Synthetic biology offers the opportunity to design and produce novel protein-based materials with tunable properties. One type of such protein is silk-amyloid-mussel foot proteins (SAMs) consisting of β-amyloid peptide, spider silk domain, and mussel foot protein (Mfp). Hydrogels of SAMs display unique tunability, biocompatibility, bio-absorbability, strong cohesion, and underwater adhesion, making them attractive candidates for various biological surfaces. Understanding the relationships between protein sequence and hydrogel properties is important to designing tunable SAM hydrogels for different biomedical applications. Here, we fabricated SAM hydrogels using hybrid proteins of varying lengths of silk-amyloid repeats and Mfps and characterized their structure and properties. We found that increasing silk-amyloid repeats enhanced hydrogel’s β-sheet content (r = 0.74), leading to higher cohesive strength and toughness. Additionally, increasing Mfp length beyond half-length of the full Mfp sequence (½Mfp) decreased β-sheet content (r = -0.47), leading to higher cohesive strength and toughness. Among different variants, hydrogel made of 16xKLV-2Mfp displayed a high ultimate strength of 3.0±0.3MPa, an ultimate strain of 664±119%, and an attractive underwater adhesivity of 416±20kPa to porcine skin. In summary, the sequence-structure-property relationships learned from this project will be useful to guide the design of future protein adhesives with tunable properties for tailored surgical applications.

(a)The design and process of SAM proteins.(b)An image of SAM hydrogel and the proposed protein structure. (c)β-sheet content of each SAM hydrogel from FTIR spectra.

(a)Tensile testing set-up and resulting mechanical properties.(b)Schematic showing an adhesion set-up and adhesive shear stress.(c)Correlation analysis between the protein properties.

Juya Jeon

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