ИСТИНА

Nowadays biosensors have found wide practical applications in various areas of modern human life. Clinical diagnostics as well as sports medicine deals with continuous monitoring of metabolites, in particular, glucose and lactate. Therefore, various biosensor based wearable devices are elaborated requiring high operational stability of corresponding biosensors. The principle of the first generation oxidase-based biosensors is to detect hydrogen peroxide (H2O2), the side product of oxidase-catalyzed reaction. Prussian Blue (PB) is known to be the most advantageous electrocatalyst for hydrogen peroxide reduction. In neutral aqueous media, favorable for applications in life science as well as for biosensors, Prussian Blue is three orders of magnitude more active and more selective compared to the commonly used platinum [1]. Besides, PB in contrast to Pt is applicable for analysis of excretory liquids like sweat. The only disadvantage of the PB in respect to long-term continuous monitoring is its inherent instability, particularly in neutral solutions: hydroxyl ion (OH¯) known to be the product of H2O2 reduction is able to solubilize ferric hexacyanoferrate. Non-iron transition metal hexacyanoferrates (isostructural to PB, but chemically and mechanically more stable than PB), especially nickel hexacyanoferrate (NiHCF), being silent in the electrocatalysis of H2O2 reduction serve as excellent matrixes for stabilization of Prussian Blue [2]. Here we confirm that operational stability of the oxidase-based biosensors can be significantly improved stabilizing the transducer used. Operational stability of PB-NiHCF bilayer based biosensors and even immobilized lactate oxidase is significantly improved [3]. The dynamic range of PB-NiHCF based biosensors is similar to it for conventional PB based ones. The developed biosensors are characterized with drastically improved performance characteristics. In this way, the stabilized Prussian Blue based glucose and lactate biosensors could find application for non-invasive diagnostics. Using the developed stabilized biosensors we have detected the concentrations of glucose and lactate in patients samples of blood and sweat. Of particular interest is the fact, that the changes in blood and sweat lactate concentration is correlating. The similar correlation has been found for glucose concentrations in blood and sweat. References: 1. A. A. Karyakin, Prussian Blue and Its Analogues: Electrochemistry and Analytical Applications. Electroanalysis 2001, 13, 813-819. 2. N. A. Sitnikova, A. V. Mokrushina, A. A. Karyakin, Iron triad-mate hexacyanoferrates as Prussian Blue stabilizers: Toward the advanced hydrogen peroxide transducer. Electrochimica Acta 2014, 122, 173-179. 3. E. V. Karpova, E. E. Karyakina, A. A. Karyakin, Accessing Stability of Oxidase-Based Biosensors via Stabilizing the Advanced H2O2 Transducer. Journal of the Electrochemical Society 2017, 164(5), B3056-B3058.