A synthetic redox biofilm made from metalloprotein–prion domain chimera nanowires

Engineering bioelectronic components and set-ups that mimic natural systems is extremely challenging. Here we report the design of a protein-only redox film inspired by the architecture of bacterial electroactive biofilms. The nanowire scaffold is formed using a chimeric protein that results from the attachment of a prion domain to a rubredoxin (Rd) that acts as an electron carrier. The prion domain self-assembles into stable fibres and provides a suitable arrangement of redox metal centres in Rd to permit electron transport. This results in highly organized films, able to transport electrons over several micrometres through a network of bionanowires. We demonstrate that our bionanowires can be used as electron-transfer mediators to build a bioelectrode for the electrocatalytic oxygen reduction by laccase. This approach opens opportunities for the engineering of protein-only electron mediators (with tunable redox potentials and optimized interactions with enzymes) and applications in the field of protein-only bioelectrodes. A protein-only redox film inspired by the architecture of bacterial electroactive biofilms has been developed. The film is formed using a rubredoxin–prion domain chimeric protein. The prion domains self-assemble into fibres that are decorated with rubredoxin. This results in highly organized films, able to transport electrons over several microns, and wire enzymes to electrodes.