Preparation and Application of Functionalized Protein Fibrils

Abstract: Many proteins have an innate ability to self-assemble into fibrous structures known as amyloid fibrils. From a material science perspective, fibrils have several interesting characteristics, including a high stability, a distinct shape and tunable surface properties. Such structures can be given additional properties through functionalization by other compounds such as fluorophores. Combination of fibrils with a function yielding compound can be achieved in several ways. Covalent bond attachment is specific, but cumbersome. External surface adhesion is nonspecific, but simple. However, in addition, internal non-covalent functionalization is possible. In this thesis, particular emphasis is put on internal functionalization of fibrils; by co-grinding fibril forming proteins with a hydrophobic molecule, a protein-hydrophobic compound molecule composite can be created that retains the proteins innate ability to form fibrils. Subsequently formed fibrils will thus have the structural properties of the protein fibril as well as the properties of the incorporated compound. The functionalization procedures used throughout this thesis are applicable for a wide range of chromophores commonly used for organic electronics and photonics. The methods developed and the prepared materials are useful for applications within optoelectronics as well as biomedicine.Regardless of the methodology of functionalization, using functionalized fibrils in a controlled fashion for material design requires an intimate understanding of the formation process and knowledge of the tools available to control not only the formation but also any subsequent macroscale assembly of fibrils. The development and application of such tools are described in several of the papers included in this thesis. With the required knowledge in hand, the possible influence of fibrils on the functionalizing agents, and vice versa, can be probed. The characteristic traits of the functionalized fibril can be customized and the resulting material can be organized and steered towards a specific shape and form. This thesis describes how control over the process of formation, functionalization and organization of functionalized fibrils can be utilized to influence the hierarchical assembly of fibrils – ranging from spherical structures to  spirals; the function – fluorescent or conducting; and macroscopic properties – optical birefringence and specific arrangement of functionalized fibrils in the solid state. In conclusion, the use of amyloid fibrils in material science has great potential. Herein is presented a possible route towards a fully bottom up approach ranging from the nanoscale to the macroscale.