Microbially Synthesized Repeats of Mussel Foot Protein Display Enhanced Underwater Adhesion

Mussels strongly adhere to a variety of surfaces by secreting byssal threads that contain mussel foot proteins (Mfps). Recombinant production of Mfps presents an attractive route for preparing advanced adhesive materials. Using synthetic biology strategies, we synthesized Mfp5 together with Mfp5 oligomers containing two or three consecutive, covalently-linked Mfp5 sequences named Mfp5⁽²⁾ and Mfp5⁽³⁾. The force and work of adhesion of these proteins were measured underwater with a colloidal probe mounted on an atomic force microscope and the adsorption was measured with a quartz crystal microbalance. We found positive correlations between Mfp5 molecular weight and underwater adhesive properties, including force of adhesion, work of adhesion, protein layer thickness, and recovery distance. DOPA-modified Mfp5⁽³⁾ displayed a high force of adhesion (201 ± 36 nN μm^-1) and a high work of adhesion (68 ± 21 fJ μm^-1) for a cure time of 200 s, which are higher than those of previously reported Mfp-mimetic adhesives. Results presented in this study highlight the power of synthetic biology in producing biocompatible and highly adhesive Mfp-based materials.