Kinetic glucose determination with glucose dehydrogenase

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Kinetic glucose determination with glucose dehydrogenase

     

Continuous glucose monitoring in interstitial fluid using glucose oxidase-based sensor compared to established blood glucose measurement in rats

Glucose monitoring is of importance for success of complex therapeutic interventions in diabetic patients. Its impact on treatment and glycemic control is demonstrated in large clinical trials. Up to eight blood glucose measurements per day are recommended. Notwithstanding, a substantial number of diabetic patients cannot or will not monitor their blood glucose appropriately. Considerable progress in control of disturbed metabolism in diabetic patients can be expected by continuous glucose monitoring. The aim of the study was to evaluate the performance of a new amperometric glucose oxidase-based glucose sensor in vitro and in vivo after subcutaneous implantation into rats.For in vitro testing current output of sensors was measured by exposure to increasing and decreasing glucose concentrations up to 472 mg dL⁻¹ over a time period of 7 days. After subcutaneous implantation of sensors into interscapular region of male rats glucose in interstitial fluid was evaluated and compared to glucose in arterial blood up to 7 days. Hyper- and hypoglycaemia were induced by intravenous application of glucose and insulin, respectively. Current of each implanted sensor was converted into glucose concentration using the first blood glucose measurement only.A change of current with glucose of 0.35 nA mg⁻¹ dL⁻¹ indicates high sensitivity of the sensor in vitro. The response time (90% of steady state) was calculated by approximately 60 s. Test strips for blood glucose measurement as reference for sensor readings was found as an appropriate and rapidly available method in rats by comparison with established hexokinase method in an automated lab analyzer with limits of agreement of +32.8 and −25.7 mg dL⁻¹ in Bland-Altman analysis. In normo- and hypoglycaemic range sensor readings in interstitial fluid correlated well with blood glucose measurements whereas hyperglycaemia was not reflected by the sensor completely when blood glucose was changing rapidly.The data given characterize a sensor with high sensitivity, long term stability and short response time. A single calibration of the sensor is required only in measurement periods up to 7 days. The findings demonstrate that the sensor is a highly promising candidate for assessment in humans.     

Electrochemical non-enzymatic glucose sensors

The electrochemical determination of glucose concentration without using enzyme is one of the dreams that many researchers have been trying to make come true. As new materials have been reported and more knowledge on detailed mechanism of glucose oxidation has been unveiled, the non-enzymatic glucose sensor keeps coming closer to practical applications. Recent reports strongly imply that this progress will be accelerated in ‘nanoera’. This article reviews the history of unraveling the mechanism of direct electrochemical oxidation of glucose and making attempts to develop successful electrochemical glucose sensors. The electrochemical oxidation of glucose molecules involves complex processes of adsorption, electron transfer, and subsequent chemical rearrangement, which are combined with the surface reactions on the metal surfaces. The information about the direct oxidation of glucose on solid-state surfaces as well as new electrode materials will lead us to possible breakthroughs in designing the enzymeless glucose sensing devices that realize innovative and powerful detection. An example of those is to introduce nanoporous platinum as an electrode, on which glucose is oxidized electrochemically with remarkable sensitivity and selectivity. Better model of such glucose sensors is sought by summarizing and revisiting the previous reports on the electrochemistry of glucose itself and new electrode materials.     

A fluorescence lifetime-based fibre-optic glucose sensor using glucose/galactose-binding protein

Alternative, non-electrochemistry-based technologies for continuous glucose monitoring are needed for eventual use in diabetes mellitus. As part of a programme investigating fluorescent glucose sensors, we have developed fibre-optic biosensors using glucose/galactose binding protein (GBP) labelled with the environmentally sensitive fluorophore, Badan. GBP-Badan was attached via an oligohistidine-tag to the surface of Ni-nitrilotriacetic acid (NTA)-functionalized agarose or polystyrene beads. Fluorescence lifetime increased in response to glucose, observed by fluorescence lifetime imaging microscopy of the GBP-Badan-beads. Either GBP-Badan agarose or polystyrene beads were loaded into a porous chamber at the end of a multimode optical fibre. Fluorescence lifetime responses were recorded using pulsed laser excitation, high speed photodiode detection and time-correlated single-photon counting. The maximal response was at 100 mM glucose with an apparent K(d) of 13 mM (agarose) and 20 mM (polystyrene), and good working-day stability was demonstrated. We conclude that fluorescence lifetime fibre-optic glucose sensors based on GBP-Badan are suitable for development as clinical glucose monitors.     

Frequency response of the glucose sensor based on immobilized glucose oxidase membrane

Frequency response of the glucose sensor based on the immobilized glucose oxidase membrane was investigated experimentally by giving the sinusoidal change of glucose concentration to the glucose sensor and observing its output signal. Observed values of gains and phase lags of the frequency response of the glucose sensor followed the frequency response model of the first-order with dead time; The time constant and also the dead time were estimated and found to decrease as the amount of enzyme immobilized in the membrane increased and the thickness of the membrane decreased.

     

Resorufin as an electron acceptor in glucose oxidase-catalyzed oxidation of glucose

Resorufin (1) has been found to act as an electron acceptor in glucose oxidase (GOD)-catalyzed oxidation of glucose. When a 1: 1: 1 mixture of solutions of 1 (5.0 microM), glucose, and GOD (4.0 mg/ml) in phosphate buffer (pH 7.4, 0.1 M) was incubated at 36 degrees C under aerobic conditions and the reaction was followed by a measurement of changes in fluorescence intensity due to 1, only two types of fluorometric traces were observed: (1) when a glucose solution of less than 0.7 mM was subjected to the enzymatic reaction, no consumption of 1 was observed; (2) the reaction with glucose at more than 1.0 mM always consumed 1, affording a regression fluorometric curve, and yet the obtained fluorometric traces could be almost superimposed on one another with no dependence on the glucose concentration. The reasons for the observed phenomena are discussed.     

Improved biosensor for glucose based on glucose oxidase-immobilized silk fibroin membrane

Based on glucose oxidase-immobilized silk fibroin membrane and oxygen electrode, the authors have developed an amperometric glucose sensor in flow-injection analysis. After the sensor was improved by the configuration of oxygen electrode and a temperature control system was added to the electrode body, its sensitivity, analytical precision, and stability were enhanced greatly. The authors first introduced a tailing inhibitor-ion pair reagent into a buffer system in the biosensor so as to eliminate all interference from hemacyte, macromolecules, and small mol wt charged species besides electroactive specie ascorbate in complex matrices. A considerably serious tailing of the biosamples, such as whole blood, plasma, serum, or urine on the sensor, based on enzyme electrode, entirely disappeared, their response times were shortened, and base lines became more smooth and stable. The glucose sensor has a broad range of linear response for glucose (up to 25.0 mmol/L) and a good correlation (γ = 0.999) under conditions of control temperature 32.0°C and 1.6 mL/min 0.02 mol/L phosphate buffer containing 0.5% tailing inhibitor (v/v). Recoveries of glucose in these biosamples are within the range of 93.71–105.88%, and its repeatabilities for determining glucose, repeated 100 times, human blood dilution 125 times, and serum 128 times, are 1.81,2.48, and 2.91% (RSD), respectively. The correlation analysis for 200 serum samples showed that the correlation (γ) is 0.9934 between the glucose sensor and Worthington method for determining serum glucose used conventionally in a hospital laboratory. Moreover, the enzyme membrane used in the biosensor can be stored for a long time (over 2 yr) and measured repeatedly over 1000 times for biosamples. The glucose sensor is capable of detecting over 60 biosamples/hr.     

Direct coupling of glucose oxidase to platinum and possible use forin vivo glucose determination

Glucose oxidase was attached to platinum-platinum oxide screens via alkylamine silaneglutaraldehyde coupling. The amount of immobilized enzyme was equivalent to 0.0031 µg of soluble glucose oxidase per cm² of screen surface. The platinum-silane-glutaraldehydeenzyme screens were tested potentiometrically in buffered glucose solutions, with respect to a Ag/AgCl reference electrode. The results were expressed as the difference in potential for the enzyme screens placed in buffer containing glucose and placed in plain buffer. This difference in potential was related linearily to the logarithm of the glucose concentration over the range 5–150 mg glucose/100 ml. The source of the potential may be due to the decomposition of hydrogen peroxide produced by the glucose oxidase catalyzed oxidation of glucose. The approach is being studied for possible development of an implantable sensor for continuousin vivo monitoring of glucose levels.     

Biosensors for determination of glucose with glucose oxidase immobilized on an eggshell membrane

A glucose biosensor using an enzyme-immobilized eggshell membrane and oxygen electrode for glucose determination has been fabricated. Glucose oxidase was covalently immobilized on an eggshell membrane with glutaraldehyde as a cross-linking agent. The glucose biosensor was fabricated by positioning the enzyme-immobilized eggshell membrane on the surface of a dissolved oxygen sensor. The detection scheme was based on the depletion of dissolved oxygen content upon exposure to glucose solution and the decrease in the oxygen level was monitored and related to the glucose concentration. The effect of glutaraldehyde concentration, pH, phosphate buffer concentration and temperature on the response of the glucose biosensor has been studied in detail. Common matrix interferents such as ethanol, d-fructose, citric acid, sodium benzoate, sucrose and l-ascorbic acid did not give significant interference. The resulting sensor exhibited a fast response (100 s), high sensitivity (8.3409 mg L⁻¹ oxygen depletion/mmol L⁻¹ glucose) and good storage stability (85.2% of its initial sensitivity after 4 months). The linear response is 1.0×10⁻⁵ to 1.3×10⁻³ mol L⁻¹ glucose. The glucose content in real samples such as commercial glucose injection preparations and wines was determined, and the results were comparable to the values obtained from a commercial glucose assay kit based on a spectrophotometric method.     

表面可更新的石墨陶瓷葡萄糖生物传感器研究

A surface-renewable glucose biosensor is reported. The glucose biosensor is developed using glucose oxidase (GOD) encapsulated in organically modified solgel glass (ORMOSIL) network in the composite matetial. The organic group in the ORMOSIL network controls the hydrophobicity of the electrode surface and thus limits the wettability of the electrode surface. The graphite powder provides the conductivity for the electrode.Ferrocenecarboxylic acid in phosphate buffer solution (pH 7.0) transfers electron between enzyme and electrode. Cyclic volammetry and amperometric measurements have been used to exmine the electrochemical behavior of glucose biosensor as shown in Fig. 1 and Fig.2. The electrode gives a linear response range of 1 -20mM glucose with a sensitivity of 3.26 μA· mM-1. The electrode can be renewed easily in reproducible manner by a simple polishing step.     

An optical glucose biosensor based on glucose oxidase immobilized on a swim bladder membrane

An optical glucose biosensor using a swim bladder membrane as an enzyme immobilization platform and an oxygen-sensitive membrane as an optical oxygen transducer has been developed. During the enzymatic reaction, glucose is oxidized by glucose oxidase with a concomitant consumption of dissolved oxygen resulting in an increase in the fluorescence intensity of the optical oxygen transducer. The fluorescence intensity is directly related to the glucose concentration. The effects of pH, temperature, buffer concentration, and selectivity have been studied in detail. The immobilized enzyme retained 80% of its initial activity after being kept for more than 10 months at 4°C. The glucose biosensor has been successfully applied to the determination of glucose content in human blood serum and urine samples. Martin M.F. Choi was on sabbatical leave at The University of North Carolina at Chapel Hill from July 2004 to July 2005.     

Sensing nanomaterials of wearable glucose sensors

The metabolic disorder of glucose in human body will cause diseases such as diabetes and hyperglycemia.Hence the determination of glucose content is very important in clinic diagnosing.In recent years,researchers have proposed various non-invasive wearable sensors for rapid and real-time glucose monitoring from human body fluids.Unlike those reviews which discussed performances,detection environments or substrates of the wearable glucose sensor,this review focuses on the sensing nanomaterials since they are the key elements of most wearable glucose sensors.The sensing nanomaterials such as carbon,metals,and conductive polymers are summarized in detail.And also the structural characteristics of different sensing nanomaterials and the corresponding wearable glucose sensors are highlighted.Finally,we prospect the future development requirements of sensing nanomaterials for wearable glucose sensors.This review would give some insights to the further development of wearable glucose sensors and the modern medical treatment.     

Amperometric determination of glucose with a ferrocene-mediated glucose oxidase/polyacrylamide gel electrode

Enzyme electrodes were constructed by immobilization of glucose oxidase and ferrocene into cross-linked polyacrylamide gels. Electrogenerated ferrocinium ion acts as a direct electron mediator between glucose oxidase and a reticulated vitreous carbon (RVC)/graphite support bed. The electrode is easily constructed, gives a current response proportional to glucose concentrations up to 30 mM, and has good chemical stability in water and air.     

Fiber-optic glucose biosensor based on glucose oxidase immobilised in a silica gel matrix

A monolithic silica gel matrix with entrapped glucose oxidase was constructed as a bioactive element in an optical biosensor for glucose determination. Physicochemical and biochemical characterizations of the catalytic matrix were performed, and the intrinsic fluorescence of immobilised glucose oxidase (GOD) was investigated in the UV and visible range by performing steady state and time course measurements. In all cases, the silica gel matrix proved to be a suitable support for optical biosensing owing to its superior optical properties (e.g., high transmittance and reliable fluorescence and GOD absorption spectra after immobilisation). From steady state measurements, calibration curves were obtained as a function of glucose concentration. When time course measurements were performed, the silica gel support displayed a larger linear calibration range and higher sensitivity than other immobilisation systems. In addition, a glucose optical biosensor was developed and characterised using as catalytic element GOD immobilised on a gel disk bound to a bundle of optical fibres.     

Fully reversible fibre-optic glucose biosensor based on the intrinsic fluorescence of glucose oxidase

In a new type of glucose biosensor, the intrinsic green fluorescence of glucose oxidase (GOD) is used to provide the analytical information. It was found that the fluorescence of GOD changes during interaction with glucose. Fluorescence is excited at 450 nm and measured at ? 500 nm, which is a wavelength range that is compatible with glass and plastic fibres. The signal response is fully reversible because oxygen is a second substrate. A major feature of this sensor relies on the fact that the recognition element is identical with the transducer element.Enzyme solutions are entrapped at the fibre end within a semipermeable membrane. The change in fluorescence occurs over a small glucose concentration range (typically 1.5–2 mM), the signal at lower and higher glucose levels being unaffected by changes in glucose concentration. Response times of 2–30 min and regeneration times of 1–10 min are observed. Effects of pH and oxygen concentrations are also investigated. To achieve as extended analytical range (e.g., 2.5–10 mM) and shorter response times, kinetic measurements are suggested.     

Use of an immobilized glucose oxidase cation-exchange resin column in the determination of glucose

A thermal flow system for glucose determination is described, that utilizes a column of glucose oxidase immobilized on a cation-exchange resin (Amberlite CG50). The response is linear for glucose concentrations in the range 0.01-0.4mM. Stability and the factors influencing the response have been examined.     

Nafion coating the ferrocenylalkanethiol and encapsulated glucose oxidase electrode for amperometric glucose detection

This paper describes the fabrication and application of a complex electrode--Nafion film coating ferrocenylalkanethiol (FcC(11)SH) and encapsulated glucose oxidase (GOD) on a gold electrode. FcC(11)SH is employed as a mediator enabling the electron transfer between GOD and the electrode, GOD is encapsulated in polyacrylamide gel to improve the stability of the enzyme, and the Nafion film is coated on the modified electrode to eliminate interferents such as ascorbic acid, uric acid and acetaminophen in amperometric glucose detection. It is noticed that such a complex electrode exhibits excellent catalytic activity for glucose oxidation, and preserves the native structure of GOD and therefore its enzymatic activity. The encapsulated GOD retains more than 80% of its original biocatalytic activity even after 24 days, much longer than that of naked GOD molecules attached directly to the electrode. The oxidation peak current at the modified electrode shows a linear relationship with the glucose concentration in the range from 0.05 to 20 mM with a detection limit of 2.4 μM. In addition, the electrode displays a rapid response and good reproducibility for glucose detection, and has been successfully employed for glucose detection in blood plasma samples.     

无酶葡萄糖电化学传感器的研究进展

随着各种新型材料的层出不穷及其在葡萄糖电化学传感器方面应用的发展,无酶葡萄糖电化学传感器的研制成为葡萄糖电化学传感器的另一个研究热点.本文综述了近年来无酶葡萄糖电化学传感器的研究进展,重点介绍了电流型无酶葡萄糖传感器所使用的各种电极材料,总结了最近五年各种新型结构材料在该类传感器研制方面的应用,并对无酶葡萄糖电化学传感器发展方向和趋势进行了展望.     

Solubility of oxygen in glucose solutions

A knowledge of the solubility of oxygen in glucose-containing solutions is essential for the determination of the kinetics of the glucose oxidase-catalysed glucose oxidation. The enzyme glucose oxidase was used in a new glucose sensor. Combination of data for the dynamic viscosity and density from the literature and data from measurements with a rotating disc electrode (RDE) for hydrogen peroxide and hydroquinone showed that the factor ηD (η = dynamic viscosity; D = diffusion coefficient) remains constant in solutions with a glucose concentration ranging from 0 to 1 M. Assuming that this is also valid for oxygen, the diffusion coefficient of oxygen in glucose solutions was calculated and the solubility of oxygen was determined with RDE measurements. At both 25 and 37°C the relationship between the solubility of oxygen and the glucose concentration is a second-degree polynomial.     

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.