Biosensing L-DOPA with laccase-based enzyme electrodes: a comparative study

Abstract

The focus of the present work is to develop and optimize an electrochemical laccase-based biosensor for the determination of 3,4-dihydroxyphenyl-alanine, also known as L-DOPA. The biosensor was assembled on a conventional glassy carbon electrode, the surface of which was covered with laccase enzyme retained under a thin Nafion™ membrane. The enzymes used for this purpose were isolated and purified from the white-rot basidiomycetes (Trametes sp.) Trametes pubescens and Trametes versicolor. Although biochemically similar, the two enzymes demonstrated some differences in their affinity not only using 3,4-dihydroxyphenyl-L-alanine as enzyme substrate, but also when catecholamines such as dopamine and L-epinephrine were used. A range of electrochemical techniques were used for the study, such as cyclic voltammetry, chronoamperometry, and electrochemical impedance spectroscopy. Experiments were performed using buffers with different pH and applying various substrate concentrations. Activity and sensitivity of the two alternative laccase – based biosensors were compared by means of chronoamperometry. The biosensor produced on the basis of Trametes pubescens laccase, operating in citrate buffer with pH 4 proved to be more suitable than the one based on laccase purified from Trametes versicolor for biosensing L-DOPA.