We propose monitoring of diabetes through continuous analysis of undiluted sweat immediately after its excretion using a flow-through glucose biosensor. The used biosensors are based on Prussian Blue and glucose oxidase immobilized in perfluorosulfonated ionomer or gel of alkoxysilane; the resulting sensitivity with the latter reaches in batch mode 0.23 A M–1 cm–2, and the calibration range is from 1 μM to 1 mM (flow-through mode). On the basis of the glucose tolerance test known to be a clinically relevant procedure to mimic hyperglycemia, a positive correlation between the rates of glucose concentration increase in blood and in noninvasively collected sweat has been observed (r = 0.75). The observed correlation between sweat and blood considering low-molecular weight metabolites is even better than that observed previously between capillary and vein blood, confirming diagnostic value of sweat for diabetes monitoring. The dynamics of sweat glucose concentration, recorded by means of the proposed biosensor, is in a good accordance with the dynamics of blood glucose content without any time delay, thus offering a prospect for noninvasive monitoring of diabetes.

Wiring glucose oxidase in the membrane with an immobilized mediator is possible due to the diffusion ability of the latter, if the enzyme containing membrane is formed according to the proposed protocol, including exposing proteins to water-organic mixtures with the high content of organic solvent. In the course of the study, the new glucose oxidase mediator, unsubstituted phenothiazine, was discovered. The diffusion coefficient of the mediator in the resulting membrane is independent of the presence of enzyme. The cyclic voltammograms of the enzyme electrode after appearance of the only glucose in solution obtain a well-defined catalytic shape, which is normally observed for both the enzyme and the mediator in solution. Analytical performances of the resulting biosensor are comparable to the advanced second generation ones, which, however, require covalent linking of the mediator either to the membrane forming polymer or to the enzyme. Even without such covalent linking, the reported biosensor is characterized by an appropriate long-term operational stability allowing reagentless sensing.

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