Robust polydopamine nano/microcapsules and their loading and release behavior.

Polydopamine (Pdop) nano/microcapsules are readily produced through the oxidative polymerization of dopamine and the spontaneous deposition of Pdop on the template surface, followed by the removal of the template. The Pdop capsules are very robust and stable under different pH. Most importantly, they exhibit outstanding unidirectional permeability to Rh6G: they can uptake Rh6G but cannot release Rh6G in an aqueous buffer solution. In contrast, in ethanol, the trend is reversed: they cannot uptake but rapidly release Rh6G.