Determination of the Antioxidant Capacity in Medicinal Plants, Using a Laccase Screen Printed-Type Biosensor

The immobilization of Laccase from Trametes versicolor (TvL) by means of entrapment, cross-linking and covalent bonding methods is analyzed through the development and characterization of amperometric screen-printed sensors for phenolic compounds. In order to do the immobilization with each of the methods stated, polyvinyl alcohol (PVA), glutaraldehyde (GA) and N-ethyl-N’-(3-dimethylaminopropyl)carbodiimide clorhydrate (EDC), were used respectively; the electrochemical characterization was carried out at (30.0 ± 0.5) °C and pH = 4.70 ± 0.01. The apparent Michaelis-Menten constant, K_m´, for the enzymatic oxidation of hydroquinone, HQ, to p-quinone, Q, was used as comparison parameter, to provide information on the enzymatic kinetic parameters, as well as the analytic parameter linked directly to the biosensor. After comparing the different immobilization methods, it became apparent that the best one was cross-linking at 40 °C, that gave the lowest K_m´ ((170.1 ± 3.2) µM), and HQ limit of detection ((17.0 ± 6.6) µM) values. The antioxidant capacity of real samples, infusion of medicinal plants, was evaluated using this biosensor.