Environmental post-processing increases the adhesion strength of mussel byssus adhesive

Abstract

Marine mussels (Mytilus trossulus) attach to a wide variety of surfaces underwater using a protein adhesive that is cured by the surrounding seawater environment. In this study, the influence of environmental post-processing on adhesion strength was investigated by aging adhesive plaques in a range of seawater pH conditions. Plaques took 8–12 days to achieve full strength at pH 8, nearly doubling in adhesion strength (+94%) and increasing the work required to dislodge (+59%). Holding plaques in low pH conditions prevented strengthening, causing the material to tear more frequently under tension. The timescale of strengthening is consistent with the conversion of DOPA to DOPA-quinone, a pH dependent process that promotes cross-linking between adhesive proteins. The precise arrangement of DOPA containing proteins away from the adhesive-substratum interface emphasizes the role that structural organization can have on function, an insight that could lead to the design of better synthetic adhesives and metal-coordinating hydrogels.

Keywords:

• Protein cross-linking
• underwater adhesion
• mussel foot protein (Mfp)
• Mytilus trossulus
• 3,4-dihydroxyphenly-L-alanine (DOPA)

Acknowledgements

The authors thank Jessie Andino, Benjamin Pedigo, MacKenzie Edelsward, and Chloe Peterschmidt for assistance with tensometer testing, Micah Glaz for support with AFM analysis, and Ian Jefferds, Dominic Pangelinan, and all the mussel growers at Penn Cove Shellfish. They would also like to thank the three anonymous reviewers whose suggestions led to significant improvements in the manuscript.