Simultaneous co-immobilization of enzyme and a redox mediator in polypyrrole film for the fabrication of an amperometric phenol biosensor

A conducting polypyrrole film has been prepared on indium tin oxide coated glass plate by electropolymerization of pyrrole in an aqueous solution of enzyme, tyrosinase (PPO), and a redox mediator potassium hexacyanoferrate (II). The enzyme retains its bioactivity well within the polymer film. Phenol concentration in aqueous solution was quantitatively estimated by monitoring the electron exchange occurring in redox mediator within the polymer matrix i.e. direct reduction of Fe (III) to Fe (II) ion at +0.12V vs. Ag/AgCl. The results of amperometric response measurements conducted on enzyme electrode (PPO/Fe2+/PPY/ITO) show a sensitivity of 0.33 AM−1 cm−2 and a linear response range of 4.5–107.4 μM for phenol in aqueous medium. The electrode exhibits a response time of about 80 second and is stable for 4 months at 4 °C.