4 research outputs found
Microphase Behavior and Enhanced Wet-Cohesion of Synthetic Copolyampholytes Inspired by a Mussel Foot Protein
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Microphase Behavior and Enhanced Wet-Cohesion of Synthetic Copolyampholytes Inspired by a Mussel Foot Protein.
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 slow (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(2)). Increasing pH to 7 after coacervate deposition at pH 4 doubled the bonding strength to ∼32.9 mJ/m(2) 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
Recommended from our members
Microphase Behavior and Enhanced Wet-Cohesion of Synthetic Copolyampholytes Inspired by a Mussel Foot Protein
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
Marine Bioinspired Underwater Contact Adhesion
Marine
mussels and barnacles are sessile biofouling organisms that
adhere to a number of surfaces in wet environments and maintain remarkably
strong bonds. Previous synthetic approaches to mimic biological wet
adhesive properties have focused mainly on the catechol moiety, present
in mussel foot proteins (mfps), and especially rich in the interfacial
mfps, for example, mfp-3 and -5, found at the interface between the
mussel plaque and substrate. Barnacles, however, do not use Dopa for
their wet adhesion, but are instead rich in noncatecholic aromatic
residues. Due to this anomaly, we were intrigued to study the initial
contact adhesion properties of copolymerized acrylate films containing
the key functionalities of barnacle cement proteins and interfacial
mfps, for example, aromatic (catecholic or noncatecholic), cationic,
anionic, and nonpolar residues. The initial wet contact adhesion of
the copolymers was measured using a probe tack testing apparatus with
a flat-punch contact geometry. The wet contact adhesion of an optimized,
bioinspired copolymer film was ∼15.0 N/cm<sup>2</sup> in deionized
water and ∼9.0 N/cm<sup>2</sup> in artificial seawater, up
to 150 times greater than commercial pressure-sensitive adhesive (PSA)
tapes (∼0.1 N/cm<sup>2</sup>). Furthermore, maximum wet contact
adhesion was obtained at ∼pH 7, suggesting viability for biomedical
applications