Glucose test strips with the largest linear range made via single step modification by glucose oxidase-hexacyanoferrate-chitosan mixture.

We report on the amperometric second-generation glucose test strips with the linear calibration range covering blood glucose concentrations. Chitosan membrane was used for immobilization of both enzyme and mediator in a single step. Optimal chitosan concentration in membrane-forming mixture corresponds to the highest enzyme activity and dramatically improved mediator adsorption in final membrane. On one hand, the immobilized glucose oxidase activation with an increase of the chitosan polymer content in the membrane has been noticed. On the other hand, positively charged chitosan matrix retains mediator (hexacyanoferrate (III) ion) in the membrane, due to its negative charge. Additionally, the excessive adsorption of the mediator on screen-printed electrodes coated with membranes was proved by means of cyclic voltammetry and impedance spectroscopy. Glucose test strips have been elaborated via single-step modification of the sensor support with the enzyme-mediator-polymer mixture. Apparently, the record linear calibration range from 1 mM to 50 mM glucose was achieved recording amperometric response at 5th second after potential was applied. The elaborated test strips have been validated through analysis of standard serum and blood samples. In whole blood test strips keep 84-98% of their sensitivity in buffer solution.