Efficiency of site-specific clicked laccase-carbon nanotubes biocathodes towards O2 reduction

Abstract : A maximization of a direct electron transfer (DET) between redox enzymes and electrodes can be obtained through the oriented immobilization of enzymes onto an electroactive surface. Here, we present a strategy for obtaining carbon nanotube (CNTs) based electrodes covalently modified with perfectly control-oriented fungal laccases. Modelisations of the laccase-CNT interaction and of electron conduction pathways serve as guide in choosing grafting positions. Homogeneous populations of alkyne-modified laccases are obtained via the reductive amination of a unique surface accessible lysine residue selectively engineered near either one or the other of the two copper centers in enzyme variants. Immobilization of the site-specific alkynated enzymes is achieved via copper click on azido-modified CNTs. A highly efficient reduction of O 2 at low overpotential and catalytic current densities over-3 mA cm −2 are obtained by minimizing the distance from the electrode surface to the trinuclear cluster.