Multifunctional coatings hinging on the catechol/amine interplay

Design and implementation of functional coatings is a topic of active research in a variety of health-related applications, most of which require wet adhesion. The powerful wet adhesion of mussel byssus proteins rich in DOPA and lysine residues provided a clue to realize that the combination of a catechol and an amine component has a specific role in the interfacial adhesion. From this natural model, polydopamine (PDA)-based coatings have been developed that result from the oxidative polymerization of dopamine combining the catechol and amine functionalities in the same molecule. Covalent interactions resulting from Michael-type addition or Schiff-base formation of the polymeric products from dopamine oxidation as well as non-covalent pi-stacking and cation-pi interactions exemplify the diverse mode of catechol/amine interplay that have been identified as responsible of the adhesion and cohesion properties of PDA. In the last decade coatings inspired to the same chemistry but using different starting materials have been explored particularly catechols of natural origin and different amine components, while mechanistic studies with model compounds have allowed to rationalize the structural requirements for adhesion and to expand the potential of these functional coatings. Inspired by the dopa/lysine rich mussel proteins featuring unique wet adhesive properties, functional coatings based on catechol and amine components represent versatile systems with applications in biomedical and other fields. The adhesive properties hinge on covalent and non-covalent interactions of the catechol/o-quinone and the amine counterpart as evidenced in both polydopamine and other coatings based on separate catechol and amine components.image