Metal protoporphyrin doped serum albumin mats conductivity

The research on charge transport mechanism in bio-materials is a developing area in the field of bioelectronics. In our study, we use the bioinspired platform of electrospun bovine serum albumin (BSA) mat, which is a free-standing protein-based material that displays proton conduction on the millimeters range,[1] to explore long-range charge transport. Doping the mats with Hemin (Iron-containing protoporphyrin) significantly improves the mat`s conductivity due to an additional process of electron transfer.[2] This process has been suggested to be electron hopping between hemin molecules. In our new work, we explore the role of the metal in the conduction mechanism of the doped mat. Removal of the Iron in the protoporphyrin IX (PPIX) center or replacing it with other transition metals allows us to isolate the metal contribution to the conductance mechanism. FePPIX, CoPPIX, ZnPPIX, CuPPIX, and free-metal PPIX serve as dopants in this study. We use AC Electrochemical Impedance Spectroscopy (EIS) measurements to extract the conductivity of the doped mats and to separate between processes in the material with different relaxation frequency. We present a correlation between the mats` ability to bind the metal-PPIX or metal-free PPIX and the conductivity of the suitable doped mat.

[1] Amdursky et al., Long-Range Proton Conduction across Free-Standing Serum Albumin Mats. Adv. Mater. 2016, 28, 2692-2698.

[2] Amdursky et al., Electron Hopping Across Hemin-Doped Serum Albumin Mats on Centimeter-Length Scales. Adv. Mater. 2017, 29, 1700810.