Laccase immobilization in redox active layered double hydroxides: A reagentless amperometric biosensor

This paper describes a new system for amperometric determination of dissolved oxygen and its application for the detection of anionic toxic substances, which are known as enzyme inhibitors. This biosensor is based on the co-immobilization of laccase from Trametes versicolor and a redox active layered double hydroxide [Zn–Cr–ABTS] on a glassy carbon electrode. The electrochemical transduction step corresponds to the electrocatalytic reduction of O2 at 0.2 V by laccase as catalyst and 2,2′-azino-bis(3-ethylbenzothiazoline-6-sulfonic acid) (ABTS) as mediator. Such device provides a fast and a sensitive response for dissolved oxygen determination between 6 × 10−8 and 4 × 10−6 M and very low detection limits for azide (5.5 nM), fluoride (6.9 nM) and cyanide (6.2 nM).