Impedimetric and amperometric bifunctional glucose biosensor based on hybrid organic-inorganic thin films

A novel glucose biosensor with an immobilized mediator was studied using electrochemical impedance spectroscopy (EIS) and amperometry measurements. The biosensor has a characteristic ultrathin form and is composed of a self-assembled monolayer anchoring glucose oxidase (GOx) covered with Langmuir-Blodgett (LB) films of Prussian blue (PB). The immobilized PB in the LB films acts as a mediator and enables the biosensor to work under a low potential (0.0 V vs. Ag/AgCl). In the EIS measurements, a dramatic decrease in charge transfer resistance (Rct) was observed with sequential addition of glucose, which can be attributed to enzymatic activity. The linearity of the biosensor response was observed by the variation of the sensor response (1/Rct) as a function of glucose concentration in the range 0 to 25 mM. The sensor also showed linear amperometric response below 130 mM glucose. The organic-inorganic system of GOx and PB nanoclusters demonstrated bifunctional sensing action, both amperometry and EIS modes, as well as long sensing stability for 4 days.