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

Toxicity of Engineered Nanoparticles in Food: Sources, Mechanisms, Contributing Factors, and Assessment Techniques

The increasing prevalence of engineered nanoparticles (ENPs) in food systems has raised concerns about their toxicity and potential health risks. To provide a comprehensive evaluation, a structured literature search was conducted using databases such as Web of Science and PubMed, focusing on studies published in the past ten years that examine ENP exposure pathways, toxicity mechanisms, contributing factors, and risk assessment strategies. This review first explores the diverse sources of ENPs, including food additives, nanocarriers, packaging, agricultural practices, and environmental contamination. Upon ingestion, ENPs undergo complex transformations within the human gastrointestinal tract (GIT), causing oxidative stress, cellular dysfunction, inflammation, and gut microbiota dysbiosis, potentially leading to systemic toxicity in vital organs. The toxicity of ENPs is influenced by their physicochemical properties, food matrix effects, GIT conditions, and host-specific factors. This review further discusses current toxicity assessment methodologies, including in silico, in vitro, in vivo, and emerging technologies. Finally, we identify critical research gaps, such as the lack of long-term exposure studies and limited evaluations of organic ENPs. By providing a comprehensive analysis of ingested ENP toxicity, this review aims to guide safer ENP applications and mitigate potential health risks.

Challenges in laser tattoo removal: the impact of titanium dioxide on photodegradation of yellow inks

As tattoos have grown increasingly popular, there has been an increase in their removal. This is commonly achieved using laser treatments. However, certain tattoo inks are resistant to removal using laser methods because of their composition. This includes the removal of yellow pigments and tattoo inks containing titanium dioxide (TiO2). This research examined a series of yellow pigments (PY14, PY74, PY65) and tattoo inks, pre- and post-irradiation, with a QS Nd:YAG laser irradiation at 532 nm. The pigments and products were analysed using a range of techniques, including EDX-SEM, DLS, XRD and GC-MS. Results of this study indicate that the presence of TiO2 alters the laser degradation process of the pigments studied, with observable changes to particle morphologies, particle size, and evolved volatile products. In addition, some of the degradation products were identified to be potentially harmful to the human body.

Advancements in research on the precise eradication of cancer cells through nanophotocatalytic technology

The rapid development of nanotechnology has significantly advanced the application of nanophotocatalysis in the medical field, particularly for cancer therapy. Traditional cancer treatments, such as chemotherapy and radiotherapy, often cause severe side effects, including damage to healthy tissues and the development of drug resistance. In contrast, nanophotocatalytic therapy offers a promising approach by utilizing nanomaterials that generate reactive oxygen species (ROS) under light activation, allowing for precise tumor targeting and minimizing collateral damage to surrounding tissues. This review systematically explores the latest advancements in highly efficient nanophotocatalysts for cancer treatment, focusing on their toxicological profiles, underlying mechanisms for cancer cell eradication, and potential for clinical application. Recent research shows that nanophotocatalysts, such as TiO2, In2O3, and g-C3N4 composites, along with photocatalysts with high conduction band or high valence band positions, generate ROS under light irradiation, which induces oxidative stress and leads to cancer cell apoptosis or necrosis. These ROS cause cellular damage by interacting with key biological molecules such as DNA, proteins, and lipids, triggering a cascade of biochemical reactions that ultimately result in cancer cell death. Furthermore, strategies such as S-scheme heterojunctions and oxygen vacancies (OVs) have been incorporated to enhance charge separation efficiency and light absorption, resulting in increased ROS generation, which improves photocatalytic performance for cancer cell targeting. Notably, these photocatalysts exhibit low toxicity to healthy cells, making them a safe and effective treatment modality. The review also discusses the challenges associated with photocatalytic cancer therapy, including limitations in light penetration and the need for improved biocompatibility. The findings suggest that nanophotocatalytic technology holds significant potential for precision cancer therapy, paving the way for safer and more effective treatment strategies.

Protective effects of N-acetylcysteine against titanium dioxide nanoparticles-induced kidney damage in rats

The objective of this study was to evaluate the potential protective effect of N-acetylcysteine (NAC) against kidney damage induced by titanium dioxide nanoparticles (TiO2NP) through biochemical, histological, and immunohistochemical analyses. Forty rats were randomly divided into four groups of 10 animals each. Saline was administered intragastrically to control group for 14 days. In NAC group, 150 mg/kg NAC was injected intraperitoneally for 21 days. In TiO2NP group, TiO2NP at a dose of 50 mg/kg/day, dissolved in saline, was administered intragastrically for 14 days. TiO2NP + NAC group received 50 mg/kg/day TiO2NP for 14 days and 150 mg/kg NAC for 21 days, starting 7 days before TiO2NP administration. At the end of experiment, rats were anesthetized, serum samples were collected for biochemical analysis, and kidney tissue was removed for histological and immunohistochemical analyses. There was no significant change in body weight, kidney weight, or serum urea-creatinine levels between the groups. TiO2NP caused a significant increase in vacuolization and brush border loss scores in tubular cells, as well as scores for congestion and leukocyte infiltration. However, NAC supplementation significantly ameliorated these impairments. Additionally, TiO2NP significantly increased NF-kB, TNF-α, and caspase-3 immunoreactivities, as well as the number of PCNA-positive and TUNEL-positive cells. NAC treatment decreased all immunoreactivities and TUNEL-positive cells, but did not change the number of PCNA-positive cells after TiO2NP exposure. The results of the study showed that the toxic effects of TiO2NP on the kidneys, commonly encountered in daily life, can be mitigated by the anti-inflammatory and anti-apoptotic properties of NAC.

Nanotechnology-Based Therapies for Preventing Post-Surgical Adhesions

Adhesions are the body's natural response to various inflammatory causes, with surgery being the most common cause. However, the formation of postoperative adhesions can lead to significant complications, including intestinal obstruction and chronic pain. To prevent such postoperative complications associated with adhesions, developing effective strategies for adhesion prevention has been a major focus of research. Currently, several therapeutic models have been developed to achieve this objective. These include pharmaceuticals, inert polymers, functional biomaterials, and nanotherapeutics. Among the various strategies developed, nanotherapeutics, though still in its early stages, has shown promise as a potential approach. Other therapeutic models are associated with adverse side effects and complications related to their application. On the other hand, nanotherapeutic models are able to overcome the limitations of the other strategies and provide their own set of unique advantages. Hence, nanotherapeutics represents a promising area for further research. Further efforts should be made to refine existing nanotherapeutics for clinical application while also addressing associated safety and ethical concerns related to their use in medical practice. Therefore, this article aims to review the various nanotherapeutic approaches developed for the prevention of postoperative adhesions, explore their regulatory pathways, and discuss associated safety and ethical concerns.

Incidental nanoparticle characterisation in industrial settings to support risk assessment modelling

Research on nanoparticle (NP) release and potential exposure can be assessed through experimental field campaigns, laboratory simulations, and prediction models. However, risk assessment models are typically designed for manufactured NP (MNP) and have not been adapted for incidental NP (INP) properties. A notable research gap is identifying NP sources and their chemical, physical, and toxicological properties, especially in real-world settings. This work aims to provide insights into the release and physico-chemical properties of INP while contributing to improving models for INP release. INP release was evaluated through a case study in a ceramic tile firing facility, where aerosol (10 nm - 10 μm) properties were determined. The Control Banding (CB) Nanotool model was applied to test outputs based on provided input parameters. RESULTS: demonstrate the constant generation and release of INP during tile firing, with NP concentrations up to 68711/cm³ and mean diameters of 37 nm, with 95% smaller than 100 nm. Particle morphology was mostly spherical, suggesting nucleation from precursor gases as the main formation mechanism. INP chemical composition was driven by primary ceramic components, while trace elements like Ni and Ti exhibited size-dependent patterns. In vitro cell viability tests indicated low to medium cytotoxicity of PM2 aerosols, decreasing human alveolar epithelial cell viability in a concentration-dependent manner. Applying the risk model with varying input parameters revealed that the risk level (RL) based on severity scores decreased when aerosol size distribution data were used, illustrating the model's sensitivity to input variables. We conclude on the need for comprehensive experimental datasets to support risk assessment models and achieve effective risk management strategies in real-world scenarios.

Synthesis of spherical and rods-like titanium oxide nanoparticles (TiO2 NPs) and evaluation of their cytotoxicity towards colon cells in vitro

Titanium oxide nanoparticles (TiO2 NPs) are currently used as ingredients in medicines and sunscreens. Unfortunately, recent information about TiO2 NPs indicates their undesirable biological effect on colon cells. Therefore, the aim of this work was to synthesize and evaluate the physicochemical characterization of spherical (TiO2 NSs) and rods-like (TiO2 NRs) NPs, followed by assessment their cytotoxicity. For this purpose, both normal colon epithelial cells (CRL-1790) and cancerous colon cells (SW480) were used. Scanning transmission electron microscopy (STEM) showed that TiO2 NSs with a diameter of ≈10 nm and TiO2 NRs with the size of the longer axis ≈25 nm and shorter axis ≈3 nm were obtained. Based on the selected area electron diffraction (SAED) patterns, it was found that crystalline phases were obtained for both TiO2 NPs. The UV-Vis spectra showed no contamination of TiO2 NPs. Zeta potential values were 9.7 mV and 3.1 mV for NSs and NRs, respectively. Cytotoxicity of TiO2 NPs was assessed using the MTS (3-(4,5-dimethylthiazol-2-yl)-5-(3-carboxy-methoxy-phenyl)-2-(4-sulfophenyl)-2H-tetrazolium) test for various concentration of NPs. The cytotoxic effect for both TiO2 NPs was visible for concentration of 75 μg/ml (for CRL-1790) and 50 μg/ml (for SW480) and higher, and it did not depend on the shape. Moreover, both types of TiO2 NPs (in higher concentration) induce the generation of reactive oxygen species (ROS) in cells cultured with these NPs. Holotomographic microscopy studies showed increased cellular uptake of TiO2 NPs by SW480. The obtained results for the synthesized TiO2 NPs are a promising prospect for their use in biomedical application.

Cellular and In Vivo Response to Industrial, Food Grade, and Photocatalytic TiO2 Nanoparticles

We encounter titanium dioxide nanoparticles (TiO2 NPs) throughout our daily lives in the form of food coloring, cosmetics, and industrial materials. They are used on a massive industrial scale, with over 1 million metric tons in the global market. For the workers who process these materials, inhalation is a major concern. The goal of our current research is to provide a direct comparison of the three major types of TiO2 NPs (P25, E171, R101) in terms of surface characterization, cellular response, and in vivo response following introduction into the lungs of mice. In both cellular and in vivo experiments, we observe a pro-inflammatory response to the P25 TiO2 NPs that is not observed in the E171 or R101 TiO2 NPs at mass-matched concentrations. Cellular experiments measured a cytokine, TNF-α, as a marker of a pro-inflammatory response. In vivo experiments in mice measured the number of immune cells and four pro-inflammatory cytokines (IL-6, MIP-2, IP-10, and MCP-1) present in bronchoalveolar lavage fluid. A detailed physical and chemical characterization of the TiO2 NPs shows that the P25 TiO2 NPs are distinguished by smaller primary particles suggesting that samples matched by mass contain a larger number of P25 TiO2 NPs. Cellular dose-response measurements with the P25, E171, and R101 TiO2 NPs support this hypothesis showing increased TNF-α release by macrophages as a function of TiO2 NP dose. Overall, this direct comparison of the three major types of TiO2 NPs shows that the number of particles in a dose, which is dependent on the particle diameter, is a key parameter in TiO2 NP-induced inflammation.

Titanium Dioxide Nanomaterials: Progress in Synthesis and Application in Drug Delivery

Background: Recent developments in nanotechnology have provided efficient and promising methods for the treatment of diseases to achieve better therapeutic results and lower side effects. Titanium dioxide (TiO2) nanomaterials are emerging inorganic nanomaterials with excellent properties such as low toxicity and easy functionalization. TiO2 with special nanostructures can be used as delivery vehicles for drugs, genes and antigens for various therapeutic options. The exploration of TiO2-based drug delivery systems shows great promise for translating nanotechnology into clinical applications; Methods: Comprehensive data on titanium dioxide were collected from reputable online databases including PubMed, GreenMedical, Web of Science, Google Scholar, China National Knowledge Infrastructure Database, and National Intellectual Property Administration; Results: In this review, we discuss the synthesis pathways and functionalization strategies of TiO2. Recent advances of TiO2 as a drug delivery system, including sustained and controlled drug release delivery systems were introduced. Rigorous long-term systematic toxicity assessment is an extremely critical step in application to the clinic, and toxicity is still a problem that needs to be closely monitored; Conclusions: Despite the great progress made in TiO2-based smart systems, there is still a great potential for development. Future research may focus on developing dual-reaction delivery systems and single-reaction delivery systems like redox and enzyme reactions. Undertaking thorough in vivo investigations is necessary prior to initiating human clinical trials. The high versatility of these smart drug delivery systems will drive the development of novel nanomedicines for personalized treatment and diagnosis of many diseases with poor prognosis.

Nano-TiO2 regulates the MAPK (ERK, P38) pathway to promote apoptosis and inhibit proliferation of human colon cells

BACKGROUND

Nano titanium dioxides (TiO2) are widely used in drug development, food additives and packaging materials. Although several studies have demonstrated the poisonousness of TiO2 in vivo and in vitro, the underlying molecular mechanisms have not been fully revealed.

METHODS

Characterization of TiO2 by FTIR, XRD, TEM and DLS. The NCM460 cell line, representing normal colon epithelial cells, was utilized as a model to assess the impact of TiO2 nanoparticles (TiO2-NPs) on cell proliferation and apoptosis. The potential molecular mechanisms underlying its toxic effects were investigated through transcriptome analysis, RT-qPCR, and western blot experiments.

RESULTS

The particle size of the TiO2-NPs used is about 25 nm, which has typical characteristics of anatase. TiO2-NPs at a concentration of 30-60 μg/mL will cause changes in colon cell morphology, decreased proliferation ability, and increased number of apoptotic cells. TiO2-NPs at a concentration of 6 μg/mL did not significantly modify the transcriptome expression profile of colon cells; while 30 μg/mL had a significant effect, leading to up-regulation of gene expression. The differentially expressed genes predominantly modulate the MAPK signaling pathway, TNF signaling pathway, cytokine-cytokine receptor interaction, and other related pathways. Further, western blot analysis revealed that higher concentrations of TiO2-NPs (30-60 μg/mL) could up-regulate the expression of P53, P21 and Bax, while down-regulating the expression of Bcl2 by regulating the MAPK (ERK, P38) signaling pathway. Simultaneously, it also promoted the decreased in Fos protein expression and inhibited the phosphorylation of Jun and Fos.

CONCLUSION

This study demonstrates that TiO2-NPs may exert potential toxic effects on colon cells, and therefore the intake of TiO2-NPs should be strictly regulated in practical applications.

Multi-Criteria Decision-Making Approach for Pre-Synthesis Selection of the Optimal Physicochemical Properties of TiO2 Photocatalytic Nanoparticles for Biomedical and Environmental Applications

Nanomaterials are widely used in several biomedical and environmental applications, due to their ideal properties. However, the synthetic and characterization procedure requires significant costs and has a negative environmental impact. Various methods are available in order to control the pre-synthesis design of the produced materials, predicting their behavior and minimizing the series of experiments. Multi-Criteria Decision-Making is proposed in this study in order to determine the best combination of the physicochemical parameters and to define the best alternative among fifteen different samples of nanostructured titanium dioxide. In particular, the Technique for Order of Preference by Similarity to Ideal Solution (TOPSIS) method was applied to achieve a final ranking of the available alternatives by avoiding several of the trials that would follow testing the biological effect and the photocatalytic degradation of organic pollutants. Thus, this approach helps us to stay environmentally and ethically correct, saving time, money, and energy and also providing an optimization of the nanomaterials that are developed.

Systematic review of mechanistic evidence for TiO2 nanoparticle-induced lung carcinogenicity

Nano-sized titanium dioxide particles (TiO2 NPs) are a high-production volume nanomaterial widely used in the paints, cosmetics, food and photovoltaics industry. However, the potential carcinogenic effects of TiO2 NPs in the lung are still unclear despite the vast number of in vitro and in vivo studies investigating TiO2 NPs. Here, we systematically reviewed the existing in vitro and in vivo mechanistic evidence of TiO2 NP lung carcinogenicity using the ten key characteristics of carcinogens for identifying and classifying carcinogens. A total of 346 studies qualified for the quality and reliability assessment, of which 206 were considered good quality. Using a weight-of-evidence approach, these studies provided mainly moderate to high confidence for the biological endpoints regarding genotoxicity, oxidative stress and chronic inflammation. A limited number of studies investigated other endpoints important to carcinogenesis, relating to proliferation and transformation, epigenetic alterations and receptor-mediated effects. In summary, TiO2 NPs might possess the ability to induce chronic inflammation and oxidative stress, but it was challenging to compare the findings in the studies due to the wide variety of TiO2 NPs differing in their physicochemical characteristics, formulation, exposure scenarios/test systems, and experimental protocols. Given the limited number of high-quality and high-reliability studies identified within this review, there is a lack of good enough mechanistic evidence for TiO2 NP lung carcinogenicity. Future toxicology/carcinogenicity research must consider including positive controls, endotoxin testing (where necessary), statistical power analysis, and relevant biological endpoints, to improve the study quality and provide reliable data for evaluating TiO2 NP-induced lung carcinogenicity.

Exposure to Titanium Dioxide Nanoparticles Leads to Specific Disorders of Spermatid Elongation via Multiple Metabolic Pathways in Drosophila Testes

Titanium dioxide nanoparticles (TiO2 NPs) have been extensively utilized in various applications. However, the regulatory mechanism behind the reproductive toxicity induced by TiO2 NP exposure remains largely elusive. In this study, we employed a Drosophila model to assess potential testicular injuries during spermatogenesis and conducted bulk RNA-Seq analysis to elucidate the underlying mechanisms. Our results reveal that while prolonged exposure to lower concentrations of TiO2 NPs (0.45 mg/mL) for 30 days did not manifest reproductive toxicity, exposure at concentrations of 0.9 and 1.8 mg/mL significantly impaired spermatid elongation in Drosophila testes. Notably, bulk RNA-seq analysis revealed that TiO2 NP exposure affected multiple metabolic pathways including carbohydrate metabolism and cytochrome P450. Importantly, the intervention of glutathione (GSH) significantly protected against reproductive toxicity induced by TiO2 NP exposure, as it restored the number of Orb-positive spermatid clusters in Drosophila testes. Our study provides novel insights into the specific detrimental effects of TiO2 NP exposure on spermatid elongation through multiple metabolic alterations in Drosophila testes and highlights the protective role of GSH in countering this toxicity.

In Vitro Effects of Zirconia Nanoparticles: Uptake, Genotoxicity, and Mutagenicity in V-79 cells

Zirconia nanoparticles are used in various industrial and biomedical applications such as dental implants, thermal barrier sprays, and fuel cells. The interaction of nanoparticles with the environment and humans is inevitable. Despite the enormous application potential of these nanoparticles, there are still some gaps in the literature regarding potential toxicological mechanisms and the genotoxicity of zirconia nanoparticles. The lung is one of the main exposure routes to nanomaterials; therefore, the present study was designed to determine the genotoxic and mutagenic effect of zirconia NPs in V-79 lung cells. Zirconia nanoparticles showed significant internalization in cells at 100 μg/mL and 150 μg/mL concentrations. Zirconia nanoparticles showed low cytotoxicity and were found to generate ROS in V-79 cells. In alkaline comet assay, zirconia nanoparticles (10 μg/mL, 50 μg/mL, and 100 μg/mL) exposed cells exhibited significant DNA strand breaks, while the neutral comet assay, which was used for double-strand break assessment, only revealed significant damage at 100 μg/mL. Chromosomal aberration induced by zirconia nanoparticles mainly resulted in the generation of gaps, few fragments, and breaks which signifies the low clastogenic activity of these nanoparticles in the V-79 cell line. In MN assay, zirconia nanoparticles resulted in no significant micronuclei induction at any given concentration. In the HPRT mutation assay, the particle shows a dose-dependent increase in the mutant frequency. It is evident from the result that zirconia nanoparticles cause dose-dependent cytotoxicity and genotoxicity, but still, more studies are needed to evaluate the clastogenic potential and the possible mechanism involved.

Development of a protocol of isolation of nanoparticles from patients' broncho-alveolar lavages for their in vitro toxicity assessment

To investigate potential correlations between human exposure to inhaled particles and pathological effects, the biological monitoring of nanoparticles in broncho-alveolar lavages (BAL) from patients has been proposed. To better understand the underlying mechanisms of toxicity, we propose to couple this biomonitoring of nanoparticles to their in vitro toxicity assessment. However, BAL obtained from regular clinical practice are conditioned with sodium hypochlorite solution (in a 50% v/v ratio), which is toxic to cells. The aim of this study was to develop a protocol to neutralize sodium hypochlorite, allowing to properly investigate the toxicity of the nanoparticles BAL contain. We first tried to neutralize chemically the sodium hypochlorite using H2O2, ascorbic acid or sodium ascorbate but this approach was unsuccessful. In addition, standard toxicology assays (MTT, LDH) could not be used because of interference with neutralizing solutions. We thus changed strategy and used ultracentrifugation to isolate nanoparticles from the sodium hypochlorite solution, with satisfactory extraction yields (88 to 100%). We then incubated the extracted nanoparticles with macrophages from the RAW264.7 cell line and assessed the cell viability and pro-inflammatory response. This study can be used as a proof-of-concept for further study of the biological impact of nanoparticles. This approach paves the way for studies aiming at a better understanding of the aetiology of some idiopathic diseases and underlying mechanisms.

Titanium Dioxide (TiO2) Nanoparticle Toxicity in a Caenorhabditis elegans Model

Titanium dioxide is a compound that is used in the food, cosmetic, and paint industries; however, it is still toxic to humans and the environment. This study determined the toxicities of titanium dioxide nanoparticles (TiO2 NPs) in a Caenorhabditis elegans (C. elegans) model. The effects of commercially available (C-TiO2) and synthetically (S-TiO2) prepared TiO2 NP solutions on lethality, lifespan, growth, reproduction, locomotion, and gene expression were studied in C. elegans. Exposure to TiO2 NPs (0.0, 0.01, 0.1, 1.0, and 10 mg/L) did not result in any change to the survival rate or body length of the nematodes, regardless of the concentration. However, there was a decrease in the reproduction (brood size) and locomotion (body bending and head thrashing) of the nematodes as the TiO2 NP concentration increased. The longevity of the nematodes was shortened following TiO2 NP exposure. The gene expression of sod-1, sod-3, ctl-1, ctl-2, cyp35A2, mlt-1, and mlt-2 in the nematodes showed that there was an overexpression of all genes when the worms were exposed to 1 mg/L C-TiO2 or 10 mg/L S-TiO2. It was therefore concluded that compared with S-TiO2, C-TiO2 possibly causes more toxicity or genotoxicity in the C. elegans model.

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.

Synthesis and Characterization of Rutile TiO2 Nanoparticles for the Toxicological Effect on the H9c2 Cell Line from Rats

The widespread use of titanium dioxide (TiO₂) has raised concerns about potential health risks associated with its cytotoxicity in the cardiovascular system. To evaluate the cytotoxicity of TiO₂ particles, the H9c2 rat cardiomyoblasts were used as a biological model, and their toxicological susceptibility to TiO₂-anatase and TiO₂-rutile particles was studied in vitro. The study examined dose and time exposure responses. The cell viability was evaluated based on metabolic inhibition and membrane integrity loss. The results revealed that both TiO₂-anatase and TiO₂-rutile particles induced similar levels of cytotoxicity at the inhibition concentrations IC₂₅ (1.4-4.4 μg/cm²) and IC₅₀ (7.2-9.3 μg/cm²). However, at more significant concentrations, TiO₂-rutile appeared to be more cytotoxic than TiO₂-anatase at 24 h. The study found that the TiO₂ particles induced apoptosis events, but necrosis was not observed at any of the concentrations of particles used. The study considered the effects of microstructural properties, crystalline phase, and particle size in determining the capability of TiO₂ particles to induce cytotoxicity in H9c2 cardiomyoblasts. The microstress in TiO₂ particles was assessed using powder X-ray diffraction through Williamson-Hall and Warren-Averbach analysis. The analysis estimated the apparent crystallite domain and microstrain of TiO₂-anatase to be 29 nm (ε = 1.03%) and TiO₂-rutile to be 21 nm (ε = 0.53%), respectively. Raman spectroscopy, N₂ adsorption isotherms, and dynamic light scattering were used to identify the presence of pure crystalline phases (>99.9%), comparative surface areas (10 m²/g), and ζ-potential values (-24 mV). The difference in the properties of TiO₂ particles made it difficult to attribute the cytotoxicity solely to one variable.

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.

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.

Experimental and Computational Nanotoxicology-Complementary Approaches for Nanomaterial Hazard Assessment

The growing development and applications of nanomaterials lead to an increasing release of these materials in the environment. The adverse effects they may elicit on ecosystems or human health are not always fully characterized. Such potential toxicity must be carefully assessed with the underlying mechanisms elucidated. To that purpose, different approaches can be used. First, experimental toxicology consisting of conducting in vitro or in vivo experiments (including clinical studies) can be used to evaluate the nanomaterial hazard. It can rely on variable models (more or less complex), allowing the investigation of different biological endpoints. The respective advantages and limitations of in vitro and in vivo models are discussed as well as some issues associated with experimental nanotoxicology. Perspectives of future developments in the field are also proposed. Second, computational nanotoxicology, i.e., in silico approaches, can be used to predict nanomaterial toxicity. In this context, we describe the general principles, advantages, and limitations especially of quantitative structure–activity relationship (QSAR) models and grouping/read-across approaches. The aim of this review is to provide an overview of these different approaches based on examples and highlight their complementarity.

Recent Advances in the Gastrointestinal Fate of Organic and Inorganic Nanoparticles in Foods

Inorganic or organic nanoparticles are often incorporated into foods to enhance their quality, stability, nutrition, or safety. When they pass through the gastrointestinal environment, the properties of these nanoparticles are altered, which impacts their biological effects and potential toxicity. Consequently, there is a need to understand how different kinds of nanoparticles behave within the gastrointestinal tract. In this article, the current understanding of the gastrointestinal fate of nanoparticles in foods is reviewed. Initially, the fundamental physicochemical and structural properties of nanoparticles are discussed, including their compositions, sizes, shapes, and surface chemistries. Then, the impact of food matrix effects and gastrointestinal environments on the fate of ingested nanoparticles is discussed. In particular, the influence of nanoparticle properties on food digestion and nutraceutical bioavailability is highlighted. Finally, future research directions are highlighted that will enable the successful utilization of nanotechnology in foods while also ensuring they are safe.

A Co-Culture Model of the Human Respiratory Tract to Discriminate the Toxicological Profile of Cationic Nanoparticles According to Their Surface Charge Density

This study aimed at discriminating with sensitivity the toxicological effects of carbon dots (CDs) with various zeta potential (ζ) and charge density (Qek) in different cellular models of the human respiratory tract. One anionic and three cationic CDs were synthetized as follows: CD-COOH (ζ = -43.3 mV); CD-PEI600 (Qek = 4.70 µmol/mg; ζ = +31.8 mV); CD-PEHA (Qek = 3.30 µmol/mg; ζ = +29.2 mV) and CD-DMEDA (Qek = 0.01 µmol/mg; ζ = +11.1 mV). Epithelial cells (A549) and macrophages (THP-1) were seeded alone or as co-cultures with different A549:THP-1 ratios. The obtained models were characterized, and multiple biological responses evoked by CDs were assessed in the mono-cultures and the best co-culture model. With 14% macrophages, the 2:1 ratio co-culture best mimicked the in vivo conditions and responded to lipopolysaccharides. The anionic CD did not induce any effect in the mono-cultures nor in the co-culture. Among the cationic CDs, the one with the highest charge density (CD-PEI600) induced the most pronounced responses whatever the culture model. The cationic CDs of low charge density (CD-PEHA and CD-DMEDA) evoked similar responses in the mono-cultures, whereas in the co-culture, the three cationic CDs ranked according to their charge density (CD-PEI600 > CD-PEHA > CD-DMEDA), when taking into account their inflammatory effect. Thus, the co-culture system developed in this study appears to be a sensitive model for finely discriminating the toxicological profile of cationic nanoparticles differing by the density of their surface charges.

Impact of montmorillonite clay on the homo- and heteroaggregation of titanium dioxide nanoparticles (nTiO2) in synthetic and natural waters

The homoaggregation of titanium dioxide nanoparticles (nTiO₂) and their heteroaggregation with ubiquitous natural clay colloids are crucial processes affecting the environmental transport and fate of nTiO₂, whereas the latter has received less attention. In this study, the effects of pH, electrolytes, natural organic matter (NOM), and montmorillonite on the homo- and heteroaggregation of nTiO₂ were systematically investigated. The isoelectric point of bare nTiO₂ was 6.98, whereas TiO₂-montmorillonite mixtures remained negative charged due to the reduced particle surface potential by heteroaggregation. Homoaggregation of nTiO₂ was mainly affected by anions, whereas heteroaggregation in TiO₂-montmorillonite mixtures was mainly affected by cations. Heteroaggregation between nTiO₂ and montmorillonite involved the adsorption of CC/CH. Intensive aggregation of nTiO₂ was observed with 4 mg/L montmorillonite, whereas with 20 mg/L montmorillonite, the aggregation was significantly inhibited by the over-coverage of montmorillonite. NOM was attached to the surface of nTiO₂ with the adsorption of functional groups involving CC/CH and OCO. The addition of NOM effectively reduced the homo- and heteroaggregation of nTiO₂, and the stabilizing effect was enhanced with the increased molecular weight and aromatic/aliphatic fraction in NOM. Besides electrostatic repulsion, steric repulsion could also be one of the main stabilization mechanisms of NOM. With Ca²⁺ in the solutions, the stabilizing effect of NOM was significantly weakened through cation bridging. The addition of montmorillonite could facilitate the aggregation of nTiO₂ in the presence of NOM. The homo- and heteroaggregation of nTiO₂ were also observed in 7 different types of natural waters. Homoaggregation predominated in waters with high ionic strength and low NOM contents (seawater and groundwater), whereas heteroaggregation predominated in surface freshwater and wastewater systems. The results reflect the instability of nTiO₂ in natural aquatic environments and the potential risk they pose to benthic organisms.

Differential response of immobile (pneumocytes) and mobile (monocytes) barriers against 2 types of metal oxide nanoparticles

BACKGROUND

Inhaled nanoparticles (NPs) challenges mobile and immobile barriers in the respiratory tract, which can be represented by type II pneumocytes (immobile) and monocytes (mobile) but what is more important for biological effects, the cell linage, or the type of nanoparticle? Here, we addressed these questions and we demonstrated that the type of NPs exerts a higher influence on biological effects, but cell linages also respond differently against similar type of NPs.

DESIGN

Type II pneumocytes and monocytes were exposed to tin dioxide (SnO₂) NPs and titanium dioxide (TiO₂) NPs (1, 10 and 50 μg/cm²) for 24 h and cell viability, ultrastructure, cell granularity, molecular spectra of lipids, proteins and nucleic acids and cytoskeleton architecture were evaluated.

RESULTS

SnO₂ NPs and TiO₂ NPs are metal oxides with similar physicochemical properties. However, in the absence of cytotoxicity, SnO₂ NPs uptake was low in monocytes and higher in type II pneumocytes, while TiO₂ NPs were highly internalized by both types of cells. Monocytes exposed to both types of NPs displayed higher number of alterations in the molecular patterns of proteins and nuclei acids analyzed by Fourier-transform infrared spectroscopy (FTIR) than type II pneumocytes. In addition, cells exposed to TiO₂ NPs showed more displacements in FTIR spectra of biomolecules than cells exposed to SnO₂ NPs. Regarding cell architecture, microtubules were stable in type II pneumocytes exposed to both types of NPs but actin filaments displayed a higher number of alterations in type II pneumocytes and monocytes exposed to SnO₂ NPs and TiO₂ NPs. NPs exposure induced the formation of large vacuoles only in monocytes, which were not seen in type II pneumocytes.

CONCLUSIONS

Most of the cellular effects are influenced by the NPs exposure rather than by the cell type. However, mobile, and immobile barriers in the respiratory tract displayed differential response against SnO₂ NPs and TiO₂ NPs in absence of cytotoxicity, in which monocytes were more susceptible than type II pneumocytes to NPs exposure.

Plasmon-Enhanced Antibacterial Activity of Chiral Gold Nanoparticles and In Vivo Therapeutic Effect

d-cysteine (d-cys) has been demonstrated to possess an extraordinary antibacterial activity because of its unique steric configuration. However, inefficient antibacterial properties seriously hinder its wide applications. Here, cysteine-functionalized gold nanoparticles (d-/l-Au NPs) were prepared by loading d-/l-cysteine on the surface of gold nanoparticles for the effective inhibition of Escherichia coli (E. coli) in vitro and in vivo, and the effects on the intestinal microflora in mice were explored during the treatment of E. coli infection in the gut. We found that the antibacterial activity of d-/l-Au NPs was more than 2-3 times higher than pure d-cysteine, l-cysteine and Au NPs. Compared with l-Au NPs, d-Au NPs showed the stronger antibacterial activity, which was related to its unique steric configuration. Chiral Au NPs showed stronger destructive effects on cell membrane compared to other groups, which further leads to the leakage of the cytoplasm and bacterial cell death. The in vivo antibacterial experiment illustrated that d-Au NPs displayed impressive antibacterial activity in the treatment of E. coli-infected mice comparable to kanamycin, whereas they could not affect the balance of intestinal microflora. This work is of great significance in the development of an effective chiral antibacterial agent.

Impact of Differentiated Macrophage-Like Cells on the Transcriptional Toxicity Profile of CuO Nanoparticles in Co-Cultured Lung Epithelial Cells

To mimic more realistic lung tissue conditions, co-cultures of epithelial and immune cells are one comparatively easy-to-use option. To reveal the impact of immune cells on the mode of action (MoA) of CuO nanoparticles (NP) on epithelial cells, A549 cells as a model for epithelial cells have been cultured with or without differentiated THP-1 cells, as a model for macrophages. After 24 h of submerged incubation, cytotoxicity and transcriptional toxicity profiles were obtained and compared between the cell culture systems. Dose-dependent cytotoxicity was apparent starting from 8.0 µg/cm² CuO NP. With regard to gene expression profiles, no differences between the cell models were observed concerning metal homeostasis, oxidative stress, and DNA damage, confirming the known MoA of CuO NP, i.e., endocytotic particle uptake, intracellular particle dissolution within lysosomes with subsequent metal ion deliberation, increased oxidative stress, and genotoxicity. However, applying a co-culture of epithelial and macrophage-like cells, CuO NP additionally provoked a pro-inflammatory response involving NLRP3 inflammasome and pro-inflammatory transcription factor activation. This study demonstrates that the application of this easy-to-use advanced in vitro model is able to extend the detection of cellular effects provoked by nanomaterials by an immunological response and emphasizes the use of such models to address a more comprehensive MoA.

The Challenges of 21st Century Neurotoxicology: The Case of Neurotoxicology Applied to Nanomaterials

After a short background discussing engineered nanomaterials (ENMs) and their physicochemical properties and applications, the present perspective paper highlights the main specific points that need to be considered when examining the question of neurotoxicity of nanomaterials. It underlines the necessity to integrate parameters, specific tools, and tests from multiple sources that make neurotoxicology when applied to nanomaterials particularly complex. Bringing together the knowledge of multiple disciplines e.g., nanotoxicology to neurotoxicology, is necessary to build integrated neurotoxicology for the third decade of the 21st Century. This article focuses on the greatest challenges and opportunities offered by this specific field. It highlights the scientific, methodological, political, regulatory, and educational issues. Scientific and methodological challenges include the determination of ENMs physicochemical parameters, the lack of information about protein corona modes of action, target organs, and cells and dose– response functions of ENMs. The need of standardization of data collection and harmonization of dedicated neurotoxicological protocols are also addressed. This article highlights how to address those challenges through innovative methods and tools, and our work also ventures to sketch the first list of substances that should be urgently prioritized for human modern neurotoxicology. Finally, political support with dedicated funding at the national and international levels must also be used to engage the communities concerned to set up dedicated educational program on this novel field.

Short Preirradiation of TiO2 Nanoparticles Increases Cytotoxicity on Human Lung Coculture System

Anatase titanium dioxide nanoparticles (TiO₂ NPs) are used in a large range of industrial applications mainly due to their photocatalytic properties. Before entering the lung, virtually all TiO₂ NPs are exposed to some UV light, and lung toxicity of TiO₂ NPs might be influenced by photoexcitation that is known to alter TiO₂ surface properties. Although the TiO₂ NPs toxicity has been extensively investigated, limited data are available regarding the toxicity of TiO₂ NPs that have been pre-exposed to UV light, and their impact on humans remains unknown. In this study, five types of TiO₂NPs with tailored physicochemical features were characterized and irradiated by UV for 30 min. Following irradiation, cytotoxicity, pro-inflammatory response, and oxidative stress on a human lung coculture system (A549 epithelial cells and macrophages differentiated from THP-1 cells) were assessed. The surface charge of all samples was less negative after UV irradiation of TiO₂ NPs, and the average aggregate size was slightly increased. A higher cytotoxic effect was observed for preirradiated TiO₂ NPs compared to nonirradiated samples. Preirradiation of TiO₂ NPs had no significant impact on the pro-inflammatory response and oxidative stress as shown by a similar production of IL-8, TNF-α, and reactive oxygen species.

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.

Quadruple abnormal protein aggregates in brainstem pathology and exogenous metal-rich magnetic nanoparticles (and engineered Ti-rich nanorods). The substantia nigrae is a very early target in young urbanites and the gastrointestinal tract a key brainstem portal

Fine particulate air pollution (PM_2.5) exposures are linked with Alzheimer's and Parkinson's diseases (AD,PD). AD and PD neuropathological hallmarks are documented in children and young adults exposed lifelong to Metropolitan Mexico City air pollution; together with high frontal metal concentrations (especially iron)-rich nanoparticles (NP), matching air pollution combustion- and friction-derived particles. Here, we identify aberrant hyperphosphorylated tau, ɑ synuclein and TDP-43 in the brainstem of 186 Mexico City 27.29 ± 11.8y old residents. Critically, substantia nigrae (SN) pathology seen in mitochondria, endoplasmic reticulum and neuromelanin (NM) is co-associated with the abundant presence of exogenous, Fe-, Al- and Ti-rich NPs.The SN exhibits early and progressive neurovascular unit damage and mitochondria and NM are associated with metal-rich NPs including exogenous engineered Ti-rich nanorods, also identified in neuroenteric neurons. Such reactive, cytotoxic and magnetic NPs may act as catalysts for reactive oxygen species formation, altered cell signaling, and protein misfolding, aggregation and fibril formation. Hence, pervasive, airborne and environmental, metal-rich and magnetic nanoparticles may be a common denominator for quadruple misfolded protein neurodegenerative pathologies affecting urbanites from earliest childhood. The substantia nigrae is a very early target and the gastrointestinal tract (and the neuroenteric system) key brainstem portals. The ultimate neural damage and neuropathology (Alzheimer's, Parkinson's and TDP-43 pathology included) could depend on NP characteristics and the differential access and targets achieved via their portals of entry. Thus where you live, what air pollutants you are exposed to, what you are inhaling and swallowing from the air you breathe,what you eat, how you travel, and your occupational longlife history are key. Control of NP sources becomes critical.