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Immobilized Glucose Oxidase (immobilized + glucose_oxidase)
Selected AbstractsElectrochemical 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] 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] Glucose-Responsive Bioinorganic Nanohybrid Membrane for Self-Regulated Insulin ReleaseADVANCED FUNCTIONAL MATERIALS, Issue 9 2010Claudia R. Gordijo Abstract A bioinorganic nanohybrid glucose-responsive membrane is developed for self-regulated insulin delivery analogous to a healthy human pancreas. The application of MnO2 nanoparticles as a multifunctional component in a glucose-responsive, protein-based membrane with embedded pH-responsive hydrogel nanoparticles is proposed. The bio-nanohybrid membrane is prepared by crosslinking bovine serum albumin (BSA),MnO2 nanoparticle conjugates with glucose oxidase and catalase in the presence of poly(N -isopropyl acrylamide- co -methacrylic acid) nanoparticles. The preparation and performance of this new nanocomposite material for a glucose-responsive insulin release system is presented. The activity and stability of immobilized glucose oxidase and the morphology and mechanical properties of the membrane are investigated. The enzymatic activity is well preserved in the membranes. The use of MnO2 nanoparticles not only reinforces the mechanical strength and the porous structure of the BSA-based membrane, but enhances the long-term stability of the enzymes. The in vitro release of insulin across the membrane is modulated by changes in glucose concentration mimicking possible fluctuations of blood-glucose level in diabetic patients. A four-fold increase in insulin permeation is observed when the glucose concentration is increased from normal to hyperglycemic levels, which returns to the baseline level when the glucose concentration is reduced to a normal level. [source] Determination of serum glucose by horseradish peroxidase-catalysed imidazole chemiluminescence coupled to a micro-flow-injection systemLUMINESCENCE: THE JOURNAL OF BIOLOGICAL AND CHEMICAL LUMINESCENCE, Issue 5 2007Osamu Nozaki Abstract The reactivity of flow-injection (FI)-horseradish peroxidase (HRP)-catalysed imidazole chemiluminescence (CL) was studied for continuous determination of hydrogen peroxide (H2O2) and serum glucose with immobilized glucose oxidase. Light emission by the HRP-catalysed imidazole CL was obtained when immobilized HRP, alkaline imidazole (in Tricine solution, pH 9.3) and H2O2 were reacted at room temperature. The optimal pH for the CL reaction was 9.3 and the optimal concentration of imidazole was 100 µmol/L. When no imidazole was added, the light intensity of the same H2O2 specimen decreased to a level that could not be quantitatively determined. The spectrum of the light emitted by imidazole CL was in the range 400,600 nm with a peak at 500 nm. The calibration equation for determination of H2O2 was y = 9860x2 + 3830x + 11 700, where y = light intensity (RLU) and x = concentration of H2O2 (µmol/L). The detection limit of H2O2 was 5 pmol, and the reproducibility of the H2O2 assay was 2.3% of the coefficient of variation (H2O2 48 µmol/L, n = 13). The CL method was successfully applied to assay glucose after on-line generation of H2O2 with the immobilized glucose oxidase column, resulting in good reproducibility (CV = 3.3% and 1.0% for the standard glucose and the control serum, respectively). Copyright © 2007 John Wiley & Sons, Ltd. [source] Real-Time Monitoring of Mass-Transport-Related Enzymatic Reaction Kinetics in a Nanochannel-Array ReactorCHEMISTRY - A EUROPEAN JOURNAL, Issue 33 2010Su-Juan Li Abstract To understand the fundamentals of enzymatic reactions confined in micro-/nanosystems, the construction of a small enzyme reactor coupled with an integrated real-time detection system for monitoring the kinetic information is a significant challenge. Nano-enzyme array reactors were fabricated by covalently linking enzymes to the inner channels of a porous anodic alumina (PAA) membrane. The mechanical stability of this nanodevice enables us to integrate an electrochemical detector for the real-time monitoring of the formation of the enzyme reaction product by sputtering a thin Pt film on one side of the PAA membrane. Because the enzymatic reaction is confined in a limited nanospace, the mass transport of the substrate would influence the reaction kinetics considerably. Therefore, the oxidation of glucose by dissolved oxygen catalyzed by immobilized glucose oxidase was used as a model to investigate the mass-transport-related enzymatic reaction kinetics in confined nanospaces. The activity and stability of the enzyme immobilized in the nanochannels was enhanced. In this nano-enzyme reactor, the enzymatic reaction was controlled by mass transport if the flux was low. With an increase in the flux (e.g., >50,,L,min,1), the enzymatic reaction kinetics became the rate-determining step. This change resulted in the decrease in the conversion efficiency of the nano-enzyme reactor and the apparent Michaelis,Menten constant with an increase in substrate flux. This nanodevice integrated with an electrochemical detector could help to understand the fundamentals of enzymatic reactions confined in nanospaces and provide a platform for the design of highly efficient enzyme reactors. In addition, we believe that such nanodevices will find widespread applications in biosensing, drug screening, and biochemical synthesis. [source] | ||||||||||