Construction of a biointerface on a carbon nanotube surface for efficient electron transfer

• Enzyme-CNT composite electrodes with highly oriented enzymes were prepared.
• Multi copper oxidase (Mcop) was used as the enzyme.
• Active center of the enzyme was aligned with the bulk direction of the electrolyte.
• Mcop-CNT electrode showed a current density of 190 μA/cm2 without a mediator.

Biodevices, which are obtained by immobilizing a biological functional molecule such as an enzyme or an antibody onto a conductive material surface, can be applied to biosensors and bio-fuel cells as a conversion and recognition element. In this study, we focus on carbon nanotubes (CNTs), which are utilized as scaffolding to facilitate electron transfer between the enzyme and electrodes. In order to achieve efficient enzymatic catalytic reactions on the CNT surface, we prepared a CNT-enzyme composite material by immobilizing an enzyme such that the active center of the enzyme was aligned with the direction of the bulk of the electrolyte solution. Multi copper oxidase from hyperthermophilic archaea Pyrobaculum aerophilium (Mcop) was immobilized onto the CNT surface with a high degree of orientation and the electrochemical characteristics of the resultant electrode are evaluated. The MWCNT-McoP modified electrode exhibited a current density of 190 μA/cm2 without a mediator. Proper immobilization of McoP onto the CNT surface facilitated direct electron transfer (DET) between the CNT and McoP via the four copper atoms in McoP without a mediator.