Adhesion of Mussel Foot Protein Mefp-5 to Mica: An Underwater Superglue

Danner, Eric; Kan, Yajing; Hammer, Malte U.; Israelachvili, Jacob N.; Waite, J. Herbert

doi:10.1021/bi3002538

Cited by 212 publications

(252 citation statements)

References 40 publications

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“…The observed interfacial energies for mfp-1, mfp-3, and mfp-5 are typically B(0.1-10) Â 10 À3 J m À2 , which is 4-6 orders of magnitude smaller than the fracture energies we determined for intact mussel plaques. 28,29 This large discrepancy indicates the importance of supramolecular-level dissipative mechanisms within the mussel holdfast that substantially enhance its tenacity. The structural origins of these additional dissipative mechanisms are not yet known and will be the focus of further studies.…”

Section: Fracture Energymentioning

confidence: 99%

Dynamics of mussel plaque detachment

et al. 2015

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Mussels are well known for their ability to generate and maintain strong, long-lasting adhesive bonds under hostile conditions. Many prior studies attribute their adhesive strength to the strong chemical interactions between the holdfast and substrate. While chemical interactions are certainly important, adhesive performance is also determined by contact geometry, and understanding the coupling between chemical interactions and the plaque shape and mechanical properties is essential in deploying bioinspired strategies when engineering improved adhesives. To investigate how the shape and mechanical properties of the mussel's plaque contribute to its adhesive performance, we use a custom built load frame capable of fully characterizing the dynamics of the detachment. With this, we can pull on samples along any orientation, while at the same time measuring the resulting force and imaging the bulk deformations of the plaque as well as the holdfast-substrate interface where debonding occurs. We find that the force-induced yielding of the mussel plaque improves the bond strength by two orders of magnitude and that the holdfast shape improves bond strength by an additional order of magnitude as compared to other simple geometries. These results demonstrate that optimizing the contact geometry can play as important a role on adhesive performance as optimizing the chemical interactions as observed in other organisms and model systems.

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Section: Fracture Energymentioning

confidence: 99%

Dynamics of mussel plaque detachment

et al. 2015

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“…This mechanism may explain the unusually strong and reversible adhesion measured between two dopa-containing mfp-5 films under reducing conditions 29 . More critically, it shows how simply re-engineering the surface of polyacrylate-based biomaterials can result in superior bulk self-mending properties.…”

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confidence: 93%

“…Periodate stoichiometrically oxidizes catechol to quinone 29 , hence was used to perturb intermolecular hydrogen bonding between symmetric catecholic soft polymer films (Fig. 4).…”

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Surface-initiated self-healing of polymers in aqueous media

et al. 2014

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Polymeric materials that intrinsically heal at damage sites under wet or moist conditions are urgently needed for biomedical and environmental applications [1][2][3][4][5][6] . Although hydrogels with self-mending properties have been engineered by means of mussel-inspired metal-chelating catechol-functionalized polymer networks 7-10 , biological self-healing in wet conditions, as occurs in self-assembled holdfast proteins in mussels and other marine organisms 11,12 , is generally thought to involve more than reversible metal chelates. Here we demonstrate self-mending in metal-free water of synthetic polyacrylate and polymethacrylate materials that are surface-functionalized with mussel-inspired catechols. Wet self-mending of scission in these polymers is initiated and accelerated by hydrogen bonding between interfacial catechol moieties, and consolidated by the recruitment of other non-covalent interactions contributed by subsurface moieties. The repaired and pristine samples show similar mechanical properties, suggesting that the triggering of complete self-healing is enabled underwater by the formation of extensive catechol-mediated interfacial hydrogen bonds.All polymeric materials suffer damage in the course of their functional lifetimes. Few, if any, completely heal at damage sites. Despite recent progress in the design of self-mending polymeric materials based on crack-activated crosslinking 1 , light 2 , heat 3 or other external stimuli 4 , these remain less than perfectly healed, and, in the case of polymers in wet environments, self-healing technologies are even more limited than those engineered for dry conditions. Mussel adhesive holdfasts exhibit significant self-healing capabilities 11,12 , although the molecular mechanisms involved are poorly understood. Notwithstanding this, the selfmending adhesion and cohesion of isolated dopa (3,4-dihydroxyphenyl-L-alanine)-containing adhesive proteins were shown to rely critically on maintaining dopa in an acidic and reducing environment 13,14 . Significantly different conditions are required to recapitulate the self-healing cohesion of tris-dopa-Fe 3+ -mediated complexes in proteins and polymers [7][8][9]15 . Such results increasingly suggest the importance of dopa, but also its subtle and diverse interfacial reactivity vis-à-vis the traditional and still widely held view that dopa, and catechols generally, function primarily as crosslinkers after their 2-electron oxidation to quinones 16 . To better assess the contribution of catechol to polymer selfhealing in a reducing (pH 3), metal-free wet environment, we prepared a material from common, water-insoluble synthetic acrylic polymers having a catechol-functionalized surface. These materials are completely self-healing in a process initiated by catecholmediated interfacial hydrogen bonding, and consolidated by followup interactions (for example, hydrophobic and steric) after a brief compression (∼6 × 10 4 Pa). The crucial and robust roles played by

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“…The cohesion of the films adsorbed and measured at pH 4 (17.0 ± 2.5 mJ/m 2 , t c independent) surpassed the maxima of mfp-5 (13.7 ± 0.5 mJ/m 2 , t c ≥ 1 h), the most adhesive protein tested. 15 Interaction energy between P2 films on mica, measured at pH 4 (black), pH 3 (red), and pH 7 (green), respectively, after adsorption at pH 4.…”

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Microphase Behavior and Enhanced Wet-Cohesion of Synthetic Copolyampholytes Inspired by a Mussel Foot Protein

Seo¹,

Das²,

Zalicki³

et al. 2015

J. Am. Chem. Soc.

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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. M arine mussels (Figure 1a) attach to hard surfaces, e.g., mineral and metal, in the intertidal zone where waves with and without suspended sand often exceed 25 m/sec velocities. 3,4-Dihydroxyphenylalanine (Dopa), a main constituent in mussel foot proteins (mfps) and substantially contributing to wet adhesion, has been incorporated in synthetic polymers to mimic the bio wet-adhesion. 1−5 However, other constitutional features of mfps, e.g., cationic residues (lysine, K), anionic residues (aspartic acid, D), nonionic polar residues (asparagine, N), and nonpolar residues (alanine, A), have not typically been included in mussel-inspired synthetic wet-adhesion systems. 1,2Here, we studied the microphase behavior and wet-adhesion of copolyampholytes with fixed catechol content and varied other key functionalities. Potential effects of aromatic moieties (Tyr, Trp) besides Dopa in mfp-3s have not been specifically tested in the present structural design of the model copolyampholytes. Conditions for the experiments were adjusted according to the microenvironmental conditions of adhesive protein deposition under the mussel's foot including acidic to neutral pH and ionic strength of ≤100 mM. 3,4 In mussel adhesion, polyelectrolyte adhesive proteins or mfps are presented to target surfaces after being condensed as a dense fluid by complex coacervation, a critical ste...

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Adhesion of Mussel Foot Protein Mefp-5 to Mica: An Underwater Superglue

Cited by 212 publications

References 40 publications

Dynamics of mussel plaque detachment

Dynamics of mussel plaque detachment

Surface-initiated self-healing of polymers in aqueous media

Microphase Behavior and Enhanced Wet-Cohesion of Synthetic Copolyampholytes Inspired by a Mussel Foot Protein

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