Formation of polydopamine nanofibers with the aid of folic acid.

Polydopamine (PDA) generated by the oxidative self-polymerization of dopamine shows great potential for surface modification. Observed PDA nanostructures are nanoparticles and thin films. The formation mechanism of PDA is still unclear; thus, the manipulation of PDA nanostructures is a big challenge. In this study, we first demonstrated that folic acid shows a dramatic effect on the PDA nanostructure: New aggregated nanostructures of PDA, nanobelts and nanofibers, were generated in a dopamine/folic acid system. We hypothesized that folic acid may be involved in the stacking of protomolecules of PDA by π-π interactions and hydrogen bonding. Herein we describe the first experimental strategy to manipulate the aggregation of PDA by using small molecules. This study not only provides a new method for generating PDA nanofibers, which are proposed bioorganic electronic materials, but also a possible way to understand the formation mechanism of PDA and its analogues in nature, melanins.