Public defence, Biotechnology, MSc (Tech.) Maaria Malkamäki

Title of the thesis: Understanding the assembly process of structural proteins into functional materials

Thesis defender: Maaria Malkamäki
Opponent: Professor Tiffany Abitbol, École polytechnique fédérale de Lausanne (EPFL), Switzerland
Custos: Professor Markus Linder, Aalto University School of Chemical Engineering

Nature provides examples of fascinating protein-based materials, such as spider silk fibres. They are known for their remarkable properties that include high strength and elasticity. Silk fibres form via precise self-assembly of proteins, but reproducing silk materials in laboratory with comparable properties has proven to be challenging due to an incomplete understanding of the assembly process. Therefore, a deeper understanding of the protein assembly process into high-performance materials is needed to be able to develop new renewable protein materials.

In this thesis work, spider silk-like proteins produced by bacteria were used to study the protein assembly process from solution into solid functional materials, such as coatings. The effect of the surrounding environment, such as solvents, salts, surfaces, humidity, and post-treatment, on the silk assembly in solution, during drying, and as a solid material was studied. Ethanol was found to strongly affect the silk organisation in solution as well as improve solid silk coating adhesion to various different surfaces, such as glass, plastics, and nitrocellulose. Specific substrates were found to change silk organisation, leading to oriented fibrous structures on polytetrafluoroethylene (PTFE, Teflon) and the formation of highly hydrophobic and durable coatings on biomineralised bacterial cellulose.

Together, these results show that recombinant silk proteins can be used to form materials with outstanding properties. The findings improve our understanding of how the protein assembly process can be controlled in order to achieve high-performance materials. In the future, the findings will help scientists to fully control the material assembly and therefore develop sustainable protein materials with outstanding tailored properties.

Keywords: recombinant silk protein, protein assembly, coating, bio-inspired material

Thesis available for public display 7 days prior to the defence at Aalto University's public display page.