Identification and characterization of a wet adhesive protein extracted from Dreissena bugensis , the freshwater quagga mussel

Mechanisms of wet adhesion have evolved in several aquatic organisms over millions of years. Yet, the repertoire of synthetic biocompatible wet adhesive materials is still limited. The byssus is a well-studied proteinaceous bioadhesive structure utilized by several bivalves to support sessile lifestyles in turbulent conditions. The quagga mussel (Dreissena bugensis) is a freshwater byssate and a notorious invasive species in the Great Lakes region. To identify adhesive proteins in the quagga mussel byssus, we utilized quantitative proteomics and found several proteins enriched at the byssus-substrate interface. Among the identified proteins was the Dbfp7 protein family. Dbfp7 is a small, polymorphic, and mostly disordered protein that lacks significant amounts of 3,4-dihydroxyphenylalanine (DOPA), a modified amino acid found in several marine mussel byssal proteins. Atomic force microscopy nanomechanical mapping of Dbfp7 films demonstrates that this protein exhibits adhesive ability in aqueous conditions. While DOPA is critical for marine mussel adhesion, interfacial electrochemistry of freshwater adhesive plaques suggests that freshwater byssates circumvent catechol-based adhesion. The functional characterization of Dbfp7 as a freshwater mussel adhesive protein advances the understanding of fundamental requirements for biocompatible wet adhesion, a crucial step for the development of bioinspired wet adhesive materials, such as improved medical adhesives.