Thesis presented June 14, 2022

Abstract:
Either resulting from misfolding or functional structuration, amyloid fibers are biological materials resulting from the self-assembling of identical proteins into unique one-dimensional ultra-high aspect ratio (>1000) nanowires. These fibrils are all different depending of the constituting protein but share common structural features well described in literature. Aside structure, amyloid-based materials gathered a lot of interest in the growing field of biomaterials, most particularly bioelectronics and biosensors. In this framework, we used a wide range of techniques, going from pure electrical characterization to large instrument X-Ray structural analysis in order to determine and characterize properties of several amyloid fibril materials. In this thesis, we highlighted three new and distinct macroscopic properties of α-lactalbumine amyloid fiber materials: generation of an open circuit voltage in high humidity environment, transformation of light polarization and generation of a long-term stable tryptophyl radical inducing red/magenta color in certain form of the material. Throughout exhaustive description of α-lactalbumine optical, “electrical” and structural micro and nanoscale features, we were able to enunciate hypothesis on how such exotic properties could arise in our amyloid fiber material. We show that most features are consequence of unusual high structuration of amyloid fibrils within the material, creating crystalline phases in the packed amyloid medium and more. This material-based study of amyloid fibril is quite unique in the literature, paving the way for future investigation of other amyloid properties that could be of use in the bioelectronic devices of tomorrow.

Keywords:
Bionanowires, biophysics, bioelectronics, proteins