The addition of mammalian cell culture medium impacts nanoparticle toxicity in zebrafish

Engineered nanomaterials (ENMs) are ubiquitous in contemporary applications, yet their environmental and human health impacts remain inadequately understood. This study addresses the challenge of identifying potential risks associated with ENM exposure by highlighting the significant variability in existing research methodologies. Without a systematic collection of toxicological data that encompasses standardized materials, relevant platforms, and assays, the task of identifying potential risks linked to ENM exposure becomes an intricate challenge. In vitro assessments often use media rich in ionic species, such as RPMI and fetal bovine serum (FBS). Zebrafish embryos, known to develop normally in low-ionic environments, were exposed to Cerium Oxide, Zinc Oxide, and Graphene Oxides in different media at varying concentrations. Here, we discovered that zebrafish embryos tolerated a mix of 80 % RPMI, 2 % FBS, and 1 % antibiotic cocktail. The results revealed that adverse effects observed in zebrafish with certain nanomaterials in Ultra-Pure (UP) water were mitigated in cell culture medium, emphasizing the importance of revisiting previously considered non-toxic materials in vitro. The zebrafish results underscore the importance of utilizing a multidimensional in vivo platform to gauge the biological activity of nanomaterials accurately.

Boosting CO2 Photoreduction to Formate or CO with High Selectivity over a Covalent Organic Framework Covalently Anchored on Graphene Oxide

Covalent organic frameworks (COFs) have been widely studied in photocatalytic CO2 reduction reaction (CO2 RR). However, pristine COFs usually exhibit low catalytic efficiency owing to the fast recombination of photogenerated electrons and holes. In this study, we fabricated a stable COF-based composite (GO-COF-366-Co) by covalently anchoring COF-366-Co on the surface of graphene oxide (GO) for the photocatalytic CO2 reduction. Interestingly, in absolute acetonitrile (CH3 CN), GO-COF-366-Co shows a high selectivity of 94.4 % for the photoreduction of CO2 to formate, with a formate yield of 15.8 mmol/g, which is approximately four times higher than that using the pristine COF-366-Co. By contrast, in CH3 CN/H2 O (v : v=4 : 1), the main product for the photocatalytic CO2 reduction over GO-COF-366-Co is CO (96.1 %), with a CO yield as high as 52.2 mmol/g, which is also approximately four times higher than that using the pristine COF-366-Co. Photoelectrochemical experiments demonstrate the covalent bonding of COF-366-Co and GO to form the GO-COF-366-Co composite facilitates charge separation and transfer significantly, thereby accounting for the enhanced catalytic activity. In addition, theoretical calculations and in situ Fourier transform infrared spectroscopy reveal H2 O can stabilize the *COOH intermediate to further form a *CO intermediate via O-H(aq)⋅⋅⋅O(*COOH) hydrogen bonding, thus explaining the regulated photocatalytic performance.

Titanium Dioxide/Graphene Oxide Composite Coatings for 316 Stainless Steel Dental Implants

Stainless steel has been used in orthopedics and orthodontic fields. However, it cannot be used for fabrication of dental implants due to its inertness, low biocompatibility and weak resistance to corrosion. A composite coating of titanium oxide /graphene oxide has been prepared for stainless steel to improve its biological properties. Stainless steel discs were polished, cleaned and pre-treated with a mixture of HNO3 and HF acid for 15 min. The composite coating composed of TiO2 produced by sol-gel technique and doped with 0.75 wt% graphene oxide. XRD, SEM-EDX and AFM were employed to characterize the composite coating. The anti-bacterial action of the composite coating was investigated against S. aureus and E. coli. The corrosion resistance of coated and noncoated samples was assessed in SBF using electrochemical technique. Cytotoxicity was assessed using osteoblast-like cells. The wettability was determined by contact angle, and bioactivity assessed by immersion in SBF. The results revealed that the composite coating was dense with few micro-cracks, and was not cytotoxic to osteoblast-like cells. The composite coating reduced bacterial colonies and the corrosion rate of the steel was improved. The wettability of the sample was increased with the composite coating and apatite formation appeared after 21 days.

Electrochemical Exfoliation of Graphene Oxide: Unveiling Structural Properties and Electrochemical Performance

An electrochemical exfoliation method for the production of graphene oxide and its characterization by electrochemical techniques are presented here. Graphite rods are used as working electrode in a three-electrode electrochemical cell, and electro-exfoliation is achieved by applying anodic polarization in a sulfuric acid solution. The electrochemical process involved two steps characterized by an intercalation at lower potential and an exfoliation at higher potential. The electrochemical behavior of the produced GO is studied through cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS). X ray Photoelectronic Spectroscopy (XPS), Raman spectroscopy, Transmission Electron Microscopy (TEM), and Atomic Force Microscopy (AFM) are employed to characterize the structural and chemical properties of the exfoliated GO. The results demonstrate that the electrochemical exfoliation method yields GO materials with varying degrees of oxidation, defect density, and crystallite size, depending on the applied potential and acid concentration. The graphene oxide samples exhibited distinct electrochemical properties, including charge transfer resistance, interfacial capacitance, and relaxation times for the charge transfer, as revealed by CV and EIS measurements with a specifically selected redox probe. The comprehensive characterization performed provides valuable insights into the structure-property relationships of the GO materials synthesized through electrochemical exfoliation of graphite.

A synergistic approach combining Adsorption and Biodegradation for effective treatment of Acid Blue 113 dye by Klebsiella grimontii entrapped Graphene Oxide-Calcium Alginate Hydrogel Beads

This study investigated the degradation of Acid Blue 113 (AB 113) dye using Klebsiella grimontii entrapped Graphene Oxide-Calcium Alginate Hydrogel beads (KG-GO-CA) in a Fluidized Bed Bioreactor (FBBR) under varying inlet loading rates. The minimum fluidization velocity of the KG-GO-CA hydrogel beads in FBBR was found to be 0.15 mm/s. The KG-GO-CA beads showed a maximum removal efficiency of 94.6% at an inlet flow rate of 20 mL/h over 15 days. Reusability studies indicated a removal efficiency of 70.6 ± 2.5% for AB 113 after the 12th cycle. Langmuir adsorption isotherm showed the best fit (R2 = 0.98724) with model parameters of Qm (203.83 mg/g) and Ki (0.0101 L/g). The study also confirmed that treated wastewater was more environmentally safe for domestic and commercial uses than untreated wastewater. The research highlights the potential use of KG-GO-CA hydrogel beads for removing dyes from wastewater.

Ultrasmall graphene oxide for combination of enhanced chemotherapy and photothermal therapy of breast cancer

Combination of chemotherapy and photothermal therapy (PTT) is an effective way for the treatment of cancer. Graphene oxide (GO) with a large specific surface area and strong near-infrared (NIR) absorbance have been widely used as both the chemotherapeutic carriers and photothermal agents. The smaller lateral size and higher oxidation degree of GO corresponding to better dispersion in water and lower cytotoxicity. Therefore, the preparation of ultrafine GO nanosheets (UGO) with the controlled size and high oxidation degree is of significant importance to meet the demands of biological applications. Herein, we developed a versatile drug delivery nanoplatform based on poly(dopamine) (PDA) modified ultrasmall graphene oxide (UGO) with small size (average size of 30 nm) and high oxidation content (45 wt. %). The fabricated PDA-modified UGO (UGP) exhibits well biocompatibility, excellent photothermal performance and high drug loading capacity of doxorubicin (DOX). Under NIR laser irradiation, the photothermal-induced release of DOX could achieve the combination of chemotherapy and PTT for efficient therapy of breast cancer. This work established UGO as a novel drug delivery with excellent photothermal performance for the combination of chemotherapy and PTT of tumors.

Synchronous Dual Electrolyte Additive Sustains Zn Metal Anode with 5600 h Lifespan

Despite conspicuous merits of Zn metal anodes, the commercialization is still handicapped by rampant dendrite formation and notorious side reaction. Manipulating the nucleation mode and deposition orientation of Zn is a key to rendering stabilized Zn anodes. Here, a dual electrolyte additive strategy is put forward via the direct cooperation of xylitol (XY) and graphene oxide (GO) species into typical zinc sulfate electrolyte. As verified by molecular dynamics simulations, the incorporated XY molecules could regulate the solvation structure of Zn²⁺ , thus inhibiting hydrogen evolution and side reactions. The self-assembled GO layer is in favor of facilitating the desolvation process to accelerate reaction kinetics. Progressive nucleation and orientational deposition can be realized under the synergistic modulation, enabling a dense and uniform Zn deposition. Consequently, symmetric cell based on dual additives harvests a highly reversible cycling of 5600 h at 1.0 mA cm^-2 /1.0 mAh cm^-2 .

A Sustainable Approach for Graphene Oxide-supported Metal N-Heterocyclic Carbenes Catalysts

Sustainable noble metal-N-heterocyclic carbenes (NHC's) are a topic of arising concern in both the chemical industry and the academic community due to a growing consciousness of environmental pollution and scarcity. Recovering and reusing homogeneous catalysts from the reaction mixture requires a tremendous amount of capital investment in the chemical manufacturing industry. Heterogeneous catalysts are proved to have better functional groups tolerance; however, catalysts support largely influences the active catalyst sites to affect catalyst efficiency and selectivity. Thus the, choice of catalyst supports plays an almost decisive role in this emerging area of catalysis research. Graphene oxide (GO)/reduced graphene oxide (rGO) support has a potential growth in heterogeneous catalysis owing to their commercial availability, considerably larger surface area, inert towards chemical transformations, and easy surface functionalization to attached metal complexes via covalent and non-covalent aromatic π-conjugates. To take advantage of two independently well-established research areas of noble metal-N-heterocyclic carbenes and GO/rGO support via covalent or non-covalent interactions approach would offer novel heterogeneous complexes with improved catalytic efficiency without sacrificing product selectivity. This unique concept of marrying metal-N-heterocyclic carbenes with GO/rGO support has potential growth in the chemical and pharmaceutical industry, however, limited examples are reported in the literature. In this perspective, a comprehensive summary of metal-NHC synthesis on GO/rGO support and synthetic strategies to graft M-NHC onto GO/rGO surface, catalytic efficiency, for the catalytic transformation are critically reviewed. Furthermore, a plausible mechanism for non-covalent grafting methodology is summarized to direct readers to give a better understanding of M-NHC@rGO complexes. This would also allow the designing of engineered catalysts for unexplored catalytic applications.

PVA based nanofiber containing GO modified with Cu nanoparticles and loaded curcumin; high antibacterial activity with acceleration wound healing

BACKGROUND

The skin is one of the most essential organs of the body that plays a vital role. Protecting the skin from damage is one of the most critical challenges. Therefore, the ideal wound dressing that has antibacterial, mechanical, biodegradable, and non-toxic properties can protect the skin against injury and accelerate and heal the wound.

OBJECTIVE

in this study, a nano-wound dressing is designed for the first time. This work is aimed to optimize and act as a dressing to speed up the wound healing process.

METHODS

Graphene Oxide (GO) was produced by the hummer method. In the next step, GO-copper (Cu) nanohybrid was prepared, then GO-Cu -Curcumin (Cur) nanohybrid was synthesized. Using the electrospinning method, polyvinyl alcohol (PVA)/ GO-Cu -Cur were spun, and finally, related analyzes were performed to investigate the properties and synthesized chemicals.

RESULTS

The results showed that the nanocomposite was synthesized correctly and the diameter of the nanofibers was 328 nm. The use of PVA improved the mechanical properties. In addition, the wound dressing had biodegradable, antimicrobial, and non-toxic properties. The results of the scratch test and animal model showed that this nanocomposite accelerated wound healing and after 14 days showed 92.25% wound healing.

CONCLUSION

The synthesized nanocomposite has the individual properties and characteristics of an ideal wound dressing and replaces traditional methods for wound healing.

Fluorescence study of the influence of centrifugation on graphene oxide dispersions in water and in tannic acid

Graphene oxide (GO) is acquiring a great interest in biomedicine, biotechnology and biochemistry due to its unique properties. However, GO layers are boundbyvan der Waals forces, which results in aggregation. An efficient dispersion of the aggregated nanostructures is crucial from an application viewpoint, hence eco-friendly procedures are pursued. In this work, the potential of tannic acid (TA) as a GO dispersant in water has been investigated for the first time. Transmission electronic microscopy (TEM) was used to visualize the degree of GO exfoliation in the dispersions. To further assess TA dispersant capability, a fluorescent biomolecule, riboflavin, has been selected. GO and TA cause a quenching effect on riboflavin fluorescence, which depends on the GO and TA concentration, the GO/TA weight ratio and the final centrifugation step that was found to be crucial. Multiple regression analysis has been used to determine the quenching constants for TA and GO simultaneously. The GO-riboflavin interaction weakens upon centrifugation. This step, traditionally used to remove the nanomaterial aggregates, should be avoided to obtain a high GO concentration in the dispersions. This study paves the way towards the use of environmentally friendly dispersant agents instead of conventional organic solvents or synthetic surfactants to attain high-quality dispersions of carbon nanomaterials in water.

High Directional Water Transport Graphene Oxide Biphilic Stack

Understanding the nature of water transport in nanoscale is of high importance. Graphene properties such as mass flow rate, stability, filtration efficiency, and selectivity have been studied in various fields. It is a widely held view that the hydrophilicity of graphene oxide enhances the water transport properties. In this study, it is shown that despite this belief, a combination of graphene and graphene oxide can yield superior transport properties including high mass flow rate and directionality. Firstly, different membrane characteristics such as the smallest pore diameter for water molecules sieving and mass flow rate have been evaluated. Furthermore, a combination of graphene and graphene oxide, a biphilic stack of hydrophobic and hydrophilic layers, are used to evaluate the mass flow rates and results are compared with that of normal graphene oxide laminates. The proposed structure acts like a water diode i.e. conduct water molecules in a desired direction and increases the mass flow rate several times. The effect of interatomic potential, oxidation level and charge, and the spacing between layers on both mass flow rate and directionality are examined. It is found that an optimized structure conducts water in a desired direction and increases the mass flow rate up to 10 times for the small interlayer distance of 7 Å compared to the normal graphene oxide laminates. The given structures can be used in a wide range of filtration applications where selective water sieving with high mass flow rate is desired.

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

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

Dataset on in-vitro study of chitosan-graphene oxide films for regenerative medicine

Chitosan (CS) is well-known for its biological properties, especially its ability to induce tissue cicatrization. However, considerable research proved that CS presents a high inflammatory response and poor mechanical properties. For these reasons, we decided to use chitosan (CS) functionalized GO by a covalent bond (CS-GO). Due to the resistant structure of the GO and the high presence of oxygen functional groups on it, it will enhance the biocompatibility of the material. The data obtained in this investigation aimed to prove the possible application of CS-GO in regenerative medicine. For this reason, it was performed an In vitro analysis using brine shrimp to prove materials biocompatibility and gingival fibroblasts for a cell growth test.

A Review on Heavy Metal Ions and Containing Dyes Removal Through Graphene Oxide-Based Adsorption Strategies for Textile Wastewater Treatment

Textile wastewater heavy metal pollution has become a severe environmental problem worldwide. Metal ion inclusion in a dye molecule exhibits a bathochromic shift producing deeper but duller shades, which provides excellent colouration. The ejection of a massive volume of wastewater containing heavy metal ions such as Cr (VI), Pb (II), Cd (II) and Zn (II) and metal-containing dyes are an unavoidable consequence because the textile industry consumes large quantities of water and all these chemicals cannot be combined entirely with fibres during the dyeing process. These high concentrations of chemicals in effluents interfere with the natural water resources, cause severe toxicological implications on the environment with a dramatic impact on human health. This article reviewed the various metal-containing dye types and their heavy metal ions pollution from entryway to the wastewater, which then briefly explored the effects on human health and the environment. Graphene-based absorbers, specially graphene oxide (GO) benefits from an ordered structured, high specific surface area, and flexible surface functionalization options, which are indispensable to realize a high performance of heavy metal ion removal. These exceptional adsorption properties of graphene-based materials support a position of ubiquity in our everyday lives. The collective representation of the textile wastewater's effective remediation methods is discussed and focused on the GO-based adsorption methods. Understanding the critical impact regarding the GO-based materials established adsorption portfolio for heavy metal ions removal are also discussed. Various heavy-metal ions and their pollutant effect, ways to remove such heavy metal ions and role of graphene-based adsorbent including their demand, perspective, limitation, and relative scopes are discussed elaborately in the review.

An Exploration of Electrocatalytic Analysis and Antibacterial Efficacy of Electrically Conductive Poly (D-Glucosamine)/Graphene Oxide Bionanohybrid

The diversification of environment congenial and conservative nanocomposites is prestigious because of increasing contamination in biota. Poly (D-glucosamine), a natural biopolymer is contemplated as a promising biodegradable polysaccharide for various applications mainly in food packaging, bone substitutes, and water filtration. The drawback of poly (D-glucosamine) is nadir mechanical strength and high hydrophilicity which could be amended by the introduction of graphene oxide (GO) nanoparticles (shows excellent load transfer). Homogeneous distribution and well dispersion of GO nanoparticles in poly (D-glucosamine) matrix have been concluded by SEM investigation. Inclusions of 1% GO into the biopolymer matrix results in enhancement of 83.21 MPa of tensile strength in contrary to pristine poly (D-glucosamine). It can be elucidated that increment in properties is due to the crosslinking reaction takes place between the amine and epoxide moieties that exist within poly (D-glucosamine) matrix and GO respectively. The thermal stability of nanocomposites has been increased on addition of nanofiller confirmed by TGA analysis. The resultant nanocomposites were examined for antimicrobial screening against various contagious bacterial strains for packaging applications. Electrochemical characteristics and capacitive investigation of the composites were also studied using cyclic voltammetry and impedance (EIS) respectively. EIS elucidated that the nanocomposite modified electrode exhibited good capacitance behaviour with the Bode phase angle (-45°) which proves the candidates have good capacitive properties. The electrocatalytic properties are found to be diffusion controlled in alkaline medium with good electrical conductivity with low resistance. It is envisioned that the resultant bionanocomposite has potential applications in packaging industry.

Viral Filtration Using Carbon-Based Materials

Viral infections alone are a significant cause of morbidity and mortality worldwide and have a detrimental impact on global healthcare and socio‐economic development. The discovery of novel antiviral treatments has gained tremendous attention and support with the rising number of viral outbreaks. In this work, carbonaceous materials, including graphene nanoplatelets and graphene oxide nanosheets, were investigated for antiviral properties. The materials were characterized using scanning electron microscopy and transmission electron microscopy. Analysis showed the materials to be two‐dimensional with lateral dimensions ranging between 1 and 4 µm for graphene oxide and 110 ± 0.11 nm for graphene nanoplatelets. Antiviral properties were assessed against a DNA virus model microorganism at concentrations of 0.5, 1.0 and 2.0 wt/v%. Both carbonaceous nanomaterials exhibited potent antiviral properties and gave rise to a viral reduction of 100% across all concentrations tested. Graphene oxide nanosheets were then incorporated into polymeric fibres, and their antiviral behaviour was examined after 3 and 24 hr. A viral reduction of 39% was observed after 24 hr of exposure. The research presented here showcases, for the first time, the antiviral potential of several carbonaceous nanomaterials, also included in a carrier polymer. These outcomes can be translated and implemented in many fields and devices to prevent viral spread and infection.

Graphene oxide coated Titanium Surfaces with Osteoimmunomodulatory Role to Enhance Osteogenesis

Graphene oxide (GO) and its derivatives are currently being explored for the modification of bone biomaterials. However, the effect of GO coatings on immunoregulation and subsequent impacts on osteogenesis are not known. In this study, GO was coated on pure titanium using dopamine. GO-coated titanium (Ti-GO) surfaces exhibited good biocompatibility, with the ability to stimulate the expression of osteogenic genes, and extracellular matrix mineralization in human mesenchymal stromal cells (hMSCs). Interestingly, it was found that GO-coated surfaces could manipulate the polarization of macrophages and expression of inflammatory cytokines via the Toll-like receptor pathway. Under physiological conditions, Ti-GO activated macrophages and induced mild inflammation and a pro-osteogenic environment, characterized by a slight increase in the levels of proinflammatory cytokines, as well as increased expression of the TGF-β1 and oncostatin M genes. In an environment mimicking acute inflammatory conditions, Ti-GO attenuated inflammatory responses, as shown by the downregulation of proinflammatory cytokines. Conditioned medium collected from macrophages stimulated by Ti-GO played a significant stimulatory role in the osteogenic differentiation of hMSCs. In summary, GO-coated surfaces displayed beneficial immunomodulatory effects in osteogenesis, indicating that GO could be a potential substance for the modification of bone scaffolds and implants.

A study on preparation of modified Graphene Oxide and flame retardancy of polystyrene composite microspheres

In this paper, the ODOPM, a kind of 9, 10-dihydro-9-oxygen-heterooxy-10-phosphoro-10-oxygen (DOPO) derivative, was obtained by hydroxylation of DOPO. Further, a phosphorus nano-flame retardant (GO-ODOPM) was obtained by addition reaction with carboxylated Graphite Oxide (GO-COOH). And then Graphene Oxide/polystyrene (GO-ODOPM/PS) composite microspheres were obtained via suspension polymerization of styrene with GO-ODOPM. The decrease of the peak heat release rate (HRR) and total heat release rate (THR) for the GO-ODOPM/PS composite microspheres was obtained when the content of the additives was only 3.0 wt% is more than 36.2% and 33.6% compared with the pure PS microspheres, respectively. Thermogravimetric (TG), dynamic rheology and carbon residue analysis were used to study the flame-retardant mechanism of GO-ODOPM in PS microspheres. The results revealed that the addition of GO-ODOPM obviously reduced the fire hazard of polystyrene (PS) microspheres. Thus, this work provided a feasible method to design efficient flame retardants for enhancing fire safety of polymers.

Graphene oxide: A growth factor delivery carrier to enhance chondrogenic differentiation of human mesenchymal stem cells in 3D hydrogels

Cartilage engineering with stem cells in 3D scaffolds is a promising future therapy to treat cartilage defects. One challenge in the field is to design carriers to efficaciously deliver biological factors in 3D scaffolds containing stem cells to appropriately guide differentiation of these cells in same scaffolds and promote specific tissue synthesis. Graphene-based 2D nanomaterials have recently attracted extensive interest for their biomedical applications as they can adsorb a plethora of biological molecules, thus offering high potential as delivery carriers. This study utilized graphene oxide (GO) flakes to adsorb transforming growth factor β3 (TGF-β3), which were then incorporated into a collagen hydrogel. Human mesenchymal stem cells (hMSCs) were encapsulated in the same gel and chondrogenic differentiation assessed. The study showed GO flakes adsorbed > 99% TGF-β3 with <1.7% release. Adsorbed TGF-β3 retained a similar conformation to its dissolved counterpart (free protein) but importantly demonstrated greater conformational stability. Smad2 phosphorylation was promoted, and higher chondrogenic gene expression and cartilage-specific extracellular matrix deposition were achieved compared to exogenously delivering TGF-β3 in culture media. Effects were sustained in long-term 28-day culture. The results demonstrate GO flakes as highly-efficient for delivering GFs in 3D to guide cells in the same scaffold and induce tissue formation. The ability of GO flakes to provide sustained local delivery makes this material attractive for tissue engineering strategies, in particular for regionally-specific MSC differentiation (e.g. osteochondral tissue engineering). STATEMENT OF SIGNIFICANCE: Cartilage engineering involving stem cells in 3D scaffolds is a promising future therapy to treat cartilage defects which can lead to debilitating conditions such as osteoarthritis. However, this field faces the challenge to design delivery carriers to efficaciously deliver biological factors inside these 3D cell-containing scaffolds for appropriately-guided cell differentiation. Graphene-based 2D nanomaterials offer high potential as delivery carriers, but to date studies using them to deliver biological factors have been restricted to 2D substrates, non-scaffold cell masses, or acellular 3D scaffolds. Our study for the first time demonstrated simultaneously incorporating both human mesenchymal stem cells (hMSCs) and GO (graphene oxide)-adsorbed growth factor TGFβ3 into a 3D scaffold, where GO-adsorbed TGFβ3 enhanced chondrogenic differentiation of hMSCs and cartilage-tissue synthesis throughout the scaffold without needing to repeatedly supply TGFβ3 exogenously.

Electrical Property of Graphene and Its Application to Electrochemical Biosensing

Graphene, a single atom thick layer of two-dimensional closely packed honeycomb carbon lattice, and its derivatives have attracted much attention in the field of biomedical, due to its unique physicochemical properties. The valuable physicochemical properties, such as high surface area, excellent electrical conductivity, remarkable biocompatibility and ease of surface functionalization have shown great potentials in the applications of graphene-based bioelectronics devices, including electrochemical biosensors for biomarker analysis. In this review, we will provide a selective overview of recent advances on synthesis methods of graphene and its derivatives, as well as its application to electrochemical biosensor development. We believe the topics discussed here are useful, and able to provide a guideline in the development of novel graphene and on graphene-like 2-dimensional (2D) materials based biosensors in the future.

A label-free fluorescent aptasensor for the detection of Aflatoxin B1 in food samples using AIEgens and graphene oxide

The detection of Aflatoxin B1 (AFB1) has attracted extensive attention for food safety is a worldwide public health problem. Herein, a novel, simple and label-free fluorescent aptasensor, based on quaternized tetraphenylethene salt (TPE-Z), graphene oxide (GO) and AFB1 aptamer, has been constructed to detect AFB1. In the presence of AFB1, AFB1 aptamer undergoes a conformational switch from single stranded structure to the AFB1/AFB1 aptamer complex upon target binding, which induces the release of TPE-Z/AFB1 aptamer from the surface of GO. Thus, the fluorescence of TPE-Z/AFB1 aptamer is recovered. The assay can be performed by simply mixing TPE-Z, AFB1 aptamer, the GO and the AFB1 samples with a detection limit of 0.25 ng/mL. It is highly selective against other aflatoxins in foods and its performance has been verified in food samples (corn, milk and rice) with known concentration AFB1.

Bio-transformation of Graphene Oxide in Lung Fluids Significantly Enhances Its Photothermal Efficacy

Rationale: Graphene oxide (GO) has shown great promises in biomedical applications, such as drug delivery and thermotherapeutics, owing to its extraordinary physicochemical properties. Nonetheless, current biomedical applications of GO materials are premised on the basis of predesigned functions, and little consideration has been given to the influence of bio-transformation in the physiological environment on the physicochemical properties and predesigned functionalities of these materials. Hence, it is crucial to uncover the possible influence on GO's physicochemical properties and predesigned functionalities for better applications. Methods: Bio-transformed GOs were characterized by X-ray diffraction (XRD) spectra, Raman spectra, X-ray photoelectron spectroscopy (XPS) and Fourier transform infrared transmission (FT-IR) spectra. The morphologies of various GO materials were assessed via transmission electron microscopy (TEM), scanning electron microscopy (SEM) and atomic force microscopy (AFM) images. The photothermal (PTT) performance of different GO materials in vitro and in vivo were measured using 808 nm laser at a power density of 2 W/cm2. The PTT efficacy was determined using transplanted 4T1 cells-derived breast tumors in mice. Results: Bio-transformation of GO in the lung (a main target organ for GO to localize in vivo) can induce dramatic changes to its physicochemical properties and morphology, and consequently, its performances in biomedical applications. Specifically, GO underwent significant reduction in two simulated lung fluids, Gamble's solution and artificial lysosomal fluid (ALF), as evidenced by the increase of C/O ratio (the ratio of C content to O content) relative to pristine GO. Bio-transformation also altered GO's morphology, characterized by sheet folding and wrinkle formation. Intriguingly, bio-transformation elevated the PTT performance of GO in vitro, and this elevation further facilitated PTT-based tumor-killing efficacy in tumor cells in vitro and in a mouse model with transplanted tumors. Bio-transformation also compromised the interaction between drug with GO, leading to reduced drug adsorption, as tested using doxorubicin (DOX). Conclusions: Transformation in Gamble's solution and ALF resulted in varied degrees of improved performances of GO, due to the differential effects on GO's physicochemical properties. Our findings unveiled an overlooked impact of GO bio-transformation, and unearthed a favorable trait of GO materials in thermotherapeutics and drug delivery in the lung microenvironment.

Aptamer-Directed Specific Drug Delivery and Magnetic Resonance Imaging of Renal Carcinoma Cells In Vitro and In Vivo

Magnetic resonance imaging (MRI) with high spatial resolution has been widely used in clinics as a noninvasive diagnostic technology, and MRI diagnosis-based theranostic nanomaterials have attracted increasing attention. Herein, we report on the fabrication of a GO/BSA-Gd2O3/AS1411-DOX theranostic nanocomplex with BSA-Gd2O3 nanoparticles for use as an MRI contrast agent (CA), with graphene oxide (GO) nanoplates as the CA and drug nanocarrier, as well as an aptamer, AS1411, as the targeting molecule. The proposed theranostic nanocomplex not only provided stronger MR contrast enhancement but also inhibited the growth of 786-0 human renal carcinoma cells with the help of the AS1411 aptamer, while sparing the normal cells from harm, thus demonstrating their specific drug delivery capability. Additionally, 786-0 cells could be specifically recognized using the GO/BSA-Gd2O3/AS1411-DOX theranostic nanocomplex with MRI both in vitro and in vivo. Notably, most of the nanocomplex that was injected into the tail vein was excreted by the kidneys and bladder, while MRI signals from the nanocomplexes that accumulated specifically in the tumor region could remain as long as 24 hours, which is beneficial for future clinical diagnosis and therapy.

Biochemical and Histopathological Evaluation of Graphene Oxide in Sprague-Dawley Rats

Graphene and its derivatives are promising material for important biomedical applications due to their versatility. A detailed comprehensive study of the toxicity of these materials is required in context with the prospective use in biological setting. We investigated toxicity of Graphene Oxide (GO) in rats following exposure with respect to hepatotoxicity and oxidative stress biomarkers. Four groups of five male rats were orally administered GOs, once a day for five days, with doses of 10, 20 and 40mg/Kg GO. A control group consisted of five rats. Blood and liver were collected 24h after the last treatment following standard protocols. GO's exposure increased induction of Reactive Oxygen Species (ROS), activities of liver enzymes (Alanine ALT, Aspartate AST, Alkaline Phosphates ALP), concentration of Lipid Hydro Peroxide (LHP) and morphological alterations of liver tissue in exposed groups compared to control. The highest two doses, 20 and 40mg/kg, showed statistically significant (p<0.05) increases in the induction of ROS, activities of ALT, ALP, LHP concentration, and morphological alterations of liver tissue compared to control. However, AST activity showed no effect. The results of this study demonstrate that GO may be hepatotoxic, and its toxicity might be mediated through oxidative stress.

Bioconjugated graphene oxide-based Raman probe for selective identification of SKBR3 breast cancer cells

In this article, we demonstrate the use of bio-conjugated 2D graphene oxide (bio-GO) nanostructure to probe breast cancer cell (SKBR3) with excellent discrimination over other types of circulating tumor cells. We distinctly observed that bio-GO nanostructure targets and bind SKBR3 cell selectively in the cell mixture. Longer incubation of SKBR3 cell with bio-GO causes Raman signal "turn off" when excited with 532 nm laser. This is attributed to penetration of the bio-GO through the plasma membrane of the cell by generating transient hole. Extraction of GO after cell digestion also support the internalization rubric of 2D graphene through cell membrane. Our experimental data with the HaCaT healthy cell line, as well as with LNCaP prostate cancer cell line clearly demonstrated that this Raman scattering assay is highly selective to SKBR3. The mechanism of selectivity and the assay's response change have been verified and discussed utilizing fluorescence properties of GO and various other techniques. The experimental results open up a possibility of new label free Raman scattering assay, for reliable diagnosis of cancer cell lines by monitoring "turn-off" of the Raman signal from Bio-GO nanostructure.

A facile way to produce epoxy nanocomposites having excellent thermal conductivity with low contents of reduced graphene oxide

A well-dispersed phase of exfoliated graphene oxide (GO) nanosheets was initially prepared in water. This was concentrated by centrifugation and was mixed with a liquid epoxy resin. The remaining water was removed by evaporation, leaving a GO dispersion in epoxy resin. A stoichiometric amount of an anhydride curing agent was added to this epoxy-resin mixture containing the GO nanosheets, which was then cured at 90 °C for 1 h followed by 160 °C for 2 h. A second thermal treatment step of 200 °C for 30 min was then undertaken to reduce further the GO in situ in the epoxy nanocomposite. An examination of the morphology of such nanocomposites containing reduced graphene oxide (rGO) revealed that a very good dispersion of rGO was achieved throughout the epoxy polymer. Various thermal and mechanical properties of the epoxy nanocomposites were measured, and the most noteworthy finding was a remarkable increase in the thermal conductivity when relatively very low contents of rGO were present. For example, a value of 0.25 W/mK was measured at 30 °C for the nanocomposite with merely 0.06 weight percentage (wt%) of rGO present, which represents an increase of ~40% compared with that of the unmodified epoxy polymer. This value represents one of the largest increases in the thermal conductivity per wt% of added rGO yet reported. These observations have been attributed to the excellent dispersion of rGO achieved in these nanocomposites made via this facile production method. The present results show that it is now possible to tune the properties of an epoxy polymer with a simple and viable method of GO addition.

Nickel-Platinum Nanoparticles Supported on Zeolitic Imidazolate Framework/Graphene Oxide as High-Performance Adsorbents for Ambient-Temperature Hydrogen Storage

A facile liquid impregnation method followed by a reduction treatment was applied for loading transition metals nickel, nickel-platinum, and platinum into zeolitic imidazolate framework (ZIF-8)/graphene oxide (GO) as potential adsorbents for ambient-temperature hydrogen storage. These materials have been characterized by powder X-ray diffraction, infrared spectra, scanning electron microscopy, transmission electron microscopy, energy-dispersive X-ray spectroscopy, inductively coupled plasma-emission spectroscopy, and gas adsorption apparatus for their physical and chemical properties. The metal-doped ZIF-8/GO composites maintained the morphology of pristine ZIF-8, although their specific surface areas significantly decreased. The metal nanoparticles in the corresponding composites have average diameters of 4.2–5.1 nm, and uniformly located on the external surface and edges of ZIF-8/GO network. Hydrogen adsorption amounts on metal-doped samples were enhanced by factors of 2.3–3.8 times over ZIF-8 at 298 K due to the spillover effect. Notably, the Pt-doped ZIF-8/GO sample seems to be the best adsorbent for hydrogen storage because of the higher catalytic reactivity of platinum than nickel.

Graphene Oxide Induces Toxicity and Alters Energy Metabolism and Gene Expression in Ralstonia solanacearum

Graphene oxide (GO) is a promising material for development as an antibacterial, phytoprotective agent due to its contact-based antibacterial activity induced by its physical and chemical properties. However, the mechanism underlying the antibacterial effect of GO has yet to be elucidated. In the current study, we investigated the effects of GO on the phytopathogen R. solanacearum at the molecular level with a specific focus on energy metabolism. Under controlled conditions, the bacteriostatic and bactericidal actions of GO were investigated with respect to concentration, treatment time and rotation speed. Transmission electron microscopy (TEM) and destabilization assays revealed that GO caused injury to bacterial cell membrane structures. Furthermore, adenosine triphosphate (ATP) levels decreased after exposure to sheets of GO, while malondialdehyde levels significantly increased, indicating the occurrence of lipid oxidation. A series of genes related to bacterial virulence, motility and oxidative stress were selected to evaluate the molecular mechanism underlying GO’s effects on R. solanacearum. Using quantitative reverse transcription polymerase chain reaction (RT-qPCR), we showed that in the presence of GO, the expression levels of genes involved in virulence and motility were down regulated, with the exception of popA. The phcA, hrpB and flgG genes were significantly downregulated by 2.61-, 3.45- and 4.22-fold, respectively. Conversely, the expression levels of sodB, oxyR and dps, three important oxidative stress genes, were upregulated by 1.82-, 2.17-, and 3.79-fold, respectively. These findings confirmed that cell membrane damage and oxidative stress were responsible for the antibacterial actions of GO, in addition to disturbances to energy metabolism processes.

An end-point method based on graphene oxide for RNase H analysis and inhibitors screening

As a highly conserved damage repair protein, RNase H can hydrolysis DNA-RNA heteroduplex endonucleolytically and cleave RNA-DNA junctions as well. In this study, we have developed an accurate and sensitive RNase H assay based on fluorophore-labeled chimeric substrate hydrolysis and the differential affinity of graphene oxide on RNA strand with different length. This end-point measurement method can detect RNase H in a range of 0.01 to 1 units /mL with a detection limit of 5.0×10^-3 units/ mL under optimal conditions. We demonstrate the utility of the assay by screening antibiotics, resulting in the identification of gentamycin, streptomycin and kanamycin as inhibitors with IC₅₀ of 60±5µM, 70±8µM and 300±20µM, respectively. Furthermore, the assay was reliably used to detect RNase H in complicated biosamples and found that RNase H activity in tumor cells was inhibited by gentamycin and streptomycin sulfate in a concentration-dependent manner. The average level of RNase H in serums of HBV infection group was similar to that of control group. In summary, the assay provides an alternative tool for biochemical analysis for this enzyme and indicates the feasibility of high throughput screening inhibitors of RNase H in vitro and in vivo.

Non-Contact Local Conductance Mapping of Individual Graphene Oxide Sheets during the Reduction Process

We used electrostatic force microscopy (EFM) to investigate local conducting states of atomically thin individual graphene oxide (GO) sheets and monitor the spatial evolution of their conducting properties during the reduction process. Because of the thinness of the GO sheets and finite carrier density, the electric field is partially screened in the reduced GO, which is manifested in the EFM phase signals. We found inhomogeneous oxidation states in as-prepared GO sheets and followed the evolution of reduction process in the individual GO sheets during both thermal and chemical reduction. We also compared the EFM measurement results with simultaneous IV characteristics to assess correlations between two measurements.

Toxicity of multi-walled carbon nanotubes, graphene oxide, and reduced graphene oxide to zebrafish embryos

OBJECTIVE

This study was aimed to investigate the toxic effects of 3 nanomaterials, i.e. multi-walled carbon nanotubes (MWCNTs), graphene oxide (GO), and reduced graphene oxide (RGO), on zebrafish embryos.

METHODS

The 2-h post-fertilization (hpf) zebrafish embryos were exposed to MWCNTs, GO, and RGO at different concentrations (1, 5, 10, 50, 100 mg/L) for 96 h. Afterwards, the effects of the 3 nanomateria on spontaneous movement, heart rate, hatching rate, length of larvae, mortality, and malformations ls were evaluated.

RESULTS

Statistical analysis indicated that RGO significantly inhibited the hatching of zebrafish embryos. Furthermore, RGO and MWCNTs decreased the length of the hatched larvae at 96 hpf. No obvious morphological malformation or mortality was observed in the zebrafish embryos after exposure to the three nanomaterials.

CONCLUSION

MWCNTs, GO, and RGO were all toxic to zebrafish embryos to influence embryos hatching and larvae length. Although no obvious morphological malformation and mortality were observed in exposed zebrafish embryos, further studies on the toxicity of the three nanomaterials are still needed.