Influence of different sizes of titanium dioxide nanoparticles on hepatic and renal functions in rats with correlation to oxidative stress

The Nephroprotective Effect of In Utero Administration of Green Synthesized Titanium Dioxide Nanoparticles in Albino Rats

Titanium dioxide nanoparticles (TiO2-NPs) are one of the most popular nanoscale materials and have a wide range of applications in the manufacturing industry; nonetheless, researchers' focus has been directed to the detrimental consequences of TiO2-NPs. The current study was designed to assess the potential hazardous effects of chemically synthesized TiO2-NPs on the placenta and feto-maternal kidneys of rats. On the other hand, the probable positive impact of TiO2-NPs made after green synthesis was also evaluated. HepG2 cell lines were used to assess the cytotoxicity of chemical and green TiO2-NPs. Five groups of fifty pregnant female rats were formed (n=10). The first (control) group received distilled water. The second and third groups were orally given 100 and 300 mg/kg body weight (bw) of chemical TiO2-NPs, respectively. The fourth and fifth groups were orally given 100 and 300 mg/kg bw of green synthesized TiO2-NPs, respectively. On gestational day 20 (GD 20), blood and tissues were collected for biochemical and histological studies. Our findings revealed that chemical TiO2-NPs induced apoptosis in HepG2 cells at high concentrations, while there was no observed toxicity for green TiO2-NPs. The chemically treated TiO2-NPs groups showed a significant decrease in the level of HDL and a significant increase in cholesterol, LDL-cholesterol, and triglyceride levels. Renal tissues showed necrosis with exfoliation of lining epithelial cells, degenerated tubules, and glomerulonephritis. While the placenta was atrophied and hyalinized. Moreover, Bax expression significantly increased in the renal tubular cells and the villi of the placenta. Contrariwise, green TiO2-NPs-treated groups showed a significant rise in HDL levels with a significant reduction in triglycerides and LDL levels, while cholesterol levels were unaffected. Also, renal tissues showed mild degenerative changes in the glomeruli and renal tubules; thus, noticeable regeneration of epithelium lining tubules was detected in the maternal kidney. Bax showed a minimal reaction in the renal tubules and the villi of the placenta. It concluded that in contrast to chemical TiO2-NPs, biosynthesized TiO2-NPs with garlic showed a positive impact on the biochemical profile and histological investigations.

Sex-Specific Effects of Short-Term Oral Administration of Food-Grade Titanium Dioxide Nanoparticles in the Liver and Kidneys of Adult Rats

Titanium dioxide (TiO2) nanomaterial is used in several items (implant materials, pills composition, cosmetics, etc.). Although TiO2 is no longer considered safe as a food additive, the general population is exposed daily through different routes, and information is lacking on some aspects of animal and human health. This study evaluated liver and kidney toxicity of food-grade TiO2 nanoparticles (NPs) (primary size < 25 nm) in male and female rats that were orally exposed for 5 days to 0, 1, and 2 mg/kg body weight per day (comparable with daily E171 consumption). Selected liver and kidney toxicity endpoints included serum biomarkers, histopathological analysis and expression of osteopontin (SPP1), vascular endothelial growth factor (VEGF), interleukin 6 (IL-6), and neuropeptide Y (NPY). Although TiO2 NPs are known to affect the gastric mucosa, short-term exposure induced sex-specific effects: general toxicity parameters were predominantly altered in female rats, whereas the liver appeared to be more affected than the kidneys in male rats, which also showed overexpression of NPY and SPP1. In the kidneys, the TiO2 NP effects were quantitatively similar but qualitatively different in the two sexes. In conclusion, careful consideration should be paid to the presence of TiO2 NPs in other items that can lead to human exposure.

Damaging effects of TiO2 nanoparticles on the ovarian cells of Bombyx mori

As a new type of biologically compatible material, TiO₂ NPs are widely used in the industry as additives, drug carriers, and components of skin care products. Due to their wide use, residual TiO₂ NPs in the environment are a safety concern that has attracted extensive attention. In this study, the ovarian cell line BmN of the model organism Bombyx mori was used to reveal the damaging effects of TiO₂ NPs exposure. The results demonstrated that TiO₂ NPs exhibited a dose-dependent effect on the relative cell viability, with significant toxic effects being observed above 20 mg/L. Oxidative damage analysis showed that ROS accumulated significantly in BmN cells after exposure to TiO₂ NPs (P ≤ 0.05) and induced DNA damage. Further analysis revealed that the transcriptional levels of key superoxide dismutase genes (SOD) decreased significantly, while the transcriptions of key genes of the MAPK/NF-κB signaling pathway (P38, MEK, ERK and REL) and the downstream inflammatory factor genes (IL6 and TNFSF5) were all significantly up-regulated (P ≤ 0.05). Overall, our results indicate that exposure to TiO₂ NPs leads to reduced transcription of antioxidant genes, accumulation of peroxides, and inflammation. These findings provide valuable data for the safety evaluation of environmental residues of TiO₂ NPs.

Effects of Titanium Dioxide Nanoparticles on Porcine Prepubertal Sertoli Cells: An "In Vitro" Study

The increasing use of nanomaterials in a variety of industrial, commercial, medical products, and their environmental spreading has raised concerns regarding their potential toxicity on human health. Titanium dioxide nanoparticles (TiO2 NPs) represent one of the most commonly used nanoparticles. Emerging evidence suggested that exposure to TiO2 NPs induced reproductive toxicity in male animals. In this in vitro study, porcine prepubertal Sertoli cells (SCs) have undergone acute (24 h) and chronic (from 1 up to 3 weeks) exposures at both subtoxic (5 µg/ml) and toxic (100 µg/ml) doses of TiO2 NPs. After performing synthesis and characterization of nanoparticles, we focused on SCs morphological/ultrastructural analysis, apoptosis, and functionality (AMH, inhibin B), ROS production and oxidative DNA damage, gene expression of antioxidant enzymes, proinflammatory/immunomodulatory cytokines, and MAPK kinase signaling pathway. We found that 5 µg/ml TiO2 NPs did not induce substantial morphological changes overtime, but ultrastructural alterations appeared at the third week. Conversely, SCs exposed to 100 µg/ml TiO2 NPs throughout the whole experiment showed morphological and ultrastructural modifications. TiO2 NPs exposure, at each concentration, induced the activation of caspase-3 at the first and second week. AMH and inhibin B gene expression significantly decreased up to the third week at both concentrations of nanoparticles. The toxic dose of TiO2 NPs induced a marked increase of intracellular ROS and DNA damage at all exposure times. At both concentrations, the increased gene expression of antioxidant enzymes such as SOD and HO-1 was observed whereas, at the toxic dose, a clear proinflammatory stress was evaluated along with the steady increase in the gene expression of IL-1α and IL-6. At both concentrations, an increased phosphorylation ratio of p-ERK1/2 was observed up to the second week followed by the increased phosphorylation ratio of p-NF-kB in the chronic exposure. Although in vitro, this pilot study highlights the adverse effects even of subtoxic dose of TiO2 NPs on porcine prepubertal SCs functionality and viability and, more importantly, set the basis for further in vivo studies, especially in chronic exposure at subtoxic dose of TiO2 NPs, a condition closer to the human exposure to this nanoagent.

Nickel nanoparticles induce hepatotoxicity via oxidative and nitrative stress-mediated apoptosis and inflammation

Nickel nanoparticles (Ni NPs) are utilized extensively in various industrial applications. However, there are increasing concerns about potential exposure to Ni NPs and consequent health effects. The aim of this study was to assess Ni NPs-induced liver toxicity in Sprague Dawley rats. Twenty-five rats were exposed to Ni NPs via intraperitoneal injection at doses of 15, 30, and 45 mg/kg per body weight for 28 days. Results from ICP-MS analysis showed an increase in the concentration of Ni NPs in a dose-dependent manner. The liver dysfunction was indicated by considerable production of ALT, AST, ALP, LDH, and TB in Ni NPs-treated rats. Histological examination demonstrated liver injuries (inflammatory cells, congestion, necrosis, and pyknosis) in exposed rats with dose-dependent severity of pathologies by semi-quantitative histograding system. To explore the toxicological pathways, we examined oxidative stress biomarkers and detected Ni NPs significantly elevated the levels of MDA and LPO while decreasing the levels of CAT and GSH. All the changes in biomarkers were recorded in a dose-dependent relationship. In addition, we found upregulated NF-kβ indicating activation of inflammatory cytokines. ELISA results of serum revealed a remarkable increase of nitrative stress markers (iNOS and NO), ATPase activity, inflammatory cytokine (IL-6, IL-1β, and TNF-α), and apoptotic mediators (caspase-3 and caspase-9) in Ni NPs-treated groups than the control. In summary, the result of this study provided evidence of hepatotoxicity of Ni NPs and insightful information about the involved toxic pathways, which will help in health risk assessment and management, related preventive measures for the use of Ni-NPs materials.

Coenzyme Q10 protects isolated human blood cells from TiO2 nanoparticles induced oxidative/antioxidative imbalance, hemolysis, cytotoxicity, DNA damage and mitochondrial impairment

TiO₂ NPs have been investigated for their toxic potential and studies have reported their toxicity is due to generation of oxidative stress. In the present study, we investigated the toxicity of TiO₂ NPs and explored the potential of well-known antioxidant coenzyme Q10 (CoQ10) in counteracting the NP-induced toxicity in isolated human blood cells. When the isolated blood cells were treated with varying concentrations of TiO₂ NPs (25-100 μg/ml), only 50 μg/ml dose induced statistically significant hemolysis in erythrocytes and cytotoxicity in lymphocytes (p < 0.05). None of the concentrations induced any significant increase in platelet aggregation. To investigate the protective effect of CoQ10, we incubated the isolated blood cells with 50 μg/ml of TiO₂ NPs in the presence and absence of 25 μM of CoQ10 for 3 h. Hemolysis, oxidative stress, LDH leakage and ATPase enzyme activity were studied in erythrocytes; cytotoxic and DNA damaging potential of NPs were determined in lymphocytes, along with mitochondrial membrane potential (MMP) and ADP/ATP ratio. Hemolysis, generation of oxidative stress, LDH leakage and reduced ATPase activity were observed in the erythrocytes treated with NPs alone (50 μg/ml), the results were statistically significant at p < 0.05. Oxidative stress was evident by increased levels of malonaldehyde, indicating lipid peroxidation and generation of reactive oxygen species including hydrogen peroxide, together with statistically significant decrease in the activities of catalase and superoxide dismutase and reduced glutathione levels. In the lymphocytes treated with NPs alone (50 μg/ml), cytotoxicity in MTT assay and DNA damage in comet assay were observed; in addition, mitochondrial membrane potential collapsed and ADP/ATP ratio increased indicating mitochondrial function impairment. However, in the presence of CoQ10, hemolysis, oxidative stress and LDH leakage in the erythrocytes and lymphocyte cytotoxicity and DNA damage were drastically reduced, enzyme activities, MMP and ADP/ATP ratio were restored towards normal levels. TiO₂ NPs induce cytotoxicity, damage DNA in lymphocytes, and induce oxidative/anti-oxidative imbalance in erythrocytes. Antioxidant CoQ10 protects erythrocytes and lymphocytes from toxicity induced by TiO₂ NPs.

Eugenol attenuates TiO2 nanoparticles-induced oxidative damage, biochemical toxicity and DNA damage in Wistar rats: an in vivo study

Titanium dioxide nanoparticles (TiO2 NPs) are widely used in food, edible dyes, and other commercial products. Human exposure to TiO2 NPs has raised concerns regarding their toxic potential. Various studies have evaluated the TiO2 NPs-induced toxicity, oxidative damage to the cellular components, and genotoxicity. In the present study, we examined whether co-treatment with the dietary antioxidant eugenol can attenuate or protect against TiO2 NPs-induced toxicity. We exposed the adult male Wistar rats to TiO2 NPs (150 mg/kg body weight) by intraperitoneal injection (i.p.) either alone or as co-treatment with eugenol (1-10 mg/kg body weight) once a day for 14 days. The untreated rats were supplied saline and served as control. Titanium (Ti) accumulation in various tissues was analyzed by inductively coupled plasma mass spectrometry. Serum levels of liver and kidney biomarkers and oxidative stress markers in the liver, kidney, and spleen were determined. A significant increase in hydrogen peroxide level confirmed that oxidative stress occurred in these tissues. TiO2 NPs induced oxidation of lipids, and decreased glutathione level and antioxidant enzyme activity in the kidney, liver, and spleen of treated rats. TiO2 NPs also increased the serum levels of alanine aminotransferase, alkaline phosphatase, aspartate aminotransferase, albumin, and total cholesterol and decreased the blood urea nitrogen, uric acid, and total bilirubin in serum, which indicates oxidative damage to the liver and kidney. In eugenol and TiO2 NPs co-treated rats, all these changes were mitigated. Single-cell gel electrophoresis (comet assay) of lymphocytes showed longer comet tail length in TiO2 NPs-treated groups, indicating DNA damage while tail length was reduced in eugenol and TiO2 NPs co-treated groups. Thus, it seems that eugenol can be used as a chemoprotective agent against TiO2 NPs-induced toxicity.

Titanium dioxide nanoparticles induced the apoptosis of RAW264.7 macrophages through miR-29b-3p/NFAT5 pathway

Titanium dioxide nanoparticles (TiO₂ NPs) are widely found in consumer and industrial products, contributing to their prevalent presence in our surroundings. In this study, several miRNAs in the immuno-related pathways were found to be dysregulated in RAW264.7 cells after 24-h exposure to TiO₂ NPs, including miR-29b-3p, which had not been previously found to be associated with the dysregulation of immunity after exposure to TiO₂ NPs. The KEGG pathway and GO enrichment analysis suggested that miR-29b-3p functioned both in the T and B cell receptor signaling pathways. The NFAT5 gene was predicted to regulate miR-29b-3p using the MiRDB online database. The expression of miR-29b-3p and NFAT5 was found to be inversely correlated using qRT-PCR and western blotting analysis. Dual-luciferase reporter gene assays demonstrated the precise regulatory relationship between miR-29b-3p and NFAT5. The upregulation of miR-29b-3p was found to reinforce the apoptosis of cells, while no changes were found in terms of the cell cycle or cell proliferation, using MTT, cell apoptosis, and cycle detection experiments. Our results demonstrate that miR-29b-3p is involved in the response of RAW264.7 cells to exposure to TiO₂, proving evidence for the further study of the toxicity and mechanisms of nano-TiO₂ exposure.

Oxidative Damage Induced by Nano-titanium Dioxide in Rats and Mice: a Systematic Review and Meta-analysis

Nano-titanium dioxide is a kind of widely used nanomaterial that exhibits various adverse outcomes. However, the role of oxidative stress in this regard remains controversial. This study aimed to evaluate whether oxidative stress is one of the toxicity mechanisms induced by nano-titanium dioxide in rats and mice model. In this meta-analysis, 64 relevant publications were included through detailed database search. The pooled results showed that nano-titanium dioxide exposure could promote the expression of oxidants, such as malonaldehyde (MDA), 8-hydroxy-2-deoxyguanosine (8-OHdG), superoxide anion (O₂^-), and hydrogen peroxide (H₂O₂). Meanwhile, the levels of antioxidant-related enzymes and molecules, such as superoxide dismutase (SOD), glutathione (GSH), glutathione peroxidase (GPx), and catalase (CAT), were reduced. Subgroup analysis revealed that different intervention routes, exposure periods, exposure dosages, and sample sources could affect the oxidative stress when exposed to nano-titanium dioxide. It was worth noting that the levels of MDA, 8-OHdG, and GSH significantly increased (P < 0.05) when the particle size of nano-titanium dioxide was < 10 nm, whereas H₂O₂, SOD, and GPx showed the highest effect at 10-40 nm. This study indicated that nano-titanium dioxide could cause oxidative damage by affecting the levels of enzymes and molecules involved in oxidative stress in rats and mice. And these results could provide a reference for studies of the toxicity mechanism induced by nano-titanium dioxide in the future.

Air pollution-derived particulate matter dysregulates hepatic Krebs cycle, glucose and lipid metabolism in mice

Exposure to ambient air particulate matter (PM_2.5) is well established as a risk factor for cardiovascular and pulmonary disease. Both epidemiologic and controlled exposure studies in humans and animals have demonstrated an association between air pollution exposure and metabolic disorders such as diabetes. Given the central role of the liver in peripheral glucose homeostasis, we exposed mice to filtered air or PM_2.5 for 16 weeks and examined its effect on hepatic metabolic pathways using stable isotope resolved metabolomics (SIRM) following a bolus of ¹³C₆-glucose. Livers were analyzed for the incorporation of ¹³C into different metabolic pools by IC-FTMS or GC-MS. The relative abundance of ¹³C-glycolytic intermediates was reduced, suggesting attenuated glycolysis, a feature found in diabetes. Decreased ¹³C-Krebs cycle intermediates suggested that PM_2.5 exposure led to a reduction in the Krebs cycle capacity. In contrast to decreased glycolysis, we observed an increase in the oxidative branch of the pentose phosphate pathway and ¹³C incorporations suggestive of enhanced capacity for the de novo synthesis of fatty acids. To our knowledge, this is one of the first studies to examine ¹³C₆-glucose utilization in the liver following PM_2.5 exposure, prior to the onset of insulin resistance (IR).

Quercetin Effects on Hepatotoxicity Induced by Titanium Dioxide Nanoparticles in Rats

Background: Most nanoparticles have adverse impacts on the liver, which is a vital body organ, by the induction of oxidative stress. Objectives: This study was designed to evaluate the hepatoprotective effects of quercetin (QCT) against the toxicity of nanoscale titanium dioxide (NTiO2) in Wistar rats. Methods: The present study was conducted on 32 adult female Wistar rats assigned into 4 groups of control, NTiO2 (50 mg/kg), NTiO2 + Quercetin (50 + 75 mg/kg), and Quercetin (75 mg/kg). The animals exposed to NTiO2 were administered by 50 mg/kg of NTiO2 for 21 days. The Quercetin + NTiO2 rats received Quercetin before exposing to NTiO2 for 7 days. Alanine aminotransferase (ALT), aspartate aminotransferase (AST), and alkaline phosphatase (ALP) of serum were considered indicators of the hepatotoxicity. The oxidative stress was assessed by measuring the activity of catalase (CAT) and superoxide dismutase (SOD) as well as the level of malondialdehyde (MDA) in the liver. TUNEL assay and histological changes were also assessed. Results: The NTiO2 significantly elevated the MDA level (P < 0.01), enhanced the serum biomarker levels, reduced the CAT (P < 0.01) and SOD (P < 0.01) activities. The NTiO2 also aggregated the red blood cells, and caused inflammatory cell infiltration, nuclear pyknosis and fat deposit in hepatocytes, as well as induced apoptosis in the liver tissue. Pretreatment with QCT quenched oxidative stress, attenuated the histological changes, elevated the CAT (P < 0.01) and SOD (P < 0.01) activities, normalized the serum biomarker levels and decreased apoptosis (P < 0.001). Conclusions: The QCT has an inhibitory impact on hepatotoxicity induced by nanoparticles in rats.

Hepatic and Renal Toxicity Induced by TiO2 Nanoparticles in Rats: A Morphological and Metabonomic Study

Titanium dioxide (TiO₂) nanoparticles (NPs) are produced abundantly and are frequently used as a white pigment in the manufacture of paints, foods, paper, and toothpaste. Despite the wide ranges of uses, there is a lack of information on the impact of NPs on animal and human health. In the present study, rats were exposed to different doses of TiO₂ nanoparticles and sacrificed, respectively, 4 days, 1 month, and 2 months after treatment. Dosage of TiO₂ in tissues was performed by ICP-AES and revealed an important accumulation of TiO₂ in the liver. The nanoparticles induced morphological and physiological alterations in liver and kidney. In the liver, these alterations mainly affect the hepatocytes located around the centrilobular veins. These cells were the site of an oxidative stress evidenced by immunocytochemical detection of 4-hydroxynonenal (4-HNE). Kupffer cells are also the site of an important oxidative stress following the massive internalization of TiO₂ nanoparticles. Enzymatic markers of liver and kidney functions (such as AST and uric acid) are also disrupted only in animals exposed to highest doses. The metabonomic approach allowed us to detect modifications in urine samples already detectable after 4 days in animals treated at the lowest dose. This metabonomic pattern testifies an oxidative stress as well as renal and hepatic alterations.

Short-term evaluation of hepatic toxicity of titanium dioxide nanofiber (TDNF)

Various in vitro and in vivo studies have shown titanium dioxide nanoparticles (TDNPs) increase the production of reactive oxygen species and change the expression of genes and proteins involved in the inflammatory response and cell division. Although, the cytotoxicity of TDNPs has been shown to be largely dependent on the characteristics of the particles including shape and surface area. This present study investigates the effects of titanium dioxide nanofibers (TDNFs) with a diameter of 300-800 nm, on the histopathology of liver tissue, changes in feed efficiency and liver weights, changes in hepatic gene expression, and serum biochemical parameters in male Sprague-Dawley rats. Male Sprague-Dawley rats were fed concentrations of 0 ppm, 40 ppm, and 60 ppm TDNF by oral gavage for two weeks. Selected inflammatory response, oxidative stress, and regulatory cell cycle genes were measured by quantitative real-time polymerase chain reaction (qRT-PCR). Differences in gene expression compared to the 0 ppm group were observed in genes Gnat3, IghA, IL-1β, p21, p53, and TNF-α. Histopathology, body and liver weights, and feed efficiency showed no significant differences. Albumin levels in all groups were not significantly higher than the reference range while ALT levels for all groups were high compared to the reference value. Currently, the results suggest TDNF does not exhibit significant hepatic toxicity. This may be explained by the rutile crystalline structure of the nanofibers, the lower concentration or the short duration of exposure toxic used during experimentation.

Uniform TiO2 nanoparticles induce apoptosis in epithelial cell lines in a size-dependent manner

The size of titanium dioxide (TiO₂) nanoparticles is a vital parameter that determines their cytotoxicity. However, most reported studies have employed irregular shapes and sizes of TiO₂ nanoparticles, as it is difficult to produce nanoparticles of suitable sizes for research. We produced good model TiO₂ nanoparticles of uniform shape and size for use in studying their cytotoxicity. In this work, spherical, uniform polyethylene glycol-modified TiO₂ (TiO₂-PEG) nanoparticles of differing sizes (100, 200, and 300 nm) were prepared using the sol-gel method. A size-dependent decrease in cell viability was observed with increasing nanoparticle size. Furthermore, apoptosis was found to be positively associated with nanoparticle size, as evidenced by an increase in caspase-3 activity with increasing nanoparticle size. Larger nanoparticles exhibited higher cellular uptake, suggesting that larger nanoparticles more strongly induce apoptosis. In addition, the cellular uptake of different sizes of nanoparticles was energy dependent, suggesting that there are size-dependent uptake pathways. We found that 100 and 200 nm (but not 300 nm) nanoparticles were taken up via clathrin-mediated endocytosis. These results utilizing uniform nanoparticles suggest that the size-dependent cytotoxicity of nanoparticles involves active cellular uptake, caspase-3 activation, and apoptosis in the epithelial cell line (NCI-H292). These findings will hopefully aid in the future design and safe use of nanoparticles.

Molecular mechanism for miR-350 in regulating of titanium dioxide nanoparticles in macrophage RAW264.7 cells

This study investigated the role of microRNA(miRNA) in regulating the cytotoxicity of TiO₂ nanoparticles (nano-TiO₂) to RAW264.7 cells. RAW264.7 cells were treated with 0 and 100 μg/ml nano-TiO₂ for 24 h (for miRNA analysis). The differentially expressed miRNAs were detected using Illumina HiSeq™ 2000 sequencing. Through the bio-informatics analysis, miR-350 was found to play an important role in multiple signaling pathways, including MAPK signaling pathway, NF-kappa B signaling pathway and Apoptosis. To characterize the miR-350 function, miR-350 mimic was transfected into RAW264.7 cells for 24 h. MTT and Flow Cytometry were performed to detect cell proliferation, apoptosis and cell cycle (repetition), respectively. QRT-PCR, Western Blot methods and Luciferase assays were applied to detect expression of putative target gene PIK3R3. The results showed that miRNA profiles were differentially dysregulated. The apoptosis rate of miR-350 mimic group was significantly higher than negative control group (p < .05). Cell proliferation and cell cycle had no significant differences between treatment and negative control group. Compared with negative control, the level of protein of PIK3R3 was significantly decreased (p < .05), and the expression of 3'UTR constructs of PIK3R3 was significantly decreased (p < .05) in miR-350 mimic group. The expression of miRNAs was changed after exposed to nano-TiO₂, and biological function and target gene results showed miR-350 may promote RAW264.7 cell apoptosis through the negative regulation of PIK3R3 gene. Our results could provide a basis for further understanding of toxicity and possible mechanisms of nano-TiO₂ exposure.

Reproductive toxicity provoked by titanium dioxide nanoparticles and the ameliorative role of Tiron in adult male rats

Titanium dioxide nanoparticles (TDN) are widely used in paints, plastics, ceramics, cosmetics, printing ink, rubber and paper. Tiron is a water soluble metal chelator and antioxidant. This study was designed to investigate the reproductive toxicity of TDN in male albino rats and the ameliorative role of Tiron to minimize such toxic effects. Eighty adult male albino rats were assigned into 4 equal groups, group 1: control; group 2: received TDN at 100 mg/kg/day orally for 8 weeks; group 3: received Tiron at 470 mg/kg/day intraperitoneally for 2 weeks (the last 2 weeks of the experimental period); group 4: received both TDN and Tiron by the same previously mentioned dose, route and duration. The results revealed that TDN provoked reproductive toxicity which was proved by the deteriorated spermogram picture, high incidence of micronucleated RBCs, elevated oxidative stress parameters and up regulation of Testin gene. Whereas, Tiron co-treatment ameliorated most of these toxic alterations. Our findings highlighted the protective role of tiron against TDN intoxication.

Progress of in vivo studies on the systemic toxicities induced by titanium dioxide nanoparticles

Titanium dioxide nanoparticles (TiO2 NPs) are inorganic materials with a diameter of 1-100 nm. In recent years, TiO2 NPs have been used in a wide range of products, including food, toothpaste, cosmetics, medicine, paints and printing materials, due to their unique properties (high stability, anti-corrosion, and efficient photocatalysis). Following exposure via various routes including inhalation, injection, dermal deposition and gastrointestinal tract absorption, NPs can be found in various organs in the body potentially inducing toxic effects. Thus more attention to the safety of TiO2 NPs is necessary. Therefore, the present review aims to provide a comprehensive evaluation of the toxic effects induced by TiO2 NPs in the lung, liver, stomach, intestine, kidney, spleen, brain, hippocampus, heart, blood vessels, ovary and testis of mice and rats in in vivo experiments, and evaluate their potential toxic mechanisms. The findings will provide an important reference for human risk evaluation and management following TiO2 NP exposure.

Impact of acute and chronic inhalation exposure to CdO nanoparticles on mice

Cadmium nanoparticles can represent a risk in both industrial and environmental settings, but there is little knowledge on the impacts of their inhalation, especially concerning longer-term exposures. In this study, mice were exposed to cadmium oxide (CdO) nanoparticles in whole body inhalation chambers for 4 to 72 h in acute and 1 to 13 weeks (24 h/day, 7 days/week) in chronic exposure to investigate the dynamics of nanoparticle uptake and effects. In the acute experiment, mice were exposed to 2.95 × 10⁶ particles/cm³ (31.7 μg CdO/m³). The same concentration and a lower one (1.18 × 10⁶ particles/cm³, 12.7 μg CdO/m³) were used for the chronic exposure. Transmission electron microscopy documented distribution of nanoparticles into all studied organs. Major portion of nanoparticles was retained in the lung, but longer exposure led to a greater relative redistribution into secondary organs, namely the kidney, and also the liver and spleen. Accumulation of Cd in the lung and liver occurred already after 24 h and in the brain, kidney, and spleen after 72 h of exposure, and a further increase of Cd levels was observed throughout the chronic exposure. There were significant differences in both Cd accumulation and effects between the two exposure doses. Lung weight in the higher exposure group increased up to 2-fold compared to the control. Histological analyses showed dose-dependent alterations in lung and liver morphology and damage to their tissue. Modulation of oxidative stress parameters including glutathione levels and increased lipid peroxidation occurred mainly after the greater chronic exposure. The results emphasize risk of longer-term inhalation of cadmium nanoparticles, since adverse effects occurring after shorter exposures gradually progressed with a longer exposure duration.

Contribution of oxidative stress to TiO2 nanoparticle-induced toxicity

With the rapid development of nanotechnology, titanium dioxide nanoparticles (TNPs) are widely used in many fields. People in such workplaces or researchers in laboratories are at a higher risk of being exposed to TNPs, so are the consumers. Moreover, increasing evidence revealed that the concentrations of TNPs are elevated in animal organs after systematic exposure and such accumulated TNPs could induce organ dysfunction. Although cellular responses such as oxidative stress, inflammatory response, apoptosis, autophagy, signaling pathways, and genotoxic effects contribute to the toxicity of TNPs, the interrelationship among them remains obscure. Given the pivotal role of oxidative stress, we summarized relevant articles covering the involvement of oxidative stress in TNPs' toxicity and found that TNP-induced oxidative stress might play a central role in toxic mechanisms. However, available data are far from being conclusive and more investigations should be performed to further confirm whether the toxicity of TNPs might be attributed in part to the cascades of oxidative stress. Tackling this uncertain issue may help us to comprehensively understand the interrelationship among toxic cellular responses induced by TNPs and might shed some light on methods to alleviate toxicity of TNPs.

Toxic Effects of Titanium Dioxide Nanoparticles and Titanium Dioxide Bulk Salt in the Liver and Blood of Male Sprague-Dawley Rats Assessed by Different Assays

This study evaluated the toxic effects of titanium dioxide (TiO2) bulk salt as well as its nanoparticles (NPs) in anatase phase with mean crystallite size of 36.15 nm in male Sprague-Dawley rats by subcutaneous injections at four different dose levels of either control (0), 50, 100 or 150 mg/kg of body weight (BW) of rat for 28 days on alternate days. Animal mortality, haematology, micronucleus assay, liver histology and activities of liver tissue damage markers like, alkaline phosphate (ALP), alanine transaminase (ALT), aspartate transaminase (AST), as well as oxidative stress indicators like superoxide dismutase (SOD), catalase (CAT), glutathione S-transferase (GST), reduced glutathione (GSH) and lipid peroxidation (LPO) were investigated. The study revealed significant differences (P < 0.05) among control and experimental groups in all the haematological parameters at the end of experiment. Significantly elevated levels (P < 0.05) of ALT, AST and ALP were found for the group treated with TiO2 NPs at the dose of 150 mg/kg of body weight as compared to control. TiO2 and TiO2 NPs caused dose-dependent genotoxicity in the blood cells of the treated rat as revealed by micronuclei test. The highest frequency of micronuclei was observed in rats treated with NPs at the dose of 150 mg/kg BW which was significantly different (P < 0.001) from all other experimental groups after 28 days of exposure. Similarly, all the treatments showed dose-dependent oxidative stress in the treated rats. However, the significantly high decline in the activities of CAT, SOD, and GST as well as elevation in malondialdehyde and GSH was observed in the group receiving NPs at the rate of 150 mg/kg BW. TiO2 also caused histological alterations in the liver. The study revealed that higher dose of TiO2 NPs exerted significantly harmful effects on liver and blood as compared to its lower doses as well as from all other doses of their bulk counterparts.

Toxicity of Nano-Titanium Dioxide (TiO2-NP) Through Various Routes of Exposure: a Review

Nano-titanium dioxide (TiO2) is one of the most commonly used materials being synthesized for use as one of the top five nanoparticles. Due to the extensive application of TiO2 nanoparticles and their inclusion in many commercial products, the increased exposure of human beings to nanoparticles is possible. This exposure could be routed via dermal penetration, inhalation and oral ingestion or intravenous injection. Therefore, regular evaluation of their potential toxicity and distribution in the bodies of exposed individuals is essential. Keeping in view the potential health hazards of TiO2 nanoparticles for humans, we reviewed the research articles about studies performed on rats or other mammals as animal models. Most of these studies utilized the dermal or skin and the pulmonary exposures as the primary routes of toxicity. It was interesting that only very few studies revealed that the TiO2 nanoparticles could penetrate through the skin and translocate to other tissues, while many other studies demonstrated that no penetration or translocation could happen through the skin. Conversely, the TiO2 nanoparticles that entered through the pulmonary route were translocated to the brain or the systemic circulation from where these reached other organs like the kidney, liver, etc. In most studies, TiO2 nanoparticles appeared to have caused oxidative stress, histopathological alterations, carcinogenesis, genotoxicity and immune disruption. Therefore, the use of such materials in humans must be either avoided or strictly managed to minimise risks for human health in various situations.

Effects of titanium dioxide nanoparticles coupled with diode laser on optical properties of in vitro normal and cancerous human lung tissues studied with optical coherence tomography and diffuse reflectance spectra

The objective is to investigate the effects of two different sized (60 and 100 nm) titanium dioxide (TiO2) nanoparticles (NPs) penetration and accumulation in in vitro human normal lung (NL) tissue, lung squamous cell carcinoma (LSCC) tissue, and 650-nm diode laser-pretreated tissue on their optical properties studied with optical coherence tomography monitoring and diffuse reflectance (DR) spectra measurement. As with TiO2 NPs penetrating into the tissues, the intensities of DR of the samples increase, and then the enhancements of DR and the attenuation coefficients of the tissues were quantitatively calculated. The results suggest that 650-nm diode laser pretreatment increased the amounts of TiO2 NPs penetration and accumulation in NL and LSCC tissues, and the tissue optical properties were significantly influenced by accumulation of TiO2 NPs.

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

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

Neurotoxicity of nanoscale materials

Nanotechnology has been applied in consumer products and commercial applications, showing a significant impact on almost all industries and all areas of society. Significant evidence indicates that manufactured nanomaterials and combustion-derived nano-materials elicit toxicity in humans exposed to these nanomaterials. The interaction of the engineered nanomaterials with the nervous system has received much attention in the nanotoxicology field. In this review, the biological effects of metal, metal oxide, and carbon-based nanomaterials on the nervous system are discussed from both in vitro and in vivo studies. The translocation of the nanoparticles through the blood–brain barrier or nose to brain via the olfactory bulb route, oxidative stress, and inflammatory mechanisms of nanomaterials are also reviewed.

Effects of Th1 and Th2 cells balance in pulmonary injury induced by nano titanium dioxide

To explore the potential immunoregulatory mechanisms linking nano TiO₂ and pulmonary injury, Sprague Dawley rats were exposed by intra-tracheal instillation to nano TiO₂ with the individual doses of 0.5, 4.0 and 32 mg/kgb.w., micro TiO₂ with 32 mg/kgb.w. and 0.9% NaCl, respectively. The exposure was conducted twice a week, for four consecutive weeks. The results of lung histology demonstrated increased macrophages accumulation, extensive disruption of alveolar septa, slight alveolar thickness and expansion hyperemia. Mitochondria tumefaction organelles dissolution, endoplasmic reticulum expansion and the gap of nuclear broadening were shown. The changes of IFN-γ and IL-4 level showed no statistical difference. The mRNA expression of GATA-3 was up-regulated, whereas T-bet was significantly down-regulated. The protein expression of T-bet decreased and there were significant differences in nano 4 and 32 mg/kg groups. The imbalance of Th1/Th2 cytokines might be one of the mechanisms of immunotoxicity of respiratory system induced by nano TiO₂ particles.

Dispersion method for safety research on manufactured nanomaterials

Nanomaterials tend to agglomerate in aqueous media, resulting in inaccurate safety assessment of the biological response to these substances. The present study searched for suitable dispersion methods for the preparation of nanomaterial suspensions. Titanium dioxide (TiO2) and zinc oxide (ZnO) nanoparticles were dispersed in a biocompatible dispersion medium by direct probe-type sonicator and indirect cup-type sonicator. Size characterization was completed using dynamic light scattering and transmission electron microscopy. A series of dispersion time and output power, as well as two different particle concentrations were tested. Microscopic contamination of metal titanium that broke away from the tip of the probe into the suspension was found. Size of agglomerated nanoparticles decreased with increase in sonication time or output power. Particle concentration did not show obvious effect on size distribution of TiO2 nanoparticles, while significant reduction of secondary diameter of ZnO was observed at higher concentration. A practicable protocol was then adopted and sizes of well-dispersed nanoparticles increased by less than 10% at 7 d after sonication. Multi-walled carbon nanotubes were also well dispersed by the same protocol. The cup-type sonicator might be a useful alternative to the traditional bath-type sonicator or probe-type sonicator based on its effective energy delivery and assurance of suspension purity.

Rat pulmonary responses to inhaled nano-TiO₂: effect of primary particle size and agglomeration state

Background

The exact role of primary nanoparticle (NP) size and their degree of agglomeration in aerosols on the determination of pulmonary effects is still poorly understood. Smaller NP are thought to have greater biological reactivity, but their level of agglomeration in an aerosol may also have an impact on pulmonary response. The aim of this study was to investigate the role of primary NP size and the agglomeration state in aerosols, using well-characterized TiO₂ NP, on their relative pulmonary toxicity, through inflammatory, cytotoxic and oxidative stress effects in Fisher 344 male rats.

Methods

Three different sizes of TiO₂ NP, i.e., 5, 10–30 or 50 nm, were inhaled as small (SA) (< 100 nm) or large agglomerates (LA) (> 100 nm) at 20 mg/m³ for 6 hours.

Results

Compared to the controls, bronchoalveolar lavage fluids (BALF) showed that LA aerosols induced an acute inflammatory response, characterized by a significant increase in the number of neutrophils, while SA aerosols produced significant oxidative stress damages and cytotoxicity. Data also demonstrate that for an agglomeration state smaller than 100 nm, the 5 nm particles caused a significant increase in cytotoxic effects compared to controls (assessed by an increase in LDH activity), while oxidative damage measured by 8-isoprostane concentration was less when compared to 10–30 and 50 nm particles. In both SA and LA aerosols, the 10–30 nm TiO₂ NP size induced the most pronounced pro-inflammatory effects compared to controls.

Conclusions

Overall, this study showed that initial NP size and agglomeration state are key determinants of nano-TiO₂ lung inflammatory reaction, cytotoxic and oxidative stress induced effects.

Impact through time of different sized titanium dioxide particles on biochemical and histopathological parameters

Due to corrosion, a titanium implant surface can be a potential source for the release of micro (MPs) and nano-sized particles (NPs) into the biological environment. This work sought to evaluate the biokinetics of different sized titanium dioxide particles (TiO2 ) and their potential to cause cell damage. Wistar rats were intraperitoneally injected with 150 nm, 10 nm, or 5nm TiO2 particles. The presence of TiO2 particles was evaluated in histologic sections of the liver, lung, and kidney and in blood cells at 3 and 12 months. Ultrastructural analysis of liver and lung tissue was performed by TEM, deposit concentration in tissues was determined spectroscopically, and oxidative metabolism was assessed by determining oxidative membrane damage, generation of superoxide anion (O2(-)), and enzymatic and non-enzymatic antioxidants. TiO2 particles were observed inside mononuclear blood cells and in organ parenchyma at 3 and 12 months. TiO2 deposits were consistently larger in liver than in lung tissue. Alveolar macrophage O2(-) generation and average particle size correlated negatively (p < 0.05). NPs were more reactive and biopersistent in lung tissue than MPs. Antioxidant activity, particularly in the case of 5 nm particles, failed to compensate for membrane damage in liver cells; the damage was consistent with histological evidence of necrosis.

Effects of polyunsaturated fatty acids on the growth of gastric cancer cells in vitro

Polyunsaturated fatty acids (PUFAs) have tumoricidal action, though the exact mechanism of their action is not clear. The results of the present study showed that of all the fatty acids tested, linoleic acid (LA) and α-linolenic acid (ALA) were the most effective in suppressing the growth of normal gastric cells (GES1) at 180 and 200 μM, while gastric carcinoma cells (MGC and SGC) were inhibited at 200 μM. Arachidonic acid (AA) suppressed the growth of GES1, MGC and SGC cells and lower concentrations (120 and 160 μM) of AA were more effective against gastric carcinoma (MGC and SGC) cells compared to normal gastric cells (GES1). Paradoxically, both eicosapentaenoic (EPA) and docosahexaenoic (DHA) acids though are more unsaturated than AA, were less effective compared with LA, ALA and AA in suppressing the growth of both normal and cancer cells. At the concentration used, methotrexate showed much less growth suppressive action compared to all the fatty acids tested. PUFAs-treated cells showed accumulation of lipid droplets. A close association was noted between apoptosis and lipid peroxides formed compared to the ability of normal and tumor cells to generate ROS (reactive oxygen species) and induce SOD (superoxide dismutase activity) in response to fatty acids tested and methotrexate. Both normal and tumor cells generated lipoxin A₄ (LXA₄) in response to supplementation of fatty acids and methotrexate though no significant correlation was noted between their ability to induce apoptosis and LXA₄ formed. These results suggest that PUFAs induced apoptosis of normal gastric and gastric carcinoma cells could, partly, be attributed to lipid peroxidation process.

Evaluation of the effect of acute and subacute exposure to TiO₂ nanoparticles on oxidative stress

The nanosized titanium dioxide (nano-TiO2) is produced abundantly and used widely in the chemical, electrical/electronic, and energy industries because of its special photovoltaic and photocatalytic activities. Past reports have shown that the nano-TiO2 can enter into the human body through different routes such as inhalation, ingestion, dermal penetration, and injection. The effects of nano-TiO2 on different organs are currently being investigated. Oxidative stress is considered to play an important role in the oxidative potential of nanoparticles. Here we discuss the association between oxidative stress and the toxicity caused by exposure to nano-TiO2 in different organs.

Genotoxicity and carcinogenicity of cobalt-, nickel- and copper-based nanoparticles

The nanotechnology industry has matured and expanded at a rapid pace in the last decade, leading to the research and development of nanomaterials with enormous potential. The largest source of these nanomaterials is the transitional metals. It has been revealed that numerous properties of these nano-sized elements are not present in their bulk states. The nano size of these particles means they are easily transported into biological systems, thus, raising the question of their effects on the susceptible systems. Although advances have been made and insights have been gained on the effect of transitional metals on susceptible biological systems, there still is much ground to be covered, particularly with respect to our knowledge on the genotoxic and carcinogenic effects. Therefore, this review intends to summarize the current knowledge on the genotoxic and carcinogenic potential of cobalt-, nickel- and copper-based nanoparticles indicated in in vitro and in vivo mammalian studies. In the present review, we briefly state the sources, use and exposure routes of these nanoparticles and summarize the current literature findings on their in vivo and in vitro genotoxic and carcinogenic effects. Due to the increasing evidence of their role in carcinogenicity, we have also included studies that have reported epigenetic factors, such as abnormal apoptosis, enhanced oxidative stress and pro-inflammatory effects involving these nanoparticles.

General and electrophysiological toxic effects of manganese in rats following subacute administration in dissolved and nanoparticle form

In an attempt to model occupational and environmental Mn exposures and their possible interaction, young male Wistar rats were exposed to Mn by oral administration in dissolved form (MnCl(2)·4H(2)O, 14.84 and 59.36 mg/kg b.w.) and by intratracheal application of MnO(2) nanoparticles (2.63 mg/kg b.w.). After 3 and 6 weeks oral, or 3 weeks oral plus 3 weeks intratracheal, exposure, general toxicological, and electrophysiological tests were done. Body weight gain was significantly reduced after 6 and 3 plus 3 weeks exposure, but the effect of the latter on the pace of weight gain was stronger. Organ weights signalized systemic stress and effect on lungs. Changes in evoked electrophysiological responses (cortical sensory evoked potential and nerve action potential) indicated that the 3 plus 3 weeks combined exposure caused equal or higher changes in the latency of these responses than 6 weeks of exposure, although the calculated summed Mn dose in the former case was lower. The results showed the importance of the physicochemical form of Mn in determining the toxic outcome, and suggested that neurofunctional markers of Mn action may indicate the human health effect better than conventional blood Mn measurement.

Evaluation of the morphological changes in the lungs of BALB/c mice after inhalation of spherical and rod-shaped titanium nanoparticles

Titanium nanoparticles are widely used by industry in consumer products such as sunscreens and some cosmetic products due to their specifically engineered properties. Some of these properties may, however, increase the toxicity of the nanoparticles which in turn may affect human and environmental health. Therefore, it is of utmost importance to study the possible effects of these particles through in vivo studies, which might produce different results than in vitro cell studies. The current study aimed to investigate the possible remodelling in the lungs of BALB/c mice by means of light and transmission electron microscopy after inhalation of spherical and rod-shaped titanium nanoparticles at two different concentrations. The focus of this paper was to demonstrate whether whole body exposure to different concentrations of the said nanoparticles could induce an inflammatory response in the lungs and no inter particle comparison was done or retention investigated. Animals were divided into five experimental groups: control, high and low concentration groups exposed to the spherical-shaped particles, as well as high and low concentration groups exposed to the rod-shaped particles. Histological and ultrastructural changes, typical of an inflammatory response, were noted in the lungs of the exposed animals. These changes were not observed in the lungs of the control animals. It can be concluded from this study that titanium nanoparticles may cause inflammatory reactions in the lungs of animals exposed through inhalation, as indicated by the presence of inflammatory cells and congestion of inter-alveolar areas. This has implications for individuals who may be potentially exposed during the production and use of titanium nanoparticles.

Feasibility of biomarker studies for engineered nanoparticles: what can be learned from air pollution research

OBJECTIVE

Occupational exposure to engineered nanoparticles (NP) may pose health risks to the workers. This article is to discuss the feasibility of identifying biomarkers that are associated with NP exposure.

METHODS

Scientific literature on the adverse health effects of ambient ultrafine particles (UFP) and NP was reviewed to discuss the feasibility of conducting biomarker studies to identify NP-induced early biological changes.

RESULTS

Various approaches for biomarker studies have been identified, including potential injury pathways that need to be considered and the methodologies that may be used for such studies.

CONCLUSIONS

Although NP may have novel mechanisms of injury, much can be learned from our experience in studying UFP. Oxidative stress-related pathways can be an important consideration for identifying NP-associated biomarkers, and one of the most effective approaches for such studies may be proteome profiling.

CLINICAL SIGNIFICANCE

Biomarker studies will provide valuable information to identify early biological events associated with the adverse health effects of engineered nanomaterials before the manifestation of clinical outcomes. This is particularly important for the health surveillance of workers who may be at higher risk due to their occupational settings.

Analysis of the cytotoxicity of differentially sized titanium dioxide nanoparticles in murine MC3T3-E1 preosteoblasts

There is an increased use of nanophase titanium dioxide (TiO(2)) in bone implants and scaffolds. However, nano-debris is generated at the bone-biomaterial interface. Therefore, TiO(2) nanoparticles (NPs) of many sizes were investigated for cytotoxic effects on murine MC3T3-E1 preosteoblasts. These TiO(2) NPs induced a time- and dose-dependent decrease in cell viability. There was a significant increase in lactate dehydrogenase (LDH) release, apoptosis and mitochondrial membrane permeability following short-term exposure of the cells to TiO(2) NPs. These NPs also increased granulocyte-macrophage colony stimulating factor (GM-CSF) and granulocyte colony-stimulating factor (G-CSF) gene expression. Compared with the 32 nm TiO(2) NPs, 5 nm TiO(2) NPs were more toxic, induced more apoptosis, increased mitochondrial membrane permeability and stimulated more GM-CSF expression at a high concentration (≥100 μg/ml). The results implied that the differential toxicity was associated with variations in size, so more attention should be given to the toxicity of small NPs for the design of future materials for implantation.

Toxicological effects of titanium dioxide nanoparticles: a review of in vitro mammalian studies

BACKGROUND AND OBJECTIVE

Recent rapid advances in nanotechnology raise concerns about development, production route, and diffusion in industrial and consumer products of titanium dioxide nanoparticles (TiO2-NPs). In fact, compared to recent increase in applications of this nanomaterial, the health effects of human exposure have not been systematically investigated. The aim of this review was to provide a comprehensive overview on the current knowledge regarding the effects of TiO2-NPs on mammalian cells.

EVIDENCE AND INFORMATION SOURCES

This review is based on an analysis of the current literature on this topic.

STATE OF THE ART

Fine TiO2 particles have been considered as safe and to pose little risk to humans, suggesting that exposure to this material is relatively harmless. However, available data in the literature showed that TiO2-NPs can cause several adverse effects on mammalian cells such as increase of reactive oxygen species (ROS) production and cytokines levels, reduction of cell viability and proliferation, induction of apoptosis and genotoxicity.

PERSPECTIVES AND CONCLUSIONS

Additional research is needed to obtain up-to-date knowledge on health effects of TiO2-NPs and to avoid any potential risk correlated to their exposure. Consequently, future studies need to: (1) use an homogeneous and rigorous exposure classification to clarify how the physicochemical properties of TiO2-NPs correlate with their toxicological effects; (2) assess the potential adverse effects of low level exposures to TiO2-NPs, as most of the information currently available originates from studies in which exposure levels were excessively and unrealistically high; (3) identify the possible roles of TiO2-NPs in genotoxicity and carcinogenicity (4) carry out epidemiologic studies of exposed workers to provide an assessment of possible risks correlated to the occupational exposure to TiO2-NPs.

Oxidative stress studies of six TiO₂ and two CeO₂ nanomaterials: immuno-spin trapping results with DNA

Six TiO₂ and two CeO₂ nanomaterials with dry sizes ranging from 6-410 nm were tested for their ability to cause DNA centered free radicals in vitro in the concentration range of 10-3,000 ug/ml. All eight of the nanomaterials significantly increased the adduction of the spin trap agent 5,5-dimethyl-1-pyroline N-oxide (DMPO) to DNA as measured by the experimental technique of immuno-spin trapping. The eight nanomaterials differed considerably in their potency, slope, and active concentration. The largest increase in DNA nitrone adducts was caused by a TiO₂ nanomaterial (25 nm, anatase) from Alfa Aesar. Some nanomaterials that increased the amount of DNA nitrone adducts at the lowest exposure concentrations (100 ug/ml) were Degussa TiO₂ (31 nm), Alfa Aesar TiO₂ (25 nm, anatase) and Nanoamor CeO₂ (8 nm, cerianite). At exposure concentrations of 10 or 30 ug/ml, no nanomaterials showed significant in vitro formation of DNA nitrone adducts.