Poly aryl amide and multiwalled carbon nanotube composite supported laccase electrode and its electrochemical behavior

Abstract

A novel strategy for the immobilization of laccase onto a glassy carbon electrode with high stability and electrocatalytic performance is presented. Laccase is attached to a matrix of mixed poly aryl amide (PAA) and multiwalled carbon nanotubes (MWCNTs) (denoted Lac/PAA-MWCNTs/GCE) by covalently bonding the surface amine group of laccase to the terminal carboxyl group of PAA and hydrophobic-hydrophobic interaction between MWCNTs and the laccase. The PAA backbone avoids the detachment and denaturing of the laccase, and the intermixed MWCNTs provide high electronic conductivity. The loading of laccase is 56.0 mg g-1 and more than 68% shows electrochemical activity. The electrode delivers direct electron transfer between the redox center of the laccase and the electrode with two pairs of redox peaks at 0.73 and 0.38 V, which is close to the formal potential of the T1 and T2 Cu-sites (0.78 and 0.39 V (vs NHE)), respectively. The onset potential for O2 reduction reaction (ORR) is ca 0.55 V in a phosphate buffer solution (pH=4.4). The Michaelis constant (KM) of the Lac/PAA-MWCNTs/GEs for O2 is 55.8 μmol L-1 and the detection limit of oxygen reaches 0.57 μmol L-1. After 2 months of storage at 4 °C the ORR activity of the Lac/PAA-MWCNTs/GC electrode retains ca 86% of its initial values and the peak potential of the ORR shifts negatively by ca 50 mV. Given the excellent catalytic performance towards ORR and its high stability this strategy will be widely applicable to the development of an enzyme-based cathode for biofuel cells and amperometric biosensors for oxygen. © Editorial office of Acta Physico-Chimica Sinica.