Polymerizable biomimetic vesicles with controlled local presentation of adhesive functional DOPA groups.

Inspired by strong adhesive properties of mussel footprint proteins, which are largely governed by the presence of dihydroxy-phenylalanine (DOPA) amino acid moieties, we present a novel approach for presenting DOPA groups in a very defined way in order to modulate the adhesion between artificial interfaces. To this end, linear peptide amphiphiles are synthesized with attached DOPA functional groups and a polymerizable diacetylenic tail. The obtained amphiphiles can be coassembled with matrix amphiphiles into vesicles, which can be subsequently stabilized through UV-light-induced solid-state polymerization. Depending on the molar ratio of matrix and adhesive amphiphiles, the vesicles self-assemble into spherical, fibrilar, or planar nanostructures. The adhesive properties of the surface-adsorbed vesicles are evaluated by drop casting them onto a planar solid substrate and performing macroscopic shear tests in contact with a similar substrate. The shear forces are investigated as a function of substrate chemistry, vesicle polymerization conditions, vesicle concentration, and number of adhesive DOPA groups in the interface. Substrate adhesion is enhanced by surface-confined vesicles and greatly depends on the presentation of DOPA groups in the adhesive interface, either as a mono- or multilayer conformation. Because the adhesive structures can be transferred onto substrates from low-viscosity aqueous solution, they may serve as interesting nanoscale gluing pads in future applications, where the high viscosity of polymer-based glues renders the controlled formation of nanoscale adhesion pads difficult.