One-step electropolymeric co-immobilization of glucose oxidase and heparin for amperometric biosensing of glucose

Electropolymerization was used for the co-deposition of glucose oxidase and heparin onto metal electrode transducers. Such electropolymeric co-entrapment within a non-conducting poly(1,2-phenylenediamine) (PPD) film imparts both biocatalytic and anticoagulation activities onto the transducer, and greatly improves the performance of the sensor after exposure to whole blood. Essentially identical glucose signals are observed before and after exposure to blood samples. Scanning electron micrographs after such exposure reveal no platelet deposition or formation of a fibrin "clot". The effect of the heparin co-immobilization on the glucose response is examined. Improved biocompatibility is reported also in connection with a needle-type carbon paste biosensor configuration. The simultaneous localization of the enzyme and heparin offers great promise for simplifying the preparation of enzyme electrodes and designing biocompatible implantable glucose biosensors.     

A glucose electrode based on carbon paste chemically modified with a ferrocene-containing siloxane polymer and glucose oxidase,coated with a poly(ester-sulfonic acid) cation-exchanger

A carbon-paste chemically modified with glucose oxidase and a ferrocene-containing siloxane polymer was further modified by coating the electrode surface with a poly(ester-sulfonic acid) cation-exchanger, Eastman AQ-29D. The polymer is obtained as a homogeneous aqueous dispersion at pH 5–6; when dried, the polymer coating is not water-soluble. The coating was shown not to be detrimental to the enzyme activity but to prevent electrochemically active anionic interferents such as ascorbate and urate from reaching the electrode surface. The polymer coating also prevented glucose oxidase from leaking out of the carbon paste into the contacting solution and protected the electrode surface from fouling agents present in urine and bovine serum albumin. Uncoated electrodes lost some 10-2-15% of their original response to glucose after storage in buffer for three weeks whereas the response of the coated electrodes remained constant. Calibration curves for glucose were strictly linear up to about 5 mM for uncoated and up to 20 mM for coated electrodes. The response current to glucose was not decreased after coating.     

Multipurpose electrode with different enzyme systems bound to collagen films

Selective, multipurpose electrodes have been developed from the previously described glucose electrode based on amperometric detection of hydrogen peroxide. Several single or multi-enzyme systems, including galactose oxidase, cholesterol oxidase, glucoamylase with glucose oxidase, and invertase with glucose oxidase, can be covalently bound to collagen membranes and attached to a platinum anode for monitoring the hydrogen peroxide generated. The probes allow fast and sensitive measurements of galactose, free cholesterol and maltose. Analogous electrodes are convenient for the assay of sucrose and lactose, with lower sensitivity. For disaccharide measurements, a comparative study of membranes produced by random co-immobilization, stacking of membranes and asymmetric coupling is reported. Asymmetric coupling improved the electrode performances in every case. One enzyme membrane is readily replaced by another in the electrode construction, and the sensors can be used for hundreds of assays.     

Bienzyne Electrodes for ATP,NAD+, Starch and Disaccharides Based on a Glucose Sensor

Abstract

A glucose measuring device based on the oxidation of glucose by glucose oxidase and an amperometric kinetic detection was developed. The characteristics obtained with this instrument are comparable with the present glucose instruments but the stability of the enzyme membrane is better and the measuring frequency is higher. In order to expand the applicability of this device to other substrates there was developed a family of bioenzyme electrodes. Enzymes producing glucose as enzymes consuming glucose in addition to glucose oxidase were used.

For determination of peroxidase substrates besides a peroxidase-catalase electrode a three-enzyme system consisting of glucose oxidase, peroxidase and catalase was used.     

Application of Amperometric Enzyme Biosensors for Wine and Must Analysis

The work presents application of amperometric biosensors based on platinum printed electrodes and immobilized enzymes alcohol oxidase, glucose oxidase and lactate oxidase for wine analysis. Created devices demonstrate wide dynamic range of work, good stability and high selectivity to the substrate, and are successfully applied for analysis of such complex mixtures as wine and must. Good correlation of the results of analysis of different wines and must obtained by amperometric biosensors and chromatography method is shown. Created biosensors can be used as a basis of commercial device for express analysis of ethanol, glucose and lactate in wine and must during its fermentation.     

A Micro Planar Ampehometric Glucose Sensor Using an Isfet as a Reference Electrode

Abstract

A very small glucose sensor has been realized, which consists of a gold working electrode with a glucose oxidase immobilized membrane on it, and a gold counter electrode, all made on a sapphire substrate. By using the pH sensitive ISFET as a reference electrode, the potential for a solution, whose pH is constant, can be measured and irreversible metal electrodes, such as gold or platinum, can be used as working electrode and counter electrode. The sensor is very suitable for miniaturizing and mass production, because the Integrated Circuit (IC) fabrication process can be applied. The glucose oxidase immobilized membrane was also deposited by a lift off method, one of the IC processes. A glucose concentration, from 1 to 100 mg/dl, was measured with good linear current output.     

Some studies of electrodes made from single crystals of TTF /sd TCNQ

Electrodes made from single crystals of tetrathiafulvalenium tetracyanoquinodimethanide (TTF. TCNQ) have been used to study the electrochemistry of the conducting organic salt and to investigate the mechanism of the electrochemical oxidation of glucose oxidase at conducting salt electrodes.The single crystal electrodes exhibit much lower non-Faradaic currents than the corresponding polycrystalline electrodes prepared as sublimed films or as pressed pellets. This leads to much lower background current levels and hence more clearly defined electrochemistry for solution species. Studies of the ac impedance behaviour and the electrochemistry of outer sphere redox species indicate that TTF·TCNQ electrodes behave as conventional metallic electrodes within their stable potential range.Results for the electrochemistry of glucose oxidase at the single crystal electrodes are inconsistent with a simple homogeneous mediation mechanism or with simple heterogeneous redox catalysis. Similarities with results obtained for TTF modified glucose oxidase suggest that the enzyme may undergo direct electrochemistry after modification by hydrophobic interaction with TTF molecules derived from the conducting salt electrode.     

Biotinylated alginate immobilization matrix in the construction of an amperometric biosensor: application for the determination of glucose

The use of biotinylated alginate as an immobilization matrix of enzymes on the surface of the amperometric transducer is described herein. The model used is that of the well-established glucose detection. Several types of immobilization protocols were tested. In the exception of one protocol, biotin labeled glucose oxidase was shown to first require conjugation with avidin, before its immobilization onto a biotin-alginate gel matrix. The response of the biosensors to incremental additions of glucose, was measured by potentiostating the modified electrodes at 0.6 V/SCE. The permeability of the modified electrodes was thereafter measured by using rotating disk electrode (RDE) voltammetry with ferrocenemonocarboxylic acid as the electroactive probe.     

Parameters important in fabricating enzyme electrodes using self-assembled monolayers of alkanethiols.

The fabrication of enzyme electrodes using self-assembled monolayers (SAMs) has attracted considerable interest because of the spatial control over the enzyme immobilization. A model system of glucose oxidase covalently bound to a gold electrode modified with a SAM of 3-mercaptopropionic acid was investigated with regard to the effect of fabrication variables such as the surface topography of the underlying gold electrode, the conditions during covalent attachment of the enzyme and the buffer used. The resultant monolayer enzyme electrodes have excellent sensitivity and dynamic range which can easily be adjusted by controlling the amount of enzyme immobilized. The major drawback of such electrodes is the response which is limited by the kinetics of the enzyme rather than mass transport of substrates. Approaches to bringing such enzyme electrodes into the mass transport limiting regime by exploiting direct electron transfer between the enzyme and the electrode are outlined.     

Activity enhancement of a screen-printed carbon electrode by modification with gold nanoparticles for glucose determination

We have successfully developed a highly sensitive electrochemical sensor strip for a home blood-sugar monitoring device by a single-step straightforward procedure. The strip consists of a pair of screen-printed carbon electrodes, which work as counter and working electrodes in the chronoamperometric mode. To remedy the poor electrochemical activity of the printed carbon electrode, a small amount of gold nanoparticles was immobilized on the electrode. In the presence of glucose oxidase, the electrode modified with 2-nm particles showed about a five times higher sensitivity for glucose oxidation than the bare printed carbon electrode, and there was a significant dependence of the current on the particle diameter. Based on these observations, we have elucidated the glucose oxidation mechanism, which is comprised of two key factors, i.e. (1) electron transfer between the gold particles, and (2) electronic coupling between the gold particles and glucose oxidase.     

Mesoporous carbon amperometric glucose sensors using inexpensive,commercial methacrylate-based binders

Two ordered, soft-templated mesoporous carbon powders with cubic and hexagonal framework structure and four different commercial, low cost methacrylate-based polymer binders with widely varying physical properties are investigated as screen printed electrodes for glucose sensors using glucose oxidase and ferricyanide as the mediator. Both the chemistry and concentration of the binder in the electrode formulation can significantly impact the performance. Poly(hydroxybutyl methacrylate) as the binder provides hydrophilicity to enable transport of species in the aqueous phase to the carbon surface, but yet is sufficiently hydrophobic to provide mechanical robustness to the sensor. The current from the mesoporous carbon electrodes can be more than an order of magnitude greater than for a commercial printed carbon electrode (Zensor) with improved sensitivity for model glucose solutions. Even when applying these sensors to rabbit whole blood, the performance of these glucose sensors compares favorably to a standard commercial glucose meter with the lower detection limit of the mesoporous electrode being approximately 20 mg dL⁻¹ despite the lack of a separation membrane to prevent non-specific events; these results suggest that the small pore sizes and high surface areas associated with ordered mesoporous carbons may effectively decrease some non-specific inferences for electrochemical sensing.     

A glucose biosensor based on electrodeposited biocomposites of gold nanoparticles and glucose oxidase enzyme.

Electrodeposition was used for the codeposition of glucose oxidase enzyme and a gold nanoparticle-silicate network onto an indium tin oxide (ITO) glass electrode. This co-entrapment of glucose oxidase enzyme in a gold nanoparticle-silicate network imparts biocatalytic activity to the film. The gold nanoparticles in the network catalyse the oxidation and reduction of H2O2, the by-product of the enzymatic reaction. The low operating potential of the sensor eliminates the interference from common interferents, such as acetaminophen, ascorbic acid, dopamine, etc.     

Fuel-Cell Type Ceramic-Carbon Oxygen Sensors

Several classes of sol-gel derived, fuel-cell-type gas sensors are described. The electrochemical sensors are comprised of a hydrophobically modified silicate network and a dispersion of carbon powder and inert metal (palladium or platinum in the zero valent state) or organometallic (e.g., cobalt porphyrin) catalyst modifier.The carbon powder provides conductivity, the Ormosil network assures high porosity, which is pertinent for gas permeation through the back of the electrodes, and the hydrophobic functional group assures that only a thin layer at the outermost section of the electrode is wetted by the electrolyte, thus providing fast dynamic response.     

Plasma-Polymerized Thin Films for Enzyme Immobilization in Biosensors

Abstract

Polymer films deposited on thin film noble metal electrodes on silicon chips, utilizing plasma polymerization are shown to be suited for immobilization of enzymes. Glucose oxidase is covalently coupled via amino- or carboxyl-groups of polymer films made by plasma polymerization of 2-amino-benzotrifluoride, acrylic or methacrylic acid. The concentration of these active surface groups increases by after-treatment in an ammonia- or oxygen-plasma. A biosensor consisting of a thin film metal electrode, plasma polymer film and immobilized glucose oxidase shows an amperometric response to glucose with a fast response time.     

A rapid and easy procedure of biosensor fabrication by micro-encapsulation of enzyme in hydrophilic synthetic latex films. Application to the amperometric determination of glucose

Novel enzyme electrodes based on synthetic hydrophilic latex matrices are described for the detection of glucose. Glucose oxidase was immobilised through micro-encapsulation, by the simple adsorption of enzyme–latex suspensions on the surface of a platinum electrode. Two latex films functionalised by a hydroxy or a gluconamide group were used. The response of these biosensors to glucose additions was measured by potentiostating the modified electrodes at 0.6 V/SCE in order to oxidise the hydrogen peroxide generated by the enzymatic oxidation of glucose in the presence of dioxygen. The response of such electrodes was evaluated as a function of film thickness and temperature. The sensitivity for a two-layer latex-based biosensor was found to be 38.78 mA M⁻¹ cm⁻² with a response time of 3–5 s. Moreover, a marked improvement of the thermal stability of the biosensor was observed. Only at temperatures higher than 65°C the enzyme started to be denatured and being inactive.     

Achieving Direct Electrical Connection to Glucose Oxidase Using Aligned Single Walled Carbon Nanotube Arrays

Direct electron transfer between an electrode and the redox active centre of glucose oxidase, flavin adenine dinucleotide (FAD), is probed using carbon nanotube modified gold electrodes. Gold electrodes are first modified with a self‐assembled monolayer of cysteamine and then shortened single walled carbon nanotubes (SWNT) are aligned normal to the electrode surface by self‐assembly. The electrochemistry of these aligned nanotube electrode arrays is initially investigated using potassium ferricyanide which showed SWNT act as nanoelectrodes with the ends of the tubes more electrochemically active than the walls. Subsequently the nanotubes are plugged into the enzymes in one of two ways. In the first method, native glucose oxidase is covalently attached to the ends of the aligned tubes which allowed close approach to FAD and direct electron transfer to be observed with a rate constant of 0.3 s^?1. In the second strategy, FAD was attached to the ends of the tubes and the enzyme reconstituted around the surface immobilized FAD. This latter approach allowed more efficient electron transfer to the FAD with a rate constant of 9 s^?1.     

Poly(3,4‐ethylenedioxythiophene)‐based copolymers for biosensor applications

The synthesis of 3,4‐ethylenedioxythiophene (EDOT) derivatives bearing functional groups is described. Their electrochemical characteristics were investigated with cyclic voltammetry and ultraviolet–visible spectroscopy. Various copolymers of EDOT and modified EDOT containing hydroxyl groups were electrochemically prepared. The ability to bind proteins to the surface of these copolymers was investigated through the covalent coupling of glucose oxidase. The obtained materials were used as working electrodes and were shown to be able to amperometrically detect glucose under aerobic and anaerobic conditions. Possible applications of these materials as biosensors are discussed. © 2002 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 40: 738–747, 2002; DOI 10.1002/pola.10159     

Amperometric enzyme electrodes of glucose and lactate based on poly(diallyldimethylammonium)-alginate-metal ion-enzyme biocomposites

Sodium alginate (AlgNa) and poly(diallyldimethylammonium chloride) (PDDA) were mixed to obtain an interpenetrating polymer composite via electrostatic interaction and then cast on an Au electrode surface, followed by incorporation of metal ions (e.g. Fe³⁺ or Ca²⁺, to form AlgFe or AlgCa hydrogel) and glucose oxidase (GOx) (or lactate oxidase (LOx)), to prepare amperometric enzyme electrodes. The interactions of PDDA, Alg, and Fe³⁺ are studied by visual inspection as well as microscopic and electrochemical methods. Under optimized conditions, the PDDA-AlgFe-enzyme/Au and PDDA-AlgCa-enzyme/Au electrodes can give good analytical performance (e.g. nM-scale limit of detection of glucose or lactate, and sensitivities > 50 μA cm⁻² mM⁻¹) in the first-generation biosensing mode, which are better than the reported analogs using typical polysaccharide biopolymers as enzyme-immobilization matrices. The enzyme electrodes also worked well in the second-generation biosensing mode in the coexistence of p-benzoquione or ferrocene monocarboxylic acid artificial mediator. Biofuel cells (BFCs) with the enzyme electrodes as the bioanodes and glucose (or lactate) as the biofuel were also fabricated with satisfactory results. The proposed protocols for preparation of high performance Alg-based biocomposites may find wide applications in bioanalysis.     

蜘蛛丝素和聚乙烯醇固定葡萄糖氧化酶 制备葡萄糖传感器

用蜘蛛丝素和聚乙烯醇的混合材料把葡萄糖氧化酶固定在氧电极表面,制成葡萄糖氧化酶电极。传感器对葡萄糖有灵敏的响应,平均响应时间为20s,电位变化值与葡萄糖浓度在3.0×10     

The Incorporation of Titania into Modified Silicates for Solar Photodegradation of Aqueous Species

A new class of sol-gel-derived photocatalytic materials has been synthesized and used in solar-assisted photodegradation studies. The materials are comprised of a homogeneous dispersion of commercial TiO₂ powder into silica and organically modified silicate (Ormosil) hosts. The efficiency of the photocatalytic properties of these TiO₂-containing materials was determined by their relative performance in the solar photodecomposition of aqueous rhodamine B. The improved adsorption properties of the modified materials compared to commercial TiO₂ increase the photodecomposition rate and the buoyancy properties, although excess hydrophobicity decreases the wetted section of the catalyst and its photocatalytic performance. These materials can be used as floatable catalysts for solar-assisted water purification.