Home About us Contact
|
Home About us Contact | ||
|
|
||
Glucose Oxidase (glucose + oxidase)
Kinds of Glucose Oxidase Selected AbstractsOn-line biosensors for simultaneous determination of glucose, choline, and glutamate integrated with a microseparation systemELECTROPHORESIS, Issue 18 2003Guoyue Shi Abstract An effective microseparation system integrated with ring-disc electrodes and two microfluidic devices was fabricated for in vivo determination using a microdialysis pump. The major interference of ascorbic acid (AA) was excluded by direct oxidation with ascorbate oxidase. Glucose, glutamate, and choline were successfully determined simultaneously through the biosensors modified with a bilayer of osmium-poly(4-vinylpyridine)gel-horseradish peroxidase (Os-gel-HRP)/glucose oxidase (GOD), glutamate oxidase (GlutaOD) or choline oxidase (ChOD). To stabilize the biosensors, 0.2% polyethylenimine (PEI) was mixed with the oxidases. The cathodic currents of glucose, glutamate, and choline biosensors started to increase after the standard solutions were injected into the microseparation system. The on-line biosensors show a wide calibration range (10,7,10,5 mol/L) with a detection limit of 10,8 mol/L at the working potential of ,50 mV. The variations of glucose, glutamate, and choline were determined simultaneously in a free moving rat when we perfused the medial frontal cortex with 100 ,mol/L N -methyl- D -aspartate (NMDA) solution, which is the agonist of the NMDA receptor. [source] Electrocatalytic Oxidation of Glucose by the Glucose Oxidase Immobilized in Graphene-Au-Nafion BiocompositeELECTROANALYSIS, Issue 3 2010Kangfu Zhou Abstract Graphene was successfully prepared and well separated to individual sheets by introducing SO3,. XRD and TEM were employed to characterize the graphene. UV-visible absorption spectra indicated that glucose oxidase (GOx) could keep bioactivity well in the graphene-Au biocomposite. To construct a novel glucose biosensor, graphene, Au and GOx were co-immobilized in Nafion to further modify a glassy carbon electrode (GCE). Electrochemical measurements were carried out to investigate the catalytic performance of the proposed biosensor. Cyclic voltammograms (CV) showed the biosensor had a typical catalytic oxidation response to glucose. At the applied potential +0.4,V, the biosensor responded rapidly upon the addition of glucose and reached the steady state current in 5,s, with the present of hydroquinone. The linear range is from 15,,M to 5.8,mM, with a detection limit 5,,M (based on the S/N=3). The Michaelis-Menten constant was calculated to be 4.4,mM according to Lineweaver,Burk equation. In addition, the biosensor exhibits good reproducibility and long-term stability. Such impressive properties could be ascribed to the synergistic effect of graphene-Au integration and good biocompatibility of the hybrid material. [source] Biosensor Based on Self-Assembling Glucose Oxidase and Dendrimer-Encapsulated Pt Nanoparticles on Carbon Nanotubes for Glucose DetectionELECTROANALYSIS, Issue 6 2007Lihuan Xu Abstract A novel amperometric glucose biosensor based on layer-by-layer (LbL) electrostatic adsorption of glucose oxidase (GOx) and dendrimer-encapsulated Pt nanoparticles (Pt-DENs) on multiwalled carbon nanotubes (CNTs) was described. Anionic GOx was immobilized on the negatively charged CNTs surface by alternatively assembling a cationic Pt-DENs layer and an anionic GOx layer. Transmission electron microscopy images and ,-potentials proved the formation of layer-by-layer nanostructures on carboxyl-functionalized CNTs. LbL technique provided a favorable microenvironment to keep the bioactivity of GOx and prevent enzyme molecule leakage. The excellent electrocatalytic activity of CNTs and Pt-DENs toward H2O2 and special three-dimensional structure of the enzyme electrode resulted in good characteristics such as a low detection limit of 2.5,,M, a wide linear range of 5,,M,0.65,mM, a short response time (within 5,s), and high sensitivity (30.64,,A mM,1,cm,2) and stability (80% remains after 30 days). [source] Reagentless Glucose Biosensor Based on the Direct Electrochemistry of Glucose Oxidase on Carbon Nanotube-Modified ElectrodesELECTROANALYSIS, Issue 11 2006Xiliang Luo Abstract The direct electrochemistry of glucose oxidase (GOD) was revealed at a carbon nanotube (CNT)-modified glassy carbon electrode, where the enzyme was immobilized with a chitosan film containing gold nanoparticles. The immobilized GOD displays a pair of redox peaks in pH,7.4 phosphate buffer solutions (PBS) with the formal potential of about ,455,mV (vs. Ag/AgCl) and shows a surface-controlled electrode process. Bioactivity remains good, along with effective catalysis of the reduction of oxygen. In the presence of dissolved oxygen, the reduction peak current decreased gradually with the addition of glucose, which could be used for reagentless detection of glucose with a linear range from 0.04 to 1.0,mM. The proposed glucose biosensor exhibited high sensitivity, good stability and reproducibility, and was also insensitive to common interferences such as ascorbic and uric acid. The excellent performance of the reagentless biosensor is attributed to the effective enhancement of electron transfer between enzyme and electrode surface by CNTs, and the biocompatible environment that the chitosan film containing gold nanoparticles provides for immobilized GOD. [source] Deglycosylation of Glucose Oxidase for Direct and Efficient Glucose Electrooxidation on a Glassy Carbon Electrode,ANGEWANDTE CHEMIE, Issue 32 2009Olivier Courjean Dr. Nützliche Enge: Eine Glucose-Oxidase (GOx, links) kommt im deglycosylierten Zustand (rechts) in engeren elektrischen Kontakt mit der Oberfläche einer Glaskohlenstoffelektrode als das native Enzym. Entsprechend wird Glucose auf einer Monoschicht der deglycosylierten GOx auf einer solchen Elektrode bei einem Potenzial von ,200,mV gegen Ag/AgCl direkt oxidiert, wobei eine Stromdichte von 235,,A,cm,2 erreicht wird. [source] Electrochemical Quartz Crystal Microbalance Studies on Enzymatic Specific Activity and Direct Electrochemistry of Immobilized Glucose Oxidase in the Presence of Sodium Dodecyl Benzene Sulfonate and Multiwalled Carbon NanotubesBIOTECHNOLOGY PROGRESS, Issue 1 2008Yuhua Su The electrochemical quartz crystal microbalance (EQCM) technique was utilized to monitor in situ the adsorption of glucose oxidase (GOD) and the mixture of GOD and sodium dodecyl benzene sulfonate (SDBS) onto Au electrodes with and without modification of multiwalled carbon nanotubes (MWCNTs) or SDBS/MWCNTs composite, and the relationship between enzymatic specific activity (ESA) and direct electrochemistry of the immobilized GOD was quantitatively evaluated for the first time. Compared with the bare gold electrode at which a little GOD was adsorbed and the direct electrochemistry of the adsorbed GOD was negligible, the amount and electroactivity of adsorbed GOD were greatly enhanced when the GOD was mixed with SDBS and then adsorbed onto the SDBS/MWCNTs modified Au electrode. However, the ESA of the adsorbed GOD was fiercely decreased to only 16.1% of the value obtained on the bare gold electrode, and the portion of adsorbed GOD showing electrochemical activity exhibited very low enzymatic activity, demonstrating that the electroactivity and ESA of immobilized GOD responded oppositely to the presence of MWCNTs and SDBS. The ESA results obtained from the EQCM method were well supported by conventional UV-vis spectrophotometry. The direct electrochemistry of redox proteins including enzymes as a function of their biological activities is an important concern in biotechnology, and this work may have presented a new and useful protocol to quantitatively evaluate both the electroactivity and ESA of trace immobilized enzymes, which is expected to find wider applications in biocatalysis and biosensing fields. [source] Expression of an Aspergillus niger Glucose Oxidase in Saccharomyces cerevisiae and Its Use to Optimize Fructo-oligosaccharides SynthesisBIOTECHNOLOGY PROGRESS, Issue 4 2006Magdalena Valdivieso-Ugarte Fructo-oligosaccharides (FOS) represent the most abundantly supplied and utilized group of nondigestible oligosaccharides as food ingredients. These prebiotics can be produced from sucrose using the transglycosylating activity of ,-fructofuranosidases (EC 3.2.1.26) at high concentrations of the starting material. The main problem during FOS synthesis is that the activity of the enzyme is inhibited by the glucose generated during the reaction, and therefore the maximum FOS content in commercial products reaches up to 60% on a dry substance basis. The glucose oxidase (gox) gene from Aspergillus niger BT18 was cloned and integrated, as part of an expression cassette, into the ribosomal DNA of a Saccharomyces cerevisiae host strain. One of the recombinant strains with a high copy number of the gox gene and showing a high GOX specific activity was used to produce the enzyme. Addition of the extracellular glucose oxidase to the FOS synthesis reaction helped to remove the glucose generated, avoiding the inhibition of the fungal ,-fructofuranosidase. As a result, a final syrup containing up to 90% of FOS was obtained. [source] Glucose Oxidation Catalyzed by Liposomal Glucose Oxidase in the Presence of Catalase-Containing LiposomesBIOTECHNOLOGY PROGRESS, Issue 3 2006Makoto Yoshimoto A catalase-containing liposome (CAL) was prepared and characterized in terms of stability during storage and catalysis of the decomposition of hydrogen peroxide (H2O2) that was initially added or produced in the oxidation of glucose catalyzed by the glucose oxidase-containing liposomes (GOL). The reactors used were a test tube and an external loop airlift bubble column as the static liquid and circulating liquid flow systems, respectively. The free catalase (CA) at low concentrations was unstable during storage at 4 °C as a result of dissociation of the tetrameric CA subunits. On the other hand, the deactivation of the CA activity in the CAL was depressed because of the high CA concentration in the CAL liposome. The CAL effectively catalyzed the repeated decompositions at 25 °C with 10 mM H2O2 added initially, whereas the free CA was significantly deactivated during the repeated reactions. The high stability of the CAL was attributed to the moderately depressed reactivity, which was essentially derived from the diffusion limitation of the CAL membrane to H2O2 in the liquid bulk. In the GOL-catalyzed prolonged oxidation of 10 mM glucose at 40 °C in the static liquid in a test tube, both the free CA and CAL could continuously catalyze the decomposition of H2O2 produced. This was because the glucose oxidation rate was small due to the limited reactivity of the GOL to glucose with its low permeability through the GOL membrane. In the glucose oxidation catalyzed by the GOL with the free CA or the CAL in the airlift, much larger oxidation rates were observed compared to those in the test tube because the permeability of the GOL membrane to glucose was increased in the gas-liquid two phase flow in the airlift. The GOL/CAL system in the airlift operated in an acidic condition, which was preferable to the GO activity, gave the largest oxidation rate with negligible accumulation of the H2O2 produced. On the other hand, the GOL/free CA system gave an oxidation rate smaller than that of the GOL/CAL system even under the acidic condition due to an unfavorable interaction of the free CA molecules with the GOL membranes leading to the decreased reactivity of the GOL. [source] Immobilization and Characterization of Glucose Oxidase on Single-Walled Carbon Nanotubes and Its Application to Sensing GlucoseCHINESE JOURNAL OF CHEMISTRY, Issue 4 2007Shu-Na Liu Abstract The negatively charged (at pH 8.2) glucose oxidase (GOx, pI ca. 4.2) was assembled onto the surface of single-walled carbon nanotubes (SWNT), which was covered (or wrapped) by a layer of positively charged polyelectrolyte poly(dimethyldiallylammonium chloride) (PDDA), via the electrostatic interaction forming GOx-PDDA- SWNT nanocomposites. Fourier transform infrared (FTIR), UV-Vis and electrochemical impedance spectroscopy (EIS) were used to characterize the growth processes of the nanocomposites. The results indicated that GOx retained its native secondary conformational structure after it was immobilized on the surface of PDDA-SWNT. A biosensor (Nafion-GOx-PDDA-SWNT/GC) was developed by immobilization of GOx-PDDA-SWNT nanocomposites on the surface of glassy carbon (GC) electrode using Nafion (5%) as a binder. The biosensor showed the electrocatalytic activity toward the oxidation of glucose under the presence of ferrocene monocarboxylic acid (FcM) as an electroactive mediator with a good stability, reproducibility and higher biological affinity. Under an optimal condition, the biosensor could be used to detection of glucose, presenting a typical characteristic of Michaelis-Menten kinetics with the apparent Michaelis-Menten constant of KappMca. 4.5 mmol/L, with a linear range of the concentration of glucose from 0.5 to 5.5 mmol/L (with correlation coefficient of 0.999) and the detection limit of ca. 83 µmol/L (at a signal-to-noise ratio of 3). Thus the biosensor was useful in sensing the glucose concentration in serum since the normal glucose concentration in blood serum was around 4.6 mmol/L. The facile procedure of immobilizing GOx used in present work would promote the developments of electrochemical research for enzymes (proteins), biosensors, biofuel cells and other bioelectrochemical devices. [source] Conducting Polymer Enzyme Alloys: Electromaterials Exhibiting Direct Electron TransferMACROMOLECULAR RAPID COMMUNICATIONS, Issue 14 2010Brianna C. Thompson Abstract Glucose oxidase (GOx) is an important enzyme with great potential application for enzymatic sensing of glucose, in implantable biofuel cells for powering of medical devices in vivo and for large-scale biofuel cells for distributed energy generation. For these applications, immobilisation of GOx and direct transfer of electrons from the enzyme to an electrode material is required. This paper describes synthesis of conducting polymer (CP) structures in which GOx has been entrained such that direct electron transfer is possible between GOx and the CP. CP/enzyme composites prepared by other means show no evidence of such "wiring". These materials therefore show promise for mediator-less electronic connection of GOx into easily produced electrodes for biosensing or biofuel cell applications. [source] Multistep filling of porous silicon with conductive polymer by electropolymerizationPHYSICA STATUS SOLIDI (A) APPLICATIONS AND MATERIALS SCIENCE, Issue 6 2009Kazuhiro Fukami Abstract The filling of porous silicon with polypyrrole by electropolymerization was investigated. The filling with polypyrrole proceeded preferentially along the porous silicon wall, leading to the formation of tubular structures. By repeating the porosification, the pore filling and the additional porosification, through-tubes of polypyrrole were formed in macropores. The technique to form through-tube was also applied to medium-sized pores. A double layer with polypyrrole was produced by the repetition of porosification and pore filling twice. The immobilization of glucose oxidase was performed by electropolymerization in an aqueous solution containing glucose oxidase and pyrrole. Glucose oxidase was immobilized physically in the polypyrrole film. In the double layer, the sensitivity of glucose oxidase was measured by electrochemical oxidation of hydrogen peroxide, which was produced by the enzymatic reaction of glucose oxidase to gluconolactone. When glucose oxidase was immobilized in the upper layer, glucose was detected sensitively. On the other hand, when glucose oxidase was immobilized in the lower layer, the sensing current showed a slow and a low response. (© 2009 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source] Stimulation of glucose oxidase with white linearly polarized lightBIOTECHNOLOGY PROGRESS, Issue 2 2010Anna Konieczna-Molenda Abstract Glucose oxidase (GOD) was illuminated with white linearly polarized light (WLPL). The enzyme was illuminated at room temperature in separate vessels then admixed to a reactor filled with D -glucose. The illumination of the enzyme for 60 min at 25,30°C and pH 6.5,7.0 provided its superior stimulation as proven in the oxidation of ,- D -glucose. Lyophilization of the illuminated enzyme reduced its activity by, approximately, 30%. © 2009 American Institute of Chemical Engineers Biotechnol. Prog., 2010 [source] Development of a Glucose Biosensor Using Advanced Electrode Modified by Nanohybrid Composing Chemically Modified Graphene and Ionic LiquidELECTROANALYSIS, Issue 11 2010Ho Yang Abstract Nanohybrids of chemically modified graphene (CMG) and ionic liquid (IL) were prepared by sonication to modify the electrode. The modified CMG-IL electrodes showed a higher current and smaller peak-to-peak potential separation than a bare electrode due to the promoted electron transfer rate. Furthermore, the glucose oxidase (GOx) immobilized on the modified electrode displayed direct electron transfer rate and symmetrical redox potentials with a linear relationship at different scan rates. The fabricated GOx/CMG-IL electrodes were developed selective glucose biosensor with respect to a sensitivity of 0.64,,A mM,1, detection limit of 0.376,mM, and response time of <5,s. [source] Electrochemically Induced Formation of Surface-Attached Temperature-Responsive Hydrogels.ELECTROANALYSIS, Issue 9 2010Amperometric Glucose Sensors with Tunable Sensor Characteristics Abstract Employing thermally responsive hydrogels, the design of an amperometric glucose sensor is proposed. The properties of the biosensor can be modulated upon changing the temperature. Homo- and copolymers of N -isopropylacrylamide (NIPAm) and oligo(ethylene glycol) methacrylate (OEGMA) were prepared by electrochemically induced polymerization thus yielding surface-attached hydrogels. The growth of the films as well as the change in the film thickness in dependence from the temperature were investigated by means of an electrochemical quartz crystal microbalance (EQCM). The layer thickness in the dry state ranged from 20 to 120,nm. The lower critical solution temperature (LCST) of the hydrogel increases with increasing content of the more hydrophilic OEGMA. Hence, the swelling in aqueous electrolyte is composition dependent and can be adjusted by selecting a specific NIPAm to OEGMA ratio. All homo- and copolymer films showed good biocompatibility and no fouling could be observed during exposing the surfaces to human serum albumin. For amperometric glucose detection, glucose oxidase was entrapped in the films during electrochemically-induced polymerization. Both the apparent Michaelis constant (K and the apparent maximum current (i as determined by amperometry could be adjusted both by the film composition as well as the operation temperature. [source] Engineered Pyranose 2-Oxidase: Efficiently Turning Sugars into Electrical EnergyELECTROANALYSIS, Issue 7-8 2010Oliver Spadiut Abstract Due to the recent interest in enzymatic biofuel cells (BFCs), sugar oxidizing enzymes other than the commonly used glucose oxidase are gaining more importance as possible bioelements of implantable microscale-devices, which can, for example, be used in biosensors and pacemakers. In this study we used rational and semi-rational protein design to improve the catalytic activity of the enzyme pyranose 2-oxidase (P2Ox) with its alternative soluble electron acceptors 1,4-benzoquinone and ferricenium ion, which can serve as electron mediators, to possibly boost the power output of enzymatic BFCs. Using a screening assay based on 96-well plates, we identified the variant H450G, which showed lower KM and higher kcat values for both 1,4-benzoquinone and ferricenium ion compared to the wild-type enzyme, when either D -glucose or D -galactose were used as saturating electron donors. Besides this variant, we analyzed the variants V546C and T169G/V546C for their possible application in enzymatic BFCs. The results obtained in homogeneous solution were compared with those obtained when P2Ox was immobilized on the surface of graphite electrodes and either "wired" to an osmium redox polymer or using soluble 1,4-benzoquinone as mediator. According to the spectrophotometrically determined kinetic constants, the possible energy output, measured in flow injection analysis experiments with these variants, increased up to 4-fold compared to systems employing the wild-type enzyme. [source] Electrocatalytic Oxidation of Glucose by the Glucose Oxidase Immobilized in Graphene-Au-Nafion BiocompositeELECTROANALYSIS, Issue 3 2010Kangfu Zhou Abstract Graphene was successfully prepared and well separated to individual sheets by introducing SO3,. XRD and TEM were employed to characterize the graphene. UV-visible absorption spectra indicated that glucose oxidase (GOx) could keep bioactivity well in the graphene-Au biocomposite. To construct a novel glucose biosensor, graphene, Au and GOx were co-immobilized in Nafion to further modify a glassy carbon electrode (GCE). Electrochemical measurements were carried out to investigate the catalytic performance of the proposed biosensor. Cyclic voltammograms (CV) showed the biosensor had a typical catalytic oxidation response to glucose. At the applied potential +0.4,V, the biosensor responded rapidly upon the addition of glucose and reached the steady state current in 5,s, with the present of hydroquinone. The linear range is from 15,,M to 5.8,mM, with a detection limit 5,,M (based on the S/N=3). The Michaelis-Menten constant was calculated to be 4.4,mM according to Lineweaver,Burk equation. In addition, the biosensor exhibits good reproducibility and long-term stability. Such impressive properties could be ascribed to the synergistic effect of graphene-Au integration and good biocompatibility of the hybrid material. [source] Glucosinolate Amperometric Bienzyme Biosensor Based on Carbon Nanotubes-Gold Nanoparticles Composite ElectrodesELECTROANALYSIS, Issue 13 2009V. Serafín Abstract A novel electrochemical biosensor design for glucosinolate determination involving bulk-incorporation of the enzymes glucose oxidase and myrosinase into a colloidal gold - multiwalled carbon nanotubes composite electrode using Teflon as binder is reported. Myrosinase catalyzes the hydrolysis of glucosinolate forming glucose, which is enzymatically oxidized. The generated hydrogen peroxide was electrochemically detected without mediator at the nanostructured composite electrode at E=+0.5,V vs. Ag/AgCl. Under the optimized conditions, the bienzyme MYR/GOx-Aucoll -MWCNT-Teflon exhibited improved analytical characteristics for the glucosinolate sinigrin with respect to a biosensor constructed without gold nanoparticles, i.e. a MYR/GOx-MWCNT-Teflon electrode, as well as with respect to other glucosinolate biosensor designs reported in the literature. The biosensor exhibits good repeatability of the amperometric measurements and good interassay reproducibility. Furthermore, the biosensor exhibited a high selectivity with respect to various potential interferents. The usefulness of the biosensor was evaluated by the determination of glucosinolate in Brussel sprout seeds. [source] Electrochemical Study of Anionic Ferrocene Derivatives Intercalated in Layered Double Hydroxides: Application to Glucose Amperometric BiosensorsELECTROANALYSIS, Issue 3-5 2009Christine Mousty Abstract Layered double hydroxides (Zn2Cr(OH)6X,nH2O LDH) containing (3-sulfopropyl)ferrocene-carboxylate (FcPSO3) and 1,1,-bis(3-sulfopropyl)ferrocene-carboxylate (Fc(PSO3)2) as interlayer anions (X) have been prepared by the co-precipitation method and characterized by PXRD, FTIR, SEM and XPS. The electrochemical behavior of these hybrid materials has been evaluated by cyclic voltammetry. A new amperometric biosensor based on the immobilization of glucose oxidase in ZnCr-FcPSO3 hybrid material was presented, the intercalated anions playing the role of mediators that shuttle electrons between the FAD centers in the enzyme and the electrode surface. The performance of the resulting biosensor for glucose determination under anaerobic conditions was evaluated by chronoamperometry at 0.5,V. The sensitivity (65,mA M,1 cm,2) determined in the concentration range 10,25,,M is higher than sensitivities reported for other glucose biosensors based on LDH host matrices. [source] Microflow Vessel Improving Reproducibility and Sensitivity of Electrochemical MeasurementsELECTROANALYSIS, Issue 23 2008Jan Krejci Abstract A new microflow system was designed and developed for electrochemical measurements. The electrochemical electrodes prepared using thick film technology were used in this arrangement. Results of various measurements such as simple amperometric measurement on the example of H2O2 detection, measurement with glucose oxidase (GOx) biosensor, soluble enzyme activity measurement etc. carried out using this system are reported. It was observed that the sensitivity and reproducibility of the electrochemical measurements is improved significantly. The new device performance was proved on H2O2 detection, activity of GOx measurement and heavy metals detection (measured concentration range: H2O2 10,9 to 10,1,M, glucose 10,6 to 10,2,M, activity of GOx 10,1 to 102,IU, heavy metals (Cu, Pb) 10,4 to 10,3,M). The microflow insert greatly reduces the overall size of the electrolyte vessel and measurements with sample quantity as low as 2,mL can be accomplished. [source] Glassy Carbon Electrodes Modified with Multiwall Carbon Nanotubes Dispersed in PolylysineELECTROANALYSIS, Issue 15 2008Yamile Jalit Abstract We report the analytical performance of glassy carbon electrodes (GCE) modified with a dispersion of multiwall carbon nanotubes (MWCNT) in polylysine (Plys) (GCE/MWCNT-Plys). The resulting electrodes show an excellent electrocatalytic activity towards different bioanalytes like ascorbic acid, uric acid and hydrogen peroxide, with important decrease in their oxidation overvoltages. The dispersion of 1.0,mg/mL MWCNT in 1.0,mg/mL polylysine is highly stable, since after 2 weeks the sensitivity for hydrogen peroxide at GCE modified with this dispersion remained in a 90% of the original value. The MWCNT-Plys layer immobilized on glassy carbon electrodes has been also used as a platform to build supramolecular architectures by self-assembling of polyelectrolytes based on the polycationic nature of the polylysine used to disperse the nanotubes. The self-assembling of glucose oxidase has allowed us to obtain a supramolecular multistructure for glucose biosensing. The influence of glucose oxidase concentration and adsorption time as well as the effect of using polylysine or MWCNT-Plys as polycationic layers for further adsorption of GOx is also evaluated. [source] Study on Glucose Biofuel Cells Using an Electrochemical Noise DeviceELECTROANALYSIS, Issue 14 2008Yueming Tan Abstract An electrochemical noise (ECN) device was utilized for the first time to study and characterize a glucose/O2 membraneless biofuel cell (BFC) and a monopolar glucose BFC. In the glucose/O2 membraneless BFC, ferrocene (Fc) and glucose oxidase (GOD) were immobilized on a multiwalled carbon nanotubes (MWCNTs)/Au electrode with a gelatin film at the anode; and laccase (Lac) and an electron mediator, 2,2,-azinobis (3-ethylbenzothiazoline-6-sulfonate) diammonium salt (ABTS), were immobilized on a MWCNTs/Au electrode with polypyrrole at the cathode. This BFC was performed in a stirred acetate buffer solution (pH,5.0) containing 40,mmol/L glucose in air, with a maximum power density of 8,,W/cm2, an open-circuit cell voltage of 0.29,V, and a short-circuit current density of 85,,A/cm2, respectively. The cell current at the load of 100,k, retained 78.9% of the initial value after continuous discharging for 15,h in a stirred acetate buffer solution (pH,5.0) containing 40,mmol/L glucose in air. The performance decrease of the BFC resulted mainly from the leakage of the ABTS mediator immobilized at the cathode, as revealed by the two-channel quartz crystal microbalance technique. In addition, a monopolar glucose BFC was performed with the same anode as that in the glucose/O2 membraneless BFC in a stirred phosphate buffer solution (pH,7.0) containing 40,mmol/L glucose, and a carbon cathode in Nafion-membrane-isolated acidic KMnO4, with a maximum power density of 115,,W/cm2, an open-circuit cell voltage of 1.24,V, and a short-circuit current density of 202,,A/cm2, respectively, which are superior to those of the glucose/O2 membraneless BFC. A modification of the anode with MWCNTs for the monopolar glucose BFC increased the maximum power density by a factor of 1.8. The ECN device is highly recommended as a convenient, real-time and sensitive technique for BFC studies. [source] Integrating an Enzyme-Entrapped Conducting Polymer Electrode and a Prereactor in a Microfluidic System for Sensing GlucoseELECTROANALYSIS, Issue 6 2008Po-Chin Nien Abstract In this study, the flow injection analysis was applied to the enzyme-entrapped electrode on a chip for sensing glucose. The on-chip microelectrode was fabricated by the standard photolithography in clean-room environment and the microfluidic channel height of 100,,m on the chip was formed by poly(dimethylsiloxane). The conducting polymer, poly(3,4-ethylenedioxythiophene), PEDOT, was electropolymerized to entrap the coexisting glucose oxidase (GOD) by cyclic voltammetry (CV). The amount of enzyme entrapped in the matrix measured spectroscopically was about 0.101,U/cm2. At a flow rate of 10,ml/hr, the working electrode (Pt/PEDOT/GOD, WE1) was set at 0.7,V (vs. Ag/AgCl) and sensing of H2O2 was carried out by injecting samples with various concentrations of glucose (Glu). A linear relationship between the sensing current and the glucose concentration, ranging from 1 to 20,mM, was obtained with a sensitivity of 8,nA mm,2 mM,1. The response time and the recovery time were about 30 and 230,s, respectively. For a single-potential test, the oxidation currents of 0.08,mM ascorbic acid (AA) and a blend of 0.08,mM AA and 10,mM Glu reached 31.3% and 145.5%, respectively, when compared with the oxidation current of 10,mM Glu alone. However, when a pre-reactor (WE2) was set at the same potential (0.7,V) before the main enzyme integrated electrode (WE1), the oxidation current for the above mixed solution reached 99.6% of the original one. [source] Amperometric Glucose Biosensors Based on Glassy Carbon and SWCNT-Modified Glassy Carbon ElectrodesELECTROANALYSIS, Issue 1 2008Irene Carpani Abstract Different carbonaceous materials, such as single-walled carbon nanotubes (SWCNTs) and glassy carbon submitted to an electrochemical activation at +1.80,V (vs. SCE) for 900,s, have been used with the aim of comparing their performances in the development of enzyme electrodes. Commercial SWCNTs have been pretreated with 2.2,M HNO3 for 20,h prior to use. The utility of activated GC as promising material for amperometric oxidase-based biosensors has been confirmed. With glucose oxidase (GOx) as a model enzyme, glucose was efficiently detected up to 1 mM without the use of a mediator. Both electrodes operated in stirred solutions of 0.1,M phosphate buffer (pH,5.5), containing dissolved oxygen, at a potential of ,0.40,V vs. SCE. Although the performances of the two carbonaceous materials were comparable, the biosensors based on activated GC were characterized by a practically unchanged response 40 days after the fabrication, a better signal to noise ratio, and a little worse sensitivity. In addition, the preparation procedure of such biosensors was more simple, rapid and reproducible. [source] Amperometric Glucose Biosensing of Gold Nanoparticles and Carbon Nanotube Multilayer MembranesELECTROANALYSIS, Issue 9 2007Ying Liu Abstract A novel multilayer gold nanoparticles/multiwalled carbon nanotubes/glucose oxidase membrane was prepared by electrostatic assembly using positively charged poly(dimethyldiallylammonium chloride) to connect them layer by layer. The modification process and membrane structures were characterized by atomic force microscopy, scanning electron microscopy and electrochemical methods. This membrane showed excellent electrocatalytic character for glucose biosensing at a relatively low potential (,0.2,V). The Km value of the immobilized glucose oxidase was 10.6,mM. This resulting sensor could detect glucose up to 9.0,mM with a detection limit of 128,,M and showed excellent analytical performance. [source] Biosensor Based on Self-Assembling Glucose Oxidase and Dendrimer-Encapsulated Pt Nanoparticles on Carbon Nanotubes for Glucose DetectionELECTROANALYSIS, Issue 6 2007Lihuan Xu Abstract A novel amperometric glucose biosensor based on layer-by-layer (LbL) electrostatic adsorption of glucose oxidase (GOx) and dendrimer-encapsulated Pt nanoparticles (Pt-DENs) on multiwalled carbon nanotubes (CNTs) was described. Anionic GOx was immobilized on the negatively charged CNTs surface by alternatively assembling a cationic Pt-DENs layer and an anionic GOx layer. Transmission electron microscopy images and ,-potentials proved the formation of layer-by-layer nanostructures on carboxyl-functionalized CNTs. LbL technique provided a favorable microenvironment to keep the bioactivity of GOx and prevent enzyme molecule leakage. The excellent electrocatalytic activity of CNTs and Pt-DENs toward H2O2 and special three-dimensional structure of the enzyme electrode resulted in good characteristics such as a low detection limit of 2.5,,M, a wide linear range of 5,,M,0.65,mM, a short response time (within 5,s), and high sensitivity (30.64,,A mM,1,cm,2) and stability (80% remains after 30 days). [source] Glucose Biosensor Mediated by 1,2-Diferrocenylethane in a Sono-Gel Composite ElectrodeELECTROANALYSIS, Issue 2-3 2007Barbara Ballarin Abstract An amperometric glucose biosensor was constructed based on a renewable carbon composite sono-gel matrix incorporating 1,2-diferrocenylethane as electron transfer mediator between the electrode and the active site of glucose oxidase. The enzyme was immobilized on the electrode surface by cross-linking with glutaraldehyde and bovine serum albumin. The process parameters for the fabrication of the biosensor and the influence of various experimental conditions (i.e., pH, temperature, operating potential) were investigated. Cyclic voltammetry and amperometric measurements were used to study the response of the glucose sensor, which displayed fast response time and good reproducibility. The analytical performances and the apparent Michaelis-Menten constant of the biosensor were evaluated. [source] Electrostatic Assembly of a Redox Catalysis System for Detection of GlutamateELECTROANALYSIS, Issue 24 2006Alice Abstract Interfacial assemblies capable of determining glutamate by redox catalysis are prepared by electrostatic assembly of alternating layers of ferrocene poly(allylamine) polymer and glutamate oxidase on a gold electrode. Deposition of the polymer was confirmed in cyclic voltammetry measurements by the presence of a surface wave corresponding to the oxidation of the ferrocene group. In the presence of glutamate in the adjacent electrolyte solution, the current increases and approaches a pseudosteady state, consistent with redox catalysis. Electrodes modified with glutamate oxidase had a linear response to glutamate up to 0.0045,M with sensitivity of 20,,A/cm2 and a limit of detection of 31.4,,M glutamate. An apparent Michaelis,Menten constant of 0.40(±0.13),mM for the confined glutamate oxidase was determined for this assembly. When used in flow-injection experiments, glucose oxidase modified electrodes responded to transient zones of glucose; however, the detection limits of the assemblies to the flowing stream were substantially higher than found for measurements on static solutions. [source] Study of Factors Affecting Molecular Behaviors in Phenothiazine-Mediated Biosensing by Electrochemical and Spectroscopic MethodsELECTROANALYSIS, Issue 23 2006Yetunde Abstract Reagentless glucose-detecting biosensors were constructed by incorporating a series of phenothiazine derivatives as mediators onto chitosan (CHIT) matrix via different covalent bonds, wherein glucose oxidase (GOx) was employed as the enzyme. Electrochemical studies show significant decrease in the electrocatalytic current during cyclic voltammetric and amperometric measurements, resulting from complexes formation between GOx and phenothiazine molecules. This behavior was further verified by spectroscopic studies. The decrease in the peak intensity at 258,nm is due to the gradual complexes formation over time, consistent to the decrease in the current signal in electrochemical investigations. Correlation with the molecular structures of phenothiazine derivatives reveals a strong relationship between the hydrophobicity of the mediators and the stability of the biosensor electrodes. [source] SECM Visualization of Spatial Variability of Enzyme-Polymer Spots.ELECTROANALYSIS, Issue 19-20 20062: Complex Interference Elimination by Means of Selection of Highest Sensitivity Sensor Substructures, Artificial Neural Networks Abstract Polymer spots with entrapped glucose oxidase were fabricated on glass surfaces and the localized enzymatic response was subsequently visualized using scanning electrochemical microscopy (SECM) in the generator,collector mode. SECM images were obtained under simultaneous variation of the concentration of glucose (0,6,mM) and ascorbic acid (0,200,,M), or, in a second set of experiments, of glucose (0,2,mM) and 2-deoxy- D(+)-glucose (0,4,mM). Aiming at the quantification of the mixture components discretization of the response surfaces of the overall enzyme/polymer spot into numerous spatially defined microsensor substructures was performed. Sensitivity of sensor substructures to measured analytes was calculated and patterns of variability in the data were analyzed before and after elimination of interferences using principal component analysis. Using artificial neural networks which were fed with the data provided by the sensor substructures showing highest sensitivity for glucose, glucose concentration could be calculated in solutions containing unknown amounts of ascorbic acid with a good accuracy (RMSE 0.17,mM). Using, as an input data set, measurements provided by sensing substructures showing highest sensitivity for ascorbic acid in combination with the response of the sensors showing highest dependence on the glucose concentration, the error of the ascorbic acid concentration calculation in solution containing the unknown amount of glucose was 10,,M. Similarly, prediction of the glucose concentration in the presence of 2-deoxy- D(+)-glucose was possible with a RMSE of 0.1,mM while the error of the calculation of 2-deoxy- D(+)-glucose concentrations in the presence of unknown concentrations of glucose was 0.36,mM. [source] Miniature Biofuel Cells with Improved Stability Under Continuous OperationELECTROANALYSIS, Issue 19-20 2006Michael Abstract We have developed miniature biofuel cells (BFCs) with dimensions as small as 12×12×9,mm by adopting the design of stackable proton exchange membrane (PEM) fuel cells. The enzymatic anodes were constructed by using stabilized glucose oxidase (GOx) in the form of crosslinked enzyme clusters (CECs) on the surface of carbon nanotubes (CNTs). The combination of stabilized GOx and unbuffered fuel solution resulted in stabilized performance of miniature BFCs under continuous operation for more than 16 hours. This unprecedentedly high operational stability of miniature BFCs opens up new possibilities for many BFC applications. [source] | |||||||||||||||||||||||||||||||||||||