Kinetic behaviour of dopamine-polyphenol oxidase on electrodes of tetrathiafulvalenium tetracyanoquinodimethanide and tetracyanoquinodimethane species

This paper presents a study of the electrochemical behaviour of polyphenol oxidase onto conducting organic salt electrodes using dopamine as enzymatic substrate. The enzyme is immobilized behind a dialysis membrane. TTF·TCNQ and carbon paste with TCNQ⁰ and NaTCNQ are employed, and the role of the different salt components as enzyme regeneration mediators is analysed under anaerobic conditions. It is concluded that both TCNQ⁰ and NaTCNQ species are able to regenerate the active enzyme although chemical reactions between the species make it difficult to discriminate their behaviour. Results strongly suggest a heterogeneous mechanism for the enzymatic reaction and NaTCNQ as enzymatic regenerator on TTF·TCNQ. Apparent Michaelis-Menten constants are evaluated. The results clearly point to an enzymatic control of the reaction rate under our experimental conditions. A chemical catalytic effect due to coupled chemical reactions is also described. The biosensors analysed are potentially useful from the analytical point of view. Different electrode materials were analysed: TTF·TCNQ and carbon paste with TCNQ⁰ and NaTCNQ.