Flexible amperometric transducers for biosensors based on a screen printed three electrode system

Screen printed three electrode sensors comprising a platinum working, a carbon counter and an Ag ∣ AgCl pseudo reference electrode were developed employing polymer thick film inks. The sensors were constructed as amperometric transducers for multianalyte biosensors for use in batch, as well as in flow through systems. The characteristics of the sensors were determined. The active surface area of the Pt working electrodes was determined using electrochemical and SEM studies. Cyclic voltammograms of the ferricyanide/ferrocyanide couple showed that the reaction was quasi-reversible at these electrodes. Although the surface was not ideal for this redox couple, the sensors proved to be reproducible and well suited for the determination of hydrogen peroxide and thus for biosensors based on oxidases as biologically active compounds. The combination of two pretreatment steps, an additional heat curing and an electrochemical preconditioning step, was found to be most helpful to reduce background current and settling time of the sensors. Different aspects of the changing surface composition are discussed. The sensors with optimized preconditioning showed linear ranges from 10 μM up to at least 500 μM hydrogen peroxide and sensitivities of 6.97±0.20 nA μM^?1 hydrogen peroxide for uncovered, 4.01±0.08 nA μM^?1 hydrogen peroxide for PCS/BSA membrane covered and 0.222±0.002 nA μM^?1 hydrogen peroxide for Nafion^® coated platinum working electrodes. Moreover, optimized transducers with immobilized sarcosine oxidase (sensitivity: 2.30±0.07 nA μM^?1 sarcosine) demonstrated the feasibility of the sensor concept, the manufacturing and pretreatment processes for the development of enzyme sensors.