Hosting Adamantane in the Substrate Pocket of Laccase: Direct Bioelectrocatalytic Reduction of O2 on Functionalized Carbon Nanotubes

We report the efficient immobilization and orientation of laccase from Trametes versicolor on MWCNT electrodes using 1-pyrenebutyric acid adamantyl amide as a supramolecular linker. We demonstrate the ability of adamantane to specifically interact with the hydrophobic cavity of laccase, while pyrene interacts with MWCNT sidewalls by pi-pi interactions. Adamantane allows the oriented immobilization of laccases on MWCNT electrodes. Using an anthraquinone-modified pyrene derivative for comparison, adamantane-modified MWCNTs achieve the stable immobilization and orientation of a higher number of enzymes per surface units, as confirmed by electrochemistry, theoretical calculations, and quartz crystal microbalance experiments. Furthermore, the efficient direct electron transfer ensures bioelectrocatalytic oxygen reduction at high half-wave potential of 0.55 V vs SCE accompanied by no kinetic limitation by the heterogeneous electron transfer and maximum current densities of 2.4 mA cm(-2).