Determination Of Glucose In Beverages Research Articles

Glucose oxidase, horseradish peroxidase and phenothiazine dyes-co-adsorbed carbon felt-based amperometric flow-biosensor for glucose.

To develop an amperometric flow-biosensor for glucose, the stabilizing effect of methylene blue (MB) toward adsorbed glucose oxidase (GOx) on carbon felt (CF) was successfully applied to prepare the GOx-modified CF-based enzyme reactor combined with a horseradish peroxidase (HRP)-modified CF-based H2O2 detector. Upon mixing MB in the GOx-adsorption solution, the O2-dependent GOx-activity was significantly increased with increasing concentration of MB in the GOx-adsorption solution. The GOx-immobilization protocol on CF is very straightforward [i.e., adsorption of the GOx/MB mixed aqueous solution for 5 min under ultrasound (US)-irradiation]. Under the optimized operational conditions (i.e., applied potential, 0 vs. Ag/AgCl; carrier pH, 5.0; carrier flow rate, 4.0 mL min-1), the resulting GOx/MB-CF-reactor and HRP/TN-CF-detector combined amperometric flow-biosensor exhibited sensitive, selective, reproducible and stable cathodic peak current responses to glucose with the following analytical performances: sensitivity, 6.22 μA mM-1; linear range, 0.01 to 1 mM; limit of detection, 9.6 μM (S/N = 3, noise level, 20 nA); sample throughput, 46-96 samples per h for 10-0.1 mM glucose. The developed amperometric flow-biosensor allowed the determination of glucose in beverages and liquors, and the analytical results by the sensor were in fairly good agreement with those by conventional spectrophotometry.

Brilliant green sequestered poly(amic) acid film for dual-mode detection: Fluorescence and electrochemical enzymatic biosensor

Herein, we report a facile technique to fabricate fluorescent polymeric structure, brilliant-green sequestered poly(amic) acid film (BG-PAA), as enzyme support-material for biosensor applications. The structure and fluorescence properties of the fabricated BG-PAA membrane were investigated using 1H NMR, scanning electron microscopy (SEM) and fluorescence microscopy. Glucose oxidase (GOx) was used as a model enzyme that immobilized on BG-PAA membrane using glutaraldehyde. The created BG-PAA/GOx membrane was utilized to fabricate dual-purpose as fluorescent and electrochemical biosensors for the determination of glucose in beverages. Utilization of the dissolved oxygen in GOx mediated glucose oxidation resulted in alteration of the measured fluorescence and current intensity. In the fluorescence assay, the decreased concentration of oxygen causes the increased fluorescence intensity due to the elimination of quenching effect of oxygen on BG fluorescence. In amperometric assay, decrease in oxygen concentration was followed at −0.7V. After optimization of working conditions linearity, limit of detection and repeatability of system were determined. Finally, BG-PAA/GOx was tested to analyze glucose in beverages.

Tannic Acid Modified Electrochemical Biosensor for Glucose Sensing Based on Direct Electrochemistry

AbstractA novel glucose biosensor was constructed through the immobilization of glucose oxidase (GOx) on gold nanoparticles (Au NPs) deposited, and chemically reduced graphene oxide (rGO) nanocomposite. In the synthesis, tannic acid (TA) was used for the reduction of both graphene oxide, and Au3+ to rGO, and Au NPs, respectively. Also, by harnessing the π‐π interaction between graphene oxide and TA, and protein‐TA interaction, a novel nanocomposite for the fabrication of a third generation biosensor was successfully constructed. Upon the oxidation of TA to quinone, which is easily reducible at the negative potential range, enhanced electron transfer was obtained. The cyclic voltammetry (CV) results demonstrated a pair of well‐defined and quasi‐reversible redox peaks of active site molecule of GOx. The biosensor exhibited a linear response to glucose concentrations varying from 2 to 10 mM with a sensitivity of 18.73 mA mM−1 cm−2. The fabricated biosensor was used for the determination of glucose in beverages.

Development of dual-emission ratiometric probe-based on fluorescent silica nanoparticle and CdTe quantum dots for determination of glucose in beverages and human body fluids

A novel dual emission ratiometric fluorescence probe for determination of glucose has been developed. The reference dye fluorescence isothiocyanate (FITC) has been encapsulated in the silica nanoparticles and then the red emission CdTe QDs were grafted on the surface of the silica particles to obtain the fluorescence probe. With glucose and dopamine as substrates, the glucose level was proportional to the fluorescence ratio change of above probe caused by dopamine oxidation, which was produced via bienzyme catalysis (glucose oxidase and horseradish peroxidase). The established approach was sensitive and selective, and has been applied to determine the glucose in beverage, urine and serum samples. The average recoveries of the glucose at various spiking levels ranged from 95.5% to 108.9% with relative standard deviations from 1.5% to 4.3%. The results provided a clue to develop sensors for rapid determination of the target analytes from complex matrices.

Selenium containing conducting polymer based pyranose oxidase biosensor for glucose detection

A novel amperometric pyranose oxidase (PyOx) biosensor based on a selenium containing conducting polymer has been developed for the glucose detection. For this purpose, a conducting polymer; poly(4,7-bis(thieno[3,2-b]thiophen-2-yl)benzo[c][1,2,5] selenadiazole) (poly(BSeTT)) was synthesized via electropolymerisation on gold electrode to examine its matrix property for glucose detection. For this purpose, PyOx was used as the model enzyme and immobilised via physical adsorption technique. Amperometric detection of consumed oxygen was monitored at −0.7V vs Ag reference electrode in a phosphate buffer (50mM, pH 7.0). KMapp, Imax, LOD and sensitivity were calculated as 0.229mM, 42.37nA, 3.3×10−4nM and 6.4nA/mMcm2, respectively. Scanning electron microscopy (SEM), Electrochemical Impedance Spectroscopy (EIS) and cyclic voltammetry (CV) techniques were used to monitor changes in surface morphologies and to run electrochemical characterisations. Finally, the constructed biosensor was applied for the determination of glucose in beverages successfully.

Glucose oxidase-modified carbon-felt-reactor coupled with peroxidase-modified carbon-felt-detector for amperometric flow determination of glucose

Glucose oxidase (GOx) and horseradish peroxidase (HRP) were covalently immobilized on a porous carbon-felt (CF) by using cyanuric chloride (CC) as a linking reagent. The resulting GOx-modified-CF (GOx-ccCF) was used as column-type enzyme reactor and placed on upstream of the HRP-ccCF-based H2O2 flow-detector to fabricate amperometric flow-biosensor for glucose. Sensor setting conditions and the operational conditions were optimized, and the analytical performance characteristics of the resulting flow-biosensor were evaluated. The chemical modification of the GOx via CC was found to be effective to obtain larger catalytic activity as compared with the physical adsorption. Under the optimized conditions (i.e., volume ratio of the GOx-ccCF-reactor to the HRP-ccCF-detector is 1.0; applied potential is −0.12V vs. Ag/AgCl; carrier pH is 6.5; and carrier flow rate is 4.3ml/min), highly selective and quite reproducible peak current responses toward glucose were obtained: the RSD for 30 consecutive injections of 3mM glucose was 1.04%, and no serious interferences were observed for fructose, ethanol, uric acid, urea and tartaric acid for the amperometric measurements of glucose. The magnitude of the cathodic peak currents for glucose was linear up to 5mM (sensitivity, 6.38±0.32μA/μM) with the limit detection of 9.4μM (S/N=3, noise level, 20nA). The present GOx-ccCF-reactor and HRP-ccCF-detector-coupled flow-glucose biosensor was utilized for the determination of glucose in beverages and liquors, and the analytical results by the sensor were in fairly good agreement with those by the conventional spectrophotometry.

Determination of glucose by a kinetic method on a thin-layer chromatogram using the oxidation of 3,3′,5,5′-tetramethylbenzidine with hydrogen peroxide

The oxidation of 3,3',5,5'�tetramethylbenzidine with hydrogen peroxide in aqueous solutions in the presence of iron(II, III) was studied on the surface of chromatography paper and TLC plates following the general approach to the purposeful selection of indicator reactions in kinetic methods of analysis. Among the 17 studied model analytes, the strongest inhibitory activity was detected for benzoic acid and glucose. The inhibitory effect of substances is likely due to their interaction with hydroxyl radicals forming in the indicator reaction. The most intense signal of glucose was detected on the surface of silica. Glucose was detected as a light spot against the blue background ( Rf ~ 0.5). A procedure for the semiquantitative determination of glu� cose on a thinlayer chromatogram based on the dep endence of the reflectometerregistered value of the reflectance coefficient on the logarithm of the analyte concentration is proposed. In the range 3 × 10 -5 - 0.01 M, two concentrations of glucose differing by one half order of magnitude can be distinguished. The detection limit is 1 × 10 -5 M. The procedure was applied to the determination of glucose in beverages, saliva samples, and in a fructose preparation.

Glucose biosensor based on graphite electrodes modified with glucose oxidase and colloidal gold nanoparticles

The electrochemistry of glucose oxidase (GOx) immobilized on a graphite rod electrode modified by gold nanoparticles (Au-NPs) was studied. Two types of amperometric glucose sensors based on GOx immobilized and Au-NPs modified working electrode (Au-NPs/GOx/graphite and GOx/Au-NPs/graphite) were designed and tested in the presence and the absence of N-methylphenazonium methyl sulphate in different buffers. Results were compared to those obtained with similar electrodes not containing Au-NPs (GOx/graphite). This study shows that the application of Au-NPs increases the rate of mediated electron transfer. Major analytical characteristics of the amperometric biosensor based on GOx and 13 nm diameter Au-NPs were determined. The analytical signal was linearly related to glucose concentration in the range from 0.1 to 10 mmol L−1. The detection limit for glucose was found within 0.1 mmol L−1 and 0.08 mmol L−1 and the relative standard deviation in the range of 0.1–100 mol L−1 was 0.04–0.39%. The τ1/2 of Vmax characterizes the storage stability of sensors: this parameter for the developed GOx/graphite electrode was 49.3 days and for GOx/Au-NPs/graphite electrode was 19.5 days. The sensor might be suitable for determination of glucose in beverages and/or in food.

Electrochemical biosensors based on colloidal gold–carbon nanotubes composite electrodes

Abstract The construction and performance of a novel colloidal gold–carbon nanotubes (CNT) composite electrode using Teflon as the non-conducting binding material, is reported. The resulting Aucoll–CNT–Teflon electrode shows significantly improved responses to hydrogen peroxide when compared with other carbon composite electrodes, including those based on CNTs. The incorporation of glucose oxidase (GOx) into the new composite matrix allowed the preparation of a mediatorless glucose biosensor. Once enzyme, CNT and colloidal gold loadings into the composite matrix were optimized, the analytical characteristics of the calibration graph for glucose, obtained by amperometry at +0.5 V, showed a remarkably higher sensitivity than that achieved with other GOx–CNT bioelectrodes. The calculated value of the apparent Michaelis–Menten constant, 14.9 mM, suggests a high affinity of the enzyme–substrate under the microenvironment provided by gold nanoparticles. Both repeatability of the amperometric measurements, reproducibility with different biosensors, lifetime and storage ability show a good analytical performance, which compares advantageously with previous GOx–CNT biosensor designs. The biosensor was applied for the rapid determination of glucose in beverages recommended for sport practice.

Determination of glucose using a coupled-enzymatic reaction with new fluoride selective optical sensing polymeric film coated in microtiter plate wells

The determination of glucose in beverages is demonstrated using newly developed fluoride selective optical sensing polymeric film that contains aluminum (III) octaethylporphyrin (Al[OEP]) ionophore and the chromoionophore ETH7075 cast at the bottom of wells of a 96-well polypropylene microtiter plate. The method uses a dual enzymatic reaction involving glucose oxidase enzyme (GOD) and horseradish peroxidase (HRP), along with an organofluoro-substrate (4-fluorophenol) as the source of fluoride ions. The concentration of fluoride ions after enzymatic reaction is directly proportional to the glucose level in the sample. The method has a detection limit of 0.8 mmol L −1, a linear range of 0.9–40 mmol L −1 and a sensitivity of 0.125 absorbance/decade of glucose concentration. Glucose levels in several beverage samples determined using the proposed method correlate well with a reference spectrophotometric enzyme method based on detection of hydrogen peroxide using bromopyrogallol red dye (BPR). The new method can also be used to determine H 2O 2 concentrations in the 0.1–50 mmol L −1 range using a single enzymatic reaction involving H 2O 2 oxidation of 4-fluorophenol catalyzed by HRP. The methodology could potentially be used to detect a wide range of substrates for which selective oxidase enzymes exist (to generate H 2O 2), with the high throughput of simple microtiter plate detection scheme.

A glucose biosensor with enzyme-entrapped sol–gel and an oxygen-sensitive optode membrane

An optical biosensor for the continuous determination of glucose in beverages based on the canalisation of glucose oxidase into a sol–gel is presented. The enzyme was entrapped within a glass matrix by the sol–gel method. The matrix was ground to a powder form and packed into a laboratory-made flow cell. This minireactor was positioned in a spectrofluorimeter connected to a continuous sample flow system. An oxygen-sensitive optode membrane was fabricated from tris(4,7-diphenyl-1,10-phenanthroline)ruthenium(II) didodecyl sulfate adsorbed on silica gel particles and entrapped in a silicone-rubber film. The membrane was situated against the wall of the flow cell to sense the depletion of oxygen content upon exposure to glucose. The change of the luminescence intensity of the optode membrane can be related to glucose concentration. The effects of temperature and pH on the response of the biosensor were investigated. Storage, stability and repeatability of the biosensor were also studied in detail. The analytical range of the biosensor was from 0.06 to 30 mmol dm−3 glucose and the time taken to reach a steady signal in a flowing solution was 5–8 min. The detection limit was found to be 6 μmol dm−3. Common matrix interferents such as fructose, galactose, lactose, raffinose, rhamnose, stachyose, sucrose and other components in beverage samples showed no interference. The glucose biosensor has been successfully applied to the determination of glucose contents of beverage samples.