Impact Research of Physical-Chemical Factors on the Activity of Modified Enzyme Electrodes

To modify graphite electrodes with a conductive enzyme polymer matrix, the method of drip application of a liquid polymer solution of various compositions was used: polyvinylpyrrolidone (40%), chitosan (0.1%), glutaric dialdehyde (0.1%), glucoxidase and peroxidase in a ratio of 2:5. To assess the effect of the immobilization time (x1), the pH of immobilization (x2) and the enzyme/carrier ratio (x3) on the activity of the enzyme electrodes, a three-factor and three-level Box-Benken and RSM design was used. This model was able to adequately predict the results of immobilization within the range of variables used. The most favorable conditions and the largest number of molecules of the enzyme complex are in the electrochemically active state when they are immobilized on PVP using modifying agents chitosan and glutaraldehyde. The results demonstrate that the productivity of the enzymatic biofuel element is directly proportional to the activity of the immobilized GOX/HRP complex, since in this case the glucose oxidation reaction can proceed more efficiently.

DETERMINATION OF GLUCOSE OXIDASE ACTIVITY BY SPECTROPHOTOMETRIC METHOD

В статье рассматривается универсальная, чувствительная, быстрая и воспроизводимая методика определения активности глюкозооксидазы, основанная на окислении пероксидом водорода йодида калия в присутствии молибдата аммония и фотометрировании образующегося синего комплекса «йод-крахмал». Построен калибровочный график для определения концентрации пероксида водорода в реакционной смеси. Проведен анализ образования пероксида водорода в реакции окисления глюкозы глюкозооксидазой при варьировании начальной концентрации глюкозы. The article developed a universal, sensitive, fast and reproducible method for determining glucose oxidase activity, based on the oxidation of potassium iodide by hydrogen peroxide in the presence of ammonium molybdate and photometry of the resulting blue iodine-starch complex. A calibration graph is constructed to determine the concentration of hydrogen peroxide in the reaction mixture. Analysis of hydrogen peroxide formation in glucose oxidation reaction with glucose oxidase at variation of initial glucose concentration was performed.

Enzymatic enhancing of triplet–triplet annihilation upconversion by breaking oxygen quenching for background-free biological sensing

Triplet-triplet annihilation upconversion nanoparticles have attracted considerable interest due to their promises in organic chemistry, solar energy harvesting and several biological applications. However, triplet-triplet annihilation upconversion in aqueous solutions is challenging due to sensitivity to oxygen, hindering its biological applications under ambient atmosphere. Herein, we report a simple enzymatic strategy to overcome oxygen-induced triplet-triplet annihilation upconversion quenching. This strategy stems from a glucose oxidase catalyzed glucose oxidation reaction, which enables rapid oxygen depletion to turn on upconversion in the aqueous solution. Furthermore, self-standing upconversion biological sensors of such nanoparticles are developed to detect glucose and measure the activity of enzymes related to glucose metabolism in a highly specific, sensitive and background-free manner. This study not only overcomes the key roadblock for applications of triplet-triplet annihilation upconversion nanoparticles in aqueous solutions, it also establishes the proof-of-concept to develop triplet-triplet annihilation upconversion nanoparticles as background free self-standing biological sensors.

Electrocatalytic Oxidation of Glucose on Boron and Nitrogen Codoped Graphene Quantum Dot Electrodes in Alkali Media

A novel solvothermal technique has been developed in the presence of C/N/B precursor for synthesizing B-N-coped graphene quantum dots (GQDs) as non-metal electrocatalysts towards the catalytic glucose oxidation reaction (GOR). Both N-doped GQD and B-N-codoped GQD particles (~4.0 nm) possess a similar oxidation and amidation level. The B-N-codoped GQD contains a B/C ratio of 3.16 at.%, where the B dopants were formed through different bonding types (i.e., N‒B, C‒B, BC2O, and BCO2) inserted into or decorated on the GQDs. The cyclic voltammetry measurement revealed that the catalytic activity of B-N-codoped GQD catalyst is significantly higher compared to the N-doped GQDs (~20% increase). It was also shown that the GOR activity was substantially enhanced due to the synergistic effect of B and N dopants within the GQD catalysts. Based on the analysis of Tafel plots, the B-N-codoped-GQD catalyst electrode displays an ultra-high exchange current density along with a reduced Tafel slope. The application of B-N-codoped GQD electrodes significantly enhances the catalytic activity and results in facile reaction kinetics towards the glucose oxidation reaction. Accordingly, the novel design of GQD catalyst demonstrated in this work sets the stage for designing inexpensive GQD-based catalysts as an alternative for precious metal catalysts commonly used in bio-sensors, fuel cells, and other electrochemical devices.

Influence of Pd:Bi ratio on Pd-Bi/Al2O3 catalysts: structure, surface and activity in glucose oxidation

Pd-Bi nanoparticles show high efficiency in catalyzing gluconic acid production by glucose oxidation reaction. Although this type of catalysts was studied for some time, the correlation between bismuth content and...