Inhibition Of Glucose Oxidase Research Articles

Stabilization of enzyme-immobilized hydrogels for extended hypoxic cell culture.

In this work, glucose oxidase (GOx)-immobilized hydrogels are developed and optimized as an easy and convenient means for creating solution hypoxia in a regular incubator. Specifically, acrylated GOx co-polymerizes with poly(ethylene glycol) diacrylate (PEGDA) to form PEGDA-GOx hydrogels. Results show that freeze-drying and reaction by-products, hydrogen peroxide, negatively affect oxygen-consuming activity of network-immobilized GOx. However, the negative effects of freeze-drying can be mitigated by addition of trehalose/raffinose in the hydrogel precursor solution, whereas the inhibition of GOx caused by hydrogen peroxide can be prevented via addition of glutathione (GSH) in the buffer/media. The ability to preserve enzyme activity following freeze-drying and during long-term incubation permits facile application of this material to induce long-term solution/media hypoxia in cell culture plasticware placed in a regular CO2 incubator.

Fast Fourier transformation electrochemical impedance spectroscopy for the investigation of inactivation of glucose biosensor based on graphite electrode modified by Prussian blue, polypyrrole and glucose oxidase

In this study we report the application of fast Fourier transformation electrochemical impedance spectroscopy (FFT-EIS) for the evaluation of bioselective layer of amperometric glucose biosensor created by the entrapment of the enzyme glucose oxidase (GOx) within composite polypyrrole (Ppy) and Prussian blue (PB) based layer. Additionally, chronoamperometry and atomic force microscopy (AFM) were applied for the characterization of graphite electrodes (GE) modified with bioselective layer of PB/Ppy/GOx. AFM investigations reveal that the variation of pyrrole concentration in the range of 10–30mM did not show significant differences in the surface roughness because calculated root mean square (RMS) was in the range of 15–19nm. In another set of experiments, which were based on FFT-EIS, only a small variation in charge transfer resistance was observed before and after application of GE/PB/Ppy/GOx electrodes for amperometric determination of glucose concentration. These findings preliminary suggest that those electrochemical properties of GE/PB/Ppy/GOx electrode, which could be detected by FFT-EIS method, do not vary significantly during the use of this electrode in the detection of glucose. However, the amperometric signals of the GE/PB/Ppy/GOx electrodes decrease during the measurements due to the mixed-type of GOx inhibition, as it was determined by the evaluation of cathodic currents vs glucose concentrations. These evaluations of amperometric response kinetics let us suggest that the decrease of biosensor signal is based on mixed-type (uncompetitive and non-competitive) inhibition of GOx.

Visible-light-activated photoelectrochemical biosensor for the detection of the pesticide acetochlor in vegetables and fruit based on its inhibition of glucose oxidase

A new and sensitive photoelectrochemical (PEC) biosensor which is visible-light-activated was fabricated based on acetochlor’s ability to inhibit glucose oxidase (GOx) activity.

Comparison of Cobalt Hexacyanoferrate and Poly(Neutral Red) Modified Carbon Film Electrodes for the Amperometric Detection of Heavy Metals Based on Glucose Oxidase Enzyme Inhibition

Electrochemical biosensors have been developed for the determination of cadmium, cobalt, and copper cations through their inhibitory effect on glucose oxidase activity, using cobalt hexacyanoferrate or poly(neutral red) as redox mediators. Cobalt hexacyanoferrate and poly(neutral red) were used to modify carbon film electrodes by electrodeposition and glucose oxidase was then immobilized on the electrode by crosslinking with glutaraldehyde. A comparison between the two redox mediated biosensors for the determination of the metal ions was performed under the same experimental conditions. In fixed-potential amperometry at −0.35 V vs. the saturated calomel electrode, the detection limits for the metal cations studied were in the low micromolar range, lower at glucose oxidase/cobalt hexacyanoferrate/carbon film electrode, and the lowest achieved with glucose oxidase inhibition measurements. The linear dynamic ranges were wider at the glucose oxidase/poly(neutral red)/carbon film electrode for all three metal ions. The 10% and 50% inhibition values (I10 and I50) for the metal cations were calculated and the degree of inhibition at the biosensors was compared. Copper ions inhibited glucose oxidase to the highest degree for both biosensors. The application for the analysis of tap water was demonstrated.

Methylglyoxal may affect hydrogen peroxide accumulation in manuka honey through the inhibition of glucose oxidase.

Although hydrogen peroxide (H₂O₂) is one of the major antibacterial factors in most honeys, it does not accumulate in medical-grade manuka honey. The goal of this study was to investigate the effect of artificially added methylglyoxal (MGO) on H₂O₂ accumulation in natural non-manuka honeys. H₂O₂ concentrations in the honey solutions were determined using a fluorimetric assay. Two, the most potent H₂O₂ producers honeydew honeys were mixed with MGO at final concentrations of 250, 500, and 1000 mg/kg, and incubated for 4 days at 37°C. Subsequently, H₂O₂ concentrations were determined in 50% (wt/vol) MGO supplemented honey solutions. In vitro crosslinking of the enzyme glucose oxidase (GOX) after incubation with MGO was determined by sodium dodecyl sulfate-polyacrylamide gel electrophoresis. Tested honeys at a concentration of 50% (wt/vol) accumulated up to 495.8±9.1 μM H₂O₂ in 24 h. The most potent producers were the two honeydew honeys, whose 50% solutions accumulated 306.9±6.8 and 495.8±9.1 μM H₂O₂, respectively. Levels of H₂O₂ increased significantly over time in both honey solutions. Contrary to this, the MGO-treated honeys generated significantly lower amounts of H₂O₂ (P<.001), and this reduction was dose dependent. In addition, MGO-treated GOX formed high molecular weight adducts with increasing time of incubation accompanied by loss of its enzymatic activity. High levels of MGO in manuka honey, by modifying the enzyme GOX, might be responsible for suppressing H₂O₂ generation. These data highlight the detrimental effect of MGO on significant proteinaceous components of manuka honey.

Glucose oxidase inhibition in poly(neutral red) mediated enzyme biosensors for heavy metal determination

A biosensor for the determination of heavy metal cations based on glucose oxidase enzymatic inhibition has been developed. The biosensor was assembled on carbon film electrode supports with glucose oxidase immobilised by cross-linking with glutaraldehyde on top of a film of poly(neutral red) as redox mediator, prepared by electropolymerisation. The biosensor was used to determine the metallic cations, cadmium, copper, lead and zinc in the presence of chosen amounts of glucose. The detection limits were found to be 1 μg L−1 for cadmium, 6 μg L−1 for copper, 3 μg L−1 for lead and 9 μg L−1 for zinc. Inhibition constants were determined by using the Dixon plot, and the type of inhibition induced by the metallic cations was evaluated from Cornish-Bowden plots plus Dixon plots, it being found that the inhibition is reversible and competitive for cadmium, mixed for copper and lead and uncompetitive for zinc. Copper-inhibited glucose oxidase to a greater extent followed by cadmium, lead and zinc. Regeneration of the glucose oxidase response was studied by using Ethylene diamine tetracetic acid metal-chelating agent and the nonionic surfactant Triton X-100. The suitability of the biosensor for determination in foodstuffs or beverages which contain trace concentrations of metals was investigated by performing recovery tests in commercial milk samples.

Bioelectrochemical activation and inhibition of polyaniline glucose oxidase electrode by cations

The effect of 14 metal cations and NH 4 + on the response current of a polyaniline glucose oxidase electrode is investigated in this paper. The immobilized glucose oxidase is only activated by Mn 2+ among investigated cations. Based on the experimental results, a mechanism of the activation kinetics of the immobilized glucose oxidase in the presence of Mn 2+ is presented, that is E + M ⇋ EM, EM + S ⇋ EMS → EM + P, and a rate equation from this model is given. The inhibition of glucose oxidase by Cu 2+ is reversible and non-competitive.