests. The BCFs values obtained in all cases were <100, which classifies ionic titanium and TiO₂ NPs as non-bioaccumulative substances, under the REACH regulations.     

Analysis of titanium dioxide and zinc oxide nanoparticles in cosmetics

There have been rapid increases in consumer products containing nanomaterials, raising concerns over the impact of nanoparticles (NPs) to humankind and the environment, but little information has been published about mineral filters in commercial sunscreens. It is urgent to develop methods to characterize the nanomaterials in products. Titanium dioxide (TiO₂) and zinc oxide (ZnO) NPs in unmodified commercial sunscreens were characterized by laser scanning confocal microscopy, atomic force microscopy, X-ray diffraction (XRD), and transmission electron microscopy (TEM). The results showed that laser scanning confocal microscopy evaluated primary particle aggregates and dispersions but could not size NPs because of the diffraction limited resolution of optical microscopy (200 nm). Atomic force microscopy measurements required a pretreatment of the sunscreens or further calibration in phase analysis, but could not provide their elemental composition of commercial sunscreens. While XRD gave particle size and crystal information without a pretreatment of sunscreen, TEM analysis required dilution and dispersion of the commercial sunscreens before imaging. When coupled with energy-dispersive X-ray spectroscopy, TEM afforded particle size information and compositional analysis. XRD characterization of six commercial sunscreens labeled as nanoparticles revealed that three samples contained TiO₂ NPs, among which two listed ZnO and TiO₂, and displayed average particle sizes of 15 nm, 21 nm, and 78 nm. However, no nanosized ZnO particles were found in any of the samples by XRD. In general, TEM can resolve nanomaterials that exhibit one or more dimensions between 1 nm and 100 nm, allowing the identification of ZnO and TiO₂ NPs in all six sunscreens and ZnO/TiO₂ mixtures in two of the samples. Overall, the combination of XRD and TEM was suitable for analyzing ZnO and TiO₂ NPs in commercial sunscreens.     

纳米活性炭,纳米二氧化硅和纳米二氧化钛对人胃肿瘤BGC-823细胞的毒性作用

目的探讨不同化学组成的纳米颗粒对人胃癌BGC-823细胞的毒性作用及其机制。方法分别以纳米活性炭(ACNP)、纳米二氧化硅(SiO2)和纳米二氧化钛(TiO2)100,200,400,800和1600mg·L-1悬液作用BGC-823细胞24,48和72h,MTT法检测细胞增殖,比色法检测乳酸脱氢酶(LDH)漏出量。ACNP100mg·L-1,纳米SiO2200mg·L-1,纳米TiO2200mg·L-1作用BGC-823细胞24h,透射电镜观察细胞形态及超微结构的影响。纳米SiO2和纳米TiO2100,200,400mg·L-1作用细胞24h后,AnnexinⅤ-FITC/PI双染法检测细胞凋亡。ACNP、纳米SiO2和纳米TiO2100,200mg·L-1作用细胞48h后,用PI染色法检测细胞周期。结果 ACNP,纳米SiO2和纳米TiO2均能明显抑制BGC-823细胞的增殖,作用72h后的IC50分别为874.2,676.2和883.5mg·L-1。与正常对照组相比,纳米SiO2100～800mg·L-1组LDH漏出量均显著升高,并呈浓度依赖性(r=0.9751,P<0.01),而纳米TiO2100mg·L-1作用细胞24h,LDH漏出量与对照组相比没有显著差异,但随着作用浓度增加和作用时间延长,各组LDH漏出量明显高于对照组(P<0.05)。ACNP100mg·L-1作用24h后,细胞出现细胞质浓缩、细胞核固缩和裂解。纳米SiO2200mg·L-1和纳米TiO2200mg·L-1作用24h后均出现细胞坏死。纳米颗粒ACNP,SiO2和TiO2作用组均可见纳米颗粒进入细胞及线粒体损伤。纳米SiO2100mg·L-1和纳米TiO2100mg·L-1作用24h,细胞坏死率与正常对照组(4.59±1.20)%相比显著升高(P<0.01),分别为(39.40±1.72)%和(14.12±0.90)%(P<0.05);细胞凋亡率与对照组相比没有显著差异。ACNP,纳米SiO2和纳米TiO2100和200mg·L-1作用细胞48h后,S期细胞增多,G0/G1期细胞减少,细胞碎片增多;ACNP组亚二倍体细胞增多。结论 ACNP、纳米SiO2和纳米TiO2能够抑制BGC-823细胞的增殖。ACNP可诱导细胞凋亡。纳米SiO2和纳米TiO2能损伤细胞膜,造成以细胞坏死为主的毒性损伤。     

Biological effect of food additive titanium dioxide nanoparticles on intestine: an in vitro study

Titanium dioxide nanoparticles (TiO₂ NPs) are widely found in food‐related consumer products. Understanding the effect of TiO₂ NPs on the intestinal barrier and absorption is essential and vital for the safety assessment of orally administrated TiO₂ NPs. In this study, the cytotoxicity and translocation of two native TiO₂ NPs, and these two TiO₂ NPs pretreated with the digestion simulation fluid or bovine serum albumin were investigated in undifferentiated Caco‐2 cells, differentiated Caco‐2 cells and Caco‐2 monolayer. TiO₂ NPs with a concentration less than 200 µg ml^–1 did not induce any toxicity in differentiated cells and Caco‐2 monolayer after 24 h exposure. However, TiO₂ NPs pretreated with digestion simulation fluids at 200 µg ml^–1 inhibited the growth of undifferentiated Caco‐2 cells. Undifferentiated Caco‐2 cells swallowed native TiO₂ NPs easily, but not pretreated NPs, implying the protein coating on NPs impeded the cellular uptake. Compared with undifferentiated cells, differentiated ones possessed much lower uptake ability of these TiO₂ NPs. Similarly, the traverse of TiO₂ NPs through the Caco‐2 monolayer was also negligible. Therefore, we infer the possibility of TiO₂ NPs traversing through the intestine of animal or human after oral intake is quite low. This study provides valuable information for the risk assessment of TiO₂ NPs in food. Copyright © 2015 John Wiley & Sons, Ltd.     

Tissue distribution and histopathological effects of titanium dioxide nanoparticles after intravenous or subcutaneous injection in mice

Nanoparticles can be formed following degradation of medical devices such as orthopedic implants. To evaluate the safety of titanium alloy orthopedic materials, data are needed on the long‐term distribution and tissue effects of injected titanium nanoparticles in experimental animals. In this study, we evaluated the tissue distribution and histopathological effects of titanium dioxide (TiO₂) nanoparticles (approximately 120 nm diameter) in mice after intravenous (i.v.; 56 or 560 mg kg^?1 per mouse) or subcutaneous (s.c.; 560 or 5600 mg kg^?1 per mouse) injection on two consecutive days. Animals were examined 1 and 3 days, and 2, 4, 12 and 26 weeks after the final injection. When examined by light microscopy, particle agglomerates identified as TiO₂ were observed mainly in the major filtration organs – liver, lung and spleen – following i.v. injection. Particles were still observed 26 weeks after injection, indicating that tissue clearance is limited. In addition, redistribution within the histological micro‐compartments of organs, especially in the spleen, was noted. Following s.c. injection, the largest particle agglomerates were found mainly in the draining inguinal lymph node, and to a lesser extent, the liver, spleen and lung. With the exception of a foreign body response at the site of s.c. injection and the appearance of an increased number of macrophages in the lung and liver, there was no histopathological evidence of tissue damage observed in any tissue at any time point. Published 2011. This article is a US Government work and is in the public domain in the USA.     

Application of titanium dioxide (TiO2) nanoparticles in cancer therapies

Abstract

Cancer is one of the most common diseases all over the world; many people suffer from diverse types of cancer. However, currently there is no exact cure or therapy developed for cancer. On the other hand, nanoparticles are defined as microscopic particles that have dimensions less than 100?nm and they are known for their usage in health sciences and medicine, however a few harmful effects on different animal cells. Therefore, researchers began to use nanoparticles for cancer therapies and to develop new methods for much more effective therapies. Nanoparticles in cancer studies are commonly used in photodynamic therapy (PDT) and sonodynamic therapy (SDT) as a sensitising agent, in computed tomography imaging (CT) and radiation therapy as an enhancement agent, in dual-mode image contrast and enhancement therapy as an image contrast agent. Titanium dioxide nanoparticles (TiO₂ NPs) are known as commonly used nanoparticles in medical applications and hence in cancer studies. They are used in PDT, SDT and drug delivery systems. As cancer continues to affect people, new therapeutics and therapies will be developed and nanotechnology for this aim will be an important approach for the researchers.     

纳米氧化钛对大鼠神经胶质细胞的毒性作用

目的研究纳米氧化钛(nano-TiO2)对大鼠神经胶质细胞的毒性作用。方法①体外实验:制备3种粒径10,20和200nm的nano-TiO2颗粒悬液,分别以6.25,12.5,25,50和100mg·L-1对大鼠星形胶质细胞进行72h染毒培养,应用磺基罗丹明B法检测nano-TiO2对星形胶质细胞存活率的影响。②体内实验:Wistar大鼠气管内分别注入上述3种粒径的nano-TiO2悬液,每种粒径设0.1,1.0和10.0mg·kg-13个剂量组,每组3只,72h后分别用电感耦合等离子质谱和放射免疫法检测大鼠脑组织中nano-TiO2的含量和白细胞介素1β(IL-1β)、肿瘤坏死因子α(TNF-α)和IL-10水平的变化,并通过光学显微镜和透射电镜观察nano-TiO2对大鼠神经胶质细胞形态的影响。结果①体外实验发现,nano-TiO2对大鼠星形胶质细胞存活率的抑制作用具有明显的浓度-效应关系,3种粒径10,20和200nm的nano-TiO2与胶质细胞培养72h,其半数抑制浓度分别为55.9,66.0和3827.0mg·L-1;细胞形态亦发生明显变化,细胞排列稀疏,间隙增大,胞内颗粒物增多,细胞透明度下降。②体内实验发现,粒径10和20nm的nano-TiO20.1mg·kg-1及粒径200nm的nano-TiO20.1,1.0和10.0mg·kg-1组,大鼠脑组织中的nano-TiO2,IL-1β,TNF-α及IL-10浓度与对照组比较无明显变化;粒径10和20nm的nano-TiO21.0及10.0mg·kg-1组大鼠脑组织中nano-TiO2,IL-1β,TNF-α及IL-10浓度随nano-TiO2剂量的增加而增加;病理学观察结果表明,nano-TiO2破坏大鼠血脑屏障,造成脑组织坏死,并进入神经胶质细胞内,引起炎症反应和细胞水肿。结论Nano-TiO2对大鼠神经胶质细胞具有细胞毒性作用,其作用强度与粒径大小有关,其作用机制可能与诱导炎症反应有关。     

The immunomodulatory effects of titanium dioxide and silver nanoparticles

Due to their characteristic physical, chemical and optical properties, titanium dioxide and silver nanoparticles are attractive tools for use in a wide range of applications. The use of nanoparticles for biological applications is, however, dependent upon their biocompatibility with living cells. Because of the importance of inflammation as a modulator of human health, the safe and efficacious in vivo use of titanium dioxide and silver nanoparticles is inherently linked to a favorable interaction with immune system cells. However, both titanium dioxide and silver nanoparticles have demonstrated potential to exert immunomodulatory and immunotoxic effects. Titanium dioxide and silver nanoparticles are readily internalized by immune system cells, may accumulate in peripheral lymphoid organs, and can influence multiple manifestations of immune cell activity. Although the factors influencing the biocompatibility of titanium dioxide and silver nanoparticles with immune system cells have not been fully elucidated, nanoparticle core composition, size, concentration and the duration of cell exposure seem to be important. Because titanium dioxide and silver nanoparticles are widely utilized in pharmaceutical, commercial and industrial products, it is vital that their effects on human health and immune system function be more thoroughly evaluated.     

Effect of titanium dioxide nanoparticles on glucose homeostasis after oral administration

As food additives, titanium dioxide nanoparticles (TiO₂ NPs) have been widely used in various products that are usually simultaneously consumed with a high content of sugar, thus necessitating research on the effect of TiO₂ NPs on glucose homeostasis. We conducted an animal study to explore the effect of orally administrated TiO₂ NPs on glucose absorption and metabolism in rats at 0, 2, 10 and 50 mg kg^–1 body weight day^–1 for 30 and 90 days. The results showed that oral exposure to TiO₂ NPs caused a slight and temporary hypoglycemic effect in rats at 30 days post‐exposure but recovered at 90 days post‐exposure. Decreased levels of intestinal glucose absorption and increased levels of hepatic glucose metabolism may be responsible for the hypoglycemic effect. Remodeling of the villi in the small intestine that decreased the surface area available for glucose absorption and increased levels of hepatic glucose uptake, utilization and storage related to hepatocellular injury are supposed to be the mechanisms. Our results demonstrated that dietary intake of TiO₂ NPs as food additives could affect the absorption and metabolism of glucose.     

The toxic effects of titanium dioxide nanoparticles on plasma glucose metabolism are more severe in developing mice than in adult mice

Titanium dioxide nanoparticles (TiO₂ NPs) are authorized food additives, and children have the highest exposure. Therefore, children are likely more susceptible to the adverse effects of TiO₂ NPs than adults. Previous study showed that oral administration of 50 mg/kg body weight (bw) TiO₂ NPs increase plasma glucose in mice. However, few studies have directly compared the adverse effects of exposure to TiO₂ NPs on plasma glucose metabolism of different age groups. In this study, the developing (age 3 weeks) and adult mice (age 10 weeks) were orally administered with 50 mg/kg bw TiO₂ NPs per day. The TiO₂ NPs induced hyperglycemia earlier in the developing mice than in the adult mice. Then mechanisms were analyzed after mice were oral administration of TiO2 NPs for 8 weeks and 26 weeks, respectively. Results showed that the treatment with TiO₂ NPs activated xenobiotic biodegradation in livers of both developing and adult mice at the early stage. However, only in the developing mice, TiO₂ NPs induced endoplasmic reticulum (ER) stress in livers and increased reactive oxygen species in livers and sera in the early stage. The ER stress and ROS activated an inflammation response and mitogen‐activated protein kinase pathways, thereby inducing insulin resistance in the livers of developing mice at the early stage. The response of the adult mice was delayed, and these changes were observed in the late stage of the study. The results of this study all suggest that children are more susceptible than adults to the toxicity of orally administered TiO₂ NPs.     

Genotoxicity evaluation of titanium dioxide nanoparticles using the Ames test and Comet assay

Titanium dioxide nanoparticles (TiO₂‐NPs) are being used increasingly for various industrial and consumer products, including cosmetics and sunscreens because of their photoactive properties. Therefore, the toxicity of TiO₂‐NPs needs to be thoroughly understood. In the present study, the genotoxicity of 10nm uncoated sphere TiO₂‐NPs with an anatase crystalline structure, which has been well characterized in a previous study, was assessed using the Salmonella reverse mutation assay (Ames test) and the single‐cell gel electrophoresis (Comet) assay. For the Ames test, Salmonella strains TA102, TA100, TA1537, TA98 and TA1535 were preincubated with eight different concentrations of the TiO₂‐NPs for 4 h at 37 °C, ranging from 0 to 4915.2 µg per plate. No mutation induction was found. Analyses with transmission electron microscopy (TEM) and energy‐dispersive X‐ray spectroscopy (EDS) showed that the TiO₂‐NPs were not able to enter the bacterial cell. For the Comet assay, TK6 cells were treated with 0–200 µg ml^–1 TiO₂‐NPs for 24 h at 37 °C to detect DNA damage. Although the TK6 cells did take up TiO₂‐NPs, no significant induction of DNA breakage or oxidative DNA damage was observed in the treated cells using the standard alkaline Comet assay and the endonuclease III (EndoIII) and human 8‐hydroxyguanine DNA‐glycosylase (hOGG1)‐modified Comet assay, respectively. These results suggest that TiO₂‐NPs are not genotoxic under the conditions of the Ames test and Comet assay. Published 2012. This article is a US Government work and is in the public domain in the USA.     

Induction of chromosomal aberrations by carbon nanotubes and titanium dioxide nanoparticles in human lymphocytes in vitro

Abstract

We examined if three commercially available nanomaterials – short singlewall carbon nanotubes (SWCNTs), short multiwall carbon nanotubes (MWCNTs) and nanosized titanium dioxide anatase (TiO₂; primary particle size <25 nm) – can induce structural chromosomal aberrations (CAs) in cultures of isolated human lymphocytes. To find a suitable sampling time, the cells were treated with 6.25–300 μg/ml of the nanomaterials for 24, 48 and 72 h. The 48-h treatment was the most effective, inducing a dose-dependent increase in chromosome-type CAs (all materials) and chromatid-type CAs (SWCNTs and TiO₂ anatase). The 72-h treatment yielded a positive result with SWCNTs. None of the treatments significantly affected cell count or the mitotic index. Our results suggest that with nanomaterials a continuous treatment for about two cell cycles is needed for CA induction, possibly reflecting access of nanomaterials to the nucleus during the first mitosis or delayed secondary genotoxic effect associated with the inflammatory process.     

In situ quantification of diverse titanium dioxide nanoparticles unveils selective endoplasmic reticulum stress-dependent toxicity

Although titanium dioxide nanoparticles (TiO₂ NPs) have been extensively studied, their possible impact on health due to their specific properties supported by their size and geometry, remains to be fully characterized to support risk assessment. To further document NPs biological effects, we investigated the impact of TiO₂ NPs morphology on biological outcomes. To this end, TiO₂ NPs were synthesized as nanoneedles (NNs), titanate scrolled nanosheets (TNs), gel-sol-based isotropic nanoparticles (INPs) and tested for perturbation of cellular homeostasis (cellular ion content, cell proliferation, stress pathways) in three cell types and compared to the P25. We showed that TiO₂ NPs were internalized at various degrees and their toxicity depended on both titanium content and NPs shape, which impacted on intracellular calcium homeostasis thereby leading to endoplasmic reticulum stress. Finally, we showed that a minimal intracellular content of TiO₂ NPs was mandatory to induce toxicity enlightening once more the crucial notion of internalized dose threshold beside the well-recognized dose of exposure.     

Using physiologically based pharmacokinetic (PBPK) modeling for dietary risk assessment of titanium dioxide (TiO2) nanoparticles

Abstract

Nano-sized titanium dioxide particles (nano-TiO₂) can be found in a large number of foods and consumer products, such as cosmetics and toothpaste, thus, consumer exposure occurs via multiple sources, possibly involving different exposure routes. In order to determine the disposition of nano-TiO₂ particles that are taken up, a physiologically based pharmacokinetic (PBPK) model was developed. High priority was placed on limiting the number of parameters to match the number of underlying data points (hence to avoid overparameterization), but still reflecting available mechanistic information on the toxicokinetics of nano-TiO₂. To this end, the biodistribution of nano-TiO₂ was modeled based on their ability to cross the capillary wall of the organs and to be phagocytosed in the mononuclear phagocyte system (MPS). The model’s predictive power was evaluated by comparing simulated organ levels to experimentally assessed organ levels of independent in vivo studies. The results of our PBPK model indicate that: (1) within the application domain of the PBPK model from 15 to 150?nm, the size and crystalline structure of the particles had a minor influence on the biodistribution; and (2) at high internal exposure the particles agglomerate in vivo and are subsequently taken up by macrophages in the MPS. Furthermore, we also give an example on how the PBPK model may be used for risk assessment. For this purpose, the daily dietary intake of nano-TiO₂ was calculated for the German population. The PBPK model was then used to convert this chronic external exposure into internal titanium levels for each organ.     

Inflammatory response of mice to manufactured titanium dioxide nanoparticles: Comparison of size effects through different exposure routes

TiO₂ is a widely used manufactured nanomaterial and the opportunity for human exposure makes it necessary to study its health implications. Using murine models for inflammation, size effects of inflammatory response in instillation and acute inhalation exposures of TiO₂ nanoparticles with manufacturers’ average particles sizes of 5 and 21 nm were investigated. The properties of the primary nanoparticles, nanoparticle agglomerates aerosol and instillation solution for both sized nanoparticles were evaluated. Mice were acutely exposed in a whole-body exposure chamber or through nasal instillation and toxicity was assessed by enumeration of total and differential cells, determination of total protein, LDH activity and inflammatory cytokines in BAL fluid. Lungs were also evaluated for histopathological changes. Results show the larger TiO₂ nanoparticles were found to be moderately, but significantly, more toxic. The nanoparticles had different agglomeration states which may be a factor as important as the surface and physical characteristics of the primary nanoparticles in determining toxicity.     

The effect and underlying mechanisms of titanium dioxide nanoparticles on glucose homeostasis: A literature review

Titanium dioxide (TiO₂) is used extensively as a white pigment in the food industry, personal care, and a variety of products of everyday use. Although TiO₂ has been categorized as a bioinert material, recent evidence has demonstrated different toxicity profiles of TiO₂ nanoparticles (NPs) and a potential health risk to humans. Studies indicated that titanium dioxide enters the systemic circulation and accumulates in the lungs, liver, kidneys, spleen, heart, and central nervous system and may cause oxidative stress and tissue damage in these vital organs. Recently, some studies have raised concerns about the possible detrimental effects of TiO₂ NPs on glucose homeostasis. However, the findings should be interpreted with caution due to the methodological issues. This article aims to evaluate current evidence regarding the effects of TiO₂ NPs on glucose homeostasis, including possible underlying mechanisms. Furthermore, the limitations of current studies are discussed, which may provide a comprehensive understanding and new perspectives for future studies in this field.     

Food‐grade titanium dioxide (E171) by solid or liquid matrix administration induces inflammation,germ cells sloughing in seminiferous tubules and blood‐testis barrier disruption in mice

Food‐grade titanium dioxide labeled as E171 has been approved for human consumption by the Food and Drug Administration (USA) and by the European Union for five decades. However, titanium dioxide has been classified as a possible carcinogen for humans by the International Agency of Research in Cancer raising concerns of its oral intake and the translocation to bloodstream, which could disturb barriers such as the blood‐testis barrier. There is evidence that titanium dioxide by intragastric/intraperitoneal/intravenous administration induced alterations on testosterone levels, testicular function and architecture, but studies of the E171 effects on the testicle structure and blood‐testis barrier are limited. E171 is contained not only in foods in liquid matrix but also in solid ones, which can exert different biological effects. We aimed to compare the effects of E171 consumption in a solid matrix (0.1%, 0.5% and 1% in pellets) and liquid suspension (5 mg/kg body weight) on testis structure, inflammation infiltrate and blood‐testis barrier disruption of male BALB/c mice. Results showed that none of the administration routes had influence on body weight but an increase in germ cell sloughing and the infiltrate of inflammatory cells in seminiferous tubules, together with disruption of the blood‐testis barrier were similar in testis of both groups even if the dose received in mice in liquid matrix was 136 or 260 times lower than the dose reached by oral intake in solid E171 pellets in 0.5% E171 and 1% E171, respectively. This study highlights the attention on matrix food containing E171 and possible adverse effects on testis when E171 is consumed in a liquid matrix.     

Genotoxicity of titanium dioxide nanoparticles

Titanium dioxide nanoparticles (TiO₂-NPs, <100 nm) are increasingly being used in pharmaceuticals and cosmetics due to the unique properties derived from their small sizes. However, their large surface-area to mass ratio and high redox potential may negatively impact human health and the environment. TiO₂-NPs can cause inflammation, pulmonary damage, fibrosis, and lung tumors and they are possibly carcinogenic to humans. Because cancer is a disease involving mutation, there are a large number of studies on the genotoxicity of TiO₂-NPs. In this article, we review the results that have been reported in the literature, with a focus on data generated from the standard genotoxicity assays. The data include genotoxicity results from the Ames test, in vitro and in vivo Comet assay, in vitro and in vivo micronucleus assay, sister chromatid exchange assay, mammalian cell hypoxanthine-guanine phosphoribosyl transferase gene assay, the wing somatic mutation and recombination assay, and the mouse phosphatidylinositol glycan, class A gene assay. Inconsistent results have been found in these assays, with both positive and negative responses being reported. The in vitro systems for assessing the genotoxicity of TiO₂-NPs have generated a greater number of positive results than the in vivo systems, and tests for DNA and chromosome damage have produced more positive results than the assays measuring gene mutation. Nearly all tests for measuring the mutagenicity of TiO₂-NPs were negative. The current data indicate that the genotoxicity of TiO₂-NPs is mediated mainly through the generation of oxidative stress in cells.     

Effects of titanium dioxide nanoparticles on human keratinocytes

Titanium dioxide (TiO₂) is a ubiquitous whitening compound widely used in topical products such as sunscreens, lotions and facial creams. The damaging health effects of TiO₂ inhalation has been widely studied in rats, mice and humans showing oxidative stress increase, DNA damage, cell death and inflammatory gene upregulation in lung and throat cells; however, the effects on skin cells from long-term topical use of various products remain largely unknown. In this study, we assessed the effect of specific TiO₂ nanoparticles (H₂TiO₇) on a human keratinocyte cell line (HaCaT). We performed a comparative analysis using three TiO₂ particles varying in size (Fine, Ultrafine and H₂TiO₇) and analyzed their effects on HaCaTs. There is a clear dose-dependent increase in superoxide production, caspase 8 and 9 activity, and apoptosis in HaCaTs after treatment with all three forms of TiO₂; however, there is no consistent effect on cell viability and proliferation with either of these TiO₂ particles. While there is data suggesting UV exposure can enhance the carcinogenic effects of TiO₂, we did not observe any significant effect of UV-C exposure combined with TiO₂ treatment on HaCaTs. Furthermore, TiO₂-treated cells showed minimal effects on VEGF upregulation and Wnt signaling pathway thereby showing no potential effect on angiogenesis and malignant transformation. Overall, we report here an increase in apoptosis, which may be caspase 8/Fas-dependent, and that the H₂TiO₇ nanoparticles, despite their smaller particle size, had no significant enhanced effect on HaCaT cells as compared to Fine and Ultrafine forms of TiO₂.