Induction of sister chromatid exchanges and micronuclei by titanium dioxide in Chinese hamster ovary-K1 cells

Safety assessment of titanium dioxide (E171) as a food additive

The present opinion deals with an updated safety assessment of the food additive titanium dioxide (E 171) based on new relevant scientific evidence considered by the Panel to be reliable, including data obtained with TiO2 nanoparticles (NPs) and data from an extended one-generation reproductive toxicity (EOGRT) study. Less than 50% of constituent particles by number in E 171 have a minimum external dimension < 100 nm. In addition, the Panel noted that constituent particles < 30 nm amounted to less than 1% of particles by number. The Panel therefore considered that studies with TiO2 NPs < 30 nm were of limited relevance to the safety assessment of E 171. The Panel concluded that although gastrointestinal absorption of TiO2 particles is low, they may accumulate in the body. Studies on general and organ toxicity did not indicate adverse effects with either E 171 up to a dose of 1,000 mg/kg body weight (bw) per day or with TiO2 NPs (> 30 nm) up to the highest dose tested of 100 mg/kg bw per day. No effects on reproductive and developmental toxicity were observed up to a dose of 1,000 mg E 171/kg bw per day, the highest dose tested in the EOGRT study. However, observations of potential immunotoxicity and inflammation with E 171 and potential neurotoxicity with TiO2 NPs, together with the potential induction of aberrant crypt foci with E 171, may indicate adverse effects. With respect to genotoxicity, the Panel concluded that TiO2 particles have the potential to induce DNA strand breaks and chromosomal damage, but not gene mutations. No clear correlation was observed between the physico-chemical properties of TiO2 particles and the outcome of either in vitro or in vivo genotoxicity assays. A concern for genotoxicity of TiO2 particles that may be present in E 171 could therefore not be ruled out. Several modes of action for the genotoxicity may operate in parallel and the relative contributions of different molecular mechanisms elicited by TiO2 particles are not known. There was uncertainty as to whether a threshold mode of action could be assumed. In addition, a cut-off value for TiO2 particle size with respect to genotoxicity could not be identified. No appropriately designed study was available to investigate the potential carcinogenic effects of TiO2 NPs. Based on all the evidence available, a concern for genotoxicity could not be ruled out, and given the many uncertainties, the Panel concluded that E 171 can no longer be considered as safe when used as a food additive.

Using a high-throughput method in the micronucleus assay to compare animal-free with rat-derived S9

This study presents a high-throughput (HTP) micronucleus assay in multi-well plates with an automated evaluation for risk assessment applications. The evaluation of genotoxicity via the micronucleus assays according to international guidelines ISO 21427-2 with Chinese hamster (Cricetulus griseus) V79 cells was the starting point to develop our methodology. A drawback of this assay is that it is very time consuming and cost intensive. Our HTP micronucleus assay in a 48-well plate format allows for the simultaneous assessment of five different sample-concentrations with additional positive, negative and solvent controls with six technical replicates each within a quarter of the time required for the equivalent evaluation using the traditional slide method. In accordance with the 3R principle, animal compounds should be replaced with animal-free alternatives. However, traditional cell culture-based methods still require animal derived compounds like rat-liver derived S9-fraction, which is used to simulate the mammalian metabolism in in vitro assays that do show intrinsic metabolization capabilities. In the present study, a recently developed animal-free biotechnological alternative (ewoS9R) was investigated in the new high-throughput micronucleus assay. In total, 12 different mutagenic or genotoxic chemicals were investigated to assess the potential use of the animal-free metabolization system (ewoS9R) in comparison to a common rat-derived product. Out of the 12 compounds, one compound did not induce micronuclei in any treatment and 2 substances showed a genotoxic potential without the need for a metabolization system. EwoS9R demonstrated promising potential for future applications as it shows comparable results to the rat-derived S9 for 6 of the 9 pro-genotoxic substances tested. The remaining 3 substances (2-Acetamidofluorene, Benzo[a]pyrene, Cyclophosphamide) were only metabolized by rat-derived S9. A potential explanation is that ewoS9R was investigated with an approx. 10-fold lower enzyme concentration and was only optimized for CYP1A metabolization that may be improved with a modified production procedure. Future applications of ewoS9R go beyond the micronucleus assay, but further research is necessary.

Genotoxic properties of materials used for endoprostheses: Experimental and human data

Approximately 2 million endoprostheses are implanted annually and metal ions as well as particles are released into the body from the materials which are used. This review describes the results of studies concerning genotoxic damage caused by artificial joints. DNA damage leads to various adverse long-term health effects in humans including cancer. Experiments with mammalian cells showed that metal ions and particles from orthopedic materials cause DNA damage. Induction of chromosomal aberrations (CA) was found in several in vitro experiments and in studies with rodents with metals from orthopedic materials. Human studies focused mainly on induction of CA (7 studies). Only few investigations (4) concerned sister chromatid exchanges, oxidative DNA damage (2) and micronucleus formation (1). CA are a reliable biomarker for increased cancer risks in humans) and were increased in all studies in patients with artificial joints. No firm conclusion can be drawn at present if the effects in humans are due to oxidative stress and if dissolved metal ions or release particles play a role. Our findings indicate that patients with artificial joints may have increased cancer risks due to damage of the genetic material. Future studies should be performed to identify safe materials and to study the molecular mechanisms in detail.

Role of MicroRNAs in regulation of DNA damage in monocytes exposed to polystyrene and TiO2 nanoparticles

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Time and dose dependent DNA damage profile was established to determine the genotoxicity of PSNPs and nano-TiO₂-ARS.

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Expression of DNA damage repairing genes was elevated post nano-TiO₂-ARS, but not post PSNPs exposure.

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miRNA expression screening with different potential activators revealed miR-155-5p as best candidate.

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Transfection of miR-155-5p mimic influenced expression of genes invovled in DNA damage post expousre to TiO₂ and PSNPs.

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miR-155-5p showed the highest potential to be used as biomarker for PSNPs and nano-TiO₂-ARS induced adverse effects.

The release of nanoparticles into the environment can interfere with the health of the exposed organisms. MicroRNAs have been suggested as potential toxicology biomarkers. The expression of potential zebrafish nano-toxicity biomarker miRNAs in our previous study was validated in THP-1 human monocytic cell line after exposure to polystyrene (PSNPs) and ARS labeled Titanium dioxide nanoparticles (nano-TiO₂-ARS). miRNAs expression post exposure to PLGA nanoparticles and E. coli BioParticles was used to exclude potential activation and engagement of miRNAs through phagocytosis or pro-inflammatory specific responses. miR-155-5p showed the highest potential to be used as biomarker for PSNPs and nano-TiO₂-ARS induced toxicity. To determine effects of PSNPs and nano-TiO₂-ARS on genotoxicity, time and dose dependent DNA damage profile was established. Severe DNA damage was triggered by both nanoparticles, and expression of DNA damage repairing genes was elevated post nano-TiO₂-ARS, but not post PSNPs exposure, questioning the utility of the comet assay as universal assessment tool for genotoxicity induced by nanoparticles in general. Transfection of miR-155-5p mimic influenced the expression of miR-155-5p related, DNA damage responsible genes post both nano-TiO₂-ARS and PSNPs exposure. Transfection results suggest significant involvement of miR-155-5p in gene repair mechanisms triggered by adverse effects of PSNPs and nano-TiO₂-ARS on monocytes.

Effect of the Compositions on the Biocompatibility of New Alumina-Zirconia-Titania Dental Ceramic Composites

Dental implant biomaterials are expected to be in contact with living tissues, therefore their toxicity and osseointegration ability must be carefully assessed. In the current study, the wettability, cytotoxicity, and genotoxicity of different alumina-zirconia-titania composites were evaluated. The surface wettability determines the biological event cascade in the bioceramic/human living tissues interface. The measured water contact angle indicated that the wettability strongly depends on the ceramic composition. Notwithstanding the contact angle variability, the ceramic surfaces are hydrophilic. The cytotoxicity of human gingival fibroblast cells with materials, evaluated by an (3-(4,5 methylthiazol-2-yl)-2,5-diphenyl-tetrazolium bromide (MTT) test, revealed an absence of any cytotoxic effect. A relationship was found between the cell viability and the wettability. It was subsequently deduced that the cell viability increases when the wettability increases. This effect is more pronounced when the titania content is higher. Finally, a comet test was applied as complementary biocompatibility test to detect any changes in fibroblast cell DNA. The results showed that the DNA damage is intimately related to the TiO₂ content. Genotoxicity was mainly attributed to ceramic composites containing 10 wt.% TiO₂. Our research revealed that the newly developed high performance alumina-zirconia-titania ceramic composites contain less than 10 wt.% TiO₂, and display promising surface properties, making them suitable for dental implantology applications.

Characterization and Anti-Cancerous Effect of Putranjiva roxburghii Seed Extract Mediated Silver Nanoparticles on Human Colon (HCT-116), Pancreatic (PANC-1) and Breast (MDA-MB 231) Cancer Cell Lines: A Comparative Study

Introduction

A comparative study of Putranjiva roxburghii Wall. seed extract and developed silver nanoparticles (PJSNPs) for improving bioavailability that enhance their anti-cancer activity against HCT-116 (colon carcinoma), PANC-1 (pancreatic carcinoma), MDA-MB 231 (breast carcinoma) cell lines was performed.

Materials and Methods

The green synthesis of PJSNPs (Putranjiva silver nanoparticles) was performed using PJ (Putranjiva) extract, and characterization of synthesized nanoparticles was accomplished through UV-Vis spectrum, X-ray diffraction (XRD), transmission electron microscopy, energy-dispersive X-ray spectroscopy (TEM-EDAX), scanning electron microscopy (SEM), Fourier transform infrared spectroscopy (FTIR), atomic force microscopy (AFM), and Raman spectroscopy.

Results

The results revealed that PJSNPs are homogeneous, spherical in shape, ~8±2 nm in size, and negatively charged with a zeta potential of about -26.71 mV. The cytotoxicity pattern observed was AgNO₃ > PJSNPs > PJ extract. The morphological changes of the cells were observed by flow cytometry and also by the DNA ladder pattern on gel electrophoresis, which indicated that the process of cell death occurred via the apoptosis mechanism and PJSNPs were exerting late-stage apoptosis in all the tested cell lines. The small size and negative value of zeta potential could be the factors responsible for greater bioavailability and thus increased uptake by the tumor cells.

Conclusion

The MTT assay and morphological changes observed by various methods indicate that the novel PJSNPs are a better anticancer agent than PJ extract. All the above properties make biologically synthesized PJSNPs an important target in the field of anti-cancer drug discovery.

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

Titanium dioxide nanoparticles (TiO₂-NPs) are widely used in the cosmetics, health, and food industries, but their safety and genotoxicity remain a matter of debate. We investigated whether TiO₂-NPs could induce gene mutations in mouse lymphoma L5178Y cells and Salmonella typhimurium strains TA97a, TA98, TA100, TA102, and TA1535. Following preliminary tests, 2 mg/mL for the mouse lymphoma gene mutation assay and 1.25 mg/plate for the in vitro bacterial reverse mutation assay (Ames test) were selected as the highest concentrations. Exposure to TiO2-NPs for 4 or 24 h with or without S9 metabolic activation did not increase mutation frequency for any of the concentrations tested in L5178Y cells. In the Ames test, TiO₂-NPs did not induce reverse mutation in the bacterial strains. No positive mutagenic responses were observed in either test system, and therefore we cannot classify TiO₂-NPs as mutagenic; further testing will be required to determine conclusively whether TiO₂-NPs are genotoxic.

Anti-cancerous effect of albumin coated silver nanoparticles on MDA-MB 231 human breast cancer cell line

With the aim of making specific targeting of silver nanoparticles as a drug for tumor cells and developing new anticancer agents, a novel nano-composite was developed. Albumin coated silver nanoparticles (ASNPs) were synthesized, and their anti-cancerous effects were evaluated against MDA-MB 231, a human breast cancer cell line. The synthesized ASNPs were characterized by spectroscopic methods. The morphological changes of the cells were observed by inverted, florescent microscopy and also by DNA ladder pattern on gel electrophoresis; the results revealed that the cell death process occurred through the apoptosis mechanism. It was found that ASNPs with a size of 90 nm and negatively charged with a zeta-potential of about −20 mV could be specifically taken up by tumor cells. The LD₅₀ of ASNPs against MDA-MB 231 (5 μM), was found to be 30 times higher than that for white normal blood cells (152 μM). The characteristics of the synthesized ASNPs included; intact structure of coated albumin, higher cytotoxicity against cancer cells than over normal cells, and cell death based on apoptosis and reduction of gland tumor sizes in mice. This work indicates that ASNPs could be a good candidate for chemotherapeutic drug.

An in vitro blood culture for evaluating the genotoxicity of titanium dioxide: the responses of antioxidant enzymes

Titanium dioxide (TiO2) is extensively used in many industrial areas, including cosmetics, pharmaceutical, paint and paper production. Although the uses of TiO2have become so widespread, there is limited information concerning its toxicity on humans. However, the genotoxicity of TiO2remains to be controversial. The possible genotoxic effects of TiO2have been evaluated in human whole blood cultures (WBCs) related to oxidative status. The blood was processed to examine the following oxidative stress markers: glutathione peroxidase, glutathione reductase, superoxide dismutase and catalase. In addition, the frequencies of sister-chromatid exchanges (SCEs) and micronuclei (MN) were scored as genetic endpoints. Different concentrations of TiO2(1, 2, 3, 5, 7.5 and 10 μM) were tested. From the results, it appeared that TiO2was able to induce genotoxic effects, as observed by the increases found in SCE and MN frequencies in TiO2-treated cultures. Present results also show that treatments with TiO2promoted oxidative stress in human WBC with an increase in concentrations. In conclusion, our data indicate that TiO2can enhance oxidative stress-mediated DNA damage in vitro. Toxicology and Industrial Health 2007; 23: 19—23.

“In Vitro” Comparative Immune Effects of Different Titanium Compounds

Exposure to Ti compounds is today an occupational and environmental health hazard. Object of this study was to determine “in vitro” effects of different Ti salts on cultured human peripheral blood mononuclear cells (PBMC) proliferation and cytokine release. 10−4 and 10−7 M Ti compounds did not modify spontaneous PBMC proliferation. Ti dioxide (a biocompatible material and sunscreen component) did not exert effects on phytoemagglutinin (PHA) stimulated PBMC proliferation and on PHA stimulated IFN-γ and TNF-α release from PBMC. On the other hand, 10−4 M Ti oxalate (with wide industrial applications) and Ti ascorbate (used mainly in agriculture) inhibited about 70 % the PHA stimulated PBMC proliferation; both these Ti compounds at 10−4 and 10−7 M concentrations significantly inhibited TNF-α release, while only Ti oxalate inhibited that of IFN-γ. Titanocene (used in chemotherapy) did not exert effects on PBMC proliferation but markedly inhibited IFN-γ and TNF-α release. On the whole, this study demonstrates that Ti dioxide is not immunotoxic; Ti oxalate shows marked immunotoxicity; titanocene exerts selective toxicity on cytokine release but not on PBMC proliferation, while Ti ascorbate affects TNF-α release from PBMC but not IFN-γ release. In conclusion, these data show that immunotoxicity of Ti depends on speciation.

Genotoxicity of metal oxide nanomaterials: review of recent data and discussion of possible mechanisms

Nanotechnology has rapidly entered into human society, revolutionized many areas, including technology, medicine and cosmetics. This progress is due to the many valuable and unique properties that nanomaterials possess. In turn, these properties might become an issue of concern when considering potentially uncontrolled release to the environment. The rapid development of new nanomaterials thus raises questions about their impact on the environment and human health. This review focuses on the potential of nanomaterials to cause genotoxicity and summarizes recent genotoxicity studies on metal oxide/silica nanomaterials. Though the number of genotoxicity studies on metal oxide/silica nanomaterials is still limited, this endpoint has recently received more attention for nanomaterials, and the number of related publications has increased. An analysis of these peer reviewed publications over nearly two decades shows that the test most employed to evaluate the genotoxicity of these nanomaterials is the comet assay, followed by micronucleus, Ames and chromosome aberration tests. Based on the data studied, we concluded that in the majority of the publications analysed in this review, the metal oxide (or silica) nanoparticles of the same core chemical composition did not show different genotoxicity study calls (i.e. positive or negative) in the same test, although some results are inconsistent and need to be confirmed by additional experiments. Where the results are conflicting, it may be due to the following reasons: (1) variation in size of the nanoparticles; (2) variations in size distribution; (3) various purities of nanomaterials; (4) variation in surface areas for nanomaterials with the same average size; (5) differences in coatings; (6) differences in crystal structures of the same types of nanomaterials; (7) differences in size of aggregates in solution/media; (8) differences in assays; (9) different concentrations of nanomaterials in assay tests. Indeed, due to the observed inconsistencies in the recent literature and the lack of adherence to appropriate, standardized test methods, reliable genotoxicity assessment of nanomaterials is still challenging.

Genotoxicity in primary human peripheral lymphocytes after exposure to lithium titanate nanoparticles in vitro

Lithium titanate (Li2TiO3) nanoparticles (LTT NPs; <100 nm) are widely used in battery technology, porcelain enamels, and ceramic insulating bodies. With the increased applications of LTT NPs, the concerns about their potential human toxicity effects and their environmental impact were also increased. However, toxicity data for LTT NPs relating to human health are very limited. Therefore, the purpose of this study was to evaluate whether LTT NPs are able to induce genetic damage in human peripheral lymphocytes in vitro when taking into consideration that DNA damage plays an important role in carcinogenesis. With this aim, the chromosome aberrations (CA), sister chromatid exchanges (SCE), and micronucleus (MN) assays were used as genotoxicity end points. Human peripheral lymphocytes obtained from five healthy male volunteers were exposed to LTT NPs at final dispersed concentrations ranging from 0 to 1000 μg/mL for 72 h at 37°C. The obtained results indicated that LTT NPs compound did not induce DNA damage in human peripheral lymphocytes as depicted by CA/cell, SCE/cell, and MN/1000 cell values in all concentrations tested. In summary, our results revealed that exposure to LTT NPs is not capable of inducing DNA lesions in human peripheral lymphocytes for the first time.

Health risk assessments of lithium titanate nanoparticles in rat liver cell model for its safe applications in nanopharmacology and nanomedicine

Due to their high chemical stability, lithium titanate (Li2TiO3) nanoparticles (LTT NPs) now are projected to be transferred into different nanotechnology areas like nano pharmacology and nano medicine. With the increased applications of LTT NPs for numerous purposes, the concerns about their potential human toxicity effects and their environmental impact are also increased. However, toxicity data for LTT NPs related to human health are very limited. Therefore we aimed to investigate toxicity potentials of various concentrations (0-1,000 ppm) of LTT NPs (<100 nm) in cultured primary rat hepatocytes. Cell viability was detected by [3-(4,5-dimethyl-thiazol-2-yl) 2,5-diphenyltetrazolium bromide] (MTT) assay and lactate dehydrogenase (LDH) release, while total antioxidant capacity (TAC) and total oxidative stress (TOS) levels were determined to evaluate the oxidative injury. DNA damage was analyzed by scoring liver micronuclei rates and by determining 8-oxo-2-deoxyguanosine (8-OH-dG) levels. The results of MTT and LDH assays showed that higher concentrations of dispersed LTT NPs (500 and 1,000 ppm) decreased cell viability. Also, LTT NPs increased TOS (300, 500 and 1,000 ppm) levels and decreased TAC (300, 500 and 1,000 ppm) levels in cultured hepatocytes. The results of genotoxicity tests revealed that LTT NPs did not cause significant increases of micronucleated hepatocytes and 8-OH-dG as compared to control culture. In conclusion, the obtained results showed for the first time that LTT NPs had dose dependent effects on oxidative damage and cytotoxicity but not genotoxicity in cultured primary rat hepatocytes for the first time.

Cytotoxicity of biologically synthesized silver nanoparticles in MDA-MB-231 human breast cancer cells

Silver nanoparticles (AgNPs) have been used as an antimicrobial and disinfectant agents. However, there is limited information about antitumor potential. Therefore, this study focused on determining cytotoxic effects of AgNPs on MDA-MB-231 breast cancer cells and its mechanism of cell death. Herein, we developed a green method for synthesis of AgNPs using culture supernatant of Bacillus funiculus, and synthesized AgNPs were characterized by various analytical techniques such as UV-visible spectrophotometer, particle size analyzer, and transmission electron microscopy (TEM). The toxicity was evaluated using cell viability, metabolic activity, and oxidative stress. MDA-MB-231 breast cancer cells were treated with various concentrations of AgNPs (5 to 25 μg/mL) for 24 h. We found that AgNPs inhibited the growth in a dose-dependent manner using MTT assay. AgNPs showed dose-dependent cytotoxicity against MDA-MB-231 cells through activation of the lactate dehydrogenase (LDH), caspase-3, reactive oxygen species (ROS) generation, eventually leading to induction of apoptosis which was further confirmed through resulting nuclear fragmentation. The present results showed that AgNPs might be a potential alternative agent for human breast cancer therapy.

Titanium dioxide nanoparticles: a review of current toxicological data

Titanium dioxide (TiO2) nanoparticles (NPs) are manufactured worldwide in large quantities for use in a wide range of applications. TiO2 NPs possess different physicochemical properties compared to their fine particle (FP) analogs, which might alter their bioactivity. Most of the literature cited here has focused on the respiratory system, showing the importance of inhalation as the primary route for TiO2 NP exposure in the workplace. TiO2 NPs may translocate to systemic organs from the lung and gastrointestinal tract (GIT) although the rate of translocation appears low. There have also been studies focusing on other potential routes of human exposure. Oral exposure mainly occurs through food products containing TiO2 NP-additives. Most dermal exposure studies, whether in vivo or in vitro, report that TiO2 NPs do not penetrate the stratum corneum (SC). In the field of nanomedicine, intravenous injection can deliver TiO2 nanoparticulate carriers directly into the human body. Upon intravenous exposure, TiO2 NPs can induce pathological lesions of the liver, spleen, kidneys, and brain. We have also shown here that most of these effects may be due to the use of very high doses of TiO2 NPs. There is also an enormous lack of epidemiological data regarding TiO2 NPs in spite of its increased production and use. However, long-term inhalation studies in rats have reported lung tumors. This review summarizes the current knowledge on the toxicology of TiO2 NPs and points out areas where further information is needed.

Titanium dioxide nanoparticles: a review of current toxicological data

Titanium dioxide (TiO2) nanoparticles (NPs) are manufactured worldwide in large quantities for use in a wide range of applications. TiO2 NPs possess different physicochemical properties compared to their fine particle (FP) analogs, which might alter their bioactivity. Most of the literature cited here has focused on the respiratory system, showing the importance of inhalation as the primary route for TiO2 NP exposure in the workplace. TiO2 NPs may translocate to systemic organs from the lung and gastrointestinal tract (GIT) although the rate of translocation appears low. There have also been studies focusing on other potential routes of human exposure. Oral exposure mainly occurs through food products containing TiO2 NP-additives. Most dermal exposure studies, whether in vivo or in vitro, report that TiO2 NPs do not penetrate the stratum corneum (SC). In the field of nanomedicine, intravenous injection can deliver TiO2 nanoparticulate carriers directly into the human body. Upon intravenous exposure, TiO2 NPs can induce pathological lesions of the liver, spleen, kidneys, and brain. We have also shown here that most of these effects may be due to the use of very high doses of TiO2 NPs. There is also an enormous lack of epidemiological data regarding TiO2 NPs in spite of its increased production and use. However, long-term inhalation studies in rats have reported lung tumors. This review summarizes the current knowledge on the toxicology of TiO2 NPs and points out areas where further information is needed.

In vivo demonstration of enhanced radiotherapy using rare earth doped titania nanoparticles

Radiation therapy is often limited by damage to healthy tissue and associated side-effects; restricting radiation to ineffective doses. Preferential incorporation of materials into tumour tissue can enhance the effect of radiation. Titania has precedent for use in photodynamic therapy (PDT), generating reactive oxygen species (ROS) upon photoexcitation, but is limited by the penetration depth of UV light. Optimization of a nanomaterial for interaction with X-rays could be used for deep tumour treatment. As such, titania nanoparticles were doped with gadolinium to optimize the localized energy absorption from a conventional medical X-ray, and further optimized by the addition of other rare earth (RE) elements. These elements were selected due to their large X-ray photon interaction cross-section, and potential for integration into the titania crystal structure. Specific activation of the nanoparticles by X-ray can result in generation of ROS leading to cell death in a tumour-localized manner. We show here that intratumoural injection of RE doped titania nanoparticles can enhance the efficacy of radiotherapy in vivo.

Titanium dioxide nanoparticles exhibit genotoxicity and impair DNA repair activity in A549 cells

Titanium dioxide nanoparticles (TiO(2)-NPs) are produced in large quantities, raising concerns about their impact for human health. The aim of this study was to deeply characterize TiO(2)-NPs genotoxic potential to lung cells, and to link genotoxicity to physicochemical characteristics, e.g., size, specific surface area, crystalline phase. A549 cells were exposed to a panel of TiO(2)-NPs with diameters ranging from 12 to 140 nm, either anatase or rutile. A set of complementary techniques (comet and micronucleus assays, gamma-H2AX immunostaining, 8-oxoGuanine analysis, H2-DCFDA, glutathione content, antioxidant enzymes activities) allowed us to demonstrate that small and spherical TiO(2)-NPs, both anatase and rutile, induce single-strand breaks and oxidative lesions to DNA, together with a general oxidative stress. Additionally we show that these NPs impair cell ability to repair DNA, by inactivation of both NER and BER pathways. This study thus confirms the genotoxic potential of TiO(2)-NPs, which may preclude their mutagenicity and carcinogenicity.

Nanoscale materials for tackling brain cancer: recent progress and outlook

This article reports on recent progress in the development of advanced nanoscale photoreactive, magnetic and multifunctional materials applicable to brain cancer diagnostics, imaging, and therapy, with an emphasis on the latest contributions and the novelty of the approach, along with the most promising emergent trends.

Assessment of the genetic risks of a metallic alloy used in medical implants

The use of artificial implants provides a palliative or permanent solution for individuals who have lost some bodily function through disease, an accident or natural wear. This functional loss can be compensated for by the use of medical devices produced from special biomaterials. Titanium alloy (Ti-6Al-4V) is a well-established primary metallic biomaterial for orthopedic implants, but the toxicity of the chemical components of this alloy has become an issue of concern. In this work, we used the MTT assay and micronucleus assay to examine the cytotoxicity and genotoxicity, respectively, of an extract obtained from this alloy. The MTT assay indicated that the mitochondrial activity and cell viability of CHO-K1 cells were unaffected by exposure to the extract. However, the micronucleus assay revealed DNA damage and an increase in micronucleus frequency at all of the concentrations tested. These results show that ions released from Ti-6Al-4V alloy can cause DNA and nuclear damage and reinforce the importance of assessing the safety of metallic medical devices constructed from biomaterials.

A core in vitro genotoxicity battery comprising the Ames test plus the in vitro micronucleus test is sufficient to detect rodent carcinogens and in vivo genotoxins

In vitro genotoxicity testing needs to include tests in both bacterial and mammalian cells, and be able to detect gene mutations, chromosomal damage and aneuploidy. This may be achieved by a combination of the Ames test (detects gene mutations) and the in vitro micronucleus test (MNvit), since the latter detects both chromosomal aberrations and aneuploidy. In this paper we therefore present an analysis of an existing database of rodent carcinogens and a new database of in vivo genotoxins in terms of the in vitro genotoxicity tests needed to detect their in vivo activity. Published in vitro data from at least one test system (most were from the Ames test) were available for 557 carcinogens and 405 in vivo genotoxins. Because there are fewer publications on the MNvit than for other mammalian cell tests, and because the concordance between the MNvit and the in vitro chromosomal aberration (CAvit) test is so high for clastogenic activity, positive results in the CAvit test were taken as indicative of a positive result in the MNvit where there were no, or only inadequate data for the latter. Also, because Hprt and Tk loci both detect gene-mutation activity, a positive Hprt test was taken as indicative of a mouse-lymphoma Tk assay (MLA)-positive, where there were no data for the latter. Almost all of the 962 rodent carcinogens and in vivo genotoxins were detected by an in vitro battery comprising Ames+MNvit. An additional 11 carcinogens and six in vivo genotoxins would apparently be detected by the MLA, but many of these had not been tested in the MNvit or CAvit tests. Only four chemicals emerge as potentially being more readily detected in MLA than in Ames+MNvit--benzyl acetate, toluene, morphine and thiabendazole--and none of these are convincing cases to argue for the inclusion of the MLA in addition to Ames+MNvit. Thus, there is no convincing evidence that any genotoxic rodent carcinogens or in vivo genotoxins would remain undetected in an in vitro test battery consisting of Ames+MNvit.

Comparative study of the cytotoxic and genotoxic effects of titanium oxide and aluminium oxide nanoparticles in Chinese hamster ovary (CHO-K1) cells

The aim of this study was to analyze the cytotoxicity and genotoxicity of titanium oxide (TiO(2)) and aluminium oxide (Al(2)O(3)) nanoparticles (NPs) on Chinese hamster ovary (CHO-K1) cells using neutral red (NR), mitochondrial activity (by MTT assay), sister chromatid exchange (SCE), micronucleus (MN) formation, and cell cycle kinetics techniques. Results showed a dose-related cytotoxic effect evidenced after 24h by changes in lysosomal and mitochondrial dehydrogenase activity. Interestingly, transmission electronic microscopy (TEM) showed the formation of perinuclear vesicles in CHO-K1 cells after treatment with both NPs during 24h but no NP was detected in the nuclei. Genotoxic effects were shown by MN frequencies which significantly increased at 0.5 and 1 microg/mL TiO(2) and 0.5-10 microg/mL Al(2)O(3). SCE frequencies were higher for cells treated with 1-5 microg/mL TiO(2). The absence of metaphases evidenced cytotoxicity for higher concentrations of TiO(2). No SCE induction was achieved after treatment with 1-25 microg/mL Al(2)O(3). In conclusion, findings showed cytotoxic and genotoxic effects of TiO(2) and Al(2)O(3) NPs on CHO-K1 cells. Possible causes of controversial reports are discussed further on.

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.

Genotoxic effects of nanosized and fine TiO2

The in-vitro genotoxicity of nanosized TiO(2) rutile and anatase was assessed in comparison with fine TiO(2) rutile in human bronchial epithelial BEAS 2B cells using the single-cell gel electrophoresis (comet) assay and the cytokinesis-block micronucleus test. BEAS 2B cells were exposed to eight doses (1-100 microg/cm(2)) of titanium(IV) oxide nanosized rutile (>95%, <5% amorphous SiO(2) coating; 10 x 40 nm), nanosized anatase (99.7%; <25 nm), or fine rutile (99.9%; <5 microm) for 24, 48, and 72 h. Fine rutile reduced cell viability at lower doses than nanosized anatase, which was more cytotoxic than nanosized rutile. In the comet assay, nanosized anatase and fine rutile induced DNA damage at several doses with all treatment times. Dose-dependent effects were seen after the 48- and 72-h treatments with nanosized anatase and after the 24-, 48- (in one out of two experiments), and 72-h treatments (one experiment) with fine rutile. The lowest doses inducing DNA damage were 1 microg/cm(2) for fine rutile and 10 microg/cm( 2) for nanosized anatase. Nanosized rutile showed a significant induction in DNA damage only at 80 microg/cm(2) in the 24-h treatment and at 80 and 100 microg/ cm(2) in the 72-h treatment (with a dose-dependent effect). Only nanosized anatase could elevate the frequency of micronucleated BEAS 2B cells, producing a significant increase at 10 and 60 microg/cm( 2) after the 72-h treatment (no dose-dependency). At increasing doses of all the particles, MN analysis became difficult due to the presence of TiO(2) on the microscopic slides. In conclusion, our studies in human bronchial epithelial BEAS 2B cells showed that uncoated nanosized anatase TiO(2) and fine rutile TiO(2) are more efficient than SiO( 2)-coated nanosized rutile TiO(2) in inducing DNA damage, whereas only nanosized anatase is able to slightly induce micronuclei.

Anti-proliferative activity of silver nanoparticles

BACKGROUND

Nanoparticles possess exceptional physical and chemical properties which led to rapid commercialisation. Silver nanoparticles (Ag-np) are among the most commercialized nanoparticles due to their antimicrobial potential. Ag-np based cosmetics, therapeutic agents and household products are in wide use, which raised a public concern regarding their safety associated with human and environmental use. No safety regulations are in practice for the use of these nanomaterials. The interactions of nanomaterials with cells, uptake mechanisms, distribution, excretion, toxicological endpoints and mechanism of action remain unanswered.

RESULTS

Normal human lung fibroblasts (IMR-90) and human glioblastoma cells (U251) were exposed to different doses of Ag-nps in vitro. Uptake of Ag-nps occurred mainly through endocytosis (clathrin mediated process and macropinocytosis), accompanied by a time dependent increase in exocytosis rate. The electron micrographs revealed a uniform intracellular distribution of Ag-np both in cytoplasm and nucleus. Ag-np treated cells exhibited chromosome instability and mitotic arrest in human cells. There was efficient recovery from arrest in normal human fibroblasts whereas the cancer cells ceased to proliferate. Toxicity of Ag-np is mediated through intracellular calcium (Ca2+) transients along with significant alterations in cell morphology and spreading and surface ruffling. Down regulation of major actin binding protein, filamin was observed after Ag-np exposure. Ag-np induced stress resulted in the up regulation of metallothionein and heme oxygenase -1 genes.

CONCLUSION

Here, we demonstrate that uptake of Ag-np occurs mainly through clathrin mediated endocytosis and macropinocytosis. Our results suggest that cancer cells are susceptible to damage with lack of recovery from Ag-np-induced stress. Ag-np is found to be acting through intracellular calcium transients and chromosomal aberrations, either directly or through activation of catabolic enzymes. The signalling cascades are believed to play key roles in cytoskeleton deformations and ultimately to inhibit cell proliferation.

A high-performance nanobio photocatalyst for targeted brain cancer therapy

We report pronounced and specific antiglioblastoma cell phototoxicity of 5 nm TiO(2) particles covalently tethered to an antibody via a dihydroxybenzene bivalent linker. The linker application enables absorption of a visible part of the solar spectrum by the nanobio hybrid. The phototoxicity is mediated by reactive oxygen species (ROS) that initiate programmed death of the cancer cell. Synchrotron X-ray fluorescence microscopy (XFM) was applied for direct visualization of the nanobioconjugate distribution through a single brain cancer cell at the submicrometer scale.

Genotoxicity evaluation of locally produced dental porcelain--an in vitro study using the Ames and Comet assays

The aim of this study was to determine the genotoxicity of a locally produced dental porcelain (Universiti Sains Malaysia, Malaysia) using the Ames and Comet assays. In the Ames assay, four genotypic variants of the Salmonella strains (TA98, TA100, TA1537 and TA1535) carrying mutations in several genes were used. The dental porcelain was incubated with these four strains in five different doses both in the presence and absence of metabolic activation (S9) and the result was assessed based on the number of revertant colonies. Concurrently, appropriate positive controls were used so as to validate the test. The average number of revertant colonies per plate treated with locally produced dental porcelain was less than double as compared to that of negative control. In the Comet assay, L929 (CCL-1 ATCC, USA) mouse fibroblast cells were treated with the dental porcelain in three different concentrations along with concurrent negative and positive controls. The tail moment which was used as a measurement of DNA damage was almost equal to that of the negative control, suggesting that the locally produced dental porcelain did not induce any DNA damage. The results indicated that the locally produced dental porcelain is non-genotoxic under the present test conditions.

DNA can sediment TiO2 particles and decrease the uptake potential by mammalian cells

Titanium dioxide (TiO(2)) is an important material used in a broad range of industries. As TiO(2) particles used in industries have recently become smaller as technology develops, problems specific to small size are increasing. One such problem is the difficulty of recovering TiO(2) particles suspended in solution. Particles not recovered during their manufacture would be released in the environment and might be taken up by living organisms, leading to "small-size specific toxicity", which has recently become a concern in numerous industries. To prevent environmental release of small-size TiO(2), separation and complete recovery of the particles are important. In this study, we showed that DNA could be used to separate TiO(2) particles (60-500 nm) from an aqueous solution. Although TiO(2) particles (20 mg/10 ml) were kept in suspension in a standing solution for 72 h, addition of small amounts of DNA (25-100 microg/10 ml) completely sedimented all particles within 4 h. Analysis with transmission electron microscopy suggested that the enhanced sedimentation with DNA was due to the formation of aggregates of TiO(2) particles with DNA. Conveniently, DNA-treated TiO(2) particles had difficulty translocating into human cell lines (keratinocytes and skin fibroblasts), suggesting that "small-size specific toxicity" can be prevented. DNA is a useful tool for separating TiO(2) particles which would prevent "small-size specific toxicity" by allowing quick and complete recovery and suppression of uptake by living organisms.

Photodynamic activity of platinum(IV) chloride surface-modified TiO2 irradiated with visible light

The visible light-induced phototoxicity of titanium dioxide modified with platinum(IV) chloride complexes, [TiO2/PtCl4], was tested. In vitro experiments with the mouse melanoma cells (S-91) have demonstrated phototoxicity of the [TiO2/PtCl4] material. Detection of efficiently generated various reactive oxygen species (.OH, O2. -, H2O2, 1O2) and also reactive chlorine species has proven the photodynamic activity of the tested material, induced by visible light (lambda>455 nm). The cellular death (recognized as a necrosis) is a result of the cell membrane peroxidation.

Genotoxicity of poorly soluble particles

Poorly soluble particles such as TiO2, carbon black, and diesel exhaust particles have been evaluated for their genotoxicity using both in vitro and in vivo assays, since inhalation of these compounds by rats at high concentrations has been found to lead to tumor formation. Two principle modes of genotoxic action can be considered for particles, referred to as primary and secondary genotoxicity. Primary genotoxicity is defined as genetic damage elicited by particles in the absence of pulmonary inflammation, whereas secondary genotoxicity implies a pathway of genetic damage resulting from the oxidative DNA attack by reactive oxygen/nitrogen species (ROS/RNS), generated during particle-elicited inflammation. Conceptually, primary genotoxicity might operate via various mechanisms, such as the actions of ROS (e.g., as generated from reactive particle surfaces), or DNA-adduct formation by reactive metabolites of particle-associated organic compounds (e.g., polycyclic aromatic hydrocarbons). Currently available literature data, however, merely indicate that the tumorigenesis of poorly soluble particles involves a mechanism of secondary genotoxicity. However, further research is urgently required, since (1) causality between pulmonary inflammation and genotoxicity has not yet been established, and (2) effects of inflammation on fundamental DNA damage responses that orchestrate mutagenesis and carcinogenic outcome,that is, cell cycle arrest, DNA repair, proliferation, and apoptosis, are currently poorly understood.

Nano-cerium-element-doped titanium dioxide induces apoptosis of Bel 7402 human hepatoma cells in the presence of visible light

AIM

To investigate the apoptotic effect of photoexcited titanium dioxide (TiO(2)) nanoparticles in the presence of visible light on human hepatoma cell line (Bel 7402) and to study the underlying mechanism.

METHODS

Cerium-element-doped titanium dioxide nanoparticles were prepared by impregnation method. Bel 7402 human hepatoma cells were cultured in RPMI 1640 medium in a humidified incubator with 50 mL/L CO(2) at 37 centigrade. A 15 W fluorescent lamp with continuous wavelength light was used as light source in the photocatalytic test. Fluorescence morphology and agarose gel eletrophoresis pattern were performed to analyze apoptotic cells.

RESULTS

The Ce (IV)-doped TiO(2) nanoparticles displayed their superiority. The adsorption edge shifted to the 400-450 nm region. With visible light illuminated for 10 min, 10 microg/cm(3) Ce (IV)-doped TiO(2) induced micronuclei and significant apoptosis in 4 and 24 h, respectively. Hochest 33258 staining of the fixed cells revealed typical apoptotic structures (apoptotic bodies), agarose gel electrophoresis showed typical DNA ladder pattern in treated cells but not in untreated ones.

CONCLUSION

Ce (IV) doped TiO(2) nanoparticles can induce apoptosis of Bel 7402 human hepatoma cells in the presence of visible light.

An investigation of the photo-clastogenic potential of ultrafine titanium dioxide particles

Ultrafine titanium dioxide is widely used in a number of commercial products including sunscreens and cosmetics. There is extensive evidence on the safety of ultrafine titanium dioxide. However, there are some published studies indicating that some forms at least may be photogenotoxic, photocatalytic and/or carcinogenic. In order to clarify the conflicting opinions on the safety of ultrafine titanium dioxide particles, the current studies were performed to investigate the photo-clastogenic potential of eight different classes of ultrafine titanium dioxide particles. The photo-clastogenicity of titanium dioxide was measured in Chinese hamster ovary (CHO) cells in the absence and presence of UV light at a dose of 750 mJ/cm(2). The treatments were short (3 h) followed by a 17-h recovery and achieved concentrations that either induced approximately 50% cytotoxicity or reached 5000 microg/ml if non-cytotoxic. None of the titanium dioxide particles tested induced any increase in chromosomal aberration frequencies either in the absence or presence of UV. These studies show that ultrafine titanium dioxide particles do not exhibit photochemical genotoxicity in the model system used.

Cyto- and genotoxicity of ultrafine TiO2 particles in cultured human lymphoblastoid cells

Titanium dioxide is frequently used in the production of paints, paper, plastics, welding rod-coating material, and cosmetics, because of its low toxicity. However, recent studies have shown that nano-sized or ultrafine TiO(2) (UF-TiO(2)) (<100 nm in diameter) can generate pulmonary fibrosis and lung tumor in rats. Cytotoxicity induced by UF-TiO(2) in rat lung alveolar macrophages was also observed. This generates great concern about the possible adverse effects of UF-TiO(2) for humans. The cytotoxicity and genotoxicity of UF-TiO(2) were investigated using the methyl tetrazolium cytotoxicity (MTT) assay, the population growth assay, the apoptosis assay by flow cytometry, the cytokinesis block micronucleus (CBMN) assay, the comet assay, and the hypoxanthine-guanine phosphoribosyltransferase (HPRT) gene mutation assay. WIL2-NS cells were incubated for 6, 24 and 48 h with 0, 26, 65 and 130 microg/ml UF-TiO(2). Significant decreases in viability were seen in the MTT assay at higher doses; for example, 61, 7 and 2% relative viability at 130 microg/ml for 6, 24 and 48-h exposure (P<0.01). A dose-dependent relationship was observed, while a time-dependent relationship was seen only at the highest dose (130 microg/ml) after exposure for 24 and 48 h. Treatment with 130 microg/ml UF-TiO(2) induced approximately 2.5-fold increases in the frequency of micronucleated binucleated cells (P<0.01). In addition, a significant reduction in the cytokinesis block proliferation index was observed by the CBMN assay (P<0.05). In the comet assay, treatment with 65 microg/ml UF-TiO(2) induced approximately 5-fold increases in olive tail moment (P<0.05). In the HPRT mutation assay, treatment with 130 microg/ml UF-TiO(2) induced approximately 2.5-fold increases in the mutation frequency (P<0.05). The results of this study indicate that UF-TiO(2) can cause genotoxicity and cytotoxicity in cultured human cells.