Direct Electrochemistry Of Glucose Oxidase Research Articles

Application of magnetic core–shell microspheres on reagentless immunosensor based on direct electrochemistry of glucose oxidase for detection of carbohydrate antigen 19-9

This paper reported the production of magnetic core–shell composite microspheres (Fe3O4@SiO2–[email protected]2) which consist of a silica-protected magnetite particle core, an active gold nanoparticle transition layer and an outer mesoporous silica shell with pore channels. During the synthesis of the microspheres, the shape of the nanocomposite was changed from hexagons or quadrangles of Fe3O4 to well-defined spheres of Fe3O4@SiO2–[email protected]2. The synthesized microspheres were characterized by scanning electron microscopy, transmission electron microscopy and X-ray photoelectron spectroscopy. A strategy was proposed for the fabrication of reagentless immunosensors based on direct electrochemistry of glucose oxidase (GOD), which employed multiwall carbon nanotubes and the prepared Fe3O4@SiO2–[email protected]2 as immobilization matrix. The immobilized GOD exhibited direct electrochemistry with a rate constant of 1.8 s−1. The cyclic voltammetric (CV) and differential pulse voltammetric (DPV) peak currents of GOD decreased linearly with the increase of carbohydrate antigen 19-9 (CA19-9) concentrations from 0.01 to 1.11 U mL−1 and 11.11 to 476.11 U mL−1 with a relatively low detection limit of 0.004 U mL−1. Furthermore, this strategy avoided the addition of electron transfer mediator, which simplified the immunoassay procedure and decreased the analytical time.

Direct electrochemistry of glucose oxidase at electrochemically reduced graphene oxide-multiwalled carbon nanotubes hybrid material modified electrode for glucose biosensor

Direct electrochemistry of glucose oxidase (GOx) at an electrochemically reduced graphene oxide–multiwalled carbon nanotubes hybrid (ERGO–MWCNT) modified glassy carbon electrode (GCE) has been reported. The π–π stacking interaction operating between the MWCNT and graphene oxide (GO) has been revealed by UV–Vis absorption spectroscopy. GOx was well immobilized onto the ERGO–MWCNT hybrid film, as a result direct electrochemistry of GOx has been achieved. Compared with pristine MWCNT, 2.1 fold higher peak current and very low peak to peak separation (ΔEp) of 26mV were observed at the hybrid film, demonstrating faster electron transfer between GOx and the modified electrode surface. Moreover, the modified film exhibited high electrocatalytic activity towards glucose via reductive detection of oxygen consumption and in the presence of mediator. The proposed biosensor exhibits low detection limit of 4.7μM with wide linear range of 0.01–6.5mM and acquires excellent storage and operational stabilities. The accurate glucose determination in human blood serum and good recoveries achieved in spiked urine samples revealed their great potential in the practical applications.

Engineering graphene/carbon nanotube hybrid for direct electron transfer of glucose oxidase and glucose biosensor

The graphene/carbon nanotube hybrid was designed and implemented by a deoxygenation process for direct electron transfer of glucose oxidase and glucose biosensor. The procedure was analyzed by transmission electron microscopy, X-ray photoelectron spectroscopy, and Raman spectra, etc. The strategy of structurally engineering one-dimensional carbon nanotube (CNT) and two-dimensional graphene oxide (GO) presented three benefits: (a) a deoxygenation process between GO and acid-CNT was introduced under strongly alkaline condition; (b) GO prevented the irreversible integration of CNT; and (c) CNT hindered the restacking of GO. The RGO interacted with CNT through the van der Waals forces and π–π stacking interaction. The three-dimensional hybrid not only had a high surface area, but also exhibited a good electronic conductivity. A direct electrochemistry of glucose oxidase was obtained on the nanohybrid modified electrode which showed good response for glucose sensing. This study would provide a facile and green method for the preparation of nanohybrid for a wide range of applications including biosensing, super capacitor, and transparent electrode.

Glassy carbon electrode modified with glucose oxidase–graphene–nano-copper composite film for glucose sensing

We report on the modification of a glassy carbon electrode with graphene and Cu nanoparticles (Cunano), and how this electrode can serve as a platform for the construction of a novel electrochemical biosensor for the study of the direct electrochemistry of glucose oxidase and then application for glucose detection. To obtain the biosensor, the glucose oxidase was immobilized on the surface of the graphene and Cunano modified electrode, and this process was characterized by cyclic voltammetry and electrochemical impedance spectroscopy. A sensitive biosensor with a detection limit of 5μM glucose was achieved, which was thought to result from a combination of beneficial effects including the biocompatibility and large surface area of the Cunano, the high conductivity of the graphene, the synergistic effects of composite film, and the increased quantity of glucose oxidase adsorbed on the electrode surface. The voltammetric responses were proportional to the concentration of glucose in the range from 0.05mM to 12mM. The biosensor was sensitive and stable.

Direct electrochemistry of glucose oxidase immobilized on TiO2–graphene/nickel oxide nanocomposite film and its application

A novel electrochemical platform based on nickel oxide (NiO) nanoparticles and TiO2–graphene (TiO2–Gr) was developed for the direct electrochemistry of glucose oxidase (GOD). The electrochemical behavior of the sensor was studied using cyclic voltammetry and chronoamperometry. The experimental results demonstrated that the nanocomposite well retained the activity of GOD and the modified electrode GOD/NiO/TiO2–Gr/GCE exhibited excellent electrocatalytic activity toward the redox of GOD as evidenced by the significant enhancement of redox peak currents in comparison with bare GCE. The biosensor responded linearly to glucose in the range of 1.0–12.0 mM, with a sensitivity of 4.129 μA mM−1 and a detection limit of 1.2 × 10−6 M under optimized conditions. The response time of the biosensor was 3 s. In addition, the developed biosensor possessed good reproducibility and stability, and there was negligible interference from other electroactive components.

A simple electrochemical approach to fabricate a glucose biosensor based on graphene–glucose oxidase biocomposite

We report a simple electrochemical approach for the immobilization of glucose oxidase (GOx) on reduced graphene oxide (RGO). The immobilization of GOx was achieved in a single step without any cross linking agents or modifiers. A simple solution phase approach was used to prepare exfoliated graphene oxide (GO), followed by electrochemical reduction to get RGO–GOx biocomposite. The direct electrochemistry of GOx was revealed at the RGO–GOx modified glassy carbon electrode (GCE). The electrocatalytic and electroanalytical applications of the proposed film were studied by cyclic voltammetry (CV) and amperometry. It is notable that the glucose determination has been achieved in mediator-free conditions. RGO–GOx film showed very good stability, reproducibility and high selectivity. The developed biosensor exhibits excellent catalytic activity towards glucose over a wide linear range of 0.1–27mM with a sensitivity of 1.85μAmM−1cm−2. The facile and easy electrochemical approach used for the preparation of RGO–GOx may open up new horizons in the production of cost-effective biosensors and biofuel cells.

A glucose biosensor based on direct electrochemistry of glucose oxidase immobilized onto platinum nanoparticles modified graphene electrode

The platinum nanoparticles were adsorbed on graphene oxide sheets and played an important role in catalytic reduction of graphene oxide with hydrazine, leading to the formation of graphene-Pt nanoparticles. Because of their good electronic properties, biocompatibility and high surface area, graphene-Pt based composites achieved the direct electron transfer of redox enzyme and maintained their bioactivity well. The graphene-Pt nanocomposites were characterized using X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), high-resolution transmission electron microscopy (HR-TEM) and selected area electron diffraction (SAED). The amperometric biosensor fabricated by depositing glucose oxidase over Nafion-solubilized graphene-Pt electrode retained its biocatalytic activity and has offered fast and sensitive glucose quantification.

Comparison of the direct electrochemistry of glucose oxidase immobilized on the surface of Au, CdS and ZnS nanostructures

A comparison of the electrochemical and photoelectrochemical behaviors of three biosensors, based on the use of Au, CdS, and ZnS nanoparticles–glucose oxidase (GOD) system, is discussed. All the nanoparticles were electrodeposited onto the indium tin oxide (ITO) thin film coated glass surface. GOD was then immobilized on the nanoparticles-modified electrodes surface with the sol–gel technique. The deposited nanoparticles on ITO electrodes were characterized by scanning electron microscopy, UV–vis spectroscopy and electrochemical impedance spectra. The direct electrochemistry of GOD, analytical performance of glucose calibration curves and the kinetic parameters of the enzyme reaction were compared for all the electrochemical biosensors. Furthermore, the current response of the quantum dots–GOD system biosensor can be increased after illumination. The electrochemical and photoelectrochemical biosensors based on ZnS nanostructures exhibited higher sensitivity than that of Au or CdS nanostructures. Considering ZnS is nontoxic to human and environment, the results suggest that ZnS nanoparticles–GOD system seems to be a promising platform for fabrication of novel electrochemical and photoelectrochemical biosensors.

Direct Electrochemistry of Glucose Oxidase at a Gold Electrode Modified with Graphene Nanosheets

In this work, we report the direct electrochemistry of glucose oxidase (GOD) observed at a gold electrode modified with graphene nanosheets. Initially, graphene nanosheets were synthesized and conjugated to the enzyme GOD and immobilized on to a gold electrode surface. Cyclic voltammetry was then performed using Gold-Graphene-GOD modified electrodes in a pH 7.2 phosphate buffered saline (PBS). A pair of well-defined redox peaks was obtained for GOD with the reduction peak centered at +180 mV and a peak separation of 70 mV in PBS under physiological conditions. Moreover, the electron transfer rate of GOD redox reaction was greatly enhanced and the peak potential was found to be pH dependent at the graphene-GOD surface. Further, the performance of the Gold-Graphene-GOD was found to be stable and excellent under physiological conditions indicating the possibility of employing this platform for real time analysis. The observed results indicated that the 2D-graphene holds great promise for conjugation ability with a variety of enzymes. Further, our results also confirmed that graphene is capable of holding the enzyme GOD in a favorable position and retains its original structure and functionality that are essential for biosensing.

Direct Electrochemistry of Glucose Oxidase Immobilized on Titanium Carbide‐Au Nanoparticles‐Fullerene C60 Composite Film and Its Biosensing for Glucose

AbstractThe direct electrochemistry of glucose oxidase (GOD) immobilized on the designed titanium carbide‐Au nanoparticles‐fullerene C60 composite film modified glassy carbon electrode (TiC‐AuNPs‐C60/GCE) and its biosensing for glucose were investigated. UV‐visible and Fourier‐transform infrared spectra of the resulting GOD/TiC‐AuNPs‐C60 composite film suggested that the immobilized GOD retained its original structure. The direct electron transfer behaviors of immobilized GOD at the GOD/TiC‐AuNPs‐C60/GCE were investigated by cyclic voltammetry in which a pair of well‐defined, quasi‐reversible redox peaks with the formal potential (E0′) of ‐0.484 V (vs. SCE) in phosphate buffer solution (0.05 M, pH 7.0) at the scan rate of 100 mV·s−1 were obtained. The proposed GOD modified electrode exhibited an excellent electrocatalytic activity to the reduction of glucose, and the currents of glucose reduction peak were linearly related to glucose concentration in a wider linearity range from 5.0 × 10−6 to 1.6 × 10−4 M with a correlation coefficient of 0.9965 and a detection limit of 2.0 × 10−6 M (S/N = 3). The sensitivity and the apparent Michaelis‐Menten constant (KMapp) were determined to be 149.3 μA·mM−1·cm−2 and 6.2 × 10−5 M, respectively. Thus, the protocol will have potential application in studying the electron transfer of enzyme and the design of novel electrochemical biosensors.

Reduced graphene oxide/PAMAM–silver nanoparticles nanocomposite modified electrode for direct electrochemistry of glucose oxidase and glucose sensing

Reduced graphene oxide/PAMAM–silver nanoparticles nanocomposite (RGO–PAMAM–Ag) was synthesized by self-assembly of carboxyl-terminated PAMAM dendrimer (PAMAM-G3.5) on graphene oxide (GO) as growing template, and in-situ reduction of both AgNO3 and GO under microwave irradiation. The RGO–PAMAM–Ag nanocomposite was used as a novel immobilization matrix for glucose oxidase (GOD) and exhibited excellent direct electron transfer properties for GOD with the rate constant (Ks) of 8.59s−1. The fabricated glucose biosensor based on GOD electrode modified with RGO–PAMAM–Ag nanocomposite displayed satisfactory analytical performance including high sensitivity (75.72μAmM−1cm−2), low detection limit (4.5μM), an acceptable linear range from 0.032mM to 1.89mM, and also preventing the interference of some interfering species usually coexisting with glucose in human blood at the work potential of −0.25V. These results indicated that RGO–PAMAM–Ag nanocomposite is a promising candidate material for high-performance glucose biosensors.

Novel urchin-like In2O3–chitosan modified electrode for direct electrochemistry of glucose oxidase and biosensing

A novel urchin-like In2O3–chitosan modified glassy carbon electrode (GCE) is for the first time prepared. The direct electrochemistry of glucose oxidase (GOD) immobilized on the surface of modified GCE and biosensing are studied. The urchin-like In2O3 nanostructure-based matrix has large specific surface area and provides a favorable and biocompatible microenvironment for promoting the direct electron transfer between proteins and electrode surface. The properties of different modified electrode are characterized by scanning electron microscopy (SEM), electrochemical impedance spectra (EIS), UV–vis spectroscopy, Fourier transform infrared spectroscopy (FTIR) and cyclic voltammetry, respectively. The constructed glucose biosensor shows wide linear range (5.0 × 10−6 to 1.3 × 10−3 M), low detection limit (1.9 × 10−6 M), a Michaelis–Menten constant of 0.37 mM. The proposed biosensor has good sensitivity, excellent selectivity, good reproducibility and stability. This urchin-like In2O3–chitosan matrix provides a new approach and efficient matrix for the direct electrochemistry of proteins and developing novel types of biosensors.

Enhanced Direct Electrochemistry of Glucose Oxidase and Glucose Biosensing Based on TiO<sub>2</sub>-Decorated Graphene Nanohybrids

Using TiO2-decorated graphene (TiO2-G) nanohybrids as the immobilized platform for redox protein, and selecting glucose oxidase (GOD) as model enzyme, the direct electrochemistry of GOD was investigated in this paper. By virtue of the synergetic effect between graphene and TiO2 nanoparticles, the direct electron transfer of GOD on the TiO2-G nanohybrids modified electrode was remarkably promoted with a rate constant of 3.24 s-1. Moreover, based on the decrease of the electrocatalytic response of the reduced form of GOD by dissolved oxygen, a glucose biosensor was developed, which showed a satisfactory analytical performance for glucose determination over an acceptable linear concentration range from 5×10−4 to 2×10−2 mol/L. All these results demonstrated the great significance of such TiO2-G nanohybrids for the immobilization of enzyme and other biomolecules.

Direct Electrochemistry of Glucose Oxidase at Reduced Graphene Oxide/Zinc Oxide Composite Modified Electrode for Glucose Sensor

Direct Electrochemistry of Glucose Oxidase at Reduced Graphene Oxide/Zinc Oxide Composite Modified Electrode for Glucose Sensor

An reagentless glucose biosensor based on direct electrochemistry of glucose oxidase immobilized on poly(methylene blue) doped silica nanocomposites

Conducting polymer nanocomposites have attracted a wide attention in material chemistry and analytical chemistry. In this work, poly(methylene blue) doped silica nanocomposites (PMB@SiO2(nano)) on glassy carbon electrode (GCE) were synthesized based on a two-step electropolymerization. Compared with poly(methylene blue) film, PMB@SiO2(nano) had more advantages in facilitating electron transfer between glucose oxidase (GOx) and the electrode surface. GOx immobilized on PMB@SiO2(nano) underwent a direct and reversible electrochemical reaction involving two-electron and two-proton exchange. A reagentless glucose biosensor using the nanocomposite modified electrode was developed. The calibration curve was linear over a glucose concentration range of 0.01–1.11mM with a correlation coefficient of 0.998 and a detection limit (3σ) of 3μM. The apparent Michalis–Menten constant, Km, for the enzymatic reaction was 0.50mM. The developed biosensor presented good accuracy, repeatability, reproducibility and stability as well as an excellent ability to resist interference from ascorbic acid and uric acid species. The investigation indicates that PMB@SiO2(nano) has a good potential for application in construction of the third-generation enzyme biosensor as a conducting matrix material.

Direct electrochemistry of glucose oxidase immobilized on nanostructured gold thin films and its application to bioelectrochemical glucose sensor

Glucose oxidase (GOx) was stably immobilized via a simple physical adsorption method onto the nanostructured Au thin films fabricated by using electrodeposition and galvanic replacement technology, which provides a facile method to prepare morphology-controllable Au films and also facilitates the preparation and application of enzyme modified electrodes. An obvious advantage of the as-prepared enzyme electrode (denoted as GOx/Au/GCE) is that the nano-Au films provide a favorable microenvironment for GOx and facilitate the electron transfer between the active center of GOx and electrodes. Cyclic voltammetry (CV) results indicate that the immobilized GOx displayed a direct, reversible and surface-confined redox reaction in the phosphate buffer solution. Furthermore, the enzyme modified electrode was used as a glucose bioelectrochemical sensor, exhibiting a linear relationship in the concentration ranges of 2.5–32.5μmolL−1 and 60–130μmolL−1 with a detection limit of 0.32μmolL−1 (S/N=3) at an applied potential of −0.55V. Due to the excellent stability, sensitivity and anti-interference ability, the Au thin films are hopeful in the construction of glucose biosensors.

Direct Electrochemistry of Glucose Oxidase Immobilized at a Novel Composite Material β‐Cyclodextrin/poly(4‐aminothiophenol)/Au Nanoparticle Modified Electrode

AbstractA novel complex material was fabricated by three steps. In the first step, gold nanoparticle (Aunano) was prepared with the method of chemistry and dialysis. In the second step, 4‐aminothiophenol (AT) was encapsulated in the cavity of β‐cyclodextrin and formed inclusion complex, cyclodextrin/4‐aminothiophenol (CD/AT). And then inclusion complex was adsorbed to the surface of Aunano based on the bond of Au‐S interaction. In the last step, a complex material, cyclodextrin/poly(4‐aminothiophenol)‐Au nanoparticles (CD/PAT‐Aunano) was obtained by the polymerizing in the acid solution initiated by chlorauric acid. The CD/PAT‐Aunano has spherical nanostructure with the average diameter of 55 nm. Glucose oxidase (GOx) was anchored with this complex material and direct electrochemistry of GOx was achieved. A couple of stable and well‐defined redox peaks were observed with the formal potential (E0′) of ‐0.488 V (vs. SCE) in a pH 6.98 buffer solution. The GOx modified electrode also exhibited an excellent electrocatalytic activity to the reduction of glucose, a linearity range for determination of glucose is from 0.25 mM to 16.0 mM with a detection limit of 0.09 mM (S/N = 3). This protocol had potential application to fabricate the third‐generation biosensor.

Apple – biomorphic synthesis of porous ZnO nanostructures for glucose direct electrochemical biosensor

Biomorphic porous ZnO nanostructures were successfully synthesized via an aqueous sol–gel soaking process using pieces of apple flesh and skin as templates and employed for glucose direct electrochemical biosensor. The structure and morphology of ZnO nanostructures were characterized by X-ray diffraction (XRD) and scanning electron microscope (SEM). By modifying glassy carbon electrode with the biomorphic ZnO nanostructures and Nafion, two glucose biosensors were constructed and their direct electrochemistry of glucose oxidase (GOD) was successfully investigated by cyclic voltammetry (CV). The biomorphic porous ZnO nanostructures using apple skin template (S-ZnO) were more effective in facilitating the electron transfer of immobilized GOD than that of using flesh apple template (F-ZnO). This may be a result of the unique morphology and smaller average crystallite size of the S-ZnO nanostructure. GOD immobilized on Nafion-porous S-ZnO nanostructure composite display direct, reversible, and surface-controlled redox reaction with a detection limit of 10μM, a response time of 7s, high sensitivity of 23.4μA/mMcm2 and a fast heterogeneous electron transfer rate with a rate constant (ks) of 3.9s−1. It was found that S-ZnO significantly has improved the direct electron transfer between GOD and glassy carbon electrode with good stability and reproducibility.

Direct electrochemistry of glucose oxidase and biosensing for glucose based on helical carbon nanotubes modified magnetic electrodes

Poly(diallyldimethylammonium chloride) functionalized helical carbon nanotubes (PDDA-HCNTs) were successfully synthesized. The resulting PDDA-HCNTs composite has good conductivity, solubility and ferromagnetic property. The fabricated HCNTs could be conveniently separated and magnetically attached to the magnetic electrode owing to their excellent magnetic properties. An amperometric biosensor was firstly developed based on glucose oxidase (GOD) functionalized PDDA-HCNTs loaded on magnetic glass carbon electrode. The constructed biosensor exhibited excellent electrocatalytic activity and stability for the detection of glucose with a linear range from 5 to 85 μM and a low detection limit of 0.72 μM at 3 σ. The present work offers a new avenue to broaden the applications of HCNTs in electrochemical biosensors.

Multifunctional carbon nanotubes for direct electrochemistry of glucose oxidase and glucose bioassay

Polydopamine (Pdop) has recently been shown to adsorb to a wide variety of surfaces and serves as an adhesion layer to immobilize biological molecules. In this work, the multifunctional carbon nanotube (CNT) composites were prepared though the oxidation of dopamine at room temperature and subsequent electroless silver deposition by mildly stirring. The stable immobilization and direct electron transfer of glucose oxidase were achieved on the composite film modified glassy carbon electrode. The resulting electrode gave a well-defined redox peaks with a formal potential of about −482 mV (vs. SCE) in pH 7.0 buffer. The electron transfer rate constant was estimated to be 3.6 s −1, due to the combined contribution of Pdop, CNTs and Ag nanoparticles with the help of Nafion. Furthermore, the method for detecting of glucose was proposed based on the decrease of oxygen caused by the enzyme-catalyzed reaction between glucose oxidase (GOD) and glucose. The linear response to glucose ranging from 50.0 μM to 1.1 mM ( R 2 = 0.9958), with a calculated detection limit of 17.0 μM at a signal-to-noise ratio of 3. The low calculated apparent Michaelis–Menten constant ( K M app ) was 5.46 mM, implying the high enzymatic activity and affinity of immobilized GOD for glucose. It can reasonably be expected that this observation might hold true for other noble metal nanostructure-electroactive protein systems, providing a promising platform for the development of biosensors and biofuel cells.