Toxicological aspects of long-term treatment of keratinocytes with ZnO and TiO2 nanoparticles

Sunscreens containing ZnO and TiO(2) nanoparticles (NPs) are increasingly applied to skin over long time periods to reduce the risk of skin cancer. However, long-term toxicological studies of NPs are very sparse. The in vitro toxicity of ZnO and TiO(2) NPs on keratinocytes over short- and long-term applications is reported. The effects studied are intracellular formation of radicals, alterations in cell morphology, mitochondrial activity, and cell-cycle distribution. Cellular response depends on the type of NP, concentration, and exposure time. ZnO NPs have more pronounced adverse effects on keratinocytes than TiO(2). TiO(2) has no effect on cell viability up to 100 μg mL(-1), whereas ZnO reduces viability above 15 μg mL(-1) after short-term exposure. Prolonged exposure to ZnO NPs at 10 μg mL(-1) results in decreased mitochondrial activity, loss of normal cell morphology, and disturbances in cell-cycle distribution. From this point of view TiO(2) has no harmful effect. More nanotubular intercellular structures are observed in keratinocytes exposed to either type of NP than in untreated cells. This observation may indicate cellular transformation from normal to tumor cells due to NP treatment. Transmission electron microscopy images show NPs in vesicles within the cell cytoplasm, particularly in early and late endosomes and amphisomes. Contrary to insoluble TiO(2), partially soluble ZnO stimulates generation of reactive oxygen species to swamp the cell redox defense system thus initiating the death processes, seen also in cell-cycle distribution and fluorescence imaging. Long-term exposure to NPs has adverse effects on human keratinocytes in vitro, which indicates a potential health risk.

[Effect of nano-TiO(2) intratracheal instillation on lipid metabolism of AopE gene-knockout mice]

OBJECTIVE

To investigate the effect of nano-TiO(2) intratracheal instillation on the progression of dyslipidemia and atherosclerosis in apolipoprotein E-knockout mice.

METHODS

The nano-TiO(2) was ultrasound with phosphate-buffered saline solutions (PBS) into its suspension for exposure. A total of 46 specific pathogen free (SPF) level of 11-week-old male apolipoprotein E-knockout mice were randomly divided into groups by their body weights: non-treatment group (8 mice), PBS control group (9 mice), high dose group (1.0 mg/ml, 10 mice), medium dose group (0.5 mg/ml, 10 mice), and low dose group (0.1 mg/ml, 9 mice). Except the non-treatment group, mice from other groups were intratracheally instilled with 0.05 ml each time, twice a week. After exposure of 6 weeks, viscera index, blood TC, TG, HDL-C, LDL-C, and organic lipid ratio were assessed as biomarkers. Artery and aortic root issues were assessed by histopathology.

RESULTS

After 5 weeks exposure, mice body weights in high dose group ((29.7 ± 1.9) g) started to drop, compared to PBS control ((31.3 ± 1.9) g, t = -1.58, P < 0.05) and low dose group ((31.4 ± 1.4) g, t = -1.17, P < 0.05); after 6 weeks, high dose group ((28.8 ± 1.5) g) was lower than PBS control ((30.4 ± 1.9) g, t = -1.60, P < 0.05), non-treatment group ((30.2 ± 1.3) g, t = -1.43, P < 0.05) and low dose group ((30.6 ± 1.0) g, t = -1.83, P < 0.05). TC levels of non-treatment, PBS control, high dose group, medium dose group and low dose group were (2.92 ± 1.18), (3.12 ± 0.73), (4.19 ± 1.86), (3.46 ± 0.72) and (2.57 ± 0.64) mmol/L, respectively; TG levels were (0.39 ± 0.13), (0.39 ± 0.08), (0.60 ± 0.21), (0.55 ± 0.19) and (0.41 ± 0.11) mmol/L, respectively; HDL-C levels were (1.67 ± 0.45), (1.54 ± 0.67), (0.93 ± 0.50), (1.02 ± 0.48) and (1.31 ± 0.64) mmol/L; TG levels of high dose group were higher than that of non-treatment group (t = 1.27, P = 0.03) and low dose group (t = 1.62, P = 0.01); TG levels of medium dose group was higher than PBS control (t = 0.16, P = 0.04), and TC levels of high dose group were higher than PBS control (t = 0.22, P = 0.01), non-treatment group (t = 0.22, P = 0.04) and low dose group (t = 0.20, P = 0.03), and HDL-C levels of high dose group were lower than PBS control (t = -0.61, P = 0.04) and non-treatment group (t = -0.74, P = 0.04); organic lipid ratio of each group were (2.27 ± 0.51)%, (2.06 ± 0.53)%, (2.90 ± 0.50)%, (2.60 ± 0.23)%, (2.24 ± 0.45)%; high dose group were higher than PBS control (t = 0.85, P = 0.00), non-treatment group (t = 0.64, P = 0.03) and low dose group (t = 0.67, P = 0.01); medium dose group was higher than PBS control (t = 0.54, P = 0.02). The plaque lipid content and calcium content which showed the progression of atherosclerosis and plaque rupture were elevated in medium and high dose groups.

CONCLUSION

Intratracheal instillation of nano-TiO(2) can induce dyslipidemia and accelerate the development of atherosclerosis and plaque rupture in ApoE-/-mice.

Nanoparticles: a closer look at their dermal effects

Nano-sized particles represent a unique class of materials with novel physiochemical properties due to increased surface area. Many sunscreens and cosmetics are now using nano-sized titanium dioxide and zinc oxide, which avoids the white, chalky appearance of the older preparations. Although the U.S. Food and Drug Administration (FDA) has determined that nano-sized titanium dioxide is not a new ingredient, but a specific grade of the original product, recent studies suggest that nanomaterials products may not be equivalent to their respective bulk-form products, and the adverse effects of nanoparticles cannot be reliably predicted from the properties of the material in bulk form. Nanoparticles are incorporated into a variety of skin care products, and in the future may be useful as transdermal drug delivery devices. Thus, understanding potential epidermal and dermal penetration, as well as possible toxicity, is important to the field of dermatology. The authors present a review of the therapeutic applications and potential toxicity of nanoparticles relevant to the field of dermatology thus far.

Effect of titanium on lipoprotein lipase activity in vivo and in vitro

SUMMARY

Lipoprotein lipase (LPL) is a major lipolytic enzyme in the intravascular metabolism of postprandial triglyceride-rich lipoproteins. This enzyme is synthesized and secreted by tissues and transported to the capillary endothelial surface. Decreased activity of this enzyme is suggested to be involved in arterial sequestration of lipoproteins and thus in the progression of atherosclerosis. Titanium salts are widely used in industry, medicine, and pharmacy for tablet coating, pharmaceuticals and cosmetic products. In this study the effect of titanium on post-heparin LPL activity is reported in vivo and in vitro.

METHODS

Groups of Male Wistar rats were administered (i.p) with an acute dose of 2.5 mg/kg titanium chloride for 10 days and a chronic dose of 0.75 mg/kg for 30 and/or 60 days. Blood samples were then collected for LPL assay. For in vitro study, plasma aliquots were incubated in the presence of up to 50 mM titanium and the enzyme activity was measured.

RESULTS

Animals exposed to acute dose of titanium showed about 20% reduction in LPL activity, whereas 31% and 36% reductions were observed in animals chronically exposed for 30 and/or 60 days, respectively. Titanium in vitro also led to enzyme inhibition, so that a decrease of 28-53% was seen in the presence of 0.1-50 mM titanium. This inhibition by titanium was potentiated when citrate and/or bicarbonate was present.

CONCLUSION

Although the mechanism of titanium effect on LPL activity in vivo and in vitro demands more investigations, the inhibitory effect of titanium ion in vivo should be considered seriously in subjects exposed to this metal ion. Changes in LPL activity may affect whole body lipid metabolism, a condition favorable for development and progression of atherosclerosis.

One-to-one comparison of sunscreen efficacy, aesthetics and potential nanotoxicity

Numerous reports have described the superior properties of nanoparticles and their diverse range of applications. Issues of toxicity, workplace safety and environmental impact have also been a concern. Here we show a theoretical comparison of how the size of titanium dioxide nanoparticles and their concentration in sunscreens can affect efficacy, aesthetics and potential toxicity from free radical production. The simulation results reveal that, unless very small nanoparticles can be shown to be safe, there is no combination of particle size and concentration that will deliver optimal performance in terms of sun protection and aesthetics. Such a theoretical method complements well the experimental approach for identifying these characteristics.

Effects of titanium dioxide nanoparticle exposure on neuroimmune responses in rat airways

Exposure to ambient nanoparticles (defined as particulate matter [PM] having one dimension <100 nm) is associated with increased risk of childhood and adult asthma. Nanomaterials feature a smaller aerodynamic diameter and a higher surface area per unit mass ratio compared to fine or coarse-sized particles, resulting in greater lung deposition efficiency and an increased potential for biological interaction. The neurotrophins nerve growth factor and brain-derived neurotrophic factor are key regulatory elements of neuronal development and responsiveness of airway sensory neurons. Changes in their expression are associated with bronchoconstriction, airway hyperresponsiveness, and airway inflammation. The neurogenic-mediated control of airway responses is a key pathophysiological mechanism of childhood asthma. However, the effects of nanoparticle exposure on neurotrophin-driven airway responses and their potential role as a predisposing factor for developing asthma have not been clearly elucidated. In this study, in vivo inhalation exposure to titanium dioxide nanoparticles (12 mg/m(3); 5.6 h/d for 3 d) produced upregulation of lung neurotrophins in weanling (2-wk-old) and newborn (2-d-old) rats but not in adult (12-wk-old) animals compared to controls. This effect was associated with increased airway responsiveness and upregulation of growth-related oncogene/keratine-derived chemokine (GRO/KC; CXCL1, rat equivalent of human interleukin [IL]-8) in bronchoalveolar lavage fluid. These data show for the first time that exposure to nanoparticulate upregulates the expression of lung neurotrophins in an age-dependent fashion and that this effect is associated with airway hyperresponsiveness and inflammation. These results suggest the presence of a critical window of vulnerability in earlier stages of lung development, which may lead to a higher risk of developing asthma.

[Toxicological sanitary characterization of titanium dioxide nanoparticles introduced in gastrointestinal tract of rats. Communication 2. Intestinal microbiocenosis condition and allergic sensitivity]

Intestinal microbiocenosis condition, cytokine IL-6, IL-10 and TNF-alpha levels and allergic sensitivity in experimental systemic anaphylaxis test were studied in rats that received intragastrically nanoparticles of titanium dioxide. The results obtained were discussed from the standpoint of possible health risks related to nanodimensional titanium dioxide exposure.

Pulmonary inflammation after intraperitoneal administration of ultrafine titanium dioxide (TiO2) at rest or in lungs primed with lipopolysaccharide

Nanoparticles are widely used in nanomedicines, including for targeted delivery of pharmacological, therapeutic, and diagnostic agents. Since nanoparticles might translocate across cellular barriers from the circulation into targeted organs, it is important to obtain information concerning the pathophysiologic effects of these particles through systemic migration. In the present study, acute pulmonary responses were examined after intraperitoneal (ip) administration of ultrafine titanium dioxide (TiO(2), 40 mg/kg) in mice at rest or in lungs primed with lipopolysaccharide (LPS, ip, 5 mg/kg). Ultrafine TiO(2) exposure increased neutrophil influx, protein levels in bronchoalveolar lavage (BAL) fluid, and reactive oxygen species (ROS) activity of BAL cells 4 h after exposure. Concomitantly, the levels of proinflammatory mediators, such as tumor necrosis factor (TNF)-alpha, interleukin (IL)-1beta, and macrophage inflammatory protein (MIP)-2 in BAL fluid and mRNA expression of TNF-alpha and IL-1beta in lung tissue were elevated post ultrafine TiO(2) exposure. Ultrafine TiO(2) exposure resulted in significant activation of inflammatory signaling molecules, such as c-Src and p38 MAP kinase, in lung tissue and alveolar macrophages, and the nuclear factor (NF)-kappaB pathway in pulmonary tissue. Furthermore, ultrafine TiO(2) additively enhanced these inflammatory parameters and this signaling pathway in lungs primed with lipopolysaccharide (LPS). Contrary to this trend, a synergistic effect was found for TNF-alpha at the level of protein and mRNA expression. These results suggest that ultrafine TiO(2) (P25) induces acute lung inflammation after ip administration, and exhibits additive or synergistic effects with LPS, at least partly, via activation of oxidant-dependent inflammatory signaling and the NF-kappaB pathway, leading to increased production of proinflammatory mediators.

Disturbed mitotic progression and genome segregation are involved in cell transformation mediated by nano-TiO2 long-term exposure

Titanium dioxide (TiO2) nano-particles (<100 nm in diameter) have been of interest in a wide range of applications, such as in cosmetics and pharmaceuticals because of their low toxicity. However, recent studies have shown that TiO2 nano-particles (nano-TiO2) induce cytotoxicity and genotoxicity in various lines of cultured cells as well as tumorigenesis in animal models. The biological roles of nano-TiO2 are shown to be controversial and no comprehensive study paradigm has been developed to investigate their molecular mechanisms. In this study, we showed that short-term exposure to nano-TiO2 enhanced cell proliferation, survival, ERK signaling activation and ROS production in cultured fibroblast cells. Moreover, long-term exposure to nano-TiO2 not only increased cell survival and growth on soft agar but also the numbers of multinucleated cells and micronucleus (MN) as suggested in confocal microscopy analysis. Cell cycle phase analysis showed G2/M delay and slower cell division in long-term exposed cells. Most importantly, long-term TiO2 exposure remarkably affected mitotic progression at anaphase and telophase leading to aberrant multipolar spindles and chromatin alignment/segregation. Moreover, PLK1 was demonstrated as the target for nano-TiO2 in the regulation of mitotic progression and exit. Notably, a higher fraction of sub-G1 phase population appeared in TiO2-exposed cells after releasing from G2/M synchronization. Our results demonstrate that long-term exposure to nano-TiO2 disturbs cell cycle progression and duplicated genome segregation, leading to chromosomal instability and cell transformation.

Dietary exposure to titanium dioxide nanoparticles in rainbow trout, (Oncorhynchus mykiss): no effect on growth, but subtle biochemical disturbances in the brain

Our laboratory recently reported gut pathology following incidental ingestion of titanium dioxide nanoparticles (TiO(2) NPs) during aqueous exposures in trout, but there are almost no data on dietary exposure to TiO(2) NPs in fish. The aim of this experiment was to observe the sub-lethal effects of dietary exposure to TiO(2) NPs in juvenile rainbow trout (Oncorhynchus mykiss). Stock solutions of dispersed TiO(2) NPs were prepared by sonication without the use of solvents and applied to a commercial trout diet. Fish were exposed in triplicate to either, control (no added TiO(2)), 10, or 100 mg kg(-1) TiO(2) NPs diets for 8 weeks followed by a 2 week recovery period where all fish were fed the control diet. TiO(2) NPs had no impact on growth or nutritional performance, and no major disturbances were observed in red or white blood cell counts, haematocrits, whole blood haemoglobin, or plasma Na(+). Ti accumulation occurred in the gill, gut, liver, brain and spleen during dietary TiO(2) exposure. Notably, some of these organs, especially the brain, did not clear Ti after exposure. The brain also showed disturbances to Cu and Zn levels (statistically significant at weeks 4 and 6; ANOVA or Kruskal-Wallis, P < 0.05) and a 50% inhibition of Na(+)K(+)-ATPase activity during TiO(2) NP exposure. Na(+)K(+)-ATPase activity was unaffected in the gills and intestine. Total glutathione in the gills, intestine, liver and brain were not affected by dietary TiO(2) NPs, but thiobarbituric acid reactive substances (TBARS) showed up to 50% decreases in the gill and intestine. We conclude that TiO(2) NPs behave like other toxic dietary metals where growth rate and haematology can be protected during sub-lethal exposures, but in the case of TiO(2) NPs this may be at the expense of critical organs such as the brain and the spleen.

Elicitation of pharmacologically active substances in an intact medical plant

The quality of medical plants used for the production of galenics or pharmacologically useful compounds is usually assessed by the content of biologically active compounds. Because most of these plants are grown in fields, this study focused on stimulation of active compounds by in vivo elicitation. Foliar application of elicitors on the immunostimulating medical plant purple coneflower ( Echinacea purpurea L. Moench.) grown on soil was used to increase the content of biologically active phenolics. Natural plant stress mediators and their derivatives (acetylsalicylic acid, salicylic acid, and methyl salicylate) as well as newly introduced biocompatible metal elicitor [titanium(IV) ascorbate] were chosen as active components of foliar sprays. A tremendous increase of phenolics (up to 10 times compared to control) and stimulation of the biomass yield were achieved. Tuning of organ specificity by modulation of the concentration of elicitor was also observed. This methodology represents a convenient alternative to cell suspension or hydroponic cultures being applicable in wide agricultural practice.

PULMONARY TOXICITY STUDIES IN RATS WITH TRIETHOXYOCTYLSILANE (OTES)-COATED, PIGMENT-GRADE TITANIUM DIOXIDE PARTICLES: BRIDGING STUDIES TO PREDICT INHALATION HAZARD

The aim of this study was to assess and compare the acute lung toxicities of intratracheally instilled hydrophobic relative to hydrophilic surface-coated titanium dioxide (TiO(2)) particles using a pulmonary bridging methodology. In addition, the results of these instillation studies were bridged with data previously generated from inhalation studies with hydrophilic, pigment-grade (base) TiO(2) particles, using the base, pigment-grade TiO(2) particles as the inhalation/instillation bridge material. To conduct toxicity comparisons, the surface coatings of base pigment-grade TiO(2) particles were made hydrophobic by application of triethoxyoctylsilane (OTES), a commercial product used in plastics applications. For the bioassay experimental design, rats were intratracheally instilled with 2 or 10 mg/kg of the following TiO(2) particle-types: (1) base (hydrophilic) TiO(2) particles; (2) TiO(2) with OTES surface coating; (3) base TiO(2) with Tween 80; or (4) OTES TiO(2) with Tween 80. Saline instilled rats served as controls. Following exposures, the lungs of sham- and TiO(2)-exposed rats were assessed both using bronchoalveolar lavage (BAL) biomarkers and by histopathology of lung tissue at 24 hours, 1 week, 1 month, and 3 months post exposure. The results demonstrated that only the base, high-dose (10 mg/kg) pigment-grade TiO(2) particles and those with particle-types containing Tween 80 produced a transient pulmonary inflammatory response, and this was reversible within 1 week postexposure. The authors conclude that the OTES hydrophobic coating on the pigment-grade TiO(2) particle does not cause significant pulmonary toxicity.

[Metabonomic study of plasma after intratracheally instilling titanium dioxide nanoparticles in rats]

OBJECTIVE

1H magnetic resonance (1H MR) spectroscopic technique in combination with pattern recognition technique were applied to analyze toxic effects of rats which were intratracheally instilled with titanium dioxide nanoparticles (nano-TiO2) as well as to detect the target organs and biomarkers associated with the toxic effects.

METHODS

Twenty-four SD male rats were divided into 4 groups randomly which were high dose group (40 mg/kg nano-TiO2), moderate dose group (4 mg/kg nano-TiO2), low dose group (0.4 mg/kg nano-TiO2) and control group (0.9% NaCl solution) respectively, there were six rats per group. All rats were exposed to the object by single intratracheally instilling at a volume of 0.1 ml/100 g. After one week observation, 1H MR spectra of plasma were measured and analyzed by principal component analysis. Histopathologic examination for tissues such as heart, lung, liver, and kidney were performed simultaneously.

RESULTS

The relative content of lactate [(37.86+/-2.58)x10(-3)], citrate [(2.21+/-0.45)x10(-3)], choline [(7.74+/-0.76)x10(-3)] and creatine [(4.17+/-1.15)x10(-3)] in high dose group were significantly decreased as compared with those [(52.07+/-5.12)x10(-3), (3.01+/-0.21)x10(-3), (9.28+/-0.78)x10(-3), (8.59+/-2.64)x10(-3)] in control group (t values were -6.024, -3.177, -3.374, -4.215 respectively, P<0.05), however the relative content of glucose [(19.41+/-1.72)x10(-3)] was significantly increased compared with that [(14.45+/-2.45)x10(-3)] in control group (t value was 2.802, P<0.05). The relative content of lactate [(44.39+/-5.09)x10(-3)] and creatine [(3.67+/-0.76)x10(-3)] in moderate group was significantly decreased compared with those [(52.07+/-5.12)x10(-3), (8.59+/-2.64)x10(-3)] in control group (t values were -3.254, -4.694 respectively, P<0.05). The relative content of pyruvate [(3.84+/-0.70)x10(-3)] was significantly increased in low dose group as compared with that [(3.13+/-0.46)x10(-3)] in control group (t value was 2.787, P<0.05), however the relative content of creatine [(8.10+/-0.72)x10(-3)] was significantly decreased compared with that [(9.28+/-0.78)x10(-3)] in control group (t value was -2.602, P<0.05). No significant difference was found between other experimental groups and control group. No visible damage was found in histopathologic examination.

CONCLUSION

Lung, liver, kidney and heart were the target organs of rats which were intratracheally instilling titanium dioxide nanoparticles. Lactate, pyruvate, glucose, citrate, choline and creatine can be presumed as the biomarkers when searching the target organs of the toxic effects.

[Case of extra-hepatic lymph node metastasis of hepatocellular carcinoma with no evident sign of intra-hepatic recurrence]

A 73-year-old man with chronic hepatitis C was Successfully treated for hepatocellular carcinoma (HCC) by localized treatment. During the follow-up period, abdominal computed tomography (CT) revealed no HCC recurrence in the liver. However, 9 months after the treatment, abdominal lymph nodes appeared enlarged on CT. Laparoscopic biopsy of the lymph nodes showed that the lesion was HCC, and TS-1/cisplatin chemotherapy was performed. However, extra-hepatic lymph nodes rapidly grew, leading to obstructive jaundice and finally death 10 months after of HCC metastasis. Although abdominal lymph node metastasis of HCC has been widely considered to be rare, the confirmation of effective therapy is awaited because histological studies have suggested that this pathologic lesion may occur more often than expected.

[One-stage reconstruction of zygomatico-orbital complex with the use of implants of different origin]

Reconstruction of zygomatico-orbital complex remains as one of the troublesome and topical problems at steady posttraumatic deformations and fresh traumas of the mentioned region. The present work provides analysis of our own experience of surgical treatment of patients suffering from posttraumatic deformations and defects of zygomatico-orbital complex. The work was based on the results of examination and treatment of 33 patients who underwent an operation during the period from 2003 to 2008 years. Of 33, 21 patients were operated due to fresh traumas of the zygomatico-orbital region, and 12 - due to steady posttraumatic deformations of the mentioned region. Of 33 clinical cases, 19 patients underwent reconstruction of zygomatico-orbital complex with the use of implant. In 11 cases implants were perforated titanic plates, in 6 cases - bone cement (Surgical Simplex P), and in 2 cases - combination of titanic plates with bone cement. The results of our investigations have shown that one-stage reconstruction of zygomatico-orbital complex with the use of titanic plates and bone cement liquidates functional and cosmetic disorders. It has been suggested that the use of elaborated complex approaches in treatment of posttraumatic deformations and fresh traumas of zygomatico-orbital region is reasonable and acceptable.

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

As titanium dioxide (TiO(2)) nanoparticles are widely used commercially, the potential effects of TiO(2) nanoparticles on humans are a concern. To evaluate the effects of TiO(2) nanoparticles on hepatic and renal functions and correlate changes to oxidative stress, Sprague-Dawley rats were treated with TiO(2) particles of two different specific surface areas (TiO(2-S50): 50 m(2)/g, and TiO(2-S210): 210 m(2)/g) at 0.5, 5, or 50 mg/kg body weight by intratracheal instillation. After 7 d, TiO(2) nanoparticles produced no obvious acute toxicity on hepatic and renal functions. However, superoxide dismutase (SOD) activity of plasma and glutathione peroxidase (GSH-PX) activity of kidney in the low-dose TiO(2-S210) group were significantly decreased. After TiO(2-S210) exposure, malondialdehyde (MDA) levels of liver and kidney in intermediate and high-dose groups were significantly increased. This change only appeared in liver after TiO(2-S50) exposure. Furthermore, SOD activity in liver and kidney and GSH-PX activity in kidney with low TiO(2-S210) exposure group were significantly less than with low TiO(2-S50). No apparent pathological changes in liver and kidney were observed. Intratracheal exposure to TiO(2) nanoparticles may induce oxidative stress in liver and kidney, but does not influence hepatic or renal functions. There was no apparent evidence that TiO(2-S210) was more toxic than TiO(2-S50). In general, intratracheal exposure to TiO(2) did not markedly affect extrapulmonary tissue functions.

Time-dependent translocation and potential impairment on central nervous system by intranasally instilled TiO(2) nanoparticles

Nanoparticles can be administered via nasal, oral, intraocular, intratracheal (pulmonary toxicity), tail vein and other routes. Here, we focus on the time-dependent translocation and potential damage of TiO(2) nanoparticles on central nervous system (CNS) through intranasal instillation. Size and structural properties are important to assess biological effects of TiO(2) nanoparticles. In present study, female mice were intranasally instilled with two types of well-characterized TiO(2) nanoparticles (i.e. 80 nm, rutile and 155 nm, anatase; purity>99%) every other day. Pure water instilled mice were served as controls. The brain tissues were collected and evaluated for accumulation and distribution of TiO(2), histopathology, oxidative stress, and inflammatory markers at post-instillation time points of 2, 10, 20 and 30 days. The titanium contents in the sub-brain regions including olfactory bulb, cerebral cortex, hippocampus, and cerebellum were determined by inductively coupled plasma mass spectrometry (ICP-MS). Results indicated that the instilled TiO(2) directly entered the brain through olfactory bulb in the whole exposure period, especially deposited in the hippocampus region. After exposure for 30 days, the pathological changes were observed in the hippocampus and olfactory bulb using Nissl staining and transmission electron microscope. The oxidative damage expressed as lipid peroxidation increased significantly, in particular in the exposed group of anatase TiO(2) particles at 30 days postexposure. Exposure to anatase TiO(2) particles also produced higher inflammation responses, in association with the significantly increased tumor necrosis factor alpha (TNF-alpha) and interleukin (IL-1 beta) levels. We conclude that subtle differences in responses to anatase TiO(2) particles versus the rutile ones could be related to crystal structure. Thus, based on these results, rutile ultrafine-TiO(2) particles are expected to have a little lower risk potential for producing adverse effects on central nervous system. Although understanding the mechanisms requires further investigation, the present results suggest that we should pay attention to potential risk of occupational exposure for large-scaled production of TiO(2) nanoparticles.

Matrix metalloproteinase-2 and -9 are induced differently by metal nanoparticles in human monocytes: The role of oxidative stress and protein tyrosine kinase activation

Recently, many studies have shown that nanoparticles can translocate from the lungs to the circulatory system. As a particulate foreign body, nanoparticles could induce host responses such as reactive oxygen species (ROS) generation, inflammatory cytokine and matrix metalloproteinase (MMP) release which play a major role in tissue destruction and remodeling. However, the direct effects of nanoparticles on leukocytes, especially monocytes, are still unclear. The objective of the present study was to compare the ability of Nano-Co and Nano-TiO(2) to cause alteration of transcription and activity of MMPs and to explore possible mechanisms. We hypothesized that non-toxic doses of some transition metal nanoparticles stimulate an imbalance of MMP/TIMP that cause MMP production that may contribute to their health effects. To test this hypothesis, U937 cells were treated with Nano-Co and Nano-TiO(2) and cytotoxic effects and ROS generation were measured. The alteration of MMP-2 and MMP-9 expression and activity of MMP-2 and MMP-9 after exposure to these metal nanoparticles were subsequently determined. To investigate the potential signaling pathways involved in the Nano-Co-induced MMP activation, the ROS scavengers or inhibitors, AP-1 inhibitor, and protein tyrosine kinase (PTK) inhibitors were also used to pre-treat U937 cells. Our results demonstrated that exposure of U937 cells to Nano-Co, but not to Nano-TiO(2), at a dose that does not cause cytotoxicity, resulted in ROS generation and up-regulation of MMP-2 and MMP-9 mRNA expression(..) Our results also showed dose- and time-related increases in pro-MMP-2 and pro-MMP-9 gelatinolytic activities in conditioned media after exposure of U937 cells to Nano-Co, but not to Nano-TiO(2). Nano-Co-induced pro-MMP-2 and pro-MMP-9 activity increases were inhibited by pre-treatment with ROS scavengers or inhibitors. We also demonstrated dose- and time-related decreases in tissue inhibitors of metalloproteinases 2 (TIMP-2) in U937 cells after exposure to Nano-Co, but not to Nano-TiO(2). However, neither Nano-Co nor Nano-TiO(2) exposure led to any transcriptional change of TIMP-1. The decrease of TIMP-2 after exposure to Nano-Co was also inhibited by pre-treatment with ROS scavengers or inhibitors. Our results also showed that pre-treatment of U937 cells with AP-1 inhibitor, curcumin, or the PTK specific inhibitor, herbimycin A or genistein, prior to exposure to Nano-Co, significantly abolished Nano-Co-induced pro-MMP-2 and-9 activity. Our results suggest that Nano-Co causes an imbalance between the expression and activity of MMPs and their inhibitors which is mediated by the AP-1 and tyrosine kinase pathways due to oxidative stress.

Metabolic insertion of nanostructured TiO2 into the patterned biosilica of the diatom Pinnularia sp. by a two-stage bioreactor cultivation process

Diatoms are single-celled algae that make silica shells or frustules with intricate nanoscale features imbedded within periodic two-dimensional pore arrays. A two-stage photobioreactor cultivation process was used to metabolically insert titanium into the patterned biosilica of the diatom Pinnularia sp. In Stage I, diatom cells were grown up on dissolved silicon until silicon starvation was achieved. In Stage II, soluble titanium and silicon were continuously fed to the silicon-starved cell suspension (approximately 4 x 10(5) cells/mL) for 10 h. The feeding rate of titanium (0.85-7.3 micromol Ti L(-1) h(-1)) was designed to circumvent the precipitation of titanate in the liquid medium, and feeding rate of silicon (48 micromol Si L(-1) h(-1)) was designed to sustain one cell division. The addition of titanium to the culture had no detrimental effects on cell growth and preserved the frustule morphology. Cofeeding of Ti and Si was required for complete intracellular uptake of Ti. The maximum bulk composition of titanium in the frustule biosilica was 2.3 g of Ti/100 g of SiO(2). Intact biosilica frustules were isolated by treatment of diatom cells with SDS/EDTA and then analyzed by TEM and STEM-EDS. Titanium was preferentially deposited as a nanophase lining the base of each frustule pore, with estimated local TiO(2) content of nearly 80 wt %. Thermal annealing in air at 720 degrees C converted the biogenic titanate to anatase TiO(2) with an average crystal size of 32 nm. This is the first reported study of using a living organism to controllably fabricate semiconductor TiO(2) nanostructures by a bottom-up self-assembly process.

Carcinogenic Hazards from Inhaled Carbon Black, Titanium Dioxide, and Talc not Containing Asbestos or Asbestiform Fibers: Recent Evaluations by anIARC MonographsWorking Group

In February 2006, an IARC Monographs Working Group reevaluated the carcinogenic hazards to humans of carbon black, titanium dioxide, and talc, which belong to the group of poorly soluble, low-toxicity particles. The review of the relevant literature and the evaluations by the Working Group will be published in Volume 93 of the IARC Monographs series. This article summarizes the Working Group's conclusions. Epidemiological studies among workers in carbon black production and in the rubber industry provided inadequate evidence of carcinogenicity. The overall data from cancer studies in rodents exposed to carbon black provided sufficient evidence of carcinogenicity. The Working Group evaluated carbon black as possibly carcinogenic to humans, Group 2B. Reviewing the epidemiological studies in the titanium dioxide production industry, the Working Group concluded that there is inadequate evidence of carcinogenicity. Overall, the results from rodent cancer studies with titanium dioxide were considered to provide sufficient evidence. Titanium dioxide was evaluated as possibly carcinogenic to humans, Group 2B. Epidemiological studies on talc miners and millers provided inadequate evidence of carcinogenicity of inhaled talc not containing asbestos or asbestiform fibers. The evidence from rodent cancer studies was considered limited. The Working Group evaluated inhaled talc not containing asbestos or asbestiform fibers as not classifiable as to its carcinogenicity to humans, Group 3. The Working Group noted that prolonged exposure to inhaled particles at sufficiently high concentrations in experimental animals may lead to impairment of normal clearance mechanisms in the alveolar region of the lung, resulting in a continued buildup of particles that eventually leads to excessive lung burdens accompanied by chronic alveolar inflammation. The inflammatory response may give rise to increased generation of reactive oxygen species, cell injury, cell proliferation, fibrosis, induction of mutations, and, ultimately, cancer. Since many of these steps also occur in workers in dusty jobs, such as coal miners, data on cancer in animals obtained under conditions of impaired lung clearance were considered relevant to humans. In addition, impaired lung clearance in rodents exposed to ultrafine particles occurs at much lower mass concentrations than with fine particles, which adds to the human relevance.

Chronic Inhalation Toxicity and Carcinogenicity Study on Potassium Octatitanate Fibers (TISMO) in Rats

A chronic inhalation toxicity/carcinogenicity study of potassium octatitanate fibers (TISMO) was conducted in male Fischer 344 rats. Groups of 135 rats were exposed via whole-body inhalation to 0, 20, 60, or 200 WHO fibers/cc of TISMO, 6 h/day, 5 days/w for 24 mo. Six of 30 subgroup rats were killed after 3, 6, 12, 18, and 24 mo of exposure for lung burden evaluations. Another 30 subgroup rats were removed from the exposure chambers after 6 mo of exposure, placed in clean air, and from this group 6 rats were killed at 3, 6, 9, 12, and 18 mo later to study lung clearance. The remaining 75 rats in each group were subjected to 24 mo of exposure for chronic toxicity and carcinogenicity study. Rats exposed to HEPA-filtered air (chamber control) were used as a negative control in each study. The lung burden results indicated that a time point of equilibrium between lung burden and lung clearance at 20 WHO fibers/cc exposure was attained after approximately 18 mo of exposure. There was no difference in the number of WHO fiber from the lungs between 18 and 24 mo at 20 WHO fibers/cc exposure. But disproportional rapid increase in lung burden at 200 WHO fibers/cc exposure appeared to be saturation of lung clearance mechanism resulting from lung overloading. At 200 WHO fibers/cc exposure, approximately 22.9 and 70.5 million WHO fibers were retained in the lung after 3 and 6 mo of exposure, respectively, but lungs revealed normal in appearance. However, alveolar walls enclosing aggregated TISMO-laden alveolar macrophages (AMs) showed fibrotic thickening and approximately 197.3 million WHO fibers were retained in the lungs after 18 mo of exposure. Inhaled fibers were rapidly cleared during 3- and 6-mo recovery periods, and thereafter gradually progressive fiber reduction was observed throughout 18 mo of recovery. The number of WHO fibers decreased by approximately 72%, 74%, and 79% in the 200, 60, and 20 WHO fibers/cc groups, respectively, at the end of the 18-mo recovery period following 6 mo of exposure. Although inhaled TISMO fibers in the 20 WHO fibers/cc exposure group were phagocytized by alveolar macrophages (AMs) the lung morphology appeared normal throughout 24 mo of exposure. At 60 WHO fibers/cc exposure, a slight dose- and time-dependent increase in TISMO-laden AMs was observed throughout 3, 6, and 12 mo of exposure and some alveoli containing aggregated TISMO-laden AMs showed alveolar wall thickening at 18 mo of exposure and minimal alveolar fibrosis at 24 mo of exposure. The exposure concentration is interpreted as a borderline effect level. At 200 WHO fibers/cc exposure, lungs preserved normal architecture at 3 and 6 mo of exposure. Some alveolar walls enclosing aggregates of TISMO-laden AMs were slightly thickened after 12 mo of exposure and revealed slight alveolar fibrosis after 18 and 24 mo of exposure. Neither exposure related-pulmonary neoplasm nor mesothelioma was observed in 24 mo of exposure. The 20 WHO fibers/cc exposure concentration is considered to be a no-observable-adverse-effect level (NOAEL). TISMO exposure limits of 1 WHO fiber/cc would not impose a significant health hazard to humans in the workplace based on the animal experiments and medical surveys on workers.

Bactericidal effect of TiO2 on the selected Vibrio parahaemolyticus and optimization using response surface methodology

In this work, the bactericidal effect of TiO2 on selected typical food pathogenic bacteria, Vibrio parahaemolyticus was studied. V parahaemolyticus is an important pathogen of humans and aqua-cultured animals. We established the response surface methodology (Box-Behnken Design) to investigate the effect of principal parameters on the cell sterilization such as TiO2 concentration, UV illumination time, temperature, and pH. The sterilization rate reached maximum value at the TiO2 concentration of 1.0 mg/ml. During irradiation under the time of 30 min with UV light with the 1g-TiO2/l, the sterilization rate was greater than 85%, and 99% or more cell lost their viability with 3 hours of irradiation. Sterilization rate of the cell increased with decrease in the pH and temperature.

Effects of oxygen content on bioactivity of titanium oxide films fabricated on titanium by electron beam evaporation

The titanium oxide films were fabricated on titanium metal by e-beam deposition technique in various oxygen partial pressures in order to investigate the effects of oxygen content in titanium oxide film on the bioactivity of titanium implant. The nano-sized titanium oxide particles were observed on the surface of specimens. Raman spectra showed that titanium oxide films deposited by e-beam evaporator had oxygen deficient TiO2 structure. The oxygen content in oxide films was calculated from the high resolution XPS spectra of Ti 2p. The densities of HA particles formed on the sample surfaces after immersion test in SBF became higher as the contents of oxygen in titanium oxide films increased. We concluded that the degree of hydroxyl group formation in SBF depended on the stoichiometry of TiO2, which enhanced the bioactivity of titanium.