Currently, mediator biosensors make it possible to determine the glucose content in biological fluids, food products and other complex samples, and the urgent task today is to develop the most convenient and accurate online biosensor for determining glucose levels. The developed biosensor includes a portable potentiostat, a 5 ml measuring cell and a screen-printed electrode. The working surface of the screen-printed electrode is modified with single-walled carbon nanotubes, bovine serum albumin covalently bound wuth neutral red and a glucose oxidase enzyme. Modification of bovine serum albumin with neutral red was carried out using glutaraldehyde. All measurements were carried out at pH = 7.0 (phosphate buffer solution, buffer solution salt concentration of 33 mM) and at an applied potential of -0.7 V. Modification of the working electrode with a biocomposite makes it possible to analyze glucose in the range of 0.1 – 60 mM. The functioning time of the system is 29 days. This range allows us to carry out online glucose monitoring of human blood samples, as well as of tear fluid, where glucose levels should average 0.1-0.3 mM for non-invasive measurements. The biosensor was tested on three samples of physiological fluids; a comparison of the results obtained with the data from the standard method using the Student's statistical test and Welch approximation showed a statistically insignificant difference in the results obtained via the different methods of analysis. Thus, the developed system may become an alternative analytical system for non-invasive monitoring of glucose levels in the future.

The study was supported by the Russian Science Foundation, grant No. 23-73-01220, https://rscf.ru/project/23-73-01220/»