Laccase biosensor on monolayer-modified gold electrode

Laccase enzymes from two different sources, namely, tree laccase from Rhus vernicifera and fungal laccase from Coriolus hirsutus were used for the development of biosensor for catechol. Laccase was immobilized onto the amine terminated thiol monolayers on gold surface by glutaraldehyde coupling. From the different thiol monolayers investigated, cystamine was found to be optimal with respect to sensitivity, stability, reproducibility, and other electrochemical properties of the enzyme electrode. Linear calibration in the range between 1 and 400 muM for catechol was obtained for fungal laccase covalently coupled on the electrode surface. The kinetic parameters determined using the Lineweaver-Burk and Eadie-Hofstee plots were K-m = 0.65 mM and V-max = 24.5 muA for fungal laccase compared to K-m = 5.4 mM and V-max = 6.6 muA for tree laccase on cystamine monolayer. The electrode showed good stability for 1 month without loosing appreciable activity when stored dry in a refrigerator at - 20degreesC.