Tissue distribution and urinary excretion of intravenously administered chemically functionalized graphene oxide sheets

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.

Graphene Oxide Nanosheets Hamper Glutamate Mediated Excitotoxicity and Protect Neuronal Survival In An In vitro Stroke Model

Small graphene oxide (s-GO) nanosheets reversibly downregulate central nervous system (CNS) excitatory synapses, with potential developments as future therapeutic tools to treat neuro-disorders characterized by altered glutamatergic transmission. Excitotoxicity, namely cell death triggered by exceeding ambient glutamate fueling over-activation of excitatory synapses, is a pathogenic mechanism shared by several neural diseases, from ischemic stroke to neurodegenerative disorders. In this work, CNS cultures were exposed to oxygen-glucose deprivation (OGD) to mimic ischemic stroke in vitro, and it is show that the delivery of s-GO following OGD, during the endogenous build-up of secondary damage and excitotoxicity, improved neuronal survival. In a different paradigm, excitotoxicity cell damage was reproduced through exogenous glutamate application, and s-GO co-treatment protected neuronal integrity, potentially by directly downregulating the synaptic over-activation brought about by exogenous glutamate. This proof-of-concept study suggests that s-GO may find novel applications in therapeutic developments for treating excitotoxicity-driven neural cell death.

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.

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.

Graphene Oxide Nanosheets Reduce Astrocyte Reactivity to Inflammation and Ameliorate Experimental Autoimmune Encephalomyelitis

In neuroinflammation, astrocytes play multifaceted roles that regulate the neuronal environment. Astrocytes sense and respond to pro-inflammatory cytokines (CKs) and, by a repertoire of intracellular Ca²⁺ signaling, contribute to disease progression. Therapeutic approaches wish to reduce the overactivation in Ca²⁺ signaling in inflammatory-reactive astrocytes to restore dysregulated cellular changes. Cell-targeting therapeutics might take advantage by the use of nanomaterial-multifunctional platforms such as graphene oxide (GO). GO biomedical applications in the nervous system involve therapeutic delivery and sensing, and GO flakes were shown to enable interfacing of neuronal and glial membrane dynamics. We exploit organotypic spinal cord cultures and optical imaging to explore Ca²⁺ changes in astrocytes, and we report, when spinal tissue is exposed to CKs, neuroinflammatory-associated modulation of resident glia. We show the efficacy of GO to revert these dynamic changes in astrocytic reactivity to CKs, and we translate this potential in an animal model of immune-mediated neuroinflammatory disease.

Renal clearance of graphene oxide: glomerular filtration or tubular secretion and selective kidney injury association with its lateral dimension

BACKGROUND

Renal excretion is one of the major routes of nanomaterial elimination from the body. Many previous studies have found that graphene oxide nanosheets are excreted in bulk through the kidneys. However, how the lateral size affects GO disposition in the kidneys including glomerular filtration, active tubular secretion and tubular reabsorption is still unknown.

RESULTS

The thin, two-dimensional graphene oxide nanosheets (GOs) was observed to excrete in urine through the kidneys, but the lateral dimension of GOs affects their renal clearance pathway and renal injury. The s-GOs could be renal excreted via the glomerular filtration, while the l-GOs were predominately excreted via proximal tubular secretion at a much faster renal clearance rate than the s-GOs. For the tubular secretion of l-GOs, the mRNA level of basolateral organic anion transporters Oat1 and Oat2 in the kidney presented dose dependent increase, while no obvious alterations of the efflux transporters such as Mdr1 and Mrp4 mRNA expression levels were observed, suggesting the accumulation of l-GOs. During the GO renal elimination, mostly the high dose of 15 mg/kg s-GO and l-GO treatment showed obvious kidney injuries but at different renal compartment, i.e., the s-GOs induced obvious glomerular changes in podocytes, while the l-GOs induced more obvious tubular injuries including necrosis of renal tubular epithelial cells, loss of brush border, cast formation and tubular dilatation. The specifically tubular injury biomarkers KIM1 and NGAL were shown slight increase with mRNA levels in l-GO administrated mice.

CONCLUSIONS

This study shows that the lateral size of GOs affected their interactions with different renal compartments, renal excretion pathways and potential kidney injuries.

Doped Graphene To Mimic the Bacterial NADH Oxidase for One-Step NAD+ Supplementation in Mammals

Nicotinamide adenine dinucleotide (NAD) is a critical regulator of metabolic networks, and declining levels of its oxidized form, NAD⁺, are closely associated with numerous diseases. While supplementing cells with precursors needed for NAD⁺ synthesis has shown poor efficacy in combatting NAD⁺ decline, an alternative strategy is the development of synthetic materials that catalyze the oxidation of NADH into NAD⁺, thereby taking over the natural role of the NADH oxidase (NOX) present in bacteria. Herein, we discovered that metal-nitrogen-doped graphene (MNGR) materials can catalyze the oxidation of NADH into NAD⁺. Among MNGR materials with different transition metals, Fe-, Co-, and Cu-NGR displayed strong catalytic activity combined with >80% conversion of NADH into NAD⁺, similar specificity to NOX for abstracting hydrogen from the pyridine ring of nicotinamide, and higher selectivity than 51 other nanomaterials. The NOX-like activity of FeNGR functioned well in diverse cell lines. As a proof of concept of the in vivo application, we showed that FeNGR could specifically target the liver and remedy the metabolic flux anomaly in obesity mice with NAD⁺-deficient cells. Overall, our study provides a distinct insight for exploration of drug candidates by design of synthetic materials to mimic the functions of unique enzymes (e.g., NOX) in bacteria.

Antifungal Effect of Nanoparticles against COVID-19 Linked Black Fungus: A Perspective on Biomedical Applications

Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) is a highly transmissible and pathogenic coronavirus that has caused a 'coronavirus disease 2019' (COVID-19) pandemic in multiple waves, which threatens human health and public safety. During this pandemic, some patients with COVID-19 acquired secondary infections, such as mucormycosis, also known as black fungus disease. Mucormycosis is a serious, acute, and deadly fungal infection caused by Mucorales-related fungal species, and it spreads rapidly. Hence, prompt diagnosis and treatment are necessary to avoid high mortality and morbidity rates. Major risk factors for this disease include uncontrolled diabetes mellitus and immunosuppression that can also facilitate increases in mucormycosis infections. The extensive use of steroids to prevent the worsening of COVID-19 can lead to black fungus infection. Generally, antifungal agents dedicated to medical applications must be biocompatible, non-toxic, easily soluble, efficient, and hypoallergenic. They should also provide long-term protection against fungal growth. COVID-19-related black fungus infection causes a severe increase in fatalities. Therefore, there is a strong need for the development of novel and efficient antimicrobial agents. Recently, nanoparticle-containing products available in the market have been used as antimicrobial agents to prevent bacterial growth, but little is known about their efficacy with respect to preventing fungal growth, especially black fungus. The present review focuses on the effect of various types of metal nanoparticles, specifically those containing silver, zinc oxide, gold, copper, titanium, magnetic, iron, and carbon, on the growth of various types of fungi. We particularly focused on how these nanoparticles can impact the growth of black fungus. We also discussed black fungus co-infection in the context of the global COVID-19 outbreak, and management and guidelines to help control COVID-19-associated black fungus infection. Finally, this review aimed to elucidate the relationship between COVID-19 and mucormycosis.

Respiratory exposure to graphene oxide induces pulmonary fibrosis and organ damages in rats involving caspase-1/p38MAPK/TGF-β1 signaling pathways

Numerous studies have shown that graphene oxide (GO) respiratory exposure led to severe lung injury, but whether pulmonary fibrosis caused by GO respiratory exposure is related to the activation of the caspase-1/p38MAPK/TGF-β1 remains unclear. In this study, rats were administrated GO by intratracheal instillation and fed for three months, and the molecular mechanisms of GO on the pulmonary fibrosis and other organ damage caused by GO respiratory exposure were examined. The results showed that the expression of caspase-1/p38MAPK/TGF-β1 pathway-related factors were significantly elevated with the increase of exposure concentrations of GO. Those data proved that the caspase-1/p38MAPK/TGF-β1 signaling pathway was involved in the pulmonary fibrosis caused by GO respiratory exposure. The trends of related factors also proved that the caspase-1/p38MAPK/TGF-β1 pathway was likely to play a dominant role in the sub-acute and sub-chronic stages. The other organ damage examination found that the liver and spleen were damaged initially by the GO respiratory exposure. Meanwhile for the testicle, although the acute injury was severe, signs of recovery were found during the three-month trial period.

Carbon-based Nanomaterials for delivery of small RNA molecules: a focus on potential cancer treatment applications

BACKGROUND

Nucleic acid-mediated therapy holds immense potential in the treatment of recalcitrant human diseases such as cancer. This is underscored by advances in understanding the mechanisms of gene regulation. In particular, the endogenous protective mechanism of gene silencing known as RNA interference (RNAi) has been extensively exploited.

METHODS

We review here the developments from 2011 to 2021, in the use of nanographene oxide, carbon nanotubes, fullerenes, carbon nanohorns, carbon nanodots and nanodiamonds for the delivery of therapeutic small RNA molecules.

RESULTS

Appropriately designed effector molecules such as small interfering RNA (siRNA), can, in theory, silence the expression of any disease-causing gene. Alternatively, siRNA can be generated in vivo through the introduction of plasmid-based short hairpin RNA (shRNA) expression vectors. Other small RNAs such as micro RNA (miRNA) also function in post-transcriptional gene regulation and are aberrantly expressed under disease conditions. The miRNA-based therapy involves either restoration of miRNA function through the introduction of miRNA mimics; or the inhibition of miRNA function by delivering anti-miRNA oligomers. However, the large size, hydrophilicity, negative charge and nuclease-sensitivity of nucleic acids necessitate an appropriate carrier for their introduction as medicine into cells.

CONCLUSION

While numerous organic and inorganic materials have been investigated for this purpose, the perfect carrier agent remains elusive. In recent years, carbon-based nanomaterials have received widespread attention in biotechnology due to their tunable surface characteristics, mechanical, electrical, optical and chemical properties.

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.

Development of Graphene-Based Materials in Bone Tissue Engineaering

Bone regeneration-related graphene-based materials (bGBMs) are increasingly attracting attention in tissue engineering due to their special physical and chemical properties. The purpose of this review is to quantitatively analyze mass academic literature in the field of bGBMs through scientometrics software CiteSpace, to demonstrate the rules and trends of bGBMs, thus to analyze and summarize the mechanisms behind the rules, and to provide clues for future research. First, the research status, hotspots, and frontiers of bGBMs are analyzed in an intuitively and vividly visualized way. Next, the extracted important subjects such as fabrication techniques, cytotoxicity, biodegradability, and osteoinductivity of bGBMs are presented, and the different mechanisms, in turn, are also discussed. Finally, photothermal therapy, which is considered an emerging area of application of bGBMs, is also presented. Based on this approach, this work finds that different studies report differing opinions on the biological properties of bGBMS due to the lack of consistency of GBMs preparation. Therefore, it is necessary to establish more standards in fabrication, characterization, and testing for bGBMs to further promote scientific progress and clinical translation.

Two-dimensional biomaterials: material science, biological effect and biomedical engineering applications

To date, nanotechnology has increasingly been identified as a promising and efficient means to address a number of challenges associated with public health. In the past decade, two-dimensional (2D) biomaterials, as a unique nanoplatform with planar topology, have attracted explosive interest in various fields such as biomedicine due to their unique morphology, physicochemical properties and biological effect. Motivated by the progress of graphene in biomedicine, dozens of types of ultrathin 2D biomaterials have found versatile bio-applications, including biosensing, biomedical imaging, delivery of therapeutic agents, cancer theranostics, tissue engineering, as well as others. The effective utilization of 2D biomaterials stems from the in-depth knowledge of structure-property-bioactivity-biosafety-application-performance relationships. A comprehensive summary of 2D biomaterials for biomedicine is still lacking. In this comprehensive review, we aim to concentrate on the state-of-the-art 2D biomaterials with a particular focus on their versatile biomedical applications. In particular, we discuss the design, fabrication and functionalization of 2D biomaterials used for diverse biomedical applications based on the up-to-date progress. Furthermore, the interactions between 2D biomaterials and biological systems on the spatial-temporal scale are highlighted, which will deepen the understanding of the underlying action mechanism of 2D biomaterials aiding their design with improved functionalities. Finally, taking the bench-to-bedside as a focus, we conclude this review by proposing the current crucial issues/challenges and presenting the future development directions to advance the clinical translation of these emerging 2D biomaterials.

The impact of graphene oxide sheet lateral dimensions on their pharmacokinetic and tissue distribution profiles in mice

Although the use of graphene and 2-dimensional (2D) materials in biomedicine has been explored for over a decade now, there are still significant knowledge gaps regarding the fate of these materials upon interaction with living systems. Here, the pharmacokinetic profile of graphene oxide (GO) sheets of three different lateral dimensions was studied. The GO materials were functionalized with a PEGylated DOTA (1,4,7,10-tetraazacyclododecane-1,4,7,10-tetraacetic acid), a radiometal chelating agent for radioisotope attachment for single photon emission computed tomography (SPECT/CT) imaging. Our results revealed that GO materials with three distinct size distributions, large (l-GO-DOTA), small (s-GO-DOTA) and ultra-small (us-GO-DOTA), were sequestered by the spleen and liver. Significant accumulation of the large material (l-GO-DOTA) in the lungs was also observed, unlike the other two materials. Interestingly, there was extensive urinary excretion of all three GO nanomaterials indicating that urinary excretion of these structures was not affected by lateral dimensions. Comparing with previous studies, we believe that the thickness of layered nanomaterials is the predominant factor that governs their excretion rather than lateral size. However, the rate of urinary excretion was affected by lateral size, with large GO excreting at slower rates. This study provides better understanding of 2D materials in vivo behaviour with varying structural features.

Efficacy of graphene oxide-loaded cationic antimicrobial peptide AWRK6 on the neutralization of endotoxin activity and in the treatment of sepsis

Objective: This study is to assess the therapeutic effect of graphene oxide (GO) loaded with AWRK6 on endotoxin-induced sepsis.

Method: AWRK6/GO was prepared by GO loaded AWRK6, with the structure characterization of AWRK6/GO conducted by atomic force microscope (AFM) and ultraviolet spectrophotometer, the sustained release rate of AWRK6/GO detected by high performance liquid chromatography (HPLC), and the neutralization ability of AWRK6/GO to lipopolysaccharide (LPS) tested by in vitro experiments. The levels of IL-8 and TNF-α in mouse cells after drug intervention were detected by ELISA; a LPS mouse model was established to observe the effects of drug intervention on the survival cycle and survival rate of mice.

Results: The sustained drug release rate of AWRK6/GO reached 85% within 24 hours observed under in vitro conditions, with an efficient neutralization effect to LPS (P < 0.01); Compared with the control group, the intervention of LPS succeeded in remarkably elevating the levels of IL-8 and TNF-α in the whole blood and macrophages of the mice (P < 0.01), whose survival cycle and survival rate consequently observed an obvious decline (P < 0.01); The intervention with AWRK6 or AWRK6/GO predominantly brought down the levels of IL-8 and TNF-α in the whole blood and macrophages of mice given LPS (P < 0.01), resulting in an elevation of the survival rate and survival time (P < 0.01).

Conclusion: GO loaded with cationic antimicrobial peptide AWRK6 exerts a rosy neutralization effect on endotoxin activity, with no obvious side effects on mice observed, which is of certain application value in the treatment of sepsis.

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.

Carbon-based nanomaterials for targeted cancer nanotherapy: recent trends and future prospects

Carbon-based nanomaterials are becoming attractive materials due to their unique structural dimensions and promising mechanical, electrical, thermal, optical and chemical characteristics. Carbon nanotubes, graphene, graphene oxide, carbon and graphene quantum dots have numerous applications in diverse areas, including biosensing, drug/gene delivery, tissue engineering, imaging, regenerative medicine, diagnosis, and cancer therapy. Cancer remains one of the major health problems all over the world, and several therapeutic approaches are focussed on designing targeted anticancer drug delivery nanosystems by applying benign and less hazardous resources with high biocompatibility, ease of functionalization, remarkable targeted therapy issues, and low adverse effects. This review highlights the recent development on these carbon based-nanomaterials in the field of targeted cancer therapy and discusses their possible and promising diagnostic and therapeutic applications for the treatment of cancers.

Mimicking the electrophysiological microenvironment of bone tissue using electroactive materials to promote its regeneration

The process of bone tissue repair and regeneration is complex and requires a variety of physiological signals, including biochemical, electrical and mechanical signals, which collaborate to ensure functional recovery. The inherent piezoelectric properties of bone tissues can convert mechanical stimulation into electrical effects, which play significant roles in bone maturation, remodeling and reconstruction. Electroactive materials, including conductive materials, piezoelectric materials and electret materials, can simulate the physiological and electrical microenvironment of bone tissue, thereby promoting bone regeneration and reconstruction. In this paper, the structures and performances of different types of electroactive materials and their applications in the field of bone repair and regeneration are reviewed, particularly by providing the results from in vivo evaluations using various animal models. Their advantages and disadvantages as bone repair materials are discussed, and the methods for tuning their performances are also described, with the aim of providing an up-to-date account of the proposed topics.

A Comprehensive Insight Towards Pharmaceutical Aspects of Graphene Nanosheets

Graphene Derivatives (GDs) have captured the interest and imagination of pharmaceutical scientists. This review exclusively provides pharmacokinetics and pharmacodynamics information with a particular focus on biopharmaceuticals. GDs can be used as multipurpose pharmaceutical delivery systems due to their ultra-high surface area, flexibility, and fast mobility of charge carriers. Improved effects, targeted delivery to tissues, controlled release profiles, visualization of biodistribution and clearance, and overcoming drug resistance are examples of the benefits of GDs. This review focuses on the application of GDs for the delivery of biopharmaceuticals. Also, the pharmacokinetic properties and the advantage of using GDs in pharmaceutics will be reviewed to achieve a comprehensive understanding about the GDs in pharmaceutical sciences.

Ciprofloxacin and Graphene Oxide Combination-New Face of a Known Drug

Drug modification with nanomaterials is a new trend in pharmaceutical studies and shows promising results, especially considering carbon-based solutions. Graphene and its derivatives have attracted much research interest for their potential applications in biomedical areas as drug modifiers. The following work is a comprehensive study regarding the toxicity of ciprofloxacin (CIP) modified by graphene oxide (GO). The influence on the morphology, viability, cell death pathway and proliferation of T24 and 786-0 cells was studied. The results show that ciprofloxacin modified with graphene oxide (CGO) shows the highest increase in cytotoxic potential, especially in the case of T24 cells. We discovered a clear connection between CIP modification with GO and the increase in its apoptotic potential. Our results show that drug modification with carbon-based nanomaterials might be a promising strategy to improve the qualities of existing drugs. Nevertheless, it is important to remember that cytotoxicity effects are highly dependent on dose and nanomaterial size. It is necessary to conduct further research to determine the optimal dose of GO for drug modification.

Splenic Capture and In Vivo Intracellular Biodegradation of Biological-Grade Graphene Oxide Sheets

Carbon nanomaterials, including 2D graphene-based materials, have shown promising applicability to drug delivery, tissue engineering, diagnostics, and various other biomedical areas. However, to exploit the benefits of these materials in some of the areas mentioned, it is necessary to understand their possible toxicological implications and long-term fate in vivo. We previously demonstrated that following intravenous administration, 2D graphene oxide (GO) nanosheets were largely excreted via the kidneys; however, a small but significant portion of the material was sequestered in the spleen. Herein, we interrogate the potential consequences of this accumulation and the fate of the spleen-residing GO over a period of nine months. We show that our thoroughly characterized GO materials are not associated with any detectable pathological consequences in the spleen. Using confocal Raman mapping of tissue sections, we determine the sub-organ biodistribution of GO at various time points after administration. The cells largely responsible for taking up the material are confirmed using immunohistochemistry coupled with Raman spectroscopy, and transmission electron microscopy (TEM). This combination of techniques identified cells of the splenic marginal zone as the main site of GO bioaccumulation. In addition, through analyses using both bright-field TEM coupled with electron diffraction and Raman spectroscopy, we reveal direct evidence of in vivo intracellular biodegradation of GO sheets with ultrastructural precision. This work offers critical information about biological processing and degradation of thin GO sheets by normal mammalian tissue, indicating that further development and exploitation of GO in biomedicine would be possible.

Toxicity of Carbon Nanomaterials and Their Potential Application as Drug Delivery Systems: In Vitro Studies in Caco-2 and MCF-7 Cell Lines

Carbon nanomaterials have attracted increasing attention in biomedicine recently to be used as drug nanocarriers suitable for medical treatments, due to their large surface area, high cellular internalization and preferential tumor accumulation, that enable these nanomaterials to transport chemotherapeutic agents preferentially to tumor sites, thereby reducing drug toxic side effects. However, there are widespread concerns on the inherent cytotoxicity of carbon nanomaterials, which remains controversial to this day, with studies demonstrating conflicting results. We investigated here in vitro toxicity of various carbon nanomaterials in human epithelial colorectal adenocarcinoma (Caco-2) cells and human breast adenocarcinoma (MCF-7) cells. Carbon nanohorns (CNH), carbon nanotubes (CNT), carbon nanoplatelets (CNP), graphene oxide (GO), reduced graphene oxide (GO) and nanodiamonds (ND) were systematically compared, using Pluronic F-127 dispersant. Cell viability after carbon nanomaterial treatment followed the order CNP < CNH < RGO < CNT < GO < ND, being the effect more pronounced on the more rapidly dividing Caco-2 cells. CNP produced remarkably high reactive oxygen species (ROS) levels. Furthermore, the potential of these materials as nanocarriers in the field of drug delivery of doxorubicin and camptothecin anticancer drugs was also compared. In all cases the carbon nanomaterial/drug complexes resulted in improved anticancer activity compared to that of the free drug, being the efficiency largely dependent of the carbon nanomaterial hydrophobicity and surface chemistry. These fundamental studies are of paramount importance as screening and risk-to-benefit assessment towards the development of smart carbon nanomaterial-based nanocarriers.

Simple Universal Strategy for Quantification of Carboxyl Groups on Carbon Nanomaterials: Carbon Dioxide Vapor Generation Coupled to Microplasma for Optical Emission Spectrometric Detection

The physicochemical properties and applications of carbon nanomaterials are remarkably dependent on the amount of carboxyl group on their surfaces. Unfortunately, it is challenging to determine the carboxyl group on carbon nanomaterials at an ultralow density not only due to the low sensitivities of conventional techniques, but also because there are no matrix-matched certified reference materials available. In this work, a novel strategy comprising coupling carbon dioxide vapor generation to a microplasma optical emission spectrometer was developed for the sensitive and accurate quantification of surface carboxyl groups on carbon nanomaterials. The carboxyl group on multiwall carbon nanotubes (MWCNTs), graphene (G), or its oxide (GO) was converted to carboxylic acid using concentrated hydrochloric acid prior to quantification. The generated carboxylic acid was purified and then reacted with sodium bicarbonate to generate CO₂, which was swept into a miniaturized point discharge optical emission spectrometer (μPD-OES) for the detection of carbon atomic emission lines. Potassium hydrogen phthalate (KHP) served as a calibration standard for quantification of the carboxyl group on G/GO/MWCNTs, thus, overcoming the lack of CRMs. Owing to the high sensitivity of μPD-OES for the detection of CO₂, a limit of detection of 0.1 μmol g^-1 (1 nmol) was obtained for the carboxyl group based on a sample mass of 10 mg G/GO/MWCNTs, superior to that obtained using conventional methods. Moreover, the proposed method not only retains several unique advantages of good accuracy and elimination of the use of complicated, expensive, and high power-consumption instruments, but was also applicable to the quantification of the carboxyl group on other nanomaterials such as carboxylated magnetic microspheres.

Eco-friendly development of an ultrasmall IONP-loaded nanoplatform for bimodal imaging-guided cancer theranostics

Ultrasmall IONP-decorated graphene oxide (GO) nanohybrids present T₁/T₂ dual MRI imaging-guided photothermal-chemo combined anticancer theranostics efficacy.

Estimation of genomic instability and mutation induction by graphene oxide nanoparticles in mice liver and brain tissues

The rapidly growing interest in using graphene-based nanoparticles in a wide range of applications increases human exposure and risk. However, very few studies have investigated the genotoxicity and mutagenicity of the widely used graphene oxide (GO) nanoparticles in vivo. Consequently, this study estimated the possible genotoxicity and mutagenicity of GO nanoparticles as well as possible oxidative stress induction in the mice liver and brain tissues. Nano-GO particles administration at the dose levels of 10, 20, or 40 mg/kg for one or five consecutive days significantly increased the DNA breakages in a dose-dependent manner that disrupts the genetic material and causes genomic instability. GO nanoparticles also induced mutations in the p53 (exons 6&7) and presenilin (exon 5) genes as well as increasing the expression of p53 protein. Positive p53 reaction in the liver (hepatic parenchyma) and brain (cerebrum, cerebellum, and hippocampus) sections showed significant increase of p53 immunostaining. Additionally, induction of oxidative stress was proven by the significant dose-dependent increases in the malondialdehyde level and reductions in both the level of reduced glutathione and activity of glutathione peroxidase observed in GO nanoparticles administered groups. Acute and subacute oral administration of GO nanoparticles induced genomic instability and mutagenicity by induction of oxidative stress in the mice liver and brain tissues.

A Flexible Method for Covalent Double Functionalization of Graphene Oxide

A method for the double functionalization of graphene oxide (GO) under mild alkaline conditions has been developed. Two functional groups were covalently linked to GO in two steps: the first group was attached by an epoxide ring-opening reaction and the second, bearing an amine function, was covalently conjugated to benzoquinone attached to the GO. The doubly functionalized GO was characterized by several techniques, confirming the sequential covalent modification of the GO surface with two different functional groups. This method is straightforward and the reaction conditions are mild, allowing preservation of the structure and properties of GO. This strategy could be exploited to prepare multifunctional GO conjugates with potential applications in many fields ranging from materials science to biomedicine.

Induction of chromosomal and DNA damage and histological alterations by graphene oxide nanoparticles in Swiss mice

The unique physicochemical properties of graphene oxide (GO) nanoparticles increase their uses in a wide range of applications that increase their release into the environment, and thus human exposure. However, the in vivo clastogenicity and genotoxicity of GO nanoparticles have not been well investigated. The current study was, therefore, designed to investigate the possible induction of chromosomal and DNA damage by GO nanoparticles and their impact on the tissue architecture in mice. Oral administration of GO nanoparticles for one or five consecutive days at the three dose levels 10, 20 or 40 mg/kg significantly increased the micronuclei and DNA damage levels in a dose-dependent manner in mice bone marrow cells, as well as caused, histological lesions including apoptosis, necrosis, inflammations and cells degeneration in the mice liver and brain tissue sections compared to the normal control mice. Thus, we concluded that oral administration of GO nanoparticles induced chromosomal and DNA damage in a dose-dependent manner as well as histological injuries in both acute and subacute treatments.

Intravital microscopy reveals a novel mechanism of nanoparticles excretion in kidney

Developing nanocarriers that accumulate in targeted organs and are harmlessly eliminated still remains a big challenge. Nanoparticles (NP) biodistribution is governed by their size, composition, surface charge and coverage. The current thinking in bionanotechnology is that renal clearance is limited by glomerular basement membrane pore size (≈6 nm), although there is a growing evidence that NP exceeding the threshold can also be excreted with urine. Here we compare biodistribution of PEGylated 140 nm iron oxide cubes and clusters with a special focus on renal accumulation and excretion. Atomic emission spectroscopy, fluorescent microscopy and magnetic resonance imaging revealed rapid and transient accumulation of magnetic NP in kidney. Using intravital microscopy we tracked in real time NP translocation from peritubular capillaries to basal compartment of tubular cells and subsequent excretion to the lumen within 60 min after systemic administration. Transmission electron microscopy revealed persistence of intact full-sized NP in urine 2 h post injection. The results suggest that translocation through peritubular endothelium to tubular epithelial cells is an alternative mechanism of renal clearance enabling excretion of NP above glomerular cut-off size.

The biobehavior, biocompatibility and theranostic application of SPNS and Pd@Au nanoplates in rats and rabbits

On account of the fascinating surface plasmon resonance (SPR) properties, the ability of passively targeting tumors and remarkable biocompatibility, two-dimensional (2D) Pd-based nanomaterials have demonstrated wide application prospects in cancer theranostics. However, the used animal models for exploring the bioapplications and biosafety of 2D Pd-based nanomaterials were usually limited to mice. To further widen their biomedical applications and promote future clinical transformation, it is necessary to make a breakthrough in animal models. In this work, Sprague Dawley (SD) rats and New Zealand rabbits were used as the experimental animals and orthotopic liver tumors or subcutaneous tumors were induced in these animals. Taking ≈5 nm small Pd nanosheets (SPNS) and 30 nm Pd@Au nanoplates (Pd@Au) as the representative 2D Pd-based nanomaterials, we investigated their biobehaviors and biosafety in rat liver & subcutaneous tumor models and rabbit liver tumors. The results indicated that SPNS and Pd@Au could still effectively accumulate on the tumor sites of these bigger animal models by the enhanced permeability and retention (EPR) effect, and the accumulation effects were closely related to their sizes. Metabolism studies confirmed that SPNS could be excreted out of rats through urine. Moreover, based on the sufficient uptake by cancer cells and passive accumulation of SPNS and Pd@Au in subcutaneous tumors in rats, we performed photothermal therapy (PTT) in vitro and in vivo. Significant tumor growth inhibition illustrated that even though the animal model was dozens of times bigger than the mouse model, the 2D Pd-based nanomaterials satisfied the requirements of being an outstanding photothermal reagent. Finally, the hematological and histological examination results suggested that SPNS and Pd@Au had favorable biocompatibility in rats and rabbits at a given dose. We hope this work will drive the development of 2D Pd-based nanomaterials towards practical clinical applications and provide a guide for other theranostic nanoplatforms that will be applied in bigger animal tumor models in the future.

Graphene Oxide as an Optical Biosensing Platform: A Progress Report

A few years ago, crucial graphene oxide (GO) features such as the carbon/oxygen ratio, number of layers, and lateral size were scarcely investigated and, thus, their impact on the overall optical biosensing performance was almost unknown. Nowadays valuable insights about these features are well documented in the literature, whereas others remain controversial. Moreover, most of the biosensing systems based on GO were amenable to operating as colloidal suspensions. Currently, the literature reports conceptually new approaches obviating the need of GO colloidal suspensions, enabling the integration of GO onto a solid phase and leading to their application in new biosensing devices. Furthermore, most GO-based biosensing devices exploit photoluminescent signals. However, further progress is also achieved in powerful label-free optical techniques exploiting GO in biosensing, particularly using optical fibers, surface plasmon resonance, and surface enhanced Raman scattering. Herein, a critical overview on these topics is offered, highlighting the key role of the physicochemical properties of GO. New challenges and opportunities in this exciting field are also highlighted.

Efficient and stable radiolabeling of polycyclic aromatic hydrocarbon assemblies: in vivo imaging of diesel exhaust particulates in mice

As a robust radioanalytical method for tracking carbonaceous particulates in vivo, polycyclic aromatic hydrocarbons from diesel exhaust were labeled with a radioactive-iodine-tagged pyrene analogue.

Safety Assessment of Graphene-Based Materials: Focus on Human Health and the Environment

Graphene and its derivatives are heralded as "miracle" materials with manifold applications in different sectors of society from electronics to energy storage to medicine. The increasing exploitation of graphene-based materials (GBMs) necessitates a comprehensive evaluation of the potential impact of these materials on human health and the environment. Here, we discuss synthesis and characterization of GBMs as well as human and environmental hazard assessment of GBMs using in vitro and in vivo model systems with the aim to understand the properties that underlie the biological effects of these materials; not all GBMs are alike, and it is essential that we disentangle the structure-activity relationships for this class of materials.

Functional Imaging with Nucleic-Acid-Based Sensors: Technology, Application and Future Healthcare Prospects

Timely monitoring and assessment of human health plays a crucial role in maintaining the wellbeing of our advancing society. In addition to medical tools and devices, suitable probe agents are crucial to assist such monitoring, either in passive or active ways (i.e., sensors) through inducible signals. In this review we highlight recent developments in activatable optical sensors based on nucleic acids. Sensing mechanisms and bio-applications of these nucleic acid sensors in ex vivo assays, intracellular or in vivo settings are described. In addition, we discuss the limitations of these sensors and how nanotechnology can complement/enhance sensor properties to promote translation into clinical applications.

Self-assembled, bivalent aptamers on graphene oxide as an efficient anticoagulant

Graphene oxide (GO) has unique structural properties, can effectively adsorb single-strand DNA through π-π stacking, hydrogen bonding and hydrophobic interactions, and is useful in many biotechnology applications. In this study, we developed a thrombin-binding-aptamers (15- and 29-mer) conjugated graphene oxide (TBA15/TBA29-GO) composite for the efficient inhibition of thrombin activity towards the formation of fibrin from fibrinogen. The TBA15/TBA29-GO composite was simply obtained by the self-assembly of TBA15/TBA29 hybrids on GO. The high density and appropriate orientation of TBA15/TBA29 on the GO surface enabled TBA15/TBA29-GO to acquire an ultrastrong binding affinity for thrombin (dissociation constant = 2.9 × 10-12 M). Compared to bivalent TBA15h20A20/TBA29h20A20 hybrids, the TBA15/TBA29-GO composite exhibited a superior anticoagulant potency (ca. 10-fold) against thrombin-mediated coagulation as a result of steric blocking effects and a higher binding affinity for thrombin. In addition, the prolonged thrombin clotting time, prothrombin time (PT), and activated partial thromboplastin time (aPTT) of TBA15/TBA29-GO were at least 2 times longer than those of commercially available drugs (heparin, argatroban, hirudin, and warfarin). The in vitro cytotoxicity and hemolysis analyses revealed the high biocompatibility of TBA15/TBA29-GO. The rat-tail bleeding assay of the hemostasis time and ex vivo PT and aPTT further revealed that TBA15/TBA29-GO is superior (>2-fold) to heparin, which is commonly used in the treatment and prevention of thrombotic diseases. Our multivalent, oligonucleotide-modified GO nanocomposites are easy to prepare, cost-effective, and highly biocompatible and they show great potential as effective anticoagulants for the treatment of thrombotic disorders.

Immunological impact of graphene oxide sheets in the abdominal cavity is governed by surface reactivity

Graphene oxide (GO) is an oxidised form of graphene that has attracted commercial interest in multiple applications, including inks, printed electronics and spray coatings, which all raise health concerns due to potential creation of inhalable aerosols. Although a number of studies have discussed the toxicity of GO sheets, the in vivo impact of their lateral dimensions is still not clear. Here, we compared the effects of large GO sheets (l-GO, 1–20 µm) with those of small GO sheets (s-GO, < 1 µm) in terms of mesothelial damage and peritoneal inflammation, after intraperitoneal (i.p.) injection in mice. To benchmark the outcomes, long and rigid multi-walled carbon nanotubes (MWCNTs) that were shown to be associated with asbestos-like pathogenicity on the mesothelium were also tested. Our aim was to assess whether lateral dimensions can be a predictor of inflammogenicity for GO sheets in a similar fashion as length is for MWCNTs. While long MWCNTs dispersed in 0.5% BSA induced a granulomatous response on the diaphragmatic mesothelium and immune cell recruitment to the peritoneal cavity, GO sheets dispersed under similar conditions did not cause any response, regardless of their lateral dimensions. We further interrogated whether tuning the surface reactivity of GO by testing different dispersions (5% dextrose instead of 0.5% BSA) may change the biological outcome. Although the change of dispersion did not alter the impact of GO on the mesothelium (i.e. no granuloma), we observed that, when dispersed in protein-free 5% dextrose solution, s-GO elicited a greater recruitment of monocytic cells to the peritoneal cavity than l-GO, or when dispersed in protein-containing solution. Such recruitment coincided with the greater ability of s-GO to interact in vivo with peritoneal macrophages and was associated with a greater surface reactivity in comparison to l-GO. In conclusion, large dimension was not a determining factor of the immunological impact of GO sheets after i.p. administration. For an equal dose, GO sheets with lateral dimensions similar to the length of long MWCNTs were less pathogenic than the MWCNTs. On the other hand, surface reactivity and the ability of some smaller GO sheets to interact more readily with immune cells seem to be key parameters that can be tuned to improve the safety profile of GO. In particular, the choice of dispersion modality, which affected these two parameters, was found to be of crucial importance in the assessment of GO impact in this model. Overall, these findings are essential for a better understanding of the parameters governing GO toxicity and inflammation, and the rational design of safe GO-based formulations for various applications, including biomedicine.

In vivo toxicological evaluation of graphene oxide nanoplatelets for clinical application

Background

Graphene is considered as a wonder material; it is the strongest material on the planet, super-elastic, and conductive. Its application in biomedicine is huge, with a multibillion-dollar industry, and will revolutionize the diagnostic and treatment of diseases. However, its safety and potential toxicity is the main challenge.

Methods

This study assessed the potential toxicity of graphene oxide nanoplatelets (GONs) in an in vivo animal model using systemic, hematological, biochemical, and histopathological examinations. Normal saline (control group) or GONs (3–6 layers, lateral dimension=5–10 μm, and thickness=0.8–2 nm) at dose rate of 50, 150, or 500 mg/kg were intraperitoneally injected into adult male Wistar rats (n=5) every 48 hours during 1 week to receive each animal a total of four doses. The animals were allowed 2 weeks to recover after the last dosing. Then, animals were killed and the blood was collected for hematological and biochemical analysis. The organs including the liver, kidney, spleen, lung, intestine, brain, and heart were harvested for histopathological evaluations.

Results

The results showed GONs prevented body weight gain in animals after 21 days, treated at 500 mg/kg, but not in the animals treated at 150 or 50 mg/kg GONs. The biochemical analysis showed a significant increase in total bilirubin, with a significant decrease in triglycerides and high-density lipoprotein in animals treated at 500 mg/kg. Nonetheless, other hematological and biochemical parameters remained statistically insignificant in all GONs treated animals. The most common histopathological findings in the visceral organs were granulomatous reaction with giant cell formation and accumulation of GONs in capsular regions. Also, small foci of neuronal degeneration and necrosis were the most outstanding findings in the brain, including the cerebellum.

Conclusion

In conclusion, this study shows that GONs without functionalization are toxic. The future study is a comparison of the functionalized with non-functionalized GONs.

Functionalization of graphene: does the organic chemistry matter?

Reactions applying amidation- or esterification-type processes and diazonium salts chemistry constitute the most commonly applied synthetic approaches for the modification of graphene-family materials. This work presents a critical assessment of the amidation and esterification methodologies reported in the recent literature, as well as a discussion of the reactions that apply diazonium salts. Common misunderstandings from the reported covalent functionalization methods are discussed, and a direct link between the reaction mechanisms and the basic principles of organic chemistry is taken into special consideration.

Nanocolloids in Natural Water: Isolation, Characterization, and Toxicity

Nanocolloids are widespread in natural water systems, but their characterization and ecological risks are largely unknown. Herein, tangential flow ultrafiltration (TFU) was used to separate and concentrate nanocolloids from surface waters. Unexpectedly, nanocolloids were present in high concentrations ranging from 3.7 to 7.2 mg/L in the surface waters of the Harihe River in Tianjin City, China. Most of the nanocolloids were 10-40 nm in size, contained various trace metals and polycyclic aromatic hydrocarbons, and exhibited fluorescence properties. Envelopment effects and aggregation of Chlorella vulgaris in the presence of nanocolloids were observed. Nanocolloids entered cells and nanocolloid-exposed cells exhibited stronger plasmolysis, chloroplast damage and more starch grains than the control cells. Moreover, nanocolloids inhibited the cell growth, promoted reactive oxygen species (ROS), reduce the chlorophyll a content and increased the cell permeability. The genotoxicity of nanocolloids was also observed. The metabolomics analysis revealed a significant ( p < 0.05) downregulation of amino acids and upregulation of fatty acids contributing to ROS increase, chlorophyll a decrease and plasmolysis. The present work reveals that nanocolloids, which are different from specific, engineered nanoparticles (e.g., Ag nanoparticles), are present at high concentrations, exhibit an obvious toxicity in environments, and deserve more attention in the future.

Ultrathin Polypyrrole Nanosheets via Space-Confined Synthesis for Efficient Photothermal Therapy in the Second Near-Infrared Window

Extensive efforts have been devoted to synthesizing photothermal agents (PTAs) that are active in the first near-infrared (NIR) region (650-950 nm). However, PTAs for photothermal therapy in the second NIR window (1000-1350 nm) are still rare. Here, it is shown that two-dimensional ultrathin polypyrrole (PPy) nanosheets prepared via a novel space-confined synthesis method could exhibit unique broadband absorption with a large extinction coefficient of 27.8 L g^-1 cm^-1 at 1064 nm and can be used as an efficient PTA in the second NIR window. This unique optical property is attributed to the formation of bipolaron bands in highly doped PPy nanosheets. The measured prominent photothermal conversion efficiency could achieve 64.6%, surpassing previous PTAs that are active in the second NIR window. Both in vitro and in vivo studies reveal that these ultrathin PPy nanosheets possess good biocompatibility and notable tumor ablation ability in the second NIR window. Our study highlights the potential of ultrathin two-dimensional polymers with unique optical properties in biomedical applications.

Promises, facts and challenges for graphene in biomedical applications

The graphene family has captured the interest and the imagination of an increasing number of scientists working in different fields, ranging from composites to flexible electronics. In the area of biomedical applications, graphene is especially involved in drug delivery, biosensing and tissue engineering, with strong contributions to the whole nanomedicine area. Besides the interesting results obtained so far and the evident success, there are still many problems to solve, on the way to the manufacturing of biomedical devices, including the lack of standardization in the production of the graphene family members. Control of lateral size, aggregation state (single vs. few layers) and oxidation state (unmodified graphene vs. oxidized graphenes) is essential for the translation of this material into clinical assays. In this Tutorial Review we critically describe the latest developments of the graphene family materials into the biomedical field. We analyze graphene-based devices starting from graphene synthetic strategies, functionalization and processibility protocols up to the final in vitro and in vivo applications. We also address the toxicological impact and the limitations in translating graphene materials into advanced clinical tools. Finally, new trends and guidelines for future developments are presented.

Graphene oxide regulates cox2 in human embryonic kidney 293T cells via epigenetic mechanisms: dynamic chromosomal interactions

To extend the applications of engineered nanomaterials, such as graphene oxide (GO), it is necessary to minimize cytotoxicity. However, the mechanisms underlying this cytotoxicity are unclear. Dynamic chromosomal interactions have been used to illustrate the molecular bases of gene expression, which offers a more sensitive and cutting-edge technology to elucidate complex biological processes associated with epigenetic regulations. In this study, the role of GO-triggered chromatin interactions in the activation of cox2, a hallmark of inflammation, was investigated in normal human cells. Using chromosome conformation capture technology, we showed that GO triggers physical interactions between the downstream enhancer and the cox2 promoter in human embryonic kidney 293T (293T) via p65 and p300 complex-mediated dynamic chromatin looping, which was required for high cox2 expression. Moreover, tumor necrosis factor-α (TNF-α), located upstream of the p65 signaling pathway, contributed to the regulation of cox2 activation through dynamic chromatin architecture. Compared with pristine GO and aminated GO (GO-NH₂), poly (acrylic acid)-functionalized GO (GO-PAA) induced a weaker inflammatory response and a weaker effect on chromatin architecture. Our results mechanistically link GO-mediated chromatin interactions with the regulation of cox2 and suggest that GO derivatives may minimize toxicity in practical applications.

Functionalized graphene sheets for intracellular controlled release of therapeutic agents

Since therapeutic agents target specific compartments inside the cells, their efficiency depends on their intracellular release from drug delivery systems (DDS). However, control over the intracellular release of therapeutic agents is a challenging issue and can only be achieved by governing their interactions with the DDS. In this work, polyglycerol amine- and polyglycerol sulfate-functionalized graphene sheets as positively and negatively charged 2D nanomaterials with 150 nm lateral size were used to deliver and control the release of doxorubicin (DOX) inside cells. A pH-sensitive dye was conjugated onto the surfaces of graphene sheets and used as an antenna to obtain specific signals from the acidic cell compartments. It was found that both positively and negatively charged graphene sheets undergo similar acidification processes after cellular uptake. Nevertheless, the intracellular drug release of these DOX-loaded nanomaterials was distinctly different. As an overall effect of the π-π stacking and electrostatic interactions, the release of DOX from the positively charged graphene sheets was much faster than that from their analogs with a negative surface charge. Therefore, therapeutic efficiency in the first case was much higher than that in the latter. Based on our findings, the intracellular release of drugs from the surfaces of graphene sheets can be finely tuned by manipulating their functionalities, which is of great importance in the designing of the future graphene-based nanomedicines.

Characterisation of Peptide5 systemic administration for treating traumatic spinal cord injured rats

Systemic administration of a Connexin43 mimetic peptide, Peptide5, has been shown to reduce secondary tissue damage and improve functional recovery after spinal cord injury (SCI). This study investigated safety measures and potential off-target effects of Peptide5 systemic administration. Rats were subjected to a mild contusion SCI using the New York University impactor. One cohort was injected intraperitoneally with a single dose of fluorescently labelled Peptide5 and euthanised at 2 or 4 h post-injury for peptide distribution analysis. A second cohort received intraperitoneal injections of Peptide5 or a scrambled peptide and was culled at 8 or 24 h post-injury for the analysis of connexin proteins and systemic cytokine profile. We found that Peptide5 did not cross the blood-spinal cord barrier in control animals, but reached the lesion area in the spinal cord-injured animals without entering non-injured tissue. There was no evidence that the systemic administration of Peptide5 modulates Connexin43 protein expression or hemichannel closure in the heart and lung tissue of SCI animals. The expression levels of other major connexin proteins including Connexin30 in astrocytes, Connexin36 in neurons and Connexin47 in oligodendrocytes were also unaltered by systemic delivery of Peptide5 in either the injured or non-injured spinal cords. In addition, systemic delivery of Peptide5 had no significant effect on the plasma levels of cytokines, chemokines or growth factors. These data indicate that the systemic delivery of Peptide5 is unlikely to cause any off-target or adverse effects and may thus be a safe treatment option for traumatic SCI.