Numerous attempts have been made
to translate mussel adhesion to
diverse synthetic platforms. However, the translation remains largely
limited to the Dopa (3,4-dihydroxyphenylalanine) or catechol functionality,
which continues to raise concerns about Dopa’s inherent susceptibility
to oxidation. Mussels have evolved adaptations to stabilize Dopa against
oxidation. For example, in mussel foot protein 3 <i>slow</i> (mfp-3s, one of two electrophoretically distinct interfacial adhesive
proteins in mussel plaques), the high proportion of hydrophobic amino
acid residues in the flanking sequence around Dopa increases Dopa’s
oxidation potential. In this study, copolyampholytes, which combine
the catechol functionality with amphiphilic and ionic features of
mfp-3s, were synthesized and formulated as coacervates for adhesive
deposition on surfaces. The ratio of hydrophilic/hydrophobic as well
as cationic/anionic units was varied in order to enhance coacervate
formation and wet adhesion properties. Aqueous solutions of two of
the four mfp-3s-inspired copolymers showed coacervate-like spherical
microdroplets (ϕ ≈ 1–5 μm at pH ∼4
(salt concentration ∼15 mM). The mfp-3s-mimetic copolymer was
stable to oxidation, formed coacervates that spread evenly over mica,
and strongly bonded to mica surfaces (pull-off strength: ∼17.0
mJ/m<sup>2</sup>). Increasing pH to 7 after coacervate deposition
at pH 4 doubled the bonding strength to ∼32.9 mJ/m<sup>2</sup> without oxidative cross-linking and is about 9 times higher than
native mfp-3s cohesion. This study expands the scope of translating
mussel adhesion from simple Dopa-functionalization to mimicking the
context of the local environment around Dopa
