Fabrication of stem cell chip with peptide nanopatterned layer to detect cytotoxicity of environmental toxicants

A stem cell chip with peptide nanopatterned layer was fabricated to detect the effects of environmental toxins on human neural stem cells (HB1 x F3) electrochemically. The cell chip was recently developed as in vitro monitoring tool for determining the cell viability simply and rapidly compared to the conventional methods. However, cell chip composed of neural stem cells have not been reported due to the difficulties for maintaining its stemness and cell attachment on the artificial electrode surface, which is critical for sensitive detection of cell viability electrochemically. In this study, we fabricated peptide nanopatterned layer on gold electrode for increasing the affinity between the stem cell and an artificial electrode surface by self-assembly technique. After the confirmation of fabricated nanopatterned surface, neural stem cells were immobilized on chip surface and the viability was measured by electrochemical method. Thereafter, neural stem cells were treated with two kinds of common environmental toxins, and the intensities of reduction peak obtained by cyclic voltammetry (CV) were decreased with the increase of concentrations of environmental toxins. These electrochemical results were validated by 3-(4,5-Dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) assay. Our newly developed stem cell chip can be used as useful label-free analysis tool for detecting drug effects or for assessing the toxicity electrochemically.     

Ultrathin polyaniline film coated on an indium–tin oxide cell-based chip for study of anticancer effect

Polyaniline emeraldine base (EB) coated indium–tin oxide (ITO) electrode was prepared for the construction of a cell-based chip. Ultrathin polyaniline PANI film on an ITO was electroactive at neutral pH without co-deposition of an acidic counterion. HeLa cells were cultured on a PANI/ITO substrate and utilized to assess the biological toxicity of anticancer drugs. Cell growth, cell viability and drug-related cell toxicity were evaluated by a cyclic voltammetry (CV) method under a neutral pH. We demonstrated the functionality of a PANI coated ITO electrode for use as a cell chip and found that PANI was a good surface for the HeLa cells to grow without any significant morphological changes.     

Cell chip-based monitoring of toxic effects of cosmetic compounds on skin fibroblast cells

The present study estimated the efficacy of electrochemical detection of imidazolidinyl urea-induced cell toxicity in skin human fibroblast cells (HFF cells). The gold nanopunct structures were fabricated through a nanoporous alumina mask, and the structural formations were confirmed via scanning electron microscopy. The HFF cells were allowed to attach to RGD (Arg-Gly-Asp) peptide nanopatterned surfaces, and electrochemical tools were applied to skin cells attached to the chip surface. The HFF cells evidenced inflammation responses to allergens such as imidazolidinyl urea. The cells were subsequently treated with different concentrations of imidazolidinyl urea for 24 h in culture, which induced a change in the cyclic voltammetry (CV) current peak. Treatment with imidazolidinyl urea induced a loss of cell viability and accelerated inflammation in a concentration-dependent manner. The expression level of inflammation-related proteins such as IL-1 beta were increased in imidazolidinyl urea-treated cells. The CV results demonstrated that imidazolidinyl urea significantly reduced the current peaks in a dose-dependent manner. The results showed that the current peak was reduced in accordance with the increases in imidazolidinyl urea-induced inflammation. In conclusion, the results of this study suggest that the electrochemical-based chip provides crucial information for improvements to a cell chip system for drug screening applications.     

CuS nanoplatelets arrays grown on graphene nanosheets as advanced electrode materials for supercapacitor applications

CuS nanoplatelets arrays grown on graphene nanosheets are successfully synthesized via a facile low-temperature solvothermal reaction with graphene oxide (GO), CH₃CSNH₂ and Cu(CH₃COO)₂·H₂O as the reactants. CH₃CSNH₂ plays an important role in being the reducing agent for GO and the sulfur source of CuS. Supercapacitive performance of the graphene/CuS nanocomposite as active electrode materials has been evaluated by cyclic voltammetry, galvanostatic charge-discharge and electrochemical impedance spectroscopy measurements. The results indicate that graphene/CuS electrode delivers a high capacitance of 497.8 F g^–1 at a current density of 0.2 A g^–1, which outperforms bare CuS electrode. This excellent performance is ascribed to the short diffusion path and large surface area of the unique hierarchical nanostructure with nanoflakes building blocks for bulk accessibility of faradaic reaction.     

Simultaneous functionalization and reduction of graphene oxide with diatom silica

The simultaneous coupling and reduction of graphene oxide (GO) with diatom silica (Amphora sp., Navicula ramossisira and Skeletonema sp.) were demonstrated in this work. Binding of GO with diatom silica via direct esterification reaction at 100 °C was observed as well as the reduction of GO. The Raman spectra of GO-diatom silica revealed the typical peaks for reduced graphene oxide at 1350 cm^?1 (D band) and 1585 cm^?1 (G band). Infrared spectroscopy also showed the presence of a unique peak at 1260–1300 cm^?1 indicative of Si–O–C=O bond formation. This confirms the successful functionalization of GO with silica. Scanning electron microscopy showed the presence of GO on the diatom. For the pennate diatoms, Amphora sp. and N. ramossisira, their pores were closed demonstrating that GO was able to cover the surface of the diatom via the Si–O–C bond formation. For the centric diatom, Skeletonema sp., GO was found to be on its rib cage-like body structure and on its centric top. Electrochemical measurements by cyclic voltammetry using a redox probe, K₃[Fe(CN)₆], showed that GO-Amphora and GO-Navicula had more surface negative charge compared with bare GO or bare diatom silica. Furthermore, they demonstrated similar surface charge characteristics as the chemically reduced GO (by hydrazine hydrate). This implies that the composite (reduced GO-diatom) can possibly replace chemically reduced GO (by exposure to hydrazine vapor) and it could probably function as an electrode in sensing cationic biomolecules.     

Scaly Graphene Oxide/Graphite Fiber Hybrid Electrodes for DNA Biosensors

The demand for a highly sensitive and stable DNA biosensor that can be used for implantable or on‐time monitoring is constantly increasing. In this work, for the first time graphene oxide (GO) sheets are synthesized in situ at the surface of graphite fibers to yield scaly GO/graphite fiber hybrid electrodes. The partially peeled GO sheets, directly connected with the graphite fibers, not only provide a large number of binding sites for single‐stranded DNA, but also favor high electron transfer rates from GO to the graphite fibers. Cyclic voltammetry (CV) confirms that the scaly GO/graphite fiber hybrid electrode has excellent electrochemical activity. As a working electrode in an electrochemical impedance DNA biosensor, the fiber hybrid electrode exhibits high selectivity, sensitivity, and stability. Due to its simplicity, low cost, high stability, small size, and unique microfiber morphology, the scaly GO/graphite fiber hybrid electrode is an excellent candidate for an implantable biosensor. The method developed here could have a profound impact on the design of GO‐based biosensors for DNA detection.     

硫氮共掺杂石墨烯修饰电极的制备及电化学性能研究

以天然鳞片石墨为原料,采用改进的Hummers法制备了氧化石墨(GO),以GO和硫氰酸铵为前驱体,采用一步水热法制备了硫氮共掺杂石墨烯(SNG)。X射线衍射、扫描电子显微镜和拉曼光谱分析结果显示,硫和氮成功掺入石墨烯晶格中,SNG表面褶皱明显且形成了三维孔道结构。通过交流阻抗、循环伏安法和差分脉冲伏安法考察了对苯二酚(HQ)、邻苯二酚(CC)和间苯二酚(RC)在修饰玻碳电极(SNG-180/GCE)上的电化学行为。结果表明:硫氮共掺杂能有效改善石墨烯的电化学性能,修饰电极实现了对HQ、CC和RC的同时检测,线性范围在5.5~43.06μmol/L和90.91~245.28μmol/L之间,检出限为1.83μmol/L(信噪比为3)。     

Facile one-step hydrothermal synthesis of reduced graphene oxide/Co3O4 composites for supercapacitors

This paper reports a facile one-step hydrothermal treatment of graphene oxide (GO) and cobalt acetate (Co(Ac)₂) for preparing reduced GO (rGO)/Co₃O₄ composites which were used as electrode materials for supercapacitors containing electrolytes of 2 M KOH aqueous solution. The morphologies and structures of rGO/Co₃O₄ composites were characterized by X-ray diffraction, scanning electron microscopy, transmission electron microscopy, Raman spectrum, and N₂ adsorption–desorption isotherms. The electrochemical performances of two-electrode supercapacitors were evaluated by cyclic voltammetry, galvanostatic charge–discharge, and electrochemical impedance spectroscopy techniques. During the hydrothermal reaction, GO was reduced and 10–30 nm-sized Co₃O₄ nanoparticles were in situ grown onto the rGO sheets simultaneously. The effects of mass ratios of GO and Co(Ac)₂ on the performances of supercapacitors were investigated. In comparison with pure Co₃O₄-based supercapacitor, supercapacitors based on rGO/Co₃O₄ composites show better performances because both the specific surface areas and the electrical conductivities of electrode materials were increased by the introduction of rGO. When the mass ratio of GO and Co(Ac)₂ is 1:2, rGO/Co₃O₄ composite electrode exhibits the highest capacitance of 263.0 F/g at a constant current density of 0.2 A/g in a two-electrode supercapacitor. In addition, the supercapacitor shows high rate capability and long cyclic durability.     

Ni2CoS4/还原氧化石墨烯/多孔还原氧化石墨烯的制备及其在超级电容器中的应用

采用水热法制备Ni_2CoS_4活性材料,通过物理过程和水热反应将其与氧化石墨烯(GO)、水热多孔氧化石墨烯(HHGO)复合得到Ni_2CoS_4/还原氧化石墨烯/多孔还原氧化石墨烯(Ni_2CoS_4/RGO/HRGO)复合电极材料。采用X射线衍射仪(XRD)、扫描电子显微镜(SEM)、循环伏安测试、恒流充放电测试和交流阻抗测试等,对复合材料的形貌结构、电化学性能进行了表征。研究结果表明:在1 A/g的电流密度下,其比电容为1 684 F/g,在5 A/g的电流密度下循环2 000次后,其比电容保持率为91.8%。Ni_2CoS_4/RGO/HRGO优良的电化学行为归因于这种复合结构使电解液对电极材料的润湿程度提高,进而提高了离子和电荷的传输速率,同时也缓解石墨烯、Ni_2CoS_4的团聚和循环过程中的体积变化。因此,Ni_2CoS_4/RGO/HRGO是一种有良好应用前景的高性能超级电容器电极材料。     

Iron oxide/gold nanoparticles‐decorated reduced graphene oxide nanohybrid as the thermo‐radiotherapy agent

The main focus of the current study is the fabrication of a multifunctional nanohybrid based on graphene oxide (GO)/iron oxide/gold nanoparticles (NPs) as the combinatorial cancer treatment agent. Gold and iron oxide NPs formed on the GONPs via the in situ synthesis approach. The characterisations showed that gold and iron oxide NPs formed onto the GO. Cell toxicity assessment revealed that the fabricated nanohybrid exhibited negligible toxicity against MCF‐7 cells in low doses (<50 ppm). Temperature measurement showed a time and dose‐dependent heat elevation under the interaction of the nanohybrid with the radio frequency (RF) wave. The highest temperature was recorded using 200 ppm concentration nanohybrid during 40 min exposure. The combinatorial treatments demonstrated that the maximum cell death (average of 53%) was induced with the combination of the nanohybrid with RF waves and radiotherapy (RT). The mechanistic study using the flow cytometry technique illustrated that early apoptosis was the main underlying cell death. Moreover, the dose enhancement factor of 1.63 and 2.63 were obtained from RT and RF, respectively. To sum up, the authors’ findings indicated that the prepared nanohybrid could be considered as multifunctional and combinatorial cancer therapy agents.Inspec keywords: radiation therapy, toxicology, gold, biomedical materials, nanofabrication, nanoparticles, iron compounds, cancer, nanomedicine, cellular biophysics, tumours, graphene compounds, biothermicsOther keywords: graphene oxide nanohybrid, combinatorial cancer treatment agent, cell toxicity assessment, MCF‐7 cells, dose‐dependent heat elevation, multifunctional cancer therapy agents, thermoradiotherapy agent, graphene oxide‐iron oxide‐gold nanoparticles, temperature measurement, radiofrequency wave, flow cytometry, time 40.0 min, CO‐FeO‐Au     

Effect of Graphene Oxide as a Dopant on the Electrochemical Performance of Graphene Oxide/Polyaniline Composite

A method for preparing a graphene oxide/polyaniline （GO/PANI） composite electrode was developed to investigate the effect of GO doped in PANI. PANI was first prepared by the polymerisation of aniline and then dedoped by NH4OH to form emeraldine base （EB）. The dedoped PANI and as-prepared GO were dissolved in N-methyl-2-pyrrolidone （NMP） to generate a homogeneous dispersion. The GO/PANI composites were redoped in HCI before use as electrode materials. These composites were characterised by Raman spectroscopy, X-ray diffraction, UV-vis adsorption spectroscopy, scanning electron microscopy, atomic force microscopy and electrochemical measurements. The GO/PANI composite electrode （containing 2.5% GO） has an initial gravimetric capacitance of 896 F g-1 at a scan rate of 5 mV s-1 and a retention life of 51% after 500 cycles, which is an improvement over that of pure PANI （23%）. The results show that the synergy of GO and PANI attributes to the good electrochemical performance of the GO/PANI composite electrode.     

Mechanism of cellular uptake of graphene oxide studied by surface-enhanced Raman spectroscopy

The last few years have witnessed rapid development of biological and medical applications of graphene oxide (GO), such as drug/gene delivery, biosensing, and bioimaging. However, little is known about the cellular uptake mechanism and pathway of GO. In this work, surface-enhanced Raman scattering (SERS) spectroscopy is employed to investigate the cellular internalization of GO loaded with Au nanoparticles (NPs) by Ca Ski cells. The presence of Au NPs on the surface of GO enables detection of enhanced intrinsic Raman signals of GO inside the cell. The SERS results reveal that GO is distributed inhomogeneously inside the cell. Furthermore, internalization of Au-GO into Ca Ski cells is mainly via clathrin-mediated endocytosis, and is an energy-dependent process.     

Nanofabrication of bio-self assembled monolayer and its electrochemical property for toxicant detection

Cyclic voltammetry (CV) has been used to investigate the electrochemical behavior of a glutathione (GSH) self assembled monolayer on modified gold electrodes (Bio-SAM). The GSH monolayer exhibits an influence on electrode surface activity. Electrochemically immobilized dsDNA onto a Cyt c/GSH-SAM/Au electrode, which is useful for the fabrication of a nanobiosensing device. The immobilized Cyt c followed by dsDNA immobilized films maintained its surface activity and finally dsDNA/Cyt c/GSH-SAM/Au electrode, targeted for the detection of toxicants. The films were characterized by CV, DPV, and AFM. The differential pulse voltammetry (DPV) technique was applied to detect three kinds of common toxins, 2-aminoanthracene (2-AA), 3-bromobenzanthrone (3-BBA) and bisphenol A (BPhA). The electrochemical signals showed good inverse relationship with the increase of concentrations of toxicants. Our proposed system based on electrochemical method with nanoscale film technology can be applied at highly sensitive biosensor for detecting various toxic chemicals.     

A sensitive electrochemical detection of hydroquinone using newly synthesized α-Fe<Subscript>2</Subscript>O<Subscript>3</Subscript>-graphene oxide nanocomposite as an electrode material

This article presents the effect of hematite phase iron oxide (α-Fe₂O₃) on the electrocatalytic activity of graphene oxide (GO) for electrochemical detection of hydroquinone in aqueous solution. The different weight percentage (wt%) (1, 2 and 3%) of α-Fe₂O₃ added GO nanocomposites were synthesized by wet-impregnation method. The cyclic voltammetry studies using 2% α-Fe₂O₃-GO modified glassy carbon electrodes was found to exhibit an excellent electrocatalytic activity than α-Fe₂O₃ and GO electrodes that may be due to the synergistic effect of α-Fe₂O₃nanoparicles and GO sheet. In addition, the modified electrode exhibited a good reproducibility as well as long-term stability. Hence, the 2% α-Fe₂O₃-GO can be a promising catalytic material for electrochemical sensor applications.     

Facile patterning of reduced graphene oxide film into microelectrode array for highly sensitive sensing

In this study, we develop a new technique to fabricate a reduced graphene oxide (rGO)-based microelectrode array (MEA) with low-cost soft lithography. To prepare patterned rGO, a polydimethylsiloxane (PDMS) mold with an array of microwells on its surface is fabricated using soft lithography, and GO is assembled on an indium tin oxide (ITO) electrode with a layer-by-layer method. The rGO pattern is formed by closely contacting the assembled GO film onto the ITO electrode with the PDMS mold filled with hydrazine solution in the microwells to selectively reduce the localized GO into the rGO. The MEA with patterned rGO as the microelectrode is characterized with Kelvin probe force microscopy (KFM), atomic force microscopy (AFM), and cyclic voltammetry (CV) with ferricyanide in aqueous solution as the redox probe. The KFM and AFM results demonstrate that each rGO pattern prepared under the present conditions is 3 μm in diameter, which is close to that of the PDMS mold we use. The CV results show that the rGO patterned onto the ITO exhibits a sigmoid-shaped voltammogram up to 200 mVs(-1) with a microampere level current response, suggesting that the rGO-based electrode fabricated with soft lithography behalves like a MEA. To demonstrate the potential electroanalytical application of the rGO-based MEA, prussian blue (PB) is electrodeposited onto the rGO-based MEA to form the PB/rGO-based MEA. Electrochemical studies on the formed PB/rGO-based MEA reveal that MEA shows a lower detection limit and a larger current density for the detection of H(2)O(2), as compared with the macroscopic rGO electrode. The method demonstrated here provides a simple and low-cost strategy for the fabrication of graphene-based MEA that are useful for electroanalytical applications.     

石墨烯/银纳米颗粒复合材料的制备及其对双氧水的电化学检测

以氧化石墨烯(GO)和硝酸银为原材料,聚乙烯吡咯烷酮(PVP)为还原剂和稳定剂,通过水热法制备出还原氧化石墨烯/银纳米颗粒(rGO/AgNPs)复合材料。采用透射电子显微镜(TEM)、X射线衍射(XRD)及紫外-可见分光光度计(UV-Vis)对rGO/AgNPs复合材料的形貌、组成和结构进行表征。同时,将rGO/AgNPs复合材料修饰到玻碳电极表面制备出过氧化氢(H_2O_2)电化学传感器,通过循环伏安法(CV)和计时安培响应法(i-t)对传感器进行电化学性能测试。实验结果表明:制备的rGO/AgNPs传感器具有较好的电化学性能,其对H_2O_2检测的灵敏度为340.6μA·(mmol/L)~(-1)·cm~(-2),响应时间为3s,最低检测极限为7.5μmol/L(S/N=3),线性检测范围为20~4950μmol/L(线性相关系数为R=0.9973)。     

Facile synthesis of poly(Safranine T)/Reduced graphene oxide nanocomposite for supercapacitors with wide potential window in aqueous neutral electrolyte

A facile method is introduced for incorporating reduced graphene oxide (rGO) into poly(safranine T) (PST) films. First, ST-functionalized GO (ST/GO) was obtained via the absorption of ST on GO in pH 7.0 phosphate buffer solution. Then rGO/PST composite was synthesized by the electropolymerization of ST and the subsequent electrochemical reduction of GO. The as-prepared PST/rGO composite films are characterized using scanning electron microscope, X-ray diffraction, and Fourier transform–infrared spectroscopy. PST/rGO composites possess a microporous structure, which creates enormous amount of pores, and therefore provides larger interfaces for charge carrier. The properties of electrochemical capacitance for PST/rGO composites have also been investigated with cyclic voltammetry (CV) and galvanostatic charge–discharge measurements. The experimental results manifest that the PST/rGO composite showed high capacitance (293.2 F g^?1) at 20-mV s^?1 CV scan and an excellent cycling stability (8.3% drop after 1000 cycles) in 0.1 M Na₂SO₄ electrolyte.     

Surface Coating‐Dependent Cytotoxicity and Degradation of Graphene Derivatives: Towards the Design of Non‐Toxic,Degradable Nano‐Graphene

With the increasing interests of using graphene and its derivatives in the area of biomedicine, the systematic evaluation of their potential risks and impacts to biological systems is becoming critically important. In this work, we carefully study how surface coatings affect the cytotoxicity and extracellular biodegradation behaviors of graphene oxide (GO) and its derivatives. Although naked GO could induce significant toxicity to macrophages, coating those two‐dimensional nanomaterials with biocompatible macromolecules such as polyethylene glycol (PEG) or bovine serum albumin (BSA) could greatly attenuate their toxicity, as independently evidenced by several different assay approaches. On the other hand, although GO can be gradually degraded through enzyme induced oxidization by horseradish peroxidase (HRP), both PEG and BSA coated GO or reduced GO (RGO) are rather resistant to HRP‐induced biodegradation. In order to obtain biocompatible functionalized GO that can still undergo enzymatic degradation, we conjugate PEG to GO via a cleavable disulfide bond, obtaining GO‐SS‐PEG with negligible toxicity and considerable degradability, promising for further biomedical applications.     

Reduced graphene oxide supersonically sprayed on wearable fabric and decorated with iron oxide for supercapacitor applications

We demonstrate the fabrication of wearable supercapacitor electrodes.The electrodes were applied to wearable fabric by supersonically spraying the fabric with reduced graphene oxide(rGO)followed by decoration with iron oxide(Fe2O3)nanoparticles via a hydrothermal process.The integration of iron oxide with rGO flakes on wearable fabric demonstrates immense potential for applications in high-energy-storage devices.The synergetic impact of the intermingled rGO flakes and Fe2O3 nanoparticles enhances the charge transport within the composite electrode,ultimately improving the overall electrochemical performance.Taking advantage of the porous nature of the fabric,electrolyte diffusion into the active rGO and Fe2O3 materials was significantly enhanced and subsequently increased the electrochemical interfacial activities.The effect of the Fe2O3 concentration on the overall electrochemical performance was investigated.The optimal composition yields a specific capacitance of 360 F g-1 at a current density of 1A g-1 with a capacitance retention rate of 89％after 8500 galvanostatic cycles,confirming the long-term stability of the Fe2O3/rGO fabric electrode.     

有机体系中聚苯胺电化学性能研究

有机体系中，采用循环伏安法（CV）在铂片表面电聚合制备聚苯胺，并通过循环伏安、恒流充放电测试了聚苯胺的电化学特性，结果表明：聚苯胺电极的循环伏安曲线呈现矩形特征，恒流充放电的电压和时间关系为线性关系。说明该电极具有典型的电容行为，其比电容高达320．8F／g。CV循环500圈后比电容基本没有变化，电极的循环寿命较高。