Direct Electrochemistry Of Glucose Oxidase Research Articles

Microelectrode glucose biosensor based on nanoporous platinum/graphene oxide nanostructure for rapid glucose detection of tomato and cucumber fruits

Abstract A microelectrode glucose biosensor based on a three-dimensional hybrid nanoporous platinum/graphene oxide nanostructure was developed for rapid glucose detection of tomato and cucumber fruits. The nanostructure was fabricated by a two-step modification method on a microelectrode for loading a larger amount of glucose oxidase. The nanoporous structure was prepared on the surface of the platinum microelectrode by electrochemical etching, and then graphene oxide was deposited on the prepared nanoporous electrode by electrochemical deposition. The nanoporous platinum/graphene oxide nanostructure had the advantage of improving the effective surface area of the electrode and the loading quantity of glucose oxidase. As a result, the biosensor achieved a wide range of 0.1–20.0 mmol/L in glucose detection, which had the ability to accurately detect the glucose content. It was found that the three-dimensional hybrid nanostructure on the electrode surface realized the rapid direct electrochemistry of glucose oxidase. Therefore, the biosensor achieved high glucose detection sensitivity (11.64 μA·L/(mmol·cm2), low detection limit (13 μmol/L) and rapid response time (reaching 95% steady-state response within 3 s), when calibrating in glucose standard solution. In agricultural application, the as-prepared biosensor was employed to detect the glucose concentration of tomato and cucumber samples. The results showed that the relative deviation of this method was less than 5% when compared with that of high-performance liquid chromatography, implying high accuracy of the presented biosensor in glucose detection in plants.

Rising Mesopores to Realize Direct Electrochemistry of Glucose Oxidase toward Highly Sensitive Detection of Glucose

AbstractDirect electrochemistry, a direct electron transfer process between enzymes and electrode possesses, has important fundamental significance in bioelectrochemistry while offering very efficient electrocatalysis for enzyme‐based sensors. Herein, the pore structure of bacterial cellulose porous carbon nanofibers (BPCNFs) is tailored by controlled thermal carbonization. It is discovered that rising mesopores can realize a fast direct electrochemistry of glucose oxidase (GOx) for highly sensitive detection of glucose, achieving a sensitivity of 123.28 µA mmol L−1 cm−2 and a detection limit of 0.023 µmol L−1. The enhancement mechanism for the mesopores is ascribed to the most adequate mesopores of BPCNF900, which offer size‐matched “nests” to trap GOx for intimate contacts with the conductive carbon nanofiber enabling fast direct electrochemistry. In addition, with the BPCNF900 sensing platform, the mechanisms for GOx‐direct‐electrochemistry‐catalyzed glucose oxidation and oxygen reduction are systematically investigated to further clarify the confusions of glucose sensing in air and N2‐saturated solutions. This work demonstrates fundamental insights for the direct electrochemistry enabled by rationally designing a pore structure matching the target proteins, thus possessing universal significance in protein‐based electrochemical devices while offering a facile route to fabricate a highly sensitive glucose sensor for practical clinic diagnosis.

Direct electrochemistry of glucose oxidase based on one step electrodeposition of reduced graphene oxide incorporating polymerized l-lysine and its application in glucose sensing.

The direct electron transfer and enzyme catalytic activity were investigated in electrochemical biosensor based on glucose oxidase (GOx) and electrochemical reduced graphene oxide-poly-(l-lysine) (ERGO-PLL) hybrid composite film embedded in a biocompatible matrix of Nafion. The ERGO-PLL was fabricated onto glassy carbon electrode (GCE) through one step electrodeposition of RGO incorporating PLL from graphene oxide-l-lysine aqueous dispersion. The fabrication process of Nafion/GOx/ERGO-PLL/GCE has been characterized by cyclic voltammetry and electrochemical impedance spectroscopy, and the surface morphology of modified electrodes were characterized by scanning electron microscopy. A pair of well-defined redox peaks with formal potential and peak separation of -0.461 V and 30 mV were observed at scan rate of 50 mV s-1, the electron transfer rate constant was calculated to be 18.7 s-1, demonstrated that direct electron transfer between immobilized GOx with ERGO-PLL and GCE was achieved. Moreover, the fabricated enzyme biosensor exhibited excellent electrocatalytic activity for determination of glucose in O2-free PBS (7.40) with linear voltammetric response from 0.005 to 9.0 mmol L-1, and detection limits (S/N = 3) of 2.0 μmol L-1. This work indicates that ERGO-PLL based modified electrode is superior to that of graphene based, and could be applied in biosensors, bioelectronics and electrocatalysis, etc.

A TiO2–SnS2 nanocomposite as a novel matrix for the development of an enzymatic electrochemical glucose biosensor

A TiO2–SnS2 nanocomposite was prepared and for the first time used to construct a novel electrochemical enzymatic glucose biosensor based on the direct electrochemistry of glucose oxidase (GOx).

Tannic Acid-Reduced Graphene Oxide Deposited with Pt Nanoparticles for Switchable Bioelectronics and Biosensors Based on Direct Electrochemistry

In this study, we reported a novel biosensor based on direct electrochemistry of glucose oxidase (GOx) on a tannic acid-reduced graphene oxide nanocomposite modified glassy carbon electrode deposited with Pt nanoparticles. Tannic acid (TA) was utilized for the simultaneous green reduction of Pt4+ and graphene oxide (GO), along with modifying the reduced GO for the GOx immobilization, thus constructing a switchable surface with pH and temperature alterations. Upon the electrochemically oxidation of TA to quinone, enhanced electron transfer was obtained, and a third generation biosensor was fabricated using π–π interaction between GO and TA and Schiff-base assisted hydrogen bonds between GOx and TA interactions. The redox peaks were observed at a formal potential of −0.462 V with a peak separation (ΔEp) of 56 mV, which reveals the fast electron transfer. The linear response to glucose oxidation was in the range of 2–10 mM with a limit of detection of 1.21 μM and a sensitivity of 27.51 μA mM–1 cm–2. Upon the...

Highly efficient biosensors by using well-ordered ZnO/ZnS core/shell nanotube arrays

We have studied the fabrication of highly efficient glucose sensors using well-ordered heterogeneous ZnO/ZnS core/shell nanotube arrays (CSNAs). The modified electrodes exhibit a superior electrochemical response towards ferrocyanide/ferricyanide and in glucose sensing. Further, the fabricated glucose biosensor exhibited good performance over an acceptable linear range from 2.39 × 10−5 to 2.66 × 10−4 mM, with a sensitivity of 188.34 mA mM−1 cm−2, which is higher than that of the ZnO nanotube array counterpart. A low limit of detection was realized (24 μM), which is good compared with electrodes based on conventional structures. In addition, the enhanced direct electrochemistry of glucose oxidase indicates the fast electron transfer of ZnO/ZnS CSNA electrodes, with a heterogeneous electron transfer rate constant (Ks) of 1.69 s−1. The fast electron transfer is attributed to the high conductivity of the modified electrodes. The presented ZnS shell can facilitate the construction of future sensors and enhance the ZnO surface in a biological environment.

Direct electrochemistry of glucose oxidase immobilized on Au nanoparticles-functionalized 3D hierarchically ZnO nanostructures and its application to bioelectrochemical glucose sensor

Three-dimensional (3D) hierarchically ZnO nanoarchitecture with controlled morphology and dimensions was synthesized by trisodium citrate-assisted solution phase method and functionalized by Au nanoparticles (AuNPs) via in situ reduction of HAuCl4. The as-prepared AuNPs-functionalized 3D hierarchically ZnO nanostructure (Au–ZnO nanocomposite) were used as a novel immobilization matrix for glucose oxidase (GOD) and exhibited excellent direct electron transfer properties for GOD. The AuNPs-functionalized 3D hierarchically ZnO nanostructure (Au–ZnO nanocomposite) favored the immobilization of the glucose oxidase (GOD) and the penetration of water-soluble glucose molecules, which helped efficiently catalyze the oxidation of glucose and facile direct electron transfer for GOD. The as-fabricated glucose biosensor exhibited satisfactory analytical performance with a low detection limit (0.02mM) and an acceptable linear range from 1 to 20mM. These results indicated that AuNPs-functionalized 3D hierarchically ZnO nanomaterial is a promising candidate material for high-performance glucose biosensors.

Preparation of polyaniline–TiO2 nanotube composite for the development of electrochemical biosensors

The significant and novel aspect of this work lies in the preparation of a polyaniline (PANI)–TiO2 nanotube (TNT) composite which can provide excellent biocompatibility, good electrical conductivity, low electrochemical interferences and high signal-to-noise ratio for the development of electrochemical biosensors. Using a hydrothermal method, TiO2 nanoparticles were initially transformed into TNTs, on which aniline was then polymerized by oxidative polymerization to form an intimate and uniform PANI–TNT composite. After being characterized by different spectroscopic techniques, the PANI–TNT composite was used to immobilize glucose oxidase (GOD) for the construction of an electrochemical biosensor. The direct electrochemistry and electro-catalytic performance of the biosensors based on PANI–TNTs and TNTs was studied by cyclic voltammetry. The direct electrochemistry of GOD on PANI–TNTs modified electrodes was achieved and the heterogeneous electron transfer rate constant (ks) for GOD was estimated to be 9.3s−1. Furthermore, the redox currents of GOD at PANI–TNT modified biosensor were improved by ∼55% compared to that at TNT modified biosensor. The PANI–TNT modified GOD biosensor exhibited good sensitivity (11.4μAmM−1), wide dynamic range (10–2500μM) and low limit of detection (0.5μM), which are attributed to the improved properties of the composite.

Direct Electrochemistry of Glucose Oxidase at Reduced Graphene Oxide and β‐Cyclodextrin Composite Modified Electrode and Application for Glucose Biosensing

AbstractA simple glucose biosensor has been developed based on direct electrochemistry of glucose oxidase (GOx) immobilized on the reduced graphene oxide (RGO) and β‐cyclodextrin (CD) composite. A well‐defined redox couple of GOx appears with a formal potential of ∼−0.459 V at RGO/CD composite. A heterogeneous electron transfer rate constant (Ks) has been calculated for GOx at RGO/CD as 3.8 s−1. The fabricated biosensor displays a wide response to glucose in the linear concentrations range from 50 µM to 3.0 mM. The sensitivity and limit of detection of the biosensor is estimated as 59.74 µA mM−1 cm−2 and 12 µM, respectively.

Conformation, Bioactivity and Electrochemical Performance of Glucose Oxidase Immobilized on Surface of Gold Nanoparticles

Since nanomaterials have been extensively used to immobilize enzymes/proteins for developing electrochemical biosensors, it is very important to know the effects of both the conformation and bioactivity of these immobilized enzymes/proteins and the surface condition of the nanomaterials on the electroanalytical performances of enzymes/proteins based biosensors. In this work, a series of gold nanoparticles (AuNPs)-glucose oxidase (GOD) nanocomposites, such as AuNPs-GOD, AuNPs-mercaptohexadecyl acid (MHA)-GOD and AuNPs -mercaptoundecanoic acid (MUA)-GOD, have been prepared to investigate the relationship among the conformation and bioactivity of GOD immobilized on AuNPs, the surface condition of AuNPs and the electroanalytical performance of biosensors. It was found that the conformation and bioactivity of GOD immobilized on AuNPs surface depended on the surface condition of AuNPs and were more or less changed. The direct electrochemistry of GOD became better with the increase of deformation. When AuNPs-GOD nanocomposites were employed to develop glucose biosensor based on the reduction of O2, the MHA and MUA layer around AuNPs seriously disrupted the performance of biosensors. The work might provide a potential guidance for developing biosensor based on nanomaterials and enzymes/proteins.

Direct electrochemistry of glucose oxidase immobilized on carbon nanotube for improving glucose sensing

In this research, we suggest an enzyme immobilization structure that glucose oxidase (GOx) is coated on carbon nanotube (CNT) and quantify an optimal condition for the immobilization. Physical adsorption of GOx to CNT is used as the method for GOx immobilization on CNT (GOx/CNT). Cyclic voltammetry (CV) is served to evaluate catalytic activity and direct electrochemistry, while SEM is used to confirm the formation of GOx/CNT. To investigate the catalytic activity and the optimal loading of GOx, its peak current and electron transfer rate constant, ks, are measured. In both ways, 2 mg mL−1 GOx shows best results and its ks is 1.14s−1. From the relationship between scan rate and peak current, it is also revealed that this structure is (i) controlled by surface reaction and (ii) quasi-reversible. Regarding redox reaction of GOx, peak potential is linearly varied with pH with slope of −51 mV/pH. The slope indicates a typical two-electron reaction that is a desirable reaction pathway. GOx-catalyzed glucose oxidation reaction (GOR) is also investigated by reacting different concentrations of glucose with GOx/CNT layer. Peak current for GOR linearly increases with glucose concentration, proving that increase in glucose concentration promotes GOR. Therefore, GOx/CNT leads to high sensitivity of glucose (53.5 μAmM−1cm−2). When it comes to long term stability, activity of GOx/CNT is measured and 86% of the activity is maintained even after two weeks, indicating that long term stability of GOx is excellent.

Direct electrochemistry of glucose oxidase and sensing of glucose at a glassy carbon electrode modified with a reduced graphene oxide/fullerene-C60 composite

Schematic representation for the sensing of glucose at the RGO–C60/GOx composite.

Direct electrochemistry of GOD on nitrogen-doped porous carbon and its biosensing

Nitrogen-doped porous carbon (N-DPC) was prepared via a simple and effective method and was characterized by X-ray photoelectron spectroscopy, energy dispersive X-ray spectroscopy, N2 adsorption–desorption isotherms and scanning electron microscopy. The results showed that the N-DPC with two type reticular porosities in an average diameter of 10–100 nm has a large specific surface area, which is favorable to immobilize the redox proteins for constructing biosensors. Direct electrochemistry of glucose oxidase (GOD) on the N-DPC-modified electrode was investigated. UV–vis spectroscopy showed that GOD retained its catalytic activity in the N-DPC film. Electrochemical results indicated that the modified electrode exhibited effective direct electron transfer. It demonstrated that such N-DPC could provide a good matrix for direct electrochemistry of enzymes. A novel biosensor was developed by entrapping GOD in the N-DPC-modified electrode for glucose detection and showed a stable, rapid, and reproducible electrocatalytic response, a high sensitivity, a wide linear range and a low detection limit. Moreover, the biosensor can be applied in practical analysis and exhibit good reproducibility and long-term stability.

Achieving direct electrochemistry of glucose oxidase by one step electrochemical reduction of graphene oxide and its use in glucose sensing

In this paper, the direct electrochemistry of glucose oxidase (GOD) was accomplished at a glassy carbon electrode modified with electrochemically reduced graphene oxide/sodium dodecyl sulfate (GCE/ERGO/SDS). A pair of reversible peaks is exhibited on GCE/ERGO/SDS/GOD by cyclic voltammetry. The peak-to-peak potential separation of immobilized GOD is 28mV in 0.1M phosphate buffer solution (pH7.0) with a scan rate of 50mV/s. The average surface coverage is 2.62×10−10molcm−2. The resulting biosensor exhibited a good response to glucose with linear range from 1 to 8mM (R2=0.9878), good reproducibility and detection limit of 40.8μM. The results from the biosensor were similar (±5%) to those obtained from the clinical analyzer.

An enhanced direct electrochemistry of glucose oxidase at poly(taurine) modified glassy carbon electrode for glucose biosensor

A novel method for detecting glucose that employs glucose oxidase (GOx) at polytaurine (p-taurine)-modified glassy carbon electrode is reported. The polymerization of taurine was assessed by a simple electrochemical approach. The electro-polymerized p-taurine was confirmed by X-ray photoelectron spectroscopy (XPS) and scanning electron microscopy (SEM). Notably, we obtained a good peak-to-peak separation (ΔEp) of 46 mV for p-taurine/GOx/Nf-modified GCE, indicating an excellent electron transfer process between GOx and the p-taurine-modified electrode. The fabricated composite p-taurine/GOx/Nf provides excellent electrocatalytic activity towards glucose detection. In this investigation, the glucose sensor has been achieved by reductive detection of oxygen consumption without a mediator. The detection of glucose was monitored using cyclic voltammetry (CV) and differential pulse voltammetry (DPV). The obtained limit of detection (LOD) and sensitivity of the proposed glucose sensor were 0.06 mM and 26.58 μA−1 mM cm−2, respectively Moreover, the facile biosensor based on the Tau/GOx/Nf composite is preferred due to its simplicity, long-term stability, ultra high sensitivity, reliability, and durability, rendering practical applications even for real sample systems.

Green synthesis of reduced graphene oxide decorated with gold nanoparticles and its glucose sensing application

Here, we report an eco-friendly method for synthesis of reduced graphene oxide decorated with gold nanoparticles (rGO-Aunano) by using rose water as reducing agent. The prepared materials were characterized using UV–visible absorption spectroscopy, Raman spectroscopy, atomic force microscopy (AFM), scanning electron microscopy (SEM) and X-ray diffraction (XRD). Furthermore, the direct electrochemistry of glucose oxidase (GOD) was achieved at a glassy carbon electrode modified with rGO-Aunano. The resulting biosensor exhibited good response to glucose with linear range from 1 to 8mM with a low detection limit of 10μM.

Direct electrochemistry of glucose oxidase and sensing glucose using a screen-printed carbon electrode modified with graphite nanosheets and zinc oxide nanoparticles

We have studied the direct electrochemistry of glucose oxidase (GOx) immobilized on electrochemically fabricated graphite nanosheets (GNs) and zinc oxide nanoparticles (ZnO) that were deposited on a screen printed carbon electrode (SPCE). The GNs/ZnO composite was characterized by using scanning electron microscopy and elemental analysis. The GOx immobilized on the modified electrode shows a well-defined redox couple at a formal potential of −0.4 V. The enhanced direct electrochemistry of GOx (compared to electrodes without ZnO or without GNs) indicates a fast electron transfer at this kind of electrode, with a heterogeneous electron transfer rate constant (Ks) of 3.75 s−1. The fast electron transfer is attributed to the high conductivity and large edge plane defects of GNs and good conductivity of ZnO-NPs. The modified electrode displays a linear response to glucose in concentrations from 0.3 to 4.5 mM, and the sensitivity is 30.07 μA mM−1 cm−2. The sensor exhibits a high selectivity, good repeatability and reproducibility, and long term stability.

Direct electrochemistry of glucose oxidase and glucose biosensing on a hydroxyl fullerenes modified glassy carbon electrode

Direct electrochemistry of glucose oxidase (GOD) was achieved when GOD-hydroxyl fullerenes (HFs) nano-complex was immobilized on a glassy carbon (GC) electrode and protected with a chitosan (Chit) membrane. The ultraviolet–visible absorption spectrometry (UV–vis), transmission electron microscopy (TEM), and circular dichroism spectropolarimeter (CD) methods were utilized for additional characterization of the GOD, GOD-HFs and Chit/GOD-HFs. Chit/HFs may preserve the secondary structure and catalytic properties of GOD. The cyclic voltammograms (CVs) of the modified GC electrode showed a pair of well-defined quasi-reversible redox peaks with the formal potential (E°′) of 353±2mV versus Ag/AgCl at a scan rate of 0.05V/s. The heterogeneous electron transfer constant (ks) was calculated to be 2.7 ± 0.2s-1. The modified electrode response to glucose was linear in the concentrations ranging from 0.05 to 1.0mM, with a detection limit of 5±1μM. The apparent Michaelis–Menten constant (Kmapp) was 694±8μM. Thus, the modified electrode could be applied as a third generation biosensor for glucose with high sensitivity, selectivity and low detection limit.

Direct electrochemistry of glucose oxidase and a biosensor for glucose based on a glass carbon electrode modified with MoS2 nanosheets decorated with gold nanoparticles

An electrochemical glucose biosensor was developed by immobilizing glucose oxidase (GOx) on a glass carbon electrode that was modified with molybdenum disulfide (MoS2) nanosheets that were decorated with gold nanoparticles (AuNPs). The electrochemical performance of the modified electrode was investigated by cyclic voltammetry, and it is found that use of the AuNPs-decorated MoS2 nanocomposite accelerates the electron transfer from electrode to the immobilized enzyme. This enables the direct electrochemistry of GOx without any electron mediator. The synergistic effect the MoS2 nanosheets and the AuNPs result in excellent electrocatalytic activity. Glucose can be detected in the concentration range from 10 to 300 μM, and down to levels as low as 2.8 μM. The biosensor also displays good reproducibility and long-term stability, suggesting that it represents a promising tool for biological assays.

Direct electrochemistry of glucose oxidase immobilized on ZrO2nanoparticles-decorated reduced graphene oxide sheets for a glucose biosensor

Schematic representation of the preparation procedure of GOx–PLL/RGO–ZrO2composite.