Interactions of graphene oxide and graphene nanoplatelets with the in vitro Caco-2/HT29 model of intestinal barrier

Comparative toxicological analysis of two pristine carbon nanomaterials (graphene oxide and aminated graphene oxide) and their corresponding degraded forms using human in vitro models

Despite the wide application of graphene-based materials, the information of the toxicity associated to some specific derivatives such as aminated graphene oxide is scarce. Likewise, most of these studies analyse the pristine materials, while the available data regarding the harmful effects of degraded forms is very limited. In this work, the toxicity of graphene oxide (GO), aminated graphene oxide (GO-NH2), and their respective degraded forms (dGO and dGO-NH2) obtained after being submitted to high-intensity sonication was evaluated applying in vitro assays in different models of human exposure. Viability and ROS assays were performed on A549 and HT29 cells, while their skin irritation potential was tested on a reconstructed human epidermis model. The obtained results showed that GO-NH2 and dGO-NH2 substantially decrease cell viability in the lung and gastrointestinal models, being this reduction slightly higher in the cells exposed to the degraded forms. In contrast, this parameter was not affected by GO and dGO which, conversely, showed the ability to induce higher levels of ROS than the pristine and degraded aminated forms. Furthermore, none of the materials is skin irritant. Altogether, these results provide new insights about the potential harmful effects of the selected graphene-based nanomaterials in comparison with their degraded counterparts.

Harmful effects of true-to-life nanoplastics derived from PET water bottles in human alveolar macrophages

The increasing presence of secondary micro/nanoplastics (MNPLs) in the environment requires knowing if they represent a real health concern. To such end, an important point is to test representative MNPLs such as the denominated true-to-life MNPLs, resulting from the degradation of plastic goods in lab conditions. In this study, we have used polyethylene terephthalate (PET) NPLs resulting from the degradation of PET water bottles. Since inhalation is an important exposure route to environmental MNPLS, we have used mouse alveolar macrophages (MH-S) as a target cell, and the study focused only on the cells that have internalized them. This type of approach is novel as it may capture the realistic adverse effects of PETNPLs only in the internalized cells, thereby mitigating any biases while assessing the risk of these MNPLs. Furthermore, the study utilized a set of biomarkers including intracellular reactive oxygen species (ROS) levels, variations on the mitochondrial membrane potential values, and the macrophage polarization to M1 (pro-inflammatory response) and M2 (anti-proinflammatory response) as possible cellular effects due to PETNPLs in only the cells that internalized PETNPLs. After exposures lasting for 3 and 24 h to a range of concentrations (0, 25, 50, and 100 μg/mL) the results indicate that no toxicity was induced despite the 100% internalization observed at the highest concentration. Significant intracellular levels of ROS were observed, mainly at exposures lasting for 24 h, in an indirect concentration-effect relationship. Interestingly, a reduction in the mitochondrial membrane potential was observed, but only at exposures lasting for 24 h, but without a clear concentration-effect relationship. Finally, PETNPL exposure shows a significant polarization from M0 to M1 and M2 subtypes. Polarization to M1 (pro-inflammatory stage) was more marked and occurred at both exposure times. Polarization to M2 (anti-inflammatory stage) was only observed after exposures lasting for 24 h. Due to the relevance of the described biomarkers, our results underscore the need for further research, to better understand the health implications associated with MNPL exposure.

Environmental and Health Impacts of Graphene and Other Two-Dimensional Materials: A Graphene Flagship Perspective

Two-dimensional (2D) materials have attracted tremendous interest ever since the isolation of atomically thin sheets of graphene in 2004 due to the specific and versatile properties of these materials. However, the increasing production and use of 2D materials necessitate a thorough evaluation of the potential impact on human health and the environment. Furthermore, harmonized test protocols are needed with which to assess the safety of 2D materials. The Graphene Flagship project (2013-2023), funded by the European Commission, addressed the identification of the possible hazard of graphene-based materials as well as emerging 2D materials including transition metal dichalcogenides, hexagonal boron nitride, and others. Additionally, so-called green chemistry approaches were explored to achieve the goal of a safe and sustainable production and use of this fascinating family of nanomaterials. The present review provides a compact survey of the findings and the lessons learned in the Graphene Flagship.

Hyaluronic acid-functionalized graphene-based nanohybrids for targeted breast cancer chemo-photothermal therapy

Nanomaterials' application in cancer therapy has been driven by their ability to encapsulate chemotherapeutic drugs as well as to reach the tumor site. Nevertheless, nanomedicines' translation has been limited due to their lack of specificity towards cancer cells. Although the nanomaterials' surface can be coated with targeting ligands, such has been mostly achieved through non-covalent functionalization strategies that are prone to premature detachment. Notwithstanding, cancer cells often establish resistance mechanisms that impair the effect of the loaded drugs. This bottleneck may be addressed by using near-infrared (NIR)-light responsive nanomaterials. The NIR-light triggered hyperthermic effect generated by these nanomaterials can cause irreversible damage to cancer cells or sensitize them to chemotherapeutics' action. Herein, a novel covalently functionalized targeted NIR-absorbing nanomaterial for cancer chemo-photothermal therapy was developed. For such, dopamine-reduced graphene oxide nanomaterials were covalently bonded with hyaluronic acid, and then loaded with doxorubicin (DOX/HA-DOPA-rGO). The produced nanomaterials showed suitable physicochemical properties, high encapsulation efficiency, and photothermal capacity. The in vitro studies revealed that the nanomaterials are cytocompatible and that display an improved uptake by the CD44-overexpressing breast cancer cells. Importantly, the combination of DOX/HA-DOPA-rGO with NIR light reduced breast cancer cells' viability to just 23 %, showcasing their potential chemo-photothermal therapy.

Silver Nanoparticles and Graphene Oxide Complex as an Anti-Inflammatory Biocompatible Liquid Nano-Dressing for Skin Infected with Staphylococcus aureus

Background

Bacterial skin infections, including Staphylococcus aureus, are a powerful and still not fully resolved problem. The aim of this research was to determine the possibility of using a complex of graphene oxide (GO) encrusted with silver nanoparticles as an effective antibacterial agent against S. aureus and to assess its pro-inflammatory properties.

Methods

The tests were carried out in vitro on EpiDerm™ Skin, an artificial skin model (MatTek in vitro Life Science Laboratories, Slovak Republic), and the fibroblast cell line (HFF-2 from ATCC, USA). Both models were infected with S. aureus bacteria (ATCC 25923) and then treated with antibiotics or our experimental factors: silver nanoparticles (AgNPs, Nano-koloid, Poland), graphene oxide (GO, NanoPoz, Poland), and complex AgNP-GO (hydrocolloid created by self-assembly).

Results

The antibacterial effectiveness of the AgNP-GO complex was equivalent to that of the antibiotic. In addition, an increase in the level of pro-inflammatory cytokines was observed under the influence of antibiotic administration, in contrast to the effect of AgNP-GO, which showed very limited pro-inflammatory activity.

Conclusion

Hydrocolloid of the AgNP-GO complex, administered in the form of a liquid dressing, may act as an antibacterial agent and also reduce inflammation induced by S. aureus infection.

Use of sodium alginate coatings to improve bioavailability of liposomes containing DPP-IV inhibitory collagen peptides

Sodium alginate (SA) was used to coat liposomes containing DPP-IV inhibitory collagen peptides to improve their stability and in vitro absorption for intra-oral delivery. The liposome structure as well as entrapment efficiency and DPP-IV inhibitory activity was characterized. The liposome stability was determined by measuring in vitro release rates and their gastrointestinal stability. Transcellular permeability of liposomes was further tested to characterize their permeability in small intestinal epithelial cells. The results showed that the 0.3% SA coating increased the diameter (166.7 nm to 249.9 nm), absolute value of zeta potential (30.2 mV to 40.1 mV) and entrapment efficiency (61.52% to 70.99%) of liposomes. The SA-coated liposomes containing collagen peptides showed enhanced storage stability within one month, gastrointestinal stability increased by 50% in bioavailability, transcellular permeability increased by 18% in transmission percentage, and in vitro release rates reduced by 34%, compared to uncoated liposomes. SA coating liposomes are promising carriers for transporting hydrophilic molecules, may be beneficial for improving nutrient absorption and can protect bioactive compounds from being inactivated in the gastrointestinal tract.

Human and environmental impacts of nanoparticles: a scoping review of the current literature

Use of nanoparticles have established benefits in a wide range of applications, however, the effects of exposure to nanoparticles on health and the environmental risks associated with the production and use of nanoparticles are less well-established. The present study addresses this gap in knowledge by examining, through a scoping review of the current literature, the effects of nanoparticles on human health and the environment. We searched relevant databases including Medline, Web of Science, ScienceDirect, Scopus, CINAHL, Embase, and SAGE journals, as well as Google, Google Scholar, and grey literature from June 2021 to July 2021. After removing duplicate articles, the title and abstracts of 1495 articles were first screened followed by the full-texts of 249 studies, and this resulted in the inclusion of 117 studies in the presented review.In this contribution we conclude that while nanoparticles offer distinct benefits in a range of applications, they pose significant threats to humans and the environment. Using several biological models and biomarkers, the included studies revealed the toxic effects of nanoparticles (mainly zinc oxide, silicon dioxide, titanium dioxide, silver, and carbon nanotubes) to include cell death, production of oxidative stress, DNA damage, apoptosis, and induction of inflammatory responses. Most of the included studies (65.81%) investigated inorganic-based nanoparticles. In terms of biomarkers, most studies (76.9%) used immortalised cell lines, whiles 18.8% used primary cells as the biomarker for assessing human health effect of nanoparticles. Biomarkers that were used for assessing environmental impact of nanoparticles included soil samples and soybean seeds, zebrafish larvae, fish, and Daphnia magna neonates.From the studies included in this work the United States recorded the highest number of publications (n = 30, 25.64%), followed by China, India, and Saudi Arabia recording the same number of publications (n = 8 each), with 95.75% of the studies published from the year 2009. The majority of the included studies (93.16%) assessed impact of nanoparticles on human health, and 95.7% used experimental study design. This shows a clear gap exists in examining the impact of nanoparticles on the environment.

Effects of microplastic and engineered nanomaterials on inflammatory bowel disease: A review

Many microplastics and engineered nanomaterials (ENMs) exist in the daily environment. The intestinal impact of these exogenous fine particles on inflammatory bowel disease (IBD) people may be unpredictable. In this paper, we reviewed the recent progress in the effect of microplastics and ENMs on IBD individuals. We also compared and summarized the various roles of microplastics and ENMs in healthy and IBD bodies, including factors such as particle size, particle properties, intestinal microenvironment, interaction with the intestinal barrier, and molecular mechanism. Our literature review showed that microplastics could be accomplices in the development of IBD and could cause severe intestinal inflammation. Moreover, ENMs could elicit diverse exposure outcomes in healthy and IBD bodies. Silicon dioxide nanoparticles (SiO₂ NPs), titanium dioxide nanoparticles (TiO₂ NPs), and graphene oxide (GO) displayed slight to adverse effects that turned into apparent adverse effects, while zinc oxide nanoparticles (ZnO NPs) and silver nanoparticles (Ag NPs) showed a toxic effect that became therapeutic. A deeper understanding of the impact of microplastics and ENMs on the high-risk group was needed, and we proposed several insights into the research priorities and directions.

Impact of physico-chemical properties on the toxicological potential of reduced graphene oxide in human bronchial epithelial cells

The increasing use of graphene-based materials (GBM) requires their safety evaluation, especially in occupational settings. The same physico-chemical (PC) properties that confer GBM extraordinary functionalities may affect the potential toxic response. Most toxicity assessments mainly focus on graphene oxide and rarely investigate GBMs varying only by one property. As a novelty, the present study assessed the in vitro cytotoxicity and genotoxicity of six reduced graphene oxides (rGOs) with different PC properties in the human bronchial epithelial 16HBE14o - cell line. Of the six materials, rGO1-rGO4 only differed in the carbon-to-oxygen (C/O) content, whereas rGO5 and rGO6 were characterized by different lateral size and number of layers, respectively, but similar C/O content compared with rGO1. The materials were characterized by transmission electron microscopy, X-ray photoelectron spectroscopy, laser diffraction and dynamic light scattering, and Brunauer-Emmett-Teller analysis. Cytotoxicity (Luminescent Cell Viability and WST-8 assays), the induction of reactive oxygen species (ROS; 2',7'-dichlorofluorescin diacetate-based assay), the production of cytokines (enzyme-linked immunosorbent assays) and genotoxicity (comet and micronucleus assays) were evaluated. Furthermore, the internalization of the materials in the cells was confirmed by laser confocal microscopy. No relationships were found between the C/O ratio or the lateral size and any of the rGO-induced biological effects. However, rGO of higher oxygen content showed higher cytotoxic and early ROS-inducing potential, whereas genotoxic effects were observed with the rGO of the lowest density of oxygen groups. On the other hand, a higher number of layers seems to be associated with a decreased potential for inducing cytotoxicity and ROS production.

Measuring DNA modifications with the comet assay: a compendium of protocols

The comet assay is a versatile method to detect nuclear DNA damage in individual eukaryotic cells, from yeast to human. The types of damage detected encompass DNA strand breaks and alkali-labile sites (e.g., apurinic/apyrimidinic sites), alkylated and oxidized nucleobases, DNA-DNA crosslinks, UV-induced cyclobutane pyrimidine dimers and some chemically induced DNA adducts. Depending on the specimen type, there are important modifications to the comet assay protocol to avoid the formation of additional DNA damage during the processing of samples and to ensure sufficient sensitivity to detect differences in damage levels between sample groups. Various applications of the comet assay have been validated by research groups in academia, industry and regulatory agencies, and its strengths are highlighted by the adoption of the comet assay as an in vivo test for genotoxicity in animal organs by the Organisation for Economic Co-operation and Development. The present document includes a series of consensus protocols that describe the application of the comet assay to a wide variety of cell types, species and types of DNA damage, thereby demonstrating its versatility.

Genotoxicity evaluation of graphene derivatives by a battery of in vitro assays

The interest of graphene materials has increased markedly in the recent years for their promising applications in many fields as food packing. These new applications have caused some concern regarding their safety for consumers since the intake of these materials may increase. In this sense, a battery of in vitro test is required before its use as a food contact material. Then, the aim of this study was to assess the potential mutagenicity and genotoxicity of graphene oxide (GO) and reduced-graphene oxide (rGO) following the recommendations of the European Food Safety Authority (EFSA). Thus, the mouse lymphoma assay (MLA) and the micronucleus test (MN) were performed in L5178YTk ± cells, and the Caco-2 cells were used for the standard and modified comet assays. The results indicated that GO (0-250 μg/mL) was not mutagenic in the MLA. However, rGO revealed mutagenic activity from 250 μg/mL and 125 μg/mL after 4h and 24h of exposure, respectively. In the MN test, negative results were obtained for both compounds at the concentrations assayed (0-250 μg/mL) for GO/rGO. Moreover, no DNA strand breaks, or oxidative DNA damage were detected in Caco-2 cells exposed to GO (0-250 μg/mL) and rGO (0-176.3 μg/mL for 24h and 0-166.5 μg/mL for 48h). Considering the mutagenic potential of rGO observed further investigation is needed to describe its toxic profile.

The impact of co-treatment with graphene oxide and metal mixture on Salmo trutta at early development stages: The sorption capacity and potential toxicity

Graphene oxide (GO) are novel nanomaterials with a wide range of applications due to their high absorption capacity. This study was undertaken with a view to assess the bioaccumulation and acute toxicity of GO used in combination with the heavy metal mixture (Cr, Cu, Ni and Zn) to fish embryos and larvae. For this purpose, Salmo trutta embryos and larvae were subjected to the 4-day long treatment with three different concentrations of GO, the metal mixture, which was prepared of four metals at the concentrations corresponding to the maximum-permissible-concentrations for EU inland waters (Cr-0.01, Cu-0.01, Ni-0.034, and Zn-0.1 mg/L), and with GO in combination with MIX (GO+MIX). When used in combination with the metal mixture, GO exhibited a high metal sorption capacity. The obtained confocal fluorescence microscopy results showed that GO located in the embryo chorion causing its damage; in larvae, however, GO were found only in the gill region. Results of these experiments confirmed the hypothesis that GO affects the accumulation of metals and mitigates their toxic effects on organism. In embryos, the acute toxicity of exposure to GO and co-exposure to MIX+GO was found to manifest itself through the decreased heart rate (HR) and malondialdehyde (MDA) level and through the increased metallothionein (MT) concentration. Meanwhile, in larvae, GO and MIX+GO were found to induce genotoxicity effects. However, changes in HR, MDA, MT, gill ventilation frequency, yolk sack absorption and cytotoxicity compared with those of the control group were not recorded in larvae. The obtained results confirmed our hypothesis: the combined effect of MIX and GO was less toxic to larvae (especially survival) than individual effects of MIX components. However, our results emphasize that fish exposure to GO alone and in combination with heavy metal contaminants (MIX+GO) even at environmentally relevant concentrations causes health risks that cannot be ignored.

Hazard Assessment of the Effects of Acute and Chronic Exposure to Permethrin, Copper Hydroxide, Acephate, and Validamycin Nanopesticides on the Physiology of Drosophila: Novel Insights into the Cellular Internalization and Biological Effects

New insights into the interactions between nanopesticides and edible plants are required in order to elucidate their impacts on human health and agriculture. Nanopesticides include formulations consisting of organic/inorganic nanoparticles. Drosophila melanogaster has become a powerful model in genetic research thanks to its genetic similarity to mammals. This project mainly aimed to generate new evidence for the toxic/genotoxic properties of different nanopesticides (a nanoemulsion (permethrin nanopesticides, 20 ± 5 nm), an inorganic nanoparticle as an active ingredient (copper(II) hydroxide [Cu(OH)₂] nanopesticides, 15 ± 6 nm), a polymer-based nanopesticide (acephate nanopesticides, 55 ± 25 nm), and an inorganic nanoparticle associated with an organic active ingredient (validamycin nanopesticides, 1177 ± 220 nm)) and their microparticulate forms (i.e., permethrin, copper(II) sulfate pentahydrate (CuSO₄·5H₂O), acephate, and validamycin) widely used against agricultural pests, while also showing the merits of using Drosophila—a non-target in vivo eukaryotic model organism—in nanogenotoxicology studies. Significant biological effects were noted at the highest doses of permethrin (0.06 and 0.1 mM), permethrin nanopesticides (1 and 2.5 mM), CuSO₄·5H₂O (1 and 5 mM), acephate and acephate nanopesticides (1 and 5 mM, respectively), and validamycin and validamycin nanopesticides (1 and 2.5 mM, respectively). The results demonstrating the toxic/genotoxic potential of these nanopesticides through their impact on cellular internalization and gene expression represent significant contributions to future nanogenotoxicology studies.

Immunotoxicity of Carbon-Based Nanomaterials, Starring Phagocytes

In the field of science, technology and medicine, carbon-based nanomaterials and nanoparticles (CNMs) are becoming attractive nanomaterials that are increasingly used. However, it is important to acknowledge the risk of nanotoxicity that comes with the widespread use of CNMs. CNMs can enter the body via inhalation, ingestion, intravenously or by any other route, spread through the bloodstream and penetrate tissues where (in both compartments) they interact with components of the immune system. Like invading pathogens, CNMs can be recognized by large numbers of receptors that are present on the surface of innate immune cells, notably monocytes and macrophages. Depending on the physicochemical properties of CNMs, i.e., shape, size, or adsorbed contamination, phagocytes try to engulf and process CNMs, which might induce pro/anti-inflammatory response or lead to modulation and disruption of basic immune activity. This review focuses on existing data on the immunotoxic potential of CNMs, particularly in professional phagocytes, as they play a central role in processing and eliminating foreign particles. The results of immunotoxic studies are also described in the context of the entry routes, impacts of contamination and means of possible elimination. Mechanisms of proinflammatory effect depending on endocytosis and intracellular distribution of CNMs are highlighted as well.

Hazard assessment of abraded thermoplastic composites reinforced with reduced graphene oxide

Graphene-related materials (GRMs) are subject to intensive investigations and considerable progress has been made in recent years in terms of safety assessment. However, limited information is available concerning the hazard potential of GRM-containing products such as graphene-reinforced composites. In the present study, we conducted a comprehensive investigation of the potential biological effects of particles released through an abrasion process from reduced graphene oxide (rGO)-reinforced composites of polyamide 6 (PA6), a widely used engineered thermoplastic polymer, in comparison to as-produced rGO. First, a panel of well-established in vitro models, representative of the immune system and possible target organs such as the lungs, the gut, and the skin, was applied. Limited responses to PA6-rGO exposure were found in the different in vitro models. Only as-produced rGO induced substantial adverse effects, in particular in macrophages. Since inhalation of airborne materials is a key occupational concern, we then sought to test whether the in vitro responses noted for these materials would translate into adverse effects in vivo. To this end, the response at 1, 7 and 28 days after a single pulmonary exposure was evaluated in mice. In agreement with the in vitro data, PA6-rGO induced a modest and transient pulmonary inflammation, resolved by day 28. In contrast, rGO induced a longer-lasting, albeit moderate inflammation that did not lead to tissue remodeling within 28 days. Taken together, the present study suggests a negligible impact on human health under acute exposure conditions of GRM fillers such as rGO when released from composites at doses expected at the workplace.

Gut microbiome interactions with graphene based nanomaterials: Challenges and opportunities

Rapid growth of nanotechnology has accelerated immense possibility of engineered nanomaterials (ENMs) exposure by human and living organisms. In this context, wide range applications of graphene based nanomaterials (GBNMs) may inevitably cause their release into the environment. Consequently, potential risks to the ecological system and human health is consistently increasing due to the probable ingestion of GBNMs by mean of contaminated water or food sources. Further, gut microbiome is known to play a profound impact on the health status of human being and has been recognized as the most exciting advancement in the biomedical science. Recent studies has shown vital role of ENMs to alter gut microbiome and thereby changed pathological status of organisms. Therefore, in this review results of numerous studies dedicated to explore the impact of GBNMs on gut microbiome and thereby various pathological status have been summarized. Dietary exposure of different types of GBNMs [e.g. graphene, graphene oxide (GO), partially reduced graphene oxide (PRGO), graphene quantum dots (GQDs)] have been evaluated on the gut microbiome through numerous in vitro and in vivo models. Moreover, emphasis has been made to evaluate different physiological responses with the short/long-term exposure of GBNMs, particularly in gastrointestinal tract (GIT) and its correlation with gut microbiome and the health status. It is reviewed that exposure of GBNMs can exert significant impact which alter the composition, diversity and function of gut microbiome. This may further appear in terms of enteric disorder along with numerous pathological changes e.g. IEC (intestinal epithelial cells) colitis, lysosomal dysfunction, inflammation, shortened colon, resorbed embryo, retardation in skeletal development, low weight of fetus, early or late dead of fetus and IBD (inflammatory bowel disease) like symptoms. Finally, potential health risks due to the exposure of GBNMs have been discussed with future perspective.

Genotoxicity of Graphene-Based Materials

Graphene-based materials (GBMs) are a broad family of novel carbon-based nanomaterials with many nanotechnology applications. The increasing market of GBMs raises concerns on their possible impact on human health. Here, we review the existing literature on the genotoxic potential of GBMs over the last ten years. A total of 50 articles including in vitro, in vivo, in silico, and human biomonitoring studies were selected. Graphene oxides were the most analyzed materials, followed by reduced graphene oxides. Most of the evaluations were performed in vitro using the comet assay (detecting DNA damage). The micronucleus assay (detecting chromosome damage) was the most used validated assay, whereas only two publications reported results on mammalian gene mutations. The same material was rarely assessed with more than one assay. Despite inhalation being the main exposure route in occupational settings, only one in vivo study used intratracheal instillation, and another one reported human biomonitoring data. Based on the studies, some GBMs have the potential to induce genetic damage, although the type of damage depends on the material. The broad variability of GBMs, cellular systems and methods used in the studies precludes the identification of physico-chemical properties that could drive the genotoxicity response to GBMs.

Biomimetically Inspired Highly Homogeneous Hydrophilization of Graphene with Poly(l-DOPA): Toward Electroconductive Coatings from Water-Processable Paints

Water-based processing of graphene-typically considered as physicochemically incompatible with water in the macroscale-emerges as the key challenge among the central postulates of green nanotechnology. These problematic concerns are derived from the complex nature of graphene in the family of sp2-carbon nanoallotropes. Indeed, nanomaterials hidden under the common "graphene" signboard are very rich in morphological and physicochemical variants. In this work, inspired by the adhesion chemistry of mussel biomaterials, we have synthesized novel, water-processable graphene-polylevodopa (PDOPA) hybrids. Graphene and PDOPA were covalently amalgamated via the "growth-from" polymerization of l-DOPA (l-3,4-dihydroxyphenylalanine) monomer in air, yielding homogeneously PDOPA-coated (23 wt %) (of thickness 10-20 nm) hydrophilic flakes. The hybrids formed >1 year stable and water-processable aqueous dispersions and further conveniently processable paints of viscosity 0.4 Pa·s at 20 s-1 and a low yield stress τ0 up to 0.12 Pa, hence exhibiting long shelf-life stability and lacking sagging after application. Demonstrating their applicability, we have found them as surfactant-like nanoparticles stabilizing the larger, pristine graphene agglomerates in water in the optimized graphene/graphene-PDOPA weight ratio of 9:1. These characteristics enabled the manufacture of conveniently paintable coatings of low surface resistivity of 1.9 kΩ sq-1 (0.21 Ω·m) which, in turn, emerge as potentially applicable in textronics, radar-absorbing materials, or electromagnetic interference shielding.

Hazard characterization of graphene nanomaterials in the frame of their food risk assessment: A review

Different applications have been suggested for graphene nanomaterials (GFNs) in the food and feed chain. However, it is necessary to perform a risk assessment before they become market-ready, and when consumer exposure is demonstrated. For this purpose, the European Food Safety Authority (EFSA) has published a guidance that has been recently updated. In this sense, the aim of this study is to identify and characterise toxicological hazards related to GFNs after oral exposure. Thus, existing scientific literature in relation to in vitro degradation studies, in vitro and in vivo genotoxicity, toxicokinetics data, in vivo oral studies, and other in-depth studies such as effects on the microbiome has been revised. The obtained results showed that the investigations performed up to now did not follow internationally agreed-upon test guidelines. Moreover, GFNs seemed to resist gastrointestinal digestion and were able to be absorbed, distributed, and excreted, inducing toxic effects at different levels, including genotoxicity. Also, dose has an important role as it has been reported that low doses are more toxic than high doses because GFNs tend to aggregate in the digestive system, changing the internal exposure scenario. Thus, further studies including a thorough toxicological evaluation are required to protect consumer's safety.

Graphene Nanoplatelets: In Vivo and In Vitro Toxicity, Cell Proliferative Activity, and Cell Gene Expression

Multi-layer graphene (2–10 layers), also called graphene nanoplatelets (GNPs), is a carbon-based nanomaterial (CBN) type with excellent properties desirable for many biomedical applications. Despite the promising advantages reported of GNPs, nanoscale materials may also present a potential hazard to humans. Therefore, in this study, the in vivo toxicity of these nanomaterials at a wide range of concentrations from 12.5 to 500 µg/mL was evaluated in the Caenorhabditis elegans model for 24 h (acute toxicity) and 72 h (chronic toxicity). Furthermore, their in vitro toxicity (from 0 to 10 µg/mL for 12 and 24 h), proliferative activity at 72 and 96 h, and their effect on the expression of thirteen genes in human keratinocytes HaCaT cells were studied. The physico-chemical and morphological aspects of the GNPs used in this study were analyzed by Raman scattering spectroscopy, electron microscopy, zeta potential as a function of pH, and particle size measurements by dynamic light scattering. The results of this study showed that GNPs showed in vivo non-toxic concentrations of 25 and 12.5 µg/mL for 24 h, and at 12.5 µg/mL for 72 h. Moreover, GNPs present time-dependent cytotoxicity (EC50 of 1.142 µg/mL and 0.760 µg/mL at 12 h and 24 h, respectively) and significant proliferative activity at the non-toxic concentrations of 0.005 and 0.01 μg/mL in the HaCaT cell line. The gene expression study showed that this multi-layer-graphene is capable of up-regulating six of the thirteen genes of human keratinocytes (SOD1, CAT, TGFB1, FN1, CDH1, and FBN), two more genes than other CBNs in their oxidized form such as multi-layer graphene oxide. Therefore, all these results reinforce the promising use of these CBNs in biomedical fields such as wound healing and skin tissue engineering.

Impact of nanomaterials on the intestinal mucosal barrier and its application in treating intestinal diseases

The intestinal mucosal barrier (IMB) is one of the important barriers to prevent harmful substances and pathogens from entering the body environment and to maintain intestinal homeostasis. The dysfunction of the IMB is associated with intestinal diseases and disorders. Nanomaterials have been widely used in medicine and as drug carriers due to their large specific surface area, strong adsorbability, and good biocompatibility. In this review, we comprehensively discuss the impact of typical nanomaterials on the IMB and summarize the treatment of intestinal diseases by using nanomaterials. The effects of nanomaterials on the IMB are mainly influenced by factors such as the dosage, size, morphology, and surface functional groups of nanomaterials. There is huge potential and a broad prospect for the application of nanomaterials in regulating the IMB for achieving an optimal therapeutic effect for antibiotics, oral vaccines, drug carriers, and so on.

Direct and Indirect Genotoxicity of Graphene Family Nanomaterials on DNA-A Review

Graphene family nanomaterials (GFNs), including graphene, graphene oxide (GO), reduced graphene oxide (rGO), and graphene quantum dots (GQDs), have manifold potential applications, leading to the possibility of their release into environments and the exposure to humans and other organisms. However, the genotoxicity of GFNs on DNA remains largely unknown. In this review, we highlight the interactions between DNA and GFNs and summarize the mechanisms of genotoxicity induced by GFNs. Generally, the genotoxicity can be sub-classified into direct genotoxicity and indirect genotoxicity. The direct genotoxicity (e.g., direct physical nucleus and DNA damage) and indirect genotoxicity mechanisms (e.g., physical destruction, oxidative stress, epigenetic toxicity, and DNA replication) of GFNs were summarized in the manuscript, respectively. Moreover, the influences factors, such as physicochemical properties, exposure dose, and time, on the genotoxicity of GFNs are also briefly discussed. Given the important role of genotoxicity in GFNs exposure risk assessment, future research should be conducted on the following: (1) developing reliable testing methods; (2) elucidating the response mechanisms associated with genotoxicity in depth; and (3) enriching the evaluation database regarding the type of GFNs, applied dosages, and exposure times.

Ex Vivo Human Colon Tissue Exposure to Pristine Graphene Activates Genes Involved in the Binding, Adhesion and Proliferation of Epithelial Cells

Toxicology studies on pristine graphene are limited and lack significant correlations with actual human response. The goal of the current study was to determine the response of total colonic human tissue to pristine graphene exposure. Biopsy punches of colon tissues from healthy human were used to assess the biological response after ex vivo exposure to graphene at three different concentrations (1, 10, and 100 µg/mL). mRNA expression of specific genes or intestinal cytokine abundance was assessed using real-time PCR or multiplex immunoassays, respectively. Pristine graphene-activated genes that are related to binding and adhesion (GTPase and KRAS) within 2 h of exposure. Furthermore, the PCNA (proliferating cell nuclear antigen) gene was upregulated after exposure to graphene at all concentrations. Ingenuity pathway analysis revealed that STAT3 and VEGF signaling pathways (known to be involved in cell proliferation and growth) were upregulated. Graphene exposure (10 µg/mL) for 24 h significantly increased levels of pro-inflammatory cytokines IFNγ, IL-8, IL-17, IL-6, IL-9, MIP-1α, and Eotaxin. Collectively, these results indicated that graphene may activate the STAT3-IL23-IL17 response axis. The findings in this study provide information on toxicity evaluation using a human-relevant ex vivo colon model and serve as a basis for further exploration of its bio-applications.

Ex vivo exposure to different types of graphene-based nanomaterials consistently alters human blood secretome

The biomedical applications of graphene-based nanomaterials (GBN) have significantly grown in the last years. Many of these applications suppose their intravenous exposure and, in this way, GBN could encounter blood cells triggering an immunological response of unknown effects. Consequently, understanding the relationships between GBN and the immune system response should be a prerequisite for its adequate use in biomedicine. In the present study, we have conducted a little explored ex vivo exposure method in order to study the complexity of the secretome given by the interactions between GBN and blood cells. Blood samples from different healthy donors were exposed to three different types of GBN widely used in the biomedical field. In this sense, graphene oxide (GO), graphene nanoplatelets (GNPs), graphene nanoribbons (GNRs) and a panel of 105 proteins representatives of the blood secretome were evaluated. The results show broad changes in both the cytokines number and the expression levels, with important changes in inflammatory response markers. Furthermore, the indirect soft-agar assay was used as a tool to unravel the global functional impact of the found secretome changes. Our results indicate that the GBN-induced altered secretome can modify the natural anchorage-independent growth capacity of HeLa cells, used as a model. As a conclusion, this study describes an innovative approach to study the potential harmful effects of GBN, providing relevant data to be considered in the biomedical context when GBN are planned to be used in patients.

IL-6/STAT3 signaling pathway regulates the proliferation and damage of intestinal epithelial cells in patients with ulcerative colitis via H3K27ac

The aim of the present study was to investigate the effect of the IL-6/STAT3 signaling pathway on intestinal epithelial barrier injury in patients with ulcerative colitis (UC). Fifty-two patients with UC and 21 healthy subjects were recruited. The expression level of IL-6 in plasma was determined by ELISA. Normal human colon mucosal epithelial NCM460 cells were treated with IL-6 or plasma from the patients with UC. Then, the transepithelial electrical resistance value, fluorescein yellow permeability and zonulin release were evaluated. Using reverse transcription-quantitative (q)PCR and western blotting, claudin (CLDN) 1 and CLDN2 expression levels were analyzed. Furthermore, western blotting was used to detect phosphorylation of STAT3. Chromatin immunoprecipitation-qPCR was performed to investigate the enrichment of H3K27ac in the promoter regions of CLDN1 and CLDN2. The present study revealed that IL-6 content was elevated in the plasma from patients with UC and increased with the progression of the disease. IL-6 was also observed to induce intestinal epithelial cell barrier injury and regulate barrier function by influencing the expression of tight junction-related proteins, as well as STAT3. The IL-6/STAT3 signaling pathway regulated transcription of CLDN1 and CLDN2 by affecting the enrichment of histone H3K27ac in their promoter regions. Thus, the significantly increased expression level of IL-6 in the peripheral blood of patients with UC indicates a positive association with the development of UC. Furthermore, the IL-6/STAT3 signaling pathway influences the function of the intestinal barrier by affecting the H3K27ac level in intestinal epithelial cells.

Time dependent impact of copper oxide nanomaterials on the expression of genes associated with oxidative stress, metal binding, inflammation and mucus secretion in single and co-culture intestinal in vitro models

The potential for ingestion of copper oxide nanomaterials (CuO NMs) is increasing due to their increased exploitation. Investigation of changes in gene expression allows toxicity to be detected at an early stage of NM exposure and can enable investigation of the mechanism of toxicity. Here, undifferentiated Caco-2 cells, differentiated Caco-2 cells, Caco-2/HT29-MTX (mucus secreting) and Caco-2/Raji B (M cell model) co-cultures were exposed to CuO NMs and copper sulphate (CuSO₄) in order to determine their impacts. Cellular responses were measured in terms of production of reactive oxygen species (ROS), the gene expression of an antioxidant (haem oxygenase 1 (HMOX1)), the pro-inflammatory cytokine (interleukin 8 (IL8)), the metal binding (metallothionein 1A and 2A (MT1A and MT2A)) and the mucus secreting (mucin 2 (MUC2)), as well as HMOX-1 protein level. While CuSO₄ induced ROS production in cells, no such effect was observed for CuO NMs. However, these particles did induce an increase in the level of HMOX-1 protein and upregulation of HMOX1, MT2A, IL8 and MUC2 genes in all cell models. In conclusion, the expression of HMOX1, IL8 and MT2A were responsive to CuO NMs at 4 to 12 h post exposure when investigating the toxicity of NMs using intestinal in vitro models. These findings can inform the selection of endpoints, timepoints and models when investigating NM toxicity to the intestine in vitro in the future.

Indole-3-propionic Acid Improved the Intestinal Barrier by Enhancing Epithelial Barrier and Mucus Barrier

Destruction in intestinal barrier is concomitant with the intestinal diseases. There is growing evidence that tryptophan-derived intestinal bacterial metabolites play a critical role in maintaining the balance of intestinal mucosa. In this study, the Caco-2/HT29 coculture model was used to evaluate the effect of indole-3-propionic acid (IPA) on the intestinal barrier and explore its underlying mechanism. We found that IPA increased transepithelial electrical resistance and decreased paracellular permeability which was consistent with the increase in tight junction proteins (claudin-1, occludin, and ZO-1). Furthermore, IPA strengthened the mucus barrier by increasing mucins (MUC2 and MUC4) and goblet cell secretion products (TFF3 and RELMβ). Additionally, IPA weakened the expression of LPS-induced inflammatory factors. These discoveries provide new views for understanding the improvement of intestinal barrier by gut microbial metabolites of aromatic amino acids.

A review on nanotoxicity and nanogenotoxicity of different shapes of nanomaterials

Nanomaterials (NMs) generally display fascinating physical and chemical properties that are not always present in bulk materials; therefore, any modification to their size, shape, or coating tends to cause significant changes in their chemical/physical and biological characteristics. The dramatic increase in efforts to use NMs renders the risk assessment of their toxicity highly crucial due to the possible health perils of this relatively uncharted territory. The different sizes and shapes of the nanoparticles are known to have an impact on organisms and an important place in clinical applications. The shape of nanoparticles, namely, whether they are rods, wires, or spheres, is a particularly critical parameter to affect cell uptake and site-specific drug delivery, representing a significant factor in determining the potency and magnitude of the effect. This review, therefore, intends to offer a picture of research into the toxicity of different shapes (nanorods, nanowires, and nanospheres) of NMs to in vitro and in vivo models, presenting an in-depth analysis of health risks associated with exposure to such nanostructures and benefits achieved by using certain model organisms in genotoxicity testing. Nanotoxicity experiments use various models and tests, such as cell cultures, cores, shells, and coating materials. This review article also attempts to raise awareness about practical applications of NMs in different shapes in biology, to evaluate their potential genotoxicity, and to suggest approaches to explain underlying mechanisms of their toxicity and genotoxicity depending on nanoparticle shape.

Genotoxicity of Nanomaterials: Advanced In Vitro Models and High Throughput Methods for Human Hazard Assessment-A Review

Changes in the genetic material can lead to serious human health defects, as mutations in somatic cells may cause cancer and can contribute to other chronic diseases. Genotoxic events can appear at both the DNA, chromosomal or (during mitosis) whole genome level. The study of mechanisms leading to genotoxicity is crucially important, as well as the detection of potentially genotoxic compounds. We consider the current state of the art and describe here the main endpoints applied in standard human in vitro models as well as new advanced 3D models that are closer to the in vivo situation. We performed a literature review of in vitro studies published from 2000–2020 (August) dedicated to the genotoxicity of nanomaterials (NMs) in new models. Methods suitable for detection of genotoxicity of NMs will be presented with a focus on advances in miniaturization, organ-on-a-chip and high throughput methods.

An in vivo study of nanorod, nanosphere, and nanowire forms of titanium dioxide using Drosophila melanogaster: toxicity, cellular uptake, oxidative stress, and DNA damage

The biological impact of nanomaterials (NMs) is determined by several factors such as size and shape, which need to be taken into consideration in any type of analysis. While investigators often prefer to conduct in vitro studies for detection of any possible adverse effects of NMs, in vivo approaches yield more relevant data for risk assessment. For this reason, Drosophila melanogaster was selected as a suitable in vivo model to characterize the potential risks associated with exposure nanorods (NRs), nanospheres (NSs), nanowires (NWs) forms of titanium dioxide (TiO₂), and their microparticulated (or bulk) form, as TiO₂. Third instar larvae (72 hr old larvae) were fed with TiO₂ (NRs, NSs, or NWs) and TiO₂ at concentrations ranging from 0.01 to 10 mM. Viability (toxicity), internalization (cellular uptake), intracellular reactive oxygen species (ROS) production, and genotoxicity (Comet assay) were the end-points evaluated in hemocyte D. melanogaster larvae. Significant intracellular oxidative stress and genotoxicity were noted at the highest exposure concentration (10 mM) of TiO₂ (NRs, NSs, or NWs), as determined by the Comet assay and ROS analysis, respectively. A concentration-effect relationship was observed in hemocytes exposed to the NMs. Data demonstrated that selected forms of TiO₂.-induced genotoxicity in D. melanogaster larvae hemocytes indicating this organism is susceptible for use as a model to examine in vivo NMs-mediated effects.