Challenges in engineering conductive protein fibres: Disentangling the knowledge

Conductive protein materials are promising candidates for next-generation bioelectronics due to their genetically-customizable functionalities, biocompatibility, and bioactivity. We envision that they could be used in a variety of bio-friendly functional devices, including bio-electronic interfaces, bio-energy devices, and sensors. However, their practical uses are limited by gaps in our understanding of charge transport in proteins, and by challenges in establishing reliable data collection methods. Moreover, characterization protocols are not always designed with applications in mind, which hinders engineering developments. Here, we review the effects of sample preparation, environmental conditions (ie, hydration level, pH, temperature), measurement scale (nano, micro, and macro), and geometrical considerations, on the measured electrical properties of proteins. We emphasize the need for standardized methods and collaborations across fields for the design of conductive protein materials, keeping in mind their end goal applications. Our objective for this review is to disentangle the knowledge on protein conductivity, and to clarify the current challenges, limitations, and future possibilities for these biological conductors.