Development of a potentiometric catechol biosensor by entrapment of tyrosinase within polypyrrole film

A method is described for the construction of a potentiometric catechol biosensor by entrapment of tyrosinase (polyphenol oxidase; PPO) into a conducting polypyrrole film on a platinum electrode. The optimum conditions for the formation of the PPy-Tyr (polypyrrole-tyrosinase) film include a current density of 0.5 mA cm(-2), a polymerization period of 150s, 0.1 M pyrrole and 50 U mL(-1) tyrosinase. The presence of tyrosinase in the polymer film was confirmed by scanning electron microscopy (SEM), cyclic voltammetry (CV) and potentiometric measurements. The PPy-Tyr biosensor gave a sensitivity of 10 mV/mu M for catechol, with a response time of 80s. The optimum potentiometric measurement of catechol was achieved in 0.1 M phosphate buffer within a pH range of 6.5-7.5 and the lowest detectable concentration under these conditions was 1.0 mu M. A linear concentration range of 1-16 mu M catechol was obtained based on Nernstian response, but a non-Nernstian response demonstrated a linear range of 1-50 mu M. The PPy-Tyr biosensor was stable for at least 1 month when stored in a buffer at about 4 degrees C. (C) 2009 Elsevier B.V. All rights reserved.