Role of the crystalline form of titanium dioxide nanoparticles: Rutile, and not anatase, induces toxic effects in Balb/3T3 mouse fibroblasts

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

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

Engineered Mesenchymal Stem Cells as Treatment for Cancers: Opportunities, Clinical Applications and Challenges

The insufficient and unspecific target of classical chemotherapies often leads to therapy resistance and cancer recurrence. Over the past decades, discoveries about mesenchymal stem cell (MSC) biology have provided new potential approaches to improve cancer therapy. Researchers have utilised the multipotent, regenerative and immunosuppressive qualities of MSCs and tropisms towards inflammatory, hypoxic and malignant sites in various therapeutic applications. Although MSC-based therapies have generally been demonstrated safe, their effectiveness remains limited when these cells are used alone. However, through genetic engineering, researchers have proven that MSCs can be modified to have specialised delivery roles to increase their therapeutic efficacy in cancer treatment. They can be made to overexpress therapeutic proteins through viral or non-viral genetic modification, which enhances their innate properties. Nevertheless, these engineering strategies must be optimised to increase therapeutic efficacy and targeting effectiveness while minimising any loss of MSC function. This review underscores the cutting-edge methods for engineering MSCs, discusses their promise and the difficulties in translating them into clinical settings, and offers some prospective suggestions for the future on achieving their full therapeutic potential.

Ultrasound-Based Micro-/Nanosystems for Biomedical Applications

Due to the intrinsic non-invasive nature, cost-effectiveness, high safety, and real-time capabilities, besides diagnostic imaging, ultrasound as a typical mechanical wave has been extensively developed as a physical tool for versatile biomedical applications. Especially, the prosperity of nanotechnology and nanomedicine invigorates the landscape of ultrasound-based medicine. The unprecedented surge in research enthusiasm and dedicated efforts have led to a mass of multifunctional micro-/nanosystems being applied in ultrasound biomedicine, facilitating precise diagnosis, effective treatment, and personalized theranostics. The effective deployment of versatile ultrasound-based micro-/nanosystems in biomedical applications is rooted in a profound understanding of the relationship among composition, structure, property, bioactivity, application, and performance. In this comprehensive review, we elaborate on the general principles regarding the design, synthesis, functionalization, and optimization of ultrasound-based micro-/nanosystems for abundant biomedical applications. In particular, recent advancements in ultrasound-based micro-/nanosystems for diagnostic imaging are meticulously summarized. Furthermore, we systematically elucidate state-of-the-art studies concerning recent progress in ultrasound-based micro-/nanosystems for therapeutic applications targeting various pathological abnormalities including cancer, bacterial infection, brain diseases, cardiovascular diseases, and metabolic diseases. Finally, we conclude and provide an outlook on this research field with an in-depth discussion of the challenges faced and future developments for further extensive clinical translation and application.

A review on transition metal oxides in catalysis

Transition Metal Oxides (TMOs) have drawn significant attention due to their diverse range of properties and applications. The partially filled d orbitals of the transition metal ions, with highly electronegative oxygen atoms, give rise to unique electronic structures that lead to multiple applications due to their magnetic, optical, and structural properties. These properties have a direct influence on chemical reactions that enable tailoring materials for specific applications in catalysis, such as electrocatalysis and photocatalysis. While the potential of TMOs is promising, their development for enhanced functional properties poses numerous challenges. Among these challenges, identifying the appropriate synthesis processes and employing optimal characterization techniques are crucial. In this comprehensive review, an overview of recent trends and challenges in the synthesis and characterization of highly functional TMOs as well as ceramics will be covered with emphasis on catalytic applications. Mesoporous materials play a key role in augmenting their functionality for various applications and will be covered. Ab-initio modeling aspects for the design and development of novel TMO will be also discussed.

In vitro cell-transforming potential of secondary polyethylene terephthalate and polylactic acid nanoplastics

Continuous exposure to plastic pollutants may have serious consequences on human health. However, most toxicity assessments focus on non-environmentally relevant particles and rarely investigate long-term effects such as cancer induction. The present study assessed the carcinogenic potential of two secondary nanoplastics: polyethylene terephthalate (PET) particles generated from plastic bottles, and a biodegradable polylactic acid material, as respective examples of environmentally existing particles and new bioplastics. Pristine polystyrene nanoplastics were also included for comparison. A broad concentration range (6.25-200 μg/mL) of each nanoplastic was tested in both the initiation and promotion conditions of the regulatory assessment-accepted in vitro Bhas 42 cell transformation assay. Parallel cultures allowed confirmation of the efficient cellular internalisation of the three nanoplastics. Cell growth was enhanced by polystyrene in the initiation assay, and by PET in both conditions. Moreover, the number of transformed foci was significantly increased only by the highest PET concentration in the promotion assay, which also showed dose-dependency, indicating that nano PET can act as a non-genotoxic tumour promotor. Together, these findings support the carcinogenic risk assessment of nanoplastics and raise concerns regarding whether real-life co-exposure of PET nanoplastics and other environmental pollutants may result in synergistic transformation capacities.

Surface-Mediated Modulation of Different Biological Responses on Anatase-Coated Titanium

Various surface modification strategies are being developed to endow dental titanium implant surfaces with micro- and nano-structures to improve their biocompatibility, and first of all their osseointegration. These modifications have the potential to address clinical concerns by stimulating different biological processes. This study aims to evaluate the biological responses of ananatase-modified blasted/etched titanium (SLA-anatase) surfaces compared to blasted/acid etched (SLA) and machined titanium surfaces. Using unipolar pulsed direct current (DC) sputtering, a nanocrystalline anatase layer was fabricated. In vitro experiments have shown that SLA-anatase discs can effectively promote osteoblast adhesion and proliferation, which are regarded as important features of a successful dental implant with bone contact. Furthermore, anatase surface modification has been shown to partially enhance osteoblast mineralization in vitro, while not significantly affecting bacterial colonization. Consequently, the recently created anatase coating holds significant potential as a promising candidate for future advancements in dental implant surface modification for improving the initial stages of osseointegration.

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

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

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

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

The cell transformation assay to assess potential carcinogenic properties of nanoparticles

Nanoparticles (NPs) are present in many daily life products with particular physical-chemical properties (size, density, porosity, geometry …) giving very interesting technological properties. Their use is continuously growing and NPs represent a new challenge in terms of risk assessment, consumers being multi-exposed. Toxic effects have already been identified such as oxidative stress, genotoxicity, inflammatory effects, and immune reactions, some of which are leading to carcinogenesis. Cancer is a complex phenomenon implying multiple modes of action and key events, and prevention strategies in cancer include a proper assessment of the properties of NPs. Therefore, introduction of new agents like NPs into the market creates fresh regulatory challenges for an adequate safety evaluation and requires new tools. The Cell Transformation Assay (CTA) is an in vitro test able of highlighting key events of characteristic phases in the cancer process, initiation and promotion. This review presents the development of this test and its use with NPs. The article underlines also the critical issues to address for assessing NPs carcinogenic properties and approaches for improving its relevance.

Structural parameters of nanoparticles affecting their toxicity for biomedical applications: a review

Rapidly growing interest in using nanoparticles (NPs) for biomedical applications has increased concerns about their safety and toxicity. In comparison with bulk materials, NPs are more chemically active and toxic due to the greater surface area and small size. Understanding the NPs' mechanism of toxicity, together with the factors influencing their behavior in biological environments, can help researchers to design NPs with reduced side effects and improved performance. After overviewing the classification and properties of NPs, this review article discusses their biomedical applications in molecular imaging and cell therapy, gene transfer, tissue engineering, targeted drug delivery, Anti-SARS-CoV-2 vaccines, cancer treatment, wound healing, and anti-bacterial applications. There are different mechanisms of toxicity of NPs, and their toxicity and behaviors depend on various factors, which are elaborated on in this article. More specifically, the mechanism of toxicity and their interactions with living components are discussed by considering the impact of different physiochemical parameters such as size, shape, structure, agglomeration state, surface charge, wettability, dose, and substance type. The toxicity of polymeric, silica-based, carbon-based, and metallic-based NPs (including plasmonic alloy NPs) have been considered separately.

TiO2 Nanoparticles and Their Effects on Eukaryotic Cells: A Double-Edged Sword

Nanoparticulate TiO₂ (TiO₂ NPs) is a widely used material, whose potential toxicity towards eukaryotic cells has been addressed by multiple studies. TiO₂ NPs are considered toxic due to their production of reactive oxygen species (ROS), which can, among others, lead to cellular damage, inflammatory responses, and differences in gene expression. TiO₂ NPs exhibited toxicity in multiple organs in animals, generating potential health risks also in humans, such as developing tumors or progress of preexisting cancer processes. On the other hand, the capability of TiO₂ NPs to induce cell death has found application in photodynamic therapy of cancers. In aquatic environments, much has been done in understanding the impact of TiO₂ on bivalves, in which an effect on hemocytes, among others, is reported. Adversities are also reported from other aquatic organisms, including primary producers. These are affected also on land and though some potential benefit might exist when it comes to agricultural plants, TiO₂ can also lead to cellular damage and should be considered when it comes to transfer along the food chain towards human consumers. In general, much work still needs to be done to unravel the delicate balance between beneficial and detrimental effects of TiO₂ NPs on eukaryotic cells.

Polyglycerol Functionalized 10 B Enriched Boron Carbide Nanoparticle as an Effective Bimodal Anticancer Nanosensitizer for Boron Neutron Capture and Photothermal Therapies

Boron neutron capture therapy (BNCT) is a non-invasive cancer treatment with little adverse effect utilizing nuclear fission of ¹⁰ B upon neutron irradiation. While neutron source has been developed from a nuclear reactor to a compact accelerator, only two kinds of drugs, boronophenylalanine and sodium borocaptate, have been clinically used for decades despite their low tumor specificity and/or retentivity. To overcome these challenges, various boron-containing nanomaterials, or "nanosensitizers", have been designed based on micelles, (bio)polymers and inorganic nanoparticles. Among them, inorganic nanoparticles such as boron carbide can include a much higher ¹⁰ B content, but successful in vivo applications are very limited. Additionally, recent reports on the photothermal effect of boron carbide are motivating for the addition of another modality of photothermal therapy. In this study, ¹⁰ B enriched boron carbide (¹⁰ B₄ C) nanoparticle is functionalized with polyglycerol (PG), giving ¹⁰ B₄ C-PG with enough dispersibility in a physiological environment. Pharmacokinetic experiments show that ¹⁰ B₄ C-PG fulfills the following three requirements for BNCT; 1) low intrinsic toxicity, 2) ¹⁰ B in tumor/tumor tissue (wt/wt) ≥ 20 ppm, and 3) ¹⁰ B concentrations in tumor/blood ≥ 3. In vivo study reveals that neutron irradiation after intravenous administration of ¹⁰ B₄ C-PG suppresses cancer growth significantly and eradicates cancer with the help of near-infrared light irradiation.

Effects of Particle Size and Surface Charge on Mutagenicity and Chicken Embryonic Toxicity of New Silver Nanoclusters

Though there are many toxicological studies on metal nanoparticles (NPs), it remains difficult to explain discrepancies observed between studies, largely due to the lack of positive controls and disconnection between physicochemical properties of nanomaterials with their toxicities at feasible exposures in a specified test system. In this study, we investigated effects of particle size and surface charge on in vitro mutagenic response and in vivo embryonic toxicity for newly synthesized silver nanoclusters (AgNCs) at human or environmental relevant exposure and compared the new findings with one of the most common nanoscale particles, titanium dioxide NPs (TiO₂ NPs as a positive control). We hypothesized that the interaction of the test system and physicochemical properties of nanomaterials are critical in determining their toxicities at concentrations relevant with human or environmental exposures. We assessed the mutagenicity of the AgNCs (around 2 nm) and two sizes of TiO₂ NPs (i.e., small: 5-15 nm, big: 30-50 nm) using a Salmonella reverse mutation assay (Ames test). The smallest size of AgNCs showed the highest mutagenic activity with the Salmonella strain TA100 in the absence and presence of the S9 mixture, because the AgNCs maintained the nano-size scale in the Ames test, compared with two other NPs. For TiO₂ NPs, the size effect was interfered by the agglomeration of TiO₂ NPs in media and the generation of oxidative stress from the NPs. The embryonic toxicity and the liver oxidative stress were evaluated using a chicken embryo model at three doses (0.03, 0.33, and 3.3 μg/g egg), with adverse effects on chicken embryonic development in both sizes of TiO₂ NPs. The non-monotonic response was determined for developmental toxicity for the tested NPs. Our data on AgNCs was different from previous findings on AgNPs. The chicken embryo results showed some size dependency of nanomaterials, but they were more well correlated with lipid peroxidation (malondialdehyde) in chicken fetal livers. A different level of agglomeration of TiO₂ NPs and AgNCs was observed in the assay media of Ames and chicken embryo tests. These results suggest that the test nanotoxicities are greatly impacted by the experimental conditions and the nanoparticle's size and surface charge.

Metallic nanoparticle contamination from environmental atmospheric particulate matter in the last slab of the trophic chain: Nanocrystallography, subcellular localization and toxicity effects

Atmospheric particulate material (PM) from mining and steel industries comprises several metallic contaminants. PM₁₀ samples collected in a Brazilian region with a recognized influence of the steel and iron pelletizing industries were used to investigate metallic nanoparticle incorporation into human fibroblast cells (MRC-5). MRC-5 cells were exposed to 0 (control, ultrapure water), 2.5, 5, 10, 20 and 40 μg PM₁₀ mL^-1, for 24 h. Cytotoxic and genotoxic dose-response effects were observed on lysosome and DNA structure, and concentrations high as 20 and 40 μg PM₁₀ mL^-1 induced elevated cell death. Ultrastructure analyses showed aluminosilicate, iron, and the emerging metallic contaminants titanium, bismuth, and cerium nanoparticles were incorporated into lung cells, in which the nanocrystallography analysis indicated the bismuth as Bi₂O₃. All internalized metallic nanoparticles were free and unbound in the cytoplasm and nucleus thereby indicating bioavailability and potential interaction to biological processes and cellular structures. Pearson's correlation analysis showed Fe, Ni, Al, Cr, Pb and Hg as the main cytotoxic elements which are associated with the stainless steel production. The presence of internalized nanoparticles in human lung cells exposed to environmental atmospheric matter highlights the need for a greater effort by regulatory agencies to understand their potential damage and hence the need for future regulation, especially of emerging metallic contaminants.

Detection and Characterization of TiO2 Nanomaterials in Sludge from Wastewater Treatment Plants of Chihuahua State, Mexico

TiO₂ nanoparticles (TiO₂-NPs) have a wide range of industrial applications (paintings, sunscreens, food and cosmetics) and is one of the most intensively used nanomaterials worldwide. Leaching from commercial products TiO₂-NPs are predicted to significantly accumulate in wastewater sludges, which are then often used as soil amendment. In this work, sludge samples from four wastewater treatment plants of the Chihuahua State in Mexico were obtained during spring and summer (2017). A comprehensive characterization study was performed by X-ray based (laboratory and synchrotron) techniques and electron microscopy. Ti was detected in all sludge samples (1810–2760 mg/kg) mainly as TiO₂ particles ranging from 40 nm up to hundreds of nm. Micro-XANES data was analyzed by principal component analysis and linear combination fitting enabling the identification of three predominant Ti species: anatase, rutile and ilmenite. Micro-XANES from the smaller Ti particles was predominantly anatase (68% + 32% rutile), suggesting these TiO₂-NPs originate from paintings and cosmetics. TEM imaging confirmed the presence of nanoscale Ti with smooth surface morphologies resembling engineered TiO₂-NPs. The size and crystalline phase of TiO₂-NPs in the sludge from this region suggest increased reactivity and potential toxicity to agro-systems. Further studies should be dedicated to evaluating this.

Metal-Induced Crystallization in Metal Oxides

ConspectusThe properties of a material depend upon its physical characteristics, one of these being its crystalline state. Next generation solid-state technologies will integrate crystalline oxides into thermal sensitive processes and composite materials. Crystallization of amorphous phases of metal oxides in the solid state typically requires substantial energy input to induce the amorphous to crystalline phase transformation. In the case of silica, the transformation to α-quartz in a furnace occurs above 1300 °C and that of titania, above 400 °C. These calcination processes are costly in energy but also often degrade complex material architectures or compositions.Thus, low temperature crystallization techniques are required that preserve macro- and mesostructures and complex elemental composition (e.g., organic-, metal-, and semiconductor-metal oxide hybrids/composites). Some solution-based techniques exist to directly fabricate crystalline metal oxides. However, these are not always compatible with the specificities of the system or industrial constraints. A postsynthetic, solid-state approach that reduces crystallization temperature in metal oxides is metal-induced crystallization (MIC).MIC is the introduction of catalytic amounts of a cation, which can be an s-block, p-block, or d-block cation, that migrates through the solid metal oxide lattice. The cation is thought to temporarily break metal oxide bonds, allowing [MOx] polyhedra to rotate and reform bonds with neighboring [MOx] groups in a lower energy crystalline phase. Depending on the system, the cation can favor or defavor the formation of a particular crystalline phase, providing a means to tune the purity and crystalline phase ratios. An advantage of MIC is that, although the crystallization occurs in the solid state, the crystallization process can be accomplished for particle suspensions in liquid media. In this case, the energy required to induce the crystallization can come from, for example, a microwave or an ultrasound bath. The crystallization of particles in suspension avoids aggregation from particle-particle sintering. In the case of thin films, the energy for crystallization typically comes from a laser or calcination.MIC is only recently being used as a low temperature metal oxide crystallization technique, despite being widely used in the semiconductor industry. Here, the mechanism and previous studies in MIC are presented for titania, silica, and other oxides. The beauty of this technique is that it is extremely easy to employ: cations can be incorporated into the system postsynthetically and then are often expelled from the lattice upon phase conversion. We expect MIC to enrich materials for photochromic, optoelectronic, catalyst, biological, and other applications.

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

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

Nickel nanoparticle-induced cell transformation: involvement of DNA damage and DNA repair defect through HIF-1α/miR-210/Rad52 pathway

BACKGROUND

Nickel nanoparticles (Nano-Ni) are increasingly used in industry and biomedicine with the development of nanotechnology. However, the genotoxic and carcinogenic effects of Nano-Ni and the underlying mechanisms are still unclear.

METHODS

At first, dose-response (0, 10, 20, and 30 μg/mL) and time-response (0, 3, 6, 12, and 24 h) studies were performed in immortalized normal human bronchial epithelial cells BEAS-2B to observe the effects of Nano-Ni on DNA damage response (DDR)-associated proteins and the HIF-1α/miR-210/Rad52 pathway by real-time PCR or Western blot. Then, a Hsp90 inhibitor (1 µM of 17-AAG, an indirect HIF-1α inhibitor), HIF-1α knock-out (KO) cells, and a miR-210 inhibitor (20 nM) were used to determine whether Nano-Ni-induced Rad52 down-regulation was through HIF-1α nuclear accumulation and miR-210 up-regulation. In the long-term experiments, cells were treated with 0.25 and 0.5 µg/mL of Nano-Ni for 21 cycles (~ 150 days), and the level of anchorage-independent growth was determined by plating the cells in soft agar. Transduction of lentiviral particles containing human Rad52 ORF into BEAS-2B cells was used to observe the role of Rad52 in Nano-Ni-induced cell transformation. Nano-Ni-induced DNA damage and dysregulation of HIF-1α/miR-210/Rad52 pathway were also investigated in vivo by intratracheal instillation of 50 µg per mouse of Nano-Ni. gpt delta transgenic mice were used to analyze mutant frequency and mutation spectrum in mouse lungs after Nano-Ni exposure.

RESULTS

Nano-Ni exposure caused DNA damage at both in vitro and in vivo settings, which was reflected by increased phosphorylation of DDR-associated proteins such as ATM at Ser1981, p53 at Ser15, and H2AX. Nano-Ni exposure also induced HIF-1α nuclear accumulation, miR-210 up-regulation, and down-regulation of homologous recombination repair (HRR) gene Rad52. Inhibition of or knocking-out HIF-1α or miR-210 ameliorated Nano-Ni-induced Rad52 down-regulation. Long-term low-dose Nano-Ni exposure led to cell malignant transformation, and augmentation of Rad52 expression significantly reduced Nano-Ni-induced cell transformation. In addition, increased immunostaining of cell proliferation markers, Ki-67 and PCNA, was observed in bronchiolar epithelial cells and hyperplastic pneumocytes in mouse lungs at day 7 and day 42 after Nano-Ni exposure. Finally, using gpt delta transgenic mice revealed that Nano-Ni exposure did not cause increased gpt mutant frequency and certain DNA mutations, such as base substitution and small base insertions/deletions, are not the main types of Nano-Ni-induced DNA damage.

CONCLUSIONS

This study unraveled the mechanisms underlying Nano-Ni-induced cell malignant transformation; the combined effects of Nano-Ni-induced DNA damage and DNA repair defects through HIF-1α/miR-210/Rad52 pathway likely contribute to Nano-Ni-induced genomic instability and ultimately cell transformation. Our findings will provide information to further elucidate the molecular mechanisms of Nano-Ni-induced genotoxicity and carcinogenicity.

Behaviour of Titanium Dioxide Particles in Artificial Body Fluids and Human Blood Plasma

The growing application of materials containing TiO₂ particles has led to an increased risk of human exposure, while a gap in knowledge about the possible adverse effects of TiO₂ still exists. In this work, TiO₂ particles of rutile, anatase, and their commercial mixture were exposed to various environments, including simulated gastric fluids and human blood plasma (both representing in vivo conditions), and media used in in vitro experiments. Simulated body fluids of different compositions, ionic strengths, and pH were used, and the impact of the absence or presence of chosen enzymes was investigated. The physicochemical properties and agglomeration of TiO₂ in these media were determined. The time dependent agglomeration of TiO₂ related to the type of TiO₂, and mainly to the type and composition of the environment that was observed. The presence of enzymes either prevented or promoted TiO₂ agglomeration. TiO₂ was also observed to exhibit concentration-dependent cytotoxicity. This knowledge about TiO₂ behavior in all the abovementioned environments is critical when TiO₂ safety is considered, especially with respect to the significant impact of the presence of proteins and size-related cytotoxicity.

Inhibition of testosterone synthesis induced by oral TiO2 NPs is associated with ROS-MAPK(ERK1/2)-StAR signaling pathway in SD rat

Titanium dioxide nanoparticles (TiO₂ NPs) have been widely used in food, medical, and other fields; their reproductive toxicity has been reported in numerous studies. However, the relevant toxicity mechanism still requires further exploration. In this paper, the effect of oral exposure to 500 mg/kg TiO₂ NPs (anatase and rutile) in adult male SD rats was studied over 3 and 7 days. Results showed that the total sperm count and testosterone level of 7 days of exposure in serum decreased in the experimental group. Testicular tissue lesions, such as disappearance of Leydig cells, disorder of arrangement of spermatogenic cells in the lumen of convoluted seminiferous tubules, and disorder of arrangement of germ cells, were observed. Meanwhile, the expression of steroidogenic acute regulatory (StAR; the key factors of testosterone synthesis), MAPK (ERK1/2), and phosphorylated ERK1/2 in testes of SD rats after exposure to TiO₂ NPs for 7 days decreased, while the malondialdehyde content increased and superoxide dismutase activity decreased in serum. The present study showed that TiO₂ NPs could cause reproductive toxicity. Notably, anatase is more toxic than rutile. In addition, exposure to 500 mg/kg TiO₂ NPs for 7 days inhibited testosterone synthesis in male rat, which may be related to the reactive oxygen species (ROS)-MAPK (ERK1/2)-StAR signal pathway. Warning that the use of TiO₂ NPs should be regulated.

Ovarian toxicity of nanoparticles

The ovary is a highly important organ for female reproduction. The main functions include sex steroid hormone synthesis, follicular development, and achievement of oocyte meiotic and development competence for proper fertilization. Nanoparticle (NP) exposure is becoming unavoidable because of its wide use in different products, including cosmetics, food, health, and personal care products. Studies examining different nonreproductive tissues or systems have shown that characteristics such as the size, shape, core material, agglomeration, and dissolution influence the effects of NPs. However, most studies evaluating NP-mediated reproductive toxicity have paid little or no attention to the influence of the physicochemical characteristics of NP on the observed effects. As accumulating evidence indicates that NP may reach the ovary to impair proper functions, this review summarizes the available data on NP accumulation in ovarian tissue, as well as data describing toxicity to ovarian functions, including sex steroid hormone production, follicular development, oocyte quality, and fertility. Due to their toxicological relevance, this review also describes the main physicochemical characteristics involved in NP toxicity and the importance of considering NP physicochemical characteristics as factors influencing the ovarian toxicity of NPs. Finally, this review summarizes the main mechanisms of toxicity described in ovarian cells.

Mechanical Behavior of Bi-Layer and Dispersion Coatings Composed of Several Nanostructures on Ti13Nb13Zr Alloy

Titanium implants are commonly used because of several advantages, but their surface modification is necessary to enhance bioactivity. Recently, their surface coatings were developed to induce local antibacterial properties. The aim of this research was to investigate and compare mechanical properties of three coatings: multi-wall carbon nanotubes (MWCNTs), bi-layer composed of an inner MWCNTs layer and an outer TiO₂ layer, and dispersion coatings comprised of simultaneously deposited MWCNTs and nanoCu, each electrophoretically deposited on the Ti13Nb13Zr alloy. Optical microscopy, scanning electron microscopy, X-ray electron diffraction spectroscopy, and nanoindentation technique were applied to study topography, chemical composition, hardness, plastic and elastic properties. The results demonstrate that the addition of nanocopper or titanium dioxide to MWCNTs coating increases hardness, lowers Young’s modulus, improves plastic and elastic properties, wear resistance under deflection, and plastic deformation resistance. The results can be attributed to different properties, structure and geometry of applied particles, various deposition techniques, and the possible appearance of porous structures. These innovative coatings of simultaneously high strength and elasticity are promising to apply for deposition on long-term titanium implants.

Suitability of Nanoparticles to Face Benzo(a)pyrene-Induced Genetic and Chromosomal Damage in M. galloprovincialis. An In Vitro Approach

Benzo(a)pyrene (B(a)P) is a well-known genotoxic agent, the removal of which from environmental matrices is mandatory, necessitating the application of cleaning strategies that are harmless to human and environmental health. The potential application of nanoparticles (NPs) in the remediation of polluted environments is of increasing interest. Here, specifically designed NPs were selected as being non-genotoxic and able to interact with B(a)P, in order to address the genetic and chromosomal damage it produces. A newly formulated pure anatase nano-titanium (nano-TiO2), a commercial mixture of rutile and anatase, and carbon black-derived hydrophilic NPs (HNP) were applied. Once it had been ascertained that the NPs selected for the work did not induce genotoxicity, marine mussel gill biopsies were exposed in vitro to B(a)P (2 μg/mL), alone and in combination with the selected NPs (50 µg/mL nano-TiO2, 10 µg/mL HNP). DNA primary reversible damage was evaluated by means of the Comet assay. Chromosomal persistent damage was assessed on the basis of micronuclei frequency and nuclear abnormalities by means of the Micronucleus-Cytome assay. Transmission Electron Microscopy (TEM) was performed to investigate the mechanism of action exerted by NPs. Pure Anatase n-TiO2 was found to be the most suitable for our purpose, as it is cyto- and genotoxicity free and able to reduce the genetic and chromosomal damage associated with exposure to B(a)P.

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

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

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

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

Interfacial Synthesis: Morphology, Structure, and Properties of Interfacial Formations in Liquid–Liquid Systems

Abstract

The results of studies in the field of interfacial synthesis and interfacial formations in liquid–liquid systems are summarized. The mechanisms of the processes of interfacial synthesis are considered. Data on the self-assembly of nanoparticles, films, and 3D materials are given. The properties of materials of interfacial formations in systems with rare-earth elements and di(2-ethylhexyl)phosphoric acid, obtained both in the presence and absence of local vibrations, are described. It was established that materials obtained in the presence of local vibrations in the interfacial layer have higher density, melting point, and magnetic susceptibility and lower electric conductivity. The effect of force field parameters on the properties of interfacial formations is considered. Practical applications and prospects for research in the field of interfacial formations are discussed.

Changes in bacterial diversity of activated sludge exposed to titanium dioxide nanoparticles

The rapid growth of the use of nanomaterials in different modern industrial branches makes the study of the impact of nanoparticles on the human health and environment an urgent matter. For instance, it has been reported that titanium dioxide nanoparticles (TiO₂ NPs) can be found in wastewater treatment plants. Previous studies have found contrasting effects of these nanoparticles over the activated sludge process, including negative effects on the oxygen uptake. The non-utilization of oxygen reflects that aerobic bacteria were inhibited or decayed. The aim of this work was to study how TiO₂ NPs affect the bacterial diversity and metabolic processes on an activated sludge. First, respirometry assays of 8 h were carried out at different concentrations of TiO₂ NPs (0.5-2.0 mg/mL) to measure the oxygen uptake by the activated sludge. The bacterial diversity of these assays was determined by sequencing the amplified V3-V4 region of the 16S rRNA gene using Illumina MiSeq. According to the respirometry assays, the aerobic processes were inhibited in a range from 18.5 ± 4.8% to 37.5 ± 2.0% for concentrations of 0.5-2.0 mg/mL TiO₂ NPs. The oxygen uptake rate was affected mainly after 4.5 h for concentrations higher than 1.0 mg/mL of these nanoparticles. Results indicated that, in the presence of TiO₂ NPs, the bacterial community of activated sludge was altered mainly in the genera related to nitrogen removal (nitrogen assimilation, nitrification and denitrification). The metabolic pathways prediction suggested that genes related to biofilm formation were more sensitive than genes directly related to nitrification-denitrification and N-assimilation processes. These results indicated that TiO₂ NPs might modify the bacteria diversity in the activated sludge according to their concentration and time of exposition, which in turn impact in the performance of the wastewater treatment processes.

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.

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.

Impact of different crystalline forms of nTiO2 on metabolism and arsenic toxicity in Limnoperna fortunei

Arsenic (As) is a ubiquitous contaminant in the environment and it is known to induce oxidative stress in aquatic organisms. In an attempt to remove As from water, some studies have suggested the titanium dioxide nanomaterial (nTiO₂) as a promising alternative. However, it has been observed that nTiO₂ can induce toxicity alone or in combination with metals, and this toxicity is dependent on its crystalline form of nanomaterial (mainly rutile as nTiO₂R and anatase as nTiO₂A, respectively). Considering that both (nTiO₂ and As) can occur together, the objective of this study was to evaluate if co-exposure to rutile and anatase may influence accumulation, metabolisation, and toxicity of arsenite (As⁺³) in the golden mussel Limnoperna fortunei after 48 h of co-exposure to nTiO₂ (1 mg/L) and As (50 μg/L). Accumulation and chemical speciation of As in organisms were determined. Also, biochemical analyses, such as the activity of the enzymes glutathione S-transferase omega (GSTΩ), catalase (CAT) and glutathione S-transferase (GST), as well as lipid peroxidation (LPO) were investigated. Results showed that co-exposure to nTiO₂A + As changed accumulation pattern of metalloid in gills and digestive gland. Both crystalline forms of nTiO₂ affected the metabolisation capacity favoring the accumulation of more toxic As compounds and nTiO₂A alone or in combination with As showed induce oxidative stress in gills of L. fortunei. In this way, it has a high potential risk of the co-exposure of these contaminants to aquatic organisms, and it also needs to consider the nanomaterial (nTiO₂) properties and their application in the environmental remediation, carefully and judiciously.

Toxicity of TiO2 Nanoparticles: Validation of Alternative Models

There are many studies concerning titanium dioxide (TiO2) nanoparticles (NP) toxicity. Nevertheless, there are few publications comparing in vitro and in vivo exposure, and even less comparing air-liquid interface exposure (ALI) with other in vitro and in vivo exposures. The identification and validation of common markers under different exposure conditions are relevant for the development of smart and quick nanotoxicity tests. In this work, cell viability was assessed in vitro by WST-1 and LDH assays after the exposure of NR8383 cells to TiO2 NP sample. To evaluate in vitro gene expression profile, NR8383 cells were exposed to TiO2 NP during 4 h at 3 cm2 of TiO2 NP/cm2 of cells or 19 μg/mL, in two settings-submerged cultures and ALI. For the in vivo study, Fischer 344 rats were exposed by inhalation to a nanostructured aerosol at a concentration of 10 mg/m3, 6 h/day, 5 days/week for 4 weeks. This was followed immediately by gene expression analysis. The results showed a low cytotoxic potential of TiO2 NP on NR8383 cells. Despite the absence of toxicity at the doses studied, the different exposures to TiO2 NP induce 18 common differentially expressed genes (DEG) which are involved in mitosis regulation, cell proliferation and apoptosis and inflammation transport of membrane proteins. Among these genes, we noticed the upregulation of Ccl4, Osm, Ccl7 and Bcl3 genes which could be suggested as early response biomarkers after exposure to TiO2 NP. On the other hand, the comparison of the three models helped us to validate the alternative ones, namely submerged and ALI approaches.

Chaud M, Morsink M, Willemen N, Severino P, Santini A, Souto EB. Nanotoxicology and Nanosafety: Safety-By-Design and Testing at a Glance

This review offers a systematic discussion about nanotoxicology and nanosafety associated with nanomaterials during manufacture and further biomedical applications. A detailed introduction on nanomaterials and their most frequently uses, followed by the critical risk aspects related to regulatory uses and commercialization, is provided. Moreover, the impact of nanotoxicology in research over the last decades is discussed, together with the currently available toxicological methods in cell cultures (in vitro) and in living organisms (in vivo). A special focus is given to inorganic nanoparticles such as titanium dioxide nanoparticles (TiO2NPs) and silver nanoparticles (AgNPs). In vitro and in vivo case studies for the selected nanoparticles are discussed. The final part of this work describes the significance of nano-security for both risk assessment and environmental nanosafety. "Safety-by-Design" is defined as a starting point consisting on the implementation of the principles of drug discovery and development. The concept "Safety-by-Design" appears to be a way to "ensure safety", but the superficiality and the lack of articulation with which it is treated still raises many doubts. Although the approach of "Safety-by-Design" to the principles of drug development has helped in the assessment of the toxicity of nanomaterials, a combination of scientific efforts is constantly urgent to ensure the consistency of methods and processes. This will ensure that the quality of nanomaterials is controlled and their safe development is promoted. Safety issues are considered strategies for discovering novel toxicological-related mechanisms still needed to be promoted.

Enhanced Antibacterial Activity of Se Nanoparticles Upon Coating with Recombinant Spider Silk Protein eADF4(κ16)

PURPOSE

Selenium nanoparticles (Se NPs) are promising antibacterial agents to tackle the growing problem of antimicrobial resistance. The aim of this study was to fabricate Se NPs with a net positive charge to enhance their antibacterial efficacy.

METHODS

Se NPs were coated with a positively charged protein - recombinant spider silk protein eADF4(κ16) - to give them a net positive surface charge. Their cytotoxicity and antibacterial activity were investigated, with negatively charged polyvinyl alcohol coated Se NPs as a control. Besides, these eADF4(κ16)-coated Se NPs were immobilized on the spider silk films, and the antibacterial activity of these films was investigated.

RESULTS

Compared to the negatively charged polyvinyl alcohol coated Se NPs, the positively charged eADF4(κ16)-coated Se NPs demonstrated a much higher bactericidal efficacy against the Gram-negative bacteria E. coli, with a minimum bactericidal concentration (MBC) approximately 50 times lower than that of negatively charged Se NPs. Cytotoxicity testing showed that the eADF4(κ16)-coated Se NPs are safe to both Balb/3T3 mouse embryo fibroblasts and HaCaT human skin keratinocytes up to 31 µg/mL, which is much higher than the MBC of these particles against E. coli (8 ± 1 µg/mL). In addition, antibacterial coatings were created by immobilising the eADF4(κ16)-coated Se NPs on positively charged spider silk films and these were shown to retain good bactericidal efficacy and overcome the issue of low particle stability in culture broth. It was found that these Se NPs needed to be released from the film surface in order to exert their antibacterial effects and this release can be regulated by the surface charge of the film, such as the change of the spider silk protein used.

CONCLUSION

Overall, eADF4(κ16)-coated Se NPs are promising new antibacterial agents against life-threatening bacteria.

Identification of inhalable rutile and polycyclic aromatic hydrocarbons (PAHs) nanoparticles in the atmospheric dust

Addressing the presence of rutile nanoparticles (NPs) in the air is a work in progress, and the development of methodologies for the identification of NPs in atmospheric dust is essential for the assessment of its toxicological effects. To address this issue, we selected the fast growing desertic city of Hermosillo in northern Mexico. Road dust (n = 266) and soils (n = 10) were sampled and bulk Ti-contents were tested by portable X-ray fluorescence. NPs were extracted from atmospheric dust by PM_1.0-PTFE filters and further characterized by Confocal Raman Microscopy, Energy-dispersive X-ray spectroscopy (EDS) coupled to Transmission Electron Microscopy (TEM) and Scanning Electron Microscopy (SEM). Results showed (i) the average concentration of Ti in road dust (3447 mg kg^-1) was similar to natural values and worldwide urban dusts; (ii) the bulk geochemistry was not satisfactory for Ti-NPs identification; (iii) 76% of the total extracted PM_1.0 sample corresponded to NPs; (iv) mono-microaggregates of rutile NPs were identified; (v) ubiquitous polycyclic aromatic hydrocarbons (PAHs) were linked to NPs. The genotoxicity of rutile and PAHs, in connection with NPs content, make us aware of a crucial emerging environmental issue of significant health concern, justifying further research in this field.

Insights into Theranostic Properties of Titanium Dioxide for Nanomedicine

Titanium dioxide (TiO2) nanostructures exhibit a broad range of theranostic properties that make them attractive for biomedical applications. TiO2 nanostructures promise to improve current theranostic strategies by leveraging the enhanced quantum confinement, thermal conversion, specific surface area, and surface activity. This review highlights certain important aspects of fabrication strategies, which are employed to generate multifunctional TiO2 nanostructures, while outlining post-fabrication techniques with an emphasis on their suitability for nanomedicine. The biodistribution, toxicity, biocompatibility, cellular adhesion, and endocytosis of these nanostructures, when exposed to biological microenvironments, are examined in regard to their geometry, size, and surface chemistry. The final section focuses on recent biomedical applications of TiO2 nanostructures, specifically evaluating therapeutic delivery, photodynamic and sonodynamic therapy, bioimaging, biosensing, tissue regeneration, as well as chronic wound healing.

Improving our understanding of metal implant failures: Multiscale chemical imaging of exogenous metals in ex-vivo biological tissues

Biological exposures to micro- and nano-scale exogenous metal particles generated as a consequence of in-service degradation of orthopaedic prosthetics can result in severe adverse tissues reactions. However, individual reactions are highly variable and are not easily predicted, due to in part a lack of understanding of the speciation of the metal-stimuli which dictates cellular interactions and toxicity. Investigating the chemistry of implant derived metallic particles in biological tissue samples is complicated by small feature sizes, low concentrations and often a heterogeneous speciation and distribution. These challenges were addressed by developing a multi-scale two-dimensional X-ray absorption spectroscopic (XAS) mapping approach to discriminate sub-micron changes in particulate chemistry within ex-vivo tissues associated with failed CoCrMo total hip replacements (THRs). As a result, in the context of THRs, we demonstrate much greater variation in Cr chemistry within tissues compared with previous reports. Cr compounds including phosphate, hydroxide, oxide, metal and organic complexes were observed and correlated with Co and Mo distributions. This variability may help explain the lack of agreement between biological responses observed in experimental exposure models and clinical outcomes. The multi-scale 2D XAS mapping approach presents an essential tool in discriminating the chemistry in dilute biological systems where speciation heterogeneity is expected. SIGNIFICANCE: Metal implants are routinely used in healthcare but may fail following degradation in the body. Although specific implants can be identified as 'high-risk', our analysis of failures is limited by a lack of understanding of the chemistry of implant metals within the peri-prosthetic milieu. A new approach to identify the speciation and variability in speciation at sub-micron resolution, of dilute exogenous metals within biological tissues is reported; applied to understanding the failure of metallic (CoCrMo) total-hip-replacements widely used in orthopedic surgery. Much greater variation in Cr chemistry was observed compared with previous reports and included phosphate, hydroxide, oxide, metal and organic complexes. This variability may explain lack of agreement between biological responses observed in experimental exposure models and clinical outcomes.

Protein Binding Effects of Dopamine Coated Titanium Dioxide Shell Nanoparticles

Non-targeted nanoparticles are capable of entering cells, passing through different subcellular compartments and accumulating on their surface a protein corona that changes over time. In this study, we used metal oxide nanoparticles with iron-oxide core covered with titanium dioxide shell (Fe3O4@TiO2), with a single layer of covalently bound dopamine covering the nanoparticle surface. Mixing nanoparticles with cellular protein isolates showed that these nanoparticles can form complexes with numerous cellular proteins. The addition of non-toxic quantities of nano-particles to HeLa cell culture resulted in their non-specific uptake and accumulation of protein corona on nanoparticle surface. TfRC, Hsp90 and PARP were followed as representative protein components of nanoparticle corona; each protein bound to nanoparticles with different affinity. The presence of nanoparticles in cells also mildly modulated gene expression on the level of mRNA. In conclusion, cells exposed to non-targeted nanoparticles show subtle but numerous changes that are consistent from one experiment to another.

Targeting of CD133+ Cancer Stem Cells by Mesenchymal Stem Cell Expressing TRAIL Reveals a Prospective Role of Apoptotic Gene Regulation in Non-Small Cell Lung Cancer

Mesenchymal stem cells (MSCs) are emerging as vehicles for anti-tumor cytotherapy; however, investigation on its efficacy to target a specific cancer stem cell (CSC) population in non-small cell lung cancer (NSCLC) is lacking. Using assays to evaluate cell proliferation, apoptosis, and gene expression, we investigated the efficacy of MSCs expressing tumour necrosis factor (TNF)-related apoptosis inducing ligand (MSC-TRAIL) to target and destroy CD133+ (prominin-1 positive) NSCLC-derived CSCs. Characterization of TRAIL death receptor 5 (DR5) revealed that it was highly expressed in the CD133+ CSCs of both H460 and H2170 cell lines. The human MSC-TRAIL generated in the study maintained its multipotent characteristics, and caused significant tumor cell inhibition in NSCLC-derived CSCs in a co-culture. The MSC-TRAIL induced an increase in annexin V expression, an indicator of apoptosis in H460 and H2170 derived CD133+ CSCs. Through investigation of mitochondria membrane potential, we found that MSC-TRAIL was capable of inducing intrinsic apoptosis to the CSCs. Using pathway-specific gene expression profiling, we uncovered candidate genes such as NFKB1, BAG3, MCL1, GADD45A, and HRK in CD133+ CSCs, which, if targeted, might increase the sensitivity of NSCLC to MSC-TRAIL-mediated inhibition. As such, our findings add credibility to the utilization of MSC-TRAIL for the treatment of NSCLC through targeting of CD133+ CSCs.

Evaluation of cytogenotoxicity and oxidative stress parameters in male Swiss mice co-exposed to titanium dioxide and zinc oxide nanoparticles

A number of studies have investigated the adverse toxic effects of titanium dioxide (TiO₂) nanoparticles (NPs) or zinc oxide (ZnO) NPs. Information on the potential genotoxic effects of the interactions of TiO₂ NPs and ZnO NPs in vivo is lacking. Therefore, this study was designed to investigate the cytogenotoxicity of TiO₂ NPs or ZnO NPs alone or their mixtures using the bone marrow micronucleus assay, and mechanism of damage through the evaluation of oxidative stress parameters in the liver and kidney tissues of Swiss mice. Intraperitoneal administration of doses between 9.38 and 150.00 mg/kg of TiO₂ NPs or ZnO NPs or TiO₂ NPs + ZnO NPs was performed for 5 and 10 days, respectively. TiO₂ NPs alone induced a significant (P <  0.05) increase in micronucleated (Mn) polychromatic erythrocytes (PCEs) at the applied doses compared with the negative controls, with a significant difference between 5 and 10 days for TiO₂ NPs alone and TiO₂ NPs + ZnO NPs. Concurrently, TiO₂ NPs alone for 5 days and TiO₂ NPs and TiO₂ NPs + ZnO NPs for 10 days significantly (P <  0.05) decreased the percentage PCE: normochromatic erythrocyte (NCE) indicating cytotoxicity; with a significant difference between the two periods. Significant (P <  0.001) changes in the activities of superoxide dismutase (SOD) and catalase (CAT), and levels of reduced glutathione (GSH) and malondialdehyde (MDA) were observed in the liver and kidney of mice exposed to TiO₂ NPs or ZnO NPs alone or their mixtures. These results suggest that TiO₂ NPs alone was genotoxic; TiO₂ NPs and TiO₂ NPs + ZnO NPs were noticeably cytotoxic while ZnO NPs was not cytogenotoxic. The individual NPs or their mixtures induced oxidative stress.

Acute Cytotoxic Effects on Morphology and Mechanical Behavior in MCF-7 Induced by TiO2NPs Exposure

The side effects induced by nanoparticle exposure at a cellular level are one of the priority research topics due to the steady increase in the use of nanoparticles (NPs). Recently, the focus on cellular morphology and mechanical behavior is gaining relevance in order to fully understand the cytotoxic mechanisms. In this regard, we have evaluated the morphomechanical alteration in human breast adenocarcinoma cell line (MCF-7) exposed to TiO₂NPs at two different concentrations (25 and 50 µg/mL) and two time points (24 and 48 h). By using confocal and atomic force microscopy, we demonstrated that TiO₂NP exposure induces significant alterations in cellular membrane elasticity, due to actin proteins rearrangement in cytoskeleton, as calculated in correspondence to nuclear and cytoplasmic compartments. In this work, we have emphasized the alteration in mechanical properties of the cellular membrane, induced by nanoparticle exposure.

Nanoparticle transport and sequestration: Intracellular titanium dioxide nanoparticles in a neotropical fish

Intracellular titanium dioxide nanoparticles (TiO₂-NP) with rutile crystalline form and dimensions varying from 43 to 67 nm × 64 to 93 nm are reported for the first time as being sequestered from the environment. TiO₂-NP were identified inside all organs/tissues (muscle, kidney, gonad, hepatopancreas and gill) in both the cytoplasm and nucleus of the neotropical fish Centropomus parallelus, captured in an area affected by metallurgical activity. Atmospheric particulate matter (PM) sampled in the same area showed the presence of TiO₂-NP with the same rutile crystalline form and dimensions varying from 16 to 93 nm × 45 to 193 nm, thus indicating the smelting and iron processing industries as the most probable source of TiO₂-NP. In any sample, chemical analyses identify and quantify Ti concentration and nanocrystallography identified the structure of TiO₂-NP. The Ti concentration in the sediment and atmospheric PM varied between years and it was mirrored by the Ti concentration in the fish organs. The gill has a higher Ti concentration varying from 5.50 to 14.57 μg g^-1 dry weight and the gonad was the organ with lowest Ti level, 0.25 to 0.87 μg g^-1 dry weight. In the muscles, Ti concentration varied from 0.85 to 3.34 μg g^-1 dry weight. This contamination may be likely to affect the surrounding biota and food uptake, including the humans living in the city close to the metallurgical complex. These findings emphasised the needs to improve methods to reduce PM (including nanoparticles) arising from human activities and to evaluate the toxicokinetic and effects of TiO₂-NP in the biota and human health.

Biological monitoring of workers exposed to engineered nanomaterials

As the number of nanomaterial workers increase there is need to consider whether biomonitoring of exposure should be used as a routine risk management tool. Currently, no biomonitoring of nanomaterials is mandated by authoritative or regulatory agencies. However, there is a growing knowledge base to support such biomonitoring, but further research is needed as are investigations of priorities for biomonitoring. That research should be focused on validation of biomarkers of exposure and effect. Some biomarkers of effect are generally nonspecific. These biomarkers need further interpretation before they should be used. Overall biomonitoring of nanomaterial workers may be important to supplement risk assessment and risk management efforts.