Composite electrochemical biosensors: a comparison of three different electrode matrices for the construction of amperometric tyrosinase biosensors

A comparison of the behaviour of three different rigid composite matrices for the construction of amperometric tyrosinase biosensors. which are widely used for the detection of phenolic compounds. is reported. The composite electrode matrices were, graphite-Teflon; reticulated vitreous carbon (RVC)-epoxy resin; and graphite-ethylene/propylene/diene (EPD) terpolymer. After optimization of the experimental conditions, different aspects regarding the stability of the three composite tyrosinase electrode designs were considered and compared. A better reproducibility of the amperometric responses was found with the graphite-EPD electrodes, whereas a longer useful lifetime was observed for the graphite-Teflon electrodes. The kinetic parameters of the tyrosinase reaction were calculated for eight different phenolic compounds, as well as their corresponding calibration plots. The general trend in sensitivity was graphite-EPD > graphite-Teflon much greater than RVC-epoxy resin. A correlation between sensitivity and the catalytic efficiency of the enzyme reaction for each phenolic substrate was found. Furthermore, differences in the sensitivity order for the phenolic compounds were observed among the three biocomposite electrodes. which suggests that the nature of the electrode matrix influences the interactions in the tyrosinase catalytic cycle. (C) 2002 Elsevier Science B.V. All rights reserved.