Exposure to titanium dioxide and other metallic oxide nanoparticles induces cytotoxicity on human neural cells and fibroblasts

Food-grade titanium dioxide (E171) and zinc oxide nanoparticles induce mitochondrial permeability and cardiac damage after oral exposure in rats

Food-grade titanium dioxide (E171) and zinc oxide nanoparticles (ZnO NPs) are found in diverse products for human use. E171 is used as whitening agent in food and cosmetics, and ZnO NPs in food packaging. Their potential multi-organ toxicity has raised concerns on their safety. Since mitochondrial dysfunction is a key aspect of cardio-pathologies, here, we evaluate the effect of chronic exposure to E171 and ZnO NPs in rats on cardiac mitochondria. Changes in cardiac electrophysiology and body weight were measured. E171 reduced body weight more than 10% after 5 weeks. Both E171 and ZnO NPs increased systolic blood pressure (SBP) from 110-120 to 120-140 mmHg after 45 days of treatment. Both NPs altered the mitochondrial permeability transition pore (mPTP), reducing calcium requirement for permeability by 60% and 93% in E171- and ZnO NPs-exposed rats, respectively. Treatments also affected conformational state of adenine nucleotide translocase (ANT). E171 reduced the binding of EMA to Cys 159 in 30% and ZnO NPs in 57%. Mitochondrial aconitase activity was reduced by roughly 50% with both NPs, indicating oxidative stress. Transmission electron microscopy (TEM) revealed changes in mitochondrial morphology including sarcomere discontinuity, edema, and hypertrophy in rats exposed to both NPs. In conclusion, chronic oral exposure to NPs induces functional and morphological damage in cardiac mitochondria, with ZnO NPs being more toxic than E171, possibly due to their dissociation in free Zn2+ ion form. Therefore, chronic intake of these food additives could increase risk of cardiovascular disease.

Food-grade titanium dioxide and zinc oxide nanoparticles induce toxicity and cardiac damage after oral exposure in rats

BACKGROUND

Metallic nanoparticles (NPs) are widely used as food additives for human consumption. NPs reach the bloodstream given their small size, getting in contact with all body organs and cells. NPs have adverse effects on the respiratory and intestinal tract; however, few studies have focused on the toxic consequences of orally ingested metallic NPs on the cardiovascular system. Here, the effects of two food-grade additives on the cardiovascular system were analyzed.

METHODS

Titanium dioxide labeled as E171 and zinc oxide (ZnO) NPs were orally administered to Wistar rats using an esophageal cannula at 10 mg/kg bw every other day for 90 days. We evaluated cardiac cell morphology and death, expression of apoptotic and autophagic proteins in cardiac mitochondria, mitochondrial dysfunction, and concentration of metals on cardiac tissue.

RESULTS

Heart histology showed important morphological changes such as presence of cellular infiltrates, collagen deposition and mitochondrial alterations in hearts from rats exposed to E171 and ZnO NPs. Intracellular Cyt-C levels dropped, while TUNEL positive cells increased. No significant changes in the expression of inflammatory cytokines were detected. Both NPs altered mitochondrial function indicating cardiac dysfunction, which was associated with an elevated concentration of calcium. ZnO NPs induced expression of caspases 3 and 9 and two autophagic proteins, LC3B and beclin-1, and had the strongest effect compared to E171.

CONCLUSIONS

E171 and ZnO NPs induce adverse cardiovascular effects in rats after 90 days of exposure, thus food intake containing these additives, should be taken into consideration, since they translocate into the bloodstream and cause cardiovascular damage.

Effects of Zinc Oxide Nanoparticle Exposure on Human Glial Cells and Zebrafish Embryos

Zinc oxide nanoparticles (ZnO NPs) are among the most widely used nanomaterials. They have multiple applications in cosmetics, textiles, paints, electronics and, recently, also in biomedicine. This extensive use of ZnO NPs notably increases the probability that both humans and wildlife are subjected to undesirable effects. Despite being among the most studied NPs from a toxicological point of view, much remains unknown about their ecotoxicological effects or how they may affect specific cell types, such as cells of the central nervous system. The main objective of this work was to investigate the effects of ZnO NPs on human glial cells and zebrafish embryo development and to explore the role of the released Zn2+ ions in these effects. The effects on cell viability on human A172 glial cells were assessed with an MTT assay and morphological analysis. The potential acute and developmental toxicity was assessed employing zebrafish (Danio rerio) embryos. To determine the role of Zn2+ ions in the in vitro and in vivo observed effects, we measured their release from ZnO NPs with flame atomic absorption spectrometry. Then, cells and zebrafish embryos were treated with a water-soluble salt (zinc sulfate) at concentrations that equal the number of Zn2+ ions released by the tested concentrations of ZnO NPs. Exposure to ZnO NPs induced morphological alterations and a significant decrease in cell viability depending on the concentration and duration of treatment, even after removing the overestimation due to NP interference. Although there were no signs of acute toxicity in zebrafish embryos, a decrease in hatching was detected after exposure to the highest ZnO NP concentrations tested. The ability of ZnO NPs to release Zn2+ ions into the medium in a concentration-dependent manner was confirmed. Zn2+ ions did not seem entirely responsible for the effects observed in the glial cells, but they were likely responsible for the decrease in zebrafish hatching rate. The results obtained in this work contribute to the knowledge of the toxicological potential of ZnO NPs.

Biocompatibility of a Ti-Rich Medium-Entropy Alloy with Glioblastoma Astrocytoma Cells

Titanium and titanium alloys are widely used in medical devices and implants; thus, the biocompatibility of these metals is of great importance. In this study, glioblastoma astrocytoma cellular responses to Ti₆₅-Zr₁₈-Nb₁₆-Mo₁ (Ti65M, metastable medium-entropy alloy), Ti-13Nb-7Sn-4Mo (TNSM, titanium alloy), and commercially pure titanium (CP-Ti) were studied. Several physical parameters (crystal phase structure, surface roughness and hardness) of the titanium alloys were measured, and the correlation with the cellular viability was investigated. Finally, the relative protein expression in cellular proliferation pathways was measured and compared with mRNA expression assessed with quantitative real-time reverse transcription polymerase chain reaction assay (qRT-PCR).

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.

Functionalized Titanium Nanoparticles Induce Oxidative Stress and Cell Death in Human Skin Cells

Purpose

Methods

Results

Conclusion

Tungsten disulfide nanotubes enhance flow-induced crystallization and radio-opacity of polylactide without adversely affecting in vitro toxicity

Treatment of vascular disease, from peripheral ischemia to coronary heart disease (CHD), is poised for transformation with the introduction of transient implants designed to "scaffold" regeneration of blood vessels and ultimately leave nothing behind. Improved materials could expand the use of these devices. Here, we examine one of the leading polymers for bioresorbable scaffolds (BRS), polylactide (PLA), as the matrix of nanocomposites with tungsten disulfide (WS₂) nanotubes (WSNT), which may provide mechanical reinforcement and enhance radio-opacity. We evaluate in vitro cytotoxicity using vascular cells, flow-induced crystallization and radio-opacity of PLA-WSNT nanocomposites at low WSNT concentration. A small amount of WSNT (0.1 wt%) can effectively promote oriented crystallization of PLA without compromising molecular weight. And radio-opacity improves significantly: as little as 0.5 to 1 wt% WSNT doubles the radio-opacity of PLA-WSNT relative to PLA at 17 keV. The results suggest that a single component, WSNT, has the potential to increase the strength of BRS to enable thinner devices and increase radio-opacity to improve intraoperative visualization. The in vitro toxicity results indicate that PLA-WSNT nanocomposites are worthy of investigation in vivo. Although substantial further preclinical studies are needed, PLA-WSNT nanocomposites may provide a complement of material properties that may improve BRS and expand the range of lesions that can be treated using transient implants. STATEMENT OF SIGNIFICANCE: Bioresorbable Scaffolds (BRSs) support regeneration of arteries without permanent mechanical constraint. Poly-L-lactide (PLLA) is the structural material of the first approved BRS for coronary heart disease (ABSORB BVS), withdrawn due to adverse events in years 1-3. Here, we examine tungsten disulfide (WS₂) nanotubes (WSNT) in PLA to address two contributors to early complications: (1) reinforce PLLA (enable thinner BRS), and (2) increase radiopacity (provide intraoperative visibility). For BRS, it is significant that WSNT disperse, remain dispersed, reduce friction and improve mechanical properties without additional chemicals or surface modifications. Like WS₂ nanospheres, bare WSNT and PLA-WSNT nanocomposites show low cytotoxicity in vitro. PLA-WSNT show enhanced flow-induced crystallization relative to PLA, motivating future study of the processing behavior and strength of these materials.

In vitro Investigation of the Antimicrobial Activity of Mouth Washes Incorporating Zein-Coated Magnesium Oxide Nanoparticles

PURPOSE

This in vitro study was undertaken to investigate the antimicrobial effect of distinctive oral mouth washes after the addition of zein-coated (Magnesium oxide) MgO nanoparticles on exemplary of some oral microorganisms.

MATERIALS AND METHODS

Three hundred and twelve samples were used in this study. A set of five concentrations of MgO nanoparticles with zein and without zein-coating were incorporated into three oral mouth washes: Listerine zero, Listerine total control and Oral B in the mass percentages of 0.3%, 0.5%, 1%, 2%, 5% and 10%, in addition to controls with no MgO nanoparticles. The antimicrobial effect of three mouth washes with variable concentrations of MgO was tested against the following organisms: Staphylococcus aureus, Streptococcus mutans, Enterococcus faecalis and Candida albicans using the disc diffusion test (DDT) and direct contact test (DCT). Data were analyzed using one-way ANOVA statistical test.

RESULTS

The tested mouthwashes with zein-coated MgO nanoparticles showed significant differences of antimicrobial activity on S. mutans, S. aureus, E. faecalis, and C. albicans in the disc diffusion test. While in the DCT, all tested mouthwashes with MgO nanoparticles with and without zein coating showed antimicrobial activity on all tested microorganisms.

CONCLUSION

Zein-coated MgO nanoparticles may be considered as a potential antimicrobial agent when added to oral mouthwashes. Future analysis, including in vivo studies, is required in order to incorporate zein/MgO nanoparticles into oral mouthwashes that may improve its antibacterial property.

Apigenin exerts chemopreventive effects on lung injury induced by SiO2 nanoparticles through the activation of Nrf2

Apigenin (APG) is a flavonoid widely distributed in fruits, vegetables, and herbs, with comprehensive pharmacological effects. In this paper, we report that APG can elicit a protective effect, which is comparable to those induced by gymnoside II/n-BuOH extracts of Bletilla striata, on SiO₂-induced lung injury in vitro and in vivo. In vitro experiments showed that APG (25 μM) could restore the SiO₂-decreased A549 cell viability and lower the apoptotic rate and the production of intracellular reactive oxygen species (ROS) in A549 cells treated with nm SiO₂. Western blot results showed that APG (25 μM) could increase the level of Nuclear factor E2-related factor 2 (Nrf2) and its downstream proteins. In vivo experiments showed that APG (20 mg/kg) could potently alleviate the SiO₂-elicited lung injury by enhancing the Nrf2 expression and thereby suppressing Bax/Bcl-2 pathway. The present study suggests that APG can significantly alleviate the SiO₂-induced lung injury both in vitro and in vivo through, at least partially, activating Nrf2 expression.

Titanium Dioxide, but Not Zinc Oxide, Nanoparticles Cause Severe Transcriptomic Alterations in T98G Human Glioblastoma Cells

Titanium dioxide and zinc oxide are two of the most widely used nanomaterials. We assessed the effects of noncytotoxic doses of both nanomaterials on T98G human glioblastoma cells by omic approaches. Surprisingly, no effects on the transcriptome of T98G cells was detected after exposure to 5 µg/mL of zinc oxide nanoparticles during 72 h. Conversely, the transcriptome of the cells exposed to 20 µg/mL of titanium dioxide nanoparticles during 72 h revealed alterations in lots of biological processes and molecular pathways. Alterations to the transcriptome suggests that exposure to titanium dioxide nanoparticles might, potentially, compromise the integrity of the blood brain barrier integrity and cause neuroinflammation. The latter issue was further confirmed phenotypically with a proteomic analysis and by recording the release of interleukin 8. Titanium dioxide also caused autophagy, which was demonstrated through the increase in the expression of the autophagy-related 3 and microtubule associated protein 1 light chain 3 alpha genes. The proteomic analysis revealed that titanium dioxide nanoparticles might have anticancerigen properties by downregulating genes involved in the detoxication of anthracyclines. A risk assessment resulting from titanium dioxide exposure, focusing on the central nervous system as a potential target of toxicity, is necessary.

The Influence of ZnO Oxide Layer on the Physicochemical Behavior of Ti6Al4V Titanium Alloy

Titanium and its alloys are characterized by high biocompatibility and good corrosion resistance as a result of the ability to form a TiO₂ oxide layer. However, based on literature data it can be concluded that titanium degradation products, in the form of titanium particles, metal-protein groups, oxides and ions, may cause allergic, inflammatory reactions and bone resorption. The corrosion process of Ti6Al4V in the human body environment may be intensified by a decreased pH and concentration of chloride compounds. The purpose of this article was to analyze the corrosion resistance of the Ti6Al4V alloy, obtained by the selective laser melting method in a corrosion solution of neutral pH and in a solution simulating peri-implant inflammatory conditions. Additionally, the influence of zinc oxide deposited by the atomic layer deposition method on the improvement of the physicochemical behavior of the Ti6Al4V alloy was analyzed. In order to characterize the ZnO layer, tests of chemical and phase composition as well as surface morphology investigation were performed. As part of the assessment of the physicochemical properties of the uncoated samples and those with the ZnO layer, tests of wetting angle, pitting corrosion and impedance corrosion were carried out. The number of ions released after the potentiodynamic test were measured using the inductively coupled plasma atomic emission spectrometry (ICP-AES) method. It can be concluded that samples after surface modification (with the ZnO layer) were characterized by favorable physicochemical properties and had higher corrosion resistance.

Green Synthesis of Mg0.99 Zn0.01O Nanoparticles for the Fabrication of κ-Carrageenan/NaCMC Hydrogel in order to Deliver Catechin

Currently, the role of the nanoparticles in the structure of the composites and their benefits for the health of the body is valuable. In this study, the effects of the doping on the structural and morphological properties of the hydrogels using a Mg co-doped ZnO hydrogel, which has been fabricated by the sol–gel process, have been investigated. Then, a hydrogel containing nanoparticle and a hydrogel without any nanoparticles was produced as a control. The hydrogels were loaded with catechin and the related characterization was evolved based on the new structure of the matrices. The Mg_0.99Zn_0.01O nanoparticles were synthesized using a green synthesis method. To investigate the properties of the nanoparticles, zeta potential and XRD were studied. The field emission scanning electron microscopy (FESEM), FTIR, TGA, swelling Ratio, and compression tests were investigated for the hydrogels. Based on the results, FESEM showed a more compressed structure for hydrogels including nanoparticles rather than the hydrogels without a nanoparticle. The TGA showed a higher decomposition temperature in the hydrogels including nanoparticles. The swelling ratio of hydrogels containing a nanoparticle was higher than the control hydrogel. κ-Carrageenan/ Mg_0.99Zn_0.01O/NaCMC/Catechin had the highest swelling ratio (44.15%) rather than the κ-Carrageenan/NaCMC (33.22%). Mg_0.99Zn_0.01O nanoparticles presented a stronger structure of hydrogels in the compression test. It is concluded that the role of the synthesized nanoparticle is critical in the structure of the hydrogel.

Particle-size dependent bactericidal activity of magnesium oxide against Xanthomonas perforans and bacterial spot of tomato

Bacterial spot, caused by Xanthomonas spp., is a highly destructive disease of tomatoes worldwide. Copper (Cu) bactericides are often ineffective due to the presence of Cu-tolerant strains. Magnesium oxide (MgO) is an effective alternative to Cu bactericides against Xanthomonas spp. However, the effects of particle size on bactericidal activity and fruit elemental levels are unknown. In this study, nano (20 nm) and micron (0.3 and 0.6 µm) size MgO particles were compared for efficacy. Nano MgO had significantly greater in vitro bactericidal activity against Cu-tolerant X. perforans than micron MgO at 25–50 µg/ml. In field experiments nano and micron MgO applied at 200 and 1,000 µg/ml were evaluated for disease control. Nano MgO at 200 µg/ml was the only treatment that consistently reduced disease severity compared to the untreated control. Inductively Coupled Plasma Optical Emission Spectroscopy revealed that nano MgO applications did not significantly alter Mg, Cu, Ca, K, Mn, P and S accumulation compared to fruits from the untreated plots. We demonstrated that although both nano MgO and micron MgO had bactericidal activity against Cu-tolerant strains in vitro, only nano MgO was effective in bacterial spot disease management under field conditions.

Mechanoregulation of titanium dioxide nanoparticles in cancer therapy

Titanium dioxide (TiO₂) nanoparticles (NPs), first developed in the 1990s, have been applied in numerous biomedical fields such as tissue engineering and therapeutic drug development. In recent years, TiO₂-based drug delivery systems have demonstrated the ability to decrease the risk of tumorigenesis and improve cancer therapy. There is increasing research on the origin and effects of pristine and doped TiO₂-based nanotherapeutic drugs. However, the detailed molecular mechanisms by which drug delivery to cancer cells alters sensing of gene mutations, protein degradation, and metabolite changes as well as its associated cumulative effects that determine the microenvironmental mechanosensitive metabolism have not yet been clearly elucidated. This review focuses on the microenvironmental influence of TiO₂-NPs induced various mechanical stimuli on tumor cells. The differential expression of genome, proteome, and metabolome after treatment with TiO₂-NPs is summarized and discussed. In the tumor microenvironment, mechanosensitive DNA mutations, gene delivery, protein degradation, inflammatory responses, and cell viability affected by the mechanical stimuli of TiO₂-NPs are also examined.

Nanoparticles in Construction Materials and Other Applications, and Implications of Nanoparticle Use

Nanoparticles are defined as ultrafine particles sized between 1 and 100 nanometres in diameter. In recent decades, there has been wide scientific research on the various uses of nanoparticles in construction, electronics, manufacturing, cosmetics, and medicine. The advantages of using nanoparticles in construction are immense, promising extraordinary physical and chemical properties for modified construction materials. Among the many different types of nanoparticles, titanium dioxide, carbon nanotubes, silica, copper, clay, and aluminium oxide are the most widely used nanoparticles in the construction sector. The promise of nanoparticles as observed in construction is reflected in other adoptive industries, driving the growth in demand and production quantity at an exorbitant rate. The objective of this study was to analyse the use of nanoparticles within the construction industry to exemplify the benefits of nanoparticle applications and to address the short-term and long-term effects of nanoparticles on the environment and human health within the microcosm of industry so that the findings may be generalised. The benefits of nanoparticle utilisation are demonstrated through specific applications in common materials, particularly in normal concrete, asphalt concrete, bricks, timber, and steel. In addition, the paper addresses the potential benefits and safety barriers for using nanomaterials, with consideration given to key areas of knowledge associated with exposure to nanoparticles that may have implications for health and environmental safety. The field of nanotechnology is considered rather young compared to established industries, thus limiting the time for research and risk analysis. Nevertheless, it is pertinent that research and regulation precede the widespread adoption of potentially harmful particles to mitigate undue risk.

Incorporation of Glycine max Merrill Extract into Layered Double Hydroxide through Ion-Exchange and Reconstruction

We incorporated extract of Glycine max Merrill (GM), which is generally known as soybean, into a layered double hydroxide (LDH) nanostructure through two different methods, ion-exchange and reconstruction. Through X-ray diffraction, field-emission scanning electron microscopy, and zeta-potential measurement, GM moiety seemed to be simply attached on the surface of LDH by ion-exchange process, while the extract could be incorporated in the inter-particle pore of LDHs by reconstruction reaction. The quantification exhibited that both incorporation method showed comparable extract loading capacity of 15.6 wt/wt% for GM-LDH hybrid prepared by ion-exchange (GML-I) and 18.6 wt/wt% for GM-LDH hybrid by reconstruction (GML-R). On the other hand, bioactive substance in both GM-LDH hybrids, revealed that GML-R has higher daidzein content (0.0286 wt/wt%) compared with GML-I (0.0108 wt/wt%). According to time-dependent daidzein release, we confirmed that GML-R showed pH dependent daidzein release; a higher amount of daidzein was released in pH 4.5 physiological condition than in pH 7.4, suggesting the drug delivery potential of GML-R. Furthermore, alkaline phosphatase activity and collagen fiber formation on human osteoblast-like MG-63 cells displayed that GML-R had superior possibility of osteoblast differentiation than GML-I. From these results, we concluded that reconstruction method was more effective for extract incorporation than ion-exchange reaction, due to its pH dependent release property and alkaline phosphatase activity.

Elevated Systemic L-Kynurenine/L-Tryptophan Ratio and Increased IL-1 Beta and Chemokine (CX3CL1, MCP-1) Proinflammatory Mediators in Patients with Long-Term Titanium Dental Implants

Titanium is the mean biocompatible metal found in dental titanium alloys (Ti-6Al-4V). The safety of certain dental biomaterial amalgams has been questioned in patients. The levels of several systemic cytokines (interleukin (IL)-1 beta, IL-4: pg/mL) and chemokines (monocyte chemoattractant protein-1 (MCP-1), soluble fractalkine (CX3CL1: pg/mL) were determined using ELISA and compared between these study groups. The study included 30 controls without dental materials (cont), 57 patients with long-term titanium dental implants plus amalgams (A + I group) as well as 55 patients with long-term dental amalgam alone (A group). All patients (except controls) have had dental titanium implants (Ti-6Al-4V) and/or amalgams for at least 10 years (average: 15 years). We evaluated whether systemic levels of cytokines/chemokines, kyn/L-trp ratio and aromatic amino acid levels (HPLC: mM/L, Phe, L-Trp, His, Treo) could be altered in patients with long-term dental titanium and/or amalgams. These systemic markers were evaluated in 142 patients. The A + I group had higher L-Kynurenine/L-Tryptophan ratios than patients with long-term dental amalgam fillings alone (A). In addition, levels of IL-1 Beta cytokine, CX3CL1 and MCP-1 chemokines were higher in the A + I group than in the A group (A). The increased L-kyn/L-trp ratio and MCP-1 and fractalkine receptor (CX3CR1) elevations could suggest enhanced chemotactic responses by these chemokines in the A + I group.

Increased Systemic Malondialdehyde Levels and Decreased Mo/Co, Co/Fe2+ Ratios in Patients with Long-Term Dental Titanium Implants and Amalgams

INTRODUCTION

the biological safety of dental biomaterials has been questioned in human studies.

MATERIAL AND METHODS

Several heavy metals/oligoelements were compared by Inductive Coupled Mass Spectrometry (ICP-MS) in hair samples from 130 patients (n = 54 patients with long-term titanium dental implants and amalgams (A + I group), 51 patients with long-term dental amalgam alone (A group), as well as controls (n = 25: without dental materials) of similar age. All patients (except controls) had had titanium dental implants and/or dental amalgams for at least 10 years (average: 17). We evaluated whether A + I patients could present higher systemic malondialdehyde levels (MDA) as compared to the A group.

RESULTS

The A + I group have lower molybdenum levels (A + I) and reduced Mo/Co and Mo/Fe²⁺ ratios, which could predispose them to oxidative stress by raising MDA levels as compared to the A group alone; our findings suggest that higher Co levels could enhance oxidative stress in the A + I group. However, there were no differences on metals from titanium alloy (Ti-6Al), Cr from crowns or Hg²⁺, Sn, Zn²⁺, Cu²⁺ levels between the A + I and A groups.

CONCLUSION

patients with long-term dental titanium and amalgams have systemic oxidative stress due to rising MDA levels and lower Mo/Co and Mo/Fe²⁺ ratios than those with amalgams alone.

In vivo Toxicity Investigation of Magnesium Oxide Nanoparticles in Rat for Environmental and Biomedical Applications

Background

Magnesium oxide nanoparticles are characterized with a wide variety of applications and are mass-produced throughout the world. However, questions remain regarding their safety. There has been paucity of toxicology research on their side effects, especially under in vivo conditions.

Objectives

The present paper aims at evaluating the toxicity of administering 10–15 nm magnesium oxide nanoparticles to Wistar rat under in vivo conditions. In addition, hematology, biochemistry, and histopathology of the rats are examined at various concentrations (62.5-125-250-500 μg.mL^-1) over 28-days period.

Materials and Methods

In this study, 35 male Wistar rats were randomly divided into five groups, comprising one control group and four experimental groups, assigned to various doses of MgO nanoparticles by intraperitoneal injection. Eventually, blood samples were collected, and all animals were sacrificed for liver and kidney tissue investigation.

Results

The findings showed that high concentrations of Magnesium oxide nanoparticles (250 and 500 μg.mL^-1) significantly increased white blood cells, red blood cells, hemoglobin, and hematocrit compared with the control group (P < 0.05). Moreover, the nanoparticles elevated the levels of aspartate aminotransferase and alkaline phosphatase, whereas no significant difference in levels of alanine aminotransferase, gamma-glutamyl transpeptidase, urea, and creatinine were recorded in comparison with the control group (P < 0.05). Histopathological examinations in the rat’s liver showed proliferation of bile ductules, congestion in some regions of the liver sinusoids, and apoptotic cells (probably) in high-dose groups, but no histological changes were found in the kidney functions.

Conclusions

The results from the present study showed that the magnesium oxide nanoparticles in concentrations lower than 250 μg.mL^-1 are safe for desired applications.

Biological Impact of Exposure to Extremely Fine-Grained Volcanic Ash

At the northwestern edge of South America is located Ecuador. This place is a classical example of an active continental margin with widespread active volcanism. Detailed studies about the impact of volcanic ash on human health are still lacking. Therefore, the disease of exposed populations is unknown. The objective of the present investigation was to assess the biological impact of Pichincha volcanic ash on cell culture and inflammation in murine lung tissues that will contribute to the understanding of the hazards. In this study, the in vivo phase was performed in mice C57BL/6 exposed to several doses of volcanic ash (0.5, 1, and 3.75 mg/100 g mouse body weight). The body weight and survival were controlled during seven days of treatment. The expression of inflammation markers NRLP 3, caspase-1, pro-IL-1, IL-1β, IL-6, IL-8, and h-HPRT was analyzed. The in vitro phase was performed in lung cancer cells A549, peritoneal macrophages, and McCoy cells exposing them to different concentrations of volcanic ash (80, 320, and 1280 μg/cm3) to determine the cytotoxicity and the production of reactive oxygen species. The ash initiated activation of the inflammasome complex NRLP 3 and the initiation of a proinflammatory activity in the murine lung tissue depending on the concentration of this agent. The viability of A549 and McCoy cell decreased with the length of exposure and increased with the concentration of volcanic ash. The activity in superoxide dismutase decreased by about 60%, leading to the formation of reactive oxygen species. These results associated with compounds contained in Pichincha volcanic ash are considered hazardous elements which induce inflammation leading to activate inflammasome NRLP, releasing reactive oxygen species, and producing changes in cell morphology and density, all of which are expression of cytotoxicity.

Antiangiogenic and antiapoptotic effects of green-synthesized zinc oxide nanoparticles using Sargassum muticum algae extraction

Background

Algae are one of the natural materials used to green synthesis of nanoparticles. This method leads to minimize the toxicity of the chemical materials used to nanoparticle synthesis.

Methods

In this study, zinc oxide nanoparticles (ZnO NPs) synthesized by Sargassum muticum algae extraction used to evaluate its cytotoxicity and apoptotic properties on human liver cancer cell line (HepG2).

Results

Trypan blue assay results demonstrate a concentration-dependent decrease in cell viability and MTT assay shows increased growth inhibition in time and dose-dependent manner. In addition, CAM assay confirmed the ability of ZnO NPs to inhibit angiogenesis, but chick morphology (both the CR and weight) was not changed. Apoptotic tests (annexin V/PI and AO/PI) show that green-synthesized ZnO NPs induce apoptosis in all three time points (24, 48 and 72h).

Conclusions

Our results confirm the beneficial cytotoxic effects of green-synthesized ZnO NPs on Human liver cancer cell. This nanoparticle decreased angiogenesis and induces apoptosis, so we conclude that these nanoparticles can be used as a supplemental drug in cancer treatments.

Assessment of DNA Damage During Gene Delivery in Freshwater Prawn by Chitosan Reduced Gold Nanoparticles

The increasing application of nanoparticles both in industries and in agricultural fields has led to its accumulation in the aquatic ecosystem through water run-off. Insights into the validity of safer nanoparticles such as gold and chitosan are fairly established. However, its effect on aquatic invertebrates has been less studied. The present study was aimed to study effects of chitosan reduced gold nanoparticles (CRGNPs) during green fluorescent protein (GFP) encoding plasmid delivery in giant freshwater prawn, macrobrachium rosenbergii. The mean particle size and zeta potential CRGNPs was 33.7 nm and 24.79 mV respectively. Prawn juveniles were exposed to nanoparticles concentrations (10 µg/L, 20 µg/L) of CRGNPs by immersion treatment for a period of 36 hours. GFP was ubiquitously expressed in muscle tissues of prawns. The comet assay indicated dose dependent genotoxicity of CRGNPs in gill, pleopod and muscle tissues which was in conformity with its bioaccumulation pattern in vivo. The highest bioaccumulation of CRGNPs was found in Gills, followed by pleopods and least in muscles. Hence, the toxicological potential of CRGNPs to the environment cannot be denied and demands more research on the particular aspect. The doses standardized in the present study would be helpful in safer nano-gene delivery in aquatic invertebrates and development of transgenics employing less cost.

TiO2 nanoparticles induce omphalocele in chicken embryo by disrupting Wnt signaling pathway

Titanium dioxide nanoparticles (TiO₂ NPs) are among abundantly used metal oxide NPs but their interactions with biomolecules and subsequent embryonic toxicity in higher vertebrates is not extensively reported. Physicochemical interactions of TiO₂ NPs with egg albumen reveals that lower doses of TiO₂ NPs (10 and 25 µg/ml) accounted for higher friccohesity and activation energy but an increment in molecular radii was recorded at higher doses (50 and 100 µg/ml). FTIR analysis revealed conformational changes in secondary structure of egg albumen as a result of electrostratic interactions between egg albumen and TiO₂ NPs. The morphometric data of chicken embryo recorded a reduction at all the doses of TiO₂ NPs, but toxicity and developmental deformity (omphalocele and flexed limbs) were recorded at lower doses only. Inductively coupled plasma optical emission spectrometry (ICP-OES) confirmed presence of Ti in chicken embryos. mRNA levels of genes involved in canonical and non-canonical Wnt signaling were lowered following TiO₂ NPs treatment resulting in free radical mediated disruption of lateral plate mesoderm and somite myogenesis. Conformational changes in egg albumen and subsequent developmental deformity in chicken embryo following TiO₂ NPs treatment warrants detailed studies of NP toxicity at lower doses prior to their biomedical applications.

Toxicity of nanotitanium dioxide (TiO2-NP) on human monocytes and their mitochondria

The effect of nanotitanium dioxide (TiO₂-NP) in human monocytes is still unknown. Therefore, an understanding of probable cytotoxicity of TiO₂-NP on human monocytes and underlining the mechanisms involved is of significant interest. The aim of this study was to assess the cytotoxicity of TiO₂-NP on human monocytes. Using biochemical and flow cytometry assessments, we demonstrated that addition of TiO₂-NP at 10 μg/ml concentration to monocytes induced cytotoxicity following 12 h. The TiO₂-NP-induced cytotoxicity on monocytes was associated with intracellular reactive oxygen species (ROS) generation, mitochondrial membrane potential (MMP) collapse, lysosomal membrane injury, lipid peroxidation, and depletion of glutathione. According to our results, TiO₂-NP triggers oxidative stress and organelles damages in monocytes which are important cells in defense against foreign agents. Finally, our findings suggest that use of antioxidants and mitochondrial/lysosomal protective agents could be of benefit for the people in the exposure with TiO₂-NP.

Nanoparticles of Titanium and Zinc Oxides as Novel Agents in Tumor Treatment: a Review

Cancer has become a global problem. On all continents, a great number of people are diagnosed with this disease. In spite of the progress in medical care, cancer still ends fatal for a great number of the ill, either as a result of a late diagnosis or due to inefficiency of therapies. The majority of the tumors are resistant to drugs. Thus, the search for new, more effective therapy methods continues. Recently, nanotechnology has been attributed with big expectations in respect of the cancer fight. That interdisciplinary field of science creates nanomaterials (NMs) and nanoparticles (NPs) that can be applied, e.g., in nanomedicine. NMs and NPs are perceived as very promising in cancer therapy since they can perform as drug carriers, as well as photo- or sonosensitizers (compounds that generate the formation of reactive oxygen species as a result of either electromagnetic radiation excitation with an adequate wavelength or ultrasound activation, respectively). Consequently, two new treatment modalities, the photodynamic therapy (PDT) and the sonodynamic therapy (SDT) have been created. The attachment of ligands or antibodies to NMs or to NPs improve their selective distribution into the targeted organ or cell; hence, the therapy effectiveness can be improved. An important advantage of the targeted tumor treatment is lowering the cyto- and genotoxicity of active substance towards healthy cells. Therefore, both PDT and SDT constitute a valuable alternative to chemo- or radiotherapy. The vital role in cancer eradication is attributed to two inorganic sensitizers in their nanosized scale: titanium dioxide and zinc oxide.

Zinc oxide nanoparticles induce apoptosis and autophagy in human ovarian cancer cells

Background

Zinc oxide nanoparticles (ZnO NPs) are frequently used in industrial products such as paint, surface coating, and cosmetics, and recently, they have been explored in biologic and biomedical applications. Therefore, this study was undertaken to investigate the effect of ZnO NPs on cytotoxicity, apoptosis, and autophagy in human ovarian cancer cells (SKOV3).

Methods

ZnO NPs with a crystalline size of 20 nm were characterized with various analytical techniques, including ultraviolet-visible spectroscopy, X-ray diffraction, transmission electron microscopy, Fourier transform infrared spectroscopy, and atomic force microscopy. The cytotoxicity, apoptosis, and autophagy were examined using a series of cellular assays.

Results

Exposure of cells to ZnO NPs resulted in a dose-dependent loss of cell viability, and the characteristic apoptotic features such as rounding and loss of adherence, enhanced reactive oxygen species generation, and loss of mitochondrial membrane potential were observed in the ZnO NP-treated cells. Furthermore, the cells treated with ZnO NPs showed significant double-strand DNA breaks, which are gained evidences from significant number of γ-H₂AX and Rad51 expressed cells. ZnO NP-treated cells showed upregulation of p53 and LC3, indicating that ZnO NPs are able to upregulate apoptosis and autophagy. Finally, the Western blot analysis revealed upregulation of Bax, caspase-9, Rad51, γ-H₂AX, p53, and LC3 and downregulation of Bcl-2.

Conclusion

The study findings demonstrated that the ZnO NPs are able to induce significant cytotoxicity, apoptosis, and autophagy in human ovarian cells through reactive oxygen species generation and oxidative stress. Therefore, this study suggests that ZnO NPs are suitable and inherent anticancer agents due to their several favorable characteristic features including favorable band gap, electrostatic charge, surface chemistry, and potentiation of redox cycling cascades.

Effects of Metal Micro and Nano-Particles on hASCs: An In Vitro Model

As the knowledge about the interferences of nanomaterials on human staminal cells are scarce and contradictory, we undertook a comparative multidisciplinary study based on the size effect of zero-valent iron, cobalt, and nickel microparticles (MPs) and nanoparticles (NPs) using human adipose stem cells (hASCs) as a model, and evaluating cytotoxicity, morphology, cellular uptake, and gene expression. Our results suggested that the medium did not influence the cell sensitivity but, surprisingly, the iron microparticles (FeMPs) resulted in being toxic. These data were supported by modifications in mRNA expression of some genes implicated in the inflammatory response. Microscopic analysis confirmed that NPs, mainly internalized by endocytosis, persist in the vesicles without any apparent cell damage. Conversely, MPs are not internalized, and the effects on hASCs have to be ascribed to the release of ions in the culture medium, or to the reduced oxygen and nutrient exchange efficiency due to the presence of MP agglomerating around the cells. Notwithstanding the results depicting a heterogeneous scene that does not allow drawing a general conclusion, this work reiterates the importance of comparative investigations on MPs, NPs, and corresponding ions, and the need to continue the thorough verification of NP and MP innocuousness to ensure unaffected stem cell physiology and differentiation.

ZnO Nano-Rod Devices for Intradermal Delivery and Immunization

Intradermal delivery of antigens for vaccination is a very attractive approach since the skin provides a rich network of antigen presenting cells, which aid in stimulating an immune response. Numerous intradermal techniques have been developed to enhance penetration across the skin. However, these methods are invasive and/or affect the skin integrity. Hence, our group has devised zinc oxide (ZnO) nano-rods for non-destructive drug delivery. Chemical vapour deposition was used to fabricate aligned nano-rods on ZnO pre-coated silicon chips. The nano-rods’ length and diameter were found to depend on the temperature, time, quality of sputtered silicon chips, etc. Vertically aligned ZnO nano-rods with lengths of 30–35 µm and diameters of 200–300 nm were selected for in vitro human skin permeation studies using Franz cells with Albumin-fluorescein isothiocyanate (FITC) absorbed on the nano-rods. Fluorescence and confocal studies on the skin samples showed FITC penetration through the skin along the channels formed by the nano-rods. Bradford protein assay on the collected fluid samples indicated a significant quantity of Albumin-FITC in the first 12 h. Low antibody titres were observed with immunisation on Balb/c mice with ovalbumin (OVA) antigen coated on the nano-rod chips. Nonetheless, due to the reduced dimensions of the nano-rods, our device offers the additional advantage of excluding the simultaneous entrance of microbial pathogens. Taken together, these results showed that ZnO nano-rods hold the potential for a safe, non-invasive, and painless intradermal drug delivery.

Assessment of Crystal Morphology on Uptake, Particle Dissolution, and Toxicity of Nanoscale Titanium Dioxide on Artemia salina

Knowledge of nanomaterial toxicity is critical to avoid adverse effects on human and environment health. In this study, the influences of crystal morphology on physico-chemical and toxic properties of nanoscale TiO2 (n-TiO2) were investigated. Artemia salina were exposed to anatase, rutile and mixture polymorphs of n-TiO2 in seawater. Short-term (24 h) and long-term (96 h) exposures were conducted in 1, 10 and 100 mg/L suspensions of n-TiO2 in the presence and absence of food. Anatase form had highest accumulation followed by mixture and rutile. Presence of food greatly reduced accumulation. n-TiO2 dissolution was not significant in seawater (p<0.05) nor was influenced from crystal structure. Highest toxic effects occurred in 96h exposure in the order of anatase > mixture > rutile. Mortality and oxidative stress levels increased with increasing n-TiO2 concentration and exposure time (p<0.05). Presence of food in the exposure medium alleviated the oxidative stress, indicating that deprivation from food could promote toxic effects of n-TiO2 under long-term exposure.

Single and combined effects of aluminum (Al2O3) and zinc (ZnO) oxide nanoparticles in a freshwater fish, Carassius auratus

The increasing use of nanoparticles (NPs) worldwide has raised some concerns about their impact on the environment. The aim of the study was to assess the toxicity of metal oxide nanoparticles, singly or combined, in a freshwater fish (Carassius auratus). The fish were exposed for 7, 14, and 21 days to different concentrations of NPs (10 μg Al₂O₃.L^-1, 10 μg ZnO.L^-1, 10 μg Al₂O₃.L^-1 plus 10 μg ZnO.L^-1, 100 μg Al₂O₃.L^-1, 100 μg ZnO.L^-1, and 100 μg Al₂O₃.L^-1 plus 100 μg ZnO.L^-1). At the end of each exposure period, antioxidant enzyme activity (catalase, glutathione-S-transferase, and superoxide dismutase), lipid peroxidation, and histopathology were assessed in the gills and livers of C. auratus. The results show an increase in catalase (CAT) and superoxide dismutase (SOD) activity in the gills and livers of fish, especially after 14 days of exposure to single and combined NPs, followed by a reduction at 21 days. An increase in glutathione S-transferase (GST) was observed in gills after 7 days for all tested NP concentrations (single and combined); while in livers, a significant increase was determined after 14 days of exposure to 100 μg.L^-1 of both single ZnO and Al₂O₃ NPs. Lipid peroxidation (LPO) significantly increased in gills after 7 days of exposure to 100 μg.L^-1 Al₂O₃ NPs (single or combined). In livers, LPO increased significantly after 7 days of exposure to all tested concentrations of both single ZnO and Al₂O₃ (except for 10 μg Al₂O₃.L^-1), and after 14 days of exposure to ZnO (10 and 100 μg.L^-1) and Al₂O₃ (100 μg.L^-1)_. The results from histological observations suggest that exposure to metal oxide NPs affected both livers and gills, presenting alterations such as gill hyperplasia and liver degeneration. However, the most pronounced effects were found in gills. In general, this study shows that the tested NPs, single or combined, are capable of causing sub-lethal effects on C. auratus, but when combined, NPs seem to be slightly more toxic than when added alone.

Involvement of Programmed Cell Death in Neurotoxicity of Metallic Nanoparticles: Recent Advances and Future Perspectives

The widespread application of metallic nanoparticles (NPs) or NP-based products has increased the risk of exposure to NPs in humans. The brain is an important organ that is more susceptible to exogenous stimuli. Moreover, any impairment to the brain is irreversible. Recently, several in vivo studies have found that metallic NPs can be absorbed into the animal body and then translocated into the brain, mainly through the blood-brain barrier and olfactory pathway after systemic administration. Furthermore, metallic NPs can cross the placental barrier to accumulate in the fetal brain, causing developmental neurotoxicity on exposure during pregnancy. Therefore, metallic NPs become a big threat to the brain. However, the mechanisms underlying the neurotoxicity of metallic NPs remain unclear. Programmed cell death (PCD), which is different from necrosis, is defined as active cell death and is regulated by certain genes. PCD can be mainly classified into apoptosis, autophagy, necroptosis, and pyroptosis. It is involved in brain development, neurodegenerative disorders, psychiatric disorders, and brain injury. Given the pivotal role of PCD in neurological functions, we reviewed relevant articles and tried to summarize the recent advances and future perspectives of PCD involvement in the neurotoxicity of metallic NPs, with the purpose of comprehensively understanding the neurotoxic mechanisms of NPs.

Pure and multi metal oxide nanoparticles: synthesis, antibacterial and cytotoxic properties

Th antibacterial activity of metal oxide nanoparticles has received marked global attention as they can be specifically synthesized to exhibit significant toxicity to bacteria. The importance of their application as antibacterial agents is evident keeping in mind the limited range and effectiveness of antibiotics, on one hand, and the plethora of metal oxides, on the other, along with the propensity of nanoparticles to induce resistance being much lower than that of antibiotics. Effective inhibition against a wide range of bacteria is well known for several nano oxides consisting of one metal (Fe₃O₄, TiO₂, CuO, ZnO), whereas, research in the field of multi-metal oxides still demands extensive exploration. This is understandable given that the relationship between physicochemical properties and biological activity seems to be complex and difficult to generalize even for metal oxide nanoparticles consisting of only one metal component. Also, despite the broad scope that metal oxide nanoparticles have as antibacterial agents, there arise problems in practical applications taking into account the cytotoxic effects. In this respect, the consideration of polymetallic oxides for biological applications becomes even greater since these can provide synergetic effects and unify the best physicochemical properties of their components. For instance, strong antibacterial efficiency specific of one metal oxide can be complemented by non-cytotoxicity of another. This review presents the main methods and technological advances in fabrication of nanostructured metal oxides with a particular emphasis to multi-metal oxide nanoparticles, their antibacterial effects and cytotoxicity.

Molecular Mechanism of Silver Nanoparticles-Induced Human Osteoblast Cell Death: Protective Effect of Inducible Nitric Oxide Synthase Inhibitor

BACKGROUND

Silver nanoparticles (AgNPs) show strong antibacterial properties, making them excellent candidates to be used in orthopaedic repair and regeneration. However, there are concerns regarding the cytotoxicity of AgNPs and molecular mechanisms underlying AgNPs-induced bone cells toxicity have not been elucidated. Therefore, the aim of our study was to explore mechanisms of AgNPs-induced osteoblast cell death with particular emphasis on the role of nitric oxide (NO) generated by inducible nitric oxide synthase (iNOS).

METHODS AND RESULT

Silver nanoparticles used in this study were 18.3±2.6 nm in size, uncoated, spherical, regular shape and their zeta potential was -29.1±2.4 mV as measured by transmission electron microscopy (TEM) and zetasizer. The release of silver (Ag) from AgNPs was measured in cell culture medium by atomic absorption spectroscopy (AAS). The exposure of human osteoblast cells (hFOB 1.19) to AgNPs at concentration of 30 or 60 μg/mL for 24 or 48 hours, respectively resulted in cellular uptake of AgNPs and changes in cell ultrastructure. These changes were associated with apoptosis and necrosis as shown by flow cytometry and lactate dehydrogenase (LDH) assay as well as increased levels of pro-apoptotic Bax and decreased levels of anti-apoptotic Bcl-2 mRNA and protein. Importantly, we have found that AgNPs elevated the levels of nitric oxide (NO) with concomitant upregulation of inducible nitric oxide synthase (iNOS) mRNA and protein. A significant positive correlation was observed between the concentration of AgNPs and iNOS at protein and mRNA level (r = 0.837, r = 0.721, respectively; p<0.001). Finally, preincubation of osteoblast cells with N-iminoethyl-l-lysine (L-NIL), a selective iNOS inhibitor, as well as treating cells with iNOS small interfering RNAs (siRNA) significantly attenuated AgNPs-induced apoptosis and necrosis. Moreover, we have found that AgNPs-induced cells death is not related to Ag dissolution is cell culture medium.

CONCLUSION

These results unambiguously demonstrate that increased expression of iNOS and generation of NO as well as NO-derived reactive species is involved in AgNPs-induced osteoblast cell death. Our findings may help in development of new strategies to protect bone from AgNPs-induced cytotoxicity and increase the safety of orthopaedic tissue repair.

Biochemical and molecular evidences on the protection by magnesium oxide nanoparticles of chlorpyrifos-induced apoptosis in human lymphocytes

Background:

Chlorpyrifos (CP) is one of the most widely used organophosphate (OP) insecticides in agricultural and residential pest control with its attendant adverse health effect. In the present study, it is proposed to investigate the possible modulatory role of magnesium oxide nanoparticles (MgO NPs) against CP-induced toxicity in human lymphocytes and determine the mechanisms lying behind this protection by viability and biochemical assays.

Materials and Methods:

Isolated lymphocytes were exposed to 12 μg/mL CP either alone or in combination with different concentrations of MgO NPs (0.1 μg/mL, 1 μg/mL, 10 μg/mL, and 100 μg/mL). After a 3-day incubation, the viability and oxidative stress markers including cellular mitochondrial activity, caspase-3 and -9 activities, total antioxidant power, lipid peroxidation, and myeloperoxidase (MPO) activity were measured. Also, the levels of tumor necrosis factor-α (TNF-α) as inflammatory index, along with acetylcholinesterase (AChE) activity were measured. Statistical differences were determined using one-way analysis of variance (ANOVA) and Dunnett's multiple comparison tests.

Results:

It is indicated that CP-exposed lymphocytes treated with MgO NPs resulted in a substantial reduction in the pace of mortality as well as the stages of oxidative stress in a dose-dependent manner. Also, MgO NPs (100 μg/mL) meaningfully restored CP-induced increase of TNF-α (P < 0.001) and decrease of AChE activity (P < 0.001) and were capable of preventing CP-treated human lymphocytes from apoptosis (P < 0.001).

Conclusion:

Our results demonstrate that MgO NPs in approximate 100 nm diameter not only make cells resistant to the toxic properties of CP but also attenuate toxic effects of CP, which is demonstrating the potential of MgO NPs to be applied in future immune deficiency therapeutic strategies.

Unraveling the neurotoxicity of titanium dioxide nanoparticles: focusing on molecular mechanisms

Titanium dioxide nanoparticles (TiO2 NPs) possess unique characteristics and are widely used in many fields. Numerous in vivo studies, exposing experimental animals to these NPs through systematic administration, have suggested that TiO2 NPs can accumulate in the brain and induce brain dysfunction. Nevertheless, the exact mechanisms underlying the neurotoxicity of TiO2 NPs remain unclear. However, we have concluded from previous studies that these mechanisms mainly consist of oxidative stress (OS), apoptosis, inflammatory response, genotoxicity, and direct impairment of cell components. Meanwhile, other factors such as disturbed distributions of trace elements, disrupted signaling pathways, dysregulated neurotransmitters and synaptic plasticity have also been shown to contribute to neurotoxicity of TiO2 NPs. Recently, studies on autophagy and DNA methylation have shed some light on possible mechanisms of nanotoxicity. Therefore, we offer a new perspective that autophagy and DNA methylation could contribute to neurotoxicity of TiO2 NPs. Undoubtedly, more studies are needed to test this idea in the future. In short, to fully understand the health threats posed by TiO2 NPs and to improve the bio-safety of TiO2 NPs-based products, the neurotoxicity of TiO2 NPs must be investigated comprehensively through studying every possible molecular mechanism.

Preparation and evaluation of the cytotoxic nature of TiO2 nanoparticles by direct contact method

The purpose of this study is to prepare and evaluate the effect of synthesized titanium dioxide (TiO₂) nanoparticles for their biocompatibility on physiological body fluids and the effect of cell toxicity to produce osteointegration when used as implantable materials. For the past few decades, the number of researches done to understand the importance of the biocompatibility of bioceramics, metals, and polymers and their effect on clinical settings of biomedical devices has increased. Hence, the total concept of biocompatibility encourages researchers to actively engage in the investigation of the most compatible materials in living systems by analyzing them using suitable physical, chemical, and biological (bioassay) methods. The ceramic material nano TiO₂ was prepared by sol-gel method and analyzed for its functional group and phase formation by Fourier transform infrared spectroscopy and powder X-ray diffraction. Furthermore, the particle size, shape, surface topography, and morphological behavior were analyzed by dynamic light scattering, zeta potential, scanning electron microscopy–energy dispersive X-ray analysis, and transmission electron microscopy analysis. In addition to this, the cytotoxicity and cytocompatibility were determined on MG63 cell lines with varying doses of concentrations such as 1 µg/mL, 10 µg/mL, 25 µg/mL, 50 µg/mL, and 100 µg/mL with different time periods such as 24 hours and 48 hours. The results have not shown any toxicity, whereas, it improved the cell viability/proliferation at various concentrations. Hence, these findings indicate that the nano TiO₂ material acts as a good implantable material when used in the biomedical field as a prime surface-modifying agent.

High content analysis at single cell level identifies different cellular responses dependent on nanomaterial concentrations

A mechanistic understanding of nanomaterial (NM) interaction with biological environments is pivotal for the safe transition from basic science to applied nanomedicine. NM exposure results in varying levels of internalized NM in different neighboring cells, due to variances in cell size, cell cycle phase and NM agglomeration. Using high-content analysis, we investigated the cytotoxic effects of fluorescent quantum dots on cultured cells, where all effects were correlated with the concentration of NMs at the single cell level. Upon binning the single cell data into different categories related to NM concentration, this study demonstrates, for the first time, that quantum dots activate both cytoprotective and cytotoxic mechanisms, resulting in a zero net result on the overall cell population, yet with significant effects in cells with higher cellular NM levels. Our results suggest that future NM cytotoxicity studies should correlate NM toxicity with cellular NM numbers on the single cell level, as conflicting mechanisms in particular cell subpopulations are commonly overlooked using classical toxicological methods.

Central nervous system toxicity of metallic nanoparticles

Nanomaterials (NMs) are increasingly used for the therapy, diagnosis, and monitoring of disease- or drug-induced mechanisms in the human biological system. In view of their small size, after certain modifications, NMs have the capacity to bypass or cross the blood–brain barrier. Nanotechnology is particularly advantageous in the field of neurology. Examples may include the utilization of nanoparticle (NP)-based drug carriers to readily cross the blood–brain barrier to treat central nervous system (CNS) diseases, nanoscaffolds for axonal regeneration, nanoelectromechanical systems in neurological operations, and NPs in molecular imaging and CNS imaging. However, NPs can also be potentially hazardous to the CNS in terms of nano-neurotoxicity via several possible mechanisms, such as oxidative stress, autophagy, and lysosome dysfunction, and the activation of certain signaling pathways. In this review, we discuss the dual effect of NMs on the CNS and the mechanisms involved. The limitations of the current research are also discussed.

Application of dental nanomaterials: potential toxicity to the central nervous system

Nanomaterials are defined as materials with one or more external dimensions with a size of 1-100 nm. Such materials possess typical nanostructure-dependent properties (eg, chemical, biological, optical, mechanical, and magnetic), which may differ greatly from the properties of their bulk counterparts. In recent years, nanomaterials have been widely used in the production of dental materials, particularly in light polymerization composite resins and bonding systems, coating materials for dental implants, bioceramics, endodontic sealers, and mouthwashes. However, the dental applications of nanomaterials yield not only a significant improvement in clinical treatments but also growing concerns regarding their biosecurity. The brain is well protected by the blood-brain barrier (BBB), which separates the blood from the cerebral parenchyma. However, in recent years, many studies have found that nanoparticles (NPs), including nanocarriers, can transport through the BBB and locate in the central nervous system (CNS). Because the CNS may be a potential target organ of the nanomaterials, it is essential to determine the neurotoxic effects of NPs. In this review, possible dental nanomaterials and their pathways into the CNS are discussed, as well as related neurotoxicity effects underlying the in vitro and in vivo studies. Finally, we analyze the limitations of the current testing methods on the toxicological effects of nanomaterials. This review contributes to a better understanding of the nano-related risks to the CNS as well as the further development of safety assessment systems.

In vitro cytotoxic evaluation of MgO nanoparticles and their effect on the expression of ROS genes

Water-dispersible MgO nanoparticles were tested to investigate their cytotoxic effects on oxidative stress gene expression. In this in vitro study, genes related to reactive oxygen species (ROS), glutathione S-transferase (GST) and catalase, were quantified using real-time polymerase chain reactions (molecular level) and molecular beacon technologies (cellular level). The monodispersed MgO nanoparticles, 20 nm in size, were used to treat human cancer cell lines (liver cancer epithelial cells) at different concentrations (25, 75 and 150 µg/mL) and incubation times (24, 48 and 72 h). Both the genetic and cellular cytotoxic screening methods produced consistent results, showing that GST and catalase ROS gene expression was maximized at 150 µg/mL nanoparticle treatment with 48 h incubation. However, the genotoxic effect of MgO nanoparticles was not significant compared with control experiments, which indicates its significant potential applications in nanomedicine as a diagnostic and therapeutic tool.

Comparative study of the cytotoxic and genotoxic potentials of zinc oxide and titanium dioxide nanoparticles

Nanoparticles (NPs) of zinc oxide (ZnO) and titanium dioxide (TiO₂) are receiving increasing attention due to their widespread applications. The aim of this study was to evaluate the toxic effect of ZnO and TiO₂ NPs at different concentrations (50, 100, 250 and 500 ppm) and compare them with their respective salts using a battery of cytotoxicity, and genotoxicity parameters. To evaluate cytotoxicity, we have used human erythrocytes and for genotoxic studies human lymphocytes have been used as in vitro model species. Concentration dependent hemolytic activity to RBC's was obtained for both NPs. ZnO and TiO₂ NPs resulted in 65.2% and 52.5% hemolysis at 250 ppm respectively indicating that both are cytotoxic to human RBCs. Antioxidant enzymes assays were also carried out in their respective hemolysates. Both nanoparticles were found to generate reactive oxygen species (ROS) concomitant with depletion of glutathione and GST levels and increased SOD, CAT and lipid peroxidation in dose dependent manner. ZnO and TiO₂ NPs exerted roughly equal oxidative stress in terms of aforementioned stress markers. Genotoxic potential of both the NPs was investigated by in vitro alkaline comet assay. DNA damage induced by the NPs was concentration dependent and was significantly greater than their ionic forms at 250 and 500 ppm concentrations. Moreover, the nanoparticles of ZnO were significantly more genotoxic than those of TiO₂ at higher concentrations. The toxicity of these NPs is due to the generation of ROS thereby causing oxidative stress.

Titanium dioxide nanoparticles enhance production of superoxide anion and alter the antioxidant system in human osteoblast cells

Titanium dioxide (TiO₂) nanoparticles (NPs) are manufactured worldwide for a variety of engineering and bioengineering applications. TiO₂NPs are frequently used as a material for orthopedic implants. However, to the best of our knowledge, the biocompatibility of TiO₂NPs and their effects on osteoblast cells, which are responsible for the growth and remodeling of the human skeleton, have not been thoroughly investigated. In the research reported here, we studied the effects of exposing hFOB 1.19 human osteoblast cells to TiO₂NPs (5–15 nm) for 24 and 48 hours. Cell viability, alkaline phosphatase (ALP) activity, cellular uptake of NPs, cell morphology, superoxide anion (O₂^•−2) generation, superoxide dismutase (SOD) activity and protein level, sirtuin 3 (SIR3) protein level, correlation between manganese (Mn) SOD and SIR, total antioxidant capacity, and malondialdehyde were measured following exposure of hFOB 1.19 cells to TiO₂NPs. Exposure of hFOB 1.19 cells to TiO₂NPs resulted in: (1) cellular uptake of NPs; (2) increased cytotoxicity and cell death in a time- and concentration-dependent manner; (3) ultrastructure changes; (4) decreased SOD and ALP activity; (5) decreased protein levels of SOD1, SOD2, and SIR3; (6) decreased total antioxidant capacity; (7) increased O₂^•− generation; and (8) enhanced lipid peroxidation (malondialdehyde level). The linear relationship between the protein level of MnSOD and SIR3 and between O₂^•− content and SIR3 protein level was observed. Importantly, the cytotoxic effects of TiO₂NPs were attenuated by the pretreatment of hFOB 1.19 cells with SOD, indicating the significant role of O₂^•− in the cell damage and death observed. Thus, decreased expression of SOD leading to increased oxidizing stress may underlie the nanotoxic effects of TiO₂NPs on human osteoblasts.

Cell type-dependent changes in CdSe/ZnS quantum dot uptake and toxic endpoints

Toxicity of nanoparticles (NPs) is often correlated with the physicochemical characteristics of the materials. However, some discrepancies are noted in in-vitro studies on quantum dots (QDs) with similar physicochemical properties. This is partly related to variations in cell type. In this study, we show that epithelial (BEAS-2B), fibroblast (HFF-1), and lymphoblastoid (TK6) cells show different biological responses following exposure to QDs. These cells represented the 3 main portals of NP exposure: bronchial, skin, and circulatory. The uptake and toxicity of negatively and positively charged CdSe:ZnS QDs of the same core size but with different surface chemistries (carboxyl or amine polymer coatings) were investigated in full and reduced serum containing media following 1 and 3 cell cycles. Following thorough physicochemical characterization, cellular uptake, cytotoxicity, and gross chromosomal damage were measured. Cellular damage mechanisms in the form of reactive oxygen species and the expression of inflammatory cytokines IL-8 and TNF-α were assessed. QDs uptake and toxicity significantly varied in the different cell lines. BEAS-2B cells demonstrated the highest level of QDs uptake yet displayed a strong resilience with minimal genotoxicity following exposure to these NPs. In contrast, HFF-1 and TK6 cells were more susceptible to toxicity and genotoxicity, respectively, as a result of exposure to QDs. Thus, this study demonstrates that in addition to nanomaterial physicochemical characterization, a clear understanding of cell type-dependent variation in uptake coupled to the inherently different capacities of the cell types to cope with exposure to these exogenous materials are all required to predict genotoxicity.

Analysis of zinc oxide nanoparticles binding proteins in rat blood and brain homogenate

Nanoparticles (NPs) are currently used in chemical, cosmetic, pharmaceutical, and electronic products. Nevertheless, limited safety information is available for many NPs, especially in terms of their interactions with various binding proteins, leading to potential toxic effects. Zinc oxide (ZnO) NPs are included in the formulation of new products, such as adhesives, batteries, ceramics, cosmetics, cement, glass, ointments, paints, pigments, and supplementary foods, resulting in increased human exposures to ZnO. Hence, we investigated the potential ZnO nanotoxic pathways by analyzing the adsorbed proteins, called protein corona, from blood and brain from four ZnO NPs, ZnO(SM20(-)), ZnO(SM20(+)), ZnO(AE100(-)), and ZnO(AE100(+)), in order to understand their potential mechanisms in vivo. Through this study, liquid chromatography-mass spectroscopy/mass spectroscopy technology was employed to identify all bound proteins. Totals of 52 and 58 plasma proteins were identified as being bound to ZnO(SM20(-)) and ZnO(SM20(+)), respectively. For ZnO(AE100(-)) and ZnO(AE100(+)), 58 and 44 proteins were bound, respectively. Similar numbers of proteins were adsorbed onto ZnO irrespective of size or surface charge of the nanoparticle. These proteins were further analyzed with ClueGO, a Cytoscape plugin, which provided gene ontology and the biological interaction processes of identified proteins. Interactions between diverse proteins and ZnO nanoparticles could result in an alteration of their functions, conformation, and clearance, eventually affecting many biological processes.

A proteomic view to characterize the effect of chitosan nanoparticle to hepatic cells: is chitosan nanoparticle an enhancer of PI3K/AKT1/mTOR pathway?

Chitosan nanoparticle, a biocompatible material, was used as a potential drug delivery system widely. Our current investigation studies were the bioeffects of the chitosan nanoparticle uptake by liver cells. In this experiment, the characterizations of chitosan nanoparticles were measured by transmission electron microscopy and particle size analyzer. The average size of the chitosan nanoparticle was 224.6 ± 11.2 nm, and the average zeta potential was +14.08 ± 0.7 mV. Moreover, using proteomic approaches to analyze the differential protein expression patterns resulted from the chitosan nanoparticle uptaken by HepG2 and CCL-13 cells identified several proteins involved in the PI3K/AKT1/mTOR pathway. Our experimental results have demonstrated that the chitosan nanoparticle may involve in the liver cancer cell metastasis and proliferation.

ZnO nanoparticle-induced oxidative stress triggers apoptosis by activating JNK signaling pathway in cultured primary astrocytes

It has been documented in in vitro studies that zinc oxide nanoparticles (ZnO NPs) are capable of inducing oxidative stress, which plays a crucial role in ZnO NP-mediated apoptosis. However, the underlying molecular mechanism of apoptosis in neurocytes induced by ZnO NP exposure was not fully elucidated. In this study, we investigated the potential mechanisms of apoptosis provoked by ZnO NPs in cultured primary astrocytes by exploring the molecular signaling pathways triggered after ZnO NP exposure. ZnO NP exposure was found to reduce cell viability in MTT assays, increase lactate dehydrogenase (LDH) release, stimulate intracellular reactive oxygen species (ROS) generation, and elicit caspase-3 activation in a dose- and time-dependent manner. Apoptosis occurred after ZnO NP exposure as evidenced by nuclear condensation and poly(ADP-ribose) polymerase-1 (PARP) cleavage. A decrease in mitochondrial membrane potential (MMP) with a concomitant increase in the expression of Bax/Bcl-2 ratio suggested that the mitochondria also mediated the pathway involved in ZnO NP-induced apoptosis. In addition, exposure of the cultured cells to ZnO NPs led to phosphorylation of c-Jun N-terminal kinase (JNK), extracellular signal-related kinase (ERK), and p38 mitogen-activated protein kinase (p38 MAPK). Moreover, JNK inhibitor (SP600125) significantly reduced ZnO NP-induced cleaved PARP and cleaved caspase-3 expression, but not ERK inhibitor (U0126) or p38 MAPK inhibitor (SB203580), indicating that JNK signaling pathway is involved in ZnO NP-induced apoptosis in primary astrocytes.

Greater fibroblast proliferation on an ultrasonicated ZnO/PVC nanocomposite material

There has been a significant and growing concern over nosocomial medical device infections. Previous studies have demonstrated that embedding nanoparticles alone (specifically, zinc oxide [ZnO]) in conventional polymers (eg, polyvinyl chloride [PVC]) can decrease bacteria growth and may have the potential to prevent or disrupt bacterial processes that lead to infection. However, little to no studies have been conducted to determine mammalian cell functions on such a nanocomposite material. Clearly, for certain medical device applications, maintaining healthy mammalian cell functions while decreasing bacteria growth is imperative (yet uncommon). For this reason, in the presented study, ZnO nanoparticles of varying sizes (from 10 nm to >200 nm in diameter) and functionalization (including no functionalization to doping with aluminum oxide and functionalizing with a silane coupling agent KH550) were incorporated into PVC either with or without ultrasonication. Results of this study provided the first evidence of greater fibroblast density after 18 hours of culture on the smallest ZnO nanoparticle incorporated PVC samples with dispersion aided by ultrasonication. Specifically, the greatest amount of fibroblast proliferation was measured on ZnO nanoparticles functionalized with a silane coupling agent KH550; this sample exhibited the greatest dispersion of ZnO nanoparticles. Water droplet tests showed a general trend of decreased hydrophilicity when adding any of the ZnO nanoparticles to PVC, but an increase in hydrophilicity (albeit still below controls or pure PVC) when using ultrasonication to increase ZnO nanoparticle dispersion. Future studies will have to correlate this change in wettability to initial protein adsorption events that may explain fibroblast behavior. Mechanical tests also provided evidence of the ability to tailor mechanical properties of the ZnO/PVC nanocomposites through the use of the different ZnO nanoparticles. Coupled with previous antibacterial studies, the present study demonstrated that highly dispersed ZnO/PVC nanocomposite materials should be further studied for numerous medical device applications.

Surface coatings of ZnO nanoparticles mitigate differentially a host of transcriptional, protein and signalling responses in primary human olfactory cells

BACKGROUND

Inhaled nanoparticles have been reported in some instances to translocate from the nostril to the olfactory bulb in exposed rats. In close proximity to the olfactory bulb is the olfactory mucosa, within which resides a niche of multipotent cells. Cells isolated from this area may provide a relevant in vitro system to investigate potential effects of workplace exposure to inhaled zinc oxide nanoparticles.

METHODS

Four types of commercially-available zinc oxide (ZnO) nanoparticles, two coated and two uncoated, were examined for their effects on primary human cells cultured from the olfactory mucosa. Human olfactory neurosphere-derived (hONS) cells from healthy adult donors were analyzed for modulation of cytokine levels, activation of intracellular signalling pathways, changes in gene-expression patterns across the whole genome, and compromised cellular function over a 24 h period following exposure to the nanoparticles suspended in cell culture medium.

RESULTS

ZnO nanoparticle toxicity in hONS cells was mediated through a battery of mechanisms largely related to cell stress, inflammatory response and apoptosis, but not activation of mechanisms that repair damaged DNA. Surface coatings on the ZnO nanoparticles mitigated these cellular responses to varying degrees.

CONCLUSIONS

The results indicate that care should be taken in the workplace to minimize generation of, and exposure to, aerosols of uncoated ZnO nanoparticles, given the adverse responses reported here using multipotent cells derived from the olfactory mucosa.

Nanosized zinc oxide induces toxicity in human lung cells

Zinc oxide nanoparticles (ZnO-NPs) are increasingly used in sunscreens, biosensors, food additives, pigments, rubber manufacture, and electronic materials. With the wide application of ZnO-NPs, concern has been raised about its unintentional health and environmental impacts. This study investigates the toxic effects of ZnO-NPs in human lung cells. In order to assess toxicity, human lung epithelial cells (L-132) were exposed to dispersion of 50 nm ZnO-NPs at concentrations of 5, 25, 50, and 100  μ g/mL for 24 h. The toxicity was evaluated by observing changes in cell morphology, cell viability, oxidative stress parameters, DNA damage analysis, and gene expression. Exposure to 50 nm ZnO-NPs at concentrations between 5 and 100  μ g/mL decreased cell viability in a concentration-dependent manner. Morphological examination revealed cell shrinkage, nuclear condensation, and formation of apoptotic bodies. The oxidative stress parameters revealed significant depletion of GSH level and increase in ROS levels suggesting generation of oxidative stress. ZnO-NPs exposure caused DNA fragmentation demonstrating apoptotic type of cell death. ZnO-NPs increased the expression of metallothionein gene, which is considered as a biomarker in metal-induced toxicity. To summarize, ZnO-NPs cause toxicity in human lung cells possibly through oxidative stress-induced apoptosis.

Selective antibacterial effects of mixed ZnMgO nanoparticles

Antibiotic resistance has impelled the research for new agents that can inhibit bacterial growth without showing cytotoxic effects on humans and other species. We describe the synthesis and physicochemical characterization of nanostructured ZnMgO whose antibacterial activity was compared to its pure nano-ZnO and nano-MgO counterparts. Among the three oxides, ZnO nanocrystals-with the length of tetrapod legs about 100 nm and the diameter about 10 nm-were found to be the most effective antibacterial agents since both Gram-positive (B. subtilis) and Gram-negative (E. coli) bacteria were completely eradicated at concentration of 1 mg/mL. MgO nanocubes (the mean cube size ~50 nm) only partially inhibited bacterial growth, whereas ZnMgO nanoparticles (sizes corresponding to pure particles) revealed high specific antibacterial activity to Gram-positive bacteria at this concentration. Transmission electron microscopy analysis showed that B. subtilis cells were damaged after contact with nano-ZnMgO, causing cell contents to leak out. Our preliminary toxicological study pointed out that nano-ZnO is toxic when applied to human HeLa cells, while nano-MgO and the mixed oxide did not induce any cell damage. Overall, our results suggested that nanostructured ZnMgO, may reconcile efficient antibacterial efficiency while being a safe new therapeutic for bacterial infections.