Nanotoxicity of Graphene and Graphene Oxide

Doxorubicin/Cisplatin-Loaded Superparamagnetic Nanoparticles As A Stimuli-Responsive Co-Delivery System For Chemo-Photothermal Therapy

INTRODUCTION

To date, numerous iron-based nanostructures have been designed for cancer therapy applications. Although some of them were promising for clinical applications, few efforts have been made to maximize the therapeutic index of these carriers. Herein, PEGylated silica-coated iron oxide nanoparticles (PS-IONs) were introduced as multipurpose stimuli-responsive co-delivery nanocarriers for a combination of dual-drug chemotherapy and photothermal therapy.

METHODS

Superparamagnetic iron oxide nanoparticles were synthesized via the sonochemical method and coated by a thin layer of silica. The nanostructures were then further modified with a layer of di-carboxylate polyethylene glycol (6 kDa) and carboxylate-methoxy polyethylene glycol (6 kDa) to improve their stability, biocompatibility, and drug loading capability. Doxorubicin (DOX) and cisplatin (CDDP) were loaded on the PS-IONs through the interactions between the drug molecules and polyethylene glycol.

RESULTS

The PS-IONs demonstrated excellent cellular uptake, cytocompatibility, and hemocompatibility at the practical dosage. Furthermore, in addition to being an appropriate MRI agent, PS-IONs demonstrated superb photothermal property in 0.5 W/cm2 of 808 nm laser irradiation. The release of both drugs was effectively triggered by pH and NIR irradiation. As a result of the intracellular combination chemotherapy and 10 min of safe power laser irradiation, the highest cytotoxicity for iron-based nanocarriers (97.3±0.8%) was achieved.

CONCLUSION

The results of this study indicate the great potential of PS-IONs as a multifunctional targeted co-delivery system for cancer theranostic application and the advantage of employing proper combination therapy for cancer eradication.

Sonochemically N-functionalized graphene oxide towards optically active photoluminescent bioscaffold

Herein, Nitrogen functionalized graphene oxide (N-f-GrO) has been synthesized using the sonochemical method. 2-Aminopyrimidine (APD) was used as a precursor for covalent functionalization with graphene oxide [f-(APD)GrO] as N-f-GrO which was ascertained with XPS. The involvement of arylamine group and formation of covalent bond over GrO surface was confirmed with high resolution C1s spectrum of f-(APD)GrO. Also, the signature of N1s peak in the survey spectrum of f-(APD)GrO has endorsed the surface modification of GrO through covalent functionalization. A bathochromic shift was observed for f-(APD)GrO in UV and enhanced weight loss of 91.39% at 191.80 °C, confirms a facile functionalization of GrO via formation of amide bond, where the terminal -OH portal of carboxylic group is substituted by 2-Aminopyrimidine. Moreover, the formation of f-(APD)GrO was investigated with various analytical techniques like Raman, XRD and FTIR. The surface morphology and topography have been understood by using HRTEM/SAED, AFM, and SEM analysis. The synthesized f-(APD)GrO shows potential optically active photoluminescence properties and higher potency towards biological insight. The identified photoluminescence (PL) peaks at 3.78, 3.21 2.01 and 1.64 eV indicate photon emission including an orange optical transition at 2.01 eV. The multiple peaks in a PL spectrum are due to radiative and non-radiative recombinations which are also associated with excess hole (h⁺)-electron (e^-) trapping on the surface to restrict the recombinations of e^- and h⁺. The biological activity of N-f-GrO has been explored with Sulforhodamine B (SRB) assay on HaCaT and Vero cell lines. The concentration-dependent cell viabilities have been observed a maximum at 20 µg/ml for HaCaT and at 10 µg/ml for Vero cell lines at testing concentration range of 10-80 μg mL^-1. The significant morphological impact on cell lines confirms the cytocompatibility behaviour. Therefore, the synergistic impact of various properties of f-(APD)GrO can be further explored to study its significance as nanocarrier for photosensitive biomedical response.

Enhanced Osseointegration of Titanium Alloy Implants with Laser Microgrooved Surfaces and Graphene Oxide Coating

Rapid and effective osseointegration, as a critical factor in affecting the success rate of titanium (Ti) implants in orthopedic applications, is significantly affected by their surface microstructure and chemical composition. In this work, surface microgrooved Ti-6Al-4V alloys with graphene oxide coating (Ti-G-GO) were fabricated by a combination of laser processing and chemical assembly techniques. The osteogenic capability in vitro and new bone formation in vivo of the implants were systematically investigated, and biomechanical pull-out tests of the screws were also performed. First, in vitro studies indicated that the optimal microgroove width of the titanium alloy surface was 45 μm (Ti-G), and the optimum GO concentration was 1 mg/mL. Furthermore, the effects of the surface microstructure and GO coating on the in vitro bioactivity were investigated through culturing bone marrow mesenchymal stem cells (BMSCs) on the surface of titanium alloy plates. The results showed that the BMSCs cultured on the Ti-G-GO group exhibited the best adhesion, proliferation, and differentiation, compared with that on the Ti-G and Ti groups. Micro-computed tomography evaluation, histological analysis, and pull-out testing demonstrated that both Ti-G and Ti-G-GO implants had the higher osseointegration than the untreated Ti implant. Moreover, the osteogenic capability of the Ti-G-GO group appeared to be superior to that of the Ti-G group, which could be attributed to the improvement of surface wettability and apatite formation by the GO coatings. These results suggest that the combination of the microgroove structure and GO coatings exhibits considerable potential for enhancing the surface bioactivation of materials, and the combination modification is expected to be used on engineered titanium alloy surfaces to enhance osseointegration for orthopedic applications.

Understanding the Synergic Mechanism of Weak Interactions between Graphene Oxide and Lipid Membrane Leading to the Extraction of Lipids

Revealing how weak forces interact synergistically to induce differences in nanobio effects is critical to understanding the nature of the nanobio interface. Herein, graphene oxide (GO) and a lipid membrane are selected as a nanobio model, and interaction forces at the GO-biomembrane interface are modulated by varying the amounts and species of oxygenated functional groups on the surface of GO. A synergic mechanism of interfacial interaction forces is investigated by a combination of surface-enhanced infrared absorption (SEIRA) spectroscopy, confocal laser scanning microscopy (CLSM), and electrochemical impedance spectroscopy (EIS). The results reveal that after balancing with electrostatic repulsion, the moderate attraction between GO and lipid headgroups (such as electrostatic and/or hydrophobic interactions) is most favorable for lipid extraction, whereas lipid extraction is inhibited under an attraction that is too strong or too weak. Under moderate attraction between GO and the headgroups of lipids, the appropriate degree of rotation freedom is maintained for GO, which is beneficial to the hydrogen-bonding interaction between the C═O group in the phosphatide hydrophobic region and GO, thus triggering the insertion of GO into the lipid alkyl chain region, resulting in the rapid and significant extraction of lipids. Our results have important guiding significance for how to reveal the synergistic mechanism of weak interactions at the nanobio interface.

Graphene oxide effects in early ontogenetic stages of Triticum aestivum L. seedlings

Nanomaterials are being used increasingly in various areas such as electronic devices manufacture, medicine, mechanical devices production, and even food industry. Therefore, the evaluation of their toxicity is mandatory. Graphene oxide (GO) has been shown to have both positive as well as negative impact on different crop plants, depending on species, dose, and duration of exposure. The current study evaluated the impact of GO sheets at different concentrations (500, 1000 and 2000 mg/L) on physiological, biochemical and genetic levels to determine the possible toxic action. Wheat caryopses were treated with GO for 48 h and 7 days. The germination rate and roots elongation decreased in a dose-response manner, except the sample treated with GO at a concentration of 1000 mg/L. Mitotic index has ascendant trend; its increase may be due to the accumulation of prophases GO induced significant accumulation of the cells with aberrations, their presence suggests a clastogenic/aneugenic effect of these carbon nanomaterials. Regarding enzymatic and non-enzymatic antioxidant system defence, the activity varied depending on the dose of GO. Thus, chlorophyll a pigments content decreased significantly at high dose (2000 mg/L), while the carotenoid pigments had lower content at 500 mg/L of GO, and no statistical difference encountered in case of chlorophyll b amount. The antioxidant enzyme activity (CAT, POD, and SOD) was higher at low dose of GO, indicating the presence of oxidative stress generated as a response to the GO treatment. Also, the free radical scavenging activity of the polyphenolic compounds was enhanced upon GO exposure. The GO accumulation has been identified by transmission electron microscopy only at plumules level, near the intercellular space.

Medium-Dependent Antibacterial Properties and Bacterial Filtration Ability of Reduced Graphene Oxide

Toxicity of reduced graphene oxide (rGO) has been a topic of multiple studies and was shown to depend on a variety of characteristics of rGO and biological objects of interest. In this paper, we demonstrate that when studying the same dispersions of rGO and fluorescent Escherichia coli (E. coli) bacteria, the outcome of nanotoxicity experiments also depends on the type of culture medium. We show that rGO inhibits the growth of bacteria in a nutrition medium but shows little effect on the behavior of E. coli in a physiological saline solution. The observed effects of rGO on E. coli in different media could be at least partially rationalized through the adsorption of bacteria and nutrients on the dispersed rGO sheets, which is likely mediated via hydrogen bonding. We also found that the interaction between rGO and E. coli is medium-dependent, and in physiological saline solutions they form stable flocculate structures that were not observed in nutrition media. Furthermore, the aggregation of rGO and E. coli in saline media was observed regardless of whether the bacteria were alive or dead. Filtration of the aggregate suspensions led to nearly complete removal of bacteria from filtered liquids, which highlights the potential of rGO for the filtration and separation of biological contaminants, regardless of whether they include live or dead microorganisms.

High Amplification of the Antiviral Activity of Curcumin through Transformation into Carbon Quantum Dots

It is demonstrated that carbon quantum dots derived from curcumin (Cur-CQDs) through one-step dry heating are effective antiviral agents against enterovirus 71 (EV71). The surface properties of Cur-CQDs, as well as their antiviral activity, are highly dependent on the heating temperature during synthesis. The one-step heating of curcumin at 180 °C preserves many of the moieties of polymeric curcumin on the surfaces of the as-synthesized Cur-CQDs, resulting in superior antiviral characteristics. It is proposed that curcumin undergoes a series of structural changes through dehydration, polymerization, and carbonization to form core-shell CQDs whose surfaces remain a pyrolytic curcumin-like polymer, boosting the antiviral activity. The results reveal that curcumin possesses insignificant inhibitory activity against EV71 infection in RD cells [half-maximal effective concentration (EC₅₀ ) >200 µg mL^-1 ] but exhibits high cytotoxicity toward RD cells (half-maximal cytotoxic concentration (CC₅₀ ) <13 µg mL^-1 ). The EC₅₀ (0.2 µg mL^-1 ) and CC₅₀ (452.2 µg mL^-1 ) of Cur-CQDs are >1000-fold lower and >34-fold higher, respectively, than those of curcumin, demonstrating their far superior antiviral capabilities and high biocompatibility. In vivo, intraperitoneal administration of Cur-CQDs significantly decreases mortality and provides protection against virus-induced hind-limb paralysis in new-born mice challenged with a lethal dose of EV71.

Preparation of graphene oxide-graphene quantum dots hybrid and its application in cancer theranostics

Currently, an enormous amount of cancer research based on two-dimensional nano-graphene oxide (GO), as well as zero-dimensional graphene quantum dots (GQDs), is being carried out in the fields of therapeutics and diagnostics. However, the exploration of their hybrid "functional" nanomaterials in the theranostic system is still rare. In the current study, a stable complex of GO and GQDs was formed by an electrostatic layer-by-layer assembly via a polyethylene imine bridge (GO-PEI-GQDs). Furthermore, we compared separate mono-equivalents of the GO-PEI-GQDs complex - GO and GQDs, in terms of cell imaging (diagnostics), photothermal, and oxidative stress response in breast cancer cells (MDA-MB-231). GO-PEI-GQDs showed an excellent photothermal response (44-49 °C) upon 808 nm laser (0.5 W cm^-2) exposure for 5 min at a concentration up to 50 μg/mL. We report new synergistic properties of GO-PEI-GQDs such as stable fluorescence imaging and enhanced photothermal and cytotoxic activities on cancer cells. Composite materials made up of GO and GQDs combining diverse properties help to study 2D-0D heterosystems and improve specific therapeutic systems in theranostics.

Two-Dimensional Materials in Biosensing and Healthcare: From In Vitro Diagnostics to Optogenetics and Beyond

Since the isolation of graphene in 2004, there has been an exponentially growing number of reports on layered two-dimensional (2D) materials for applications ranging from protective coatings to biochemical sensing. Due to the exceptional, and often tunable, electrical, optical, electrochemical, and physical properties of these materials, they can serve as the active sensing element or a supporting substrate for diverse healthcare applications. In this review, we provide a survey of the recent reports on the applications of 2D materials in biosensing and other emerging healthcare areas, ranging from wearable technologies to optogenetics to neural interfacing. Specifically, this review provides (i) a holistic evaluation of relevant material properties across a wide range of 2D systems, (ii) a comparison of 2D material-based biosensors to the state-of-the-art, (iii) relevant material synthesis approaches specifically reported for healthcare applications, and (iv) the technological considerations to facilitate mass production and commercialization.

Viability of Neural Cells on 3D Printed Graphene Bioelectronics

Parkinson's disease (PD) is the second most common neurodegenerative disease in the United States after Alzheimer's disease (AD). To help understand the electrophysiology of these diseases, N27 neuronal cells have been used as an in vitro model. In this study, a flexible graphene-based biosensor design is presented. Biocompatible graphene was manufactured using a liquid-phase exfoliation method and bovine serum albumin (BSA) for further exfoliation. Raman spectroscopy results indicated that the graphene produced was indeed few-layer graphene (FLG) with ID/IGGraphene= 0.11. Inkjet printing of this few-layer graphene ink onto Kapton polyimide (PI) followed by characterization via scanning electron microscopy (SEM) showed an average width of ≈868 µm with a normal thickness of ≈5.20 µm. Neuronal cells were placed on a thermally annealed 3D printed graphene chip. A live-dead cell assay was performed to prove the biosensor biocompatibility. A cell viability of approximately 80% was observed over 96 h, which indicates that annealed graphene on Kapton PI substrate could be used as a neuronal cell biosensor. This research will help us move forward with the study of N27 cell electrophysiology and electrical signaling.

Ag and Au nanoparticles/reduced graphene oxide composite materials: Synthesis and application in diagnostics and therapeutics

The exceptional electrical, thermal, optical and mechanical properties have made two dimensional sp² hybridized graphene a material of choice in both academic as well as industrial research. In the last few years, researchers have devoted their efforts towards the development of graphene/polymer, graphene/metal nanoparticle and graphene/ceramic nanocomposites. These materials display excellent mechanical, electrical, thermal, catalytic, magnetic and optical properties which cannot be obtained separately from the individual components. Fascinating physical and chemical properties are displayed by noble metal nanomaterials and thus they represent model building blocks for modifying nanoscale structures for diverse applications extending from catalysis, optics to nanomedicine. Insertion of noble metal (Au, Ag) nanoparticles (NPs) into chemically derived graphene is thus of primary importance to open new avenues for both materials in various fields where the specific properties of each material act synergistically to provide hybrid materials with exceptional performances. This review attempts to summarize the different synthetic procedures for the preparation of Ag and Au NPs/reduced graphene oxide (rGO) composites. The synthesis processes of metal NPs/rGO composites are categorised into in-situ and ex-situ techniques. The in-situ approach consists of simultaneous reduction of metal salts and GO to obtain metal NPs/rGO nanocomposite materials, while in the ex-situ process, the metal NPs of desired size and shape are first synthesized and then transferred onto the GO or rGO matrix. The application of the Ag NPs and Au NPs/rGO composite materials in the area of biomedical (drug delivery and photothermal therapy) and biosensing are the focus of this review article.

How do proteins 'response' to common carbon nanomaterials?

Carbon nanomaterials are widely produced and applied in biological and environmental fields because of their outstanding physical and chemical properties, which pose a threat to the safety of living organisms and the ecological environment. Therefore, understanding how carbon nanomaterials and their derivatives work on organisms is becoming important. In recent years, more and more researchers have explored the damage of carbon nanomaterials to organisms at the molecular level. This review pays special emphasis on how proteins response to the main carbon nanomaterials (fullerene, carbon nanotubes, graphene and their derivatives). In addition, how to use the interaction between carbon nanomaterials and proteins to do some beneficial things for human and the development of safe nanomaterials is simply discussed. Finally, some suggestions have been made to lay a theoretical foundation for future research.

Co-transport of graphene oxide and titanium dioxide nanoparticles in saturated quartz sand: Influences of solution pH and metal ions

Increasing production and application of nanomaterials lead to their environmental release possible. The nanomaterials with different properties may transport together in porous media, and consequently affect their environmental fates. In this study, column experiments were conducted to investigate the co-transport of two typical nanomaterials, graphene oxide (GO) and nano-titanium dioxide (nTiO₂), in saturated quartz sand in NaCl and CaCl₂ electrolyte solutions under both favorable and unfavorable conditions. The breakthrough curves as well as the retained profiles of single and binary nanoparticles were examined. The results indicated that nTiO₂ significantly enhanced the GO retention under all examined conditions, especially at lower pH, higher ionic strength and the presence of divalent cation Ca²⁺. This might be attributed to the formation of less negatively charged and larger-sized GO-nTiO₂ agglomerates as well as the increased retention sites on sand surface by preferentially deposited nTiO₂. However, GO merely slightly enhanced the transport of nTiO₂ in NaCl solutions, whereas had negligible effect on nTiO₂ transport and retention in CaCl₂ solutions. The highly hydrophilic and mobile GO served as a carrier and facilitated the transport of nTiO₂ in NaCl solutions. In CaCl₂ solutions, the strong attachment affinity between positively charged nTiO₂ and negatively charged quartz sand (at pH 4.5), and dramatical accumulation of large nTiO₂ agglomerates near the column inlets (at pH 6.5) led to significant deposition of nTiO₂ on quartz sand. The co-presence of GO failed to counteract the retention of nTiO₂ particles on sand.

Graphene-Based Nanomaterials: From Production to Integration With Modern Tools in Neuroscience

Graphene, a two-dimensional carbon crystal, has emerged as a promising material for sensing and modulating neuronal activity in vitro and in vivo. In this review, we provide a primer for how manufacturing processes to produce graphene and graphene oxide result in materials properties that may be tailored for a variety of applications. We further discuss how graphene may be composited with other bio-compatible materials of interest to make novel hybrid complexes with desired characteristics for bio-interfacing. We then highlight graphene's ever-widen utility and unique properties that may in the future be multiplexed for cross-modal modulation or interrogation of neuronal network. As the biological effects of graphene are still an area of active investigation, we discuss recent development, with special focus on how surface coatings and surface properties of graphene are relevant to its biological effects. We discuss studies conducted in both non-murine and murine systems, and emphasize the preclinical aspect of graphene's potential without undermining its tangible clinical implementation.

Evaluation of Graphene Oxide Induced Cellular Toxicity and Transcriptome Analysis in Human Embryonic Kidney Cells

Graphene, a two-dimensional carbon sheet with single-atom thickness, shows immense promise in several nanoscientific and nanotechnological applications, including in sensors, catalysis, and biomedicine. Although several studies have shown the cytotoxicity of graphene oxide in different cell types, there are no comprehensive studies on human embryonic kidney (HEK293) cells that include transcriptomic analysis and an in vitro investigation into the mechanisms of cytotoxicity following exposure to graphene oxide. Therefore, we exposed HEK293 cells to different concentrations of graphene oxide for 24 h and performed several cellular assays. Cell viability and proliferation assays revealed a significant dose-dependent cytotoxic effect on HEK293 cells. Cytotoxicity assays showed increased lactate dehydrogenase (LDH) leakage and reactive oxygen species (ROS) generation, and decreased levels of reduced glutathione (GSH) and increased level of oxidized glutathione indicative of oxidative stress. This detailed mechanistic approach showed that graphene oxide exposure elicits significant decreases in mitochondrial membrane potential and ATP synthesis, as well as in DNA damage and caspase 3 activity. Furthermore, our RNA-Seq analysis revealed that HEK293 cells exposed to graphene oxide significantly altered the expression of genes involved in multiple apoptosis-related biological pathways. Moreover, graphene oxide exposure perturbed the expression of key transcription factors, promoting these apoptosis-related pathways by regulating their downstream genes. Our analysis provides mechanistic insights into how exposure to graphene oxide induces changes in cellular responses and massive cell death in HEK293 cells. To our knowledge, this is the first study describing a combination of cellular responses and transcriptome in HEK293 cells exposed to graphene oxide nanoparticles, providing a foundation for understanding the molecular mechanisms of graphene oxide-induced cytotoxicity and for the development of new therapeutic strategies.

Handling and Risk Mitigation of Nanoscale Graphene and Related Materials: Some Considerations and Recommendations

The purpose of this communication is to put forward some considerations and recommendations while handling nanomaterials, especially graphene and its derivatives. A large graphene sheet is generally stable and inert; thus, graphene and its derivatives are not considered hazardous, but good laboratory practices should be taken seriously for the safe handling and use of such materials. This article provides some insights about nanoscale graphene handling and some important considerations.

A label-free quantification method for measuring graphene oxide in biological samples

Characterization of carbonaceous nanomaterials (CNMs) exposure is a key step and of great importance towards a better understanding of their toxicity and underlying mechanisms. However, it has been bottlenecked for lack of valid methods capable of quantifying cell-associated CNMs. Here, we developed a new economical and convenient method based on sodium dodecyl sulfate polyacrylamide gel electrophoresis (SDS-PAGE) that could accumulate graphene oxide (GO) at the interface between the loading well and the gel. The sharp black band formed there can be digitalized and the intensity quantified, which was proportional to the amount of GO loaded onto the gel. The method has a detection limit of 84.1 ng. We showed that the amount of GO in three different cell models, mouse macrophage cells (Raw264.7), human epithelial cells (A549) and mouse mesenchymal stem cells (MSC), could be accurately quantified by this assay, with the uptake rates decreasing in the order of MSC > Raw264.7 > A549. The results were consistent with the fluorescent imaging on cells exposed to fluorescence-labeled GO and TEM examination on ultrathin cell sections. The surprisingly highest uptake rate of MSC might be due to their abundant intracellular vesicles, which deserves further investigation. The novel method provides a complementary quantitative tool to the use of radioactive markers and fluorescent labeling of carbon nanomaterials and may facilitate the toxicological studies on carbon nanomaterials.

Multifunctional graphene oxide/iron oxide nanoparticles for magnetic targeted drug delivery dual magnetic resonance/fluorescence imaging and cancer sensing

Graphene Oxide (GO) has recently attracted substantial attention in biomedical field as an effective platform for biological sensing, tissue scaffolds and in vitro fluorescence imaging. However, the targeting modality and the capability of its in vivo detection have not been explored. To enhance the functionality of GO, we combine it with superparamagnetic iron oxide nanoparticles (Fe3O4 NPs) serving as a biocompatible magnetic drug delivery addends and magnetic resonance contrast agent for MRI. Synthesized GO-Fe3O4 conjugates have an average size of 260 nm and show low cytotoxicity comparable to that of GO. Fe3O4 nanoparticles provide superparamagnetic properties for magnetic targeted drug delivery allowing simple manipulation by the magnetic field and magnetic resonance imaging with high r2/r1 relaxivity ratios of ~10.7. GO-Fe3O4 retains pH-sensing capabilities of GO used in this work to detect cancer versus healthy environments in vitro and exhibits fluorescence in the visible for bioimaging. As a drug delivery platform GO-Fe3O4 shows successful fluorescence-tracked transport of hydrophobic doxorubicin non-covalently conjugated to GO with substantial loading and 2.5-fold improved efficacy. As a result, we propose GO-Fe3O4 nanoparticles as a novel multifunctional magnetic targeted platform for high efficacy drug delivery traced in vitro by GO fluorescence and in vivo via MRI capable of optical cancer detection.

Enhancement of organic pollutants bio-decontamination from aqueous solution using newly-designed Pseudomonas putida-GA/MIL-100(Fe) bio-nanocomposites

As a natural adsorption material, graphene has become a hot research topic in water treatment due to its unique framework, large surface area, low cost, and simple preparation. Here, a series of composite material aerogels (GA/MIL-100(Fe)) consisting of Fe metal-organic frameworks (MIL-100 (Fe)) and graphene-based aerogel (GA) were prepared through a hydrothermal and step-by-step strategy and used for the adsorption of an azo dye in wastewater, scilicet acid orange 10 (AO10). The adsorption equilibrium of AO10 solutions with concentrations of 50 and 100 mg/L was reached within 45 min but the dye could not be fully removed. Besides, the synthesized composite material (GA/MIL-100(Fe)) was a good carrier for immobilized Pseudomonas putida cells due to its good biocompatibility and non-toxicity. A new, environmentally friendly adsorption and biodegradation process has been exploited here, which was to immobilize bacterial cells to the surface of GA/MIL-100(Fe) by a covalent bonding method to form a novel biocomposite material. The material could be used to completely remove AO10 dyes in 14 and 26 h from solutions with initial AO10 concentrations of 50 and 100 mg/L, respectively. This way of combining biological and physical adsorption has a higher processing efficiency and shows huge potential for the treatment of industrial wastewater.

Graphene based adsorbents for remediation of noxious pollutants from wastewater

The contamination of water resources with noxious pollutants is a serious issue. Many aquatic systems are contaminated with different toxic inorganic and organic species; coming to wastewater from various anthropogenic sources such as industries, agriculture, mining, and domestic households. Keeping in view of this, wastewater treatment appears to the main environmental challenge. Adsorption is one of the most efficient techniques for removing all most all types of pollutants i.e. inorganics and organics. Nowadays, graphene and its composite materials are gaining importance as nano adsorbents. Graphene; a two-dimensional nanomaterial having single-atom graphite layer; has attracted a great interest in many application areas (including wastewater treatment) due to its unique physico-chemical properties. The present paper is focused on the remediation of noxious wastes from wastewater using graphene based materials as adsorbents, and it contains all the details on materials - i.e., from their synthesis to application in the field of wastewater treatment (removal of hazardous contaminants of different chemical nature - heavy and rare-earth metal ions, and organic compounds - from wastewater effluents. The efficiency of the adsorption and desorption of these substances is considered. Certainly, this article will be useful for nano environmentalist to design future experiments for water treatment.

A Multifunctional Graphene Oxide Platform for Targeting Cancer

Diagnosis of oncological diseases remains at the forefront of current medical research. Carbonic Anhydrase IX (CA IX) is a cell surface hypoxia-inducible enzyme functionally involved in adaptation to acidosis that is expressed in aggressive tumors; hence, it can be used as a tumor biomarker. Herein, we propose a nanoscale graphene oxide (GO) platform functionalized with magnetic nanoparticles and a monoclonal antibody specific to the CA IX marker. The GO platforms were prepared by a modified Hummers and Offeman method from exfoliated graphite after several centrifugation and ultrasonication cycles. The magnetic nanoparticles were prepared by a chemical precipitation method and subsequently modified. Basic characterization of GO, such as the degree of oxidation, nanoparticle size and exfoliation, were determined by physical and chemical analysis, including X-ray photoelectron spectroscopy (XPS), transmission electron microscopy (TEM), energy dispersive X-ray analysis (EDX), and atomic force microscopy (AFM). In addition, the size and properties of the poly-L-lysine-modified magnetic nanoparticles were characterized. The antibody specific to CA IX was linked via an amidic bond to the poly-L-lysine modified magnetic nanoparticles, which were conjugated to GO platform again via an amidic bond. The prepared GO-based platform with magnetic nanoparticles combined with a biosensing antibody element was used for a hypoxic cancer cell targeting study based on immunofluorescence.

Supramolecular Aptamers on Graphene Oxide for Efficient Inhibition of Thrombin Activity

Graphene oxide (GO), a two-dimensional material with a high aspect ratio and polar functional groups, can physically adsorb single-strand DNA through different types of interactions, such as hydrogen bonding and π-π stacking, making it an attractive nanocarrier for nucleic acids. In this work, we demonstrate a strategy to target exosites I and II of thrombin simultaneously by using programmed hybrid-aptamers for enhanced anticoagulation efficiency and stability. The targeting ligand is denoted as Supra-TBA_15/29 (supramolecular TBA_15/29), containing TBA₁₅ (a 15-base nucleotide, targeting exosite I of thrombin) and TBA₂₉ (a 29-base nucleotide, targeting exosite II of thrombin), and it is designed to allow consecutive hybridization of TBA₁₅ and TBA₂₉ to form a network of TBAs (i.e., supra-TBA_15/29). The programmed hybrid-aptamers (Supra-TBA_15/29) were self-assembled on GO to further boost anticoagulation activity by inhibiting thrombin activity, and thus suppress the thrombin-induced fibrin formation from fibrinogen. The Supra-TBA_15/29-GO composite was formed mainly through multivalent interaction between poly(adenine) from Supra-TBA_15/29 and GO. We controlled the assembly of Supra-TBA_15/29 on GO by regulating the preparation temperature and the concentration ratio of Supra-TBA_15/29 to GO to optimize the distance between TBA₁₅ and TBA₂₉ units, aptamer density, and aptamer orientation on the GO surfaces. The dose-dependent thrombin clotting time (TCT) delay caused by Supra-TBA_15/29-GO was >10 times longer than that of common anticoagulant drugs including heparin, argatroban, hirudin, and warfarin. Supra-TBA_15/29-GO exhibits high biocompatibility, which has been proved by in vitro cytotoxicity and hemolysis assays. In addition, the thromboelastography of whole-blood coagulation and rat-tail bleeding assays indicate the anticoagulation ability of Supra-TBA_15/29-GO is superior to the most widely used anticoagulant (heparin). Our highly biocompatible Supra-TBA_15/29-GO with strong multivalent interaction with thrombin [dissociation constant (K _d) = 1.9 × 10^-11 M] shows great potential as an effective direct thrombin inhibitor for the treatment of hemostatic disorders.

Cobalt nanowire-based multifunctional platform for targeted chemo-photothermal synergistic cancer therapy

Cobalt nanowires (CoNWs) simultaneously possessing advantages in photothermal effect, targeting drug delivery and photoacoustic imaging property are hopefully promising strategies to further improve the treatment efficiency and reduce the side effects of cancer chemotherapy. Herein, a unique cobalt-based structure decorated with graphene oxide (GO) and polyethylene glycol (PEG) is fabricated through a facile approach. The resultant nanohybrids show relatively low cytotoxicity, favorable biocompatibility as well as inherit the outstanding properties of cobalt. Moreover, CoNWs decorated with GO and PEG (CoNWs-GO-PEG) can load therapeutic drug molecules (e.g., doxorubicin, DOX) with a high drug loading capacity (992.91 mg/g), and simultaneously they are responsive to pH, NIR (near-infrared) irradiation and magnetism stimulation. Accordingly, CoNWs-GO-PEG-DOX shows the satisfactory effect of eliminating cancer cells with synergistic chemo-photothermal therapy in vitro. Current work provides a solid demonstration of the potential of CoNWs-GO-PEG for serving as a targeted antitumor agent in synergistic chemo-photothermal therapy.

Carbon-based materials as adsorbent for antibiotics removal: Mechanisms and influencing factors

With the development of the removal of organic pollutants in the soil and water environment, antibiotics have been considered as emerging pollutants and received considerable attention among the scientific community. Thus, there is a need for an effective, economical, fast, operational feasible and environmental-friendly technology to remove antibiotics. Adsorption technology would be one of the most promising option on the basis that it best meets the criteria we set out above. From the most primitive activated carbon to the most innovative modified biochar, carbon-based materials have played a significant role in the adsorption process of antibiotics all the time. This paper reviews the adsorption behavior of some representative antibiotics (e.g., chloramphenicols, sulfonamides, tetracyclines, flouroquinolones) over various carbonaceous materials (i.e., activated carbon, carbon nanotubes, graphene, and biochar). Nevertheless, in addition to the structural characteristics and adsorption capacities of carbon-based materials, a special emphasis was placed on the underlying adsorption mechanisms and roles of different influencing factors in the adsorption process. Moreover, the knowledge gaps and research challenges have been highlighted, including design and optimization of the carbonaceous materials for antibiotics adsorption.

Co-exposure of graphene oxide with trace elements: Effects on acute ecotoxicity and routine metabolism in Palaemon pandaliformis (shrimp)

Graphene oxide (GO) has been evaluated for application in environmental remediation and pollution control strategies. However, the side effects caused by the interactions of GO with classical pollutants in aquatic environments are still largely unknown. In this work, the ecotoxicological effects of GO, cadmium, zinc and the interactions between GO and these trace elements (co-exposure) were evaluated through acute toxicity tests and routine metabolism (i.e., oxygen consumption and ammonia excretion) in Palaemon pandaliformis (shrimp). After 96 h of exposure, GO did not present acute ecotoxicity at concentrations up to 5.0 mg L^-1. However, the association of GO with Cd or Zn increased the toxicity of these trace elements as demonstrated by the decrease in LC₅₀ values. The 96 h LC₅₀ of Cd associated with GO was 1.7 times less than the 96 h LC₅₀ of Cd alone. Similarly, the 96 h LC₅₀ of Zn associated with GO was 1.8 times less than the 96 h LC₅₀ of Zn alone. Additionally, the co-exposure of GO with trace elements impaired the routine metabolism of P. pandaliformis. Finally, the GO potentiated the ecotoxicological effects of Cd and Zn in the shrimp model. Future research on this emerging nanomaterial should focus on its use and disposal in aquatic ecosystems.

Graphene quantum dots unraveling: Green synthesis, characterization, radiolabeling with 99mTc, in vivo behavior and mutagenicity

Graphene is one of the crystalline forms of carbon, along with diamond, graphite, carbon nanotubes, and fullerenes, and is considered as a revolutionary and innovating product. The use of a graphene-based nanolabels is one of the latest and most prominent application of graphene, especially in the field of diagnosis and, recently, in loco radiotherapy when coupled with radioisotopes. However, its biological behavior and mutagenicity in different cell or animal models, as well as the in vivo functional activities, are still unrevealed. In this study we have developed by a green route of synthesizing graphene quantum dots (GQDs) and characterized them. We have also developed a methodology for direct radiolabeling of GQDs with radioisotopes.Finally; we have evaluated in vivo biological behavior of GQDs using two different mice models and tested in vitro mutagenicity of GQDs. The results have shown that GQDs were formed with a size range of 160-280 nm, which was confirmed by DRX and Raman spectroscopy analysis, corroborating that the green synthesis is an alternative, environmentally friendly way to produce graphene. The radiolabeling test has shown that stable radiolabeled GQDs can be produced with a high yield (>90%). The in vivo test has demonstrated a ubiquitous behavior when administered to healthy animals, with a high uptake by liver (>26%) and small intestine (>25%). Otherwise, in an inflammation/VEGF hyperexpression animal model (endometriosis), a very peculiar behavior of GQDs was observed, with a high uptake by kidneys (over 85%). The mutagenicity test has demonstrated A:T to G:C substitutions suggesting that GQDs exhibits mutagenic activity.

Thermal Reduction of Graphene Oxide Mitigates Its In Vivo Genotoxicity Toward Xenopus laevis Tadpoles

The worldwide increase of graphene family materials raises the question of the potential consequences resulting from their release in the environment and future consequences on ecosystem health, especially in the aquatic environment in which they are likely to accumulate. Thus, there is a need to evaluate the biological and ecological risk but also to find innovative solutions leading to the production of safer materials. This work focuses on the evaluation of functional group-safety relationships regarding to graphene oxide (GO) in vivo genotoxic potential toward X. laevis tadpoles. For this purpose, thermal treatments in H₂ atmosphere were applied to produce reduced graphene oxide (rGOs) with different surface group compositions. Analysis performed indicated that GO induced disturbances in erythrocyte cell cycle leading to accumulation of cells in G0/G1 phase. Significant genotoxicity due to oxidative stress was observed in larvae exposed to low GO concentration (0.1 mg·L⁻¹). Reduction of GO at 200 °C and 1000 °C produced a material that was no longer genotoxic at low concentrations. X-ray photoelectron spectroscopy (XPS) analysis indicated that epoxide groups may constitute a good candidate to explain the genotoxic potential of the most oxidized form of the material. Thermal reduction of GO may constitute an appropriate “safer-by-design” strategy for the development of a safer material for environment.

General Self-Assembly Method for Deposition of Graphene Oxide into Uniform Close-Packed Monolayer Films

Depositing a morphologically uniform monolayer film of graphene oxide (GO) single-layer sheets is an important step in the processing of many composites and devices. Conventional Langmuir-Blodgett (LB) deposition is often considered to give the highest degree of morphology control, but film microstructures still vary widely between GO samples. The main challenge is in the sensitive self-assembly of GO samples with different sheet sizes and degrees of oxidation. To overcome this drawback, here, we identify a general method that relies on robust assembly between GO and a cationic surfactant (cationic surfactant-assisted LB). We systematically compared conventional LB and cationic surfactant-assisted LB for three common GO samples of widely different sheet sizes and degrees of oxidation. Although conventional LB may occasionally provide satisfactory film morphology, cationic surfactant-assisted LB is general and allows deposition of films with tunable and uniform morphologies-ranging from close-packed to overlapping single layers-from all three types of GO samples investigated. Because cationic surfactant-assisted LB is robust and general, we expect this method to broaden and facilitate the use of GO in many applications where precise control over film morphology is crucial.

Nanotoxicity of different sizes of graphene (G) and graphene oxide (GO) in vitro and in vivo

Graphene family nanomaterials (GFNs) have attracted significant attention due to their unique characteristics and applications in the fields of biomedicine and nanotechnology. However, previous studies highlighted the in vitro and in vivo toxicity of GFNs with size and oxidation state differences are still elusive. Therefore, we prepared graphene (G) and graphene oxide (GO) of three different sizes (S-small, M-medium, and L-large), and characterized them using multiple surface-sensitive analytical techniques. In vitro assays using HEK 293T cells revealed that the small and large sizes of G and GO significantly reduced the cell viability and increased DNA damage, accompanying with activated reactive oxygen species (ROS) generation and induced various expressions of associated critical genetic markers. Moreover, the bacterial assays highlighted that G and GO caused strong acute toxicity on Tox2 bacteria. Effects of G were higher than GO and showed size dependent effect: L > M > S, while the medium size of GO induced mild genetic toxicity on RecA bacteria. In vivo assays revealed that exposure to G and GO caused the developmental toxicity, induced ROS generation, and activated related pathways (specifically GO) in zebrafish. Taken together, G showed stronger ability to decrease the survival rate and induce the acute toxicity, while GO showed obvious toxicity in terms of DNA damages, ROS generation, and abnormal gene expressions. Our findings highlighted that G and GO differentially induced toxicity based on their varying physical characteristics, especially sizes and oxidation state, and exposure concentrations and sensitivity of the employed in vitro and in vivo models. In short, this study provided deep insights on the negative effects of GFNs exposure.

Graphene Oxide Tablets for Sample Preparation of Drugs in Biological Fluids: Determination of Omeprazole in Human Saliva for Liquid Chromatography Tandem Mass Spectrometry

In this study, a novel sort of sample preparation sorbent was developed, by preparing thin layer graphene oxide tablets (GO-Tabs) utilizing a mixture of graphene oxide and polyethylene glycol on a polyethylene substrate. The GO-Tabs were used for extraction and concentration of omeprazole (OME) in human saliva samples. The determination of OME was carried out using liquid chromatography-tandem mass spectrometry (LC–MS/MS) under gradient LC conditions and in the positive ion mode (ESI+) with mass transitions of m/z 346.3→198.0 for OME and m/z 369.98→252.0 for the internal standard. Standard calibration for the saliva samples was in the range of 2.0–2000 nmol L⁻¹. Limits of detection and quantification were 0.05 and 2.0 nmol L⁻¹, respectively. Method validation showed good method accuracy and precision; the inter-day precision values ranged from 5.7 to 8.3 (%RSD), and the accuracy of determinations varied from −11.8% to 13.3% (% deviation from nominal values). The extraction recovery was 60%, and GO-Tabs could be re-used for more than ten extractions without deterioration in recovery. In this study, the determination of OME in real human saliva samples using GO-Tab extraction was validated.

In vitro cardiotoxicity evaluation of graphene oxide

Graphene is a two-dimensional (2D) monolayer of carbon atoms, tightly packed, forming a honey comb crystal lattice, with physical, chemical, and mechanical properties greatly used for energy storage, electrochemical devices, and in nanomedicine. Many studies showed that nanomaterials have side-effects on health. At present, there is a lack of information regarding graphene and its derivatives including their cardiotoxic properties. The aim of the present study was to evaluate the toxicity of nano-graphene oxide (nano-GO) in the rat cardiomyoblast cell line H9c2 and the involvement of oxidative processes. The cell viability was evaluated with the fluorescein diacetate (FDA)/propidium iodide (PI) and in the trypan blue exclusion assay, furthermore mitochondrial membrane potential and production of free radicals were measured. Genotoxicity was evaluated in comet assay and low molecular weight DNA experiment. Reduction of cell viability with 20, 40, 60, 80, and 100 μg/mL nano-GO was observed after 24 h incubation. Besides, nano-GO induced a mitochondrial hyperpolarization and a significant increase of free radicals production in the same concentrations. DNA breaks were observed at 40, 60, 80, and 100 μg/mL. This DNA damage was accompanied by a significant increase in LMW DNA only at 40 μg/mL. In conclusion, the nano-GO caused cardiotoxicity in our in vitro model, with mitochondrial disturbances, generation of reactive species and interactions with DNA, indicating the importance of the further evaluation of the safety of nanomaterials.

Carbon-Based Nanomaterials for Biomedical Applications: A Recent Study

The study of carbon-based nanomaterials (CBNs) for biomedical applications has attracted great attention due to their unique chemical and physical properties including thermal, mechanical, electrical, optical and structural diversity. With the help of these intrinsic properties, CBNs, including carbon nanotubes (CNT), graphene oxide (GO), and graphene quantum dots (GQDs), have been extensively investigated in biomedical applications. This review summarizes the most recent studies in developing of CBNs for various biomedical applications including bio-sensing, drug delivery and cancer therapy.

Graphene Oxide-Based Targeting of Extracellular Cathepsin D and Cathepsin L As A Novel Anti-Metastatic Enzyme Cancer Therapy

Overexpression and secretion of the enzymes cathepsin D (CathD) and cathepsin L (CathL) is associated with metastasis in several human cancers. As a superfamily, extracellularly, these proteins may act within the tumor microenvironment to drive cancer progression, proliferation, invasion and metastasis. Therefore, it is important to discover novel therapeutic treatment strategies to target CathD and CathL and potentially impede metastasis. Graphene oxide (GO) could form the basis of such a strategy by acting as an adsorbent for pro-metastatic enzymes. Here, we have conducted research into the potential of targeted anti-metastatic therapy using GO to adsorb these pro-tumorigenic enzymes. Binding of CathD/L to GO revealed that CathD/L were adsorbed onto the surface of GO through its cationic and hydrophilic residues. This work could provide a roadmap for the rational integration of CathD/L-targeting agents into clinical settings.

Graphene Oxide Nanoplatelets Potentiate Anticancer Effect of Cisplatin in Human Lung Cancer Cells

Graphene oxide (GO) has been widely explored by many in drug delivery strategies and toxicity assays. The toxicity of graphene oxide depends on the size of the sheets. Smaller sheets show lower toxicity, a quality which is essential for utilization in biomedical applications. However, despite vast research on GO, anticancer properties and drug carrier capabilities of graphene oxide nanoplatelets have yet to be fully explored. Herein, we have uniquely prepared graphene oxide nanoplatelets (GONPs) from well-defined stacked graphite nanofibers (SGNF) with a base of 50 × 50 nm² for toxicity and drug potentiation studies when coadministered with the chemotherapeutic drug cisplatin (CP) in human lung cancer cells, A549 cells. Results obtained from our studies have found that not only were GONPs able to act as drug carriers, but they can also significantly potentiate anticancer effect of CP in A549 cells.

A Hybrid Nanoplatform of Graphene Oxide/Nanogold for Plasmonic Sensing and Cellular Applications at the Nanobiointerface

In this study, nanocomposites of spherical gold nanoparticles (AuNPs) and graphene oxide (GO) nanosheets were fabricated by a simple one-step reduction method. The characterisation by UV-visible spectroscopy of the plasmonic sensing properties pointed out to a strong interaction between graphene and metal nanoparticles in the hybrid GO-AuNP, as confirmed by nuclear magnetic resonance. Moreover, atomic force microscopy analyses demonstrated that the gold nanoparticles were mostly confined to the basal planes of the GO sheets. The response of the nanoassemblies at the biointerface with human neuroblastoma SH-SY5Y cell line was investigated in terms of nanotoxicity as well as of total and mitochondrial reactive oxygen species production. Confocal microscopy imaging of cellular internalization highlighted the promising potentialities of GO-AuNP nanoplatforms for theranostic (i.e., sensing/imaging + therapy) applications.

Modeling Interactions between Liposomes and Hydrophobic Nanosheets

2D nanomaterials could cause structural disruption and cytotoxic effects to cells, which greatly challenges their promising biomedical applications including biosensing, bioimaging, and drug delivery. Here, the physical and mechanical interaction between lipid liposomes and hydrophobic nanosheets is studied utilizing coarse-grained (CG) molecular dynamics (MD) simulations. The simulations reveal a variety of characteristic interaction morphologies that depend on the size and the orientation of nanosheets. Dynamic and thermodynamic analyses on the morphologic evolution provide insights into molecular motions such as "nanosheet rotation," "lipid extraction," "lipid flip-flop," and "lipid spreading." Driven by these molecular motions, hydrophobic nanosheets cause morphologic changes of liposomes. The lipid bilayer structure can be corrugated, and the overall liposome sphere can be split or collapsed by large nanosheets. In addition, nanosheets embedded into lipid bilayers greatly weaken the fluidity of lipids, and this effect can be cumulatively enhanced as nanosheets continuously intrude. These results could facilitate molecular-level understanding on the cytotoxicity of nanomaterials, and help future nanotoxicology studies associating computational modeling with experiments.

An insight into Cadmium poisoning and its removal from aqueous sources by Graphene Adsorbents

Graphene alone, in modified form or its composites had find their explicit position in the field of adsorption technology and hence assist in detection and removal of heavy metals like Cd (permissible limit 0.1 mg/L), which can cause various physiological problems if entered in variety of biota. Attributed to their unique physiognomies graphene-based adsorbent had classed themselves superior as compared to other carbonaceous adsorbent like CNT's or activated carbon, etc. This assessment summarizes the validity of graphene and its composite as a superior adsorbent for decontamination of Cd from aqueous environment; in addition, this evaluation also pronounces the toxicity profile of trace graphene and necessity of regeneration of the adsorbent.

Enhanced bone regeneration of the silk fibroin electrospun scaffolds through the modification of the graphene oxide functionalized by BMP-2 peptide

Introduction

Bone tissue engineering has become one of the most effective methods to treat bone defects. Silk fibroin (SF) is a natural protein with no physiological activities, which has features such as good biocompatibility and easy processing and causes minimal inflammatory reactions in the body. Scaffolds prepared by electrospinning SF can be used in bone tissue regeneration and repair. Graphene oxide (GO) is rich in functional groups, has good biocompatibility, and promotes osteogenic differentiation of stem cells, while bone morphogenetic protein-2 (BMP-2) polypeptide has an advantage in promoting osteogenesis induction. In this study, we attempted to graft BMP-2 polypeptide onto GO and then bonded the functionalized GO onto SF electrospun scaffolds through electrostatic interactions. The main purpose of this study was to further improve the biocompatibility of SF electrospun scaffolds, which could promote the osteogenic differentiation of bone marrow mesenchymal stem cells and the repair of bone tissue defects.

Materials and methods

The successful synthesis of GO and functionalized GO was confirmed by transmission electron microscope, X-ray photoelectron spectroscopy, and thermogravimetric analysis. Scanning electron microscopy, atomic force microscopy, mechanical test, and degradation experiment confirmed the preparation of SF electrospun scaffolds and the immobilization of GO on the fibers. In vitro experiment was used to verify the biocompatibility of the composite scaffolds, and in vivo experiment was used to prove the repairing ability of the composite scaffolds for bone defects.

Results

We successfully fabricated the composite scaffolds, which enhanced biocompatibility, not only promoting cell adhesion and proliferation but also greatly enhancing in vitro osteogenic differentiation of bone marrow stromal cells using either an osteogenic or non-osteogenic medium. Furthermore, transplantation of the composite scaffolds significantly promoted in vivo bone formation in critical-sized calvarial bone defects.

Conclusion

These findings suggested that the incorporation of BMP-2 polypeptide-functionalized GO into chitosan-coated SF electrospun scaffolds was a viable strategy for fabricating excellent scaffolds that enhance the regeneration of bone defects.