Stuck On Dopamine

Inspired by the chemistry that gives mussels their muscle, scientists at Northwestern University have developed a surface coating that sticks to almost anything (Science 2007, 318, 426). The adhesive proteins that give mussels their clinging power are rich in lysine and 3,4-dihydroxy-l-phenylalanine. Phillip B. Messersmith and colleagues hypothesized that dopamine, a small molecule containing the key functional groups in these residues—a primary amine and a catechol—might also have versatile adhesive properties. They found that in alkaline aqueous solution dopamine polymerizes to create a coating that adheres to virtually all types of surfaces, including noble metals, semiconductors, ceramics, and fluorinated polymers. Although Messersmith is unsure of the polymerization mechanism, he suspects the catechol is oxidized to a quinone, followed by a polymerization that's reminiscent of melanin formation. The polydopamine coating provides a platform for a variety of secondary reactions, which can further functionalize the coated object. Messersmith's group has used the technique to create metal films, bioactive surfaces, and self-assembled monolayers.