Redox Center Of Glucose Oxidase Research Articles

A high-power hybrid carbon nanotube/three-dimensional reduced graphene oxide glucose/O2 enzymatic biofuel cell

Long-lasting, high-performance enzymatic biofuel cells (EBFCs) are among the most promising candidates for renewable and green power generation. There are two main drawbacks to EBFCs: 1) short enzyme lifetime due to the enzyme's (protein) denaturation; and 2) low electron transfer efficiency as the enzyme's active site is deeply buried inside the non-conductive protein structure of the enzyme. In this study, a hybrid of carbon nanotubes (CNT) and three-dimensional graphene (3DG) was used to immobilize the glucose oxidase (GOx) on the surface of a glassy carbon electrode (GCE) to fabricate a modified bioanode in a glucose/O2 EBFC. This facile and low-cost CNT/3DG hybrid is a solution to the problems of instability, short lifespan, and poor electron transport in EBFCs. The exceptional electrocatalytic activity of the porous CNT/3DG hybrid is demonstrated by its effective immobilization of GOx and ability to collect energy from glucose oxidation by direct electron transfer (DET) while preserving the structure of the enzyme. The CNT acts like a tiny electrical wire that reaches and harvests the electron directly from the flavin adenine dinucleotide (FAD) (the redox center of GOx) and transfers it to the electrode surface, thus enhancing the performance of the EBFC. The immobilized GOx lifetime was increased to 210 days with a maximum power density of 253.36 µWcm-2 at 0.65 V. These results demonstrate the attractive capability of the CNT/3DG hybrid in the development of efficient biofuel cells and biosensors that employ enzymes in their structures.

Research on direct electron transfer of native glucose oxidase at PEDOT:PSS hydrogels modified electrode

Direct electron transfer (DET) is the critical issue in developing the third-generation glucose biosensor. However, the DET of glucose oxidase (GOx) is hard to realize because the redox center of GOx is located deeply within the enzyme molecule. Here, we have studied DET of GOx on a poly(3,4-ethylene dioxythiophene): poly(styrene sulfonate) (PEDOT:PSS) hydrogels decorated carbon nanotube fiber (CNTF) electrode with oxygen-independence glucose determination performance. PEDOT:PSS hydrogels modified on carbon nanotube fiber by electrogelation might play a key role in keeping the catalytic activity and DET for GOx simultaneously. The cyclic voltammetric result of the biosensor shows a pair of well-defined and quasi-reversible redox peaks with a formal potential of −0.431 V and a peak-to-peak separation of 69 mV. The constructed biosensor shows a linear range from 0.05 to 0.5 mM and a sensitivity of 43.52 μA mM−1 cm−2 toward glucose via a constant potential of −0.3 V in an N2-saturated solution. Three GOx models on the electrode surface are proposed to explain these DET-related electrochemical performances of the biosensor. We demonstrate the DET for the native GOx with catalytic activity in PEDOT:PSS hydrogels, which takes a step towards developing the third-generation glucose biosensor with conductive hydrogels.

Hybrid catalyst cascade for enhanced oxidation of glucose in glucose/air biofuel cell

Redox enzymes are capable of harvesting electrical energy from biofuels in high catalytic activity and under mild condition. However, it is difficult to achieve efficient electron transfer and deep oxidation of biofuels simultaneously in a single-enzyme catalytic system. Herein, we report a hybrid catalyst cascade consisting of an organic oxidation catalyst, 2,2,6,6-tetramethyl-1-piperidine N-oxyl (TEMPO), and an enzyme, glucose oxidase (GOx), for electrochemical oxidation of glucose. It is found that TEMPO is capable of mediating electron transfer between the redox center of GOx and the electrode surface. While glucose can be oxidized into glucuronic acid under neutral conditions. Thus, combining GOx and TEMPO, we are able to achieve 4e- electrooxidation of glucose using the hybrid enzymatic and organic cascade (HEOC) system. When coupled with an air-breathing Pt cathode, the resulting glucose/air biofuel cell using the proposed HEOC anode exhibits a maximum power density of 38.1 μW cm−2 with a short-circuit current of 651.4 μA cm−2, which can be attributed to the enhanced energetic efficiency, enabling TEMPO a promising catalyst for glucose oxidation in bioelectronics applications.

Ferrocene-Modified Polyelectrolyte Film-Coated Electrode and Its Application in Glucose Detection.

A polyelectrolyte film-coated electrode for the quantitative detection of glucose was reported. Carbon nanotubes, graphene oxide and polyelectrolyte with a ferrocenyl group were used to modify an enzyme electrode to facilitate the electron transfer between glucose oxidase and the electrode. Cyclic voltammetry and amperometric methods were adopted to investigate the effects of different polyelectrolytes and carbon nanomaterials on the electrochemical properties of enzyme electrodes. The results indicate that the ferrocenyl groups on a polyelectrolyte skeleton act as a mediator between the redox center of glucose oxidase and the electrode, which efficiently enhances the electron transfer between a glassy carbon electrode and glucose oxidase. The calibration curve of the sensor shows a linear range from 0.2 to 5 mM for glucose response. The sensor can achieve 95% of the steady-state current within 10 s. The electrodes also present high operational stability and long-term storage stability.

Reduced graphene oxide doping with nanometer-sized ferrocene moieties – New active material for glucose redox sensors

Herein, we present that the reduced graphene oxide (rGO) doped with nanometer-sized ferrocene moieties is a new, excellent active material for redox sensors. Two distinct approaches were utilized for the modification of rGO. The first method was based on the covalent decoration of rGO via the addition of azomethine ylide generated from the ferrocenecarboxaldehyde oxime. The second approach utilized the adsorption of 1,1′-ferrocenedicarboxylic acid on the graphene sheet via the π-π stacking. The morphology of the synthesized graphene materials was studied by application of microscopic techniques, whereas the Raman data allowed the characteristics of the tested materials in terms of their structural properties. The tested graphene materials doped with ferrocene moieties were used as a bioactive platform for glucose oxidase (GOx) immobilization. The enzyme was immobilized onto the rGO materials in two ways: (i) using a crosslinking agent – glutaraldehyde (GA) and (ii) by formation of the amide bonds between carboxylic groups of rGO-Fc(COOH)2 and amine groups from enzyme. Ferrocene moieties present at the graphene surface play the role of mediator in the electron transfer between the redox center of GOx and the electrode surface. The functionality of the constructed biosensors has been tested on real samples. The results of the recovery rates showed a satisfying degree of accuracy toward determination of glucose concentration. Examination of the potential interfering species has demonstrated favorable sensitivity and selectivity of the designed biosensor for the detection of glucose.

Voltammetric aptasensor for sulfadimethoxine using a nanohybrid composed of multifunctional fullerene, reduced graphene oxide and Pt@Au nanoparticles, and based on direct electron transfer to the active site of glucose oxidase.

This work describes a voltammetric and ultrasensitive aptasensor for sulfadimethoxine (SDM). It is based on signal amplification by making use of a multifunctional fullerene-doped reduced graphene oxide nanohybrid. The nanohybrid was coated with poly(diallyldimethylammonium chloride) to obtain a material (P-C60-rGO) with large specific surface area and a unique adsorption ability for loading it with glucose oxidase (GOx). The coating also facilitates the direct electron transfer between the active site of GOx and the glassy carbon electrode (GCE). The P-C60-rGO were then modified with Pt@Au nanoparticles, and the thiolated SDM-binding aptamer was immobilized on the nanoparticles. On exposure of the modified GCE to a solution containing SDM, it binds to the aptamer. The results were recorded through the signal responses generated from the redox center of GOx (FAD/FADH2) by cyclic voltammetry at a scan rate of 100mV·s-1 from -0.25 to -0.65V. Accordingly, The sensor has good specificity and stability, and response is linearin the 10fg·mL-1 to 50ng·mL-1 SDM concentration range with a detection limit of 8.7fg·mL-1. Graphical abstract Schematic presentation of an electrochemical aptasensor for sulfadimethoxine (SDM) using multifunctional fullerene-doped graphene (C60-rGO) nanohybrids for amplification. The limit of detection for SDM is as low as 8.7fg·mL-1.

ZnO-nanorods/graphene heterostructure: a direct electron transfer glucose biosensor.

ZnO-nanorods/graphene heterostructure was synthesized by hydrothermal growth of ZnO nanorods on chemically reduced graphene (CRG) film. The hybrid structure was demonstrated as a biosensor, where direct electron transfer between glucose oxidase (GOD) and electrode was observed. The charge transfer was attributed to the ZnO nanorod wiring between the redox center of GOD and electrode, and the ZnO/graphene heterostructure facilitated the transport of electrons on the hybride electrode. The glucose sensor based on the GOD-ZnO/CRG/Pt electrode had a high sensitivity of 17.64 μA mM−1, which is higher than most of the previously reported values for direct electron transfer based glucose biosensors. Moreover, this biosensor is linearly proportional to the concentration of glucose in the range of 0.2–1.6 mM. The study revealed that the band structure of electrode could affect the detection of direct electron transfer of GOD, which would be helpful for the design of the biosensor electrodes in the future.

New Insights into the Analysis of the Electrode Kinetics of Flavin Adenine Dinucleotide Redox Center of Glucose Oxidase Immobilized on Carbon Electrodes

New insights into electrochemical kinetics of the flavin adenine dinucleotide (FAD) redox center of glucose-oxidase (GlcOx) immobilized on reduced graphene oxide (rGO), single- and multiwalled carbon nanotubes (SW and MWCNT), and combinations of rGO and CNTs have been gained by application of Fourier transformed AC voltammetry (FTACV) and simulations based on a range of models. A satisfactory level of agreement between experiment and theory, and hence establishment of the best model to describe the redox chemistry of FAD, was achieved with the aid of automated e-science tools. Although still not perfect, use of Marcus theory with a very low reorganization energy (≤0.3 eV) best mimics the experimental FTACV data, which suggests that the process is gated as also deduced from analysis of FTACV data obtained at different frequencies. Failure of the simplest models to fully describe the electrode kinetics of the redox center of GlcOx, including those based on the widely employed Laviron theory is demonstrated, as is substantial kinetic heterogeneity of FAD species. Use of a SWCNT support amplifies the kinetic heterogeneity, while a combination of rGO and MWCNT provides a more favorable environment for fast communication between FAD and the electrode.

Glucose Oxidase/Cellulose–Carbon Nanotube Composite Paper as a Biocompatible Bioelectrode for Biofuel Cells

Biofuel cells are devices for generating electrical energy directly from chemical energy of renewable biomass using biocatalysts such as enzymes. Efficient electrical communication between redox enzymes and electrodes is essential for enzymatic biofuel cells. Carbon nanotubes (CNTs) have been recognized as ideal electrode materials because of their high electrical conductivity, large surface area, and inertness. Electrodes consisting entirely of CNTs, which are known as CNT paper, have high surface areas but are typically weak in mechanical strength. In this study, cellulose (CL)-CNT composite paper was fabricated as electrodes for enzymatic biofuel cells. This composite electrode was prepared by vacuum filtration of CNTs followed by reconstitution of cellulose dissolved in ionic liquid, 1-ethyl-3-methylimidazolium acetate. Glucose oxidase (GOx), which is a redox enzyme capable of oxidizing glucose as a renewable fuel using oxygen, was immobilized on the CL-CNT composite paper. Cyclic voltammograms revealed that the GOx/CL-CNT paper electrode showed a pair of well-defined peaks, which agreed well with that of FAD/FADH2, the redox center of GOx. This result clearly shows that the direct electron transfer (DET) between the GOx and the composite electrode was achieved. However, this DET was dependent on the type of CNTs. It was also found that the GOx immobilized on the composite electrode retained catalytic activity for the oxidation of glucose.

Facile Fabrication of a Graphene‐based Electrochemical Biosensor for Glucose Detection

AbstractA simple and effective glucose biosensor based on immobilization of glucose oxidase (GOD) in graphene (GR)/Nafion film was constructed. The results indicated that the immobilized GOD can maintain its native structure and bioactivity, and the GR/Nafion film provides a favorable microenvironment for GOD immobilization and promotes the direct electron transfer between the electrode substrate and the redox center of GOD. The electrode reaction of the immobilized GOD shows a reversible and surface‐controlled process with the large electron transfer rate constant (ks) of 3.42±0.08 s−1. Based on the oxygen consumption during the oxidation process of glucose catalyzed by the immobilized GOD, the as‐prepared GOD/GR/Nafion/GCE electrode exhibits a linear range from 0.5 to 14 mmol·L−1 with a detection limit of 0.03 mmol·L−1. Moreover, it displays a good reproducibility and long‐term stability.

Construction of reagentless glucose biosensor based on ferrocene conjugated polypyrrole

Glucose oxidase (GOx) was covalently immobilized onto an electrochemically prepared novel copolymer of ferrocene branched polypyrrole for the construction of an amperometric glucose biosensor. Ferrocene-pyrrole monomers were prepared by condensation reaction between ferrocene ethanol and 3-(1H-pyrrol-1-yl)propanoic acid and ferrocene-pyrrole, 3-(1H-pyrrol-1-yl)propanoic acid, and pyrrole monomers were electrochemically polymerized on the surface of the electrode. GOx was covalently immobilized onto the co-polymer coated electrode surface by using coupling agents to create amine bonds. The prepared copolymers were utilized as conducting films for amperometric glucose sensing after immobilization of GOx. Amperometric response was measured as a function of concentration of glucose at a fixed potential of +0.38V vs. Ag/AgCl in a phosphate-buffered saline solution (pH 7.0). Results clearly showed that the ferrocene groups on the co-polymer play the role of electron transfer mediator between the redox center of glucose oxidase (GOx) and the surface of the electrode. Also, the effects of pH and temperature, storage, reusability and interference of the amperometric glucose biosensor were investigated.

Construction of a Novel Glucose Biosensor Based on Covalent Immobilization of Glucose Oxidase on Poly(glycidyl methacrylate‐co‐vinylferrocene)

AbstractA novel glucose biosensor was constructed via direct covalent attachment of glucose oxidase onto epoxy group containing polymeric electron transfer mediator, Poly(glycidyl methacrylate‐co‐vinylferrocene). A copolymer of glycidyl methacrylate (GMA) and vinylferrocene (VFc) with different molar ratios has been prepared by free radical copolymerization. These copolymers have been utilized as polymeric mediators for amperometric glucose sensing. The catalytic electrochemistry of the enzyme electrode with the copolymer was investigated. Copolymer acts as an electron transfer mediator between the redox center of Glucose oxidase (GOx) and the electrode. The stability, reusability, pH and temperature response of the biosensor as well as its kinetic parameter have also been studied.

Immobilization of glucose oxidase on reagentless ferrocene-containing polythiophene derivative and its glucose sensing application

A novel polymer electrode in the form of a thin film was prepared by electrochemical copolymerization of thiophene, thiophene-3-acetic acid, and dicyclopentadienyl iron-1,4-dienylmethyl-2-(thiophen-3-yl)acetate, for fabricating GO x -immobilized electrodes for amperometric sensing of glucose. Glucose oxidase was immobilized by covalent binding to the carboxyl groups on the electrode. The catalytic electrochemistry of the enzyme electrode with the copolymer was investigated. The enzyme electrodes act as a mediator between the redox center of glucose oxidase (GO x ) and the electrode.

Characterization of poly(vinylferrocene- co-2-hydroxyethyl methacrylate) for use as electron mediator in enzymatic glucose sensor

A series of novel copolymers, poly(vinylferrocene-co-2-hydroxyethyl methacrylate) (VFc-HEMA), has been prepared by radical copolymerization and characterized. These copolymers have been utilized as polymeric mediators for amperometric glucose sensors. Glucose oxidase (GOx) and the redox copolymers were mixed with carbon paste, and carbon-paste enzyme electrodes were prepared to amperometrically detect concentrations of glucose. From cyclic voltammetry measurements using the enzyme electrodes in the absence and presence of glucose, these copolymers were proved to function as polymeric mediators between the redox center of GOx and the electrode. The composition of VFc-HEMA incorporated in the enzyme electrodes influenced the current response.

Direct Electrical Communication between the Redox Center of Glucose Oxidase and Electrode via Conductive Polypyrrole Matrix

Abstract A glucose oxidase (GOD) modified polypyrrole electrode was prepared by coelectropolymerization with unmodified pyrrole. Direct electrical communication between the redox center of GOD and the metal electrode via the conductive polypyrrole matrix was demonstrated using the electrode.

Achievement of direct electron transfer between glucose oxidase and an electrode by adsorption of hydroquinonesulfonate on the enzyme

Hydroquinone-adsorbed glucose oxidase shows amperometric sensitivities to glucose without assistance of any electron mediator dissolved in glucose solutions. Electrical interaction of the adsorbed hydroquinonesulfonate with the redox center of glucose oxidase is evidenced by quenching of the fluorescence of glucose oxidase caused by adsorption of hydroquinone sulfonate. The amount of adsorption of one hydroquinonesulfonate for one redox center of glucose oxidase is enough to give the maximum apmerometric sensitivity.

Electron transfer between an electron mediator-adsorbed glucose oxidase and an electrode

Visible absorption and fluorescence spectra of the flavin adenine dinucleotide of glucose oxidase are changed slightly on adsorption of hydroquinonesulfonate, suggesting the occurrence of structural changes in the glucose oxidase. The enzymatic activity of glucose oxidase is also influenced by adsorption of hydroquinonesulfonate. Hydroquinonesulfonate adsorbed on glucose oxidase mediates electron transfer between the redox center of glucose oxidase and an electrode, and the rate of electron transfer is influenced by the amount of mediator adsorbed, Based on information derived from changes in the absorption and fluorescence spectra measured as a function of the amount of hydroquinonesulfonate adsorbed, a mechanism for electron transfer is proposed.