(Invited) Role of Organic Solvents in Immobilizing Fungus Laccase on Single-Walled Carbon Nanotubes for Improved Current Response in Direct Bioelectrocatalysis

Abstract

Tuning interactions between proteins and solid surfaces is important for rationalizing molecular orientation of redox enzymes immobilized on the electrode to favor an efficient direct bioelectrocatalysis. Supramolecular docking calls for specific “linker” molecules to direct the position of enzyme redox active sites on surfaces of electrodes or conductive nanomaterials, for example, carbon nanotubes (CNTs). In this work we focus on a high-potential fungus laccase, a multi-copper oxidase that catalyzes electroreduction of oxygen, and investigate the regulative effects of organic solvents on laccase immobilization on single-walled CNTs (SWCNTs) and its direct bioelectrocatalytic activity. Herein the maximum reductive current response is dramatically improved by 600% through ethanol-assisted enzyme immobilization, which is a result of ethanol-promoted laccase-SWCNT contact and favorable enzyme orientation on SWCNTs from conformation analysis. Extended investigation on more organic solvents with distinct physiochemical properties show that organic solvents with lower polarity, weaker denaturing capacity and higher vapor pressure are well-suited for assisting DET. This study reveals that organic solvents regulate laccase immobilization for direct bioelectrocatalysis by balancing surface wetting and protein denaturing. It further solidifies our fundamental knowledge of bioelectrochemistry of laccase and may inspire the design of electrode-enzyme interfaces with tunable surface wettabilities. Figure 1