Toward Artificial Mussel‐Glue Proteins: Differentiating Sequence Modules for Adhesion and Switchable Cohesion

Abstract

Artificial mussel-glue proteins with pH-triggered cohesion control were synthesized by extending the tyrosinase activated polymerization of peptides to sequences with specific modules for cohesion control. The high propensity of these sequence sections to adopt b-sheets is suppressed by switch defects. This allows enzymatic activation and polymerization to proceed undisturbed. The b-sheet formation is regained after polymerization by changing the pH from 5.5 to 6.8, thereby triggering O!N acyl transfer rearrangements that activate the cohesion mechanism. The resulting artificial mussel glue proteins exhibit rapid adsorption on alumina surfaces. The coatings resist harsh hypersaline conditions, and reach remarkable adhesive energies of 2.64 mJ m À2 on silica at pH 6.8. In in situ switch experiments, the minor pH change increases the adhesive properties of a coating by 300 % and nanoindentation confirms the cohesion mechanism to improve bulk stiffness by around 200 %. Water-based wet adhesives, that tolerate hostile conditions are of high interest as they promise resistant under water glues, surgical sealants as well as biofriendly dyes, anti-fouling or anti-corrosive coatings. [1, 2] One of the most prominent

A Superstrong and Reversible Ionic Crystal‐Based Adhesive Inspired by Ice Adhesion

“…In the last two decades,the adhesion mechanics of ice have focused on the direct electrostatic interaction and van der Waals force. [2a, 3] Further,traditional reversible adhesives can be fabricated from stimuli-responsive polymers (e.g.t emperature or light isomerization groups), [1a,c,d, 4] dynamic covalent bonds (e.g., Diels-Alder reaction, disulfide bonds), [5] phase or topology transitions [1d, 6] and reversible non-covalent interactions (e.g., hydrogen bonds and host-gust interactions). [4b,5c, 7] Fori nstance,gecko-inspired reversible adhesive suggests that welldesigned micro/nanoscale fibril structures are ap owerful factor to induce the van der Waals interaction with the substrate.…”