FLEXIBLE GRAPHITE ELECTRODE BASED ON ELECTROLYTIC MnO₂ FOR ENZYME-FREE GLUCOSE OXIDATION

Continuous glucose monitoring (CGM) is considered to be the most advanced system for the minimally invasive blood sugar control. The working electrode of the CGM sensor should possess a number of properties such as flexibility to ensure the safety of an insertion under the skin, analytic signal stability, resistance to temperature, pH of the surrounding medium, humidity and mechanical stress (the friction against clothing when wearing or accidental impact). Enzymatic sensors, which are part of the vast majority of modern glucose meters, are affected by all the above impacts during both the operation and storage, because of the glucose oxidase enzyme that is the main constituent of the electrode of the sensor. In that regard the development of the enzyme-free electrode for glucose oxidation is still a contemporary task until now. This work is devoted to the fabrication of a flexible carbon electrode based on electrolytic manganese dioxide for enzyme-free glucose oxidation and to the determination of the activity dependence on the deposition potential of manganese dioxide on a flexible graphite foil (GF) from the MnSO4 solution. As a result of this study, the electrolytic MnO2 was shown to act as an enzyme-free electrocatalyst for glucose oxidation, and the deposition potential of the manganese dioxide on a graphite electrode was found to affect appreciably on its activity. It is shown that manganese dioxide obtained under low deposition rate possesses the highest activity, and the flexible graphite electrode based on it demonstrates a wide linear range (1-30 mM) of the dependence of the oxidation current on the square root of the glucose concentration. The sensitivity of the electrode was found to be 11.4 and 22.3 mu A/(cm(2).mM(0.5)) at 25 and 36degree celsius, respectively, which indicates that the sensor not only does not fail when the temperature rises, but also becomes twice as sensitive under conditions close to the real practical application.