Scientists at the Ural Federal University have solved the problem of synthesizing enzyme-free catalysts for glucose sensors. They proposed to deposit the surface of the electrode (test strip) with palladium and silver. Sensors with such strips will more accurately determine the concentration of glucose in the blood, they are more durable, less whimsical to storage conditions and, according to preliminary calculations by the developers, are cheaper than existing analogues with enzymes (one strip requires millionths of a gram of metals). The study was supported by a grant from the Russian Science Foundation. An article describing the method of layer-by-layer electrochemical deposition was published in the Russian Chemical Bulletin. This is the first description of such a method in the scientific literature.
“We used a printed electrode for deposition – a miniature substrate coated with a suspension of multi-walled, that is, inserted into each other, carbon nanotubes. Water from the suspension deposited on the electrode evaporates, while the nanotubes remain on the electrode, thus increasing its specific surface area. Then we alternately deposited silver and then palladium on the modified electrode surface several times, ”says Andrey Okhokhonin, Associate Professor of the Department of Analytical Chemistry of the Ural Federal University, head of the research group.
The layered deposition method is as follows. The electrode is alternately lowered into solutions of silver salt and palladium salt in dilute sulfuric acid. In this form, silver and palladium are missing one and two electrons, respectively, before the transition to the insoluble metallic state. By placing an electrode in a solution, an electric current is applied to it. The current reduces metals, and this leads to the formation of solid particles on the surface of the electrode. The operation is repeated four times. The new system, the developers say, can be used to create an enzyme-free electrocatalytic sensor for determining glucose in whole blood.
“This technique has not yet been applied, it turned out to be effective. The resulting new material has significant catalytic activity in the electrochemical oxidation of glucose. At the same time, in contrast to analogs, the oxidation reaction effectively proceeds in a neutral medium of a phosphate buffer solution, which corresponds to the acidity of human blood. Other similar systems are either noticeably less sensitive to glucose, or operate in an alkaline environment and provide for an additional stage of dilution of blood samples, in certain cases a thousand times. All this complicates the procedures and reduces the reliability of the analysis results, ”emphasizes Andrey Okhokhonin.
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