Direct Electron Transfer Of Glucose Oxidase Research Articles

Gold Nanoparticle (Au NP)-Decorated Ionic Liquid (IL) Based Liposome: A Stable, Biocompatible, and Conductive Biomimetic Platform for the Fabrication of an Enzymatic Electrochemical Glucose Biosensor

A novel liposomal nanocomposite with biocompatibility and conductivity, Au@ILs-polysome, was fabricated and first utilized as the electrode material to immobilize the redox enzyme glucose oxidase (GOD) for the sensitive determination of glucose. Ionic liquids (ILs)-based polysome (ILs-polysome) was prepared via the radical polymerization of ILs based liposome (ILs-liposome) and improved by ion exchange with chloroauric acid to prepare Au nanoparticles (Au NPs) modified ILs based polysome (Au@ILs-polysome). The morphology, surface properties, and structure of Au@ILs-polysome were characterized; the results suggest that the nanocomposite exhibited excellent stability on the surface of solid electrodes without fusion. Electrochemical impedance spectroscopy (EIS) demonstrated that the nanocomposite had enhanced conductivity. Cyclic voltammetry (CV) shows that the direct electron transfer of GOD was achieved on the GOD/Au@ILs-polysome/GCE electrode since the Au@ILs-polysome provided a biocompatible microenvironment that made the immobilized enzyme stay natural and active. Differential pulse voltammetry (DPV) demonstrates that the GOD/Au@ILs-polysome/GCE electrode exhibited improved electrocatalytic activity compared with the GOD/ILs-polysome/GCE electrode. The electrochemical sensor exhibited a low detection limit of 0.02 mM, high sensitivity of 32.52 µA mM−1 cm−2, high selectivity toward glucose, and good stability. The practical application of the sensor was verified by the determination of glucose in human serum. The multi-component liposomal nanocomposites possess universal significance in protein-based direct electrochemical devices while offering a facile route to fabricating a highly sensitive glucose sensor for practical clinical diagnosis.

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.

Aligned Carbon Nanotube Films for Immobilization of Glucose Oxidase and its Application in Glucose Biosensor

Glucose oxidase (GOx) was immobilized between aligned carbon nanotube films (ACNTFs) using a cross-stacking method without any purification and functionalization processes. Direct electron transfer of GOx was achieved on the ACNTFs with reversible redox peaks observed at the formal potential of –0.448 V. When applied to the determination of glucose by cyclic voltammetry, the prepared enzymatic electrode exhibited a linear range from 1 to 5 mM under mediator-free physiological conditions, which makes it a promising candidate for the development of third-generation glucose biosensors.

Double Biocatalysis Signal Amplification Glucose Biosensor Based on Porous Graphene.

Controllable preparation of nanopores to promote the performance of electrochemical biosensing interfaces has become one of the researching frontiers in biosensing. A double biocatalysis signal amplification of glucose biosensor for the study of electrochemical behaviors of glucose oxidase (GOx) was proposed by using horseradish peroxidase biosynthesized porous graphene (PGR) as the platform for the biocatalytic deposition of gold nanoparticles (AuNPs). The biosensor showed a linear range from 0.25 to 27.5 μM with a detection limit of 0.05 μM (S/N = 3) towards glucose. Furthermore, the proposed AuNPs/GOx–PGR modified glassy carbon electrode (AuNPs/GOx–PGR/GCE) achieved direct electron transfer of GOx.

Enhanced direct electron transfer of glucose oxidase based on gold nanoprism and its application in biosensing

Gold nanoprism (AuNP) was used for immobilization of glucose oxidase (GOD), and the direct electrochemistry of GOD–AuNP–chitosan modified GCE and glucose biosensing were studied. Transmission electron microscopy, UV–vis spectroscopy and electrochemical impendence spectroscopy were employed to confirm the morphology and film modification changes of the prepared biosensor. Results showed that the AuNP can provide a favorable and biocompatible microenvironment for facilitating the direct electron transfer between proteins and electrode surface. It was found that the special structure of gold nanoprism exhibited enhanced performances in direct electron transfer of GOD and glucose sensing. The adsorbed GOD displayed an apparent electron transfer rate constant (ks) of 24.92s−1. The constructed biosensor exhibited a good response to glucose with linear range from 0.05 to 1.2mM (R2=0.9975), low detection limit of 0.01mM and high sensitivity of 11.83μAmM−1cm−2. The proposed biosensor offers an alternative method for the determination of glucose in real samples and has potential applications in the fabrication of other biosensors with redox proteins.

Platinum nanoparticle-assembled nanoflake-like tin disulfide for enzyme-based amperometric sensing of glucose

The authors have prepared a platinum nanoparticle-assembled nanoflake-like SnS2 nanocomposite of the type PtNP@SnS2 as a support for immobilization of glucose oxidase (GOx) to obtain an electrochemical glucose biosensor based on direct electron transfer of GOx. Scanning electron microscopy, transmission electron microscopy, X-ray diffraction, electrochemical impedance spectroscopy, static water contact angle measurements, and cyclic voltammetry were used to characterize the nanocomposite and the glucose biosensor. The nanocomposite has a large surface-to-volume ratio, excellent hydrophiliciy, and high electrochemical activity. This promotes the direct electron transfer between GOx and the surface of a glassy carbon electrode (GCE). The GOx immobilized on the nanocomposite displays good bioactivity, and the surface coverage of the modified electrode is 4.15 × 10−11 mol·cm−2. Under optimum conditions and at a working voltage of −0.4 V vs. SCE, the glucose biosensor exhibits a linear response in the 0.1 to 1.0 mM and 1.0 to 12 mM glucose concentration ranges, with a lower detection limit of 2.5 μM (at an S/N ratio of 3). The biosensor shows excellent selectivity and was successfully applied to the determination of glucose in human serum samples.

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.

Nitrogen-Doped Carbon Nanotubes Supported by Macroporous Carbon as an Efficient Enzymatic Biosensing Platform for Glucose.

Effective immobilization of enzymes/proteins on an electrode surface is very essential for biosensor development, but it still remains challenging because enzymes/proteins tend to form close-packed structures on the electrode surface. In this work, nitrogen-doped carbon nanotubes (NCNTs) supported by three-dimensional Kenaf Stem-derived porous carbon (3D-KSC) (denoted as 3D-KSC/NCNTs) nanocomposites were constructed as the supporting matrix to load glucose oxidase (GOD) for preparing integrated glucose biosensors. These NCNTs are vertically arrayed on the channel walls of the 3D-KSC via the chemical vapor deposition method, which could noticeably increase the effective surface area, mechanical stability, and active sites (originating from the doped nitrogen) of the nanocomposites. The integrated glucose biosensor exhibits some advantages over the traditional GOD electrodes in terms of the capability to promote the direct electron transfer of GOD, enhance the mechanical stability of the biosensor attributed to the strong interaction between NCNTs and GOD, and enlarge the specific surface area to efficiently load a large number of GODs. The as-prepared biosensor shows a good performance toward both oxygen reduction and glucose biosensing. This study essentially offers a novel approach for the development of biosensors with excellent analytical properties.

Multifunctional Electrochemical Platforms Based on the Michael Addition/Schiff Base Reaction of Polydopamine Modified Reduced Graphene Oxide: Construction and Application.

In this paper, a new strategy for the construction of multifunctional electrochemical detection platforms based on the Michael addition/Schiff base reaction of polydopamine modified reduced graphene oxide was first proposed. Inspired by the mussel adhesion proteins, 3,4-dihydroxyphenylalanine (DA) was selected as a reducing agent to simultaneously reduce graphene oxide and self-polymerize to obtain the polydopamine-reduced graphene oxide (PDA-rGO). The PDA-rGO was then functionalized with thiols and amines by the reaction of thiol/amino groups with quinine groups of PDA-rGO via the Michael addition/Schiff base reaction. Several typical compounds containing thiol and/or amino groups such as 1-[(4-amino)phenylethynyl] ferrocene (Fc-NH2), cysteine (cys), and glucose oxidase (GOx) were selected as the model molecules to anchor on the surface of PDA-rGO using the strategy for construction of multifunctional electrochemical platforms. The experiments revealed that the composite grafted with ferrocene derivative shows excellent catalysis activity toward many electroactive molecules and could be used for individual or simultaneous detection of dopamine hydrochloride (DA) and uric acid (UA), or hydroquinone (HQ) and catechol (CC), while, after grafting of cysteine on PDA-rGO, simultaneous discrimination detection of Pb(2+) and Cd(2+) was realized on the composite modified electrode. In addition, direct electron transfer of GOx can be observed when GOx-PDA-rGO was immobilized on glassy carbon electrode (GCE). When glucose was added into the system, the modified electrode showed excellent electric current response toward glucose. These results inferred that the proposed multifunctional electrochemical platforms could be simply, conveniently, and effectively regulated through changing the anchored recognition or reaction groups. This study would provide a versatile method to design more detection or biosensing platforms through a chemical reaction strategy in the future.

Glucose biosensor based on glucose oxidase immobilized at gold nanoparticles decorated graphene-carbon nanotubes

Biopolymer pectin stabilized gold nanoparticles were prepared at graphene and multiwalled carbon nanotubes (GR-MWNTs/AuNPs) and employed for the determination of glucose. The formation of GR-MWNTs/AuNPs was confirmed by scanning electron microscopy, X-ray diffraction, UV–vis and FTIR spectroscopy methods. Glucose oxidase (GOx) was successfully immobilized on GR-MWNTs/AuNPs film and direct electron transfer of GOx was investigated. GOx exhibits highly enhanced redox peaks with formal potential of −0.40V (vs. Ag/AgCl). The amount of electroactive GOx and electron transfer rate constant were found to be 10.5×10−10molcm−2 and 3.36s−1, respectively, which were significantly larger than the previous reports. The fabricated amperometric glucose biosensor sensitively detects glucose and showed two linear ranges: (1) 10μM–2mM with LOD of 4.1μM, (2) 2mM–5.2mM with LOD of 0.95mM. The comparison of the biosensor performance with reported sensors reveals the significant improvement in overall sensor performance. Moreover, the biosensor exhibited appreciable stability, repeatability, reproducibility and practicality. The other advantages of the fabricated biosensor are simple and green fabrication approach, roughed and stable electrode surface, fast in sensing and highly reproducible.

Study of direct electron transfer and enzyme activity of glucose oxidase on graphene surface

In recent years, graphene has been widely used as a high performance two-dimensional material in the development of biosensors and biofuel cells for facilitating direct electron transfer (DET) of glucose oxidase (GOx). However, almost all of these reports perform experiments in the presence of oxygen (a natural mediator of oxidase) and whether the GOx with DET property retained their catalytic activity in the absence of mediators has not been studied in detail so far. In this paper, we investigated the DET property and enzyme activity of GOx on graphene surface without and with mediators. Experimental results showed that the biosensor had no response to glucose in mediator-free solutions, even though the DET of GOx was observed, indicating that the GOx with DET property lacked enzymatically catalytic activity. However, in the presence of mediators, the biosensor showed sensitive response to glucose, illustrating that the mediated enzymatic oxidation of glucose occurred, which can be attributed to the catalytically active GOx without DET capability. These results suggest that DET property and enzyme catalytic activity cannot occur on the same GOx simultaneously. Therefore, keeping enzyme activity and DET of GOx at the same time is still a major challenge for biosensor and biofuel cell researches.

Direct electron transfer of glucose oxidase-boron doped diamond interface: a new solution for a classical problem.

A planar boron-doped diamond (BDD) electrode was treated with KOH and functionalized with 3-aminopropyltriethoxysilane (APTES) to serve as a biosensing platform for biomolecule immobilization with glucose oxidase (GOx) as a test model. The free amino groups of GOx and APTES were cross-linked by glutaraldehyde (X), a bifunctional chemical to form a stable enzyme layer (GOx-X-APTES) on BDD. Micrographs obtained by scanning electron microscopy revealed that a mesoporous structure uniformly covered the BDD surface. Cyclic voltammetry of GOx immobilized showed a pair of well-defined redox peaks in neutral phosphate buffer solution, corresponding to the direct electron transfer of GOx. The apparent heterogeneous electron transfer rate constant of the immobilized GOx was estimated to be 8.85 ± 0.47 s(-1), considerably higher than the literature reported values. The determination of glucose was carried out by amperometry at -0.40 V, and the developed biosensor showed good reproducibility and stability with a detection limit of 20 μM. Both ascorbic and uric acids at normal physiological conditions did not provoke any signals. The dynamic range of glucose detection was further extended by covering the enzyme electrode with a thin Nafion layer. The Nafion/GOx-X-APTES/BDD biosensor showed excellent stability, a detection limit of 30 μM, a linear range between 35 μM and 8 mM, and a dynamic range up to 14 mM. Such analytical performances were compared favorably with other complicated sensing schemes using nanomaterials, redox polymers, and nanowires. The APTES-functionalized BDD could be easily extended to immobilize other redox enzymes or proteins of interests.

Direct electrochemistry and electrocatalysis of glucose oxidase immobilized on reduced graphene oxide and silver nanoparticles nanocomposite modified electrode

The direct electrochemistry of glucose oxidase (GOx) was successfully realized on electrochemically reduced graphene oxide and silver nanoparticles (RGO/Ag) nanocomposite modified electrode. The fabricated nanocomposite was characterized by field emission scanning electron microscope and energy dispersive spectroscopy. The GOx immobilized nanocomposite modified electrode showed a pair of well-defined redox peaks with a formal potential (E°) of −0.422V, indicating that the bioactivity of GOx was retained. The heterogeneous electron transfer rate constant (Ks) of GOx at the nanocomposite was calculated to be 5.27s−1, revealing a fast direct electron transfer of GOx. The GOx immobilized RGO/Ag nanocomposite electrode exhibited a good electrocatalytic activity toward glucose over a linear concentration range from 0.5 to 12.5mM with a detection limit of 0.16mM. Besides, the fabricated biosensor showed an acceptable sensitivity and selectivity for glucose.

Electrochemical Behaviors of Glucose Oxidase Based on Biocatalytic Deposition of Gold Nanoparticles

AbstractCoupling nanotechnology with biocatalysis, a highly sensitive glucose biosensor for the study of electrochemical behaviors of glucose oxidase (GOx) was proposed by using monkshoodvine root–bark like carbon (MLC) as the platform for the biocatalytic deposition of AuNPs. The biosensor showed a linear range from 0.25 to 130 μM with a detection limit of 0.1 μM (S/N = 3) towards glucose and sensitivity of 3010 μA/mM. K value was calculated to be 67.4 μM. Furthermore, the proposed AuNPs/GOx–MLC modified pyrolytic graphite electrode (AuNPs/GOx–MLC/PGE) achieved direct electron transfer of GOx. Γ* was calculated to be 2.79 × 10−11 mol/cm2 and ks was 1.79 s−1. It also showed a remarkable electrocatalysis towards glucose.

Immobilization of glucose oxidase into a nanoporous TiO2 film layered on metallophthalocyanine modified vertically-aligned carbon nanotubes for efficient direct electron transfer

Glucose oxidase (GOD) was adsorbed into a nanoporous TiO2 film layered on the surface of an iron phthalocyanine (FePc) vertically-aligned carbon nanotube (CNT) modified electrode. A Nafion film was then dropcast on the electrode's surface to improve operational and storage stabilities of the GOD-based electrode. Scanning electron microscopy (SEM) micrographs revealed the formation of FePc and nanoporous TiO2 nanoparticles along the sidewall and the tip of CNTs. Cyclic voltammograms of the GOD electrode in neutral PBS exhibited a pair of well-defined redox peaks, attesting the direct electron transfer of GOD (FAD/FADH2) with the underlying electrode. The potential of glucose electro-oxidation under nitrogen was ∼+0.12V with an oxidation current density of 65.3μAcm−2 at +0.77V. Voltammetric and amperometric responses were virtually unaffected by oxygen, illustrating an efficient and fast direct electron transfer. The modification of the CNT surface with FePc resulted in a biosensor with remarkable detection sensitivity with an oxygen-independent bioelectrocatalysis. In deaerated PBS, the biosensor displayed average response time of 12s, linearity from 50μM to 4mM, and a detection limit of 30μM (S/N=3) for glucose.

A novel glucose biosensor based on phosphonic acid-functionalized silica nanoparticles for sensitive detection of glucose in real samples

An effective strategy for preparation amperometric biosensor by using the phosphonic acid-functionalized silica nanoparticles (PFSi NPs) as special modified materials is proposed. In such a strategy, glucose oxidase (GOD) was selected as model protein to fabricate glucose biosensor in the presence of phosphonic acid-functionalized silica nanoparticles (PFSi NPs). The PFSi NPs were first modified on the surface of glassy carbon (GC) electrode, then, GOD was adsorbed onto the PFSi NPs film by drop-coating. The PFSi NPs were characterized by transmission electron microscopy (TEM) and nuclear magnetic resonance (NMR) spectra. The interaction of PFSi NPs with GOD was investigated by the circular dicroism spectroscopy (CD). The results showed PFSi NPs could essentially maintain the native conformation of GOD. The direct electron transfer of GOD on (PFSi NPs)/GCE electrode exhibited excellent electrocatalytic activity for the oxidation of glucose. The proposed biosensor modified with PFSi NPs displayed a fast amperometric response (5s) to glucose, a good linear current–time relation over a wide range of glucose concentrations from 5.00×10−4 to 1.87×10−1M, and a low detection limit of 2.44×10−5M (S/N=3). Moreover, the biosensor can be used for assessment of the concentration of glucose in many real samples (relative error<3%). The GOD biosensor modified with PFSi NPs will have essential meaning and practical application in future that attributed to the simple method of fabrication and good performance.

Enhanced Direct Electrochemistry of Glucose Oxidase and Glucose Biosensing Based on TiO&lt;sub&gt;2&lt;/sub&gt;-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.

ZnO/Cu Nanocomposite: A Platform for Direct Electrochemistry of Enzymes and Biosensing Applications

Unique structured nanomaterials can facilitate the direct electron transfer between redox proteins and the electrodes. Here, in situ directed growth on an electrode of a ZnO/Cu nanocomposite was prepared by a simple corrosion approach, which enables robust mechanical adhesion and electrical contact between the nanostructured ZnO and the electrodes. This is great help to realize the direct electron transfer between the electrode surface and the redox protein. SEM images demonstrate that the morphology of the ZnO/Cu nanocomposite has a large specific surface area, which is favorable to immobilize the biomolecules and construct biosensors. Using glucose oxidase (GOx) as a model, this ZnO/Cu nanocomposite is employed for immobilization of GOx and the construction of the glucose biosensor. Direct electron transfer of GOx is achieved at ZnO/Cu nanocomposite with a high heterogeneous electron transfer rate constant of 0.67 ± 0.06 s(-1). Such ZnO/Cu nanocomposite provides a good matrix for direct electrochemistry of enzymes and mediator-free enzymatic biosensors.

Amine functionalized TiO2–carbon nanotube composite: synthesis, characterization and application to glucose biosensing

The synthesis of amine functionalized TiO2-coated multiwalled carbon nanotubes (NH2-TiO2-CNTs) using sol–gel method was investigated. The synthesized nanocomposite was characterized with XRD, FTIR spectroscopy, BET test and SEM imaging. The results demonstrated a unique nanostructure with no destruction of the CNTs’ shape. In addition, the presence of amine groups on the composite surface was confirmed by FTIR. This nanocomposite was used for one-step immobilization of glucose oxidase (GOx) to sense glucose. The result of cyclic voltammetry showed a pair of well-defined and quasi-reversible peaks for direct electron transfer of GOx in the absence of glucose. Also, the result of electrochemical impedance spectroscopy indicated that GOx was successfully immobilized on the surface of NH2-TiO2-CNTs. Furthermore, good amperometric response showed that immobilized GOx on the NH2-TiO2-CNTs exhibits exceptional bioelectrocatalytic activity toward glucose oxidation.

Direct electron transfer of glucose oxidase at glassy carbon electrode modified with functionalized carbon nanotubes within a dihexadecylphosphate film

A glassy carbon electrode modified with functionalized multiwalled carbon nanotubes (CNTs) immobilized by 1-ethyl-3-(3-dimethylaminopropyl) carbodiimide/N-hydroxysuccinimide (EDC/NHS) in a dihexadecylphosphate film was prepared and characterized by cyclic voltammetry and scanning electron microscopy. It was used as a support for FAD or glucose oxidase (GOx) immobilization with EDC/NHS crosslinking agents. Cyclic voltammetry of GOx immobilized onto the surface of CNTs showed a pair of well-defined redox peaks, which correspond to the direct electron transfer of GOx, with a formal potential of −0.418 V vs. Ag/AgCl (3 M KCl) in 0.1 M phosphate buffer solution (pH 7.0). An apparent heterogeneous electron transfer rate constant of 1.69 s −1 was obtained. The dependence of half wave potential on pH indicated that the direct electron transfer reaction of GOx involves a two-electron, two-proton transfer. The determination of glucose was carried out by square wave voltammetry and the developed biosensor showed good reproducibility and stability. The proposed method could be easily extended to immobilize and evaluate the direct electron transfer of other redox enzymes or proteins.