Biodistribution and toxicity of radio-labeled few layer graphene in mice after intratracheal instillation

Unravelling the toxicity of carbon nanomaterials - From cellular interactions to mechanistic understanding

The application of carbon nanomaterials in diverse fields has substantially increased their demand for commercial usage. Within the earliest decade, the development of functional materials has further increased the significance of this element. Despite the advancements recorded, the potential harmful impacts of embracing carbon nanomaterials for biological applications must be balanced against their advantages. Interestingly, many studies have neglected the intriguing and dynamic cellular interaction of carbon nanomaterials and the mechanistic understanding of their property-driven behaviour, even though common toxicity profiles have been reported. Reiterating the toxicity issue, several researchers conclude that these materials have minimal toxicity and may be safe for contact with biological systems at certain dosages. Here, we aim to provide a report on the significance of some of the properties that influence their toxicity. After that, a description of the implication of nanotoxicology in humans and living systems, revealing piece by piece their exposure routes and possible risks, will be provided. Then, an extensive discussion of the mechanistic puzzle modulating the interface between various human cellular systems and carbon nanomaterials such as carbon nanotubes, carbon dots, graphene, fullerenes, and nanodiamonds will follow. Finally, this review also sheds light on the organization that handles the risk associated with nanomaterials.

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.

Comparison of PET tracing and biodistribution between 64Cu-labeled micro-and nano-polystyrene in a murine inhalation model

INTRODUCTION

Recent studies showed the presence of microplastic in human lungs. There remains an unmet need to identify the biodistribution of microplastic after inhalation. In this study, we traced the biodistribution of inhaled micro-sized polystyrene (mPS) and/or nano-sized PS (nPS) using 64Cu with PET in mice.

METHODS

We used 0.2-0.3-µm sized mPS and 20-nm sized nPS throughout. 64Cu-DOTA-mPS, 64Cu-DOTA-nPS and/or 64CuCl2 were used to trace the distribution in the murine inhalation model. PET images were acquired using an INVEON PET scanner at 1, 12, 24, 48, and 72 h after intratracheal instillation, and the SUVmax for interesting organs were determined, biodistribution was then determined in terms of percentage injected dose/gram of tissue (%ID/g). Ex vivo tissue-radio thin-layer chromatography (Ex vivo-radioTLC) was used to demonstrate the existence of 64Cu-DOTA-PS in tissue.

RESULTS

PET image demonstrated that the amount of 64Cu-DOTA-mPS retained within the lung was significantly higher than 64Cu-DOTA-nPS until 72 h; SUVmax values of 64Cu-DOTA-mPS in lungs was 11.7 ± 5.0, 48.3 ± 6.2, 65.5 ± 2.3, 42.2 ± 13.1, and 13.2 ± 2.3 at 1, 12, 24, 48, and 72 h respectively whereas it was 31.2 ± 3.1, 17.3 ± 5.9, 10.0 ± 3.4, 8.1 ± 2.4 and 8.9 ± 3.6 for 64Cu-DOTA-nPS at the corresponding timepoints. The biodistribution data supported the PET data with a similar pattern of clearance of the radioactivity from the lung. nPS cleared rapidly post instillation in comparison to mPS within the lungs. Higher accumulation of %ID/g for nPS (roughly 2 times) were observed compared to mPS in spleen, liver, intestine, thymus, kidney, brain, salivary gland, ovary, and urinary bladder. Ex vivo-radioTLC was used to demonstrate that the detected gamma rays originated from 64Cu-DOTA-mPS or nPS.

CONCLUSION

PET image demonstrated the differences in accumulations of mPS and/or nPS between lungs and other interesting organs. The information provided may be used as the basis for future studies on the toxicity of mPS and/or nPS.

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.

Pulmonary Toxicity of Boron Nitride Nanomaterials Is Aspect Ratio Dependent

Boron nitride (BN) nanomaterials have drawn a lot of interest in the material science community. However, extensive research is still needed to thoroughly analyze their safety profiles. Herein, we investigated the pulmonary impact and clearance of two-dimensional hexagonal boron nitride (h-BN) nanosheets and boron nitride nanotubes (BNNTs) in mice. Animals were exposed by single oropharyngeal aspiration to h-BN or BNNTs. On days 1, 7, and 28, bronchoalveolar lavage (BAL) fluids and lungs were collected. On one hand, adverse effects on lungs were evaluated using various approaches (e.g., immune response, histopathology, tissue remodeling, and genotoxicity). On the other hand, material deposition and clearance from the lungs were assessed. Two-dimensional h-BN did not cause any significant immune response or lung damage, although the presence of materials was confirmed by Raman spectroscopy. In addition, the low aspect ratio h-BN nanosheets were internalized rapidly by phagocytic cells present in alveoli, resulting in efficient clearance from the lungs. In contrast, high aspect ratio BNNTs caused a strong and long-lasting inflammatory response, characterized by sustained inflammation up to 28 days after exposure and the activation of both innate and adaptive immunity. Moreover, the presence of granulomatous structures and an indication of ongoing fibrosis as well as DNA damage in the lung parenchyma were evidenced with these materials. Concurrently, BNNTs were identified in lung sections for up to 28 days, suggesting long-term biopersistence, as previously demonstrated for other high aspect ratio nanomaterials with poor lung clearance such as multiwalled carbon nanotubes (MWCNTs). Overall, we reveal the safer toxicological profile of BN-based two-dimensional nanosheets in comparison to their nanotube counterparts. We also report strong similarities between BNNTs and MWCNTs in lung response, emphasizing their high aspect ratio as a major driver of their toxicity.

One-year post-exposure assessment of 14C-few-layer graphene biodistribution in mice: single versus repeated intratracheal administration

Research on graphene-based nanomaterials has experienced exponential growth in the last few decades, driven by their unique properties and their future potential impact on our everyday life. With the increasing production and commercialization of these materials, there is significant interest in understanding their fate in vivo. Herein, we investigated the distribution of 14C-few-layer graphene (14C-FLG) flakes (lat. dim. ∼ 500 nm) in mice over a period of one year. Furthermore, we compared the effects of repeated low-dose and acute high-dose exposure by tracheal administration. The results showed that most of the radioactivity was found in the lungs in both cases, with longer elimination times in the case of acute high-dose administration. In order to gain deeper insights into the distribution pattern, we conducted ex vivo investigations using μ-autoradiography on tissue sections, revealing the heterogeneous distribution of the material following administration. For the first time, μ-autoradiography was used to conduct a comprehensive investigation into the distribution and potential presence of FLG within lung cells isolated from the exposed lungs. The presence of radioactivity in lung cells strongly suggests internalization of the 14C-FLG particles. Overall these results show the long-term accumulation of the material in the lungs over one year, regardless of the administration protocol, and the higher biopersistence of FLG in the case of an acute exposure. These findings highlight the importance of the exposure scenario in the context of intratracheal administration, which is of interest in the evaluation of the potential health risks of graphene-based nanomaterials.

Lung Persistence, Biodegradation, and Elimination of Graphene-Based Materials are Predominantly Size-Dependent and Mediated by Alveolar Phagocytes

Graphene-based materials (GBMs) have promising applications in various sectors, including pulmonary nanomedicine. Nevertheless, the influence of GBM physicochemical characteristics on their fate and impact in lung has not been thoroughly addressed. To fill this gap, the biological response, distribution, and bio-persistence of four different GBMs in mouse lungs up to 28 days after single oropharyngeal aspiration are investigated. None of the GBMs, varying in size (large versus small) and carbon to oxygen ratio as well as thickness (few-layers graphene (FLG) versus thin graphene oxide (GO)), induce a strong pulmonary immune response. However, recruited neutrophils internalize nanosheets better and degrade GBMs faster than macrophages, revealing their crucial role in the elimination of small GBMs. In contrast, large GO sheets induce more damages due to a hindered degradation and long-term persistence in macrophages. Overall, small dimensions appear to be a leading feature in the design of safe GBM pulmonary nanovectors due to an enhanced degradation in phagocytes and a faster clearance from the lungs for small GBMs. Thickness also plays an important role, since decreased material loading in alveolar phagocytes and faster elimination are found for FLGs compared to thinner GOs. These results are important for designing safer-by-design GBMs for biomedical application.

Molecular Imaging, Radiochemistry, and Environmental Pollutants

The worldwide proliferation of persistent environmental pollutants is accelerating at an alarming rate. Not surprisingly, many of these pollutants pose a risk to human health. In this review, we examine recent literature in which molecular imaging and radiochemistry have been harnessed to study environmental pollutants. Specifically, these techniques offer unique ways to interrogate the pharmacokinetic profiles and bioaccumulation patterns of pollutants at environmentally relevant concentrations, thereby helping to determine their potential health risks.

Lessons from the history of inorganic nanoparticles for inhalable diagnostics and therapeutics

The respiratory tract is one of the most accessible ones to exogenous nanoparticles, yet drug delivery by their means to it is made extraordinarily challenging because of the plexus of aerodynamic, hemodynamic and biomolecular factors at cellular and extracellular levels that synergistically define the safety and efficacy of this process. Here, the use of inorganic nanoparticles (INPs) for inhalable diagnostics and therapies of the lung is viewed through the prism of the history of studies on the interaction of INPs with the lower respiratory tract. The most conceptually and methodologically innovative and illuminative studies are referred to in the chronological order, as they were reported in the literature, and the trends in the progress of understanding this interaction of immense therapeutic and toxicological significance are being deduced from it. The most outstanding actual trends delineated include the diminishment of toxicity via surface functionalization, cell targeting, tagging and tracking via controlled binding and uptake, hybrid INP treatments, magnetic guidance, combined drug and gene delivery, use as adjuvants in inhalable vaccines, and other. Many of the understudied research directions, which have been accomplished by the nanostructured organic polymers in the pulmonary niche, are discussed. The progress in the use of INPs as inhalable diagnostics or therapeutics has been hampered by their well-recognized inflammatory potential and toxicity in the respiratory tract. However, the annual numbers of methodologically innovative studies have been on the rise throughout the past two decades, suggesting that this is a prolific direction of research, its comparatively poor commercial takings notwithstanding. Still, the lack of consensus on the effects of many INP compositions at low but therapeutically effective doses, the plethora of contradictory reports on ostensibly identical chemical compositions and NP properties, and the many cases of antagonism in combinatorial NP treatments imply that the rational design of inhalable medical devices based on INPs must rely on qualitative principles for the most part and embrace a partially stochastic approach as well. At the same time, the fact that the most studied INPs for pulmonary applications have been those with some of the thickest records of pulmonary toxicity, e.g., carbon, silver, gold, silica and iron oxide, is a silent call for the expansion of the search for new inorganic compositions for use in inhalable therapies to new territories.

Synthesis and Functionalization of Graphene Materials for Biomedical Applications: Recent Advances, Challenges, and Perspectives

Since its discovery in 2004, graphene is increasingly applied in various fields owing to its unique properties. Graphene application in the biomedical domain is promising and intriguing as an emerging 2D material with a high surface area, good mechanical properties, and unrivalled electronic and physical properties. This review summarizes six typical synthesis methods to fabricate pristine graphene (p-G), graphene oxide (GO), and reduced graphene oxide (rGO), followed by characterization techniques to examine the obtained graphene materials. As bare graphene is generally undesirable in vivo and in vitro, functionalization methods to reduce toxicity, increase biocompatibility, and provide more functionalities are demonstrated. Subsequently, in vivo and in vitro behaviors of various bare and functionalized graphene materials are discussed to evaluate the functionalization effects. Reasonable control of dose (<20 mg kg-1 ), sizes (50-1000 nm), and functionalization methods for in vivo application are advantageous. Then, the key biomedical applications based on graphene materials are discussed, coupled with the current challenges and outlooks of this growing field. In a broader sense, this review provides a comprehensive discussion on the synthesis, characterization, functionalization, evaluation, and application of p-G, GO, and rGO in the biomedical field, highlighting their recent advances and potential.

Pulmonary hazard identifications of Graphene family nanomaterials: Adverse outcome pathways framework based on toxicity mechanisms

Graphene-family nanomaterials (GFNs) are revolutionary new nanomaterials that have attracted significant attention in the field of nanomaterials, but the ensuing problems lie in the potential threats to public health and the ecosystem caused by these nanomaterials. From the perspective of GFN-related health risk assessments, this study reviews the current status of GFN-induced pathological lung events with a focus on the damage caused to different biological moieties (molecular, cellular, tissue, and organ) and the mechanistic relationships between different toxic endpoints. These multiple sites of damage were matched with existing adverse outcome pathways (AOPs) in an online knowledge base to obtain available molecular initiation events (MIEs), key events (KEs), and adverse outcomes (AOs). Among them, the MIEs were discussed in combination with the structure-activity relationship due to the correlation between toxicity and physical and chemical properties of GFNs. Based on the collection of information regarding MIEs, Kes, and AOs in addition to upstream and downstream causal extrapolation, the AOP framework for GFN-induced pulmonary toxicity was developed, highlighting the possible mechanisms of GFN-induced lung damage. This review intended to combine AOP with classic toxicological methods with a view to rapidly and accurately establishing a nanotoxicology infrastructure so as to contribute to public health risk assessment strategies through iteration from and animal models up to the population level.

A follow-up study on workers involved in the graphene production process after the introduction of exposure mitigation measures: evaluation of genotoxic and oxidative effects

During nanomaterial (NM) production, workers could be exposed, particularly by inhalation, to NMs and other chemicals used in the synthesis process, so it is important to have suitable biomarkers to monitor potential toxic effects. Aim of this study was to evaluate the effectiveness of the introduction of exposure mitigation measures on workers unintentionally exposed to graphene co-pollutants during production process monitoring the presumable reduction of workplace NM contamination and of early genotoxic and oxidative effects previously found on these workers. We used Buccal Micronucleus Cytome (BMCyt) assay and Fpg-comet test, resulted the most sensitive biomarkers on our first biomonitoring work, to measure the genotoxic effects. We also detected urinary oxidized nucleic acid bases 8-oxoGua, 8-oxoGuo and 8-oxodGuo to evaluate oxidative damage. The genotoxic and oxidative effects were assessed on the same graphene workers (N = 6) previously studied, comparing the results with those found in the first biomonitoring and with the control group (N = 11). This was achieved 6 months after the installation of a special filter hood (where to perform the phases at higher risk of NM emission) and the improvement of environmental and personal protective equipment. Particle number concentration decreased after the mitigation measures. We observed reduction of Micronucleus (MN) frequency and oxidative DNA damage and increase of 8-oxodGuo excretion compared to the first biomonitoring. These results, although limited by the small subject number, showed the efficacy of adopted exposure mitigation measures and the suitability of used sensitive and noninvasive biomarkers to bio-monitor over time workers involved in graphene production process.

Indirect mediators of systemic health outcomes following nanoparticle inhalation exposure

The growing field of nanoscience has shed light on the wide diversity of natural and anthropogenic sources of nano-scale particulates, raising concern as to their impacts on human health. Inhalation is the most robust route of entry, with nanoparticles (NPs) evading mucociliary clearance and depositing deep into the alveolar region. Yet, impacts from inhaled NPs are evident far outside the lung, particularly on the cardiovascular system and highly vascularized organs like the brain. Peripheral effects are partly explained by the translocation of some NPs from the lung into the circulation; however, other NPs largely confined to the lung are still accompanied by systemic outcomes. Omic research has only just begun to inform on the complex myriad of molecules released from the lung to the blood as byproducts of pulmonary pathology. These indirect mediators are diverse in their molecular make-up and activity in the periphery. The present review examines systemic outcomes attributed to pulmonary NP exposure and what is known about indirect pathological mediators released from the lung into the circulation. Further focus was directed to outcomes in the brain, a highly vascularized region susceptible to acute and longer-term outcomes. Findings here support the need for big-data toxicological studies to understand what drives these health outcomes and better predict, circumvent, and treat the potential health impacts arising from NP exposure scenarios.

Sub-Lethal Concentrations of Graphene Oxide Trigger Acute-Phase Response and Impairment of Phase-I Xenobiotic Metabolism in Upcyte® Hepatocytes

The impact of graphene oxide on hepatic functional cells represents a crucial evaluation step for its potential application in nanomedicine. Primary human hepatocytes are the gold standard for studying drug toxicity and metabolism; however, current technical limitations may slow down the large-scale diffusion of this cellular tool for in vitro investigations. To assess the potential hepatotoxicity of graphene oxide, we propose an alternative cell model, the second-generation upcyte^® hepatocytes, which show metabolic and functional profiles akin to primary human hepatocytes. Cells were acutely exposed to sub-lethal concentrations of graphene oxide (≤80 μg/ml) for 24 h and stress-related cell responses (such as apoptosis, oxidative stress, and inflammatory response) were evaluated, along with a broad investigation of graphene oxide impact on specialized hepatic functions. Results show a mild activation of early apoptosis but not oxidative stress or inflammatory response in our cell model. Notably, while graphene oxide clearly impacted phase-I drug-metabolism enzymes (e.g., CYP3A4, CYP2C9) through the inhibition of gene expression and metabolic activity, conversely, no effect was observed for phase-II enzyme GST and phase-III efflux transporter ABCG2. The GO-induced impairment of CYP3A4 occurs concomitantly with the activation of an early acute-phase response, characterized by altered levels of gene expression and protein production of relevant acute-phase proteins (i.e., CRP, Albumin, TFR, TTR). These data suggest that graphene oxide induces an acute phase response, which is in line with recent in vivo findings. In conclusion, upcyte^® hepatocytes appear a reliable in vitro model for assessing nanomaterial-induced hepatotoxicity, specifically showing that sub-lethal doses of graphene oxide have a negative impact on the specialized hepatic functions of these cells. The impairment of the cytochrome P450 system, along with the activation of an acute-phase response, may suggest potential detrimental consequences for human health, as altered detoxification from xenobiotics and drugs.

Impact of Particle Size on Toxicity, Tissue Distribution and Excretion Kinetics of Subchronic Intratracheal Instilled Silver Nanoparticles in Mice

The unique physicochemical properties of silver nanoparticles (AgNPs) make them useful in a wide range of sectors, increasing their propensity for human exposure, as well as the need for thorough toxicological assessment. The biodistribution of silver, hematological parameters and GSH/GSSG levels in the lung and liver were studied in mice that were intratracheally instilled with AgNP (5 and 50 nm) and AgNO₃ once a week for 5 weeks, followed by a recovery period of up to 28 days (dpi). Data was gathered to build a PBPK model after the entry of AgNPs into the lungs. AgNPs could be absorbed into the blood and might cross the physiological barriers and be distributed extensively in mice. Similar to AgNO₃, AgNP5 induced longer-lasting toxicity toward blood cells and increased GSH levels in the lung. The exposure to AgNP50 increased the GSH from 1 dpi onward in the liver and silver was distributed to the organs after exposure, but its concentration decreased over time. In AgNP5 treated mice, silver levels were highest in the spleen, kidney, liver and blood, persisting for at least 28 days, suggesting accumulation. The major route for excretion seemed to be through the urine, despite a high concentration of AgNP5 also being found in feces. The modeled silver concentration was in line with the in vivo data for the heart and liver.

Meta-analysis of Bioaccumulation Data for Nondissolvable Engineered Nanomaterials in Freshwater Aquatic Organisms

Understanding the bioaccumulation of engineered nanomaterials (ENMs) is essential for making regulatory decisions on potential environmental risks. Research in the field of ENM bioaccumulation has increased in recent years, but the compilation and statistical analysis of the available experimental data have not been updated. We therefore performed a meta-analysis of the existing literature on the bioaccumulation of eight types of nondissolvable ENMs (titanium dioxide [TiO₂ ], aluminum oxide [Al₂ O₃ ], gold [Au], fullerene [C₆₀ ], carbon nanotubes, iron oxide [FeO_x ], graphene, and polystyrene) in nonmammalian freshwater aquatic organisms across three trophic levels including phytoplankton, zooplankton, and fish. Three typical endpoints were used to assess the bioaccumulation potential: the bioconcentration factor (BCF), the bioaccumulation factor (BAF), and the biomagnification factor (BMF). Our results suggest that zooplankton has greater mean logarithmic BCF and BAF values than phytoplankton (3.31 vs. 1.42) and fish (2.04). The ENMs are biomagnified in zooplankton, with a mean BMF of 17.4, whereas trophic transfer from primary consumers (zooplankton) to secondary consumers (fish) was not observed (mean BMF of 0.13). No clear dependency was identified between the physicochemical characteristics of ENMs (e.g., primary particle size, zeta potential, or shape) and bioaccumulation, except for coated versus uncoated particles accumulated in phytoplankton. Carbonaceous ENMs were found to be more bioaccumulated than the other ENMs we considered, except for TiO₂ . A meta-analysis of bioaccumulation data can (1) deepen the understanding of bioconcentration, bioaccumulation, and biomagnification of ENMs, (2) be used to support grouping strategies as a basis for a safer-by-design approach for ENMs, (3) be integrated into comprehensive hazard and risk assessments, (4) promote the standardization of testing guidelines, and (5) enhance future kinetic bioaccumulation modeling. Environ Toxicol Chem 2022;41:1202-1214. © 2022 The Authors. Environmental Toxicology and Chemistry published by Wiley Periodicals LLC on behalf of SETAC.

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.

Innate but Not Adaptive Immunity Regulates Lung Recovery from Chronic Exposure to Graphene Oxide Nanosheets

Graphene has drawn a lot of interest in the material community due to unique physicochemical properties. Owing to a high surface area to volume ratio and free oxygen groups, the oxidized derivative, graphene oxide (GO) has promising potential as a drug delivery system. Here, the lung tolerability of two distinct GO varying in lateral dimensions is investigated, to reveal the most suitable candidate platform for pulmonary drug delivery. Following repeated chronic pulmonary exposure of mice to GO sheet suspensions, the innate and adaptive immune responses are studied. An acute and transient influx of neutrophils and eosinophils in the alveolar space, together with the replacement of alveolar macrophages by interstitial ones and a significant activation toward anti-inflammatory subsets, are found for both GO materials. Micrometric GO give rise to persistent multinucleated macrophages and granulomas. However, neither adaptive immune response nor lung tissue remodeling are induced after exposure to micrometric GO. Concurrently, milder effects and faster tissue recovery, both associated to a faster clearance from the respiratory tract, are found for nanometric GO, suggesting a greater lung tolerability. Taken together, these results highlight the importance of dimensions in the design of biocompatible 2D materials for pulmonary drug delivery system.

Effects of three graphene-based materials on the growth and photosynthesis of Brassica napus L

The environmental safety and threats of graphene-based materials (GBMs) to the agroecosystem have attracted increasing attention in recent years. However, the mechanisms underlying the effects of GBMs on plants remain unclear. Here, we investigated the phytotoxicity of reduced graphene oxide (RGO), graphene oxide (GO) and amine-functionalized graphene (G-NH2) on Brassica napus L. The results revealed that RGO impaired photosynthesis mainly by decreasing the chlorophyll content and Rubisco activity. A further gene-level analysis suggested that this effect of RGO might be due to its toxicity on sulfate transmembrane transporter and nitrogen metabolism, which ultimately led to nutrient imbalance. However, GO directly damaged the photosystem by disrupting the chloroplast structure, and a decrease in Rubisco activity indicated that GO also inhibits carbon fixation. Further gene-level analysis demonstrated that GO has toxicity on the chloroplast membrane, photosystem, photosynthethic electron transport and F-type ATPase. In addition, G-NH2 at 10-1000 mg L-1 showed no significant toxicity. These findings shed light on the potential mechanism for the toxicity of GBMs on plants for risk assessment.

Emerging investigator series: metal nanoparticles in freshwater: transformation, bioavailability and effects on invertebrates

MNPs may undergo different environmental transformations in aquatic systems, consequently changing their mobility, bioavailability and toxicity to freshwater invertebrates.

Case study: risk associated to wearing silver or graphene nanoparticle-coated facemasks for protection against COVID-19

The world is living a pandemic situation derived from the worldwide spreading of SARS-CoV-2 virus causing COVID-19. Facemasks have proven to be one of the most effective prophylactic measures to avoid the infection that has made that wearing of facemasks has become mandatory in most of the developed countries. Silver and graphene nanoparticles have proven to have antimicrobial properties and are used as coating of these facemasks to increase the effectivity of the textile fibres. In the case of silver nanoparticles, we have estimated that in a real scenario the systemic (internal) exposure derived from wearing these silver nanoparticle facemasks would be between 7.0 × 10^–5 and 2.8 × 10^–4 mg/kg bw/day. In addition, we estimated conservative systemic no effect levels between 0.075 and 0.01 mg/kg bw/day. Therefore, we estimate that the chronic exposure to silver nanoparticles derived form facemasks wearing is safe. In the case of graphene, we detected important gaps in the database, especially regarding toxicokinetics, which prevents the derivation of a systemic no effect level. Nevertheless, the qualitative approach suggests that the risk of dermal repeated exposure to graphene is very low, or even negligible. We estimated that for both nanomaterials, the risk of skin sensitisation and genotoxicity is also negligible.

Promising Graphene-Based Nanomaterials and Their Biomedical Applications and Potential Risks: A Comprehensive Review

Graphene-based nanomaterials (GBNs) have been the subject of research focus in the scientific community because of their excellent physical, chemical, electrical, mechanical, thermal, and optical properties. Several studies have been conducted on GBNs, and they have provided a detailed review and summary of various applications. However, comprehensive comments on biomedical applications and potential risks and strategies to reduce toxicity are limited. In this review, we systematically summarized the following aspects of GBNs in order to fill the gaps: (1) the history, synthesis methods, structural characteristics, and surface modification; (2) the latest advances in biomedical applications (including drug/gene delivery, biosensors, bioimaging, tissue engineering, phototherapy, and antibacterial activity); and (3) biocompatibility, potential risks (toxicity in vivo/vitro and effects on human health and the environment), and strategies to reduce toxicity. Moreover, we have analyzed the challenges to be overcome in order to enhance application of GBNs in the biomedical field.

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.

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.

Carbon-Based Nanomaterials Increase Reactivity of Primary Monocytes towards Various Bacteria and Modulate Their Differentiation into Macrophages

The evaluation of carbon-based nanomaterials' (C-BNMs') interactions with the immune system, notably their ability to cause inflammation, is a critical step in C-BNM health risk assessment. Particular attention should be given to those C-BNMs that do not cause direct cytotoxicity or inflammation on their own. However, the intracellular presence of these non-biodegradable nanomaterials could dysregulate additional cell functions. This is even more crucial in the case of phagocytes, which are the main mediators of defensive inflammation towards pathogens. Hence, our study was focused on multi-walled carbon nanotubes (MWCNTs) and two different types of graphene platelets (GPs) and whether their intracellular presence modulates a proinflammatory response from human primary monocytes towards common pathogens. Firstly, we confirmed that all tested C-BNMs caused neither direct cytotoxicity nor the release of tumour necrosis factor α (TNF-α), interleukin (IL)-6 or IL-10. However, such pre-exposed monocytes showed increased responsiveness to additional bacterial stimuli. In response to several types of bacteria, monocytes pre-treated with GP1 produced a significantly higher quantity of TNF-α, IL-6 and IL-10. Monocytes pre-treated with MWCNTs produced increased levels of IL-10. All the tested C-BNMs enhanced monocyte phagocytosis and accelerated their differentiation towards macrophages. This study confirms the immunomodulatory potential of C-BNMs.

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.

Ameliorative effect of graphene nanosheets against arsenic-induced toxicity in mice by oral exposure

Arsenic is a highly toxic environmental pollutant that is abundant in waters around the world. Previous studies have indicated that the toxicity of arsenic can be affected by co-exposure to chemicals. As a promising two-dimensional nanomaterial, graphene has received extensive attention in recent years. Owing to the wide application of graphene, its co-exposure with arsenic increases significantly. However, little information is available on the combined toxicity of graphene and arsenic. This study aimed to investigate the effects of graphene on arsenic-induced toxicity by oral exposure in mice. The results showed that the addition of graphene significantly reduced the toxicity of arsenic in the intestine and liver of mice, and the high-concentration graphene exhibited greater toxicity reduction effects. Graphene significantly decreased the bioavailability of arsenic because of its adsorption capability and spatial structure. In addition, graphene adhered to the intestinal tract may also prevent arsenic from passing through the intestinal epithelium freely. Moreover, graphene also affected arsenic toxicity through enhanced metabolism transformation by changing the gut microbiota. This study provides a comprehensive understanding of the combined toxicity of graphene and arsenic.

Toxicological Aspects of Carbon Nanotubes, Fullerenes and Graphenes

Nanomedicines exhibit unbelievable capability in overcoming the hurdles faced in biological applications. Carbon nanotubes (CNTs), graphene-family nanomaterials and fullerenes are a class of engineered nanoparticles that have emerged as a new option for possible use in drug/gene delivery for life-threatening diseases. Their adaptability to pharmaceutical applications has opened new vistas for biomedical applications. Successful applications of this family of engineered nanoparticles in various fields may not support their use in medicine due to inconsistent data on toxicity as well as the lack of a centralized toxicity database. Inconsistent toxicological studies and lack of mechanistic understanding have been the reasons for limited understanding of their toxicological aspects. These nanoparticles, when underivatized or pristine, are considered as safe, however less reactive. The derivatized forms or functionalization changes their chemistry significantly to modify their biological effects including toxicity. They can cause acute and long term injuries in tissues by penetration through the the blood-air barrier, blood-alveolus barrier, blood-brain barrier, and blood-placenta barrier. and by accumulating in the lung, liver, and spleen . The toxicological effects are manifested through inflammatory response, DNA damage, apoptosis, autophagy and necrosis. Other factors that largely influence the toxicity of carbon nanotubes, graphenes and fullerenes are the concentration, functionalization, dimensional and surface topographical factors. Thus, a better understanding of the toxicity profile of CNTs, graphene-family nanomaterials and fullerenes in humans, animals and the environment is of significant importance, to improve their biological safety, to facilitate their wide biological application and for the successful commercial application. The exploration of appropriate cell lines to investigate specific receptors and intracellular targets as well as chronic toxicity beyond the proof-of-concept is required.

Factors affecting the biological response of Graphene

Nanotechnology has gained significant importance in different fields of medical, electronic, and environmental science. This technology is founded on the use of materials at the nanoscale scale (1-100 nanometers) for various purposes, particularly in the biomedical area, where its application is growing daily due to the need of materials with advanced properties. Over the past few years, there has been a growing use for graphene and its derivative composite materials. However, different physico-chemical properties influence its biological response; therefore, further studies to explain the interactions of these nanomaterials with biological systems are critical. This review presents the current advances in the applications of graphene in biomedicine with a focus on the physico-chemical characteristics of the graphene family and their influences on biological interactions.

Graphene oxide induces dose-dependent lung injury in rats by regulating autophagy

Graphene is a two-dimensional structured material with a hexagonal honeycomb lattice composed of carbon atoms. The biological effects of graphene oxide (GO) have been extensively investigated, as it has been widely used in biological research due to its increased hydrophilicity/biocompatibility. However, the exact mechanisms underlying GO-associated lung toxicity have not yet been fully elucidated. The aim of the present study was to determine the role of GO in lung injury induction, as well as its involvement in oxidative stress, inflammation and autophagy. The results revealed that lower concentrations of GO (5 and 10 mg/kg) did not cause significant lung injury, but the administration of GO at higher concentrations (50 and 100 mg/kg) induced lung edema, and increased lung permeability and histopathological lung changes. High GO concentrations also induced oxidative injury and inflammatory reactions in the lung, demonstrated by increased levels of oxidative products [malondialdehyde(MDA) and 8-hydroxydeoxyguanosine (8-OHdG)] and inflammatory factors (TNF-α, IL-6, IL-1β and IL-8). The autophagy inhibitors 3-methyladenine (3-MA) and chloroquine (CLQ) inhibited autophagy in the lung and attenuated GO-induced lung injury, as demonstrated by a reduced lung wet-to-dry weight ratio, lower levels of protein in the bronchoalveolar lavage fluid, and a reduced lung injury score. Furthermore, 3-MA and CLQ significantly reduced the levels of MDA, 8-OHdG and inflammatory factors in lung tissue, suggesting that autophagy also mediates the development of oxidative injury and inflammation in the lung. Finally, autophagy was directly inhibited in BEAS-2B cells by short hairpin RNA-mediated autophagy protein 5 (ATG5) knockdown, which were then treated with GO. Cell viability, as well as the extent of injury (indicated by lactate dehydrogenase level) and oxidative stress were determined. The results revealed that ATG5 knockdown-induced autophagic inhibition significantly decreased cellular injury and oxidative stress, suggesting that autophagy induction is a key event that leads to lung injury during exposure to GO. In conclusion, the findings of the present study indicated that GO causes lung injury in a dose-dependent manner by inducing autophagy.

Graphene-Based Scaffolds for Regenerative Medicine

Leading-edge regenerative medicine can take advantage of improved knowledge of key roles played, both in stem cell fate determination and in cell growth/differentiation, by mechano-transduction and other physicochemical stimuli from the tissue environment. This prompted advanced nanomaterials research to provide tissue engineers with next-generation scaffolds consisting of smart nanocomposites and/or hydrogels with nanofillers, where balanced combinations of specific matrices and nanomaterials can mediate and finely tune such stimuli and cues. In this review, we focus on graphene-based nanomaterials as, in addition to modulating nanotopography, elastic modulus and viscoelastic features of the scaffold, they can also regulate its conductivity. This feature is crucial to the determination and differentiation of some cell lineages and is of special interest to neural regenerative medicine. Hereafter we depict relevant properties of such nanofillers, illustrate how problems related to their eventual cytotoxicity are solved via enhanced synthesis, purification and derivatization protocols, and finally provide examples of successful applications in regenerative medicine on a number of tissues.

Interactions Between 2D Materials and Living Matter: A Review on Graphene and Hexagonal Boron Nitride Coatings

Two-dimensional material (2DM) coatings exhibit complex and controversial interactions with biological matter, having shown in different contexts to induce bacterial cell death and contribute to mammalian cell growth and proliferation in vitro and tissue differentiation in vivo. Although several reports indicate that the morphologic and electronic properties of the coating, as well as its surface features (e.g., crystallinity, wettability, and chemistry), play a key role in the biological interaction, these kinds of interactions have not been fully understood yet. In this review, we report and classify the cellular interaction mechanisms observed in graphene and hexagonal boron nitride (hBN) coatings. Graphene and hBN were chosen as study materials to gauge the effect of two atomic-thick coatings with analogous lattice structure yet dissimilar electrical properties upon contact with living matter, allowing to discern among the observed effects and link them to specific material properties. In our analysis, we also considered the influence of crystallinity and surface roughness, detailing the mechanisms of interaction that make specific coatings of these 2DMs either hostile toward bacterial cells or innocuous for mammalian cells. In doing this, we discriminate among the material and surface properties, which are often strictly connected to the 2DM production technique, coating deposition and post-processing method. Building on this knowledge, the selection of 2DM coatings based on their specific characteristics will allow to engineer desired functionalities and devices. Antibacterial coatings to prevent biofouling, biocompatible platforms suitable for biomedical applications (e.g., wound healing, tissue repairing and regeneration, and novel biosensing devices) could be realized in the next future. Overall, a clear understanding on how the 2DM coating's properties may modulate a specific bacterial or cellular response is crucial for any future innovation in the field.

Kupffer Cells Degrade 14C-Labeled Few-Layer Graphene to 14CO2 in Liver through Erythrophagocytosis

The distribution and clearance of graphene materials as drug delivery systems at organ and suborgan levels over the long term remain unclear. Here we compared the fate of ¹⁴C-labeled few-layer graphene with different lateral sizes in mice after one intravenous injection for up to 1 year and demonstrated that few-layer graphene mainly accumulated in the liver, and larger graphene can be degraded into ¹⁴CO₂ by Kupffer cells. The mechanism involves the uptake of graphene by liver cells, larger graphene-induced membrane perturbation of red blood cells, and enhanced erythrophagocytosis by the Kupffer cells, resulting in the degradation of hemoglobin into hemes and a rise in iron concentrations in cells. The increased iron triggered a Fenton reaction to generate the hydroxyl radical, facilitating the degradation of larger graphene into ¹⁴CO₂. Our findings propose a mechanism for the transformation of graphene that significantly contributes to our understanding of the hepatic fate of graphene in vivo.

Quantifying respiratory tract deposition of airborne graphene nanoplatelets: The impact of plate-like shape and folded structure

The booming development of commercial products containing graphene nanoplatelets (GNPs) triggers growing concerns over their release into the air. Precise prediction of human respiratory system deposition of airborne GNPs, especially in alveolar region, is very important for inhalation exposure assessment. In this study, the pulmonary deposition of airborne GNPs was predicted by the multiple-path particle dosimetry (MPPD) model with consideration of GNPs plate-like shape and folded structure effect. Different equivalent diameters of GNPs were derived and utilized to describe different deposition mechanisms in the MPPD model. Both of small GNPs (geometric lateral size d_g < 0.1 μm) and large GNPs (d_g > 10 μm) had high deposition fractions in human respiratory system. The total deposition fractions for 0.1 and 30 μm GNPs were 41.6% and 75.6%, respectively. Most of the small GNPs deposited in the alveolar region, while the large GNPs deposited in the head airways. The aerodynamic diameter of GNPs was much smaller than the geometric lateral dimension due to the nanoscale thickness. For GNPs with geometric lateral size of 30 μm, the aerodynamic diameter was 2.98 μm. The small aerodynamic diameter of plate-like GNPs enabled deposition in the alveolar region, and folded GNPs had higher alveolar deposition than planar GNPs. Heavy breathing led to higher GNPs deposition fraction in head airways and lower deposition fractions in the alveolar region than resting breathing.

Recent advances in graphene-family nanomaterials for effective drug delivery and phototherapy

INTRODUCTION

Owing to the unique properties of graphene, including large specific surface area, excellent thermal conductivity, and optical absorption, graphene-family nanomaterials (GFNs) have attracted extensive attention in biomedical applications, particularly in drug delivery and phototherapy.

AREAS COVERED

In this review, we point out several challenges involved in the clinical application of GFNs. Then, we provide an overview of the most recent publications about GFNs in biomedical applications, including diverse strategies for improving the biocompatibility, specific targeting and stimuli-responsiveness of GFNs for drug delivery, codelivery of drug and gene, photothermal therapy, photodynamic therapy, and multimodal combination therapy.

EXPERT OPINION

Although the application of GFNs is still in the preclinical stage, rational modification of GFNs with functional elements or making full use of GFNs-based multimodal combination therapy might show great potential in biomedicine for clinical application.

Toxic impacts and industrial potential of graphene

Advancement in the field of nanotechnology has increased the synthesis and exploitation of graphene-like nanomaterials. Graphene is a two-dimensional planar and hexagonal array of carbon atoms. Due to its flexible nature graphene and its derivatives have several significant prospects extending from electronics to life sciences and drug delivery systems. In this review, we enlist some of the toxic effects of graphene family nanomaterials (GFNs) in various aspects of biosystems viz., in vitro, in vivo, microbial, molecular and environmental. We also appreciate their extensive and promising applications though with some underlying challenges. This review also draws attention toward current and future prospect of global graphene market for wide-range commercialization.

Radioanalytical Techniques to Quantitatively Assess the Biological Uptake and In Vivo Behavior of Hazardous Substances

Concern about environmental exposure to hazardous substances has grown over the past several decades, because these substances have adverse effects on human health. Methods used to monitor the biological uptake of hazardous substances and their spatiotemporal behavior in vivo must be accurate and reliable. Recent advances in radiolabeling chemistry and radioanalytical methodologies have facilitated the quantitative analysis of toxic substances, and whole-body imaging can be achieved using nuclear imaging instruments. Herein, we review recent literature on the radioanalytical methods used to study the biological distribution, changes in the uptake and accumulation of hazardous substances, including industrial chemicals, nanomaterials, and microorganisms. We begin with an overview of the radioisotopes used to prepare radiotracers for in vivo experiments. We then summarize the results of molecular imaging studies involving radiolabeled toxins and their quantitative assessment. We conclude the review with perspectives on the use of radioanalytical methods for future environmental research.

Graphene-Like Layers from Carbon Black: In Vivo Toxicity Assessment

Graphene-like (GL) layers, a new graphene-related material (GRM), possess peculiar chemical, colloidal, optical and transport properties. Considering the very recent promising application of GL layers in biomedical and bioelectronic fields, it is of utmost importance to investigate the toxicological profile of these nanomaterials. This study represents an important first report of a complete in vivo toxicity assessment of GL layers on embryonic zebrafish (Danio rerio). Our results show that GL layers do not lead to any perturbations in the different biological parameters evaluated, indicating their good biocompatibility on a vertebrate model. The new insight into the biosafety of GL layers will expand their applications in nanomedicine.

Chemical and Colloidal Dynamics of MnO2 Nanosheets in Biological Media Relevant for Nanosafety Assessment

Many layered crystal phases can be exfoliated or assembled into ultrathin 2D nanosheets with novel properties not achievable by particulate or fibrous nanoforms. Among these 2D materials are manganese dioxide (MnO2 ) nanosheets, which have applications in batteries, catalysts, and biomedical probes. A novel feature of MnO2 is its sensitivity to chemical reduction leading to dissolution and Mn2+ release. Biodissolution is critical for nanosafety assessment of 2D materials, but the timing and location of MnO2 biodissolution in environmental or occupational exposure scenarios are poorly understood. This work investigates the chemical and colloidal dynamics of MnO2 nanosheets in biological media for environmental and human health risk assessment. MnO2 nanosheets are insoluble in most aqueous phases, but react with strong and weak reducing agents in biological fluid environments. In vitro, reductive dissolution can be slow enough in cell culture media for MnO2 internalization by cells in the form of intact nanosheets, which localize in vacuoles, react to deplete intracellular glutathione, and induce cytotoxicity that is likely mediated by intracellular Mn2+ release. The results are used to classify MnO2 nanosheets within a new hazard screening framework for 2D materials, and the implications of MnO2 transformations for nanotoxicity testing and nanosafety assessment are discussed.

Fast Identification and Quantification of Graphene Oxide in Aqueous Environment by Raman Spectroscopy

Today, graphene nanomaterials are produced on a large-scale and applied in various areas. The toxicity and hazards of graphene materials have aroused great concerns, in which the detection and quantification of graphene are essential for environmental risk evaluations. In this study, we developed a fast identification and quantification method for graphene oxide (GO) in aqueous environments using Raman spectroscopy. GO was chemically reduced by hydrazine hydrate to form partially reduced GO (PRGO), where the fluorescence from GO was largely reduced, and the Raman signals (G band and D band) were dominating. According to the Raman characteristics, GO was easily be distinguished from other carbon nanomaterials in aqueous environments, such as carbon nanotubes, fullerene and carbon nanoparticles. The GO concentration was quantified in the range of 0.001-0.6 mg/mL with good linearity. Using our technique, we did not find any GO in local water samples. The transport of GO dispersion in quartz sands was successfully quantified. Our results indicated that GO was conveniently quantified by Raman spectroscopy after partial reduction. The potential applications of our technique in the environmental risk evaluations of graphene materials are discussed further.

Few Layer Graphene Does Not Affect Cellular Homeostasis of Mouse Macrophages

: Graphene-related materials (GRMs) are widely used in various applications due to their unique properties. A growing number of reports describe the impact of different carbon nanomaterials, including graphene oxide (GO), reduced GO (rGO), and carbon nanotubes (CNT), on immune cells, but there is still a very limited number of studies on graphene. In this work, we investigated the biological responses of few layer graphene (FLG) on mouse macrophages (bone marrow derived macrophages, BMDMs), which are part of the first line of defense in innate immunity. In particular, our paper describes our findings of short-term FLG treatment in BMDMs with a focus on observing material internalization and changes in general cell morphology. Subsequent investigation of cytotoxicity parameters showed that increasing doses of FLG did not hamper the viability of cells and did not trigger inflammatory responses. Basal level induced autophagic activity sufficed to maintain the cellular homeostasis of FLG treated cells. Our results shed light on the impact of FLG on primary macrophages and show that FLG does not elicit immunological responses leading to cell death.

Graphene Oxide Causes Disordered Zonation Due to Differential Intralobular Localization in the Liver

The liver is the primary organ to sequester nanodrugs, representing a substantial hurdle for drug delivery and raising toxicity concerns. However, the mechanistic details underlying the liver sequestration and effects on the liver are still elusive. The difficulty in studying the liver lies in its complexity, which is structured with stringently organized anatomical units called lobules. Graphene oxide (GO) has attracted attention for its applications in biomedicine, especially as a nanocarrier; however, its sequestration and effects in the liver, the major enrichment and metabolic organ, are less understood. Herein, we unveiled the differential distribution of GO in lobules in the liver, with a higher amount surrounding portal triad zones than the central vein zones. Strikingly, liver zonation patterns also changed, as reflected by changes in vital zonated genes involved in hepatocyte integrity and metabolism, leading to compromised hepatic functions. RNA-Seq and DNA methylation sequencing analyses unraveled that GO-induced changes in liver functional zonation could be ascribed to dysregulation of key signaling pathways governing liver zonation at not only mRNA transcriptions but also DNA methylation imprinting patterns, partially through TET-dependent signaling. Together, this study reveals the differential GO distribution pattern in liver lobules and pinpoints the genetic and epigenetic mechanisms in GO-induced liver zonation alterations.

Metallic Fingerprints of Carbon: Label-Free Tracking and Imaging of Graphene in Plants

Detection and quantification of carbon nanomaterials are extremely challenging, especially under the background interference of carbon. Here, we propose a new label-free method to quantify, track, and in situ image graphene and graphene oxide (GO) in plants based on their inherent metallic impurities as fingerprints. We show the ubiquity and high stability of inherent metallic fingerprints of graphene and GO obtained from different exposure routes under the natural environments, which enables the materials to be easily quantified and in situ imaged by high-sensitivity (laser ablation) inductively coupled plasma mass spectrometry. The method was applied to investigate the uptake and spatial distribution of graphene and GO in soybean plants. The plants were cultivated in graphene or GO solutions for 7 days, and the indicative elements (Ni or Mn) in different parts of plants were monitored and imaged. We found that graphene and GO showed different distribution patterns in plants (the highest uptake percentages in root up to 14.4% for graphene and 47.8% for GO), and high concentration of material exposure might cause excessive accumulation of materials in roots which blocked their further transport to the other parts of plants. The present method is more straightforward, accessible, and economical than normally used isotopic or metal-labeling methods. It also avoids the uncertainties or alterations of properties caused by the labeling process and thus has great promise in analysis and risk assessment of carbon nanomaterials.

Dispersed graphene materials of biomedical interest and their toxicological consequences

Graphene is one-atom thick nanocarbon displaying a unique honeycomb structure and extensive conjugation. In addition to high surface area to mass ratio, it displays unique optical, thermal, electronic and mechanical properties. Atomic scale tunability of graphene has attracted immense research interest with a prospective utility in electronics, desalination, energy sectors, and beyond. Its intrinsic opto-thermal properties are appealing from the standpoint of multimodal drug delivery, imaging and biosensing applications. Hydrophobic basal plane of sheets can be efficiently loaded with aromatic molecules via non-specific forces. With intense biomedical interest, methods are evolving to produce defect-free and dispersion stable sheets. This review summarizes advancements in synthetic approaches and strategies of stabilizing graphene derivatives in aqueous medium. We have described the interaction of colloidal graphene with cellular and sub-cellular components, and subsequent physiological signaling. Finally, a systematic discussion is provided covering toxicological challenges and possible solutions on utilizing graphene formulations for high-end biomedical applications.

Association between in vitro fertilization success rate and ambient air pollution: a possible explanation of within-year variation of in vitro fertilization success rate

Objective

To evaluate patterns in air pollution concentrations and in vitro fertilization (IVF) success rates using data from a large, long-term clinical database.

Methods

We conducted a retrospective cohort study investigating South Korean women who pursued IVF and embryo transfer (IVF-ET) between 2011 and 2017. Hourly concentrations of air pollutants measured at 318 air quality monitoring sites in South Korea between 2011 and 2017 were obtained from the National Institute of Environmental Research. Monthly trends in pregnancy rates and concentrations of air pollutants were assessed.

Results

A total of 34,427 IVF-ET cycles in 18,478 patients were analyzed. The mean age of women at the time of IVF-ET was 36.6 years. The clinical pregnancy rate in the IVF-ET cycle was 30%. Analysis of pregnancy failure rates by month showed that IVF-ET failure rates tended to be higher in March and April and lower in July and August. Concentrations of air pollutants including particulate matter (PM) less than 10 μm in diameter, PM less than 2.5 μm in diameter, sulfur dioxide, nitrogen dioxide, and carbon monoxide were highest in March and April and lowest between July and September.

Conclusion

Within-year variations were similar between IVF-ET failure rates and air pollution concentrations based on analysis of a large, long-term database. Specifically, IVF-ET success rates were highest when PM concentrations were lowest. Further studies are warranted to examine the mechanisms accounting for the association between IVF success and air pollutant exposure.

Exposure to graphene nanoparticles induces changes in measures of vascular/renal function in a load and form-dependent manner in mice

Graphenes isolated from crystalline graphite are used in several industries. Employees working in the production of graphenes may be at risk of developing respiratory problems attributed to inhalation or contact with particulate matter (PM). However, graphene nanoparticles might also enter the circulation and accumulate in other organs. The aim of this study was to examine how different forms of graphene affect peripheral vascular functions, generation of reactive oxygen species (ROS) and changes in gene expression that may be indicative of cardiovascular and/or renal dysfunction. In the first investigation, different doses of graphene nanoplatelets were administered to mice via oropharyngeal aspiration. These effects were compared to those of dispersion medium (DM) and carbon black (CB). Gene expression alterations were observed in the heart for CB and graphene; however, only CB produced changes in peripheral vascular function. In the second study, oxidized forms of graphene were administered. Both oxidized forms increased the sensitivity of peripheral blood vessels to adrenoreceptor-mediated vasoconstriction and induced changes in ROS levels in the heart. Based upon the results of these investigations, exposure to graphene nanoparticles produced physiological and alterations in ROS and gene expression that may lead to cardiovascular dysfunction. Evidence indicates that the effects of these particles may be dependent upon dose and graphene form to which an individual may be exposed to.

Review of Therapeutic Applications of Radiolabeled Functional Nanomaterials

In the last two decades, various nanomaterials have attracted increasing attention in medical science owing to their unique physical and chemical characteristics. Incorporating radionuclides into conventionally used nanomaterials can confer useful additional properties compared to the original material. Therefore, various radionuclides have been used to synthesize functional nanomaterials for biomedical applications. In particular, several α- or β-emitter-labeled organic and inorganic nanoparticles have been extensively investigated for efficient and targeted cancer treatment. This article reviews recent progress in cancer therapy using radiolabeled nanomaterials including inorganic, polymeric, and carbon-based materials and liposomes. We first provide an overview of radiolabeling methods for preparing anticancer agents that have been investigated recently in preclinical studies. Next, we discuss the therapeutic applications and effectiveness of α- or β-emitter-incorporated nanomaterials in animal models and the emerging possibilities of these nanomaterials in cancer therapy.

Gut microbiota of aquatic organisms: A key endpoint for ecotoxicological studies

Gut microbial communities constitute a compartment of crucial importance in regulation of homeostasis of multiple host physiological functions as well as in resistance towards environmental pollutants. Many chemical contaminants were shown to constitute a major threat for gut bacteria. Changes in gut microbiome could lead to alteration of host health. The access to high-throughput sequencing platforms permitted a great expansion of this discipline in human health while data from ecotoxicological studies are scarce and particularly those related to aquatic pollution. The main purpose of this review is to summarize recent body of literature providing data obtained from microbial community surveys using high-throughput 16S rRNA sequencing technology applied to aquatic ecotoxicity. Effects of pesticides, PCBs, PBDEs, heavy metals, nanoparticles, PPCPs, microplastics and endocrine disruptors on gut microbial communities are presented and discussed. We pointed out difficulties and limits provided by actual methodologies. We also proposed ways to improve understanding of links between changes in gut bacterial communities and host fitness loss, along with further applications for this emerging discipline.