Oxidation Current Of Glucose Research Articles

α-MnO2 with a cryptomelane structure for the non-enzymatic glucose electrooxidation in a neutral medium

A high demand for non-enzymatic glucose sensors and continuous glucose monitoring systems encourages the development of stable and active catalysts for the enzymeless anodic oxidation of glucose in the neutral medium. In regard to this reaction, we analyze the prospects of alpha manganese dioxide with a cryptomelane structure synthesized via an aqueous chemical route. To provide various specific surface area, the hydrated α-MnO2 oxide is annealed in a wide temperature range from 60 to 700 °C. Furthermore, we investigate the influence of the oxide annealing temperature on the amount of crystal water, chemical composition, morphology, electrochemical recharging behavior, electrocatalytic activity and stability in the glucose oxidation carried out in an isotonic NaCl-based phosphate-buffered saline (pH 7.40). To solidly determine potentials of the irreversible cathodic dissolution of α-MnO2 as well as O2/Cl2 evolution on α-MnO2, a rotating ring-disk electrode is applied. For the most active α-MnO2 sample with the 100 μg cm−2geo loading the glucose oxidation current of ca. 40 μA cm−2geo after 1 h at +0.8 V (SCE) for 7 mM of glucose is achieved. The linear concentration dependence in a physiological glucose range (1–30 mM) with the sensitivity of ca. 17.8 μA mM−0.5 cm−2geo at 25 °C is observed. Finally, glucose selectivity of α-MnO2 in relation to fructose, galactose, xylose, ribose, urea, lactic acid, acetone, ascorbic acid and paracetamol is revealed.

Nickel foam-decorated hollow-Co3O4/GO nanocomposites: A highly sensitive non-enzymatic electrochemical sensor for glucose detection

Cobalt-based nanomaterials, characterized by multiple oxidation states and high stability in alkaline environments, have been found extensive applications in glucose detection. In this study, a cobalt-based zeolitic imidazolate framework (ZIF-67) was employed as a precursor, where Co2+ was coordinated with carboxyl groups of oxidized graphene oxide (GO), resulting in the formation of cobalt-based nanoparticles. The integration of Co2+ with GO established a novel cobalt-based nanomaterial with potential implications for glucose detection. At a calcination temperature of 260 °C, the calcination process extended for 4 h, fulfilling the synthesis of Hollow-Co3O4/GO nanocomposites. These nanocomposites were subsequently engaged as electrochemical electrodes for glucose detection through the impregnation method. The distinctive structure of Hollow-Co3O4/GO has spurred mutual promotion of the reoxidation reactions at the interface, culminating in a substantial augmentation of the specific surface area and a consequent considerable surge in the glucose oxidation current. In addition, due to the retention of the structure of MOFs, the pores can be used to adsorb glucose molecules, which is conducive to the accurate detection of the reaction. Under optimal conditions, the sensitivity of the Hollow-Co3O4/GO modified electrode hits 1582.7 μA mmol−1 cm−2, with a detection limit of 0.49 μmol/L (S/N = 3) and a response time of approximately 2 s. These achievements have emphasized the promising applicability of Hollow-Co3O4/GO nanocomposites as an active material for practical electrochemical biosensors.

Enzyme electrode for glucose oxidation using low‐solubility 4‐aminodiphenylamine derivatives as electron mediator

AbstractA novel enzyme electrode system for glucose oxidation was constructed by co‐immobilization of glucose dehydrogenase (GDH) and N,N’‐diphenyl‐p‐phenylenediamine (DPPD) on carbon electrodes. This enzyme electrode system was applied to porous carbon fabric to produce a glucose oxidation current of 7 mA/cm2, while the electrode catalytic activity was maintained at approximately 100% for more than 4 h, indicating that DPPD molecules were stably retained on the electrodes during the continuous redox cycling. Further, a stable mediation was also observed for other 4‐aminodiphenylamine derivatives similar to DPPD. The difference was found in the adsorptivity between the reduced and oxidized forms of DPPD on the carbon electrode, suggesting that a portion of oxidized DPPD can access the active center of GDH without desorbing to solution. This electrode system with 4‐aminodiphenylamine derivatives can be used in sensors for glucose monitoring and to anodes of separator‐free glucose fuel cells.

Ni-doped, urchin-like Bi2S3 particles for electrocatalytic oxidation of glucose

In order to develop non-noble metal-based electrocatalysts for glucose oxidation, the Ni-doped, urchin-like Bi2S3 particles were prepared by a solvothermal method using the solvent of ethylene glycol/H2O. The obtained products were characterized by scanning electron microscopy, transmission electron microscopy, X-ray photoelectron spectroscopy and X-ray diffraction. The background signal from capacitance current is relatively low and the electrocatalytic oxidation current of glucose relatively high due to the urchin-like nanostructure of Bi2S3 particles and high surface area where the presence of Bi also improves the electrocatalytic performance of Ni[Formula: see text]/Ni[Formula: see text] shift.

(Invited) Metal Nanoparticles Modified Carbon Film Electrodes for Chemical Sensing

Electrocatalytic performance of metal nanoparticles (NPs) has been studied to apply for electrochemical devices such as fuel cells and electrochemical sensors. We have developed metal NPs embedded carbon film electrodes by co-sputtering of metal and carbon [1]. Various kinds of metals including Pt, Pd, Au, Ni, Cu and their alloys can be fabricated in the carbon film by using unbalanced magnetron (UBM) sputtering and applied for detecting hydrogen peroxide, glucose [1], heavy metals [2,3] and sugar markers [4, 5]. The electrocatalytic activity of metal NPs can be modulated by changing electronegativity of neighbor materials. Here, we proposed two electrode structures to modulate the electrocatalytic activity of metal NPs by forming metal NPs on hybrid carbon film electrodes, The electrodes were then applied applied for detecting small organic molecules such as alcohols and sugars.The first electrode structure is Ni(OH)2 NPs electrodeposited on the surface of nitrogen terminated carbon film electrodes. The carbon film was formed by UBM sputtering and the surface was treated by N2 plasma. After treatment, the NiNPs were electrodeposited by applying negative potential(Fig.1 left figure of Electrode Fabrication). The size of NiNPs became smaller by decreasing potential from -1000 to -1300 mV. By taking account of this property, we adjusted the potential to obtain similar NiNPs size on both N2 plasma treated and untreated carbon surfaces. After deposition, the potentials of both electrodes were cycled between 0 and 0.70 V (vs Ag/AgCl) to form surface Ni(OH)2. The redox reaction peaks of Ni(OH)2 oxidation and NiOOH reduction shifted positive and negative directions, respectively at Ni(OH)2 modified untreated carbon film(Fig.1 centor figure of Electrode Fabrication). with increasing potential scan rate. In contrast , peak separation increase at Ni(OH)2 modified N2 plasma treated carbon film is greatly decreased suggesting fast redox reaction. We applied both electrodes for electrocatalytic oxidation of glucose in alkaline media(Fig.1 left of Applications). The oxidation current of glucose at Ni(OH)2 modified N2 plasma treated carbon film electrode shows much larger current than that at Ni(OH)2 modified N2 untreated carbon film electrode. The current of former electrode continued to slightly increase when the glucose concentration is around 7 mM. In contrast, the current of latter electrode was saturated below 3 mM. The other structure we proposed was fabricated by electroplating the Ni onto PdNPs or AuNPs embedded carbon film electrodes. By using the overpotential difference between PdNPs and carbon surface, we successfully electrodeposited NiNPs selectively only on the embedded PdNPs, resulting Ni-Pd heterodimer structure on the electrode surface(Fig.1 right of Electrode Fabrication). The average size of deposited NiNPs onto PdNPs is smaller than that deposited on the pure carbon film electrode because the embedded PdNPs worked as growth core of NiNPs. We cycled the potential in strong alkaline solution to form Ni(OH)2 on the surface of NiNPs. The oxidation peak potential of Ni(OH)2 /Pd heterodimers, which corresponds to surface NiOOH formation reaction, slightly increases with increasing the scan rates from 1 mV/s to 100 mV/s. In contrast, the oxidation peak potential of Ni(OH)2 NP modified pure carbon film(Fig.1 center figure of Electrode Fabrication) shifted more positively (about 0.2 V) with increasing the scan rate, which suggests that the oxidation and reduction cycle of Ni(OH)2 /Pd heterodimer is much faster than that of Ni(OH)2 NP. Both electrodes were applied to electrochemically oxidize methanol. When the concentration of methanol is below 1M, the sensitivity of Ni(OH)2 NP modified carbon film electrode is relatively higher than that at Ni(OH)2 /Pd heterodimer modified carbon film electrode. However, the curent at Ni(OH)2 /Pd heterodimer modified electrodes was superior to that at Ni(OH)2 NP modified electrode when the methanol concentration was higher than 1 M (Fig.1 right figure of Applications). This could be due to the fast regeneration of catalytic sites (NiOOH) resulting in higher turnover rates for methanol oxidation reaction. The above behavior of Ni(OH)2 /Pd heterodimer modified carbon film electrode could be more suitable for energy device such as fuel cell electrode and Ni(OH)2 modified carbon film electrode is more suitable to detect alcohol sensing electrode.In conclusion, the electrocatalytic activity of NiNPs can be largely modulated by changing substrates, suggesting that the design of electrode surfaces are very important to realize high performance electrodes for chemical sensors.

Significantly enhanced activity of ZIF-67-supported nickel phosphate for electrocatalytic glucose oxidation

Nickel-based nanoparticles have been widely used in detection of glucose due to its multiple oxidation states and high stability in alkaline environment. In this work, amorphous nickel phosphate was supported by Co-based zeolitic imidazolate framework (ZIF-67) through ion exchange to prepare Ni3(PO4)2@ZIF-67 composites as the electrode material. In comparison to glassy carbon electrode (GCE), Ni3(PO4)2/GCE and ZIF-67/GCE, the Ni3(PO4)2@ZIF-67/GCE showed significantly enhanced performances in electrocatalytic oxidation of glucose. The great improvement on glucose oxidation current could be ascribed to the unique structure of Ni3(PO4)2@ZIF-67, the mutual promotion between Ni(III)/Ni(II) and Co(IV)/Co(III) interfacial redox reactions and increased surface areas. Under optimum conditions, as-prepared Ni3(PO4)2@ZIF-67/GCE showed an ultra-high sensitivity of 2783 μA mM−1 cm−2 with a wide linear ranged from 1.0 μM to 4.0 mM, and a low limit detection of 0.7 μM at a signal-to-noise ratio of 3. Moreover, Ni3(PO4)2@ZIF-67/GCE were successfully applied to detect glucose of human serum with good recoveries (92–109%), which indicated that Ni3(PO4)2@ZIF-67 can found application in the clinical detection.

Glucose biosensor based on open-source wireless microfluidic potentiostat

Wireless potentiostats capable of cyclic voltammetry and amperometry that connect to the Internet are emerging as key attributes of future point-of-care devices. This work presents an “integrated microfluidic electrochemical detector” (iMED) three-electrode multi-potentiostat designed around operational amplifiers connected to a powerful WiFi-based microcontroller as a promising alternative to more expensive and complex strategies reported in the literature. The iMED is integrated with a microfluidic system developed to be controlled by the same microcontroller. The iMED is programmed wirelessly over a standard WiFi network and all electrochemical data is uploaded to an open-source cloud-based server. A wired desktop computer is not necessary for operation or program uploading. This method of integrated microfluidic automation is simple, uses common and inexpensive materials, and is compatible with commercial sample injectors. An integrated biosensor platform contains four screen-printed carbon arrays inside 4 separate microfluidic detection chambers with Pt counter and pseudo Ag/AgCl reference electrodes in situ. The iMED is benchmarked with K3[Fe(CN)6] against a commercial potentiostat and then as a glucose biosensor using glucose-oxidising films of [Os(2,2′-bipyridine)2(poly-vinylimidazole)10Cl] prepared on screen-printed electrodes with multi walled carbon nanotubes, poly(ethylene glycol) diglycidyl ether and flavin adenine dinucleotide-dependent glucose dehydrogenase. Potential application of this cost-effective wireless potentiostat approach to modern bioelectronics and point-of-care diagnosis is demonstrated by production of glucose oxidation currents, under pseudo-physiological conditions, using mediating films with lower redox potentials.

A novel non-enzymatic glucose sensor based on melamine supported CuO nanoflakes modified electrode

In the present work, we describe a simple electrochemical synthesis of CuO nanoflakes (CuO-NFs) using Cu-melamine complex. The as-prepared CuO nanoflakes was characterized by different physicochemical methods such as high-resolution scanning electron microscopy, elemental analysis and elemental mapping. The effect of different potential cycling towards the morphology of CuO-NFs was studied and discussed. Furthermore, CuO-NFs modified electrode was used as an electrocatalyst for oxidation of glucose in 0.1 M NaOH, and the observed electrochemical oxidation current of glucose was higher than CuNPs modified electrode. Amperometric i-t method was used for the determination of glucose using CuO-NFs modified electrode. Under optimal conditions, the amperometric i-t response of the sensor was linear over the glucose concentrations ranging from 1.0 µM to 1.445 mM with the detection limit of 0.35 µM. In addition, the selectivity of the sensor was tested in the presence of different potentially interfering compounds. The practicality of the sensor was also evaluated in human serum samples and shows acceptable recovery of glucose.

The effect of surface termination on glucose oxidation using Ni‐modified diamond electrodes

AbstractAbstractauthoren This study describes the decoration of hydrogen‐ and oxygen‐terminated boron‐doped diamond electrodes (BDD) with three different loadings of Ni. The Ni was deposited electrochemically for 600, 400, and 100 s on both hydrogen‐terminated BDD (BDDH) and oxygen‐terminated BDD (BDDO). Scanning electron microscopy (SEM) showed that all Ni particles were roughly spherical in shape, but distribution and size varied with electrode termination: a uniform coverage with a particle size dependent on deposition duration was achieved on BDDH, but on BDDO the particles are deposited primarily along surface ridges and had similar sizes for all three deposition times. The performance of the samples was then tested using glucose sensing as an exemplar application. It was found that glucose oxidation varies greatly between electrodes at concentrations similar to those found in human blood. The variability between the samples was attributed to surface differences between electrodes and the difference in particle location. Amperometry using BDDs decorated with the 100 s Ni deposition gave a stable current response with respect to glucose concentration in the range 0.1–13 mM with much higher glucose oxidation currents being observed for the Ni nanoparticles deposited on the hydrogenated diamond surface.

Self-assembly of palladium nanoparticles on functional TiO2 nanotubes for a nonenzymatic glucose sensor

Polydiallyldimethylammonium chloride, PDDA, was used as a stabilizer and linker for functionalized TiO2 nanotubes (TiO2 NTs). Self-assembled process with palladium nanoparticles (NPs) was successfully synthesized and used for the oxidation of glucose on glassy carbon electrodes. Based on the voltammetric and amperometric results, Pd NPs efficiently catalyzed the oxidation of glucose at −0.05V in the presence of 0.1M NaCl and showed excellent resistance toward interference poisoning from such interfering species as ascorbic acid, uric acid and urea. To further increase sensitivity, the Pd NPs-PDDA-TiO2 NTs/GCE was electrochemically treated with H2SO4 and NaOH, the glucose oxidation current was magnified 2.5 times than that before pretreatments due to greatly enhancing the electron transport property of the sensor based on the increased defect sites and surface oxide species. In view of the physiological level of glucose, the wide linear concentration range of glucose (4×10−7–8×10−4M) with a detection limit of 8×10−8M (S/N=3) was obviously good enough for clinical application.

Insect biofuel cell using an electrode with gold nanoparticles deposited by sputtering

A high-stability living battery that uses a metallic catalyst for glucose oxidation instead of enzymes is investigated. In this battery, glucose in insect haemolymph is oxidised by a gold nanoparticle (AuNP)-modified electrode, which is utilised as the anode of the battery. The AuNP-modified electrode was fabricated by sputtering gold onto a carbon cloth in a low-vacuum state. First, the oxidation performance values of glucose were evaluated and the oxidation current of glucose was obtained by the AuNP-modified electrode from cockroach haemolymph (CHL). Then, the electrocatalytic stability of the AuNP-modified electrode was compared with an enzymatic electrode. Furthermore, a glucose biofuel cell consisting of the AuNP-modified electrode and a bilirubin oxidase-modified electrode was constructed; the respective power densities obtained from 100 mM glucose solution and CHL were 22.4 and 15.1 µW/cm2, respectively. It is concluded that AuNPs are a useful catalyst for living batteries.

Glucose oxidation by osmium redox polymer mediated enzyme electrodes operating at low potential and in oxygen, for application to enzymatic fuel cells

Graphite electrodes modified with a redox polymer, [Os(4,4′- dimethoxy-2,2′-bipyridine)2(polyvinyl imidazole)10Cl]Cl (E°′=−0.02V vs Ag/AgCl), crosslinked with glucose oxidising enzymes and various amounts of multi-walled carbon nanotubes are investigated for current generation in the presence of glucose in physiological buffer solutions. Enzyme electrodes based on glucose oxidase and FAD-dependent glucose dehydrogenase are compared in the presence and absence of oxygen. The highest glucose oxidation currents are produced from enzyme electrodes containing 68% w/w multi-walled carbon nanotubes in the deposition matrix. The FAD-dependent glucose dehydrogenase and glucose oxidase enzyme electrodes provide similar current density of ∼0.8mA cm−2 in de-oxygenated 50mM phosphate-buffered saline at 37°C containing 5mM glucose concentration. Current densities under the same conditions, but in the presence of oxygen are 0.50mAcm−2 and 0.27mAcm−2, for glucose dehydrogenase and glucose oxidase enzyme electrodes, respectively, with decreased currents a result of oxygen reduction by the redox polymer in both cases, and oxygen acting as a co-substrate for the glucose oxidase-based electrodes. Application of the anodes in membrane-less enzymatic fuel cells is demonstrated by connection to cathodes prepared by co-immobilisation of [Os(2,2′-bipyridine)2(polyvinyl imidazole)10Cl]Cl redox polymer, Myrothecium verrucaria bilirubin oxidase and multi-walled carbon nanotubes on graphite electrodes. Power densities of up to 270μWcm−2 are achieved, showing promise for in vivo or ex vivo power generation under these conditions.

Non-enzymatic sensing of glucose at neutral pH values using a glassy carbon electrode modified with carbon supported Co@Pt core-shell nanoparticles

Co@Pt core-shell nanoparticles (NPs) were synthetized by a two-step reductive method using carbon (Vulcan XC-72) as a solid support. The NPs were characterized by X-ray diffraction, field emission gun scanning electron microscopy, energy dispersive X-ray spectroscopy, and transmission electron microscopy. Their electrochemical performance was evaluated by cyclic voltammetry, electrochemical impedance spectroscopy and chronoamperometry, and these showed that the Co@Pt NPs display an electrocatalytic activity towards the oxidation of glucose that is much better than that of plain Pt NPs. Under optimized conditions and at pH 7.0, the oxidation current of glucose at a working potential of −50 mV (vs. SCE) is linearly related to its concentration in the 1.0 to 30 mM range, and the detection limit is 0.3 mM (S/N = 3). It therefore covers the clinical range. The sensor also exhibits excellent stability and repeatability.

A highly sensitive non-enzymatic glucose sensor based on PtxCo1−x/C nanostructured composites

Platinum–cobalt (PtxCo1−x, x=0.70, 0.55) alloy nanoparticles have been successfully fabricated by the chemical reduction method, using carbon (Vulcan XC-72) as support. The physical properties of the materials were characterized by X-ray diffraction, and transmission electron microscopy, respectively. The electrochemical performance of the PtxCo1−x/C catalysts was evaluated by cyclic voltammetry, electrochemical impedance spectroscopy and chronoamperometry. Electrochemical measurements indicated that the oxidation current of glucose is linear to its concentration from 0.10 to 14.20mM with high sensitivity of 73.60μAmM−1cm−2. In addition, the interference from the oxidation of fructose, uric acid, acetamidophenol and ascorbic acid could be effectively avoided. Meanwhile, the non-enzymatic glucose sensors exhibited excellent selectivity, stability and repeatability. Thus, this novel non-enzyme sensor has potential application in glucose detection.

PtxNi/C nanostructured composites fabricated by chemical reduction and their application in non-enzymatic glucose sensors

Platinum–cobalt PtxNi alloy nanoparticles have been successfully fabricated by the chemical reduction method, using carbon (Vulcan XC-72) as support. The resulting modified glassy carbon electrode shows excellent catalytic activity for the oxidation of glucose. Under physiological conditions, the oxidation current of glucose has two specific linear ranges of 2.0−420μM and 0.5–8.5mM, with high sensitivities of 1795.1μAmM−1cm−2 and 707.72μAmM−1cm−2, respectively. In addition, interference from the oxidation of ascorbic acid, uric acid, or acetamidophenol could be effectively avoided. The non-enzymatic glucose sensors based on this electrode exhibited excellent selectivity, stability, and repeatability. Thus, this novel non-enzyme sensor has potential application in glucose detection.

An Interference‐Free Glucose Biosensor Based on an Anionic Redox Polymer‐Mediated Enzymatic Oxidation of Glucose

Herein a novel strategy for the construction of an amperometric biosensor for highly sensitive and selective determination of glucose is described. The biosensor is made of a biocomposite membrane of glucose oxidase (GOx) and an Os(bpy)2 (bpy=2,2'-bipyridine)-based anionic redox polymer (Os-RP) mediator. The biosensor is fabricated through the co-immobilization of GOx and the Os-RP on the surface of a glassy carbon electrode by a simple one-step chemical crosslinking process. The crosslinked Os-RP/GOx composite membrane shows excellent catalytic activity toward the oxidation of glucose. Under optimal experimental conditions, a linear correlation between the oxidation current of glucose in amperometry at 0.25 V (vs. Ag/AgCl) and glucose concentration up to 10 mM with a sensitivity of 16.5 μA mM(-1) cm(-2) and a response time <5 s. Due to the presence of anionic sulfonic acid groups in the backbone of the redox polymer, the biosensor exhibits excellent selectivity to glucose in the presence of ascorbic acid and uric acid. The low hydrophobicity of the composite membrane also effectively retards the transport of molecular oxygen within the membrane.

Ultrafine CuO nanoparticles isolated by ordered mesoporous carbon for catalysis and electroanalysis

Ultrafine CuO nanoparticles (UCNs) were well-isolated in the nano-channels of ordered mesoporous carbon (OMC) via a double solvent procedure. In this approach, uniform OMC meso-channels of large surface area acted as nanoreactors embedded with small nanoparticles. n-Hexane was used as hydrophobic solvent to disperse OMC, and hydrophilic Cu(NO3)2 aqueous solution served as a precursor to fill the nano-channels. The interfacial force between double solvents of Cu(NO3)2 and n-hexane facilitated the precursor filling within the OMC mesopores, and the subsequent heat treatment triggered in situ isolation of UCNs within OMC porous channels. This final product was denoted as UCNs@OMC, and the structure and morphology of UCNs@OMC were characterized by X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), scanning electron microscopy (SEM), transmission electron microscopy (TEM) and N2-sorption. Increased glucose oxidation currents implied the accessibility of the active catalytic sites of UCNs@OMC, and an UCNs@OMC based glucose sensor was fabricated and tested exhibiting good reproducibility and selectivity.

High-density gold nanoparticles on multi-walled carbon nanotube films: a sensitive electrochemical nonenzymatic platform of glucose

In this study, a simple electrochemical method for grafting high-density gold nanoparticles (GNPs) on Congo red functionalised multi-walled carbon nanotube (MWNT–CR) films was reported. The GNP-decorated MWNT–CR composite (GNP–MWNT–CR), prepared by the constant potential deposition of GNPs on MWNT–CR films, had a compact and uniform nanostructure with a large surface area. Electrochemical characterisations showed that the GNP–MWNT–CR film exhibited excellent catalytic activity towards the direct electrochemical oxidation of glucose in basic media, with a much higher sensitivity than MWNT films, GNP films and GNP-coated MWNT films (GNP–MWNT). Under optimal working conditions, the oxidation current of glucose at the GNP–MWNT–CR film increased linearly with its concentration in the range 5.0 µM–37.0 mM with a low detection limit of 0.5 µM (S/N = 3). This glucose electrochemical sensor was applied to the determination of glucose in human serum samples and the results were satisfied.

Fabrication of polymeric electron-transfer mediator/enzyme hydrogel multilayer on an Au electrode in a layer-by-layer process

The layer-by-layer (LBL) construction of an enzyme electrode covered with a multilayer structure alternately composed of a polymeric electron transfer mediator and a polymer-modified enzyme was examined. Poly(2-methacryloyloxyethyl phosphorylcholine-co-p-vinylphenylboronic acid-co-vinylferrocene) (PMVF) was synthesized and used as a polymeric electron transfer mediator. Glucose oxidase (GOx) was selected as a model enzyme and poly(vinyl alcohol) (PVA) chains were bound to the GOx (GOx-PVA) under mild conditions. The PMVF and PVA formed a gel spontaneously through a selective reaction between phenylboronic acid units and hydroxyl groups in both polymers. Using the spin coating technique, a repeating PMVF/GOx-PVA multilayer was fabricated on the surface of an Au electrode. The thickness of each PMVF/GOx-PVA layer was around 5.8nm, corresponding to the dimensions of GOx. The electrochemical performance of the electrode was evaluated in glucose concentration measurement. The oxidation current of glucose by GOx was measured at 0.38V (vs. Ag/AgCl), verifying that ferrocene units in the PMVF of the hydrogel electrically wired the immobilized GOx. Moreover, the current increased with the number of PMVF/GOx-PVA layers. That is, both intermolecular electron transfer between each individual layer and the presence of a freely diffusing substrate in the hydrogel were achieved. We conclude that a LBL structure constructed from PMVF and a PVA-modified enzyme is effective for use in developing bioelectronic devices that employ enzyme molecules.

Crosslinked redox polymer enzyme electrodes containing carbon nanotubes for high and stable glucose oxidation current

Co-immobilisation approaches for preparation of glucose-oxidising films of [Os(2,2'-bipyridine)(2)(poly-vinylimidazole)(10)Cl] and glucose oxidase on glassy carbon electrodes are compared. Electrodes prepared by crosslinking using glutaraldehyde vapour, without and with a NaBH(4) reduction, provide higher glucose oxidation current than those prepared using a well-established diepoxide method. Addition of multi walled carbon nanotubes to the film deposition solutions produces an enhanced glucose oxidation current density of 5 mA cm(-2) at 0.35 V vs. Ag/AgCl, whilst improving the operational stability of the current signal. Carbon nanotube, glutaraldehyde vapour crosslinked, films on electrodes, reduced by NaBH(4), retain 77% of initial catalytic current over 24 hours of continuous amperometric testing in a 37 °C, 50 mM phosphate buffer solution containing 150 mM NaCl and 100 mM glucose. Potential application of this approach to implantable enzymatic biofuel cells is demonstrated by production of glucose oxidation currents, under pseudo-physiological conditions, using mediating films with lower redox potentials.