Mediatorless catalytic oxygen reduction at boron-doped diamond electrodes

Most approaches to electron conduction from electrode to the enzyme requires the use of mediators – molecular relays which can take electrons from the electrode and deliver them to the redox sites of the enzyme. In the present paper, the biocatalytic reduction of oxygen to water in the presence of laccase is shown to proceed on the boron-doped diamond at highly positive potentials and without any additional mediator. The onset of catalytic reduction current appears at 0.805 V vs. NHE in solutions of pH 5.2. Laccase is either dissolved in the solution or trapped on the BDD electrode in a thin film of lipidic cubic phase. The remarkable stability of the modified electrode, avoiding the use of mediators and positive potential of the dioxygen reduction process make the BDD–laccase system especially interesting for applications in electrochemical sensing and microbiofuel cells.