Electrochemical behavior of polyphenol oxidase immobilized in self-assembled structures layer by layer with cationic polyallylamine

We report here a novel bioelectrode based on self-assembled multilayers of polyphenol oxidase intercalated with cationic polyallylamine built up on a thiol-modified field surface. We use an immobilization strategy previously described by Hodak J, et al. (Langmuir 1997, 13, 2708-2716) Quartz crystal microbalance with electro-acustic impedance experiments were carried out to follow quantitatively the multilayer film formation. The response of the s elf-assembly polyphenol oxidase-polyallylamine electrodes toward different metabolically related cate-cholamines was studied, to evaluate enzyme kinet ics. For the analyzed compounds, only dopamine and its metabolite Dopac gav e catalytic currents at applied potential close to 0V. These responses were proportional to the number of polyphenol oxidase-immobilized layers and we re also controlled by the enzymatic reaction. The combination of microgravi metric and electrochemical techniques allowed us to determine the kinetic e nzymatic constants, showing that the decomposition rate for the enzyme-subs trate complex is slower than the enzymatic reoxidation step.