Effects of Titanium Dioxide Nanoparticles Exposure on Human Health-a Review

Foodborne TiO2 Nanoparticles Induced More Severe Hepatotoxicity in Fructose-Induced Metabolic Syndrome Mice via Exacerbating Oxidative Stress-Mediated Intestinal Barrier Damage

The hazard of titanium dioxide nanoparticles (TiO₂ NPs) in diseased population should be given focus due to the huge number of these NPs in foods and medicine. This study aimed to evaluate the stronger biological adverse effect of oral exposure to TiO₂ NPs in a fructose-induced metabolic syndrome mouse model. Compared to the normal mice, low-dose (2 mg/kg) TiO₂ NPs did not cause severe hepatotoxicity. However, high-dose (20 mg/kg) TiO₂ NPs induced aggravated hepatic inflammation, fibrosis, and apoptosis, with substantial alteration of related biochemical parameters in the mouse model. Moreover, significantly increased Ti and lipopolysaccharide burden were observed in metabolic syndrome murine liver and serum, which possibly worsened the portend intestinal leakage. The expression of tight junction-related protein showed that TiO₂ NPs induced further increase in serious intestinal permeability. The intestinal inflammatory and oxidative stress response in the model were also assessed. Results showed that TiO₂ NPs caused more severe intestinal inflammatory injury by intensifying the oxidative stress in metabolic syndrome mice and then induced further liver injury. This work provides information on the insights into the toxic effect of TiO₂ NPs in sub-healthy population.

Four Types of TiO2 Reduced the Growth of Selected Lactic Acid Bacteria Strains

Food-grade titanium dioxide (TiO₂) containing a nanoparticle fraction (TiO₂ NPs -nanoparticles) is widely used as a food additive (E171 in the EU). In recent years, it has increasingly been raising controversies as to the presence or absence of its harmful effects on the gastrointestinal microbiota. The complexity and variability of microbiota species present in the human gastrointestinal tract impede the assessment of the impact of food additives on this ecosystem. As unicellular organisms, bacteria are a very convenient research model for investigation of the toxicity of nanoparticles. We examined the effect of TiO₂ (three types of food-grade E171 and one TiO₂ NPs, 21 nm) on the growth of 17 strains of lactic acid bacteria colonizing the human digestive tract. Each bacterial strain was treated with TiO₂ at four concentrations (60, 150, 300, and 600 mg/L TiO₂). The differences in the growth of the individual strains were caused by the type and concentration of TiO₂. It was shown that the growth of a majority of the analyzed strains was decreased by the application of E171 and TiO₂ NPs already at the concentration of 150 and 300 mg/L. At the highest dose (600 mg/L) of the nanoparticles, the reactions of the bacteria to the different TiO₂ types used in the experiment varied.

Tracking of Zinc Ferrite Nanoparticle Effects on Pea (Pisum sativum L.) Plant Growth, Pigments, Mineral Content and Arbuscular Mycorrhizal Colonization

Important gaps in knowledge remain regarding the potential of nanoparticles (NPs) for plants, particularly the existence of helpful microorganisms, for instance, arbuscular mycorrhizal (AM) fungi present in the soil. Hence, more profound studies are required to distinguish the impact of NPs on plant growth inoculated with AM fungi and their role in NP uptake to develop smart nanotechnology implementations in crop improvement. Zinc ferrite (ZnFe₂O₄) NPs are prepared via the citrate technique and defined by X-ray diffraction (XRD) as well as transmission electron microscopy for several physical properties. The analysis of the XRD pattern confirmed the creation of a nanocrystalline structure with a crystallite size equal to 25.4 nm. The effects of ZnFe₂O₄ NP on AM fungi, growth and pigment content as well as nutrient uptake of pea (Pisum sativum) plants were assessed. ZnFe₂O₄ NP application caused a slight decrease in root colonization. However, its application showed an augmentation of 74.36% and 91.89% in AM pea plant shoots and roots’ fresh weights, respectively, compared to the control. Moreover, the synthesized ZnFe₂O₄ NP uptake by plant roots and their contents were enhanced by AM fungi. These findings suggest the safe use of ZnFe₂O₄ NPs in nano-agricultural applications for plant development with AM fungi.

Suitability of Different Titanium Dioxide Nanotube Morphologies for Photocatalytic Water Treatment

Photocatalysis has long been touted as one of the most promising technologies for environmental remediation. The ability of photocatalysts to degrade a host of different pollutants, especially recalcitrant molecules, is certainly appealing. Titanium dioxide (TiO₂) has been used extensively for this purpose. Anodic oxidation allows for the synthesis of a highly ordered nanotubular structure with a high degree of tunability. In this study, a series of TiO₂ arrays were synthesised using different electrolytes and different potentials. Mixed anatase-rutile photocatalysts with excellent wettability were achieved with all the experimental iterations. Under UVA light, all the materials showed significant photoactivity towards different organic pollutants. The nanotubes synthesised in the ethylene glycol-based electrolyte exhibited the best performance, with near complete degradation of all the pollutants. The antibacterial activity of this same material was similarly high, with extremely low bacterial survival rates. Increasing the voltage resulted in wider and longer nanotubes, characteristics which increase the level of photocatalytic activity. The ease of synthesis coupled with the excellent activity makes this a viable material that can be used in flat-plate reactors and that is suitable for photocatalytic water treatment.

Nanomaterials in the environment, human exposure pathway, and health effects: A review

Nanomaterials (NMs), both natural and synthetic, are produced, transformed, and exported into our environment daily. Natural NMs annual flux to the environment is around 97% of the total and is significantly higher than synthetic NMs. However, synthetic NMs are considered to have a detrimental effect on the environment. The extensive usage of synthetic NMs in different fields, including chemical, engineering, electronics, and medicine, makes them susceptible to be discharged into the atmosphere, various water sources, soil, and landfill waste. As ever-larger quantities of NMs end up in our environment and start interacting with the biota, it is crucial to understand their behavior under various environmental conditions, their exposure pathway, and their health effects on human beings. This review paper comprises a large portion of the latest research on NMs and the environment. The article describes the natural and synthetic NMs, covering both incidental and engineered NMs and their behavior in the natural environment. The review includes a brief discussion on sampling strategies and various analytical tools to study NMs in complex environmental matrices. The interaction of NMs in natural environments and their pathway to human exposure has been summarized. The potential of NMs to impact human health has been elaborated. The nanotoxicological effect of NMs based on their inherent properties concerning to human health is also reviewed. The knowledge gaps and future research needs on NMs are reported. The findings in this paper will be a resource for researchers working on NMs all over the world to understand better the challenges associated with NMs in the natural environment and their human health effects.

Comparative Photo-Electrochemical and Photocatalytic Studies with Nanosized TiO2 Photocatalysts towards Organic Pollutants Oxidation

The size of TiO2 can significantly affect both its photocatalytic and photo-electrochemical properties, thus altering the photooxidation of organic pollutants in air or water. In this work, we give an account of the photo-electrochemical and photocatalytic features of some nanosized TiO2 commercial powders towards a model reaction, the photooxidation of acetone. Cyclic voltammograms (CV) of TiO2 particulate electrodes under UV illumination experiments were carried out in either saturated O2 or N2 solutions for a direct correlation with the photocatalytic process. In addition, the effect of different reaction conditions on the photocatalytic efficiency under UV light in both aqueous and gaseous phases was also investigated. CV curves with the addition of acetone under UV light showed a negative shift of the photocurrent onset, confirming the efficient transfer of photoproduced reactive oxygen species (ROSs), e.g., hydroxyl radicals or holes to acetone molecules. The photocatalytic experiments showed that the two nano-sized samples exhibit the best photocatalytic performance. The different photoactivity of the larger-sized samples is probably attributed to their morphological differences, affecting both the amount and distribution of free ROSs involved in the photooxidation reaction. Finally, a direct correlation between the photocatalytic measurements in gas phase and the photo-electrochemical measurements in aqueous phase is given, thus evincing the important role of the substrate-surface interaction with similar acetone concentrations.

Nanomaterials and the Serosal Immune System in the Thoracic and Peritoneal Cavities

The thoracic and peritoneal cavities are lined by serous membranes and are home of the serosal immune system. This immune system fuses innate and adaptive immunity, to maintain local homeostasis and repair local tissue damage, and to cooperate closely with the mucosal immune system. Innate lymphoid cells (ILCs) are found abundantly in the thoracic and peritoneal cavities, and they are crucial in first defense against pathogenic viruses and bacteria. Nanomaterials (NMs) can enter the cavities intentionally for medical purposes, or unintentionally following environmental exposure; subsequent serosal inflammation and cancer (mesothelioma) has gained significant interest. However, reports on adverse effects of NM on ILCs and other components of the serosal immune system are scarce or even lacking. As ILCs are crucial in the first defense against pathogenic viruses and bacteria, it is possible that serosal exposure to NM may lead to a reduced resistance against pathogens. Additionally, affected serosal lymphoid tissues and cells may disturb adipose tissue homeostasis. This review aims to provide insight into key effects of NM on the serosal immune system.

Optimisation and application of an analytical approach for the characterisation of TiO2 nanoparticles in food additives and pharmaceuticals by single particle inductively coupled plasma-mass spectrometry

This study was designed to optimise an analytical method for characterising TiO₂ nanoparticles (NPs) in food additives and pharmaceuticals by inductively coupled plasma-mass spectrometry in single particle mode (spICP-MS). Several parameters, including transport efficiency (TE), were assessed and optimised using the NM-100 reference material. We found that self-aspiration for sample intake and use of the concentration-based method for TE was optimal for characterising TiO₂ NPs. No spectral interference was observed with either ⁴⁹Ti or ⁴⁸Ti isotopes. The optimised Excel spreadsheet developed for this study not only provided additional parameters but gave results closer to the NM-100 reference value than the ICP-MS software. The method was then applied to the analysis of a selection of food samples and pharmaceuticals. The average diameter of TiO₂ particles ranged from 86 to 179 nm in the food samples and from 131 to 197 nm in the pharmaceuticals, while the nanoparticular fraction was between 19 and 68% in food, and between 13 and 45% in pharmaceuticals.

Estimates of lung burden risk associated with long-term exposure to TiO2 nanoparticles as a UV-filter in sprays

Titanium dioxide (TiO2) nanoparticles (NPs) are employed as an ultraviolet filter in sunscreen products because of their high ultraviolet absorptivity. However, sunscreen sprays may pose health risks due to the toxicity of inhaled TiO2 NPs. Therefore, we estimated the potential human health risk posed by inhaled TiO2 NPs emitted from sunscreen sprays. The physiology-based lung model was employed to predict the lung TiO2 NPs burden caused by long-term exposure. A Hill-based dose-response model described the relationship between lung inflammation and TiO2 NP accumulation. The Weibull threshold model was used to estimate the threshold amount of accumulation inducing 0.5% of the maximum increase in neutrophils. The potential health risk was assessed using a hazard quotient-based probabilistic risk model. All data obtained to date indicate that application of sunscreen sprays poses no significant health risk. However, using data simulations based on the threshold criterion, we discovered that in terms of practical strategies for preventing the risks posed by inhaled TiO2 NPs emitted from spray products, the suggested daily use amount and pressing number are 40 g (95% confidence interval: 11-146 g) and 66 (18-245), respectively. In this study, we successfully translated the potential health risk of long-term exposure to NP-containing sunscreen sprays and recommendations for daily application into mechanistic insights.

Aggregation kinetics of diesel soot nanoparticles in artificial and human sweat solutions: Effects of sweat constituents, pH, and temperature

Soot nanoparticles (SNPs) are airborne contaminants that could potentially penetrate skin, but their aggregation after contact with sweat may lower their health risks. This study investigated SNP aggregation kinetics in 4 artificial sweat standards and 21 human sweat samples. Effects of sweat inorganic (NaCl, Na₂HPO₄, and NaH₂PO₄) and organic (L-histidine, lactic acid, and urea) constituents, pH, temperature, and concentrations were examined. Results showed that SNP aggregation rates in 4 standards followed American Association of Textile Chemists and Colorists (AATCC) > British Standard (EN) > International Standard Organization (ISO) pH 5.5 > ISO pH 8.0, and could be described by the Derjaguin-Landau-Verwey-Overbeek (DLVO) theory. The aggregation rates increased with concentrations of SNPs, inorganic salts, L-histidine, and lactic acid, decreased with increasing pH and concentration of urea, and were weakly influenced by temperature. Systematic characterizations revealed SNP adsorption for organic sweat constituents. SNPs aggregated rapidly to ∼1000 nm in AATCC, but remained stable in ISO pH 8.0 and > 14/21 human sweat fluids over 20 min. The SNP aggregation rates correlated negatively with pH (r = -0.531*) and |ζ potential| (r = -0.464*) of human sweat samples. Sweat evaporation could promote aggregation of SNPs, hence lowering their potential harm via dermal exposure.

Tinospora cordifolia ameliorated titanium dioxide nanoparticle-induced toxicity via regulating oxidative stress-activated MAPK and NRF2/Keap1 signaling pathways in Nile tilapia (Oreochromis niloticus)

Titanium dioxide nanoparticle (TNP) has been suggested for use in fish farms to prevent or alleviate bacterial diseases owing to its bactericidal property. Unfortunately, the interaction of TNP with cells impaired the host defenses of fish resulting in increased mortality during bacterial challenges. The present study evaluated the efficacy of the ethanolic extract of Tinospora cordifolia (TCE) as a dietary supplement in ameliorating TNP induced toxicity in Nile tilapia (Oreochromis niloticus). The fishes were exposed to environmentally relevant concentration (10 mg/L) of TNP for 14 days and the effect of TCE supplemented feed at 3 different doses (5, 10, and 15 g/kg) was studied. TCE signally increased the weight gain, specific growth rate, and decreased feed conversion ratio in fish. TCE significantly (P < 0.05) ameliorated the toxic effects caused by TNP by increasing the antioxidant (CAT, SOD, GPx) activity and decreasing the levels of serum enzymes (ALT, AST, ALP, ACP), macromolecular oxidation, excessive ROS production, and pro-inflammatory cytokines (IL-1β, IL-6, IL-8, INF-γ, TNF-α, PGE-2). TNP bioaccumulation and histopathological alterations in gill, liver, and kidney were also significantly alleviated by TCE supplementation. TCE perceptibly regulated the expression of heat shock proteins (HSP60, -70), MAPKs (pERK1/2, pp38), antioxidant (NRF2, Keap1, HO-1), apoptotic (p53, PDRG1), and anti-apoptotic (AKT, Bcl2) proteins in fish. Regarding disease resistance, the TCE co-treated groups showed reduced cumulative mortality and higher relative percent survival with A. hydrophila. Our results suggest that TNP-induced apoptosis is mediated by the MAPK/NRF2/Keap1 pathway and underlines the therapeutic potential of TCE in aqua-farming.

Plant isoflavones can affect accumulation and impact of silver and titania nanoparticles on ovarian cells

Objectives. The application of nanoparticles is experiencing a rapid growth, but it faces a problem of their toxicity, especially adverse effects on female reproduction. Food and medicinal plants and their isoflavones can be protectors against environmental stressors, but their ability to abate the adverse effects of nanoparticles has not been studied yet. In the present study, we examined the effect of silver (AgNPs) and titanium dioxide (titania, TiO2NPs) nanoparticles alone or in combination with plant phytoestrogens/antioxidants (resveratrol, diosgenin, and quercetin) on accumulation of nanoparticles, and progesterone release by cultured porcine ovarian granulosa cells.Methods. Porcine granulosa cells were incubated in the presence of AgNPs or TiO2NPs (0.1, 1, 10 or 100 µg/ml) alone or in combination with resveratrol, diosgenin or quercetin (10 µg/ml) for 48 h. The accumulation of tested nanoparticles by granulosa cells was assessed under light microscope. Progesterone concentration in culture media was measured by ELISA kit.Results. Cells accumulated both AgNPs and TiO2NPs in a dose-dependent manner. AgNPs, but not TiO2NPs, at highest dose (100 µg/ml) resulted in a destruction of cell monolayer. Both Ag-NPs and TiO2NPs reduced progesterone release. Resveratrol, diosgenin, and quercetin promoted accumulation of both AgNPs and TiO2NPs in ovarian cells and inhibited the progesterone output. Furthermore, resveratrol and diosgenin, but not quercetin, prevented the suppressive action of both AgNPs, and TiO2NPs on progesterone release.Conclusions. These observations (1) demonstrate accumulation of AgNPs and TiO2NPs in ovarian cells, (2) confirm the toxic impact of AgNPs, and TiO2NPs on these cells, (3) confirm the inhibitory effects of plant polyphenols/phytoestrogens on ovarian steroidogenesis, (4) show the ability of these isoflavones to increase the accumulation of AgNPs and TiO2NPs, and (5) show their ability to reduce the suppressive effect of AgNPs and TiO2NPs on ovarian progesterone release. The suppressive effect of AgNPs and TiO2NPs on ovarian functions should be taken into account by their exposition. However, these adverse effects could be mitigated by some plant isoflavones.

Toxicological Consequences of Titanium Dioxide Nanoparticles (TiO2NPs) and Their Jeopardy to Human Population

Titanium dioxide nanoparticles (TiO2 NPs) are the most produced nanomaterial for food additives, pigments, photocatalysis, and personal care products. These nanomaterials are at the forefront of rapidly developing indispensable nanotechnology. In all these nanomaterials, titanium dioxide (TiO2) is the most common nanomaterial which is being synthesized for many years. These nanoparticles of TiO2 are widely used at the commercial level, especially in cosmetic industries. High usage in such a way has increased the toxicological consequences of the human population. Several studies have shown that TiO2 NPs accumulated after oral exposure or inhalation in the alimentary canal, lungs, heart, liver, spleen, cardiac muscle, and kidneys. Additionally, in mice and rats, they disturb glucose and lipid homeostasis. Moreover, TiO2 nanoparticles primarily cause adverse reactions by inducing oxidative stress that leads to cell damage, inflammation, genotoxicity, and adverse immune responses. The form and level of destruction are strongly based on the physical and chemical properties of TiO2 nanoparticles, which administer their reactivity and bioavailability. Studies give indications that TiO2 NPs cause both DNA strand breaks and chromosomal damages. The effects of genotoxicity do not depend only on particle surface changes, size, and exposure route, but also relies on the duration of exposure. Most of these effects may be because of a very high dose of TiO2 NPs. Despite increased production and use, epidemiological data for TiO2 NPs is still missing. This review discusses previous research regarding the impact of TiO2 NP toxicity on human health and highlights areas that require further understanding in concern of jeopardy to the human population. This review is important to point out areas where extensive research is needed; thus, their possible impact on individual health should be investigated in more details.

Assessment of the Influence of Crystalline Form on Cyto-Genotoxic and Inflammatory Effects Induced by TiO2 Nanoparticles on Human Bronchial and Alveolar Cells

Titanium dioxide nanoparticles (TiO₂NPs) are increasingly used in consumer products, industrial and medical applications, raising concerns on their potential toxicity. The available in vitro and in vivo studies on these NPs show controversial results. Crystalline structure is the physicochemical characteristic that seems to influence mainly TiO₂NPs toxicity, so its effect needs to be further studied. We aimed to study whether and how crystalline form influences potential cyto-genotoxic and inflammatory effects induced by two commercial TiO₂NPs (TiO₂-A, mainly anatase; TiO₂-B, mainly rutile) in human alveolar A549 and bronchial BEAS-2B cells exposed to 1–40 µg/mL. Cell viability (WST-1), membrane damage (LDH release), IL-6, IL-8 and TNF-α release (ELISA) and direct/oxidative DNA damage (fpg-comet assay) were evaluated. Physicochemical characterization included analysis of crystalline form (TEM and XRD), specific surface area (BET), agglomeration (DLS) and Z-potential (ELS). Our results show that TiO₂-A NPs induce in BEAS-2B cytotoxicity and a slight inflammation and in A549 slight oxidative effects, whereas TiO₂-B NPs induce genotoxic/oxidative effects in both cell lines, revealing different toxicity mechanisms for the two tested NPs. In conclusion, our study confirms the influence of crystalline form on cellular response, also demonstrating the suitability of our in vitro model to screen early TiO₂NPs effects.

A review of the impact of xenobiotics from dietary sources on infant health: Early life exposures and the role of the microbiota

Xenobiotics are worldwide distributed and humans are unavoidably exposed to multiple chemical compounds during life, from preconception to adulthood. The human microbiota is mainly settled during early life and modulate host health and fitness. One of the main routes for chemical exposure is by intake of contaminated food and water. Thus, the interplay between diet-xenobiotics-microbiota during pregnancy and perinatal period may have relevant consequences for infant and adult health. Maternal exposure to metal(oid)s, persistent organic pollutants, and some food additives can modify the infant's microbiota with unknown consequences for child or adult health. Toxicants' exposure may also modulate the maternal transfer of microorganisms to the progeny during birth and breastfeeding; however, scarce information is available. The rapid increase in releasing novel chemicals to the environment, the exposure to chemical mixtures, the chronic/low dose scenario, and the delay in science-stakeholders action call for novel and groundbreaking approaches to improve a comprehensive risk assessment in sensitive population groups like pregnant women and neonates, with emphasis on microbiota as modulating factor and target-organ of xenobiotic's toxicity.

Rapid and continuous fabrication of TiO2 nanoparticles encapsulated by polyimide fine particles using a multistep flow-system and their application

PI fine particles encapsulating a large number of TiO₂ nanoparticles (PI FPs/TiO₂ NPs) were successfully fabricated rapidly and continuously by the emulsion re-precipitation method using a multistep flow synthetic system. The fabricated material, PI FPs/TiO₂ NPs, was spherical in structure with a diameter of 214 nm, and the mean size of TiO₂ NPs was 5.2 nm. Line scan elemental analysis with SEM-EDX showed that the TiO₂ NPs were disproportionately embedded near the surface of the PI FPs. UV-vis transmission spectra revealed high UV shielding efficiency of the PI FPs/TiO₂ NPs as the NPs are located near the surface.

We rapidly and continuously fabricated TiO₂ nanoparticles encapsulated by polymer fine particles, and the fabricated nanomaterials showed high UV shielding efficiency.

Emerging nanomaterials for dental treatments

The emergence of nanomaterials for dental treatments is encouraged by the nanotopography of the tooth structure, together with the promising benefits of nanomedicine. The use of nanoparticles in dentistry, also termed as 'nanodentistry', has manifested in applications for remineralisation, antimicrobial activity, local anaesthesia, anti-inflammation, osteoconductivity and stem cell differentiation. Besides the applications on dental tissues, nanoparticles have been used to enhance the mechanical properties of dental composites, improving their bonding and anchorage and reducing friction. The small particle size allows for enhanced permeation into deeper lesions, and reduction in porosities of dental composites for higher mechanical strength. The large surface area to volume ratio allows for enhanced bioactivity such as bonding and integration, and more intense action towards microorganisms. Controlled release of encapsulated bioactive molecules such as drugs and growth factors enables them to be delivered more precisely, with site-targeted delivery for localised treatments. These properties have benefitted across multiple fields within dentistry, including periodontology and endodontics and reengineering of dental prosthetics and braces. This review summarises the current literature on the emerging field of nanomaterials for dental treatments.

Influence of the physicochemical features of TiO2 nanoparticles on the formation of a protein corona and impact on cytotoxicity

Due to their unique properties TiO2 nanoparticles are widely used. The adverse effects they may elicit are usually studied in relation to their physicochemical features. However, a factor is often neglected: the influence of the protein corona formed around nanoparticles upon contact with biological media. Indeed, although it is acknowledged that it can strongly influence nanoparticle toxicity, it is not systematically considered. The aim of this study was to characterize the formation of the protein corona of TiO2 nanoparticles as a function of the main nanoparticle properties and investigate potential relationship with the cytotoxicity nanoparticles induce in vitro in human lung cells. To that purpose, five TiO2 nanoparticles differing in size, shape, agglomeration state and surface charge were incubated in cell culture media (DMEM or RPMI supplemented with 10% fetal bovine serum) and the amount and profile of adsorbed proteins on each type of nanoparticle were compared to their toxicological profile. While nanoparticle size and surface charge were found to be determinant factors for protein corona formation, no clear impact of the shape and agglomeration state was observed. Furthermore, no clear relationship was evidenced between the protein corona of the nanoparticles and the adverse effect they elicited.

Interaction of nanoparticles with biological macromolecules: a review of molecular docking studies

The high frequency of using engineered nanoparticles in various medical applications entails a deep understanding of their interaction with biological macromolecules. Molecular docking simulation is now widely used to study the binding of different types of nanoparticles with proteins and nucleic acids. This helps not only in understanding the mechanism of their biological action but also in predicting any potential toxicity. In this review, the computational techniques used in studying the nanoparticles interaction with biological macromolecules are covered. Then, a comprehensive overview of the docking studies performed on various types of nanoparticles will be offered. The implication of these predicted interactions in the biological activity and/or toxicity is also discussed for each type of nanoparticles.

Neutrophil activation by nanomaterials in vitro: comparing strengths and limitations of primary human cells with those of an immortalized (HL-60) cell line

Assessment of nanomaterial (NM) induced inflammatory responses has largely relied on rodent testing via measurement of leukocyte accumulation in target organs. Despite observations that NMs activate neutrophil driven inflammatory responses in vivo, a limited number of studies have investigated neutrophil responses to NMs in vitro. We compared responses between the human neutrophil-like HL-60 cell line and human primary neutrophils following exposure to silver (Ag), zinc oxide (ZnO), copper oxide (CuO) and titanium dioxide (TiO₂) NMs. NM cytotoxicity and neutrophil activation were assessed by measuring cellular metabolic activity, cytokine production, respiratory burst, and release of neutrophil extracellular traps. We observed a similar pattern of response between HL-60 cells and primary neutrophils, however we report that some neutrophil functions are compromised in the cell line. Ag NMs were consistently observed to stimulate neutrophil activation, with CuO NMs inducing similar though weaker responses. TiO₂ NMs did not induce a neutrophil response in either cell type. Interestingly, ZnO NMs readily induced activation of HL-60 cells but did not appear to activate primary cells. Our findings are relevant to the development of a tiered testing strategy for NM hazard assessment which promotes the use of non-rodent models. Whilst we acknowledge that HL-60 cells may not be a perfect substitute for primary cells and require further investigation regarding their ability to predict neutrophil activation, we recommend their use for initial screening of NM-induced inflammation. Primary human neutrophils can then be used for more focused assessments of neutrophil activation before progressing to in vivo models where necessary.

The toxic influence of silver and titanium dioxide nanoparticles on cultured ovarian granulosa cells

The application of metal nanoparticles in modern society is growing, but there is insufficient data concerning their influence on reproductive processes and comparison of their biological activity. The present experiments aimed to compare the effects of silver and titanium dioxide nanoparticles (AgNPs and TiO2NPs) on ovarian granulosa cell functions. AgNPs and TiO2NPs were added to culture of porcine granulosa cells at doses 0, 0.01, 0.1, 1 or 10 μg/mL. The mRNAs for proliferating cell nuclear antigen (PCNA), cyclin B1, bax and caspase 3 were quantified by RT-PCR; release of progesterone was analyzed by ELISA. It was shown that both AgNPs and TiO2NPs significantly reduced all the measured parameters. ED₅₀ of the inhibitory influence of AgNPs on the main ovarian cell parameters was higher than ED₅₀ of TiO2NPs. The ability of AgNPs and TiO2NPs to suppress ovarian granulosa cell functions should be taken into account by their application.

Hepatotoxicity induced by nanomaterials: mechanisms and in vitro models

The unique physicochemical properties of materials at nanoscale have opened a plethora of opportunities for applications in the pharmaceutical and medical field, but also in consumer products from food and cosmetics industries. As a consequence, daily human exposure to nanomaterials through distinct routes is considerable and, therefore, may raise health concerns. Many nanomaterials have been described to accumulate and induce adversity in the liver. Among these, silica and some types of metallic nanoparticles are the most broadly used in consumer products and, therefore, the most studied and reported. The reviewed literature was collected from PubMed.gov during the month of March 2020 using the search words "nanomaterials induced hepatotoxicity", which yielded 181 papers. This present paper reviews the hepatotoxic effects of nanomaterials described in in vitro and in vivo studies, with emphasis on the underlying mechanisms. The induction of oxidative stress and inflammation are the manifestations of toxicity most frequently reported following exposure of cells or animal models to different nanomaterials. Furthermore, the available in vitro models for the evaluation of the hepatotoxic effects of nanomaterials are discussed, highlighting the continuous interest in the development of more advanced and reliable in vitro models for nanotoxicology.

Exposure to TiO2 Nanoparticles Increases Listeria monocytogenes Infection of Intestinal Epithelial Cells

Titanium dioxide nanoparticles (TiO2 NPs) are widely used in a variety of consumer products. Cellular exposure to TiO2 NPs results in complex effects on cell physiology that could impact biological systems. We investigated the behavior of Listeria monocytogenes in intestinal epithelial cells pre-treated with either a low or high (1 and 20 µg/cm2) dose of TiO2 NPs. Our results indicate that the pre-treated cells with a low dose became more permissive to listeria infection; indeed, both adhesion and invasion were significantly increased compared to control. Increased invasion seems to be correlated to cytoskeletal alterations induced by nanoparticles, and higher bacterial survival might be due to the high levels of listeriolysin O that protects L. monocytogenes from reactive oxygen species (ROS). The potential risk of increased susceptibility to L. monocytogenes infection related to long-term intake of nanosized TiO2 at low doses should be considered.

Quantification of titanium dioxide nanoparticles in human urine by single-particle ICP-MS

The increasing use of titanium dioxide nanoparticles in daily use consumer products such as cosmetics, personal care products, food additives, and even medicine has led to growing concerns regarding human safety. It would be ideal to track exposure to this emerging nanopollutant, for example through bioassays, however, so far nanoparticle assessment in biological matrices such as urine remains challenging. The lack of data is mainly due to the limitations of the current metrology, but also to the low expected concentration in human samples. In this study, a quantification method for titanium dioxide nanoparticles in urine has been developed and validated following the ISO/CEI 17025:2017 guidelines. The detection limit for titanium dioxide nanoparticle mass concentration by single-particle inductively coupled plasma mass spectrometry (SP-ICP-MS) was 0.05 ng mL^-1. The particle size limit was determined using three different approaches, with the highest calculated limit value approaching 50 nm. Repeatability and reproducibility of 14% and 18% respectively were achieved for particle mass concentration, and 6% for both parameters for particle size determination. Method trueness and recovery were 98% and 84%, respectively.

Are Titania Photocatalysts and Titanium Implants Safe? Review on the Toxicity of Titanium Compounds

Titanium and its compounds are broadly used in both industrial and domestic products, including jet engines, missiles, prostheses, implants, pigments, cosmetics, food, and photocatalysts for environmental purification and solar energy conversion. Although titanium/titania-containing materials are usually safe for human, animals and environment, increasing concerns on their negative impacts have been postulated. Accordingly, this review covers current knowledge on the toxicity of titania and titanium, in which the behaviour, bioavailability, mechanisms of action, and environmental impacts have been discussed in detail, considering both light and dark conditions. Consequently, the following conclusions have been drawn: (i) titania photocatalysts rarely cause health and environmental problems; (ii) despite the lack of proof, the possible carcinogenicity of titania powders to humans is considered by some authorities; (iii) titanium alloys, commonly applied as implant materials, possess a relatively low health risk; (iv) titania microparticles are less toxic than nanoparticles, independent of the means of exposure; (v) excessive accumulation of titanium in the environment cannot be ignored; (vi) titanium/titania-containing products should be clearly marked with health warning labels, especially for pregnant women and young children; (vi) a key knowledge gap is the lack of comprehensive data about the environmental content and the influence of titania/titanium on biodiversity and the ecological functioning of terrestrial and aquatic ecosystems.

Food additives containing nanoparticles induce gastrotoxicity, hepatotoxicity and alterations in animal behavior: The unknown role of oxidative stress

Food additives such as titanium dioxide (E171), iron oxides and hydroxides (E172), silver (E174), and gold (E175) are highly used as colorants while silicon dioxide (E551) is generally used as anticaking in ultra-processed foodstuff highly used in the Western diets. These additives contain nanosized particles (1-100 nm) and there is a rising concern since these nanoparticles could exert major adverse effects due to they are not metabolized but are accumulated in several organs. Here, we analyze the evidence of gastrotoxicity, hepatotoxicity and the impact of microbiota on gut-brain and gut-liver axis induced by E171, E172, E174, E175 and E551 and their non-food grade nanosized counterparts after oral consumption. Although, no studies using these food additives have been performed to evaluate neurotoxicity or alterations in animal behavior, their non-food grade nanosized counterparts have been associated with stress, depression, cognitive and eating disorders as signs of animal behavior alterations. We identified that these food additives induce gastrotoxicity, hepatotoxicity and alterations in gut microbiota and most evidence points out oxidative stress as the main mechanism of toxicity, however, the role of oxidative stress as the main mechanism needs to be explored further.

Comparison of respiratory toxicity of TiO2 and Fe3O4 nanoparticles after intravenous instillation: an experimental study

OBJECTIVE

Nanomaterials consist of particles smaller than 100 nm - nanoparticles (NPs). Their nano dimensions allow them to penetrate through various membranes and enter into the bloodstream and disseminate into different body organs. Massive expansion of nanotechnologies together with production of new nanoparticles which have not yet been in contact with living organisms may pose a potential health problem. It is therefore necessary to investigate the health impact of NPs after experimental exposure. Comparison of the effect of TiO₂ and NPs Fe₃O₄ in Wistar rats at time intervals 1, 7, 14 and 28 days was performed by studying the cytotoxic effect in the isolated inflammatory cells from bronchoalveolar lavage (BAL).

METHODS

Wistar rats were intravenously (i.v.) given a suspension of NPs TiO₂ or Fe₃O₄ (coated by sodium oleate) via the tail vein. After time intervals of 1, 7, 14 and 28 days, we sacrificed the animals under anaesthesia, performed BAL and isolated the cells. The number of animals in the individual groups was 7-8. We examined the differential count of BAL cells (alveolar macrophages - AM, polymorphonuclear leukocytes - PMN, lymphocytes - Ly); viability and phagocytic activity of AM; the proportion of immature and polynuclear cells and enzymes - cathepsin D - CAT D, lactate dehydrogenase - LDH and acid phosphatase - ACP.

RESULTS

We found that TiO₂ NPs are relatively inert - without induction of inflammatory and cytotoxic response. Exposure to nanoparticles Fe₃O₄ induced - under the same experimental conditions - in comparison with the control and TiO₂ a more extensive inflammatory and cytotoxic response, albeit only at 1, 7 and 14 days after injection.

CONCLUSIONS

The results suggest that TiO₂ and Fe₃O₄ nanoparticles used in our study were transferred from the bloodstream to the respiratory tract, but this effect was not observed at 28 days after i.v. injection, probably due to their removal from the respiratory tract.

Efficient Method for the Concentration Determination of Fmoc Groups Incorporated in the Core-Shell Materials by Fmoc-Glycine

In this paper, we described the synthesis procedure of TiO₂@SiO₂ core-shell modified with 3-(aminopropyl)trimethoxysilane (APTMS). The chemical attachment of Fmoc-glycine (Fmoc-Gly-OH) at the surface of the core-shell structure was performed to determine the amount of active amino groups on the basis of the amount of Fmoc group calculation. We characterized nanostructures using various methods: transmission electron microscope (TEM), scanning electron microscopy (SEM), Fourier-transform infrared spectroscopy (FTIR), thermogravimetric analysis (TGA) and X-ray photoelectron spectroscopy (XPS) to confirm the modification effectiveness. The ultraviolet-visible spectroscopy (UV-vis) measurement was adopted for the quantitative determination of amino groups present on the TiO₂@SiO₂ core-shell surface by determination of Fmoc substitution. The nanomaterials were functionalized by Fmoc-Gly-OH and then the fluorenylmethyloxycarbonyl (Fmoc) group was cleaved using 20% (v/v) solution of piperidine in DMF. This reaction led to the formation of a dibenzofulvene-piperidine adduct enabling the estimation of free Fmoc groups by measurement the maximum absorption at 289 and 301 nm using UV-vis spectroscopy. The calculations of Fmoc loading on core-shell materials was performed using different molar absorption coefficient: 5800 and 6089 dm³ × mol^-1 × cm^-1 for λ = 289 nm and both 7800 and 8021 dm³ × mol^-1 × cm^-1 for λ = 301 nm. The obtained results indicate that amount of Fmoc groups present on TiO₂@SiO₂-(CH₂)₃-NH₂ was calculated at 6 to 9 µmol/g. Furthermore, all measurements were compared with Fmoc-Gly-OH used as the model sample.

Titanium dioxide nanoparticles exaggerate respiratory syncytial virus-induced airway epithelial barrier dysfunction

Respiratory syncytial virus (RSV) is the leading cause of lower respiratory tract infections in children worldwide. While most develop a mild, self-limiting illness, some develop severe acute lower respiratory infection and persistent airway disease. Exposure to ambient particulate matter has been linked to asthma, bronchitis, and viral infection in multiple epidemiological studies. We hypothesized that coexposure to nanoparticles worsens RSV-induced airway epithelial barrier dysfunction. Bronchial epithelial cells were incubated with titanium dioxide nanoparticles (TiO2-NP) or a combination of TiO2-NP and RSV. Structure and function of epithelial cell barrier were analyzed. Viral titer and the role of reactive oxygen species (ROS) generation were evaluated. In vivo, mice were intranasally incubated with TiO2-NP, RSV, or a combination. Lungs and bronchoalveolar lavage (BAL) fluid were harvested for analysis of airway inflammation and apical junctional complex (AJC) disruption. RSV-induced AJC disruption was amplified by TiO2-NP. Nanoparticle exposure increased viral infection in epithelial cells. TiO2-NP induced generation of ROS, and pretreatment with antioxidant, N-acetylcysteine, reversed said barrier dysfunction. In vivo, RSV-induced injury and AJC disruption were augmented in the lungs of mice given TiO2-NP. Airway inflammation was exacerbated, as evidenced by increased white blood cell infiltration into the BAL, along with exaggeration of peribronchial inflammation and AJC disruption. These data demonstrate that TiO2-NP exposure exacerbates RSV-induced AJC dysfunction and increases inflammation by mechanisms involving generation of ROS. Further studies are required to determine whether NP exposure plays a role in the health disparities of asthma and other lung diseases, and why some children experience more severe airway disease with RSV infection.

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.

COVID-19 and a novel initiative to improve safety by 3D printing personal protective equipment parts from computed tomography

BACKGROUND

Powered air-purifying respirators are in short supply and can break down with extended use. Replacement parts can become hard to acquire. The aim of this study was to create an innovative quality improvement proof of concept using rapid prototyping.

METHODS

Here we report three cases of 3D printed powered air-purifying respirator parts. 3D printing was performed on all parts using fused deposition modeling with standard polylactic acid, in the same way that presurgical models would be created. Measurements using an electronic caliper as well as CT scans were used to compare an original part to its corresponding 3D printed parts for accuracy.

RESULTS

Electronic caliper and computed tomography measurements both showed accuracy consistant with current published norms.

CONCLUSIONS

Ultimately, there will be questions surrounding intellectual property, effectiveness and potential long-term safety for these types of 3D printed parts. Future research should look into the addition of specific nanoparticles from the position of cost, efficacy, safety and improved accuracy.

Total Reflection X-ray Fluorescence spectrometry determination of titanium dioxide released from UV-protective textiles during wash

The aim of this study is to determine the release of TiO₂ from six sport garments into the wash water after 1, 2 and 10 washes. For such, Total Reflection X-ray Fluorescence (TXRF) spectrometry was employed for the study of the wash water and Scanning Electron Microscopy - Energy Dispersive Spectrometry (SEM-EDS) was used for the analysis of the textiles. Results showed that the six sport garments released between 0.106 mg/L and 0.352 mg/L after the first two washes and between 0.028 mg/L and 0.337 mg/L of Ti after ten washes. The values found for the Ti amount released in wash water, and consequently into the environment, is much less than other common sources. These results showed the potential of TXRF spectrometry in quantifying Ti in wash water, which is a hard task even for well-established methods. SEM images show that all six samples were weft knitted fabrics, with yarns of approximately 250 μm of width and fibers' width between 9 and 13 μm.

Nanomaterial integration into the scaffolding materials for nerve tissue engineering: a review

The nervous system, which consists of a complex network of millions of neurons, is one of the most highly intricate systems in the body. This complex network is responsible for the physiological and cognitive functions of the human body. Following injuries or degenerative diseases, damage to the nervous system is overwhelming because of its complexity and its limited regeneration capacity. However, neural tissue engineering currently has some capacities for repairing nerve deficits and promoting neural regeneration, with more developments in the future. Nevertheless, controlling the guidance of stem cell proliferation and differentiation is a challenging step towards this goal. Nanomaterials have the potential for the guidance of the stem cells towards the neural lineage which can overcome the pitfalls of the classical methods since they provide a unique microenvironment that facilitates cell-matrix and cell-cell interaction, and they can manipulate the cell signaling mechanisms to control stem cells' fate. In this article, the suitable cell sources and microenvironment cues for neuronal tissue engineering were examined. Afterward, the nanomaterials that impact stem cell proliferation and differentiation towards neuronal lineage were reviewed.

[Effects of titanium dioxide nanoparticles on fecal metabolome in rats after oral administration for 90 days]

OBJECTIVE

To explore the effects and related mechanisms of oral exposure titanium dioxide nanoparticles (TiO₂ NPs) for 90 days on the intestinal and the gut microbiota of rats, through fecal metabolomics.

METHODS

Twelve 4-week-old clean-grade Sprague Dawley (SD) rats were randomly de-vided into 2 groups by body weight, treated with TiO₂ NPs at dose of 0 or 50 mg/kg body weight everyday respectively for 90 days. The solution of each infection was freshly prepared and shocked fully by ultrasonic. Characterization of the particle size, crystal form, purity, and specific surface area of TiO₂ NPs was conducted. And the fresh feces of the rats were collected on the 90th day. After lyophilized and hydrophilic phase extraction, ultra performance liquid chromatography-Q-exactive orbitrap-high-resolution mass spectrometry system (UPLC-QEMS) was utilized for non-targeted determination of fecal meta-bolites. The metabolites were identified and labeled through Compound Discoverer 3.0 software, and used for subsequent metabolomics analysis. Bioinformatics analysis was carried out including unsupervised principal component analysis and supervised orthogonal projection to latent structure discriminant analysis for the differential metabolites between the two groups. The differential metabolites were followed-up for Kyoto Encyclopedia of Genes and Genomes (KEGG) pathway analysis.

RESULTS

Compared with the control group, the body weight of the rats was significantly reduced (P<0.05) in the treatment group. A total of 22 metabolites in fecal metabolomics showed significant changes. Among them, xanthine, 1-methyladenine, 3-hydroxypyridine, methionine sulfoxide, pyridoxine, 1,5-isoquinolinediol, N-acetylornithine, N-acetyl-D-galactosamine, L-citrulline, L-methionine, leucine, DL-tryptophan, L-ornithine, 4-methyl-5-thiazoleethanol, and L-glutamic acid totaled 15 metabolites increased significantly. N-acetylhistamine, D-pipecolinic acid, imidazolelactic acid, L-valine, 2,3,4,6-tetramethylpyrazine, caprolactam, and histamine totaled 7 metabolites decreased significantly. N-acetylhistamine, L-valine and methionine sulfoxide were changed more than 16 times. Analysis of KEGG pathway revealed that the two metabolic pathways arginine biosynthesis and aminoacyl-tRNA biosynthesis were significantly changed (false discover rate < 0.05, pathway impact > 0.1).

CONCLUSION

Oral exposure to TiO₂ NPs for 90 days could disrupt the metabolism of the intestine and gut microbiota, causing significant changes in metabolites and metabolic pathways which were related to inflammatory response, oxidative stress, glucose homeostasis, blood system and amino acid homeostasis in rat feces. It is suggested that the toxic effect of TiO₂ NPs on rats may be closely related to intestinal and gut microbiota metabolism.

Size Fractionation of Titania Nanoparticles in Wild Dittrichia viscosa Grown in a Native Environment

We report a size fractionation of titania (TiO₂) nanoparticles absorbed from the environment and found within wild Dittrichia viscosa plants. The nanoparticles were isolated by extraction and isolation from distinct plant organs, as well as from the corresponding rhizosphere of wild, adult plants. The collected nanoparticles were characterized by scanning transmission electron microscopy coupled with energy dispersive X-ray spectroscopy (STEM-EDS). More than 1200 TiO₂ nanoparticles were analyzed by these techniques. The results indicated the presence of TiO₂ nanoparticles with a wide range of sizes within the inspected plant organs and rhizospheres. Interestingly, a size selective process occurs during the internalization and translocation of these nanoparticles (e.g., foliar and root uptake), which favors the accumulation of mainly TiO₂ nanoparticles with diameters <50 nm in the leaves, stems, and roots. In fact, our findings indicate that among the total number of TiO₂ nanoparticles analyzed, the fraction of the particles with dimensions <50 nm were 52% of those within the rhizospheres, 88.5% of those within the roots, 90% of those within the stems, and 53% of those within the leaves. This significant difference observed in the size distribution of the TiO₂ nanoparticles among the rhizosphere and the plant organs could have impacts on the food chain and further biologicals effects that are dependent on the size of the TiO₂.

Early-onset colorectal cancer: initial clues and current views

Over the past several decades, the incidence of early-onset colorectal cancer (EOCRC; in patients <50 years old) has increased at an alarming rate. Although robust and scientifically rigorous epidemiological studies have sifted out environmental elements linked to EOCRC, our knowledge of the causes and mechanisms of this disease is far from complete. Here, we highlight potential risk factors and putative mechanisms that drive EOCRC and suggest likely areas for fruitful research. In addition, we identify inconsistencies in the evidence implicating a strong effect of increased adiposity and suggest that certain behaviours (such as diet and stress) might place nonobese and otherwise healthy people at risk of this disease. Key risk factors are reviewed, including the global westernization of diets (usually involving a high intake of red and processed meats, high-fructose corn syrup and unhealthy cooking methods), stress, antibiotics, synthetic food dyes, monosodium glutamate, titanium dioxide, and physical inactivity and/or sedentary behaviour. The gut microbiota is probably at the crossroads of these risk factors and EOCRC. The time course of the disease and the fact that relevant exposures probably occur in childhood raise important methodological issues that are also discussed.

Adipose tissue concentrations of arsenic, nickel, lead, tin, and titanium in adults from GraMo cohort in Southern Spain: An exploratory study

BACKGROUND

Adipose tissue has been acknowledged as a potential target for obesogenic pollutants, including toxic metal(loid)s. However, the presence of these chemicals in the adipose tissue has been poorly characterized.

OBJECTIVE

To examine the distributions of adipose tissue concentrations of five toxic metal(loid)s (i.e., arsenic [As], nickel [Ni], lead [Pb], tin [Sn], and titanium [Ti]) in adults, and potential socio-demographic and lifestyle factors associated with metal(loid) concentrations.

METHODS

The study population consisted of a subsample of 228 subjects from GraMo cohort in Southern Spain (N = 387). Adipose tissue samples were intra-operatively collected from adults recruited in 2003-2004 in two public hospitals, and concentrations of metal(loid)s in adipose tissue were analyzed in 2015 by High-Resolution Inductively Coupled Plasma Mass Spectrometry. Data on socio-demographic and lifestyle factors were obtained by baseline questionnaire completion. Linear and multinomial regression was used to identify factors associated with metal(loid) levels.

RESULTS

Ni, Pb, Sn, and Ti were detected in all adipose tissue samples, and As in 51% of them. Ni was the metal showing the highest median concentration (0.56 μg/g), followed by Ti (0.31 μg/g), Pb (0.08 μg/g), Sn (0.06 μg/g), and As (0.003 μg/g). Predictors of As levels included area of residence, social class, and oily fish intake; for Ni: area of residence and consumption of cheese, meat, eggs, and canned food; for Pb: vegetables intake and industrial occupation; for Sn: age, body mass index, and consumption of lean fish, eggs, and milk; and cheese intake for Ti. Some of these predictors were sex-specific, particularly those regarding dietary intake.

CONCLUSIONS

This exploratory study provides the first evidence of the occurrence of Ni, Pb, Sn, Ti, and As in adipose tissue from adult population, and highlights the potential of this tissue as a biological matrix for studying exposure levels and chronic health effects of toxic metal(loid)s.

Development of Polyelectrolyte Complex Nanoparticles-PECNs Loaded with Ampicillin by Means of Polyelectrolyte Complexation and Ultra-High Pressure Homogenization (UHPH)

This study was focused on synthesizing, characterizing and evaluating the biological potential of Polyelectrolyte Complex Nanoparticles (PECNs) loaded with the antibiotic ampicillin. For this, the PECNs were produced initially by polyelectrolytic complexation (bottom-up method) and subsequently subjected to ultra-high pressure homogenization-UHPH (top-down method). The synthetic polymeric materials corresponding to the sodium salt of poly(maleic acid-alt-octadecene) (PAM-18Na) and the chloride salt of Eudragit E-100 (EuCl) were used, where the order of polyelectrolyte complexation, the polyelectrolyte ratio and the UHPH conditions on the PECNs features were evaluated. Likewise, PECNs were physicochemically characterized through particle size, polydispersity index, zeta potential, pH and encapsulation efficiency, whereas the antimicrobial effect was evaluated by means of the broth microdilution method employing ampicillin sensitive and resistant S. aureus strains. The results showed that the classical method of polyelectrolyte complexation (bottom-up) led to obtain polymeric complexes with large particle size and high polydispersity, where the 1:1 ratio between the titrant and receptor polyelectrolyte was the most critical condition. In contrast, the UHPH technique (top-down method) proved high performance to produce uniform polymeric complexes on the nanometric scale (particle size < 200 nm and PDI < 0.3). Finally, it was found there was a moderate increase in antimicrobial activity when ampicillin was loaded into the PECNs.

MicroRNA Response and Toxicity of Potential Pathways in Human Colon Cancer Cells Exposed to Titanium Dioxide Nanoparticles

Titanium dioxide nanoparticles (TiO₂-NPs) are widely used for biomedical and food applications, the toxicity of TiO₂-NPs in vivo and in vitro has been elucidated, but the underlying cytotoxicity of TiO₂-NPs against microRNA remains largely unknown. The purpose of this study was to analyze microRNA profiling induced by TiO₂-NPs against NCM460 and HCT116 cell lines. Comparative analysis identified 34 and 24 microRNAs were significantly altered in the TiO₂-NPs treated cells at concentrations of 3 μg/mL and 30 μg/mL, respectively. Functional classification demonstrated that a large proportion of genes involved in metabolism, human disease, and environmental information process were significantly upregulated by TiO₂-NPs. Bioinformatics analysis suggested that microRNA 378 might be an early indicator of cellular response to exogenous stimuli with apoptotic signals. Furthermore, TiO₂-NPs significantly altered the expression of microRNA 378b and 378g in HCT116 and NCM460 cell lines at different concentrations from 3 to 6 μg/mL. These concentrations elicit high-sensitivity of stimuli response in colon cancer cells when exposed to the slight doses of TiO₂-NPs. Our study indicated that microRNAs 378b and 378g may play an important role in TiO₂-NPs-mediated colonic cytotoxicity, which may provide a valuable insight into the molecular mechanisms of potential risks in colitis and colon cancer.

Effects of Mixtures of Engineered Nanoparticles and Metallic Pollutants on Aquatic Organisms

In aquatic environment, engineered nanoparticles (ENPs) are present as complex mixtures with other pollutants, such as trace metals, which could result in synergism, additivity or antagonism of their combined effects. Despite the fact that the toxicity and environmental risk of the ENPs have received extensive attention in the recent years, the interactions of ENPs with other pollutants and the consequent effects on aquatic organisms represent an important challenge in (nano)ecotoxicology. The present review provides an overview of the state-of-the-art and critically discusses the existing knowledge on combined effects of mixtures of ENPs and metallic pollutants on aquatic organisms. The specific emphasis is on the adsorption of metallic pollutants on metal-containing ENPs, transformation and bioavailability of ENPs and metallic pollutants in mixtures. Antagonistic, additive and synergistic effects observed in aquatic organisms co-exposed to ENPs and metallic pollutants are discussed in the case of “particle-proof” and “particle-ingestive” organisms. This knowledge is important in developing efficient strategies for sound environmental impact assessment of mixture exposure in complex environments.

The Current Understanding of Autophagy in Nanomaterial Toxicity and Its Implementation in Safety Assessment-Related Alternative Testing Strategies

Nanotechnology has rapidly promoted the development of a new generation of industrial and commercial products; however, it has also raised some concerns about human health and safety. To evaluate the toxicity of the great diversity of nanomaterials (NMs) in the traditional manner, a tremendous number of safety assessments and a very large number of animals would be required. For this reason, it is necessary to consider the use of alternative testing strategies or methods that reduce, refine, or replace (3Rs) the use of animals for assessing the toxicity of NMs. Autophagy is considered an early indicator of NM interactions with cells and has been recently recognized as an important form of cell death in nanoparticle-induced toxicity. Impairment of autophagy is related to the accelerated pathogenesis of diseases. By using mechanism-based high-throughput screening in vitro, we can predict the NMs that may lead to the generation of disease outcomes in vivo. Thus, a tiered testing strategy is suggested that includes a set of standardized assays in relevant human cell lines followed by critical validation studies carried out in animals or whole organism models such as C. elegans (Caenorhabditis elegans), zebrafish (Danio rerio), and Drosophila (Drosophila melanogaster)for improved screening of NM safety. A thorough understanding of the mechanisms by which NMs perturb biological systems, including autophagy induction, is critical for a more comprehensive elucidation of nanotoxicity. A more profound understanding of toxicity mechanisms will also facilitate the development of prevention and intervention policies against adverse outcomes induced by NMs. The development of a tiered testing strategy for NM hazard assessment not only promotes a more widespread adoption of non-rodent or 3R principles but also makes nanotoxicology testing more ethical, relevant, and cost- and time-efficient.

Unravelling the Potential Cytotoxic Effects of Metal Oxide Nanoparticles and Metal(Loid) Mixtures on A549 Human Cell Line

Humans are typically exposed to environmental contaminants' mixtures that result in different toxicity than exposure to the individual counterparts. Yet, the toxicology of chemical mixtures has been overlooked. This work aims at assessing and comparing viability and cell cycle of A549 cells after exposure to single and binary mixtures of: titanium dioxide nanoparticles (TiO2NP) 0.75-75 mg/L; cerium oxide nanoparticles (CeO2NP) 0.0.75-10 μg/L; arsenic (As) 0.75-2.5 mg/L; and mercury (Hg) 5-100 mg/L. Viability was assessed through water-soluble tetrazolium (WST-1) and thiazolyl blue tetrazolium bromide (MTT) (24 h exposure) and clonogenic (seven-day exposure) assays. Cell cycle alterations were explored by flow cytometry. Viability was affected in a dose- and time-dependent manner. Prolonged exposure caused inhibition of cell proliferation even at low concentrations. Cell-cycle progression was affected by TiO2NP 75 mg/L, and As 0.75 and 2.5 μg/L, increasing the cell proportion at G0/G1 phase. Combined exposure of TiO2NP or CeO2NP mitigated As adverse effects, increasing the cell surviving factor, but cell cycle alterations were still observed. Only CeO2NP co-exposure reduced Hg toxicity, translated in a decrease of cells in Sub-G1. Toxicity was diminished for both NPs co-exposure compared to its toxicity alone, but a marked toxicity for the highest concentrations was observed for longer exposures. These findings prove that joint toxicity of contaminants must not be disregarded.

Design of Multifunctional Titania-Based Photocatalysts by Controlled Redox Reactions

This work aims at the preparation of multifunctional titania-based photocatalysts with inherent capabilities for thermal co-activation and stabilisation of anatase polymorph, by designing the phase composition and microstructure of rutile-silicon carbide mixture. The processing involved a conventional solid state route, including partial pre-reduction of rutile by SiC in inert Ar atmosphere, followed by post-oxidation in air. The impacts of processing conditions on the phase composition and photocatalytic activity were evaluated using Taguchi planning. The XRD studies confirmed the presence of rutile/anatase mixtures in the post-oxidised samples. The results emphasise that pre-reduction and post-oxidation temperatures are critical in defining the phase composition, while post-oxidation time is relevant for the photocatalytic performance. Microstructural studies revealed the formation of core-shell particles, which can suppress the photocatalytic activity. The highest apparent reaction rate of the photodegradation of methylene blue was observed for the sample pre-reduced in Ar at 1300 °C for 5 h and then calcined in air at 400 °C for 25 h. Though its performance was ~1.6-times lower than that for the same amount of nanostructured industrial P25 photocatalyst, it was achieved in the material possessing 2–3 times lower surface area and containing ~50 mol% of SiO₂ and SiC, thus demonstrating excellent prospects for further improvements.

TiO2 Nanomaterials Non-Controlled Contamination Could Be Hazardous for Normal Cells Located in the Field of Radiotherapy

Among nanomaterials (NMs), titanium dioxide (TiO₂) is one of the most manufactured NMs and can be found in many consumers' products such as skin care products, textiles and food (as E171 additive). Moreover, due to its most attractive property, a photoactivation upon non-ionizing UVA radiation, TiO₂ NMs is widely used as a decontaminating agent. Uncontrolled contaminations by TiO₂ NMs during their production (professional exposure) or by using products (consumer exposure) are rather frequent. So far, TiO₂ NMs cytotoxicity is still a matter of controversy depending on biological models, types of TiO₂ NMs, suspension preparation and biological endpoints. TiO₂ NMs photoactivation has been widely described for UV light radiation exposure, it could lead to reactive oxygen species production, known to be both cyto- and genotoxic on human cells. After higher photon energy exposition, such as X-rays used for radiotherapy and for medical imaging, TiO₂ NMs photoactivation still occurs. Importantly, the question of its hazard in the case of body contamination of persons receiving radiotherapy was never addressed, knowing that healthy tissues surrounding the tumor are indeed exposed. The present work focuses on the analysis of human normal bronchiolar cell response after co-exposition TiO₂ NMs (with different coatings) and ionizing radiation. Our results show a clear synergistic effect, in terms of cell viability, cell death and oxidative stress, between TiO₂ NMS and radiation.

Nanoparticles as Anti-Microbial, Anti-Inflammatory, and Remineralizing Agents in Oral Care Cosmetics: A Review of the Current Situation

Many investigations have pointed out widespread use of medical nanosystems in various domains of dentistry such as prevention, prognosis, care, tissue regeneration, and restoration. The progress of oral medicine nanosystems for individual prophylaxis is significant for ensuring bacterial symbiosis and high-quality oral health. Nanomaterials in oral cosmetics are used in toothpaste and other mouthwash to improve oral healthcare performance. These processes cover nanoparticles and nanoparticle-based materials, especially domains of application related to biofilm management in cariology and periodontology. Likewise, nanoparticles have been integrated in diverse cosmetic produces for the care of enamel remineralization and dental hypersensitivity. This review summarizes the indications and applications of several widely employed nanoparticles in oral cosmetics, and describes the potential clinical implementation of nanoparticles as anti-microbial, anti-inflammatory, and remineralizing agents in the prevention of dental caries, hypersensitivity, and periodontitis.

Analysis of the Exposure of Organisms to the Action of Nanomaterials

The rapid development of the production of materials containing metal nanoparticles and metal oxides is a potential risk to the environment. The degree of exposure of organisms to nanoparticles increases from year to year, and its effects are not fully known. This is due to the fact that the range of nanoparticle interactions on cells, tissues and the environment requires careful analysis. It is necessary to develop methods for testing the properties of nanomaterials and the mechanisms of their impact on individual cells as well as on entire organisms. The particular need to raise public awareness of the main sources of exposure to nanoparticles should also be highlighted. This paper presents the main sources and possible routes of exposure to metal nanoparticles and metal oxides. Key elements of research on the impact of nanoparticles on organisms, that is, in vitro tests, in vivo tests and methods of detection of nanoparticles in organisms, are presented.