Biomolecular Electronics and Protonics from the NM- to the Macro-Scale, in Solution and in the Solid-State

Biological charge transfer processes, such as the ones in the respiratory system, are the basis for our life, where proteins are Nature’s main choice for the translocation of charges. As such, we as scientists have the obligation of understanding the fundamentals of these processes. In our research group we explore various types of charge transfer properties mainly across peptides and proteins, while distinguishing between electron and proton transfer. One experimental route that we use for exploring charge transfer properties is by attaching a charge donor (and/or acceptor) to the biological material (peptide, protein or membrane), and to follow the excited-state charge transfer by fast spectroscopy. The ability of biological molecules to mediate charges has resulted in the emerge of the bioelectronics field, where biomolecules are probed for their ability to mediate electronic conduction. In our group, we use different types of bioelectronic device configurations from the nm-scale to the macroscale to probe the ability of biomaterials to conduct both electrons and protons while applying an electric field. Here, we report on the use of the serum albumin (SA) protein for bioelectronic devices. We show that SA can be used both for molecular junctions (transport across a distance of 3 nm) and for the formation of freestanding protein-based material (transport across centimeters). In both cases, the protein can be molecularly doped, which results in an impressive increase in conductance. We attribute the charge conductance to electron hopping between dopant molecules. One of the end goals of our group is to design protein-based biomaterials with tunable electronic and protonic properties for the use of tissue engineering.