No cytotoxicity or genotoxicity of graphene and graphene oxide in murine lung epithelial FE1 cells in vitro

In vitro evaluation of the toxicity mechanisms of two functionalized reduced graphene oxide derivatives

Dodecyl amine functionalized reduced graphene oxide (DA-rGO) and [2-(methacryloyloxy) ethyl] trimethylammonium chloride functionalized rGO (MTAC-rGO) have been developed and characterised for their further use in the food packaging industry as food contact materials. But before their application, an authorization procedure is required in which their safety plays a key role. Therefore, the aim of this work was to evaluate their toxicity with focus on two different toxicity mechanisms: genotoxicity and immunotoxicity. Following the recommendations of the European Food Safety Authority, the mutagenicity and genotoxicity were evaluated by the mouse lymphoma assay and the micronucleus assay, respectively, in L5178Y TK cells. Both assays did not show any effect at the tested concentrations (up to 200 μg/mL). The potential immunotoxicity was evaluated on two human cell lines: THP-1 (monocytes) and Jurkat (lymphocytes). The results showed that the highest cytotoxicity was induced by MTAC-rGO in Jurkat cells. The two functionalized rGO compounds did not significantly affect the differentiation process of monocytes into macrophages. In general, both compounds altered the expression of different cytokines, with the most prominent changes observed with MTAC-rGO in THP-1 cells. Moreover, MTAC-rGO induced the most evident differences in markers of cell death mechanisms. Also, for this graphene derivative, increased levels of IL-1β and TNF-α in THP-1 cell supernatants were observed by ELISA. In conclusion, a case-by-case evaluation is necessary as both functionalized rGO compounds exhibit distinct toxicity profiles that warrant further investigation before their application in the food industry.

Carbon Based Polymeric Nanocomposite Hydrogel Bioink: A Review

Carbon-based polymeric nanocomposite hydrogels (NCHs) represent a groundbreaking advancement in biomedical materials by integrating nanoparticles such as graphene, carbon nanotubes (CNTs), carbon dots (CDs), and activated charcoal (AC) into polymeric matrices. These nanocomposites significantly enhance the mechanical strength, electrical conductivity, and bioactivity of hydrogels, making them highly effective for drug delivery, tissue engineering (TE), bioinks for 3D Bioprinting, and wound healing applications. Graphene improves the mechanical and electrical properties of hydrogels, facilitating advanced tissue scaffolding and drug delivery systems. CNTs, with their exceptional mechanical strength and conductivity, enhance rheological properties, facilitating their use as bioinks in supporting complex 3D bioprinting tasks for neural, bone, and cardiac tissues by mimicking the natural structure of tissues. CDs offer fluorescence capabilities for theranostic applications, integrating imaging and therapeutic functions. AC enhances mechanical strength, biocompatibility, and antibacterial effectiveness, making it suitable for wound healing and electroactive scaffolds. Despite these promising features, challenges remain, such as optimizing nanoparticle concentrations, ensuring biocompatibility, achieving uniform dispersion, scaling up production, and integrating multiple functionalities. Addressing these challenges through continued research and development is crucial for advancing the clinical and industrial applications of these innovative hydrogels.

Impacts of graphene oxide contamination on a food web: Threats to somatic and reproductive health of organisms

Contamination of aquatic food webs with nanomaterials poses a significant ecological and human health challenge. Ingestion of nanomaterials alongside food disrupts digestion and impairs physiological processes, with potential consequences for organism fitness and survival. Complex interactions between nanomaterials and biota further exacerbate the issue, influencing life-history strategies and ecosystem dynamics. Accumulation of nanomaterials within autotrophic and detritus-based food webs raises concerns about biomagnification, especially for top-level consumers and seafood-dependent human populations. Understanding the extent and impact of nanomaterial contamination on aquatic biota is crucial for effective mitigation strategies. To address this challenge, we conducted a comprehensive study evaluating the bioaccumulation effects of graphene oxide (GO), a commonly used nanomaterial, within an aquatic food chain. Using a gnotobiotic freshwater microcosm, we investigated the effects of micro- and nano-scale GO sheets on key organisms: green algae (Chlorella vulgaris), brine shrimp (Artemia salina), and zebrafish (Danio rerio). Two feeding regimes, direct ingestion and trophic transfer, were employed to assess GO uptake and transfer within the food web. Direct exposure involved individual organisms being exposed to either nano- or micro-scale GO sheets, while trophic transfer involved a sequential exposure pathway: algae exposed to GO sheets, artemias feeding on the algae, and zebrafish consuming the artemias. Our study provides critical insights into nanomaterial contamination in aquatic ecosystems. Physicochemical properties of GO sheets, including ζ-potential and dispersion, were influenced by salt culture media, resulting in aggregation under salt conditions. Microscopic imaging confirmed the bioaccumulation of GO sheets within organisms, indicating prolonged exposure and potential long-term effects. Notably, biodistribution analysis in zebrafish demonstrated the penetration of nano-sized GO into the intestinal wall, signifying direct interaction with vital organs. Exposure to GO resulted in increased zebrafish mortality and impaired reproductive performance, particularly through trophic transfer. These findings emphasize the urgent need to address nanomaterial contamination in aquatic food webs to protect ecosystem components and human consumers. Our study highlights the importance of developing effective mitigation strategies to preserve the integrity of aquatic ecosystems, ensure resource sustainability, and safeguard human well-being. In conclusion, our study provides crucial insights into the impact of nanomaterial pollution on aquatic biota. By recognizing the challenges posed by nanomaterial contamination and implementing targeted interventions, we can mitigate the adverse effects, preserving the integrity of aquatic ecosystems and safeguarding human health.

An elevated rate of whole-genome duplications in cancers from Black patients

In the United States, Black individuals have higher rates of cancer mortality than any other racial group. Here, we examine chromosome copy number changes in cancers from more than 1800 self-reported Black patients. We find that tumors from self-reported Black patients are significantly more likely to exhibit whole-genome duplications (WGDs), a genomic event that enhances metastasis and aggressive disease, compared to tumors from self-reported white patients. This increase in WGD frequency is observed across multiple cancer types, including breast, endometrial, and lung cancer, and is associated with shorter patient survival. We further demonstrate that combustion byproducts are capable of inducing WGDs in cell culture, and cancers from self-reported Black patients exhibit mutational signatures consistent with exposure to these carcinogens. In total, these findings identify a type of genomic alteration that is associated with environmental exposures and that may influence racial disparities in cancer outcomes.

Teicoplanin-Decorated Reduced Graphene Oxide Incorporated Silk Protein Hybrid Hydrogel for Accelerating Infectious Diabetic Wound Healing and Preventing Diabetic Foot Osteomyelitis

Developing hybrid hydrogel dressings with anti-inflammatory, antioxidant, angiogenetic, and antibiofilm activities with higher bone tissue penetrability to accelerate diabetic wound healing and prevent diabetic foot osteomyelitis (DFO) is highly desirable in managing diabetic wounds. Herein, the glycopeptide teicoplanin is used for the first time as a green reductant to chemically reduce graphene oxide (GO). The resulting teicoplanin-decorated reduced graphene oxide (rGO) is incorporated into a mixture of silk proteins (SP) and crosslinked with genipin to yield a physicochemically crosslinked rGO-SP hybrid hydrogel. This hybrid hydrogel exhibits high porosity, self-healing, shear-induced thinning, increased cell proliferation and migration, and mechanical properties suitable for tissue engineering. Moreover, the hybrid hydrogel eradicates bacterial biofilms with a high penetrability index in agar and hydroxyapatite disks covered with biofilms, mimicking bone tissue. In vivo, the hybrid hydrogel accelerates the healing of noninfected wounds in a diabetic rat and infected wounds in a diabetic mouse by upregulating anti-inflammatory cytokines and downregulating matrix metalloproteinase-9, promoting M2 macrophage polarization and angiogenesis. The implantation of hybrid hydrogel into the infected site of mouse tibia improves bone regeneration. Hence, the rGO-SP hybrid hydrogel can be a promising wound dressing for treating infectious diabetic wounds, providing a further advantage in preventing DFO.

A Systematic Genotoxicity Assessment of a Suite of Metal Oxide Nanoparticles Reveals Their DNA Damaging and Clastogenic Potential

Metal oxide nanoparticles (MONP/s) induce DNA damage, which is influenced by their physicochemical properties. In this study, the high-throughput CometChip and micronucleus (MicroFlow) assays were used to investigate DNA and chromosomal damage in mouse lung epithelial cells induced by nano and bulk sizes of zinc oxide, copper oxide, manganese oxide, nickel oxide, aluminum oxide, cerium oxide, titanium dioxide, and iron oxide. Ionic forms of MONPs were also included. The study evaluated the impact of solubility, surface coating, and particle size on response. Correlation analysis showed that solubility in the cell culture medium was positively associated with response in both assays, with the nano form showing the same or higher response than larger particles. A subtle reduction in DNA damage response was observed post-exposure to some surface-coated MONPs. The observed difference in genotoxicity highlighted the mechanistic differences in the MONP-induced response, possibly influenced by both particle stability and chemical composition. The results highlight that combinations of properties influence response to MONPs and that solubility alone, while playing an important role, is not enough to explain the observed toxicity. The results have implications on the potential application of read-across strategies in support of human health risk assessment of MONPs.

Adhesion States Greatly Affect Cellular Susceptibility to Graphene Oxide: Therapeutic Implications for Cancer Metastasis

Graphene oxide (GO) has received increasing attention in the life sciences because of its potential for various applications. Although GO is generally considered biocompatible, it can negatively impact cell physiology under some circumstances. Here, we demonstrate that the cytotoxicity of GO greatly varies depending on the cell adhesion states. Human HCT-116 cells in a non-adhered state were more susceptible to GO than those in an adherent state. Apoptosis was partially induced by GO in both adhered and non-adhered cells to a similar extent, suggesting that apoptosis induction does not account for the selective effects of GO on non-adhered cells. GO treatment rapidly decreased intracellular ATP levels in non-adhered cells but not in adhered ones, suggesting ATP depletion as the primary cause of GO-induced cell death. Concurrently, autophagy induction, a cellular response for energy homeostasis, was more evident in non-adhered cells than in adhered cells. Collectively, our observations provide novel insights into GO's action with regard to cell adhesion states. Because the elimination of non-adhered cells is important in preventing cancer metastasis, the selective detrimental effects of GO on non-adhered cells suggest its therapeutic potential for use in cancer metastasis.

The effect of graphene and graphene oxide induced reactive oxygen species on polycaprolactone scaffolds for bone cancer applications

Bone cancer remains a critical healthcare problem. Among current clinical treatments, tumour resection is the most common strategy. It is usually effective but may present several limitations such as multiple operations, long hospital time, and the potential recurrence caused by the incomplete removal of cancer cells. To address these limitations, three-dimensional (3D) scaffolds fabricated through additive manufacturing have been researched for both bone cancer treatment and post-treatment rehabilitation. Polycaprolactone (PCL)-based scaffolds play an important role in bone regeneration, serving as a physical substrate to fill the defect site, recruiting cells, and promoting cell proliferation and differentiation, ultimately leading to the regeneration of the bone tissue without multiple surgical applications. Multiple advanced materials have been incorporated during the fabrication process to improve certain functions and/or modulate biological performances. Graphene-based nanomaterials, particularly graphene (G) and graphene oxide (GO), have been investigated both in vitro and in vivo, significantly improving the scaffold's physical, chemical, and biological properties, which strongly depend on the material type and concentration. A unique targeted inhibition effect on cancer cells was also discovered. However, limited research has been conducted on utilising graphene-based nanomaterials for both bone regeneration and bone cancer treatment, and there is no systematic study into the material- and dose-dependent effects, as well as the working mechanism on 3D scaffolds to realise these functions. This paper addresses these limitations by designing and fabricating PCL-based scaffolds containing different concentrations of G and GO and assessing their biological behaviour correlating it to the reactive oxygen species (ROS) release level. Results suggest that the ROS release from the scaffolds is a dominant mechanism that affects the biological behaviour of the scaffolds. ROS release also contributes to the inhibition effect on bone cancer due to healthy cells and cancer cells responding differently to ROS, and the osteogenesis results also present a certain correlation with ROS. These observations revealed a new route for realising bone cancer treatment and subsequent new bone regeneration, using a single dual-functional 3D scaffold.

Respiratory Toxicology of Graphene-Based Nanomaterials: A Review

Graphene-based nanomaterials (GBNs) consist of a single or few layers of graphene sheets or modified graphene including pristine graphene, graphene nanosheets (GNS), graphene oxide (GO), reduced graphene oxide (rGO), as well as graphene modified with various functional groups or chemicals (e.g., hydroxyl, carboxyl, and polyethylene glycol), which are frequently used in industrial and biomedical applications owing to their exceptional physicochemical properties. Given the widespread production and extensive application of GBNs, they can be disseminated in a wide range of environmental mediums, such as air, water, food, and soil. GBNs can enter the human body through various routes such as inhalation, ingestion, dermal penetration, injection, and implantation in biomedical applications, and the majority of GBNs tend to accumulate in the respiratory system. GBNs inhaled and substantially deposited in the human respiratory tract may impair lung defenses and clearance, resulting in the formation of granulomas and pulmonary fibrosis. However, the specific toxicity of the respiratory system caused by different GBNs, their influencing factors, and the underlying mechanisms remain relatively scarce. This review summarizes recent advances in the exposure, metabolism, toxicity and potential mechanisms, current limitations, and future perspectives of various GBNs in the respiratory system.

Role of Chemical Reduction and Formulation of Graphene Oxide on Its Cytotoxicity towards Human Epithelial Bronchial Cells

Graphene-based materials may pose a potential risk for human health due to occupational exposure, mainly by inhalation. This study was carried out on bronchial epithelial 16HBE14o- cells to evaluate the role of chemical reduction and formulation of graphene oxide (GO) on its cytotoxic potential. To this end, the effects of GO were compared to its chemically reduced form (rGO) and its stable water dispersion (wdGO), by means of cell viability reduction, reactive oxygen species (ROS) generation, pro-inflammatory mediators release and genotoxicity. These materials induced a concentration-dependent cell viability reduction with the following potency rank: rGO > GO >> wdGO. After 24 h exposure, rGO reduced cell viability with an EC50 of 4.8 μg/mL (eight-fold lower than that of GO) and was the most potent material in inducing ROS generation, in contrast to wdGO. Cytokines release and genotoxicity (DNA damage and micronucleus induction) appeared low for all the materials, with wdGO showing the lowest effect, especially for the former. These results suggest a key role for GO reduction in increasing GO cytotoxic potential, probably due to material structure alterations resulting from the reduction process. In contrast, GO formulated in a stable dispersion seems to be the lowest cytotoxic material, presumably due to its lower cellular internalization and damaging capacity.

In vitro safety assessment of reduced graphene oxide in human monocytes and T cells

Considering the increase in the use of graphene derivatives in different fields, the environmental and human exposure to these materials is likely, and the potential consequences are not fully elucidated. This study is focused on the human immune system, as this plays a key role in the organism's homeostasis. In this sense, the cytotoxicity response of reduced graphene oxide (rGO) was investigated in monocytes (THP-1) and human T cells (Jurkat). A mean effective concentration (EC₅₀-24 h) of 121.45 ± 11.39 μg/mL and 207.51 ± 21.67 μg/mL for cytotoxicity was obtained in THP-1 and Jurkat cells, respectively. rGO decreased THP-1 monocytes differentiation at the highest concentration after 48 h of exposure. Regarding the inflammatory response at genetic level, rGO upregulated IL-6 in THP-1 and all cytokines tested in Jurkat cells after 4 h of exposure. At 24 h, IL-6 upregulation was maintained, and a significant decrease of TNF-α gene expression was observed in THP-1 cells. Moreover, TNF-α, and INF-γ upregulation were maintained in Jurkat cells. With respect to the apoptosis/necrosis, gene expression was not altered in THP-1 cells, but a down regulation of BAX and BCL-2 was observed in Jurkat cells after 4 h of exposure. These genes showed values closer to negative control after 24 h. Finally, rGO did not trigger a significant release of any cytokine at any exposure time assayed. In conclusion, our data contributes to the risk assessment of this material and suggest that rGO has an impact on the immune system whose final consequences should be further investigated.

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.

3D printing of PLA:CaP:GO scaffolds for bone tissue applications

Graphene oxide (GO) has attracted increasing interest for biomedical applications owing to its outstanding properties such as high specific surface area, ability to bind functional molecules for therapeutic purposes and solubility, together with mechanical resistance and good thermal conductivity. The combination of GO with other biomaterials, such as calcium phosphate (CaP) and biodegradable polymers, presents a promising strategy for bone tissue engineering. Presently, the development of these advanced biomaterials benefits from the use of additive manufacturing techniques, such as 3D printing. In this study, we develop a 3D printed PLA:CaP:GO scaffold for bone tissue engineering. First, GO was characterised alone by XPS to determine its main bond contributions and C : O ratio. Secondly, we determined the GO dose which ensures the absence of toxicity, directly exposed in vitro (human osteoblast-like cells MG-63) and in vivo (zebrafish model). In addition, GO was microinjected in the zebrafish to evaluate its effect on immune cells, quantifying the genetic expression of the main markers. Results indicated that the GO tested (C : O of 2.14, 49.50% oxidised, main bonds: C-OH, C-O-C) in a dose ≤0.25 mg mL^-1 promoted MG63 cells viability percentages above 70%, and in a dose ≤0.10 mg mL^-1 resulted in the absence of toxicity in zebrafish embryos. The immune response evaluation reinforced this result. Finally, the optimised GO dose (0.10 mg mL^-1) was combined with polylactic acid (PLA) and CaP to obtain a 3D printed PLA:CaP:GO scaffold. Physicochemical characterisation (SEM/EDS, XRD, FT-Raman, nano-indentation) was performed and in vivo tests confirmed its biocompatibility, enabling a novel approach for bone tissue-related applications.

Effects of adding functionalized graphene oxide nanosheets on physical, mechanical, and anti-biofilm properties of acrylic resin: In vitro- experimental study

Background

Polymethyl methacrylate resin is widely used in orthodontic treatments. Graphene oxide (GO) has reactive functional groups on its surface that facilitate binding to various materials such as polymers, biomolecules, DNA, and proteins. This study aimed to investigate the impact of adding functionalized GO nanosheets on the physical, mechanical, cytotoxicity, and anti-biofilm properties of acrylic resin.

Materials and Methods

In this experimental study, fifty samples (for each test) were divided into groups of 10, in the form of acrylic resin discs with concentrations of 0, 0.25, 0.5, 1, and 2 weight percentage (wt%) of functionalized GO nanosheets and also the control group. Samples were evaluated in terms of physical properties (surface hardness, surface roughness, compressive strength, fracture toughness, and flexural strength), anti-biofilm properties (On four groups of micro-organisms, including Streptococcus mutans, Streptococcus sanguis, Staphylococcus aureus, and Candida albicans), and cytotoxicity. Data were analyzed using SPSS software version 22, descriptive statistics, one-way analysis of variance test, and Tukey post hoc test. The significance level was considered P < 0.05.

Results

No significant difference was observed between the different groups with weight percentages of 0.25, 0.5, 1, and 2% nano GO (nGO) and the control group (without nGO) in terms of surface roughness and toughness. However, compressive strength, three-point flexural strength, and surface hardness showed significant differences between the groups. Furthermore, the degree of cytotoxicity increased by increasing the weight percentage of nano-GO.

Conclusion

The addition of functionalized nGO in appropriate concentrations to polymethyl methacrylate can improve the anti-bacterial and anti-fungal biofilm properties without changing or increasing their physical and mechanical properties.

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.

Pulmonary toxicity of molybdenum disulphide after inhalation in mice

Molybdenum disulphide (MoS₂) is a constituent of many products. To protect humans, it is important to know at what air concentrations it becomes toxic. For this, we tested MoS₂ particles by nose-only inhalation in mice. Exposures were set to 13, 50 and 150 mg MoS₂/m³ (=8, 30 and 90 mg Mo/m³), corresponding to Low, Mid and High exposure. The duration was 30 min/day, 5 days/week for 3 weeks. Molybdenum lung-deposition levels were estimated based on aerosol particle size distribution measurements, and empirically determined with inductively coupled plasma-mass spectrometry (ICP-MS). Toxicological endpoints were body weight gain, respiratory function, pulmonary inflammation, histopathology, and genotoxicity (comet assay). Acellular reactive oxygen species (ROS) production was also determined. The aerosolised MoS₂ powder had a mean aerodynamic diameter of 800 nm, and a specific surface area of 8.96 m²/g. Alveolar deposition of MoS₂ in lung was estimated at 7, 27 and 79 µg/mouse and measured as 35, 101 and 171 µg/mouse for Low, Mid and High exposure, respectively. Body weight gain was lower than in controls at Mid and High exposure. The tidal volume was decreased with Low and Mid exposure on day 15. Increased genotoxicity was seen in bronchoalveolar lavage (BAL) fluid cells at Mid and High exposures. ROS production was substantially lower than for carbon black nanoparticles used as bench-mark, when normalised by mass. Yet if ROS of MoS₂ was normalised by surface area, it was similar to that of carbon black, suggesting that a ROS contribution to the observed genotoxicity cannot be ruled out. In conclusion, effects on body weight gain and genotoxicity indicated that Low exposure (13 mg MoS₂/m³, corresponding to 0.8 mg/m³ for an 8-hour working day) was a No Observed Adverse Effect Concentration (NOAEC,) while effects on respiratory function suggested this level as a Lowest Observed Adverse Effect Concentration (LOAEC).

Role of Solvent Used in Development of Graphene Oxide Coating on AZ31B Magnesium Alloy: Corrosion Behavior and Biocompatibility Analysis

Clinical applications of bio-absorbable magnesium (Mg) and its alloys can be enhanced by increasing their corrosion resistance, using surface modification and functionality. In this study, we synthesized graphene oxide (GO) through improved Hummers' method and deposited it on biodegradable AZ31B Mg alloy for further characterization. Different suspensions of GO were prepared in various solvents, like deionized water, ethanol, and acetone by ultra-sonication. Electrophoretic deposition (EPD) was used to develop GO coatings on AZ31B Mg using different GO suspensions. Effect of various solvents on corrosion behavior, as well as in vitro biocompatibility, was studied. The optimized EPD parameters were 3 volts and 90 s for coating. Different characterization techniques were used to study GO and prepared coatings. Atomic force microscopy found that the average thickness of GO was ~1 nm. Electrochemical behavior of coatings was studied through electrochemical impedance spectroscopy (EIS) and Tafel analysis in Ringer's lactate solution. Tafel analysis revealed that GO coatings deposited by GO water suspension increased corrosion protection efficiency of AZ31B Mg alloy by ~94%. After 72 h incubation in MC3T3-E1 osteoblast cells extract, in vitro analysis was performed to determine the cell viability and biocompatibility of the GO- coated and bare Mg samples. GO coatings deposited by GO water suspension demonstrated ~2× cell viability, as well as nontoxicity and better biocompatibility compared to the bare and other GO-coated Mg samples.

G-Optrode Bio-Interfaces for Non-Invasive Optical Cell Stimulation: Design and Evaluation

Biocompatibility and potential efficacy in biological applications rely on the bio-interactions of graphene nanoparticles with biological tissues. Analyzing and modulating cellular and device-level activity requires non-invasive electrical stimulation of cells. To address these needs, G-optrodes, bio-interfaces based on graphene, have been developed. These devices use light to stimulate cells without modifying their genetic code. Optoelectronic capabilities, in particular the capacity to transform light energy into electrical energy, will be maintained throughout the procedures of neural stimulation. G-optrodes have also been studied as thin films on a range of substrates, and they have been designed to function at a very small scale. This study examines the impact of G-optrode-based substrate designs on the optical stimulation of pheochromocytoma (PC-12). Graphene electrodes, known as G-optrodes, are responsible for converting light into electrical pulses with stimulating effects. G-optrode bio-interfaces provide a stimulus that is independent of wavelength range but is sensitive to changes in illuminance. The authors have performed a comprehensive investigation based on the correct effects of the medication in vitro, employing substrate-based G-optrode biointerfaces. In substrate-based systems, the authors have proven that graphene is biocompatible. PC-12 cells were cultured on graphene for 7 days. Based on the findings, 20-nm and 50-nm thick G-optrodes are being studied for possible use in biological and artificial retinal applications. The findings of this study highlight the significance of biocompatibility in the selection and use of G-optrodes for biomedical purposes.

Lung recovery from DNA damage induced by graphene oxide is dependent on size, dose and inflammation profile

BACKGROUND

A key aspect of any new material safety assessment is the evaluation of their in vivo genotoxicity. Graphene oxide (GO) has been studied for many promising applications, but there are remaining concerns about its safety profile, especially after inhalation. Herein we tested whether GO lateral dimension, comparing micrometric (LGO) and nanometric (USGO) GO sheets, has a role in the formation of DNA double strand breaks in mouse lungs. We used spatial resolution and differential cell type analysis to measure DNA damages in both epithelial and immune cells, after either single or repeated exposure.

RESULTS

GO induced DNA damages were size and dose dependent, in both exposure scenario. After single exposure to a high dose, both USGO and LGO induced significant DNA damage in the lung parenchyma, but only during the acute phase response (p < 0.05 for USGO; p < 0.01 for LGO). This was followed by a fast lung recovery at day 7 and 28 for both GOs. When evaluating the chronic impact of GO after repeated exposure, only a high dose of LGO induced long-term DNA damages in lung alveolar epithelia (at 84 days, p < 0.05). Regardless of size, low dose GO did not induce any significant DNA damage after repeated exposure. A multiparametric correlation analysis of our repeated exposure data revealed that transient or persistent inflammation and oxidative stress were associated to either recovery or persistent DNA damages. For USGO, recovery from DNA damage was correlated to efficient recovery from acute inflammation (i.e., significant secretion of SAA3, p < 0.001; infiltration of neutrophils, p < 0.01). In contrast, the persistence of LGO in lungs was associated to a long-lasting presence of multinucleated macrophages (up to 84 days, p < 0.05), an underlying inflammation (IL-1α secretion up to 28 days, p < 0.05) and the presence of persistent DNA damages at 84 days.

CONCLUSIONS

Overall these results highlight the importance of the exposure scenario used. We showed that LGO was more genotoxic after repeated exposure than single exposure due to persistent lung inflammation. These findings are important in the context of human health risk assessment and toward establishing recommendations for a safe use of graphene based materials in the workplace.

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.

Assessment of primary and inflammation-driven genotoxicity of carbon black nanoparticles in vitro and in vivo

Carbon black nanoparticles (CBNPs) have a large surface area/volume ratio and are known to generate oxidative stress and inflammation that may result in genotoxicity and cancer. Here, we evaluated the primary and inflammatory response-driven (i.e. secondary) genotoxicity of two CBNPs, Flammruss101 (FL101) and PrintexXE2B (XE2B) that differ in size and specific surface area (SSA), and cause different amounts of reactive oxygen species. Three doses (low, medium and high) of FL101 and XE2B were assessed in vitro in the lung epithelial (A549) and activated THP-1 (THP-1a) monocytic cells exposed in submerged conditions for 6 and 24 h, and in C57BL/6 mice at day 1, 28 and 90 following intratracheal instillation. In vitro, we assessed pro-inflammatory response as IL-8 and IL-1β gene expression, and in vivo, inflammation was determined as inflammatory cell infiltrates in bronchial lavage (BAL) fluid and as histological changes in lung tissue. DNA damage was quantified in vitro and in vivo as DNA strand breaks levels by the alkaline comet assay. Inflammatory responses in vitro and in vivo correlated with dosed CBNPs SSA. Both materials induced DNA damage in THP-1a (correlated with dosed mass), and only XE2B in A549 cells. Non-statistically significant increase in DNA damage in vivo was observed in BAL cells. In conclusion, this study shows dosed SSA predicted inflammation both in vivo and in vitro, whereas dosed mass predicted genotoxicity in vitro in THP-1a cells. The observed lack of correlation between CBNP surface area and genotoxicity provides little evidence of inflammation-driven genotoxicity in vivo and in vitro.

Systematic review on primary and secondary genotoxicity of carbon black nanoparticles in mammalian cells and animals

Carbon black exposure causes oxidative stress, inflammation and genotoxicity. The objective of this systematic review was to assess the contributions of primary (i.e. direct formation of DNA damage) and secondary genotoxicity (i.e., DNA lesions produced indirectly by inflammation) to the overall level of DNA damage by carbon black. The database is dominated by studies that have measured DNA damage by the comet assay. Cell culture studies indicate a genotoxic action of carbon black, which might be mediated by oxidative stress. Many in vivo studies originate from one laboratory that has investigated the genotoxic effects of Printex 90 in mice by intra-tracheal instillation. Meta-analysis and pooled analysis of these results demonstrate that Printex 90 exposure is associated with a slightly increased level of DNA strand breaks in bronchoalveolar lavage cells and lung tissue. Other types of genotoxic damage have not been investigated as thoroughly as DNA strand breaks, although there is evidence to suggest that carbon black exposure might increase the mutation frequency and cytogenetic endpoints. Stratification of studies according to concurrent inflammation and DNA damage does not indicate that carbon black exposure gives rise to secondary genotoxicity. Even substantial pulmonary inflammation is at best only associated with a weak genotoxic response in lung tissue. In conclusion, the review indicates that nanosized carbon black is a weak genotoxic agent and this effect is more likely to originate from a primary genotoxic mechanism of action, mediated by e.g., oxidative stress, than inflammation-driven (secondary) genotoxicity.

The High-Throughput In Vitro CometChip Assay for the Analysis of Metal Oxide Nanomaterial Induced DNA Damage

Metal oxide nanomaterials (MONMs) are among the most highly utilized classes of nanomaterials worldwide, though their potential to induce DNA damage in living organisms is known. High-throughput in vitro assays have the potential to greatly expedite analysis and understanding of MONM induced toxicity while minimizing the overall use of animals. In this study, the high-throughput CometChip assay was used to assess the in vitro genotoxic potential of pristine copper oxide (CuO), zinc oxide (ZnO), and titanium dioxide (TiO2) MONMs and microparticles (MPs), as well as five coated/surface-modified TiO2 NPs and zinc (II) chloride (ZnCl2) and copper (II) chloride (CuCl2) after 2–4 h of exposure. The CuO NPs, ZnO NPs and MPs, and ZnCl2 exposures induced dose- and time-dependent increases in DNA damage at both timepoints. TiO2 NPs surface coated with silica or silica–alumina and one pristine TiO2 NP of rutile crystal structure also induced subtle dose-dependent DNA damage. Concentration modelling at both post-exposure timepoints highlighted the contribution of the dissolved species to the response of ZnO, and the role of the nanoparticle fraction for CuO mediated genotoxicity, showing the differential impact that particle and dissolved fractions can have on genotoxicity induced by MONMs. The results imply that solubility alone may be insufficient to explain the biological behaviour of MONMs.

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.

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.

Exploring graphene-based materials' genotoxicity: inputs of a screening method

Graphene-based materials (GBMs) are promising nanomaterials, and several innovations depend on their use. However, the assessment of their potential hazard must be carefully explored before entering any market. GBMs are indeed well-known to induce various biological impacts, including oxidative stress, which can potentially lead to DNA damage. Genotoxicity is a major endpoint for hazard assessment and has been explored for GBMs, but the available literature shows conflicting results. In this study, we assessed the genotoxicity of 13 various GBMs, one carbon black and one amorphous silica through a DNA damage response assay (using a human respiratory cell model, BEAS-2B). Concurrently, oxidative stress was assessed through a ROS production quantification (DCFH-DA assay using a murine macrophage model, RAW 264.7). We also performed a full physicochemical characterization of our samples to explore potential structure-activity relationships involving genotoxicity. We observed that surface oxidation appears linked to genotoxicity response and were able to distinguish several groups within our studied GBMs showing different genotoxicity results. Our findings highlight the necessity to individually consider each nanoform of GBMs since the tested samples showed various results and modes of action. We propose this study as a genotoxicity assessment using a high-throughput screening method and suggest few hypotheses concerning the genotoxicity mode of action of GBMs.

A Study of the Impact of Graphene Oxide on Viral Infection Related to A549 and TC28a2 Human Cell Lines

Graphene has been one of the most tested materials since its discovery in 2004. It is known for its special properties, such as electrical conductivity, elasticity and flexibility, antimicrobial effect, and high biocompatibility with many mammal cells. In medicine, the antibacterial, antiviral, and antitumor properties of graphene have been tested as intensively as its drug carrying ability. In this study, the protective effect of graphene oxide against Rubella virus infection of human lung epithelial carcinoma cells and human chondrocyte cells was examined. Cells were incubated with graphene oxide alone and in combination with the Rubella virus. The cytopathic effect in two incubation time periods was measured using DAPI dye as a percentage value of the changed cells. It was shown that the graphene oxide alone has no cytopathic effect on any of tested cell lines, while the Rubella virus alone is highly cytopathic to the cells. However, in combination with the graphene oxide percentage of the changed cells, its cytotopathicity is significantly lower. Moreover, it can be concluded that graphene oxide has protective properties against the Rubella virus infection to cells, lowering its cytopathic changes to the human cells.

Toxicity screening of air extracts representing different source sectors in the Greater Toronto and Hamilton areas: In vitro oxidative stress, pro-inflammatory response, and toxicogenomic analysis

In the present study, the suitability and sensitivity of different in vitro toxicity endpoints were determined to evaluate and distinguish the specific contributions of polycyclic aromatic carbon (PAC) mixtures from various sites in Toronto (Canada), to pulmonary toxicity. Air samples were collected for two-month periods from April 2014 to March 2015 from one location, and from August 2016 to August 2017 from multiple locations reflecting different geographical areas in Toronto, and the Greater Toronto Area, with varying source emissions including background, traffic, urban, industrial and residential sites. Relative concentrations of PACs and their derivatives in these air samples were characterised. In vitro cytotoxicity, pro-inflammatory, and oxidative stress assays were employed to assess the acute pulmonary effects of urban-air-derived air pollutants. In addition, global transcriptional profiling was utilized to understand how these chemical mixtures exert their harmful effects. Lastly, the transcriptomic data and the chemical profiles for each site and season were used to relate the biological response back to individual constituents. Site-specific responses could not be derived; however, the Spring season was identified as the most responsive through benchmark concentration analysis. A combination of correlational analysis and principal component analysis revealed that nitrated and oxygenated polycyclic aromatic hydrocarbons (PAHs) drive the response at lower concentrations while specific PAHs drive the response at the highest concentration tested. Unsubstituted PAHs are the current targets for analysis as priority pollutants. The present study highlights the importance of by-products of PAH degradation in the assessment of risk. The study also demonstrates the usefulness of in vitro toxicity assays to derive meaningful data in support of risk assessment.

Pro-inflammatory response and genotoxicity caused by clay and graphene nanomaterials in A549 and THP-1 cells

Nanoclays and graphene oxide nanomaterials represent a class of materials sharing similar shapes constituted of high aspect ratio platelets. The increased production of these materials for various industrial applications increases the risk of occupational exposure, consequently with elevated risk of adverse reactions and development of pulmonary diseases, including lung cancer. In this study, pro-inflammatory responses and genotoxicity were assessed in alveolar epithelial cells (A549) and activated THP-1 macrophages (THP-1a) after exposure to three nanoclays; a pristine (Bentonite) and two surface modified (benzalkonium chloride-coated Nanofil9, and dialkyldimethyl-ammonium-coated NanofilSE3000); graphene oxide (GO) and reduced graphene oxide (r-GO) nanomaterials. The pro-inflammatory response in terms of IL-8 expression was strongest in cells exposed to Bentonite, whereas surface modification resulted in decreased toxicity in both cell lines when exposed to Nanofil9 and NanofilSE3000. GO and r-GO induced a pro-inflammatory response in A549 cells, while no effect was detected with the two nanomaterials on THP-1a cells. The pro-inflammatory response was strongly correlated with in vivo inflammation in mice after intra-tracheal instillation when doses were normalized against surface area. Genotoxicity was assessed as DNA strand breaks, using the alkaline comet assay. In A549 cells, an increase in DNA strand breaks was detected only in cells exposed to Bentonite, whereas Bentonite, NanofilSE3000 and GO caused an increased level of genotoxicity in THP-1a cells. Genotoxicity in THP-1a cells was concordant with the DNA damage in bronchoalveolar lavage fluid cells following 1 and 3 days after intra-tracheal instillation in mice. In conclusion, this study shows that surface modification of pristine nanoclays reduces the inflammatory and genotoxic response in A549 and THP-1a cells, and these in vitro models show comparable toxicity to what seen in previous mouse studies with the same materials.

Graphene oxide enriched with oxygen-containing groups: on the way to an increase of antioxidant activity and biocompatibility

The article is dedicated to the comprehensive biocompatibility investigation of synthesised graphene oxide (GO) enriched with oxygen-containing functional groups (⁓85%). GO was synthesised through a modified Hummers and Offeman's method and characterised using ¹³C NMR, Raman, and IR spectroscopy, XRD, HRTEM, along with size dimensions and ζ-potentials in aqueous dispersions. Biocompatibility study included tests on haemocompatibility (haemolysis, platelet aggregation, binding to human serum albumin and its esterase activity), antioxidant activity (2,2-diphenyl-1-picrylhydrazyl reaction, NO-radical uptake, Radachlorin photobleaching, photo-induced haemolysis), genotoxicity using DNA comet assay, as well as metabolic activity and proliferation of HEK293 cells.

Effects of Metallic and Carbon-Based Nanomaterials on Human Pancreatic Cancer Cell Lines AsPC-1 and BxPC-3

Pancreatic cancer, due to its asymptomatic development and drug-resistance, is difficult to cure. As many metallic and carbon-based nanomaterials have shown anticancer properties, we decided to investigate their potential use as anticancer agents against human pancreatic adenocarcinoma. The objective of the study was to evaluate the toxic properties of the following nanomaterials: silver (Ag), gold (Au), platinum (Pt), graphene oxide (GO), diamond (ND), and fullerenol (C₆₀(OH)₄₀) against the cell lines BxPC-3, AsPC-1, HFFF-2, and HS-5. The potential cytotoxic properties were evaluated by the assessment of the cell morphology, cell viability, and cell membrane damage. The cancer cell responses to GO and ND were analysed by determination of changes in the levels of 40 different pro-inflammatory proteins. Our studies revealed that the highest cytotoxicity was obtained after the ND treatment. Moreover, BxPC-3 cells were more sensitive to ND than AsPC-1 cells due to the ND-induced ROS production. Furthermore, in both of the cancer cell lines, ND caused an increased level of IL-8 and a decreased level of TIMP-2, whereas GO caused only decreased levels of TIMP-2 and ICAM-1 proteins. This work provides important data on the toxicity of various nanoparticles against pancreatic adenocarcinoma cell lines.

Nanomaterial- and shape-dependency of TLR2 and TLR4 mediated signaling following pulmonary exposure to carbonaceous nanomaterials in mice

Background

Pulmonary exposure to high doses of engineered carbonaceous nanomaterials (NMs) is known to trigger inflammation in the lungs paralleled by an acute phase response. Toll-like receptors (TLRs), particularly TLR2 and TLR4, have recently been discussed as potential NM-sensors, initiating inflammation. Using Tlr2 and Tlr4 knock out (KO) mice, we addressed this hypothesis and compared the pattern of inflammation in lung and acute phase response in lung and liver 24 h after intratracheal instillation of three differently shaped carbonaceous NMs, spherical carbon black (CB), multi-walled carbon nanotubes (CNT), graphene oxide (GO) plates and bacterial lipopolysaccharide (LPS) as positive control.

Results

The LPS control confirmed a distinct TLR4-dependency as well as a pronounced contribution of TLR2 by reducing the levels of pulmonary inflammation to 30 and 60% of levels in wild type (WT) mice. At the doses chosen, all NM caused comparable neutrophil influxes into the lungs of WT mice, and reduced levels were only detected for GO-exposed Tlr2 KO mice (35%) and for CNT-exposed Tlr4 KO mice (65%). LPS-induced gene expression was strongly TLR4-dependent. CB-induced gene expression was unaffected by TLR status. Both GO and MWCNT-induced Saa1 expression was TLR4-dependent. GO-induced expression of Cxcl2, Cxcl5, Saa1 and Saa3 were TLR2-dependent. NM-mediated hepatic acute phase response in terms of liver gene expression of Saa1 and Lcn2 was shown to depend on TLR2 for all three NMs. TLR4, in contrast, was only relevant for the acute phase response caused by CNTs, and as expected by LPS.

Conclusion

TLR2 and TLR4 signaling was not involved in the acute inflammatory response caused by CB exposure, but contributed considerably to that of GO and CNTs, respectively. The strong involvement of TLR2 in the hepatic acute phase response caused by pulmonary exposure to all three NMs deserves further investigations.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12989-021-00432-z.

The effects of bimodal action of photodynamic and photothermal therapy on antimicrobial and shear bond strength properties of orthodontic composite containing nano-graphene oxide

BACKGROUND

White spot lesions are a common adverse effect of fixed orthodontic treatment and represent the main challenge to achieving esthetic appearance. The purpose of the current study was to evaluate physico-mechanical and antimicrobial potency of orthodontic composite (OC; Transbond XT) containing nano-structured graphene oxide (nGO) (OC-nGO) as a novel composite following photodynamic therapy (PDT) and photothermal therapy (PTT) against Streptococcus mutans.

MATERIALS AND METHODS

Following preparation of OC-nGO, shear bond strength (SBS) and adhesive remnant index (ARI) of the test OC-nGO (containing 1, 2, 5, and 10% wt. nGO) were measured using a universal testing machine and stereomicroscope, respectively. The antimicrobial activities of test OC contained different concentrations of nGO were determined by disk agar diffusion (DAD), biofilm formation inhibition, and eluted components assays. After continuously rinsed in the aging process (up to 180 days), the antimicrobial activity of OC-nGO containing the highest concentration of nGO which had simultaneously the highest antimicrobial activity and SBS value were determined by DAD, biofilm formation, metabolic activity, and gtfB gene expression assays following photo-activation using diode laser irradiation against S. mutans. Data were analyzed using One-way Analysis of Variance (ANOVA). The Bonferroni post hoc test was used for comparison between the experimental groups. The significant difference was considered at P values < 0.05.

RESULTS

OC with 5% wt. nGO showed simultaneously the highest SBS value (10.64 ± 2.76 MPa, P < 0.05) an antimicrobial and anti-biofilm activities. The OC-nGO in all test concentrations of nGO had ARI scores as same as control group (Transbond XT without the nGO) (P < 0.05). In microbial biofilm formation and gene expression assays, the reduction of photothermal disinfection and anti-virulence activities of the 5% wt. OC-nGO against test bacterium was associated with the time of aging process, so they were reduced significantly up to day 150. Diode laser irradiated 5% wt. OC-nGO suppressed 15.6 and 8.1-fold gtfB mRNA expressions in the biofilm growth of the S. mutans at days 120 and 150 of rinsing (P < 0.05). Microbial biofilm formation and gtfB gene expression in S. mutans at day 180 following PAD had a high level of similarity with OOC as the control group. 5% wt. OC-nGO following photo-activation was not colonized by the S. mutans at day 90 and significant suppressed 91.98% and 76.37% of S. mutans biofilm formation at day 120 and 150, respectively (both P < 0.05). From day 120 onwards, metabolic activity was progressively increased on laser-irradiated 5% wt. OC-nGO discs compared to the control group (OC alone). Photo-activated OC-nGO containing 5% wt. nGO suppressed 86.94% and 46.82% metabolic activity of the S. mutans at days 120 and 150 of rinsing (both P < 0.05).

CONCLUSIONS

Our data support that the photo-activated 5% wt. OC-nGO can serve as an orthodontic composite/adhesive additive to control cariogenic bacterial biofilms.

Synthesis and Toxicity of Graphene Oxide Nanoparticles: A Literature Review of In Vitro and In Vivo Studies

Nanomaterials have been widely used in many fields in the last decades, including electronics, biomedicine, cosmetics, food processing, buildings, and aeronautics. The application of these nanomaterials in the medical field could improve diagnosis, treatment, and prevention techniques. Graphene oxide (GO), an oxidized derivative of graphene, is currently used in biotechnology and medicine for cancer treatment, drug delivery, and cellular imaging. Also, GO is characterized by various physicochemical properties, including nanoscale size, high surface area, and electrical charge. However, the toxic effect of GO on living cells and organs is a limiting factor that limits its use in the medical field. Recently, numerous studies have evaluated the biocompatibility and toxicity of GO in vivo and in vitro. In general, the severity of this nanomaterial's toxic effects varies according to the administration route, the dose to be administered, the method of GO synthesis, and its physicochemical properties. This review brings together studies on the method of synthesis and structure of GO, characterization techniques, and physicochemical properties. Also, we rely on the toxicity of GO in cellular models and biological systems. Moreover, we mention the general mechanism of its toxicity.

Mechanical properties of aerospace epoxy composites reinforced with 2D nano-fillers: current status and road to industrialization

High-performance epoxy composites find application in the aerospace industry. Although epoxy is a high-performance polymer, its fracture toughness is compromised due to its highly cross-linked nature. Nanomaterials such as carbon nanotubes (CNTs), graphene derivatives, and inorganic 2-dimensional (2D) nanomaterials are being explored to improve epoxy composites' mechanical properties. Graphene is one of the most popular 2D nano-reinforcing agents for epoxy composites. Following graphene discovery, the research community's attention was brought to various other few-atom thick 2D nanomaterials. Hence, apart from graphene, inorganic nanosheets such as transition metal dichalcogenides (TMDs), hexagonal boron nitride (hBN), etc., are also being studied as modifiers for enhancing the mechanical performance of epoxy composites. Graphene, TMDs and hBN are known to possess a high aspect ratio, high specific surface area and inherently high mechanical strength and stiffness, contributing to a stronger and tougher composite. Despite that, the challenges associated with these nanomaterials, such as dispersion issues, lack of standardization, underlying health hazards, etc., have hampered their commercialization. It has been long past a decade since the discovery of graphene, yet there are concerns regarding the lab to industry scale-up, and health and environmental hazards associated with nanomaterials for the fabrication of aerospace composites. This review offers a comprehensive literature survey and a perspective into the possible ways of bridging the gaps between the laboratory research and industrialization of 2D nanosheet-filled epoxy composites.

In Vitro Primary-Indirect Genotoxicity in Bronchial Epithelial Cells Promoted by Industrially Relevant Few-Layer Graphene

Few-layer graphene (FLG) has garnered much interest owing to applications in hydrogen storage and reinforced nanocomposites. Consequently, these engineered nanomaterials (ENMs) are in high demand, increasing occupational exposure. This investigation seeks to assess the inhalation hazard of industrially relevant FLG engineered with: (i) no surface functional groups (neutral), (ii) amine, and (iii) carboxyl group functionalization. A monoculture of human lung epithelial (16HBE14o^- ) cells is exposed to each material for 24-h, followed by cytotoxicity and genotoxicity evaluation using relative population doubling (RPD) and the cytokinesis-blocked micronucleus (CBMN) assay, respectively. Neutral-FLG induces the greatest (two-fold) significant increase (p < 0.05) in micronuclei, whereas carboxyl-FLG does not induce significant (p < 0.05) genotoxicity. These findings correlate to significant (p < 0.05) concentration-dependent increases in interleukin (IL)-8, depletion of intracellular glutathione (rGSH) and a depletion in mitochondrial ATP production. Uptake of FLG is evaluated by transmission electron microscopy, whereby FLG particles are observed within membrane-bound vesicles in the form of large agglomerates (>1 µm diameter). The findings of the present study have demonstrated the capability of neutral-FLG and amine-FLG to induce genotoxicity in 16HBE14o^- cells through primary indirect mechanisms, suggesting a possible role for carboxyl groups in scavenging radicals produced via oxidative stress.

Methods to Scale Down Graphene Oxide Size and Size Implication in Anti-cancer Applications

Despite considerable progress in the comprehension of the mechanisms involved in the origin and development of cancer, with improved diagnosis and treatment, this disease remains a major public health challenge with a considerable impact on the social and economic system, as well as on the individual. One way to improve effectiveness and reduce side effects is to consider responsive stimuli delivery systems that provide tailor-made release profiles with excellent spatial and temporal control. 2D nanomaterials possess special physicochemical properties (e.g., light, ultrasonic and magnetic responses) and biological behaviors such as endocytosis, biodistribution, biodegradation, and excretory pathways, which lead to their use in various biomedical applications. In particular, among 2D nanomaterials, graphene and its derivatives, namely graphene oxide (GO) nanomaterials, have attracted enormous attention in cancer diagnosis and therapy because they combine, in a unique material, extremely small size, NIR absorption, delocalized electrons, extremely high surface area, and versatile surface functionality. Taking into account the fundamental role played by GO size, in this review, we summarize the main methods employed to reduce and homogenize in nanometric scale the lateral dimensions of graphene oxide produced by chemical exfoliation of graphite, as well as post-synthesis separation techniques to uniform the size. We also discuss the implication of the small size in cancer treatment by exploiting GO nanocarriers as an effective theranostic tool.

A transcriptomic overview of lung and liver changes one day after pulmonary exposure to graphene and graphene oxide

Hazard evaluation of graphene-based materials (GBM) is still in its early stage and it is slowed by their large diversity in the physicochemical properties. This study explores transcriptomic differences in the lung and liver after pulmonary exposure to two GBM with similar physical properties, but different surface chemistry. Female C57BL/6 mice were exposed by a single intratracheal instillation of 0, 18, 54 or 162 μg/mouse of graphene oxide (GO) or reduced graphene oxide (rGO). Pulmonary and hepatic changes in the transcriptome were profiled to identify commonly and uniquely perturbed functions and pathways by GO and rGO. These changes were then related to previously analyzed toxicity endpoints. GO exposure induced more differentially expressed genes, affected more functions, and perturbed more pathways compared to rGO, both in lung and liver tissues. The largest differences were observed for the pulmonary innate immune response and acute phase response, and for hepatic lipid homeostasis, which were strongly induced after GO exposure. These changes collective indicate a potential for atherosclerotic changes after GO, but not rGO exposure. As GO and rGO are physically similar, the higher level of hydroxyl groups on the surface of GO is likely the main reason for the observed differences. GO exposure also uniquely induced changes in the transcriptome related to fibrosis, whereas both GBM induced similar changes related to Reactive Oxygen Species production and genotoxicity. The differences in transcriptomic responses between the two GBM types can be used to understand how physicochemical properties influence biological responses and enable hazard evaluation of GBM and hazard ranking of GO and rGO, both in relation to each other and to other nanomaterials.

Graphene Oxide affects Staphylococcus aureus and Pseudomonas aeruginosa dual species biofilm in Lubbock Chronic Wound Biofilm model

Chronic wound management becomes a complex procedure because of the persistence of forming biofilm pathogens that do not respond to antimicrobial treatment. The aim of this paper is to detect the Graphene Oxide-GO effect on Staphylococcus aureus and Pseudomonas aeruginosa dual species wound biofilm in Lubbock Chronic Wound Biofilm-LCWB model. LCWB is a recognized model that mimics the spatial microbial colonization into chronic wounds and reproduces the wound and its clot. Staphylococcus aureus PECHA 10 and P. aeruginosa PECHA 4, are the pathogens used in the study. The GO effect on both in forming and mature biofilms, is detected by the evaluation of the CFU/mg reduction, the cell viability and ultrastructural analysis of the treated LCWBs. Graphene Oxide, at 50 mg/l, shows a significant antibiofilm effect in forming and mature LCWBs. In particular, during the biofilm formation, GO reduces the S. aureus and P. aeruginosa growth of 55.05% ± 4.73 and 44.18% ± 3.91 compared to the control. In mature biofilm, GO affects S. aureus and P. aeruginosa by reducing their growth of 70.24% ± 4.47 and 63.68% ± 17.56, respectively. Images taken by SEM show that GO display a disaggregated microbial effect also disrupting the fibrin network of the wound-like biofilm framework. In conclusion, GO used against microorganisms grown in LCWB, displays a significant inhibitory action resulting in a promising tool for potential application in wound management.

Theoretical Evaluation of DNA Genotoxicity of Graphene Quantum Dots: A Combination of Density Functional Theory and Molecular Dynamics Simulations

Owing to their unique morphology, ultrasmall lateral sizes, and exceptional properties, graphene quantum dots (GQDs) hold great potential in many applications, especially in the fields of electrochemical biosensors, bioimaging, drug delivery, gene delivery, etc. Their biosafety and potential genotoxicity to human and animal cells have been a growing concern in recent years. Especially, the potential DNA damage caused by GQDs is very crucial but still unclear. In this study, the effect of GQDs on DNA damage has been evaluated by a combination of molecular dynamics (MD) simulations and density functional theory. Our results demonstrate that the DNA damaging mechanism of GQDs depends on the size of GQDs. The small GQDs (seven benzene rings) tend to enter into the interior of DNA molecules and cause a DNA base mismatch. The relatively large GQDs (61 benzene rings) tend to adsorb onto the two ends of a DNA molecule and cause DNA unwinding. Due to the strong interaction between guanine (G) and GQDs, the effect of GQDs is much larger on G than on the other three bases (A, C, and T). In addition, the concentration of GQDs could also affect the results of DNA damaging.

Reduction and functionalization of graphene oxide with L-cysteine: Synthesis, characterization and biocompatibility

This article presents data on the synthesis, identification, computer simulation and biocompatibility of graphene oxide (GO) functionalized with L-cysteine (GFC). It was determined that GO reacts with L-cysteine in two different ways: in an alkaline medium, L-cysteine reduces functional groups on the surface and at the boundaries of GO; with heating and the use of thionyl chloride, L-cysteine covalently attaches to GO through carboxylic groups only at the boundaries. The identification of GO, reduced graphene oxide and GFC was performed using various physicochemical methods, including infrared spectroscopy, Raman spectroscopy, X-ray diffraction, X-ray photoelectron spectroscopy, thermogravimetric analysis, scanning electron microscopy and high-resolution transmission electron microscopy. Biocompatibility experiments included erythrocyte hemolysis, platelet aggregation, photodynamic and antiradical activity, binding to human serum albumin, and geno- and cytotoxicity studies. Applying density functional theory and molecular dynamics allowed us to obtain the structural and dynamic characteristics of a GFC-water binary system.

Reduced graphene oxide mitigates cadmium-induced cytotoxicity and oxidative stress in HepG2 cells

Numerous applications of reduced graphene oxide (RGO) and pervasive cadmium (Cd) have led concern about their co-exposure to the environment and human. We studied the combined effects of RGO and Cd in human liver (HepG2) cells. Initially, we found that RGO (up to 50 μg/ml) did not harm to HepG2 cells while Cd induced dose-dependent (1-10 μg/ml) cytotoxicity. Exciting observations were that a non-cytotoxic concentration of RGO (25 μg/ml) effectively mitigates the toxic effects of Cd (2 μg/ml) such as cell viability reduction, lactate dehydrogenase release, and irregular cell morphology. Cd-induced cell cycle arrest, induction of caspases (3 and 9) enzymes activity, and loss of mitochondrial membrane potential were also significantly alleviated by RGO co-exposure. Moreover, generation of pro-oxidants (reactive oxygen species and hydrogen peroxide levels) and depletion of antioxidants (glutathione level and superoxide dismutase activity) due to Cd exposure was effectively attenuated by RGO co-exposure. Mitigating effect of RGO could be due to strong adsorption of Cd on the large surface area of RGO sheets, which decrease the cellular uptake and bioavailability of Cd for HepG2 cells. This study warrants future research on potential mechanisms of mitigating effects of RGO against Cd-induced toxicity in animal models.

Organomodified nanoclays induce less inflammation, acute phase response, and genotoxicity than pristine nanoclays in mice lungs

Surface modification by different quaternary ammonium compounds (QAC) makes nanoclays more compatible with various polymeric matrices, thereby expanding their potential applications. The growing industrial use of nanoclays could potentially pose a health risk for workers. Here, we assessed how surface modification of nanoclays modulates their pulmonary toxicity. An in vitro screening of the unmodified nanoclay Bentonite (montmorillonite) and four organomodified nanoclays (ONC); coated with various QAC, including benzalkonium chloride (BAC), guided the selection of the materials for the in vivo study. Mice were exposed via a single intratracheal instillation to 18, 54, and 162 µg of unmodified Bentonite or dialkyldimethyl-ammonium-coated ONC (NanofilSE3000), or to 6, 18, and 54 µg of a BAC-coated ONC (Nanofil9), and followed for one, 3, or 28 days. All materials induced dose- and time-dependent responses in the exposed mice. However, all doses of Bentonite induced larger, but reversible, inflammation (BAL neutrophils) and acute phase response (Saa3 gene expression in lung) than the two ONC. Similarly, highest levels of DNA strand breaks were found in BAL cells of mice exposed to Bentonite 1 day post-exposure. A significant increase of DNA strand breaks was detected also for NanofilSE3000, 3 days post-exposure. Only mice exposed to Bentonite showed increased Tgf-β gene expression in lung, biomarker of pro-fibrotic processes and hepatic extravasation, 3 days post-exposure. This study indicates that Bentonite treatment with some QAC changes main physical-chemical properties, including shape and surface area, and may decrease their pulmonary toxicity in exposed mice.

Reduced graphene oxide membranes in ocular regenerative medicine

Biological membranes are currently used in Ophthalmology in order to treat different ocular disorders. These membranes have different properties such as cellular biocompatibility and promoting wound healing. Moreover, intrinsic antimicrobial properties could also be desirable because it would allow their use reducing the risk of infections. Graphene and its derivatives are promising biomaterials that already proved their bactericidal effect. However, their clinical use is limited due to the controversial results regarding their toxicity. In this work, we have developed and characterized a reduced graphene oxide membrane (rGOM) for its use in ocular Regenerative Medicine, and studied its in vitro and in vivo biocompatibility and genotoxicity with different types of human ocular cells. We proved that rGOM allowed the growth of different ocular cells without inducing in vitro or in vivo cytotoxicity or genotoxicity in the short-term. These results indicate that rGOM may be a promising candidate in Regenerative Medicine for the treatment of different ocular pathologies.

Alleviating effects of reduced graphene oxide against lead-induced cytotoxicity and oxidative stress in human alveolar epithelial (A549) cells

Broad application of reduced graphene oxide (rGO) and ubiquitous lead (Pb) pollution may increase the possibility of combined exposure of humans. Information on the combined effects of rGO and Pb in human cells is scarce. This work was designed to explore the potential effects of rGO on Pb-induced toxicity in human alveolar epithelial (A549) cells. Prepared rGO was polycrystalline in nature. The formation of a few layers of visible creases and silky morphology due to high aspect ratio was confirmed. Low level (25 μg/mL) of rGO was not toxic to A549 cells. However, Pb exposure (25 μg/mL) induced cell viability reduction, lactate dehydrogenase enzyme leakage with rounded morphology in A549 cells. Remarkably, Pb-induced cytotoxicity was significantly mitigated by rGO co-exposure. Pb-induced mitochondrial membrane potential loss, cell cycle arrest and higher activity of caspase-3 and -9 enzymes were also alleviated by rGO co-exposure. Moreover, we observed that Pb exposure causes generation of pro-oxidants (e.g., reactive oxygen species, hydrogen peroxide and lipid peroxidation) and antioxidant depletion (e.g., glutathione and antioxidant enzymes). In addition, the effects of Pb on pro-oxidant and antioxidant markers were significantly reverted by GO co-exposure. Inductively coupled plasma-mass spectrometry suggested that due to the adsorption of Pb on rGO sheets, accessibility of Pb ions for A549 cells was limited. Hence, rGO reduced the toxicity of Pb in A549 cells. This research warrants further study to work on detailed underlying mechanisms of the mitigating effects of rGO against Pb-induced toxicity on a molecular level.

Repeated exposure to aerosolized graphene oxide mediates autophagy inhibition and inflammation in a three-dimensional human airway model

Hazard evaluation of engineered nanomaterials (ENMs) using real-world exposure scenario could provide better interpretation of toxicity end points for their use in the assessment of human safety and for their implications in many fields such as toxicology, nanomedicine, and so forth. However, most of the current studies, both in vivo and in vitro, do not reflect realistic conditions of human exposure to ENMs, due to the high doses implemented. Moreover, the use of cellular models cultured under submerged conditions limits their physiological relevance for lung exposure, where cells are primarily cultured at the air-liquid interface. Addressing such issues is even more challenging for emergent nanomaterials, such as graphene oxide (GO), for which little or no information on exposure is available. In this work, we studied the impact of repeated exposure of GO on a three-dimensional (3D) reconstruct of human bronchial tissue, using a nebulizer system focusing on short-term effects. The selected doses (reaching a maximum of ca. 20 ​μg/cm² for a period of 4 weeks of exposure) were extrapolated from alveolar mass deposition values of a broader class of carbon-based nanomaterials, reflecting a full working lifetime of human exposure. Experimental results did not show strong toxic effects of GO in terms of viability and integrity of the lung tissue. However, since 2 weeks of treatment, repeated GO exposure elicited a proinflammatory response, moderate barrier impairment, and autophagosome accumulation, a process resulting from blockade of autophagy flux. Interestingly, the 3D airway model could recover such an effect by restoring autophagy flux at longer exposure (30 days). These findings indicate that prolonged exposure to GO produces a time window (during the 30 days of treatment set for this study) for which GO-mediated autophagy inhibition along with inflammation may potentially increase the susceptibility of exposed humans to pulmonary infections and/or lung diseases. This study also highlights the importance of using physiologically relevant in vitro models and doses derived from real-world exposure to obtain focused data for the assessment of human safety.