In vitro toxicity assessment of silver nanoparticles in the presence of phenolic compounds--preventive agents against the harmful effect?

Epigallocatechin gallate alleviated the in vivo toxicity of ZnO nanoparticles to mouse intestine

To evaluate the oral toxicity of nanoparticles (NPs), it is necessary to consider the interactions between NPs and nutrient molecules. Recently, we reported that epigallocatechin gallate (EGCG), a healthy component in green tea, alleviated the toxicity of ZnO NPs to 3D Caco-2 spheroids in vitro. The present study investigated the combined effects of EGCG and ZnO NPs to mice in vivo. Mice were administrated with 35 or 105 mg/kg bodyweight ZnO NPs with or without the presence of 80 mg/kg bodyweight EGCG via gastric route, once a day, for 21 days, and the influences of EGCG on the toxicity of ZnO NPs to intestine were investigated. We found that EGCG altered the colloidal properties of ZnO NPs both in water and artificial intestine juice. As expected, ZnO NPs induced toxicological effects, such as decreased bodyweight, higher Chiu's scores, and ultrastructural changes in intestine, whereas EGCG alleviated these effects. Combined exposure to EGCG and ZnO NPs also changed trace element levels in mouse intestine. For example, the levels of Ti, Co, and Ni were only significantly elevated after co-exposure to EGCG and ZnO NPs, and Fe levels were only significantly decreased by ZnO NPs. Western blot analysis suggested that tight junction (TJ) and endoplasmic reticulum (ER) proteins were elevated by ZnO NPs, but EGCG inhibited this trend. Combined, these data suggested that gastric exposure to ZnO NPs induced intestinal damage, trace element imbalance, and TJ/ER protein expression in mouse intestine, whereas EGCG alleviated these effects of ZnO NPs.

Enhanced antibacterial effect and biodegradation of coating via dual-in-situ growth based on carboxymethyl cellulose

The lack of antimicrobial effect of commercial paper coating for food packaging makes it difficult to prevent food spoilage and harms the environment by non-biodegradation. Herein, carboxymethyl cellulose (CMC) provides negatively charged sites for anchoring Ag⁺ and Zn²⁺ to grow AgNPs and ZIF-8 in situ on its molecular chains. The ZIF-8/AgNPs@CMC paper coating has excellent synergistic antibacterial activity to prolong the shelf-life of food. It not only has good thermal stability but binds closely to the paper and its adhesion force reaches 628.9 nN. Besides, the ZIF-8/AgNPs@CMC coated paper has better mechanical properties, water vapor barrier, and resists water solubility. Interestingly, due to the confinement effect of ZIF-8, the cumulative release of AgNPs after 168 h is only 2.66 % to avoid possible food safety risks. Especially, the coating can be almost biodegraded in the soil after 30 days, which provides the possibility to replace the non-biodegradable coatings in food packaging.

How Nanoparticles Open the Paracellular Route of Biological Barriers: Mechanisms, Applications, and Prospects

Biological barriers are essential physiological protective systems and obstacles to drug delivery. Nanoparticles (NPs) can access the paracellular route of biological barriers, either causing adverse health impacts on humans or producing therapeutic opportunities. This Review introduces the structural and functional influences of NPs on the key components that govern the paracellular route, mainly tight junctions, adherens junctions, and cytoskeletons. Furthermore, we evaluate their interaction mechanisms and address the influencing factors that determine the ability of NPs to open the paracellular route, which provides a better knowledge of how NPs can open the paracellular route in a safer and more controllable way. Finally, we summarize limitations in the research models and methodologies of the existing research in the field and provide future research direction. This Review demonstrates the in-depth causes for the reversible opening or destruction of the integrity of barriers generated by NPs; more importantly, it contributes insights into the design of NP-based medications to boost paracellular drug delivery efficiency.

The role of MOF based nanocomposites in the detection of phenolic compounds for environmental remediation- A review

Phenolic compounds would be the emerging pollutant by 2050, because of their wide spread applicability in daily life and therefore the adoption of suitable detection methods in which identification and separation of isomers is highly desirable. Owing to the fascinating features, Metal-organic framework (MOF), a class of reticular materials holds a large surface area with tunable shape and adjustable porosity will provide strong interaction with analytes through abundant functional groups resulting in high selectivity towards electrochemical determination of phenolic isomers. Nevertheless, the sensing performance can still be further improved by building MOF network (intrinsic resistance) with functional (conducting) materials, resulting in MOF based nanocomposite. Herein, this review provides the summary of MOF based nanocomposites for electrochemical sensing of phenolic compounds developed from 2015. In this review, we discussed the demerits of pristine MOF as electrode materials, and the requirement of new class of MOF with functional materials such as nanomaterials, carbon nanotubes, graphene and MXene. The history and evolution of MOF nanocomposite-based materials are discussed and also featured the impressive physical and chemical properties. Besides this review discusses the factors influencing the conducting pathway and mass transport of MOF based nanocomposite for enhanced sensing performance of phenolic compounds with suitable mechanistic illustrations. Finally, the major challenges governing the determination of phenolic compounds and the future advancements required for the development of MOF based electrodes for various applications are highlighted.

Silver-Nanoparticle- and Silver-Nitrate-Induced Antioxidant Disbalance, Molecular Damage, and Histochemical Change on the Land Slug (Lehmannia nyctelia) Using Multibiomarkers

It is known that silver nanoparticles (Ag NPs) and AgNO3 have harmful effects on the surrounding organisms, which may cause damage to these organisms. Therefore, the aim of this study is to detect damage caused by Ag NPs and silver nitrate to land slugs (Lehmannia nyctelia). In this study, the slugs were exposed to various concentrations of Ag NPs and AgNO3 for 15 days. The biochemical, antioxidant, lipid peroxidation (LPO), DNA fragmentation, and histopathological endpoints were assessed after 15 days of exposure to different concentrations of Ag NPs (0.04, 0.08, 0.4, and 0.8 g/L) and silver nitrate (0.04, 0.08, 0.4, and 0.8 g/L). The results show a significant decrease in total protein, total carbohydrate, superoxide dismutase, and GST and a significant increase in total lipid, LPO, and DNA fragmentation after exposure to Ag NPs and AgNO3 for 15 days compared with the control group. Histopathiological alterations were observed in the digestive glands which were indicated by histochemical staining. We concluded that exposure to AgNO3 and Ag NPs caused oxidative stress, genetic damage and alterations in the profile of muscle proteins and histological structure in L. nyctelia.

Nutrient molecule corona: An update for nanomaterial-food component interactions

The adsorption of biological molecules to nanomaterials (NMs) will significantly impact NMs' behavior in complex microenvironments. Previously we proposed the need to consider the interactions between food components and NMs for the evaluation of oral toxicity of NMs. This review updated this concept as nutrient molecule corona, that the adsorption of nutrient molecules alters the uptake of nutrient molecules and/or NMs, as well as the signaling pathways to induce a combined toxicity due to the biologically active nature of nutrient molecules. Even with the presence of protein corona, nutrient molecules may still bind to NMs to change the identities of NMs in vivo. Furthermore, this review proposed the binding of excessive nutrient molecules to NMs to induce a combined toxicity under pathological conditions such as metabolic diseases. The structures of nutrient molecules and physicochemical properties of NMs determine nutrient molecule corona formation, and these aspects should be considered to limit the unwanted effects brought by nutrient molecule corona. In conclusion, similar to other biological molecule corona, the formation of nutrient molecule corona due to the presence of food components or excessive nutrient molecules in pathophysiological microenvironments will alter the behaviors of NMs.

Quercetin Abrogates Oxidative Neurotoxicity Induced by Silver Nanoparticles in Wistar Rats

This study aimed to investigate the oxidative neurotoxicity induced by silver nanoparticles (AgNPs) and assess the neuroprotective effects of quercetin against this toxicity. Forty adult male rats were divided into four equal groups: control, AgNPs (50 mg/kg intraperitoneally), quercetin (50 mg/kg orally), and quercetin + AgNPs. After 30 days, blood and brain tissue samples were collected for further studies. AgNP exposure increased lipid peroxidation and decreased glutathione peroxidase, catalase, and superoxide dismutase activities in brain tissue. AgNPs decreased serum acetylcholine esterase activity and γ-aminobutyric acid concentrations. AgNPs upregulated tumor necrosis factor-α, interleukin-1β, and Bax transcript levels. AgNPs reduced the transcripts of claudin-5, brain-derived neurotrophic factor, paraoxonase, nuclear factor-erythroid factor 2 (Nrf2), and Bcl-2. Histopathologically, AgNPs caused various degenerative changes and neuronal necrosis associated with glial cell reactions. AgNPs increased the immunohistochemical staining of glial fibrillary acidic protein (GFAP) in the cerebrum and cerebellum. Oral treatment with quercetin efficiently counteracted the opposing effects of AgNPs on brain tissue via modulation of tight junction proteins, Nrf2, and paraoxonase, and its positive mechanism in modulating pro-inflammatory cytokines and the downregulation of GFAP expression, and the apoptotic pathway. AgNPs also altered the severity of histopathological lesions and modulated GFAP immunostaining in the examined tissue.

Engineered nanomaterials induce alterations in biological barriers: focus on paracellular permeability

Engineered nanoparticles (ENPs) are widely used in medical diagnosis and treatment, as food additives and as energy materials. ENPs may exert adverse or beneficial effects on the human body, which may be linked to interactions with biological barriers. In this review, the authors summarize the influences of four typical metal/metal oxide nanomaterials (Ag, TiO₂, Au, ZnO nanoparticles) on the paracellular permeability of biological barriers. Disruptions on tight junctions, adhesion junctions, gap junctions and desmosomes via complex signaling pathways, such as the MAPK, PKC and ROCK signaling pathways, affect paracellular permeability. Reactive oxygen species and cytokines underlie the mechanism of ENP-triggered alterations in paracellular permeability. This review provides the information necessary for the cautious application of nanoparticles in medicine and life sciences in the future.

Protective Role of Flavonoids against Intestinal Pro-Inflammatory Effects of Silver Nanoparticles

Silver nanoparticles (AgNP) have been increasingly incorporated into food-related and hygiene products for their unique antimicrobial and preservative properties. The consequent oral exposure may then result in unpredicted harmful effects in the gastrointestinal tract (GIT), which should be considered in the risk assessment and risk management of these materials. In the present study, the toxic effects of polyethyleneimine (PEI)-coated AgNP (4 and 19 nm) were evaluated in GIT-relevant cells (Caco-2 cell line as a model of human intestinal cells, and neutrophils as a model of the intestinal inflammatory response). This study also evaluated the putative protective action of dietary flavonoids against such harmful effects. The obtained results showed that AgNP of 4 and 19 nm effectively induced Caco-2 cell death by apoptosis with concomitant production of nitric oxide, irrespective of the size. It was also observed that AgNP induced human neutrophil oxidative burst. Interestingly, some flavonoids, namely quercetin and quercetagetin, prevented the deleterious effects of AgNP in both cell types. Overall, the data of the present study provide a first insight into the promising protective role of flavonoids against the potentially toxic effects of AgNP at the intestinal level.

In vivo assessments for predicting the bioavailability of nanoencapsulated food bioactives and the safety of nanomaterials

Use of nano-sized materials to design novel delivery systems is actually a double-edged sword regarding the enhancement of absorption and bioavailability of encapsulated bioactives as well as the unpredictable phenomena inside the living cells causing health concerns. So, comprehensive investigations on the use of nanomaterials in foods and their biological fate are needed. To reach this goal, both in vitro and in vivo techniques have been extensively applied. Besides the in vitro models such as cell culture and yeast/bacteria, different live animal models like mice, rat, Drosophila melanogaster, Caenorhabditis elegans, Zebrafish and dog can be applied to study bioavailability and safety of nanodelivery systems. However, considering the low correlation between the achieved results of in vitro and in vivo assays, in vivo tests are the first priority due to providing a real physiological condition. On the other hand, uncorrelated results by in vivo assays represent a serious problem to compare them. To defeat the issues in setting an in vivo research for the nanodelivery systems, all restrictions and FDA regulations is likely to be considered to improve the assays authenticity. This review takes a comprehensive look at the different types of in vivo assays and model organisms that has been utilized for the investigation of bioavailability, release profile and possible toxicity of food-based nanomaterials so far.

An alginate-PHMB-AgNPs based wound dressing polyamide nanocomposite with improved antibacterial and hemostatic properties

Wound dressing should be impenetrable against microorganisms and it should keep the wound wet. Gauze and polyamide (PA) substrate were treated with various concentrations of AgNPs (25, 50, 75, and 100 ppm), PHMB (0.2, 0.4, 0.6, 0.8, and 1% w/v), and constant concentration of alginate (0.5% W/V) using a simple dipping method. Prepared samples were characterized by various techniques including Fourier transform infrared spectroscopy and scanning electron microscopy. The results indicated that the particles were successfully applied onto both substrates with an average diameter of particle size of 78 nm on gauze and 172 nm on the PA substrate surface (based on 50 nanoparticles). Antibacterial activity of the prepared nanocomposite against Staphylococcus aureus (gram-positive) bacteria on PA substrate and gauze were evaluated using the disc diffusion method. The results indicated that the prepared nanocomposites offer favorable antibacterial properties and bacteria would not grow in culture media. The water uptake capacity test of the treated samples was assessed and the data demonstrated that the water absorption rate significantly increases on both treated substrates (gauze and PA substrate) due to the presence of alginate polymer. Also, observing the results of the coagulation test showed that treated samples caused blood clots on the dressing. This is due to the presence of alginate polymer. The present work demonstrates that the prepared samples offer excellent antibacterial properties and good water uptake capacity that capable of being a potential candidate for wound dressings. Due to the results, the produced PA substrate could be an appropriate replacement for the cotton gauze as a wound dressing.

Fabrication of Hierarchical Indium Vanadate Materials for Supercapacitor Application

Transition metal orthovanadates are emerging 2D materials for promising electrochemical energy storage applications. Facile hydrothermal method for nanocrystalline indium vanadate (InVO4) semiconducting materials' fabrication is economical because of its direct chemical synthesis. X-ray diffraction studies, field emission scanning electron microscope (SEM) images, transmission electron microscopy (TEM), and photoelectron X-ray spectrum are used to describe the semiconductor materials as synthesized. InVO4 microspheres have attracted a lot of attention in the energy and environmental sector. These microsphere-derived semiconductor materials are recognized to offer the advantages of their large surface area, tunable pore sizes, enhanced light absorption, efficient carrier (electron-hole) separation, superior electronic and optical behavior, and high durability. From the results of SEM and TEM, InVO4 shows a microsphere construction with a mixture of nanosized particles. Diffuse reflectance UV-visible measurements are used to determine the bandgap, and it is found to be 2.1 eV for InVO4. The electrochemical analysis reveals a superior performance of the pseudocapacitor with hydrothermally derived microspheres of InVO4. Alongside an improved pseudocapacity, developed after 4000 cycles, it has excellent cycling stability with a retention of ≈94% of its original specific capacitance efficiency.

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.

The Nano-Intestine Interaction: Understanding the Location-Oriented Effects of Engineered Nanomaterials in the Intestine

Engineered nanomaterials (ENMs) are used in food additives, food packages, and therapeutic purposes owing to their useful properties, Therefore, human beings are orally exposed to exogenous nanomaterials frequently, which means the intestine is one of the primary targets of nanomaterials. Consequently, it is of great importance to understand the interaction between nanomaterials and the intestine. When nanomaterials enter into gut lumen, they inevitably interact with various components and thereby display different effects on the intestine based on their locations; these are known as location-oriented effects (LOE). The intestinal LOE confer a new biological-effect profile for nanomaterials, which is dependent on the involvement of the following biological processes: nano-mucus interaction, nano-intestinal epithelial cells (IECs) interaction, nano-immune interaction, and nano-microbiota interaction. A deep understanding of NM-induced LOE will facilitate the design of safer NMs and the development of more efficient nanomedicine for intestine-related diseases. Herein, recent progress in this field is reviewed in order to better understand the LOE of nanomaterials. The distant effects of nanomaterials coupling with microbiota are also highlighted. Investigation of the interaction of nanomaterials with the intestine will stimulate other new research areas beyond intestinal nanotoxicity.

Antioxidant Enzyme Activity and Lipid Peroxidation in Aporrectodea caliginosa Earthworms Exposed to Silver Nanoparticles and Silver Nitrate in Spiked Soil

Silver nanoparticles (AgNPs) from industrial use, discharged via the land application of sewage sludge, are interacting with soil biota, including earthworms. In affected organisms, excessive production of reactive oxygen species can result in lipid peroxidation, shifting the balance between oxidants and antioxidants to cause oxidative stress. We determined selected lower-tier biomarkers such as antioxidant responses and lipid peroxidation in Aporrectodea caliginosa earthworms exposed to soils spiked with AgNPs or silver nitrate (AgNO₃ ). Aporrectodea caliginosa were exposed to AgNPs at 0 (control), 0.3, 3, 30, and 300 mg/kg or Ag⁺ (as AgNO₃ ) at 0, 0.03, 0.3, 3, and 10 mg/kg in soil for 4 wk. At 1, 2, 3, and 4 wk, the activity of the antioxidant enzymes superoxide dismutase, catalase, glutathione peroxidase, glutathione S-transferase, as well as lipid peroxidation (malondialdehyde content), increased as a function of concentration, with a much larger response for Ag⁺ than AgNPs. Given the likelihood of ever-increasing AgNP concentrations in soil, where AgNPs can transform to ionic Ag (Ag⁺ ), our findings of antioxidant response to oxidative stress in a common indicator organism even at an environmentally realistic exposure concentration of 0.03 mg/kg demonstrate that AgNPs may affect soil fertility and, thus, agricultural production. Evaluating selected lower-tier biomarkers offers a meaningful assessment of AgNPs and Ag⁺ effects on terrestrial earthworms. Environ Toxicol Chem 2020;39:1257-1266. © 2020 SETAC.

Soluble silver ions from silver nanoparticles induce a polarised secretion of interleukin-8 in differentiated Caco-2 cells

Because of their antimicrobial properties, silver nanoparticles are increasingly incorporated in food-related and hygiene products, which thereby could lead to their ingestion. Although their cytotoxicity mediated by oxidative stress has been largely studied, their effects on inflammation remain controversial. Moreover, the involvement of silver ions (originating from Ag0 oxidation) in their mode of action is still unclear. In this context, the present study aims at assessing the impact of silver nanoparticles on the secretion of the pro-inflammatory chemokine interleukin-8 by Caco-2 cells forming an in vitro model of the intestinal mucosal barrier. Silver nanoparticles induced a vectorized secretion of interleukin-8 towards the apical compartment, which is found in the medium 21 h after the incubation. This secretion seems mediated by Nrf2 signalling pathway that orchestrates cellular defense against oxidative stress. The soluble silver fraction of silver nanoparticles suspensions led to a similar amount of secreted interleukin-8 than silver nanoparticles, suggesting an involvement of silver ions in this interleukin-8 secretion.

Recent advances and challenges on applications of nanotechnology in food packaging. A literature review

Nanotechnology applied to food and beverage packaging has created enormous interest in recent years, but in the same time there are many controversial issues surrounding nanotechnology and food. The benefits of engineered nanoparticles (ENPs) in food-contact applications are accompanied by safety concerns due to gaps in understanding of their possible toxicology. In case of incorporation in food contact polymers, the first step to consumer exposure is the transfer of ENPs from the polymer to the food. Hence, to improve understanding of risk and benefit, the key questions are whether nanoparticles can be released from food contact polymers and under which conditions. This review has two main goals. Firstly, it will presents the current advancements in the application of ENPs in food and beverage packaging sector to grant active and intelligent properties. A particular focus will be placed on current demands in terms of risk assessment strategies associated with the use ENPs in food contact materials (FCMs), i.e. up-to-date migration/cytotoxicity studies of ENPs which are partly contradictory. Food matrix effects are often ignored, and may have a pronounced impact on the behaviour of ENPs in the gastrointestinal tract (GIT). A standardized food model (SFM) for evaluating the toxicity and fate of ingested ENPs was recently proposed and herein discussed with the aims to offer an overview to the reader. It is therefore clear that further systematic research is needed, which must account for interactions and transformations of ENMs in foods (food matrix effect) and in the gastrointestinal tract (GIT) that are likely to determine nano-biointeractions. Secondly, the review provides an extensive analysis of present market dynamics on ENPs in food/beverage packaging moving beyond concept to current industrial applications.

Toxicity of combined exposure of ZnO nanoparticles (NPs) and myricetin to Caco-2 cells: changes of NP colloidal aspects, NP internalization and the apoptosis-endoplasmic reticulum stress pathway

Phytochemicals as typical food components may significantly influence the toxicity of nanoparticles (NPs) in intestinal cells, indicating a need to evaluate the toxicological effects of NPs in a complex situation. Previous studies suggested that the anti-oxidative properties of phytochemicals were important to elicit cytoprotective effects against NP exposure. However, we recently found that the changes of signaling pathways may be more important for cytoprotective effects of phytochemicals. In this study, we investigated the influence of myricetin (MY) on the cytotoxicity of ZnO NPs in Caco-2 cells and the possible mechanism. MY at 50 μM showed minimal impact on the solubility and colloidal aspects of ZnO NPs, but protected Caco-2 cells from NP exposure as it increased the EC50 value. For comparison, dihydromyricetin (DMY; chemical analog of MY) increased the EC50 value to a much lesser extent. Exposure to ZnO NPs significantly induced intracellular Zn ions, whereas MY or DMY did not significantly influence the internalization of NPs. However, ZnO NPs significantly promoted the ratio of caspase-3/pro-caspase-3, which was inhibited by the presence of MY. Exposure to ZnO NPs did not significantly promote the biomarkers of endoplasmic reticulum (ER) stress, but co-exposure to ZnO NPs and MY significantly lowered the levels of a panel of ER stress biomarkers. In conclusion, these results suggested that MY could protect Caco-2 cells from ZnO NP exposure, which may not be related to the changes of colloidal stability or internalization of NPs but could be alternatively related to the reduction of ER stress leading to lower cleaved caspase-3.

Influence of 3-Hydroxyflavone on Colloidal Stability and Internationalization of Ag Nanomaterials Into THP-1 Macrophages

Polyphenols as typical food components can influence the colloidal properties and internalization of nanomaterials (NMs) into mammalian cells. Recently, we found that 3-hydroxyflavone (H3) promoted intracellular Zn ions in ZnO nanoparticle (NP) exposed Caco-2 and HepG2 cells. However, it is unclear if H3 could affect the internalization of metal-based NMs with different morphologies. This study investigated the influence of H3 on colloidal aspects of Ag NPs and Ag nanoflakes (NFs) as well as the internalization of Ag NMs into THP-1 macrophages. 3-Hydroxyflavone at 50 μM promoted the solubility and altered hydrodynamic size, polydispersity index, and ζ potential of Ag NPs and Ag NFs, which indicated that H3 could affect the colloidal stability of Ag NMs. Only H3 but not Ag NMs significantly decreased mitochondrial activities of THP-1 macrophages. The internalization of Ag NMs was markedly increased due to the presence of H3. 3-Hydroxyflavone also exhibited antioxidative properties as it reduced intracellular reactive oxygen species and promoted the activities of ABC transporters as it reduced retention of Calcein in Ag NM-exposed THP-1 macrophages. We concluded that H3 promoted the internalization of Ag NMs into macrophages probably by altering the colloidal stability of Ag NMs and consequently NM-macrophage interactions.

Food additives can act as triggering factors in celiac disease: Current knowledge based on a critical review of the literature

Celiac disease (CeD) is an autoimmune disorder, mainly affecting the small intestine, triggered by the ingestion of gluten with the diet in subjects with a specific genetic status. The passage of gluten peptides through the intestinal barrier, the uptake by antigen presenting cells and their presentation to T cells represent essential steps in the pathogenesis of the disease. CeD prevalence varies in different populations, but a tendency to increase has been observed in various studies in recent years. A higher amount of gluten in modern grains could explain this increased frequency, but also food processing could play a role in this phenomenon. In particular, the common use of preservatives such as nanoparticles could intervene in the pathogenesis of CeD, due to their possible effect on the integrity of the intestinal barrier, immune response or microbiota. In fact, these alterations have been reported after exposure to metal nanoparticles, which are commonly used as preservatives or to improve food texture, consistency and color. This review will focus on the interactions between several food additives and the intestine, taking into account data obtained in vitro and in vivo, and analyzing their effect in respect to the development of CeD in genetically predisposed individuals.

Stealth Iron Oxide Nanoparticles for Organotropic Drug Targeting

The ability of peculiar iron oxide nanoparticles (IONPs) to evade the immune system was investigated in vivo. The nanomaterial was provided directly into the farming water of zebrafish ( Danio rerio) and the distribution of IONPs and the delivery of oxytetracycline (OTC) was studied evidencing the successful overcoming of the intestinal barrier and the specific and prolonged (28 days) organotropic delivery of OTC to the fish ovary. Noteworthy, no sign of adverse effects was observed. In fish blood, IONPs were able to specifically bind apolipoprotein A1 (Apo A1) and molecular modeling showed the structural analogy between the IONP@Apo A1 nanoconjugate and high-density lipoprotein (HDL). Thus, the preservation of the biological identity of the protein suggests a plausible explanation of the observed overcoming of the intestinal barrier, of the great biocompatibity of the nanomaterial, and of the prolonged drug delivery (benefiting of the lipoprotein transport route). The present study promises novel and unexpected stealth materials in nanomedicine.

Assessing the relevance of exposure time in differentiated Caco-2/HT29 cocultures. Effects of silver nanoparticles

In vitro models of the intestinal barrier are being increasingly used to evaluate nanoparticles (NPs) exposure risk. Nevertheless, most of these studies have focused on short-term exposures lasting no more than 24 h of duration, which could underestimate the toxic effects of a given compound under a more realistic setting. Since the assessment of longer exposure time-points is crucial to evaluate the risk of cumulative exposure to NPs, we have analyzed the effects of AgNPs at different exposure time-points between 6 h and 4 days on the barrier model system constituted by Caco-2/HT29 cells. Our results indicate that i) the system is stable during this time frame; ii) AgNPs affect the barrier's integrity only at the highest concentration tested (100 μg/mL), and only after 96 h of exposure; iii) cellular uptake of AgNPs showed a time-dependent and concentration-dependent increase; iv) translocation through the barrier was only observed at the highest concentration and only after 96 h of exposure; v) the expression of genes involved in the barrier's structure differs depending on the exposure time analyzed. All these results reinforce our proposal of expanding exposure times beyond 24 h when performing assays for hazard assessment of NPs using in vitro models of the intestinal barrier.

In vitro nanoparticle dosimetry for adherent growing cell monolayers covering bottom and lateral walls

Background

Even though a continuously high number of in vitro studies on nanoparticles are being published, the issue of correct dose matter is often not sufficiently taken into account. Due to their size, the diffusion of nanoparticles is slower, as compared to soluble chemicals, and they sediment slowly. Therefore, the administered dose of particles in in vitro experiments is not necessarily the same (effective) dose that comes into contact with the cellular system. This can lead to misinterpretations of experimental toxic effects and disturbs the meaningfulness of in vitro studies. In silico calculations of the effective nanoparticle dose can help circumventing this problem.

Results

This study addresses more complex in vitro models like the human intestinal cell line Caco-2 or the human liver cell line HepaRG, which need to be differentiated over a few weeks to reach their full complexity. During the differentiation time the cells grow up the wall of the cell culture dishes and therefore a three-dimensional-based in silico model of the nanoparticle dose was developed to calculate the administered dose received by different cell populations at the bottom and the walls of the culture dish. Moreover, the model can perform calculations based on the hydrodynamic diameter which is measured by light scattering methods, or based on the diffusion coefficient measured by nanoparticle tracking analysis (NTA). This 3DSDD (3D-sedimentation-diffusion-dosimetry) model was experimentally verified against existing dosimetry models and was applied to differentiated Caco-2 cells incubated with silver nanoparticles.

Conclusions

The 3DSDD accounts for the 3D distribution of cells in in vitro cell culture dishes and is therefore suitable for differentiated cells. To encourage the use of dosimetry calculating software, our model can be downloaded from the supporting information.

Electronic supplementary material

The online version of this article (10.1186/s12989-018-0278-9) contains supplementary material, which is available to authorized users.

Potential role of α-lipoic acid and Ginkgo biloba against silver nanoparticles-induced neuronal apoptosis and blood-brain barrier impairments in rats

AIMS

This study explored whether silver nanoparticles (AgNPs) can disrupt tight-junctions integrity resulted in blood-brain barrier dysfunction along with oxidative stress, pro-inflammation, and apoptosis induction. Additionally, neuroprotective activities of α-lipoic acid (LA) and Ginkgo biloba (GB) were investigated.

MAIN METHODS

Forty adults rats were enrolled into; Control, AgNPs (50 mg/kg), LA (100 mg/kg) + AgNPs, and GB (120 mg/kg) + AgNPs. After 30 days, neuronal changes were assessed biochemically and histopathologically. Brain tissues oxidative indices, mRNA expression of proinflammatory cytokines and tight-junction proteins and pro-apoptotic biomarker, caspase-3 were investigated.

KEY FINDINGS

AgNPs exposure enhanced lipid peroxidation (+195%) along with declines in glutathione (-43%), glutathione peroxidase (-34%), glutathione S-transferase (-31%), catalase (-43%), and superoxide dismutase (-38%) activities in brain tissues. The apparent brain oxidative damage was associated with obvious neuronal dysfunction that was ascertained by neuropathological lesions. AgNPs lowered serum acetylcholine esterase, iron and copper levels, and increased creatine phosphokinase and creatine phosphokinase-brain type activities. Following AgNPs exposure, brain silver and iron contents were increased, but the copper level was decreased. AgNPs up-regulated TNF-α (6.5-fold) and IL-1β (8.9-fold) transcript levels, and simultaneously over-expressed the caspase-3 protein in cerebrum and cerebellum inducing cell apoptosis. Moreover, AgNPs down-regulated the transcript levels of tight-junction proteins; JP-1 (0.65-fold) and JAM-3(0.81-fold).

SIGNIFICANCE

LA and relatively GB improved the serious effects of AgNPs on the blood-brain barrier function and tight-junction proteins through their antioxidants, anti-inflammatory, and anti-apoptotic efficacies. Co-treatment with LA or GB may be favorable in ameliorating the neurotoxic side effects of AgNPs.

Chemical Structures of Polyphenols That Critically Influence the Toxicity of ZnO Nanoparticles

Recent studies suggested that phytochemicals as natural antioxidants in food could alleviate nanoparticle (NP) toxicity. This study investigated the combined toxicity of ZnO NPs and a panel of polyphenols. Surprisingly, polyphenols with both high and almost no radical scavenging activities could elicit cytoprotective effects against NP exposure in Caco-2 cells, which were primarily influenced by the positions of the hydroxyl group. Polyphenols with different chemical structures variously influenced the hydrodynamic size, zeta potential, and solubility of ZnO NPs as well as NP-induced intracellular superoxide and Zn ions, which could all contribute to the combined effects. Responses of human endothelial cells appeared to be different from the responses of Caco-2 cells, which may indicate cell-type dependent responses to combined exposure of NPs and phytochemicals. In conclusion, the data from this study suggested a pivotal role of chemical structures of phytochemicals in determining their capacity to affect ZnO NP toxicity.

A combination of NMR and liquid chromatography to characterize the protective effects of Rhus tripartita extracts on ethanol-induced toxicity and inflammation on intestinal cells

Consumption of ethanol may have severe effects on human organs and tissues and lead to acute and chronic inflammation of internal organs. The present study aims at investigating the potential protective effects of three different extracts prepared from the leaves, root, and stem of the sumac, Rhus tripartita, against ethanol-induced toxicity and inflammation using intestinal cells as a cell culture system, in vitro model of the intestinal mucosa. The results showed an induction of cytotoxicity by ethanol, which was partially reversed by co-administration of the plant extracts. As part of investigating the cellular response and the mechanism of toxicity, the role of reduced thiols and glutathione-S-transferases were assessed. In addition, intestinal cells were artificially imposed to an inflammation state and the anti-inflammatory effect of the extracts was estimated by determination of interleukin-8. Finally, a detailed characterization of the contents of the three plant extracts by high resolution Nuclear Magnetic Resonance (NMR) spectroscopy and mass spectrometry revealed significant differences in their chemical compositions.

Green synthesis of silver nanoparticles using Artemisia turcomanica leaf extract and the study of anti-cancer effect and apoptosis induction on gastric cancer cell line (AGS)

The current study was aimed (1) to study the green synthesis of silver nanoparticles using Artemisia turcomanica leaf extract, (2) to investigate the induction of apoptosis by biologically synthesized silver nanoparticles in gastric cancer cell line (AGS) and (3) to compare their anti-cancer potential with commercial silver nanoparticles. The specification and morphology of the phytosynthesized AgNPs were evaluated using transmission electron microscopy (TEM), scanning electron microscopy (SEM), UV-visible spectroscopy, X-ray diffraction and Fourier transform infrared spectroscopy (FTIR). The nanoparticles synthesized were of an average size of 22 nm. The cytotoxicity of biological and commercial nanoparticles was investigated in gastric cancer cells (AGS) as well as normal fibroblast cells (L-929) by MTT assay. By increasing the concentration of phytosynthesized and commercial silver nanoparticles, a decrease was observed in the cell viability. Increased apoptosis was observed in the cells treated with biological silver nanoparticles compared to untreated cells (p < .001). Based on these findings, it was inferred that biologically synthesized silver nanoparticles induced apoptosis, and showed a cytotoxic and anti-cancer effect against gastric cancer cell lines in a dose- and time-dependent manner. Biologically synthesized nanoparticles may possess higher anti-cancer properties than commercial silver nanoparticles.

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.

The effects of baicalein or baicalin on the colloidal stability of ZnO nanoparticles (NPs) and toxicity of NPs to Caco-2 cells

Recent study suggested that the presence of phytochemicals in food could interact with nanoparticles (NPs) and consequently reduce the toxicity of NPs, which has been attributed to the antioxidant properties of phytochemicals. In this study, we investigated the interactions between ZnO NPs and two flavonoids baicalein (Ba) or baicalin (Bn) as well as the influence of the interactions on the toxicity of ZnO NPs to Caco-2 cells. The antioxidant properties of Ba and Bn were confirmed by 1,1-diphenyl-2-picrylhydrazyl (DPPH) and 2'-azino-bis(3-ethylbenzothiazoline-6-sulphonic acid) (ABTS) assays, with Ba being stronger. However, the presence of Ba or Bn did not significantly affect cytotoxicity, intracellular superoxide or release of inflammatory cytokines of Caco-2 cells after ZnO NP exposure. When Ba was present, the cellular viability of Caco-2 cells after exposure to ZnO NPs was slightly increased, associated with a modest decrease of intracellular Zn ions, but these effects were not statistically different. Ba was more effective than Bn at changing the hydrodynamic sizes, Zeta potential and UV-Vis spectra of ZnO NPs, which indicated that Ba might increase the colloidal stability of NPs. Taken together, the results of the present study indicated that the anti-oxidative phytochemical Ba might only modestly protected Caco-2 cells from the exposure to ZnO NPs associated with an insignificant reduction of the accumulation of intracellular Zn ions. These results also indicated that when assessing the combined effects of NPs and phytochemicals to cells lining gastrointestinal tract, it might be necessary to evaluate the changes of colloidal stability of NPs altered by phytochemicals.

The presence of oleate stabilized ZnO nanoparticles (NPs) and reduced the toxicity of aged NPs to Caco-2 and HepG2 cells

The presence of food components may alter the colloidal aspects and toxicity of nanoparticles (NPs). In this study, the toxicity of ZnO NPs to Caco-2 and HepG2 cells was assessed, with the emphasis on the interactions between ZnO NPs and oleate (OA). The presence of OA increased UV-Vis spectra and hydrodynamic sizes, decreased Zeta potential, and markedly reduced the release of Zn ions from the dissolution of ZnO NPs, which combined indicated that OA could coat ZnO NPs and stabilize ZnO NPs. Exposure to ZnO NPs significantly induced cytotoxicity to Caco-2 and HepG2 cells, associated with increased intracellular Zn ions but not superoxide. When OA was added to the freshly prepared ZnO NP suspensions, the cytotoxicity, intracellular Zn ions and superoxide induced by ZnO NPs were not significantly affected. However, when ZnO NPs were aged for 24 h with the presence of OA, the cytotoxicity of ZnO NPs to Caco-2 and HepG2 cells was significantly reduced, associated with a reduction of intracellular Zn ions. The results from this study suggested that the presence of OA could increase colloidal stability of ZnO NPs and consequently reduce the toxicity of ZnO NPs after aging associated with reduced accumulation of intracellular Zn ions.

Biological evaluation of silver nanoparticles incorporated into chitosan-based membranes

AIM

To evaluate the antibacterial potential and biological performance of silver nanoparticles in chitosan-based membranes.

MATERIALS & METHODS

Electrospun chitosan/poly(ethylene oxide) membranes with different amounts of silver nanoparticles were evaluated for antibacterial properties and cytotoxicity in vitro and for tissue response in a rabbit subcutaneous model.

RESULTS

The nanoparticles displayed dose-dependent antibacterial properties against Porphyromonas gingivalis and Fusobacterium nucleatum, without showing noticeable cytotoxicity. The membranes with silver nanoparticles evoked a similar inflammatory response compared with the membranes without silver nanoparticles.

CONCLUSION

The antibacterial effect, combined with the findings on cyto- and biocompatibility warrants further investigation to the usefulness of chitosan/poly(ethylene oxide) membranes with silver nanoparticles, for clinical applications like guided tissue regeneration.

Potential adverse effects of engineered nanomaterials commonly used in food on the miRNome

The emergence of nanotechnology has greatly impacted our daily lives. Multiple products, including cosmetics, pharmaceuticals, electronics and food, are produced with incorporation of nanomaterials (NMs). Nanotechnology has yielded many promising benefits, yet, there remains much uncertainty about the hazards of NMs to humans. Hence, it is important to ensure safety of the users. Although many in vitro and in vivo studies have been carried out on the potential toxicity generated by NMs in food, its effects on the microRNA genome (miRNome) involved in the regulation of gene expression have been poorly understood. Therefore, this review focuses on the types of commonly used NMs (containing silicon dioxide, titanium dioxide, silver or zinc oxide) in food products and their potential toxic effects, including how NMs can induce epigenetic toxicity mediated via altered miRNA expression.

The Interactions between ZnO Nanoparticles (NPs) and α-Linolenic Acid (LNA) Complexed to BSA Did Not Influence the Toxicity of ZnO NPs on HepG2 Cells

Background: Nanoparticles (NPs) entering the biological environment could interact with biomolecules, but little is known about the interaction between unsaturated fatty acids (UFA) and NPs. Methods: This study used α-linolenic acid (LNA) complexed to bovine serum albumin (BSA) for UFA and HepG2 cells for hepatocytes. The interactions between BSA or LNA and ZnO NPs were studied. Results: The presence of BSA or LNA affected the hydrodynamic size, zeta potential, UV-Vis, fluorescence, and synchronous fluorescence spectra of ZnO NPs, which indicated an interaction between BSA or LNA and NPs. Exposure to ZnO NPs with the presence of BSA significantly induced the damage to mitochondria and lysosomes in HepG2 cells, associated with an increase of intracellular Zn ions, but not intracellular superoxide. Paradoxically, the release of inflammatory cytokine interleukin-6 (IL-6) was decreased, which indicated the anti-inflammatory effects of ZnO NPs when BSA was present. The presence of LNA did not significantly affect all of these endpoints in HepG2 cells exposed to ZnO NPs and BSA. Conclusions: the results from the present study indicated that BSA-complexed LNA might modestly interact with ZnO NPs, but did not significantly affect ZnO NPs and BSA-induced biological effects in HepG2 cells.

Cytotoxic effects of nanosilver are highly dependent on the chloride concentration and the presence of organic compounds in the cell culture media

BACKGROUND

Nanosilver shows great promise for use in industrial, consumer or medical products because of its antimicrobial properties. However, the underlying mechanisms of the effects of silver nanoparticles on human cells are still controversial. Therefore, in the present study the influence of the chloride concentration and different serum content of culture media on the cytotoxic effects of nanosilver was systematically evaluated.

RESULTS

Our results show that nanosilver toxicity was strongly affected by the composition of the culture media. The chloride concentration, as well as the carbon content affected the silver agglomeration and the complex formation. But also the dissolution of nanosilver and the availability of free silver ions (Ag+) were severely affected by the compositions of the culture media. Cells, only exposed to silver particles in suspension and dissolved silver complexes, did not show any effects under all conditions. Nanosilver agglomerates and silver complexes were not very soluble. Thus, cells growing on the bottom of the culture dishes were exposed to sedimented nanosilver agglomerates and precipitated silver complexes. Locally, the concentration of silver on the cell surface was very high, much higher compared the silver concentration in the bulk solution. The cytotoxic effects of nanosilver are therefore a combination of precipitated silver complexes and organic silver compounds rather than free silver ions.

CONCLUSIONS

Silver coatings are used in health care products due to their bacteriostatic or antibacterial properties. The assessment of the toxicity of a certain compound is mostly done using in vitro assays. Therefore, cytotoxicity studies of nanosilver using human cell cultures have to be undertaken under well controlled and understood cultivations conditions in order to improve the compatibility of different studies. Especially when eukaryotic versus prokaryotic systems are compared for the evaluation of the use of nanosilver as antibacterial coatings for implants in order to prevent bacterial colonization.

Combined effects of low levels of palmitate on toxicity of ZnO nanoparticles to THP-1 macrophages

We have recently proposed that the interaction between food components and nanoparticles (NPs) should be considered when evaluating the toxicity of NPs. In the present study, we used THP-1 differentiated macrophages as a model for immune cells and investigated the combined toxicity of low levels of palmitate (PA; 10 or 50μM) and ZnO NPs. The results showed that PA especially at 50μM changed the size, Zeta potential and UV-vis spectra of ZnO NPs, indicating a possible coating effect. Up to 32μg/mL ZnO NPs did not significantly affect mitochondrial activity, intracellular reactive oxygen species (ROS) or release of interleukin 6 (IL-6), but significantly impaired lysosomal function as assessed by neutral red uptake assay and acridine orange staining. The presence of 50μM PA, but not 10μM PA, further promoted the toxic effects of ZnO NPs to lysosomes but did not significantly affect other endpoints. In addition, ZnO NPs dose-dependently increased intracellular Zn ions in THP-1 macrophages, which was not significantly affected by PA. Taken together, the results of the present study showed a combined toxicity of low levels of PA and ZnO NPs especially to lysosomes in THP-1 macrophages.

Different responses of Caco-2 and MCF-7 cells to silver nanoparticles are based on highly similar mechanisms of action

The mode of action of silver nanoparticles (AgNPs) is suggested to be exerted through both Ag⁺ and AgNP dependent mechanisms. Ingestion is one of the major NP exposure routes, and potential effects are often studied using Caco-2 cells, a well-established model for the gut epithelium. MCF-7 cells are epithelial breast cancer cells with extensive well-characterized toxicogenomics profiles. In the present study, we aimed to gain a deeper understanding of the cellular molecular responses in Caco-2 and MCF-7 cells after AgNP exposure in order to evaluate whether epithelial cells derived from different tissues demonstrated similar responses. These insights could possibly reduce the size of cell panels for NP hazard identification screening purposes. AgNPs of 20, 30, 60, and 110 nm, and AgNO₃ were exposed for 6 h and 24 h. AgNPs were shown to be taken up and dissolve intracellularly. Compared with MCF-7 cells, Caco-2 cells showed a higher sensitivity to AgNPs, slower gene expression kinetics and absence of NP size-dependent responses. However, on a molecular level, no significant differences were observed between the two cell types. Transcriptomic analysis showed that Ag(NP) exposure caused (oxidative) stress responses, possibly leading to cell death in both cell lines. There was no indication for effects specifically induced by AgNPs. Responses to AgNPs appeared to be induced by silver ions released from the AgNPs. In conclusion, differences in mRNA responses to AgNPs between Caco-2 and MCF-7 cells were mainly related to timing and magnitude, but not to a different underlying mechanism.

Consideration of interaction between nanoparticles and food components for the safety assessment of nanoparticles following oral exposure: A review

Nanoparticles (NPs) are increasingly used in food, and the toxicity of NPs following oral exposure should be carefully assessed to ensure the safety. Indeed, a number of studies have shown that oral exposure to NPs, especially solid NPs, may induce toxicological responses both in vivo and in vitro. However, most of the toxicological studies only used NPs for oral exposure, and the potential interaction between NPs and food components in real life was ignored. In this review, we summarized the relevant studies and suggested that the interaction between NPs and food components may exist by that 1) NPs directly affect nutrients absorption through disruption of microvilli or alteration in expression of nutrient transporter genes; 2) food components directly affect NP absorption through physico-chemical modification; 3) the presence of food components affect oxidative stress induced by NPs. All of these interactions may eventually enhance or reduce the toxicological responses induced by NPs following oral exposure. Studies only using NPs for oral exposure may therefore lead to misinterpretation and underestimation/overestimation of toxicity of NPs, and it is necessary to assess the synergistic effects of NPs in a complex system when considering the safety of NPs used in food.

Mucin-mediated nanocarrier disassembly for triggered uptake of oligonucleotides as a delivery strategy for the potential treatment of mucosal tumours

This work demonstrates gastric mucin-triggered nanocarrier disassembly for release of antisense oligonucleotides and consequent unassisted cellular entry as a novel oral delivery strategy. A fluorescence activation-based reporter system was used to investigate the interaction and mucin-mediated disassembly of chitosan-based nanocarriers containing a 13-mer DNA oligonucleotide with a flanked locked RNA nucleic acid gapmer design. Gastric mucins were shown to trigger gapmer release from nanocarriers that was dependent on the interaction time, mucin concentration and N : P ratio with a maximal release at N : P 10. In contrast to siRNA, naked gapmers exhibited uptake into mucus producing HT-MTX mono-cultures and HT-MTX co-cultured with the carcinoma epithelial cell line Caco-2. Importantly, in vivo gapmer uptake was observed in epithelial tissue 30 min post-injection in murine intestinal loops. The findings present a mucosal design-based system tailored for local delivery of oligonucleotides that may maximize the effectiveness of gene silencing therapeutics within tumours at mucosal sites.

Toxicological Effects of Caco-2 Cells Following Short-Term and Long-Term Exposure to Ag Nanoparticles

Extensive utilization increases the exposure of humans to Ag nanoparticles (NPs) via the oral pathway. To comprehensively address the action of Ag NPs to the gastrointestinal systems in real situations, i.e., the long-term low-dose exposure, we evaluated and compared the toxicity of three Ag NPs (20–30 nm with different surface coatings) to the human intestine cell Caco-2 after 1-day and 21-day exposures, using various biological assays. In both the short- and long-term exposures, the variety of surface coating predominated the toxicity of Ag NPs in a descending order of citrate-coated Ag NP (Ag-CIT), bare Ag NP (Ag-B), and poly (N-vinyl-2-pyrrolidone)-coated Ag NP (Ag-PVP). The short-term exposure induced cell growth inhibition and death. The cell viability loss appeared after cells were exposed to 0.7 μg/mL Ag-CIT, 0.9 μg/mL Ag-B or >1.0 μg/mL Ag-PVP for 24 h. The short-term and higher-dose exposure also induced reactive oxygen species (ROS) generation, mitochondrial damage, cell membrane leakage, apoptosis, and inflammation (IL-8 level). The long-term exposure only inhibited the cell proliferation. After 21-day exposure to 0.4 μg/mL Ag-CIT, the cell viability dropped to less than 50%, while cells exposed to 0.5 μg/mL Ag-PVP remained normal as the control. Generally, 0.3 μg/mL is the non-toxic dose for the long-term exposure of Caco-2 cells to Ag NPs in this study. However, cells presented inflammation after exposure to Ag NPs with the non-toxic dose in the long-term exposure.

Tuning the inflammatory response to silver nanoparticles via quercetin in Caco-2 (co-)cultures as model of the human intestinal mucosa

Interaction of nanoparticles with food matrix components may cause unpredictable health complications. Using an improved Caco-2 cell-based in vitro (co-)culture model the potential of quercetin as one of the major food flavonoids to alter the effect of silver nanoparticles (Ag-NPs) <20 nm in the human intestinal mucosa at real life concentrations was investigated. Ag-NPs (15-90 μg/ml) decreased cell viability and reduced thiol groups, induced oxidative/nitrosative stress and lipid peroxidation and led to activity changes of various antioxidant enzymes after 3h exposure. The contribution of Ag(+) ions within the concentrations released from nanoparticles was shown to be less important, compared to Ag-NPs. While leading to inflammatory response in the intestines, Ag-NPs, paradoxically, also showed a potential anti-infammatory effect manifested in down-regulated IL-8 levels. Quercetin, co-administered with Ag-NPs, led to a reduction of cytotoxicity, oxidative stress, and recovered metabolic activity of Caco-2 cells, suggesting the protective effects of this flavonoid against the harmful effect of Ag-NPs. Quercetin not only alleviated the effect of Ag-NPs on the gastrointestinal cells, but also demonstrated a potential to serve as a tool for reversible modulation of intestinal permeability.

Cytotoxicity of Nanoparticles Contained in Food on Intestinal Cells and the Gut Microbiota

Toxicity of nanoparticles (NPs) upon oral exposure has been studied in animals using physiological changes, behavior, histology, and blood analysis for evaluation. The effects recorded include the combination of the action on cells of the exposed animal and the reaction of the microorganisms that populate the external and internal surfaces of the body. The importance of these microorganisms, collectively termed as microbiota, for the health of the host has been widely recognized. They may also influence toxicity of NPs but these effects are difficult to differentiate from toxicity on cells of the gastrointestinal tract. To estimate the likelihood of preferential damage of the microbiota by NPs the relative sensitivity of enterocytes and bacteria was compared. For this comparison NPs with antimicrobial action present in consumer products were chosen. The comparison of cytotoxicity with Escherichia coli as representative for intestinal bacteria and on gastrointestinal cells revealed that silver NPs damaged bacteria at lower concentrations than enterocytes, while the opposite was true for zinc oxide NPs. These results indicate that silver NPs may cause adverse effects by selectively affecting the gut microbiota. Fecal transplantation from NP-exposed animals to unexposed ones offers the possibility to verify this hypothesis.

Surface modification of InVO4 nanoparticles on WO3 plate array films for improved photoelectrochemical performance

Surface modification of InVO₄ nanoparticles on WO₃ plates array films using a dipping–annealing method.