Design of a biosensor based on 1-(4-nitrophenyl)-2,5-di(2-thienyl)-1H pyrrole

Immobilization of polyphenol oxidase (tyrosinase, E.C. 1.14.18.1) was achieved on a copolymer of 1-(4-nitrophenyl)-2,5-di(2-thienyl)-1H-pyrrole [SNS(NO2)] with pyrrole ([SNS(NO2)]/PPy) via electrochemical polymerization. Two different substrates; catechol and l-tyrosine were used for the characterization of biosensor. The kinetic parameters of the biosensor, maximum reaction rate of the enzyme (Vmax) and Michaelis–Menten constant (Km) were determined for two different substrates. Vmax was found as 0.02 μmol/min electrode for both substrates. Km values were determined as 250 and 2 mM for catechol and l-tyrosine respectively. Calibration curves for enzyme activity versus substrate concentration were plotted between 0.05 and 0.5 M catechol and between 0.8 and 2.5 mM l-tyrosine. Optimum temperature and pH, operational and storage stabilities of immobilized enzyme were examined.