Immobilization of polyphenol oxidase on polypyrrole films for application in biosensors

Amperometric biosensors were fabricated based on a crude enzymatic extract of avocado as a source of polyphenol oxidase (PPO) immobilized on polypyrrole (PPY) films electrodeposited on fluorine-tin-oxide glass (FTO) electrodes. These enzymatic electrodes can be applied for determination of phenolic compounds from pesticides. The working electrode, FTO, was initially modified with a thin PPY film electrodeposited in a non-aqueous medium solution. The pre-deposited FTO/PPY films allowed us to obtain thicker and homogeneous PPY-PPO films by cyclic voltammetry in an aqueous medium solution. The enzyme, PPO, was immobilized onto FTO/PPY films by electropolymerization of pyrrole in the presence of crude PPO extract at a fixed amount. The PPY-PPO films exhibited a high sensitivity for catechol in solution and a highly selective response at very low concentrations of catechol. A detection limit of around 10 nmol L/sup -1/ for catechol was estimated for PPY-PPO films.