Hydrogen peroxide biosensor based on sol-gel-derived glasses doped with Eastman AQ polymer

A hydrogen peroxide biosensor based on sol-gel-derived glasses doped with poly(ester sulfonic acid) Eastman AQ 55D was constructed. Thionine (TH), as a mediator, was incorporated in this matrix by electrostatic force between TH+ and the negatively charged sulfonic acid group in Eastman AQ polymer. Performance and characteristics of the sensor were evaluated with respect to response time, sensitivity and storage stability. The enzyme electrode has a sensitivity of 11.36 muA mM(-1) with a detection limit of 5.0 x 10(-7) M H2O2, and the sensor achieved 95% of the steady state current within 20 s. (C) 2001 Elsevier Science B.V. All rights reserved.

A facile approach to immobilize protein for biosensor: self-assembled supported bilayer lipid membranes on glassy carbon electrode

A kind of solid substrate, glassy carbon (GC) electrode. was selected to support self-assembled lipid layer membranes. On the surface of GC electrode. we made layers of dimyristoylphosphatidylcholine (DMPG, a kind of lipid). From electrochemical impedance experiments. we demonstrated that the lipid layers on the GC electrode were bilayer lipid membranes. We immobilized horseradish peroxidase (HRP) into the supported bilayer lipid membranes (s-BLM) to develop a kind of mediator-free biosensor for H2O2. The biosensor exhibited fine electrochemical response, stability and reproducibility due to the presence of the s-BLM. As a model of biological membrane, s-BLM could supply a biological environment for enzyme and maintain its activity. So s-BLM is an ideal choice to immobilize enzyme for constructing the mediator-free biosensor based on GC electrode. (C) 2001 Elsevier Science B.V. All rights reserved.

Cobalt(II)hexacyanoferrate film modified glassy carbon electrode for construction of a glucose biosensor

An amperometric glucose biosensor was constructed based on a glassy carbon electrode modified with a Cobalt(II)hexacyanoferrate film which catalyzes electroreduction of hydrogen peroxide. Gelatin was used as immobilization matrix. Interference could be effectively eliminated by the combination of low detection potential with a Nafion coating. A low applied potential can avoid oxidation of interferences such as ascorbic acid, uric acid, p-acetyl-aminophenol, etc.. Nafion coating prevents interferences from access to the electrode surface by electrostatic repulsion. A wide linear range of detection was obtained. Analytical performance parameters are given and kinetic analysis discussed.

Sol-gel biosensor

yA review with 44 references is presented on the development of sol-gel-based biosensor. The main discussions are devoted to the process, advantages and properties of sol-gel immobilization method, sol-gel optical biosensor and amperometric biosensor, also the trend in this field is forecasted.

Sol-gel thin-film immobilized soybean peroxidase biosensor for the amperometric determination of hydrogen peroxide in acid medium

An acid-stable soybean-peroxidase biosensor was devel oped by immobilizing the enzyme in a sol-gel thin film. Methylene blue was used as a mediator because of its high electron-transfer efficiency. The sol-gel thin film and enzyme membrane were characterized by FT-IR, and the effects of pH, operating potential, and temperature were explored for optimum analytical performance by using the amperometric method. The H2O2 sensor exhibited a fast response (5 s), high sensitivity (27.5 mu A/mM), as well as good thermostability and long-term stability. In addition, the performance of the biosensor was investigated using flow-injection analysis (FIA).

Self-gelatinizable graft copolymer of poly(vinyl alcohol) with 4-vinylpyridine as an immobilization matrix for the construction of a tyrosinase-based amperometric biosensor

A tyrosinase-based amperometric biosensor using a self-gelatinizable graft copolymer of poly(vinyl alcohol) with 4-vinylpyridine (PVA-g-PVP) as an immobilization matrix was constructed. The 4-vinylpyridine component of PVA-g-PVP enhances the adherence to a glassy carbon electrode surface. The content of 4-vinylpyridine in this immobilization matrix plays a key role in retaining the activity of tyrosinase. A simple, milder method was adopted by simply syringing the copolymer-tyrosinase aqueous solution on to the electrode surface and allowing water to evaporate at 4 degrees C in a refrigerator. Several parameters, including copolymer composition; pH, applied potential and enzyme membrane composition, ware optimized. The enzyme membrane composition can be varied to obtain higher sensitivity or a wider linear detection range. The biosensor was used for the determination of phenol, p-cresol and catechol. The biosensor exhibited excellent reproducibility, stability and sensitive response and can be used in flow injection analysis. The biosensor showed an extended linear range in hydrophilic organic solvents and it can be used in monitoring organic reaction processes. The analytical performance demonstrated this immobilization matrix is suitable for the immobilization of tyrosinase.

Functionalized inorganic-organic composite material derivated by sol-gel for construction of mediated amperometric hydrogen peroxide biosensor

A novel functionalized inorganic-organic hybrid material with cation exchange property was prepared by sol-gel method. The H2O2 biosensor was fabricated by simply dipping the horseradish peroxidase-containing functionalized membrane modified electrode into Meldola's blue (MDB) solution. MDB was adsorbed and firmly immobilized within the membrane. The electrochemical behavior of MDB incorporated in the membrane was more reversible compared with that of the solution species and suitable as mediator for the horseradish peroxidase. The response time was less than 25 s. Linear range is up to 0.6 mM (COH. coeff. 0.9998) with detection Limit of 9 x 10(-7) M. High sensitivity of 75 nA mu M cm(-2) was obtained due to high MDB-loading. The biosensor exhibited a good stability. (C) 1999 Elsevier Science B.V. All rights reserved.

Self-gelatinizable copolymer immobilized glucose biosensor based on Prussian Blue modified graphite electrode

A novel poly(vinyl alcohol) grafting 4-vinylpyridine self-gelatinizable copolymer was adapted to immobilize glucose oxidase. The reduction of hydrogen peroxide (H2O2) was detected at a Prussian Blue (PB) modified graphite electrode. A stable and sensitive glucose amperometric biosensor is described. The copolymer is a good biocompatible polymer in which the glucose oxidase retains high activity. Moreover, the copolymer can adhere firmly to the inorganic PB membrane. The sensor showed an apparent Michaelis-Menten constant of 18 +/- 0.2 mM and a maximum current density of 1.14 mu A cm(-2) mM(-1). The linear range is from 5 mu M to 4.5 mM glucose and the detection limit is 0.5. mu M glucose. The catalytic efficiency of PB for the reduction of H2O2 is higher than that for the oxidation of H2O2. Glucose concentrations in serum samples from healthy persons and diabetic patients were determined using the sensor. The results compared well with those provided by the hospital using a spectroscopy method.

Amperometric glucose biosensor based on sol-gel organic-inorganic hybrid material

A new type of sol-gel organic-inorganic hybrid material was developed and used for the production of biosensors. This material is composed of silica sol and a grafting copolymer of poly(vinyl alcohol) with 4-vinylpyridine. It prevents the cracking of conventional sol-gel-derived glasses and eliminates the swelling of the hydrogel. The optimum composition of the hybrid material was first examined, and then glucose oxidase was immobilized in this matrix to demonstrate its application. The characteristics of the biosensor were studied by cyclic voltammetry and chronoamperometry. The biosensor exhibited a series of good properties: high sensitivity (600 nA mmol(-1)L(-1)), short response time (11 s) and remarkable long-term stability in storage (at least 5 months). In addition, the characteristics of the second-generation biosensor with the use of tetrathiafulvalene as a mediator mere discussed.

Amperometric biosensor for tyrosinase inhibitors in a pure organic phase

The determination of benzoic acid, thiourea and 2-mercaptoethanol in three pure organic solvents, viz., chloroform, chlorobenzene and 1,2-dichlorobenzene, by using an amperometric cryohydrogel tyrosinase biosensor is described. Measurements were carried out with phenol as the enzyme substrate. Kinetic parameters (K-i and I-50) were determined in the three solvents for various inhibitors. The sensor showed the most sensitive measurements to these inhibitors in pure chloroform. The solvent-induced deviation of the biosensor to thiourea was evaluated by means of Hill coefficients. The smallest deviation as observed in 1,2-dichlorobenzene, owing to the high hydrophobicity of this solvent. The nature of the inhibition process and its reversibility mere also examined.

Cryoimmobilized enzyme for biosensor construction

A new immobilization material and an immobilization method for a glucose sensor with HEFc (hydroxyethylferrocene) as mediator is described. In the course of three months, the enzyme electrode shows almost no deterioration in its response characteristics. The response time is less than 30 s. The electrode has a wide linear range up to 10 mmol l(-1) with good repeatability. The kinetic parameters have also been calculated.

Cyro-hydrogel for the construction of a tyrosinase-based biosensor

A new immobilization method for construction of a tyrosinase based biosensor is described. A simple physical freezing technique was adopted for preparation. The immobilized enzyme yields specific activities that are more than 22% of the soluble enzyme. The enzyme electrode can be stored in dry state for more than three months without any loss of activity. The biosensor was applied to the determination of several phenols and o-diphenols. The lowest detect limit is 0.02 mu mol/1 and the linear range was 1.0 X 10(-7)-1.0 X 10(-4) mol/1 for catechol. The kinetic parameters have also been calculated.

CONSTRUCTION OF A TYROSINASE-BASED BIOSENSOR IN PURE ORGANIC-PHASE

A novel immobilization method for construction of a tyrosinase-based biosensor applied in pure organic phase is described. This method gives the enzyme a hydrated shell which allows the enzyme to maintain its biocatalytic activity in a pure organic solvent The enzyme electrode was used to determine several phenols and o-diphenols in pure chloroform and chlorobenzene. The biosensor can be stored in dry state for more than 3 months without any loss of the activity. The kinetic parameters have also been calculated and are presented herein.

A蛋白定向固定抗体用于椭偏光学生物传感器免疫检测

椭偏光学生物传感器是在椭偏光学显微成像技术的基础上发展的一项生物传感技术.它能够直接观测固体表面上的生物分子面密度,毋需任何标记辅助,适合发展成为一种无标记免疫检测技术.研究了在硅片表面上通过A蛋白定向固定抗体分子用于椭偏光学生物传感器免疫检测的可能性.实验结果表明,通过A蛋白固定抗体得到的抗体膜层的均一性和固定量的重复性能够保证椭偏光学生物传感器免疫检测结果的质量.通过A蛋白定向固定的抗体的抗原结合位点趋向一致,显著提高了抗体与抗原结合的能力.此外,通过蛋白A固定的免疫球蛋白G分子能够结合更多的多克隆抗体分子说明通过A蛋白固定的蛋白质分子能够较好地保持其空间构象.

椭偏光学生物传感器及生物医学应用

椭偏光学生物传感器是识别和检测蛋白质的一种新型的高通量、快速生物分子分析技术.它可以实现无标记多元生物分子自动化检测、静态或动态测量及定性和定量测量等,已应用于生物医学与临床检测等方面,如肿瘤标志蛋白检测、乙肝五项同时检测、蛋白质竞争吸附以及多元蛋白质相互作用动态测量等,显示出了广阔的应用前景.