ИСТИНА

Biosensors after their discovery have found wide practical applications in various areas of human life. Current trend in clinical diagnostics as well as sports medicine is continuous monitoring of metabolites (for example, glucose and lactate). Accordingly, various biosensor based wearable devices are elaborated requiring high operational stability of the biosensors. Oxidases serve as terminal ones for more than 90% of enzyme based biosensors. The most progressive way to couple the oxidase-catalyzed and the electrochemical reactions is to detect hydrogen peroxide (H2O2), their side product. Prussian Blue (PB) is considered to be the most advantageous low-potential transducer for hydrogen peroxide over all known systems. Both the high sensitivity (more than 0.5 A/M·cm2) and selectivity in presence of oxygen are more than three orders of magnitude higher, than for commonly used Pt electrodes. Besides, PB in contrast to Pt is suitable for analysis of excretory liquids like sweat. The only disadvantage of the PB in respect to long-term continuous monitoring is their inherent instability, particularly in neutral solutions: hydroxyl ion (OH¯) known to be the product of H2O2 reduction is able to solubilize ferric hexacyanoferrate. Best way to stabilize the electrocatalyst is to use non-iron hexacyanoferrates isostructural to PB. Iron triad-mates form both chemically and mechanically stable hexacyanoferrates, especially nickel hexacyanoferrate (NiHCF). That was shown that the iron-nickel hexacyanoferrate bilayer is characterized by high catalytic activity, which is close to activity of pure PB as well as high operational stability, and high reproducibility. Thus, novel electrocatalyst for hydrogen peroxide reduction on the basis of transition metal hexacyanoferrates has been synthesized. 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 apparently the most labile lactate oxidase is significantly improved in terms of twice longer half inactivation and ≈3.5 times lower inactivation constant. The dynamic range of PB-NiHCF based biosensors is similar to it for conventional PB based ones, which allows using the former for similar purposes drastically improving their performance characteristics. In this way, stabilized PB based glucose and lactate biosensors could find wide application for non-invasive diagnostics.