Polydopamine (PDA) was discovered in 2007 as a biomimetic solution for the underwater strong adhesion of mussels. Since then, the interest in using PDA as an intermediate layer for developing functional surfaces has grown exponentially, due to many favorable properties: simple deposition process, strong adhesion to virtually any substrate, biocompatibility, and chemical reactivity.
Despite the growing number of PDA applications, the exact mechanism by which it adheres so strongly to virtually any substrate is a fundamental challenge remained unsolved in the field. Conventional analytical techniques, including solid-state NMR applied on natural abundance samples, can give only global information, with no selectivity to the interactions between substrate and PDA molecular sites. In this context, the solution we propose here is to introduce local markers in PDA that can “report” about their interaction with the atoms at the substrate’s surface.
The idea is implemented by 2H/13C/15N isotopic labeling of each distinct chemical site in dopamine monomer (selective labeling): the selectively labelled monomers will be used to synthesize multiple PDA@substrate samples, of which investigation by ss-NMR will give information with atomic resolution. The proposed scheme is original, representing the first proposed experimental approach that can address the problem of PDA adhesion at the atomic level in a realistic way, thus going well beyond the current state of the art in the field.