Shape-engineered titanium dioxide nanoparticles (TiO2-NPs): cytotoxicity and genotoxicity in bronchial epithelial cells

Updated assessment of the genotoxic potential of titanium dioxide based on reviews of in vitro comet, mode of action and cellular uptake studies, and recent publications

In 2021 the European Food Safety Authority (EFSA) concluded that "A concern for genotoxicity of TiO2 particles that may be present in E 171 could therefore not be ruled out.". A detailed review of the genotoxicity of titanium dioxide (TiO2) was subsequently published by Kirkland et al. (2022) using a comprehensive weight of evidence (WoE) approach in which test systems and endpoints were allocated different levels of relevance. At that time only 34 publications met the reliability and quality criteria for being most relevant in the evaluation of genotoxicity, and based on these it was concluded that the existing evidence did not support a direct DNA damaging mechanism for TiO2. Recently a number of regulatory opinions have been published, in which papers were cited that described in vitro DNA damage (mainly comet), mode of action, and cellular uptake studies that were not discussed in Kirkland et al. (2022). Furthermore, a number of additional papers have been published recently or have been identified from the regulatory opinions as a result of using extended search criteria. A total of 70 publications not previously reviewed in Kirkland et al. (2022) have been reviewed here, and again show that the published data on the genotoxicity of TiO2 are inconsistent, often of poor quality, and in some cases difficult to interpret. The cellular uptake studies show some evidence of cytoplasmic uptake, particularly in cells treated in vitro, but there is no convincing evidence of nuclear uptake. In terms of genotoxicity, the conclusions of Kirkland et al. (2022) that existing evidence does not support a direct DNA damaging mechanism for titanium dioxide (including nano forms), and that the main mechanism leading to TiO2 genotoxicity is most likely indirect damage to DNA through generation of reactive oxygen species (ROS), are still valid.

Bioconjugation of Serratiopeptidase with Titanium Oxide Nanoparticles: Improving Stability and Antibacterial Properties

Antimicrobial resistance (AMR) poses a significant global health threat, necessitating the development of novel antibacterial strategies. Serratiopeptidase (SP), a metalloprotease produced by bacteria such as Serratia marcescens, has gained attention not only for its anti-inflammatory properties but also for its potential antibacterial activity. However, its protein nature makes it susceptible to pH changes and self-proteolysis, limiting its effectiveness. This study aimed to increase both the enzymatic stability and antibacterial activity of serratiopeptidase through immobilization on titanium oxide nanoparticles (TiO2-NPs), leveraging the biocompatibility and stability of these nanomaterials. Commercial TiO2-NPs were characterized using TGA/DTG, FT-IR, UV-Vis, and XRD analyses, and their biocompatibility was assessed through cytotoxicity studies. Serratiopeptidase was produced via fermentation using the C8 isolate of Serratia marcescens obtained from the intestine of Bombyx mori L., purified chromatographically, and immobilized on carboxylated nanoparticles via EDC/NHS coupling at various pH conditions. The optimal enzymatic activity was achieved by using pH 5.1 for nanoparticle activation and pH 5.5 for enzyme coupling. The resulting bioconjugate demonstrated stable proteolytic activity at 25 °C for 48 h. Immobilization was confirmed by FT-IR spectroscopy, and the Michaelis-Menten kinetics were determined. Notably, the bioconjugate exhibited two-fold greater antibacterial activity against E. coli than the free enzyme or TiO2-NPs at 1000 µg/mL. This study successfully developed a serratiopeptidase-TiO2 bioconjugate with enhanced enzymatic stability and antibacterial properties. The improved antibacterial activity of the immobilized enzyme presents a promising approach for developing new tools to combat antimicrobial resistance, with potential applications in healthcare, food safety, and environmental protection.

Assessment of possible biomedical applications of green synthesized TiO2NPs-an in-vitro approach

Biomedical applications for various types of nanoparticles are emerging on a daily basis. Hence this research was performed to evaluate the antifungal (Aspergillus sp., Alternaria sp., Trichophyton sp., Candida sp., and Penicillium sp.), cytotoxicity (MCF10A cell lines), and antioxidant (DPPH) potential of Coleus aromaticus mediated and pre-characterized TiO2NPs were studied with respective standard methodology. Interestingly, the TiO2NPs exhibited significant antifungal activity on pathogenic fungal strains like Alternaria sp., Aspergillus sp. (31 ± 1.4), Penicillium sp. (31 ± 1.9) Trichophyton sp. (27 ± 2.1), and Candida sp. (26 ± 2.3) at high concentration (250 μg mL-1). However, the considerable levels of zone of inhibitions on fungal pathogens were recorded at 100 μg mL-1 of TiO2NPs as well as it was considerably greater than positive control. It also demonstrated dose based anti-inflammatory and antidiabetic activities. The plant-mediated TiO2NPs demonstrated a maximum DPPH scavenging efficiency of 91% at a dosage of 250 μg mL-1, comparable to the positive control's 94%. Furthermore, TiO2NPs at 100 μg mL-1 concentration did not cause cytotoxicity in MCF10A cell lines. At higher concentrations (250 μg mL-1), the nanoparticles showed the lowest cytotoxicity (17%). These findings suggest that C. aromaticus-mediated TiO2NPs have significant biomedical applications. However, in-vivo studies are needed to learn more about their (C. aromaticus-mediated TiO2NPs) potential biomedical applications.

Ti-containing NPs in raw water and their removal with conventional treatments in four water treatment plants in Taiwan

The ingestion of Ti-containing nanoparticles from drinking water has emerged as a concern in recent years. This study therefore aimed to characterize Ti-containing nanoparticles in water samples collected from four water treatment plants in Taiwan and to explore the challenges associated with measuring them at low levels using single particle-inductively coupled plasma mass spectrometry. Additionally, the study sought to identify the most effective processes for the removal of Ti-containing nanoparticles. For each water treatment plant, two water samples were collected from raw water, sedimentation effluent, filtration effluent, and finished water, respectively. Results revealed that Ti-containing nanoparticles in raw water, with levels at 8.69 μg/L and 296.8 × 103 particles/L, were removed by approximately 35% and 98%, respectively, in terms of mass concentration and particle number concentration, primarily through flocculation and sedimentation processes. The largest most frequent nanoparticle size in raw water (112.0 ± 2.8 nm) was effectively reduced to 62.0 ± 0.7 nm in finished water, while nanoparticles in the size range of 50-70 nm showed limited changes. Anthracite was identified as a necessary component in the filter beds to further improve removal efficiency at the filtration unit. Moreover, the most frequent sizes of Ti-containing nanoparticles were found to be influenced by salinity. Insights into the challenges associated with measuring low-level Ti-containing nanoparticles in aqueous samples provide valuable information for future research and management of water treatment processes, thereby safeguarding human health.

Genotoxicity evaluation of food additive titanium dioxide using a battery of standard in vivo tests

The increasing use of titanium dioxide (TiO2) nanoparticles (NPs) has raised concern about the safety of food additive TiO2. TiO2 has been considered no longer safe by EFSA due to concerns over genotoxicity, however, there are conflicting opinions upon the safety of TiO2 as a food additive, and the number of in vivo genotoxicity studies conducted on food additive TiO2 was limited. In order to investigate the potential genotoxicity of food additive TiO2, we evaluated the genotoxicity of a commercial food additive TiO2 (average size of 135.54 ± 41.01 nm, range from 60.83 to 230.16 nm, NPs account for 30% by number) using a battery of standard in vivo tests, including mammalian erythrocyte micronucleus test, mammalian bone marrow chromosomal aberration test and in vivo mammalian alkaline comet test. After 15 days of consecutive intragastric administration at doses of 250, 500, and 1000 mg/kgBW, food additive TiO2 neither increased the frequencies of bone marrow micronuclei or chromosomal aberration in mice, nor induced DNA strand breakage in rat liver cells. These results indicate that under the condition of this study, food additive TiO2 does not have genotoxic potential although it contains a fraction of NPs.

Evaluation of possible cytotoxic, genotoxic and epigenotoxic effects of titanium dioxide nanoparticles and possible protective effect of melatonin

Nanoparticles (NPs) are particles of matter that are between 1 to 100 nm in diameter. They are suggested to cause toxic effects in both humans and environment thorough different mechanisms. However, their toxicity profile may be different from the parent material. Titanium dioxide (TiO2) NPs are widely used in cosmetic, pharmaceutical and food industries. As a white pigment, the use of TiO2 is used in food coloring, industrial paints, clothing and UV filters has increased tremendously in recent years. Melatonin, on the other hand, is a well-known antioxidant and may prevent oxidative stress caused by a variety of different substances, including NPs. In the current study, we aimed to comparatively investigate the effects of normal-sized TiO2 (220 nm) and nano-sized TiO2 (21 nm) on cytopathology, cytotoxicity, oxidative damage (lipid peroxidation, protein oxidation and glutathione), genotoxicity (8-hydroxydeoxyguanosine), apoptosis (caspase 3, 8 and 9) and epigenetic alterations (global DNA methylation, H3 acetylation) on 3T3 fibroblast cells. In addition, the possible protective effects of melatonin, which is known to have strong antioxidant effects, against the toxicity of TiO2 were also evaluated. Study groups were: a. the control group; b. melatonin group; c. TiO2 group; d. nano-sized TiO2 group; e. TiO2 + melatonin group and f. nano-sized TiO2 + melatonin group. We observed that both normal-sized and nano-sized TiO2 NPs showed significant toxic effects. However, TiO2 NPs caused higher DNA damage and global DNA methylation compared to normal-sized TiO2 whereas normal-sized TiO2 led to lower H3 acetylation vs. TiO2 NPs. Melatonin showed partial protective effect against the toxicity caused by TiO2 NPs.

DNA damage in workers exposed to pigment grade titanium dioxide (TiO2) and association with biomarkers of oxidative stress and inflammation

The present study was aimed at investigating DNA damage, micronuclei frequency and meta-nuclear alterations in buccal cells of workers involved in pigment-grade TiO2 production (15 exposed and 20 not-exposed). We also assessed associations of genotoxicity biomarkers with oxidative stress/inflammatory biomarkers in urine and exhaled breath condensate (EBC), as well as possible associations between biomarkers and reported respiratory symptoms. In spite of compliance with TiO2 Occupational Exposure Limits, results showed increased direct/oxidative DNA damage and micronuclei frequency in exposed workers. Genotoxicity parameters were associated with oxidative stress/inflammation biomarkers in urine and EBC, thus confirming that TiO2 exposure can affect the oxidative balance. Workers with higher genotoxic/oxidative stress biomarkers levels reported early respiratory symptoms suggesting that molecular alterations can be predictive of early health dysfunctions. These findings suggest the need to assess early health impairment in health surveillance programs and to address properly safety issues in workplaces where TiO2 is handled.

Biocompatibility Evaluation of TiO2, Fe3O4, and TiO2/Fe3O4 Nanomaterials: Insights into Potential Toxic Effects in Erythrocytes and HepG2 Cells

Nanomaterials such as titanium dioxide and magnetite are increasingly used in several fields, such as water remediation and agriculture. However, this has raised environmental concerns due to potential exposure to organisms like humans. Nanomaterials can cause adverse interactions depending on physicochemical characteristics, like size, morphology, and composition, when interacting with living beings. To ensure safe use and prevent the risk of exposure to nanomaterials, their biocompatibility must be assessed. In vitro cell cultures are beneficial for assessing nanomaterial-cell interactions due to their easy handling. The present study evaluated the biocompatibility of TiO2, Fe3O4, and TiO2/Fe3O4 nanomaterials thermally treated at 350 °C and 450 °C in erythrocytes and HepG2 cells. According to the hemolysis experiments, non-thermally treated NMs are toxic (>5% hemolysis), but their thermally treated counterparts do not present toxicity (<2%). This behavior indicates that the toxicity derives from some precursor (solvent or surfactant) used in the synthesis of the nanomaterials. All the thermally treated nanomaterials did not show hemolytic activity under different conditions, such as low-light exposure or the absence of blood plasma proteins. In contrast, non-thermally treated nanomaterials showed a high hemolytic behavior, which was reduced after the purification (washing and thermal treatment) of nanomaterials, indicating the presence of surfactant residue used during synthesis. An MTS cell viability assay shows that calcined nanomaterials do not reduce cell viability (>11%) during 24 h of exposure. On the other hand, a lactate dehydrogenase leakage assay resulted in a higher variability, indicating that several nanomaterials did not cause an increase in cell death as compared to the control. However, a holotomographic microscopy analysis reveals a high accumulation of nanomaterials in the cell structure at a low concentration (10 µg mL-1), altering cell morphology, which could lead to cell membrane damage and cell viability reduction.

Evaluation of the cytotoxic effect of titanium dioxide nanoparticles in human embryonic lung cells

Background/aim

Titanium dioxide nanoparticles are widely used in a variety of products, including sunscreens, paints, and ceramics. However, their increasing use has raised concerns about their potential health risks. Titanium dioxide nanoparticles have been shown to have the ability to enter the bloodstream and accumulate in various tissues, reaching the fetus via the placenta. The aim of this study was to investigate the cytotoxic effects of titanium dioxide nanoparticles on a human embryonic lung cell line (HEL 299/An1) and the formation of oxidative DNA damage.

Materials and methods

The cytotoxic effects of brookite-based titanium dioxide nanoparticles (<100 nm) were assessed using the 3-(4,5-dimethyldiazol-2-yl)-2,5 diphenyl tetrazolium bromide (MTT) assay for 24 and 48 h. Cell titanium levels were determined using inductively coupled plasma mass spectrometry. Oxidative DNA damage was assessed by measuring the levels of 8-hydroxy-2-deoxyguanosine (8-OHdG) as a biomarker.

Results

Titanium dioxide nanoparticles caused dose-dependent cytotoxicity in HEL 299/An1 cells. The IC50 values were 25.93 μM and 0.054 μM after 24 h and 48 h of exposure, respectively. Cell titanium levels were found to be 25,967 ppb after 24 h and 210,353 ppb after 48 h (p < 0.01). 8-OHdG was detected at 32.96 ng/mL after 24 h of exposure and 17.89 ng/mL after 48 h of exposure.

Conclusion

In our study, it was shown that titanium nanoparticles caused dose-dependent cytotoxicity and oxidative DNA damage in human embryonic lung cells. The nanoparticles also accumulated in cells and were taken up in higher amounts after 48 h of exposure. These findings suggest that titanium dioxide nanoparticles may pose a health risk, especially for pregnant women who may not be aware of their pregnancy. Therefore, it is important to take preventive measures to reduce exposure to these nanoparticles.

In Vitro Safety Assessment of In-House Synthesized Titanium Dioxide Nanoparticles: Impact of Washing and Temperature Conditions

Titanium dioxide nanoparticles (TiO2 NPs) have been widely used in food, cosmetics, and biomedical research. However, human safety following exposure to TiO2 NPs remains to be fully understood. The aim of this study was to evaluate the in vitro safety and toxicity of TiO2 NPs synthesized via the Stöber method under different washing and temperature conditions. TiO2 NPs were characterized by their size, shape, surface charge, surface area, crystalline pattern, and band gap. Biological studies were conducted on phagocytic (RAW 264.7) and non-phagocytic (HEK-239) cells. Results showed that washing amorphous as-prepared TiO2 NPs (T1) with ethanol while applying heat at 550 °C (T2) resulted in a reduction in the surface area and charge compared to washing with water (T3) or a higher temperature (800 °C) (T4) and influenced the formation of crystalline structures with the anatase phase in T2 and T3 and rutile/anatase mixture in T4. Biological and toxicological responses varied among TiO2 NPs. T1 was associated with significant cellular internalization and toxicity in both cell types compared to other TiO2 NPs. Furthermore, the formation of the crystalline structure induced toxicity independent of other physicochemical properties. Compared with anatase, the rutile phase (T4) reduced cellular internalization and toxicity. However, comparable levels of reactive oxygen species were generated following exposure to the different types of TiO2, indicating that toxicity is partially driven via non-oxidative pathways. TiO2 NPs were able to trigger an inflammatory response, with varying trends among the two tested cell types. Together, the findings emphasize the importance of standardizing engineered nanomaterial synthesis conditions and evaluating the associated biological and toxicological consequences arising from changes in synthesis conditions.

TiO2-MWCNT nanohybrid: Cytotoxicity, protein corona formation and cellular internalisation in RTG-2 fish cell line

Titanium dioxide nanoparticles-multiwalled carbon nanotubes (TiO_2-MWCNT) nanohydrid has an enhanced photocatalytic activity across the visible light with promising applications in environmental remediation, solar energy devices and antimicrobial technologies. However, it is necessary to evaluate the toxicological effects of TiO_2-MWCNT towards safe and sustainable development of nanohybrids. In this work, we studied the cytotoxicity, protein corona formation and cellular internalisation of TiO_2-MWCNT on fibroblasts derived from gonadal rainbow trout tissue (RTG-2) for the first time. This nanohydrid did not show any toxicity effect on RTG-2 cells up to 100 mg L^-1 after 24 h of exposure as monitored by alamar blue, neutral red and trypan blue assays (in presence or absence of foetal bovine serum, FBS). Futhermore, cryo-transmission electron microscopy analysis demonstrated that TiO₂ particles is attached on nanotube surface after FBS-protein corona formation in cell culture medium. Raman spectroscopy imaging showed that TiO_2-MWCNT can be internalised by RTG-2 cells. This work is a novel contribution towards better understanding the nanobiointeractions of nanohydrids linked to their in vitro effects on fish cells in aquatic nanoecotoxicology.

A Nanomedicine Structure-Activity Framework for Research, Development, and Regulation of Future Cancer Therapies

Despite their clinical success in drug delivery applications, the potential of theranostic nanomedicines is hampered by mechanistic uncertainty and a lack of science-informed regulatory guidance. Both the therapeutic efficacy and the toxicity of nanoformulations are tightly controlled by the complex interplay of the nanoparticle's physicochemical properties and the individual patient/tumor biology; however, it can be difficult to correlate such information with observed outcomes. Additionally, as nanomedicine research attempts to gradually move away from large-scale animal testing, the need for computer-assisted solutions for evaluation will increase. Such models will depend on a clear understanding of structure-activity relationships. This review provides a comprehensive overview of the field of cancer nanomedicine and provides a knowledge framework and foundational interaction maps that can facilitate future research, assessments, and regulation. By forming three complementary maps profiling nanobio interactions and pathways at different levels of biological complexity, a clear picture of a nanoparticle's journey through the body and the therapeutic and adverse consequences of each potential interaction are presented.

Lack of mutagenicity of TiO2 nanoparticles in vitro despite cellular and nuclear uptake

The potential genotoxicity of titanium dioxide (TiO₂) nanoparticles (NPs) is a conflictive topic because both positive and negative findings have been reported. To add clarity, we have carried out a study with two cell lines (V79-4 and A549) to evaluate the effects of TiO₂ NPs (NM-101), with a diameter ranging from 15 to 60 nm, at concentrations 1-75 μg/cm². Using two different dispersion procedures, cell uptake was determined by Transmission Electron Microscopy (TEM). Mutagenicity was evaluated using the Hprt gene mutation test, while genotoxicity was determined with the comet assay, detecting both DNA breaks and oxidized DNA bases (with formamidopyrimidine glycosylase - Fpg). Cell internalization, as determined by TEM, shows TiO₂ NM-101 in cytoplasmic vesicles, as well as close to and inside the nucleus. Such internalization did not depend on the state of agglomeration, nor the dispersion used. In spite of such internalization, no cytotoxicity was detected in V79-4 cells (relative growth activity and plating efficiency assays) or in A549 cells (AlamarBlue assay) after exposure lasting for 24 h. However, a significant decrease in the relative growth activity was detected at longer exposure times (48 and 72 h) and at the highest concentration 75 µg/cm². When the modified enzyme-linked alkaline comet assay was performed on A549 cells, although no significant induction of DNA damage was detected, a positive concentration-effects relationship was observed (Spearman's correlation = 0.9, p 0.0001). Furthermore, no significant increase of DNA oxidized purine bases was observed. When the frequency of Hprt gene mutants was determined in V79-4 cells, no increase was observed in the exposed cells, relative to the unexposed cultures. Our general conclusion is that, under our experimental conditions, TiO₂ NM-101 exposure does not exert mutagenic effects despite the evidence of NP uptake by V79-4 cells.

Evaluating the Use of TiO2 Nanoparticles for Toxicity Testing in Pulmonary A549 Cells

Purpose

Titanium dioxide nanoparticles, 25 nm in size of crystallites (TiO₂ P25), are among the most produced nanomaterials worldwide. The broad use of TiO₂ P25 in material science has implied a request to evaluate their biological effects, especially in the lungs. Hence, the pulmonary A549 cell line has been used to estimate the effects of TiO₂ P25. However, the reports have provided dissimilar results on caused toxicity. Surprisingly, the physicochemical factors influencing TiO₂ P25 action in biological models have not been evaluated in most reports. Thus, the objective of the present study is to characterize the preparation of TiO₂ P25 for biological testing in A549 cells and to evaluate their biological effects.

Methods

We determined the size and crystallinity of TiO₂ P25. We used four techniques for TiO₂ P25 dispersion. We estimated the colloid stability of TiO₂ P25 in distilled water, isotonic NaCl solution, and cell culture medium. We applied the optimal dispersion conditions for testing the biological effects of TiO₂ P25 (0–100 µg.mL⁻¹) in A549 cells using biochemical assays (dehydrogenase activity, glutathione levels) and microscopy.

Results

We found that the use of fetal bovine serum in culture medium is essential to maintain sufficient colloid stability of dispersed TiO₂ P25. Under these conditions, TiO₂ P25 were unable to induce a significant impairment of A549 cells according to the results of biochemical and microscopy evaluations. When the defined parameters for the use of TiO₂ P25 in A549 cells were met, similar results on the biological effects of TiO₂ P25 were obtained in two independent cell laboratories.

Conclusion

We optimized the experimental conditions of TiO₂ P25 preparation for toxicity testing in A549 cells. The results presented here on TiO₂ P25-induced cellular effects are reproducible. Therefore, our results can be helpful for other researchers using TiO₂ P25 as a reference material.

Evaluation of TiO2 Nanoparticles Physicochemical Parameters Associated with their Antimicrobial Applications

Titanium dioxide nanoparticles (TiO2NPs) usage is increasing in everyday consumer products, hence, assessing their toxic impacts on living organisms and environment is essential. Various studies have revealed the significant role of TiO2NPs physicochemical properties on their toxicity. However, TiO2NPs are still poorly characterized with respect to their physicochemical properties, and environmental factors influencing their toxicity are either ignored or are too complex to be assessed under laboratory conditions. The outcomes of these studies are diverse and inconsistent due to lack of standard protocols. TiO2NPs toxicity also differs for in vivo and in vitro systems, which must also be considered during standardization of protocols to maintain uniformity and reproducibility of results. This review critically evaluates impact of different physicochemical parameters of TiO2NPs and other experimental conditions, employed in different laboratories in determining their toxicity towards bacteria. These important observations may be helpful in evaluation of environmental risks posed by these nanoparticles and this can further assist regulatory bodies in policymaking.

Industrial-relevant TiO2 types do not promote cytotoxicity in the A549 or TK6 cell lines regardless of cell specific interaction

Due to the expansive application of TiO₂ and its variance in physico-chemical characteristics, the toxicological profile of TiO₂, in all its various forms, requires evaluation. This study aimed to assess the hazard of five TiO₂ particle-types in relation to their cytotoxic profile correlated to their cellular interaction, specifically in human lymphoblast (TK6) and type-II alveolar epithelial (A549) cells. Treatment with the test materials was undertaken at a concentration range of 1-100 μg/cm² over 24 and 72 h exposure. TiO₂ interaction with both cell types was visualised by transmission electron microscopy, supported by energy-dispersive X-ray. None of the TiO₂ materials tested promoted cytotoxicity in either cell type over the concentration and time range studied. All materials were observed to interact with the A549 cells and were further noted to be internalised following 24 h exposure. In contrast, only the pigmentary rutile was internalised by TK6 lymphoblasts after 24 h exposure. Where uptake was observed there was no evidence, as determined by 2D microscopy techniques, of particle localisation within the nucleus of either cell type. This study indicates that industrially relevant TiO₂ particles demonstrate cell interactions that are cell-type dependent and do not induce cytotoxicity at the applied dose range.

DNA Oxidative Damage as a Sensitive Genetic Endpoint to Detect the Genotoxicity Induced by Titanium Dioxide Nanoparticles

The genotoxicity of nanomaterials has attracted great attention in recent years. As a possible occupational carcinogen, the genotoxic effects and underlying mechanisms of titanium dioxide nanoparticles (TiO2 NPs) have been of particular concern. In this study, the effect of TiO2 NPs (0, 25, 50 and 100 µg/mL) on DNA damage and the role of oxidative stress were investigated using human bronchial epithelial cells (BEAS-2B) as an in vitro model. After detailed characterization, the cytotoxicity of TiO2 NPs was detected. Through transmission electron microscopy (TEM), we found that TiO2 NPs entered the cytoplasm but did not penetrate deep into the nucleus of cells. The intracellular levels of reactive oxygen species (ROS) significantly increased in a dose-dependent manner and the ratios of GSH/GSSG also significantly decreased. The results of the normal comet assay were negative, while the Fpg-modified comet assay that specifically detected DNA oxidative damage was positive. Meanwhile, N-acetyl-L-cysteine (NAC) intervention inhibited the oxidative stress and genotoxicity induced by TiO2 NPs. Therefore, it was suggested that TiO2 NPs could induce cytotoxicity, oxidative stress and DNA oxidative damage in BEAS-2B cells. DNA oxidative damage may be a more sensitive genetic endpoint to detect the genotoxicity of TiO2 NPs.

Estimation of Titanium Dioxide Intake by Diet and Stool Assessment among US Healthy Adults

BACKGROUND

Titanium dioxide (TiO2/E171) is used in foods primarily as a whitening agent. Little is known regarding TiO2 exposure in the United States.

OBJECTIVES

To quantify stool TiO2 content among US adults and evaluate its association with estimated intake.

METHODS

Adults participated in phase 1 [three 24-h dietary recalls (DRs) and stool TiO2 measured from 3 matched samples (n = 52)] and/or phase 2 [tailored FFQ and stool TiO2 measured from 3 samples over 3 mo (n = 61)]. TiO2 in foods was estimated from a database, and concentration in 49 additional foods and 339 stool samples were quantified using inductively coupled plasma mass spectrometry. Associations between dietary and stool TiO2 were assessed by log-linear multivariable regression. USDA food groups (n = 49, servings/d) were related to stool TiO2 by stepwise regression.

RESULTS

TiO2 food content varied by brand. Mean TiO2 intake from three 24-h DRs [0.19 ± 0.31 mg/(kg body weight · d)] was lower than from the FFQ [0.30 ± 0.21 mg/(kg body weight · d)]. Dietary TiO2 was not predictive of stool TiO2, in phase 1 or phase 2, 10^(β) per 10 times higher dietary TiO2: 1.138 [10^(95% CI): 0.635, 2.037, P = 0.66] and 0.628 [10^(95% CI): 0.206, 1.910, P = 0.41], respectively. Food groups related to stool TiO2 were 1) milk desserts, sauces, and gravies [10^(β) per servings/d: 3.361; 10^(95% CI): 0.312, 36.163; P = 0.002] and 2) yeast breads [10^(β): 1.430; 10^(95% CI): 0.709, 2.884; P = 0.002] in phase 1 and 1) cream and cream substitutes [10^(β) = 10.925; 10^(95% CI): 1.952, 61.137; P = 0.01] and 2) milk and milk drinks [10^(β) = 0.306; 10^(95% CI): 0.086, 1.092, P = 0.07] in phase 2.

CONCLUSIONS

Intake of certain foods was associated with higher stool TiO2 content. There is a need for valid estimation of TiO2 intakes via the improvement of a dietary assessment method and a TiO2 food composition database. Future research should assess whether high stool TiO2 content is related to adverse health outcomes.

Titanium Dioxide: Structure, Impact, and Toxicity

Titanium dioxide, first manufactured a century ago, is significant in industry due to its chemical inertness, low cost, and availability. The white mineral has a wide range of applications in photocatalysis, in the pharmaceutical industry, and in food processing sectors. Its practical uses stem from its dual feature to act as both a semiconductor and light scatterer. Optical performance is therefore of relevance in understanding how titanium dioxide impacts these industries. Recent breakthroughs are summarised herein, focusing on whether restructuring the surface properties of titanium dioxide either enhances or inhibits its reactivity, depending on the required application. Its recent exposure as a potential carcinogen to humans has been linked to controversies around titanium dioxide's toxicity; this is discussed by illustrating discrepancies between experimental protocols of toxicity assays and their results. In all, it is important to review the latest achievements in fast-growing industries where titanium dioxide prevails, while keeping in mind insights into its disputed toxicity.

Advances in genotoxicity of titanium dioxide nanoparticles in vivo and in vitro

Titanium dioxide nanoparticles (TiO₂ NPs) are currently one of the most widely used nanomaterials. Due to an increasing scope of applications, the exposure of humans to TiO₂ NP is inevitable, such as entering the body through the mouth with food additives or drugs, invading the damaged skin with cosmetics, and entering the body through the respiratory tract during the process of production and handling. Compared with TiO₂ coarse particles, TiO₂ NPs have stronger conductivity, reaction activity, photocatalysis, and permeability, which may lead to greater toxicity to organisms. Given that TiO₂ was classified as a category 2B carcinogen (possibly carcinogenic to humans), the genotoxicity of TiO₂ NPs has become the focus of attention. There have been a series of previous studies investigating the potential genotoxicity of TiO₂ NPs, but the existing research results are still controversial and difficult to conclude. More than half of studies have shown that TiO₂ NPs can cause genotoxicity, suggesting that TiO₂ NPs are likely to be genotoxic to humans. And the genotoxicity of TiO₂ NPs is closely related to the exposure concentration, mode and time, and experimental cells/animals as well as its physicochemical properties (crystal type, size, and shape). This review summarized the latest research progress of related genotoxic effects through in vivo studies and in vitro cell tests, hoping to provide ideas for the evaluation of TiO₂ NPs genotoxicity.

How can exposure to engineered nanomaterials influence our epigenetic code? A review of the mechanisms and molecular targets

Evidence suggests that engineered nanomaterials (ENM) can induce epigenetic modifications. In this review, we provide an overview of the epigenetic modulation of gene expression induced by ENM used in a variety of applications: titanium dioxide (TiO₂), silver (Ag), gold (Au), silica (SiO₂) nanoparticles and carbon-based nanomaterials (CNM). Exposure to these ENM can trigger alterations in cell patterns of DNA methylation, post-transcriptional histone modifications and expression of non-coding RNA. Such effects are dependent on ENM dose and physicochemical properties including size, shape and surface chemistry, as well as on the cell/organism sensitivity. The genes affected are mostly involved in the regulation of the epigenetic machinery itself, as well as in apoptosis, cell cycle, DNA repair and inflammation related pathways, whose long-term alterations might lead to the onset or progression of certain pathologies. In addition, some DNA methylation patterns may be retained as a form of epigenetic memory. Prenatal exposure to ENM may impair the normal development of the offspring by transplacental effects and/or putative transmission of epimutations in imprinting genes. Thus, understanding the impact of ENM on the epigenome is of paramount importance and epigenetic evaluation must be considered when assessing the risk of ENM to human health.

Metal-Containing Nanoparticles in Low-Rank Coal-Derived Fly Ash from China: Characterization and Implications toward Human Lung Toxicity

Characterization of nanoparticles (NPs) in coal fly ashes (CFAs) is critical for better understanding the potential health-related risks resulting from coal combustion. Based on single-particle (SP)-inductively coupled plasma mass spectrometry (ICP-MS) coupled with transmission electron microscopy techniques, this study is the first to determine the concentrations and sizes of metal-containing NPs in low-rank coal-derived fly ashes. Despite only comprising a minor component of the studied CFAs by mass, NPs were the dominant fraction by particle number. Fe- and Ti-containing NPs were identified as the dominant NPs with their particle number concentration ranging from 2.5 × 10⁷ to 2.5 × 10⁸ particles/mg. In addition, the differences of Fe-/Ti-containing NPs in various CFAs were regulated by the coalification degree of feed coals and combustion conditions of all of the low-rank CFAs tested. In the cases where these NPs in CFAs become airborne and are inhaled, they can be taken up in pulmonary interstitial fluids. This study shows that in Gamble's solution (a lung fluid simulant), 51-87% of Fe and 63-89% of Ti (ratio of the mass of Fe-/Ti-containing NPs to the total mass of Fe/Ti) exist in the NP form and remain suspended in pulmonary fluid simulants. These NPs are bioavailable and may induce lung tissue damage.

A critical review on genotoxicity potential of low dimensional nanomaterials

Low dimensional nanomaterials (LDNMs) have earned attention among researchers as they exhibit a larger surface area to volume and quantum confinement effect compared to high dimensional nanomaterials. LDNMs, including 0-D and 1-D, possess several beneficial biomedical properties such as bioimaging, sensor, cosmetic, drug delivery, and cancer tumors ablation. However, they threaten human beings with the adverse effects of cytotoxicity, carcinogenicity, and genotoxicity when exposed for a prolonged time in industry or laboratory. Among different toxicities, genotoxicity must be taken into consideration with utmost importance as they inherit DNA related disorders causing congenital disabilities and malignancy to human beings. Many researchers have performed NMs' genotoxicity using various cell lines and animal models and reported the effect on various physicochemical and biological factors. In the present work, we have compiled a comparative study on the genotoxicity of the same or different kinds of NMs. Notwithstanding, we have included the classification of genotoxicity, mechanism, assessment, and affecting factors. Further, we have highlighted the importance of studying the genotoxicity of LDNMs and signified the perceptions, future challenges, and possible directives in the field.

Genotoxicity Evaluation of Titanium Dioxide Nanoparticles In Vitro: a Systematic Review of the Literature and Meta-analysis

With the wide use of titanium dioxide nanoparticles (TiO₂-NPs), the genotoxicity of TiO₂-NPs, which is a factor for safety assessment, has attracted people's attention. However, their genotoxic effects in vitro remain controversial due to inconsistent reports. Therefore, a systematic review was conducted followed by a meta-analysis to reveal whether TiO₂-NPs cause genotoxicity in vitro. A total of 59 studies were identified in this review through exhaustive database retrieval and exclusion. Meta-analysis results were presented based on different evaluation methods. The results showed that TiO₂-NP exposure considerably increased the percentage of DNA in tail and olive tail moment in comet assay. Gene mutation assay revealed that TiO₂-NPs could also induce gene mutation. However, TiO₂-NP exposure had no effect on micronucleus (MN) formation in the MN assay. Subgroup analysis showed that normal cells were more vulnerable to toxicity induced by TiO₂-NPs. Moreover, mixed form and small particles of TiO₂-NPs increased the percentage of DNA in tail. In addition, short-term exposure could detect more DNA damage. The size, coating, duration, and concentration of TiO₂-NPs influenced MN formation. This study presented that TiO₂-NP exposure could cause genotoxicity in vitro. The physicochemical properties of TiO₂-NPs and experimental protocols influence the genotoxic effects in vitro. Comet and gene mutation assays may be more sensitive to the detection of TiO₂-NP genotoxic effects.

Antimicrobial activities of chitosan/titanium dioxide composites as a biological nanolayer for food preservation: A review

Packaging is an integral part of food industry that preserves the properties of food during storage. Food spoilage caused by foodborne microorganisms is a public health problem that imposes a significant burden on the healthcare systems. Moreover, packaging based on artificial and chemical materials such as plastic is destructive to the environment. Chitosan can be categorized as an active food packaging material because of its inherent antimicrobial properties and capacity to carry various active components. Combining chitosan and metallic nanoparticles can be used as a practical approach in antimicrobial packaging systems. This strategy has advantages of thermal stability, barrier properties, antioxidant and antimicrobial packaging. Titanium dioxide is one of these nanoparticles that plays a photocatalytic role by releasing reactive oxygen species, thereby leading to the destruction of microorganisms' cell wall and extension of food shelf life. This review elaborates on the antimicrobial applications of chitosan/titanium dioxide nanoparticles films in food packaging systems.

Environmental Impact of Nanoparticles' Application as an Emerging Technology: A Review

The unique properties that nanoparticles exhibit, due to their small size, are the principal reason for their numerous applications, but at the same time, this might be a massive menace to the environment. The number of studies that assess the possible ecotoxicity of nanomaterials has been increasing over the last decade to determine if, despite the positive aspects, they should be considered a potential health risk. To evaluate their potential toxicity, models are used in all types of organisms, from unicellular bacteria to complex animal species. In order to better understand the environmental consequences of nanotechnology, this literature review aims to describe and classify nanoparticles, evaluating their life cycle, their environmental releasing capacity and the type of impact, particularly on living beings, highlighting the need to develop more severe and detailed legislation. Due to their diversity, nanoparticles will be discussed in generic terms focusing on the impact of a great variety of them, highlighting the most interesting ones for the industry.

Nanoparticle Surface Functionalization: How to Improve Biocompatibility and Cellular Internalization

The use of nanoparticles (NP) in diagnosis and treatment of many human diseases, including cancer, is of increasing interest. However, cytotoxic effects of NPs on cells and the uptake efficiency significantly limit their use in clinical practice. The physico-chemical properties of NPs including surface composition, superficial charge, size and shape are considered the key factors that affect the biocompatibility and uptake efficiency of these nanoplatforms. Thanks to the possibility of modifying physico-chemical properties of NPs, it is possible to improve their biocompatibility and uptake efficiency through the functionalization of the NP surface. In this review, we summarize some of the most recent studies in which NP surface modification enhances biocompatibility and uptake. Furthermore, the most used techniques used to assess biocompatibility and uptake are also reported.

Genotoxicity of Nanomaterials: Advanced In Vitro Models and High Throughput Methods for Human Hazard Assessment-A Review

Changes in the genetic material can lead to serious human health defects, as mutations in somatic cells may cause cancer and can contribute to other chronic diseases. Genotoxic events can appear at both the DNA, chromosomal or (during mitosis) whole genome level. The study of mechanisms leading to genotoxicity is crucially important, as well as the detection of potentially genotoxic compounds. We consider the current state of the art and describe here the main endpoints applied in standard human in vitro models as well as new advanced 3D models that are closer to the in vivo situation. We performed a literature review of in vitro studies published from 2000-2020 (August) dedicated to the genotoxicity of nanomaterials (NMs) in new models. Methods suitable for detection of genotoxicity of NMs will be presented with a focus on advances in miniaturization, organ-on-a-chip and high throughput methods.

Titanium dioxide nanoparticle genotoxicity: A review of recent in vivo and in vitro studies

Titanium dioxide nanoparticles (TiO2 NPs, size <100 nm) find applications in a wide range of products including food and cosmetics. Studies have found that exposure to TiO2 NPs can cause inflammation, cytotoxicity, genotoxicity and cell apoptosis. In this article, we have reviewed the recent literature on the potential of TiO2 NPs to cause genotoxicity and summarized the results of two standard genotoxicity assays, the comet and micronucleus (MN) assays. Analysis of these peer-reviewed publications shows that the comet assay is the most common genotoxicity test, followed by MN, Ames, and chromosome aberration tests. These assays have reported positive as well as negative results, although there is inconsistency in some results that need to be confirmed further by well-designed experiments. We also discuss the possible mechanisms of TiO2 NP genotoxicity and point out areas that warrant further research.

Oral exposure of titanium oxide nanoparticles induce ileum physical barrier dysfunction via Th1/Th2 imbalance

In this work, we aimed to evaluate the adverse effects and the mechanism of intestinal barrier caused by titanium dioxide nanoparticles (TiO₂ NPs). Here, the effects of two different dosages (300 and 1200 mg/kg) of TiO₂ NPs on female mice (n = 5) were investigated. After 28-day oral exposure, the results of Ti content were significantly increased in the ileum in comparison with the control. The histopathological structure index of the ileum was significantly changed after TiO₂ NPs exposure; villi height and crypt depth were decreased and increased, respectively. Meanwhile, TiO₂ NPs treatment also significantly altered the transcription levels of genes. First, the GATA-3 and STAT-4 were upregulation and downregulation, respectively. Second, gene expressions of the Zonula Occludens-1, claudin (CLDN)-12, occludin, and myosin light chain kinase were significantly upregulated, while the CLDN-3 was decreased. Finally, the caspase-3, caspase-9, and caspase-12 were upregulated. The results of TUNEL staining indicated apoptosis in the ileum. In general, TiO₂ NPs treatment significantly changed the intestine physical barrier in a dose-dependent manner. The toxicity of TiO₂ NPs could be through the imbalance in the Th1/Th2.

Impact of the Physicochemical Features of TiO2 Nanoparticles on Their In Vitro Toxicity

The concern about titanium dioxide nanoparticles (TiO₂-NPs) toxicity and their possible harmful effects on human health has increased. Their biological impact is related to some key physicochemical properties, that is, particle size, charge, crystallinity, shape, and agglomeration state. However, the understanding of the influence of such features on TiO₂-NP toxicity remains quite limited. In this study, cytotoxicity, proinflammatory response, and oxidative stress caused by five types of TiO₂-NPs with different physicochemical properties were investigated on A549 cells used either as monoculture or in co-culture with macrophages differentiated from the human monocytic THP-1 cells. We tailored bulk and surface TiO₂ physicochemical properties and differentiated NPs for size/specific surface area, shape, agglomeration state, and surface functionalization/charge (aminopropyltriethoxysilane). An impact on the cytotoxicity and to a lesser extent on the proinflammatory responses depending on cell type was observed, namely, smaller, large-agglomerated TiO₂-NPs were shown to be less toxic than P25, whereas rod-shaped TiO₂-NPs were found to be more toxic. Besides, the positively charged particle was slightly more toxic than the negatively charged one. Contrarily, TiO₂-NPs, whatever their physicochemical properties, did not induce significant ROS production in both cell systems compared to nontreated control groups. These results may contribute to a better understanding of TiO₂-NPs toxicity in relation with their physicochemical features.

Exposure Route of TiO2 NPs from Industrial Applications to Wastewater Treatment and Their Impacts on the Agro-Environment

The tremendous increase in the production and consumption of titanium dioxide (TiO2) nanoparticles (NPs) in numerous industrial products and applications has augmented the need to understand their role in wastewater treatment technologies. Likewise, the deleterious effects of wastewater on the environment and natural resources have compelled researchers to find out most suitable, economical and environment friendly approaches for its treatment. In this context, the use of TiO2 NPs as the representative of photocatalytic technology for industrial wastewater treatment is coming to the horizon. For centuries, the use of industrial wastewater to feed agriculture land has been a common practice across the globe and the sewage sludge generated from wastewater treatment plants is also used as fertilizer in agricultural soils. Therefore, it is necessary to be aware of possible exposure pathways of these NPs, especially in the perspective of wastewater treatment and their impacts on the agro-environment. This review highlights the potential exposure route of TiO2 NPs from industrial applications to wastewater treatment and its impacts on the agro-environment. Key elements of the review present the recent developments of TiO2 NPs in two main sectors including wastewater treatment and the agro-environment along with their potential exposure pathways. Furthermore, the direct exposure routes of these NPs from production to end-user consumption until their end phase needs to be studied in detail and optimization of their suitable applications and controlled use to ensure environmental safety.

The Toxicity Phenomenon and the Related Occurrence in Metal and Metal Oxide Nanoparticles: A Brief Review From the Biomedical Perspective

Thousands of different nanoparticles (NPs) involve in our daily life with various origins from food, cosmetics, drugs, etc. It is believed that decreasing the size of materials up to nanometer levels can facilitate their unfavorable absorption since they can pass the natural barriers of live tissues and organs even, they can go across the relatively impermeable membranes. The interaction of these NPs with the biological environment disturbs the natural functions of cells and its components and cause health issues. In the lack of the detailed and comprehensive standard protocols about the toxicity of NPs materials, their control, and effects, this review study focuses on the current research literature about the related factors in toxicity of NPs such as size, concentration, etc. with an emphasis on metal and metal oxide nanoparticles. The goal of the study is to highlight their potential hazard and the advancement of green non-cytotoxic nanomaterials with safe threshold dose levels to resolve the toxicity issues. This study supports the NPs design along with minimizing the adverse effects of nanoparticles especially those used in biological treatments.

TiO2 genotoxicity: An update of the results published over the last six years

TiO₂ particles are broadly used in daily products, including cosmetics for their UV-absorbing property, food for their white colouring property, water and air purification systems, self-cleaning surfaces and photoconversion electrical devices for their photocatalytic properties. The toxicity of TiO₂ nano- and microparticles has been studied for decades, and part of this investigation has been dedicated to the identification of their potential impact on DNA, i.e., their genotoxicity. This review summarizes data retrieved from their genotoxicity testing during the past 6 years, encompassing both in vitro and in vivo studies, mostly performed on lung and intestinal models. It shows that TiO₂ particles, both nano- and micro-sized, produce genotoxic damage to a variety of cell types, even at low, realistic doses.

Involvement of Bcl-2 Activation and G1 Cell Cycle Arrest in Colon Cancer Cells Induced by Titanium Dioxide Nanoparticles Synthesized by Microwave-Assisted Hybrid Approach

The toxic effect of TiO₂ nanoparticles (TNP) greatly varies with the variation in synthesis protocol followed. Any morphological alteration of TNPs affects their activity. In the present study, we report the detailed toxicological analysis of TNPs fabricated by a microwave irradiation–assisted hybrid chemical approach. The toxicological mechanism was studied in human colon cancer cell lines (HCT116). Results indicate that TNP induces oxidative stress on HCT116, which, in turn, causes mitochondrial membrane depolarization. We also observed activation of Bcl-2 and caspase-3 by Western blot analysis. This indicates TNPs induce mitochondrial-mediated apoptosis. Furthermore, G1 cell cycle arrest was observed by flow-cytometric analysis. This study provides an understanding of the mechanism of action for apoptosis induced by TNPs, which can be further used to design safe TNPs for various consumer products and also suggests that extensive research needs to be done on harmful effects of TNPs synthesized from different approaches before commercial application.

An in vivo study of nanorod, nanosphere, and nanowire forms of titanium dioxide using Drosophila melanogaster: toxicity, cellular uptake, oxidative stress, and DNA damage

The biological impact of nanomaterials (NMs) is determined by several factors such as size and shape, which need to be taken into consideration in any type of analysis. While investigators often prefer to conduct in vitro studies for detection of any possible adverse effects of NMs, in vivo approaches yield more relevant data for risk assessment. For this reason, Drosophila melanogaster was selected as a suitable in vivo model to characterize the potential risks associated with exposure nanorods (NRs), nanospheres (NSs), nanowires (NWs) forms of titanium dioxide (TiO₂), and their microparticulated (or bulk) form, as TiO₂. Third instar larvae (72 hr old larvae) were fed with TiO₂ (NRs, NSs, or NWs) and TiO₂ at concentrations ranging from 0.01 to 10 mM. Viability (toxicity), internalization (cellular uptake), intracellular reactive oxygen species (ROS) production, and genotoxicity (Comet assay) were the end-points evaluated in hemocyte D. melanogaster larvae. Significant intracellular oxidative stress and genotoxicity were noted at the highest exposure concentration (10 mM) of TiO₂ (NRs, NSs, or NWs), as determined by the Comet assay and ROS analysis, respectively. A concentration-effect relationship was observed in hemocytes exposed to the NMs. Data demonstrated that selected forms of TiO₂.-induced genotoxicity in D. melanogaster larvae hemocytes indicating this organism is susceptible for use as a model to examine in vivo NMs-mediated effects.

Titanium Dioxide Nanoparticles in Food and Personal Care Products-What Do We Know about Their Safety?

Titanium dioxide (TiO2) is a material of diverse applications commonly used as a food additive or cosmetic ingredient. Its prevalence in products of everyday use, especially in nanosize, raises concerns about safety. Current findings on the safety of titanium dioxide nanoparticles (TiO2 NPs) used as a food additive or a sunscreen compound are reviewed and systematized in this publication. Although some studies state that TiO2 NPs are not harmful to humans through ingestion or via dermal exposure, there is a considerable number of data that demonstrated their toxic effects in animal models. The final agreement on the safety of this nanomaterial has not yet been reached among researchers. There is also a lack of official, standardized guidelines for thorough characterization of TiO2 NPs in food and cosmetic products, provided by international authorities. Recent advances in the application of 'green-synthesized' TiO2 NPs, as well as comparative studies of the properties of 'biogenic' and 'traditional' nanoparticles, are presented. To conclude, perspectives and directions for further studies on the toxicity of TiO2 NPs are proposed.

Genotoxicity of TiO2 Nanoparticles in Four Different Human Cell Lines (A549, HEPG2, A172 and SH-SY5Y)

Titanium dioxide nanoparticles (TiO2 NPs) have a wide variety of applications in many consumer products, including as food additives, increasing the concern about the possible hazards that TiO2 NPs may pose to human health. Although most previous studies have focused on the respiratory system, ingestion must also be considered as an important exposure route. Furthermore, after inhalation or ingestion, TiO2 NPs can reach several organs, such as the liver, brain or lungs. Taking this into consideration, the present study focuses on the uptake and potential genotoxicity (micronuclei induction) of TiO2 NPs on four human cell lines of diverse origin: lung cells (A549), liver cells (HepG2), glial cells (A172) and neurons (SH-SY5Y), using flow cytometry methods. Results showed a concentration-, time- and cell-type- dependent increase in TiO2 NPs uptake but no significant induction of micronuclei in any of the tested conditions. Data obtained reinforce the importance of cell model and testing protocols choice for toxicity assessment. However, some questions remain to be answered, namely on the role of cell culture media components on the agglomeration state and mitigation of TiO2 NPs toxic effects.

Differences in cytotoxicity of lung epithelial cells exposed to titanium dioxide nanofibers and nanoparticles: Comparison of air-liquid interface and submerged cell cultures

Air Liquid Interface (ALI) system has emerged as a useful tool for toxicity evaluation of nanomaterials related to inhalation since the system mimics the aerosol exposure. We compared the biological responses of lung epithelial cells exposed to titanium dioxide (TiO₂) nanofibers and nanoparticles in ALI and submerged cell cultures systems. Cells were exposed to 2 and 10 μg/cm² for 24 h, 48 h and 72 h and LDH release, TiO₂ internalization, DNA-double strand breaks (DSBs) and ROS production were assessed. LDH release was similar in both systems and particles had higher cytoplasmic uptake in submerged systems. Both TiO₂ types were located in the cytoplasm but nanofibers had nuclear uptake regardless to the system tested. Cells exposed to TiO₂ nanofibers had higher DSBs in the ALI system than in submerged cell cultures but cells exposed to TiO₂ nanoparticles had similar DSBs in both systems. ROS production was higher in cells exposed to TiO₂ nanofibers compared to cells exposed to TiO₂ nanoparticles. In conclusion, cytotoxicity of lung epithelial cells was similar in ALI or submerged cell cultures, however cells exposed to TiO₂ nanofibers displayed higher toxicity than cells exposed to TiO₂ nanoparticles.

Genotoxicity assessment of titanium dioxide nanoparticle accumulation of 90 days in the liver of gpt delta transgenic mice

Backgound

A variety of in vivo and in vitro studies to assess the genotoxicity of titanium dioxide nanoparticles (TiO₂ NPs) have been reported, but the results are inconsistent. Recently, we reported that TiO₂ NPs exhibit no genotoxic effects in the liver and erythrocytes during a relatively brief period following intravenous injection into mice. However, there is no information about long-term genotoxicity due to TiO₂ NP accumulation in tissues. In this study, we investigated the long-term mutagenic effects of TiO₂ NPs and the localization of residual TiO₂ NPs in mouse liver after multiple intravenous injections.

Results

Male gpt delta C57BL/6 J mice were administered with various doses of TiO₂ NPs weekly for 4 consecutive weeks. The long-term mutagenic effects on the liver were analyzed using gpt and Spi⁻ mutation assays 90 days after the final injection. We also quantified the amount of titanium in the liver using inductively coupled plasma mass spectrometry and observed the localization of TiO₂ NPs in the liver using transmission electron microscopy. Although TiO₂ NPs were found in the liver cells, the gpt and Spi⁻ mutation frequencies in the liver were not significantly increased by the TiO₂ NP administration.

Conclusions

These results clearly show that TiO₂ NPs have no mutagenic effects on the liver, even though the particles remain in the liver long-term.

Flexible and Transparent Substrates Based on Gold Nanoparticles and TiO2 for in Situ Bioanalysis by Surface-Enhanced Raman Spectroscopy

Flexible and transparent substrates are emerging as low cost and easy-to-operate support for surface-enhanced Raman spectroscopy (SERS). In particular, in situ SERS detection approach for surface characterization in transmission modality can be efficiently employed for non-invasive analysis of non-planar surfaces. Here we propose a new methodology to fabricate a homogenous, transparent, and flexible SERS membrane by the assistance of a thin TiO2 porous layer deposited on the PDMS surface, which supports the uniform loading of gold nanoparticles over large area. The substrate was first characterized for homogeneity, sensitivity and repeatability using a model molecule for SERS, i.e., 7-mercapto-4-methylcoumarin. Satisfactory intra-substrate uniformity and inter-substrates repeatability was achieved, showing an RSD of 10%, and an analytical sensitivity down to 10 nM was determined with an EF of 3.4 × 105 ± 0.4 × 105. Furthermore, SERS detection of pyrimethanil (PMT), a commonly employed pesticide in crops for human consumption, was performed in situ, exploiting the optical transparency of the device, using both model surfaces and non-flat bio-samples. PMT contamination at the phytochemical concentration levels corresponding to commonly used infield doses was successfully detected on the surface of the yellow Ficus benjiamina leaves, supporting the use of this substrate for food safety in-field application.

The Comet Assay as a Tool to Detect the Genotoxic Potential of Nanomaterials

The interesting physicochemical characteristics of nanomaterials (NMs) has brought about their increasing use and, consequently, their increasing presence in the environment. As emergent contaminants, there is an urgent need for new data about their potential side-effects on human health. Among their potential effects, the potential for DNA damage is of paramount relevance. Thus, in the context of the EU project NANoREG, the establishment of common robust protocols for detecting genotoxicity of NMs became an important aim. One of the developed protocols refers to the use of the comet assay, as a tool to detect the induction of DNA strand breaks. In this study, eight different NMs—TiO₂NP (2), SiO₂NP (2), ZnONP, CeO₂NP, AgNP, and multi-walled carbon nanotubes (MWCNT)—were tested using two different human lung epithelial cell lines (A549 and BEAS-2B). The comet assay was carried out with and without the use of the formamidopyrimidine glycosylase (FPG) enzyme to detect the induction of oxidatively damaged DNA bases. As a high throughput approach, we have used GelBond films (GBF) instead of glass slides, allowing the fitting of 48 microgels on the same GBF. The results confirmed the suitability of the comet assay as a powerful tool to detect the genotoxic potential of NMs. Specifically, our results indicate that most of the selected nanomaterials showed mild to significant genotoxic effects, at least in the A549 cell line, reflecting the relevance of the cell line used to determine the genotoxic ability of a defined NM.

EFSA statement on the review of the risks related to the exposure to the food additive titanium dioxide (E 171) performed by the French Agency for Food, Environmental and Occupational Health and Safety (ANSES)

On 15 April 2019, the French Agency for Food, Environmental and Occupational Health and Safety (ANSES) published an opinion on the risks related to the exposure to the food additive titanium dioxide (E 171) taking into account the most recent scientific studies available. Further to this publication, EFSA was requested by the European Commission to provide urgent scientific and technical assistance regarding the opinion issued by ANSES. In the ANSES opinion, 25 new relevant publications published between 2017 and 2019 were reviewed together with previous opinions by EFSA and ANSES and a systematic review on in vitro genotoxicity of nano titanium dioxide. In this statement, EFSA concludes that the ANSES opinion published in April 2019 does not identify any major new findings that would overrule the conclusions made in the previous two scientific opinions on the safety of titanium dioxide (E 171) as a food additive issued by the EFSA ANS Panel in 2016 and 2018. The ANSES opinion reiterates the previously identified uncertainties and data gaps, which are currently being addressed in the context of the follow-up activities originating from the previous EFSA evaluations and their recommendations. In addition to the aspects for which the follow-up work is currently ongoing, ANSES recommends further investigation of in vivo genotoxicity. EFSA considers this recommendation should be revisited once the ongoing work on the physico-chemical characterisation of the food additive titanium dioxide (E 171) is completed.