Comparative study of ZnO and TiO2nanoparticles: physicochemical characterisation and toxicological effects on human colon carcinoma cells

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

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

Investigating the in vitro antibacterial, antibiofilm, antioxidant, anticancer and antiviral activities of zinc oxide nanoparticles biofabricated from Cassia javanica

It is thought to be risk-free, environmentally benign, and safe for biological processes to produce zinc oxide nanoparticles from renewable resources. This study examined Cassia javanica's ability to create ZnONPs. The generated ZnONPs were analyzed using a variety of techniques, such as TEM, FTIR spectroscopy, UV-Vis spectroscopy, and XRD analysis. The antibacterial potential of ZnONPs has been investigated using both Agar well diffusion and microtitreplate (MTP) methods. One method used to evaluate ZnONPs' capacity to scavenge free radicals at different concentrations was the DPPH method. The permanent zinc oxide (ZnO) shape and the naturally occurring crystal structure of ZnONPs were validated by the XRD data. ZnONPs showed antibacterial activity with MICs of 31.7 μg/mL toward Bacillus subtilis, 62.5 μg/mL for Salmonella typhimurium, Escherichia coli while Clostridium sporogenes and Bacillus pumilus was 125μg/mL. Furthermore, ZnONPs demonstrated a range of antibiofilm activities toward Staphylococcus aureus (MRSA). ZnONPs showed an intriguing antioxidant capacity, achieving IC50 of 109.3 μg/ml μg/mL. Additionally, ZnONPs demonstrated low toxic effect on Vero cell with IC50 154.01 μg/mL as well as possible anticancer action when applied to the carcinoma cell lines HepG2 with IC50 of 47.48 μg/mL. Furthermore, ZnONPs at 62.5 μg/mL had a promising antiviral impact against HSV1 and COX B4, with antiviral activities of 75.4% and 65.8%, respectively.

Mechanism of Action and Efficiency of Ag3PO4-Based Photocatalysts for the Control of Hazardous Gram-Positive Pathogens

Silver phosphate and its composites have been attracting extensive interest as photocatalysts potentially effective against pathogenic microorganisms. The purpose of the present study was to investigate the mechanism of bactericidal action on cells of opportunistic pathogens. The Ag3PO4/P25 (AGP/P25) and Ag3PO4/HA (HA/AGP) powders were prepared via a co-precipitation method. Thereafter, their antimicrobial properties against Enterococcus faecalis, Staphylococcus epidermidis, and Staphylococcus aureus (clinical and reference strains) were analyzed in the dark and after exposure to visible light (VIS). The mechanism leading to cell death was investigated by the leakage of metabolites and potassium ions, oxidative stress, and ROS production. Morphological changes of the bacterial cells were visualized by transmission electron microscopy (TEM) and scanning transmission electron microscopy with energy-dispersive X-ray spectroscopy (SEM EDS) analysis. It has been shown that Ag3PO4-based composites are highly effective agents that can eradicate 100% of bacterial populations during the 60 min photocatalytic inactivation. Their action is mainly due to the production of hydroxyl radicals and photogenerated holes which lead to oxidative stress in cells. The strong affinity to the bacterial cell wall, as well as the well-known biocidal properties of silver itself, increase undoubtedly the antimicrobial potential of the Ag3PO4-based composites.

In Vitro Antiviral and Anti-Inflammatory Activities of N-Acetylglucosamine: Development of an Alternative and Safe Approach to Fight Viral Respiratory Infections

Viral respiratory tract infections (RTIs) are responsible for significant morbidity and mortality worldwide. A prominent feature of severe respiratory infections, such as severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infection, is the cytokine release syndrome. Therefore, there is an urgent need to develop different approaches both against viral replication and against the consequent inflammation. N-acetylglucosamine (GlcNAc), a glucosamine (GlcN) derivative, has been developed as an immunomodulatory and anti-inflammatory inexpensive and non-toxic drug for non-communicable disease treatment and/or prevention. Recent studies have suggested that GlcN, due to its anti-inflammatory activity, could be potentially useful for the control of respiratory virus infections. Our present study aimed to evaluate in two different immortalized cell lines whether GlcNAc could inhibit or reduce both viral infectivity and the inflammatory response to viral infection. Two different viruses, frequent cause of upper and lower respiratory tract infections, were used: the H1N1 Influenza A virus (IAV) (as model of enveloped RNA virus) and the Human adenovirus type 2 (Adv) (as model of naked DNA virus). Two forms of GlcNAc have been considered, bulk GlcNAc and GlcNAc in nanoform to overcome the possible pharmacokinetic limitations of GlcNAc. Our study suggests that GlcNAc restricts IAV replication but not Adv infection, whereas nano-GlcNAc inhibits both viruses. Moreover, GlcNAc and mainly its nanoformulation were able to reduce the pro-inflammatory cytokine secretion stimulated by viral infection. The correlation between inflammatory and infection inhibition is discussed.

Toxicity of transition metal nanoparticles: A review of different experimental models in the gastrointestinal tract

The development of nanotechnology is becoming a major trend nowadays. Nanoparticles (NPs) have been widely used in fields including food, biomedicine, and cosmetics, endowing NPs more opportunities to enter the human body. It is well-known that the gut microbiome plays a key role in human health, and the exposure of intestines to NPs is unavoidable. Accordingly, the toxicity of NPs has attracted more attention than before. This review mainly highlights recent advances in the evaluation of NPs' toxicity in the gastrointestinal system from the existing cell-based experimental models, such as the original mono-culture models, co-culture models, three-dimensional (3D) culture models, and the models established on microfluidic chips, to those in vivo experiments, such as mice models, Caenorhabditis elegans models, zebrafish models, human volunteers, as well as computer-simulated toxicity models. Owing to these models, especially those more biomimetic models, the outcome of the toxicity of NPs acting in the gastrointestinal tract can get results closer to what happened inside the real human microenvironment.

Adverse Outcome Pathways Associated with the Ingestion of Titanium Dioxide Nanoparticles-A Systematic Review

Titanium dioxide nanoparticles (TiO₂-NPs) are widely used, and humans are exposed through food (E171), cosmetics (e.g., toothpaste), and pharmaceuticals. The oral and gastrointestinal (GIT) tract are the first contact sites, but it may be systemically distributed. However, a robust adverse outcome pathway (AOP) has not been developed upon GIT exposure to TiO₂-NPs. The aim of this review was to provide an integrative analysis of the published data on cellular and molecular mechanisms triggered after the ingestion of TiO₂-NPs, proposing plausible AOPs that may drive policy decisions. A systematic review according to Prisma Methodology was performed in three databases of peer-reviewed literature: Pubmed, Scopus, and Web of Science. A total of 787 records were identified, screened in title/abstract, being 185 used for data extraction. The main endpoints identified were oxidative stress, cytotoxicity/apoptosis/cell death, inflammation, cellular and systemic uptake, genotoxicity, and carcinogenicity. From the results, AOPs were proposed where colorectal cancer, liver injury, reproductive toxicity, cardiac and kidney damage, as well as hematological effects stand out as possible adverse outcomes. The recent transgenerational studies also point to concerns with regard to population effects. Overall, the findings further support a limitation of the use of TiO₂-NPs in food, announced by the European Food Safety Authority (EFSA).

The Stability and Anti-Angiogenic Properties of Titanium Dioxide Nanoparticles (TiO2NPs) Using Caco-2 Cells

Titanium dioxide nanoparticles (TiO₂NPs) are found in a wide range of products such as sunscreen, paints, toothpaste and cosmetics due to their white pigment and high refractive index. These wide-ranging applications could result in direct or indirect exposure of these NPs to humans and the environment. Accordingly, conflicting levels of toxicity has been associated with these NPs. Therefore, the risk associated with these reports and for TiO₂NPs produced using varying methodologies should be measured. This study aimed to investigate the effects of various media on TiO₂NP properties (hydrodynamic size and zeta potential) and the effects of TiO₂NP exposure on human colorectal adenocarcinoma (Caco-2) epithelial cell viability, inflammatory and cell stress biomarkers and angiogenesis proteome profiles. The NPs increased in size over time in the various media, while zeta potentials were stable. TiO₂NPs also induced cell stress biomarkers, which could be attributed to the NPs not being cytotoxic. Consequently, TiO₂NP exposure had no effects on the level of inflammatory biomarkers produced by Caco-2. TiO₂NPs expressed some anti-angiogenic properties when exposed to the no-observed-adverse-effect level and requires further in-depth investigation.

The colony forming efficiency assay for toxicity testing of nanomaterials—Modifications for higher-throughput

To cope with the high number of nanomaterials manufactured, it is essential to develop high-throughput methods for in vitro toxicity screening. At the same time, the issue with interference of the nanomaterial (NM) with the read-out or the reagent of the assay needs to be addressed to avoid biased results. Thus, validated label-free methods are urgently needed for hazard identification of NMs to avoid unintended adverse effects on human health. The colony forming efficiency (CFE) assay is a label- and interference-free method for quantification of cytotoxicity by cell survival and colony forming efficiency by CFE formation. The CFE has shown to be compatible with toxicity testing of NMs. Here we present an optimized protocol for a higher-throughput set up.

Microbial Mediated Synthesis of Zinc Oxide Nanoparticles, Characterization and Multifaceted Applications

Nanoparticles have gained considerable importance compared to bulk counterparts due to their unique properties. Due to their high surface to volume ratio and high reactivity, metallic and metal-oxide nanostructures have shown great potential applications. Among them, zinc oxide nanoparticles (ZnONPs) have gained tremendous attention attributed to their unique properties such as low toxicity, biocompatibility, simplicity, easy fabrication, and environmental friendly. Remarkably, ZnONPs exhibit optical, physical, antimicrobial, anticancer, anti-inflammatory and wound healing properties. These nanoparticles have been applied in various fields such as in biomedicine, biosensors, electronics, food, cosmetic industries, textile, agriculture and environment. The synthesis of ZnONPs can be performed by chemical, physical and biological methods. Although the chemical and physical methods suffer from some disadvantages such as the involvement of high temperature and pressure conditions, high cost and not environmentally friendly, the green synthesis of ZnONPs offers a promising substitute to these conventional methods. On that account, the microbial mediated synthesis of ZnONPs is clean, eco-friendly, nontoxic and biocompatible method. This paper reviews the microbial synthesis of ZnONPs, parameters used for the optimization process and their physicochemical properties. The potential applications of ZnONPs in biomedical, agricultural and environmental fields as well as their toxic aspects on human beings and animals have been reviewed.

Meta-analysis of in-vitro cytotoxicity evaluation studies of zinc oxide nanoparticles: Paving way for safer innovations

Nano-based products have shown their daunting presence in several sectors. Among them, Zinc Oxide (ZnO) nanoparticles wangled the reputation of providing "next-generation solutions" and are being utilized in plethora of products. Their widespread application has led to increased exposure of these particles, raising concerns regarding toxicological repercussions to the human health and environment. The diversity, complexity, and heterogeneity in the available literature, along with correlation of befitting attributes, makes it challenging to develop one systematic framework to predict this toxicity. The present study aims at developing predictive modelling framework to tap the prospective features responsible for causing cytotoxicity in-vitro on exposure to ZnO nanoparticles. Rigorous approach was used to mine the information from complete body of evidence published to date. The attributes, features and experimental conditions were systematically extracted to unmask the effect of varied features. 1240 data points from 76 publications were obtained, containing 14 qualitative and quantitative attributes, including physiochemical properties of nanoparticles, cell culture and experimental parameters to perform meta-analysis. For the first time, the efforts were made to investigate the degree of significance of attributes accountable for causing cytotoxicity on exposure to ZnO nanoparticles. We show that in-vitro cytotoxicity is closely related with dose concentration of nanoparticles, followed by exposure time, disease state of the cell line and size of these nanoparticles among other attributes.

Investigation of the genotoxicity of digested titanium dioxide nanomaterials in human intestinal cells

The widespread use of titanium dioxide nanomaterials (TiO₂ NMs) in food and consumer products such as toothpaste or food contact materials, suggests the relevance of human oral exposure to these nanomaterials (NMs) and raises the possibility of adverse effects in the gastrointestinal tract (GIT). We previously showed that the in vitro digestion of TiO₂ NMs may increase their toxicity in intestinal cells. In this work, we analyzed the genotoxicity and the intracellular reactive oxygen species induction by physiologically relevant concentrations of three different TiO₂ NMs (NM-102, NM-103 and NM-105) in Caco-2 and HT29-MTX-E12 intestinal cells, while considering the potential influence of the digestion process in the NMs' physiochemical characteristics. The results evidenced a DNA-damaging effect dependent on the NM, more relevant for the rutile/anatase NM-105, possibly due to its lower hydrodynamic size in the cells medium. In addition, the results of the micronucleus assay suggest effects on chromosomal integrity, an indicator of cancer risk, in the HT29-MTX-E12 cells, for all the tested TiO₂ NMs, especially after the in vitro digestion. This work supports the evidence for concerns on the use of TiO₂ NMs as a food additive, recently reported by EFSA, and for their use in applications in consumer products that may drive human exposure through ingestion.

Cellular and Molecular Mechanisms of Toxicity of Ingested Titanium Dioxide Nanomaterials

An exponential increase in products containing titanium dioxide nanomaterials (TiO2), in agriculture, food and feed industry, lead to increased oral exposure to these nanomaterials (NMs). Thus, the gastrointestinal tract (GIT) emerges as a possible route of exposure that may drive systemic exposure, if the intestinal barrier is surpassed. NMs have been suggested to produce adverse outcomes, such as genotoxic effects, that are associated with increased risk of cancer, leading to a concern for public health. However, to date, the differences in the physicochemical characteristics of the NMs studied and other variables in the test systems have generated contradictory results in the literature. Processes like human digestion may change the NMs characteristics, inducing unexpected toxic effects in the intestine. Using TiO2 as case-study, this chapter provides a review of the works addressing the interactions of NMs with biological systems in the context of intestinal tract and digestion processes, at cellular and molecular level. The knowledge gaps identified suggest that the incorporation of a simulated digestion process for in vitro studies has the potential to improve the model for elucidating key events elicited by these NMs, advancing the nanosafety studies towards the development of an adverse outcome pathway for intestinal effects.

The impact of TiO2 nanoparticle exposure on transmembrane cholesterol transport and enhanced bacterial infectivity in HeLa cells

We have previously shown that exposure to TiO₂ nanoparticles (NPs) reduces the resistance of HeLa cells to bacterial infection. Here we demonstrate that the increased infectivity is associated with enhanced asymmetry in the cholesterol distribution. We applied a live cell imaging method which uses tunable orthogonal cholesterol sensors to visualize and quantify in-situ cholesterol distribution between the two leaflets of the plasma membrane (PM). In the control culture, we found marked transbilayer asymmetry of cholesterol, with the concentration in the outer plasma membrane (OPM) being 13 ± 2-fold higher than that in the inner plasma membrane (IPM). Exposure of the culture to 0.1 mg/mL of rutile TiO₂ NPs increased the asymmetry such that the concentration in the OPM was 51 ± 10 times higher, while the total cholesterol content increased only 21 ± 2%. This change in cholesterol gradient may explain the increase in bacterial infectivity in HeLa cells exposed to TiO₂ NPs since many pathogens, including Staphylococcus aureus used in the present study, require cholesterol for proper membrane attachment and virulence. RT-PCR indicated that exposure to TiO₂ was responsible for upregulation of the ABCA1 and ABCG1 mRNAs, which are responsible for the production of the cholesterol transporter proteins that facilitate cholesterol transport across cellular membranes. This was confirmed by the observation of an overall decrease in bacterial infection in ABCA1 knockout or methyl-β-cyclodextrin-treated HeLa cells, as regardless of TiO₂ NP exposure. Hence rather than preventing bacterial infection, TiO₂ nanoparticles upregulate genes associated with membrane cholesterol production and distribution, hence increasing infectivity. STATEMENT OF SIGNIFICANCE: A great deal of work has been done regarding the toxicology of the particles, especially focusing on detrimental outcomes associated with reactive oxygen species (ROS) production. In this paper we show unambiguously a very surprising result, namely the ability of these particles to enhance bacterial infection even at very small exposure levels, where none of the deleterious effects of ROS products can yet be detected. Using a new imaging technique, we are able to demonstrate, in operando, the effect of the particles on cholesterol generation and distribution in live HeLa cells. This paper also represents the first in a series where we explore other consequences of increased membrane cholesterol, due to particle exposure, which are known to have multiple other consequences on human tissue function and development.

Zinc oxide nanoparticles promote the aging process in a size-dependent manner

Zinc oxide (ZnO) nanoparticles (NPs) are generally utilized in cosmetic goods, sheds, biosensors, and delivery of drug. As in vitro ideal systems, mesenchymal stem cells (MSCs) are used to test acute toxicity. In the present study, size-dependent cytotoxicity effects of ZnO NPs on MSCs were assessed. Bone marrow and adipose MSCs were treated with ZnO NPs with average sizes of 10-30 and 35-45 nm. The 5 and 10 µg/ml concentrations of ZnO NP were found to be the safe concentrations for the NP sizes of 10-30 and 35-45 nm, respectively. Cell-cycle analysis indicated that the small size of ZnO NPs has more negative effects on the process of cell entry to DNA synthesis when compared to the larger size. The results of the β-galactosidase test showed the promotion of the aging process in the cells treated with the smaller size of ZnO NPs. Both sizes of the NP were found to upregulate the aging-related genes NF-kB and p53 and downregulate the anti-aging gene Nanog. To sum up, the smaller size of ZnO NPs can enhance the aging process in the cells.

Influence of Titanium Dioxide Nanoparticles on Human Health and the Environment

Nanotechnology has enabled tremendous breakthroughs in the development of materials and, nowadays, is well established in various economic fields. Among the various nanomaterials, TiO₂ nanoparticles (NPs) occupy a special position, as they are distinguished by their high availability, high photocatalytic activity, and favorable price, which make them useful in the production of paints, plastics, paper, cosmetics, food, furniture, etc. In textiles, TiO₂ NPs are widely used in chemical finishing processes to impart various protective functional properties to the fibers for the production of high-tech textile products with high added value. Such applications contribute to the overall consumption of TiO₂ NPs, which gives rise to reasonable considerations about the impact of TiO₂ NPs on human health and the environment, and debates regarding whether the extent of the benefits gained from the use of TiO₂ NPs justifies the potential risks. In this study, different TiO₂ NPs exposure modes are discussed, and their toxicity mechanisms—evaluated in various in vitro and in vivo studies—are briefly described, considering the molecular interactions with human health and the environment. In addition, in the conclusion of this study, the toxicity and biocompatibility of TiO₂ NPs are discussed, along with relevant risk management strategies.

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.

A harmonized and standardized in vitro approach produces reliable results on silver nanoparticles toxicity in different cell lines

Despite the widespread use of silver nanoparticles (AgNPs) in different fields and the amount of investigations available, to date, there are many contradictory results on their potential toxicity. In the present study, extensively characterized 20-nm AgNPs were investigated using optimized protocols and standardized methods to test several toxicological endpoints in different cell lines. The agglomeration/aggregation state of AgNPs in culture media was measured by dynamic light scattering (DLS). DNA and chromosomal damage on BEAS-2B and RAW 264.7 cells were evaluated by comet and micronucleus assays, while oxidative DNA damage by modified comet assay and 8-oxodG/8-oxodA detection. We also investigated immunotoxicity and immunomodulation by cytokine release and NO production in RAW 264.7 and MH-S cells, with or without lipopolysaccharide (LPS) stimulus. Transmission electron microscope (TEM) analysis was used to analyze cellular uptake of AgNPs. Our results indicate different values of AgNPs hydrodynamic diameter depending on the medium, some genotoxic effect just on BEAS-2B and no or slight effects on function of RAW 264.7 and MH-S in absence or presence of LPS stimulus. This study highlights the relevance of using optimized protocols and multiple endpoints to analyze the potential toxicity of AgNPs and to obtain reliable and comparable results.

Biological Effect of Silver-modified Nanostructured Titanium Dioxide in Cancer

BACKGROUND/AIM

Nanomedicine is a promising scientific field that exploits the unique properties of innovative nanomaterials, providing alternative solutions in diagnostics, prevention and therapeutics. Titanium dioxide nanoparticles (TiO2 NPs) have a great spectrum of photocatalytic antibacterial and anticancer applications. The chemical modification of TiO2 optimizes its bioactive performance. The aim of this study was the development of silver modified NPs (Ag/TiO2 NPs) with anticancer potential.

MATERIALS AND METHODS

Ag/TiO2 NPs were prepared through the sol-gel method, were fully characterized and were tested on cultured breast cancer epithelial cells (MCF-7 and MDA-MB-231). The MTT colorimetric assay was used to estimate cellular viability. Western blot analysis of protein expression along with a DNA-laddering assay were employed for apoptosis detection.

RESULTS AND CONCLUSION

We show that photo-activated Ag/TiO2 NPs exhibited significant cytotoxicity on the highly malignant MDA-MB-231 cancer cells, inducing apoptosis, while MCF-7 cells that are characterized by low invasive properties were unaffected under the same conditions.

Broiler welfare is preserved by long-term low-dose oral exposure to zinc oxide nanoparticles: preliminary study

The potential public health risk through utilizing of zinc oxide nanoparticles (ZnO NPs) in food constitutes the major obstacle to the expansion of nanoparticle (NP) in food industry. Liver histology, bone marrow and liver genotoxicity, immunity, and oxidant status were investigated upon long-term ZnO NPs feed supplementation. One hundred and sixty male IR (Indian River) chicks were randomly allocated to one of the four dietary treatments: control, ZnO NPs at 10, 20, or 40 mg/kg for 42 days. This study revealed non-significant hepatic histopathological alterations and DNA damage and the treatment had no influence on body and organ weights, liver enzymes, lipid peroxidation (MDA), IgG, IgM, and interferon gamma (IFN-γ). This study suggests that low-dose (< 40 mg/kg diet) long-term ZnO NPs supplementation to broiler chicks has no observed potential adverse effects on normal histology of the liver, blood physiology, immune system, and DNA damage of liver and bone marrows, which are critical features for validating ZnO NPs for use in food. Further studies are required to evaluate the probable withdrawal period of ZnO NPs before approval as a dietary supplement in broiler or livestock diets.

Nanomedicine: Photo-activated nanostructured titanium dioxide, as a promising anticancer agent

The multivariate condition of cancer disease has been approached in various ways, by the scientific community. Recent studies focus on individualized treatments, minimizing the undesirable consequences of the conventional methods, but the development of an alternative effective therapeutic scheme remains to be held. Nanomedicine could provide a solution, filling this gap, exploiting the unique properties of innovative nanostructured materials. Nanostructured titanium dioxide (TiO₂) has a variety of applications of daily routine and of advanced technology. Due to its biocompatibility, it has also a great number of biomedical applications. It is now clear that photo-excited TiO₂ nanoparticles, induce generation of pairs of electrons and holes which react with water and oxygen to yield reactive oxygen species (ROS) that have been proven to damage cancer cells, triggering controlled cellular processes. The aim of this review is to provide insights into the field of nanomedicine and particularly into the wide context of TiO₂-NP-mediated anticancer effect, shedding light on the achievements of nanotechnology and proposing this nanostructured material as a promising anticancer photosensitizer.

Influence of surfactant-tailored Mn-doped ZnO nanoparticles on ROS production and DNA damage induced in murine fibroblast cells

The present study concerns the in vitro oxidative stress responses of non-malignant murine cells exposed to surfactant-tailored ZnO nanoparticles (NPs) with distinct morphologies and different levels of manganese doping. Two series of Mn-doped ZnO NPs were obtained by coprecipitation synthesis method, in the presence of either polyvinylpyrrolidone (PVP) or sodium hexametaphosphate (SHMTP). The samples were investigated by powder X-ray Diffraction, Transmission Electron Microscopy, Fourier-Transform Infrared and Electron Paramagnetic Resonance spectroscopic methods, and N₂ adsorption-desorption analysis. The observed surfactant-dependent effects concerned: i) particle size and morphology; ii) Mn-doping level; iii) specific surface area and porosity. The relationship between the surfactant dependent characteristics of the Mn-doped ZnO NPs and their in vitro toxicity was assessed by studying the cell viability, intracellular reactive oxygen species (ROS) generation, and DNA fragmentation in NIH3T3 fibroblast cells. The results indicated a positive correlation between the specific surface area and the magnitude of the induced toxicological effects and suggested that Mn-doping exerted a protective effect on cells by diminishing the pro-oxidative action associated with the increase in the specific BET area. The obtained results support the possibility to modulate the in vitro toxicity of ZnO nanomaterials by surfactant-controlled Mn-doping.

Exposure to ZnO/TiO2 Nanoparticles Affects Health Outcomes in Cosmetics Salesclerks

Concerns about the effects of nanoparticles (NPs) on human health are being raised by researchers because the risks of nanocosmetics like sunscreen are unknown. We explored the association between urinary oxidative stress markers and exposure of cosmetics salesclerks to 20 cosmetics that might contain titanium dioxide (TiO₂)/zinc oxide (ZnO) NPs. We then recruited 40 cosmetics salesclerks and 24 clothing salesclerks and categorized them based on their exposure to ZnO and TiO₂ NPs. Nineteen and 15 samples met the EU definition for TiO₂ and ZnO nanomaterials, respectively. Participants with a higher co-exposure index of ZnO and TiO₂ NPs had a significantly higher base level of urinary 8-hydroxy-2′-deoxyguanosin (8-OHdG) concentrations than the lower co-exposure group (5.82 vs. 2.85 ng/mL, p < 0.001). After potential confounding factors had been adjusted for, the TiO₂ and ZnO NP co-exposure index was significantly positively associated with the urinary 8-OHdG base concentration (β = 0.308, 95% CI = 0.106 to 0.510) and the creatinine-adjusted concentration (β = 0.486, 95% CI = 0.017 to 0.954). Current evidence suggests that the likelihood of harm from using sunscreens containing nanoparticles might result in higher urinary 8-OHdG. However, our limited number and types of sample cosmetics might underestimate the risk.

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

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

Thermodynamic Parameters at Bio-Nano Interface and Nanomaterial Toxicity: A Case Study on BSA Interaction with ZnO, SiO2, and TiO2

Understanding nanomaterial (NM)-protein interactions is a key issue in defining the bioreactivity of NMs with great impact for nanosafety. In the present work, the complex phenomena occurring at the bio/nano interface were evaluated in a simple case study focusing on NM-protein binding thermodynamics and protein stability for three representative metal oxide NMs, namely, zinc oxide (ZnO; NM-110), titanium dioxide (TiO₂; NM-101), and silica (SiO₂; NM-203). The thermodynamic signature associated with the NM interaction with an abundant protein occurring in most cell culture media, bovine serum albumin (BSA), has been investigated by isothermal titration and differential scanning calorimetry. Circular dichroism spectroscopy offers additional information concerning adsorption-induced protein conformational changes. The BSA adsorption onto NMs is enthalpy-controlled, with the enthalpic character (favorable interaction) decreasing as follows: ZnO (NM-110) > SiO₂ (NM-203) > TiO₂ (NM-101). The binding of BSA is spontaneous, as revealed by the negative free energy, ΔG, for all systems. The structural stability of the protein decreased as follows: TiO₂ (NM-101) > SiO₂ (NM-203) > ZnO (NM-110). As protein binding may alter NM reactivity and thus the toxicity, we furthermore assessed its putative influence on DNA damage, as well as on the expression of target genes for cell death (RIPK1, FAS) and oxidative stress (SOD1, SOD2, CAT, GSTK1) in the A549 human alveolar basal epithelial cell line. The enthalpic component of the BSA-NM interaction, corroborated with BSA structural stability, matched the ranking for the biological alterations, i.e., DNA strand breaks, oxidized DNA lesions, cell-death, and antioxidant gene expression in A549 cells. The relative and total content of BSA in the protein corona was determined using mass-spectrometry-based proteomics. For the present case study, the thermodynamic parameters at bio/nano interface emerge as key descriptors for the dominant contributions determining the adsorption processes and NMs toxicological effect.

Biomedical Applications of TiO2 Nanostructures: Recent Advances

Titanium dioxide (TiO2) nanostructures are one of the most plentiful compounds that have emerged in various fields of technology such as medicine, energy and biosensing. Various TiO2 nanostructures (nanotubes [NTs] and nanowires) have been employed in photoelectrochemical (PEC) biosensing applications, greatly enhancing the detection of targets. TiO2 nanostructures, used as reinforced material or coatings for the bare surface of titanium implants, are excellent additive materials to compensate titanium implants deficiencies-like poor surface interaction with surrounding tissues-by providing nanoporous surfaces and hierarchical structures. These nanostructures can also be loaded by diversified drugs-like osteoporosis drugs, anticancer and antibiotics-and used as local drug delivery systems. Furthermore, TiO2 nanostructures and their derivatives are new emerging antimicrobial agents to overcome human pathogenic microorganisms. However, like all other nanomaterials, toxicity and biocompatibility of TiO2 nanostructures must be considered. This review highlights recent advances, along with the properties and numerous applications of TiO2-based nanostructure compounds in nano biosensing, medical implants, drug delivery and antibacterial fields. Moreover, in the present study, some recent advances accomplished on the pharmaceutical applications of TiO2 nanostructures, as well as its toxicity and biocompatibility, are presented.

Zinc oxide nanoparticles for therapeutic purposes in cancer medicine

Zinc oxide nanoparticles are characterized by a good biocompatibility while providing a versatile potential as innovative therapeutic agents in cancer medicine.

Antibacterial effects of graphene- and carbon-nanotube-based nanohybrids on Escherichia coli: Implications for treating multidrug-resistant bacteria

Some nanomaterials including Fe⁰, Ag⁰, and ZnO are well known for their antibacterial effects. However, very few studies have examined antibacterial effects of nanohybrids. Given that metal oxides, mainly ZnO and TiO₂, are known to increase mobility, surface area, and photocatalysis when combined with carbon-based nanomaterials, ZnO- and TiO₂-conjugated carbon nanotube and graphene oxide nanohybrids were investigated for their antibacterial effects on Escherichia coli (DH5α, a multidrug-resistant coliform bacterium). Graphene-oxide (GO)-based nanohybrids (ZnO-GO and TiO₂-GO) induced increased dispersion compared to carbon-nanotube (CNT)-based nanohybrids (ZnO-CNT and TiO₂-CNT). Among the four types of nanohybrids, ZnO-conjugated nanohybrids exhibited a higher antibacterial property, resulting in the antibacterial effect (measured with growth inhibition of cells) in the order ZnO-GO > ZnO-CNT > TiO₂-GO > TiO₂-CNT. Among four possible antibacterial mechanisms (generation of reactive oxygen species (ROS), physicochemical characteristics, the steric effect, and release of metal ions), a primary mechanism-ROS generation-was identified; whereas, physicochemical characteristics and the steric effect were part of contributing mechanisms. The increasing dispersion of TiO₂/ZnO on GO may have contributed to the antibacterial effects due to increasing surface areas. Similarly, significant damages to E. coli cell membranes were found by the GO sheet with its sharp edges. Our results suggest that applying GO-based ZnO or TiO₂ could be an effective antibacterial method, especially for the treatment of multidrug-resistant bacteria in the water.

A Brief Review about the Role of Nanomaterials, Mineral-Organic Nanoparticles, and Extra-Bone Calcification in Promoting Carcinogenesis and Tumor Progression

People come in contact with a huge number of nanoparticles (NPs) throughout their lives, which can be of both natural and anthropogenic origin and are capable of entering the body through swallowing, skin penetration, or inhalation. In connection with the expanding use of nanomaterials in various industrial processes, the question of whether there is a need to study the potentially adverse effects of NPs on human health becomes increasingly important. Despite the fact that the nature and the extent of damage caused depends on the chemical and the physical characteristics of individual NPs, there are also general mechanisms related to their toxicity. These mechanisms include the ability of NPs to translocate to various organs through endocytosis, as well as their ability to stimulate the production of reactive oxygen species (ROS), leading to oxidative stress, inflammation, genotoxicity, metabolic changes, and potentially carcinogenesis. In this review, we discuss the main characteristics of NPs and the effects they cause at both cellular and tissue levels. We also focus on possible mechanisms that underlie the relationship of NPs with carcinogenesis. We briefly summarize the main concepts related to the role of endogenous mineral organic NPs in the development of various human diseases and their participation in extra-bone calcification. Considering data from both our studies and those published in scientific literature, we propose the revision of some ideas concerning extra-bone calcification, since it may be one of the factors associated with the initiation of the mechanisms of immunological tolerance.

Fabrication of Hybrid Materials from Titanium Dioxide and Natural Phenols for Efficient Radical Scavenging against Oxidative Stress

Oxidative stress caused by free radicals is one of the great threats to inflict intracellular damage. Here, we report a convenient approach to the synthesis, characterization, and evaluation of the radical activity of titanium-based composites. We have investigated the potential of natural antioxidants (curcumin, quercetin, catechin, and vitamin E) as radical scavengers and stabilizers. The titanium oxide composites were prepared via three steps including sol-gel synthesis, carboxylation, and esterification. The characterization of the titanium-phenol composites was carried out by FTIR, PXRD, UV-vis and SEM methods. The radical scavenging ability of the novel materials was evaluated using DPPH and an in vitro LPO assay using isolated rat liver mitochondria. The novel materials exhibit both a higher stability and an antioxidant activity in comparison to bare TiO₂. It was found that curcumin and quercetin based composites show the highest antioxidant efficiency among the composites under study followed by catechin and vitamin E based materials. The results from an MTT assay carried out on the Caco-2 cell line indicate that the composites do not contribute to the cytotoxicity in vitro. This study demonstrates that a combination of powerful antioxidants with titanium dioxide can change its functional properties and provide a convenient strategy against oxidative stress.

Cytotoxic and proinflammatory responses induced by ZnO nanoparticles in in vitro intestinal barrier

ZnO nanoparticles (NPs) are widely used nowadays, thus the gastrointestinal exposure to ZnO NPs is likely to be relevant and the effects on the intestinal barrier should be investigated. Polarized Caco-2 cells were exposed from the apical (Ap) and basolateral (Bl) compartments to increasing concentrations (0, 10, 50 and 100 μg/mL) of sonochemical (sono) and commercial ZnO NPs. The transepithelial electrical resistance (TEER), cell viability, proinflammatory cytokine release and presence of protein oxidative damage were evaluated after exposure. TEER was not significantly affected by Ap exposure to either sono or commercial ZnO NPs at any tested concentrations. After Bl exposure to sono ZnO NPs (all the concentrations) and to 100 μg/mL of commercial ZnO NPs TEER was decreased (P < 0.05). Ap and Bl exposure to 100 μg/mL sono ZnO NPs and Ap exposure to 50 μg/mL commercial ZnO NPs induced a significant (P < 0.05) release of interleukin-6. A significant (P < 0.05) release of interleukin-8 was observed after Ap exposure to ZnO NPs at 100 μg/mL and after Bl exposure to sono ZnO NPs at 100 μg/mL. Ap or Bl exposure to sono or commercial ZnO NPs did not affect tumour necrosis factor-alpha secretion or protein sulphydryl oxidation. In conclusion, the ZnO NP exposure from the Ap compartment appeared almost safe, while the exposure through the basal compartment appeared to be more hazardous and the different NP size and crystallinity seem to affect the mode of action, but further studies are necessary to elucidate better these toxicity mechanisms.

The cytotoxic properties of zinc oxide nanoparticles on the rat liver and spleen, and its anticancer impacts on human liver cancer cell lines

INTRODUCTION

Due to their unique properties including cellular uptake and the delivery efficiency to biological systems, nanoparticles are used in various preclinical and clinical applications. The aim of this study was to investigate the toxicity impacts of zinc oxide nanoparticles (ZnO-NPs) on morphology and functionality of the rat's liver and spleen and illustrated its safe-therapeutic doses.

METHODS

The 28 female Swiss albino rats (180-220 g) and two human hepatocyte cell lines (HepG2 and HUH7) were designed as an in vivo and in vitro study, respectively. Samples were treated with certain doses of ZnO-NPs. The rat's liver morphology and functionality and apoptotic genes expression profile (Bax, Bcl-2, and P53) were analyzed to detect the cytotoxicity and antitumor impacts of ZnO-NPs, respectively.

RESULTS

The results showed a positive significant association between the increasing doses of ZnO-NPs and alanine aminotransferase/aspartate aminotransferase values. Moreover, a meaningful correlation was detected between the rat's liver and spleen weight and ZnO-NPs doses. Furthermore, the histopathological analysis of rat's liver showed the individual cytotoxic properties of ZnO-NPs. Finally, the positive significant correlation was detected among the expression of Bax and P53 genes with ZnO-NPs. In addition, the negative correlation was demonstrated between the expression of Bcl-2 and ZnO-NPs.

CONCLUSION

In general, in the current study, the antitumor effects of ZnO-NPs were confirmed by the enhancement of P53 and Bax genes expression profile, which are indicated the apoptotic induction in HUH7 cell line. Moreover, we introduced a safe-clinical ZnO-NPs dosage, have antitumor effects.

Application of radially grown ZnO nanowires on poly-l-lactide microfibers complexed with a tumor antigen for cancer immunotherapy

Zinc oxide (ZnO)-based nanocomposites have shown promising potential for various biomedical applications, including vaccine development, owing to their multifunctionality and biocompatibility. Here, we synthesized radially grown ZnO nanowires (NWs) on poly-l-lactic acid (PLLA) microfibers with unique 3-dimensional structure and applied them as therapeutic cancer vaccines. This inorganic-organic hybrid nanocomposite has mild cellular toxicity but efficiently delivers a tumor antigen into dendritic cells, cellular bridges between innate and adaptive immunity, to stimulate them to express inflammatory cytokines and activation surface markers. We also demonstrated that the hybrid nanocomposites successfully induce tumor antigen-specific cellular immunity and significantly inhibit tumor growth in vivo. ZnO NWs on PLLA fibers systemically reduced immune suppressive TReg cells and enhanced the infiltration of T cells into tumor tissues, compared to mice immunized with PLLA fibers coated with the antigen. Our current findings open a new avenue in extending the biomedical application of inorganic metal oxide-inert organic hybrid nanocomposites as a novel vaccine platform.

In Vitro Approaches for Assessing the Genotoxicity of Nanomaterials

Genotoxicity is associated with serious health effects and includes different types of DNA lesions, gene mutations, structural chromosome aberrations involving breakage and/or rearrangements of chromosomes (referred to as clastogenicity) and numerical chromosome aberrations (referred to as aneuploidy). Assessing the potential genotoxic properties of chemicals, including nanomaterials (NMs), is a key element in regulatory safety assessment. State-of-the-art genotoxicity testing includes a battery of assays covering gene mutations, structural and numerical chromosome aberrations. Typically various in vitro assays are performed in the first tier. It is not very likely that NMs may induce as yet unknown types of genotoxic damage beyond what is already known for chemicals. Thus, principles of genotoxicity testing as established for chemicals should be applicable to NMs as well. However, established test guidelines (i.e., OECD TG) may require adaptations for NM testing, as currently under discussion at the OECD. This chapter gives an overview of genotoxicity testing of NMs in vitro based on experiences from various research projects. We recommend a combination of a mammalian gene mutation assay (at either Tk or HPRT locus), the in vitro comet assay, and the cytokinesis-block micronucleus assay, which are discussed in detail here. In addition we also include the Cell Transformation Assay (CTA) as a promising novel test for predicting NM-induced cell transformation in vitro.

Human keratinocytes adapt to ZnO nanoparticles induced toxicity via complex paracrine crosstalk and Nrf2-proteasomal signal transduction

Zinc oxide nanoparticles (Nano-ZnO) is currently one of the most extensively used inorganic particles in a wide range of skin care and consumable products. Therefore, examining the biological effects of Nano-ZnO, especially in the non-cytotoxic levels, thus holds important contemporary practical implications. Herein, our study demonstrates that long-term conditioning of human keratinocytes (HaCaTs) to non-cytoxic dose of Nano-ZnO (∼100 nm) can induce an adaptive response, leading to an enhancement of the cells tolerance against cytotoxic level of Nano-ZnO. It was found that the Nano-ZnO induced adaptive alteration is mediated by a strong synergism between the generation of reactive oxygen species (ROS) flares by a sub-population of cells that are loaded with Nano-ZnO and upregulation of several pro-inflammatory transcripts. Further studies revealed activation of the nuclear factor (erythroid-derived 2)-like 2 (Nrf-2) stress response pathway and the associated downstream sustained augmented level of chymotrypsin-like 20 s proteasome activity to be the major mechanism underpinning this phenomenon. Interestingly, these cytoprotective responses can further aid the Nano-ZnO conditioned HaCaT cells to cross-adapt to harmful effects of ultraviolet-A (UVA) by reducing radiation-induced DNA damage. Our findings have unveiled a range of previously undocumented potent and exploitable bioeffects of Nano-ZnO induced ROS mediated signaling within the framework of nano-adaptation.

Effects of ZnO nanoparticles on intestinal function and structure in normal/high fat diet-fed rats and Caco-2 cells

Aim: The present study was carried out to determine the effects of ZnO nanoparticles (ZnO–NPs) on intestinal function and pathophysiological alteration. Materials & methods: ZnO–NPs were synthesized and their characterizations were performed using various techniques. The Wistar male rats fed with normal diet and/or high fat diet (HFD) for 8 weeks and then orally received ZnO–NPs (5, 50 and 100 mg/kg bodyweight) for 28 days. The oxidative stress (SOD, CAT, GPx), inflammatory (TNF-α, iNOS) and apoptosis pathways (Bcl2, Bax and p53) genes expression and protein levels were measured by real-time polymerase chain reaction and available kit, respectively. The activity of Caspase-3, antioxidant capacity, as well as inflammatory markers were determined. The histological alterations of the large and small intestine were also evaluated with haematoxylin and eosin (H&E) as well as TdT dUTP nick end labeling (TUNEL) assay. The biochemical factors, viability and antioxidant activity were also determined in Caco-2 cells. Results: It was found that the antioxidant enzymes activity and genes expression markedly increased, while inflammatory and apoptosis pathways and TNF-α levels significantly decreased in the intestine of HFD-fed rats treated with 5 mg/kg ZnO–NPs. Intestinal morphological changes were also restored by 5 mg/kg ZnO–NPs in HFD group. Conclusion: Treatment of rats with 50 and 100 mg/kg ZnO–NPs significantly induced intestinal injury, while treatment with 5 mg/kg ZnO nanoparticle normalized intestinal functions and structure. This study showed the synergistic effects of ZnO–NPs and HFD administration on liver enzyme, oxidative stress, apoptosis, inflammation, morphological changes and cell toxicity.

The Advancing of Zinc Oxide Nanoparticles for Biomedical Applications

Zinc oxide nanoparticles (ZnO NPs) are used in an increasing number of industrial products such as rubber, paint, coating, and cosmetics. In the past two decades, ZnO NPs have become one of the most popular metal oxide nanoparticles in biological applications due to their excellent biocompatibility, economic, and low toxicity. ZnO NPs have emerged a promising potential in biomedicine, especially in the fields of anticancer and antibacterial fields, which are involved with their potent ability to trigger excess reactive oxygen species (ROS) production, release zinc ions, and induce cell apoptosis. In addition, zinc is well known to keep the structural integrity of insulin. So, ZnO NPs also have been effectively developed for antidiabetic treatment. Moreover, ZnO NPs show excellent luminescent properties and have turned them into one of the main candidates for bioimaging. Here, we summarize the synthesis and recent advances of ZnO NPs in the biomedical fields, which will be helpful for facilitating their future research progress and focusing on biomedical fields.

Ingested engineered nanomaterials: state of science in nanotoxicity testing and future research needs

BACKGROUND

Engineered nanomaterials (ENM) are used extensively in food products to fulfill a number of roles, including enhancement of color and texture, for nutritional fortification, enhanced bioavailability, improved barrier properties of packaging, and enhanced food preservation. Safety assessment of ingested engineered nanomaterials (iENM) has gained interest in the nanotoxicology community in recent years. A variety of test systems and approaches have been used for such evaluations, with in vitro monoculture cell models being the most common test systems, owing to their low cost and ease-of-use. The goal of this review is to systematically assess the current state of science in toxicological testing of iENM, with particular emphasis on model test systems, their physiological relevance, methodological strengths and challenges, realistic doses (ranges and rates), and then to identify future research needs and priorities based on these assessments.

METHODS

Extensive searches were conducted in Google Scholar, PubMed and Web of Science to identify peer-reviewed literature on safety assessment of iENM over the last decade, using keywords such as "nanoparticle", "food", "toxicity", and combinations thereof. Relevant literature was assessed based on a set of criteria that included the relevance of nanomaterials tested; ENM physicochemical and morphological characterization; dispersion and dosimetry in an in vitro system; dose ranges employed, the rationale and dose realism; dissolution behavior of iENM; endpoints tested, and the main findings of each study. Observations were entered into an excel spreadsheet, transferred to Origin, from where summary statistics were calculated to assess patterns, trends, and research gaps.

RESULTS

A total of 650 peer-reviewed publications were identified from 2007 to 2017, of which 39 were deemed relevant. Only 21% of the studies used food grade nanomaterials for testing; adequate physicochemical and morphological characterization was performed in 53% of the studies. All in vitro studies lacked dosimetry and 60% of them did not provide a rationale for the doses tested and their relevance. Only 12% of the studies attempted to consider the dissolution kinetics of nanomaterials. Moreover, only 1 study attempted to prepare and characterize standardized nanoparticle dispersions.

CONCLUSION

We identified 5 clusters of factors deemed relevant to nanotoxicology of food-grade iENM: (i) using food-grade nanomaterials for toxicity testing; (ii) performing comprehensive physicochemical and morphological characterization of iENM in the dry state, (iii) establishing standard NP dispersions and their characterization in cell culture medium, (iv) employing realistic dose ranges and standardized in vitro dosimetry models, and (v) investigating dissolution kinetics and biotransformation behavior of iENM in synthetic media representative of the gastrointestinal (GI) tract fluids, including analyses in a fasted state and in the presence of a food matrix. We discussed how these factors, when not considered thoughtfully, could influence the results and generalizability of in vitro and in vivo testing. We conclude with a set of recommendations to guide future iENM toxicity studies and to develop/adopt more relevant in vitro model systems representative of in vivo animal and human iENM exposure scenarios.

Role of modification route for zinc oxide nanoparticles on protein structure and their effects on glioblastoma cells

Zinc oxide nanoparticles (ZnO) are presented as potential cancer therapeutic agent based on their surface properties. In this study, the most abundant blood proteins, albumin, fibrinogen and apo-transferrin, were covalently bound (c-ZnO NPs) and nonspecifically adsorbed (n-ZnO NPs) onto ZnO NPs to evaluate the role of modification route on protein structure and their effects on glioblastoma cells. The success of modification and structures of proteins on ZnO NPs were characterized with FT-IR. It was found that non-covalent interaction significantly damaged the secondary structure of proteins compared to those covalently attached to the ZnO nanoparticle. The effects of modified ZnO NPs were investigated by evaluating viability, cycle, and death mechanisms of glioblastoma (U373) cells. n-ZnO NPs were found more toxic compared to the pristine and c-ZnO NPs. However, c-ZnO NPs with albumin and apo-transferrin both perturbed the cell cycle function, and decreased the necrotic cell death rate of U373 cells below toxic concentration, suggesting their potential curative effect on glioblastoma cells.

Nano titanium exposure induces dose- and size-dependent cytotoxicity on human epithelial lung and colon cells

The productions as well as use of Titanium dioxide nanoparticles (TNPs) were rapidly increasing in the present nano-world. The TNP becomes an inevitable part our daily life in the form of cosmeceutical, bio-medical, and nano-pharmaceutical applications. The TNPs are either inhaled or ingested into the human body through common routes of exposure like the lungs and the oral-gastrointestinal tract (GIT). Human lung and colon were exposed to test particles, TNP 18 nm (TNP 18), TNP 30 nm (TNP 30), and TNP 87 nm (TNP 87) with a dose range 0.1-100 µg/ml. The effect of exposure was determined using MTT, LDH, and DCFH-DA methods. The TNP 18, TNP 30, and TNP 87 significantly (p < 0.001) reduced cell viability in a dose- and a size-dependent manner in 60 and 100 µg/ml. The lowest IC₅₀ values 21.80 and 24.83 µg/ml were observed in A549 and Caco-2 for the smallest size, TNP 18. Further, for TNP 30, IC₅₀ values were 23.30 and 28.59 µg/ml compared to Nano QTZ 43.82 and 45.86 µg/ml. The EC₂₅ values of LDH leakage were 5.83 and 9.50 µg/ml for TNP 18 in lung and colon cells. Besides, ROS levels increased significantly at doses 60 (p < 0.01) and 100 (p < 0.001) µg/ml in two cells. The smaller size particle, TNP 18 has produced a significant (p < 0.05) toxic effect at the lowest dose i.e., 10 µg/ml. Therefore, we conclude that TNP 18, TNP 30, and TNP 87 induced a dose- and size-dependent cytotoxicity via decreased cell viability, increased LDH and ROS levels by in vitro methods.

Analysis of nanoparticle biomolecule complexes

Nanoparticles exposed to biological fluids adsorb biomolecules on their surface forming a biomolecular corona. This corona determines, on a molecular level, the interactions and impact the newly formed complex has on cells and organisms. The corona formation as well as the physiological and toxicological relevance are commonly investigated. However, an acknowledged but rarely addressed problem in many fields of nanobiotechnology is aggregation and broadened size distribution of nanoparticles following their interactions with the molecules of biological fluids. In blood serum, TiO₂ nanoparticles form complexes with a size distribution from 30 nm to more than 500 nm. In this study we have separated these complexes, with good resolution, using preparative centrifugation in a sucrose gradient. Two main apparent size populations were obtained, a fast sedimenting population of complexes that formed a pellet in the preparative centrifugation tube, and a slow sedimenting complex population still suspended in the gradient after centrifugation. Concentration and surface area dependent differences are found in the biomolecular corona between the slow and fast sedimenting fractions. There are more immunoglobulins, lipid binding proteins, and lipid-rich complexes at higher serum concentrations. Sedimentation rate and the biomolecular corona are important factors for evaluating any experiment including nanoparticle exposure. Our results show that traditional description of nanoparticles in biological fluids is an oversimplification and that more thorough characterisations are needed.

The unrecognized occupational relevance of the interaction between engineered nanomaterials and the gastro-intestinal tract: a consensus paper from a multidisciplinary working group

BACKGROUND

There is a fundamental gap of knowledge on the health effects caused by the interaction of engineered nanomaterials (ENM) with the gastro-intestinal tract (GIT). This is partly due to the incomplete knowledge of the complex physical and chemical transformations that ENM undergo in the GIT, and partly to the widespread belief that GIT health effects of ENM are much less relevant than pulmonary effects. However, recent experimental findings, considering the role of new players in gut physiology (e.g. the microbiota), shed light on several outcomes of the interaction ENM/GIT. Along with this new information, there is growing direct and indirect evidence that not only ingested ENM, but also inhaled ENM may impact on the GIT. This fact, which may have relevant implications in occupational setting, has never been taken into consideration. This review paper summarizes the opinions and findings of a multidisciplinary team of experts, focusing on two main aspects of the issue: 1) ENM interactions within the GIT and their possible consequences, and 2) relevance of gastro-intestinal effects of inhaled ENMs. Under point 1, we analyzed how luminal gut-constituents, including mucus, may influence the adherence of ENM to cell surfaces in a size-dependent manner, and how intestinal permeability may be affected by different physico-chemical characteristics of ENM. Cytotoxic, oxidative, genotoxic and inflammatory effects on different GIT cells, as well as effects on microbiota, are also discussed. Concerning point 2, recent studies highlight the relevance of gastro-intestinal handling of inhaled ENM, showing significant excretion with feces of inhaled ENM and supporting the hypothesis that GIT should be considered an important target of extrapulmonary effects of inhaled ENM.

CONCLUSIONS

In spite of recent insights on the relevance of the GIT as a target for toxic effects of nanoparticles, there is still a major gap in knowledge regarding the impact of the direct versus indirect oral exposure. This fact probably applies also to larger particles and dictates careful consideration in workers, who carry the highest risk of exposure to particulate matter.

Zinc oxide nanoparticles induce toxic responses in human neuroblastoma SHSY5Y cells in a size-dependent manner

Due to the widespread applications of zinc oxide nanoparticles (ZnO NPs), the potential exposure of workers, consumers, and scientists to these particles has increased. This potential for exposure has attracted extensive attention in the science community. Many studies have examined the toxicological profile of ZnO NPs in the immune system, digestive system, however, information regarding the toxicity of ZnO NPs in the nervous system is scarce. In this study, we detected the cytotoxicity of two types of ZnO NPs of various sizes - ZnOa NPs and ZnOb NPs - and we characterized the shedding ability of zinc ions within culture medium and the cytoplasm. We found that reactive oxygen species played a crucial role in ZnO NP-induced cytotoxicity, likely because zinc ions were leached from ZnO NPs. Apoptosis and cytoskeleton changes were also toxic responses induced by the ZnO NPs, and ZnOb NPs induced more significant toxic responses than ZnOa NPs in SHSY5Y cells. In conclusion, ZnO NPs induced toxic responses in SHSY5Y cells in a size-dependent manner, which can probably be attributed to their ion-shedding ability.

Oxidative Stress and Genotoxicity of Zinc Oxide Nanoparticles to Pseudomonas Species, Human Promyelocytic Leukemic (HL-60), and Blood Cells

In the present study, toxicity of commercial zinc oxide nanoparticles (ZnO NPs) was studied on the bacterium Pseudomonas sp., human promyelocytic leukemia (HL-60) cells, and peripheral blood mononuclear cells (PBMC). The toxicity was assessed by measuring growth, cell viability, and protein expression in bacterial cell. The bacterial growth and viability decreased with increasing concentrations of ZnO NP. Three major proteins, ribosomal protein L1 and L9 along with alkyl hydroperoxides reductase, were upregulated by 1.5-, 1.7-, and 2.0-fold, respectively, after ZnO NP exposure. The results indicated oxidative stress as the leading cause of toxic effect in bacteria. In HL-60 cells, cytotoxic and genotoxic effects along with antioxidant enzyme activity and reactive oxygen species (ROS) generation were studied upon ZnO NP treatment. ZnO NP exhibited dose-dependent increase in cell death after 24-h exposure. The DNA-damaging potential of ZnO NP in HL-60 cells was maximum at 0.05 mg/L concentration. Comet assay showed 70-80% increase in tail DNA at 0.025 to 0.05 mg/L ZnO NP concentration. A significant increase of 1.6-, 1.4-, and 2.0-fold in ROS level was observed after 12 h. Genotoxic potential of ZnO NPs was also demonstrated in PBMC through DNA fragmentation. Thus, ZnO NP, besides being an essential element having antibacterial activity, also showed toxicity towards human cells (HL-60 and PBMC).

Nanoparticle-induced oxidation of corona proteins initiates an oxidative stress response in cells

Titanium dioxide nanoparticles (TiO₂ NPs), used as pigments and photocatalysts, are ubiquitous in our daily lives. Previous work has observed cellular oxidative stress in response to the UV-excitation of photocatalytic TiO₂ NPs. In comparison, most human exposure to TiO₂ NPs takes place in the dark, in the lung following inhalation or in the gut following consumption of TiO₂ NP food pigment. Our spectroscopic characterization shows that both photocatalytic and food grade TiO₂ NPs, in the dark, generate low levels of reactive oxygen species (ROS), specifically hydroxyl radicals and superoxides. These ROS oxidize serum proteins that form a corona of proteins on the NP surface. This protein layer is the interface between the NP and the cell. An oxidized protein corona triggers an oxidative stress response, detected with PCR and western blotting. Surface modification of TiO₂ NPs to increase or decrease surface defects correlates with ROS generation and oxidative stress, suggesting that NP surface defects, likely oxygen vacancies, are the underlying cause of TiO₂ NP-induced oxidative stress.