Hydrogen-bonded Multilayers of Silk Fibroin: From Coatings to Cell-mimicking Shaped Microcontainers.

We present a novel type of all-aqueous non-ionic layer-by-layer films of silk fibroin with synthetic macromolecules and a natural polyphenol. We found the multilayer growth and stability to be strongly pH-dependent. Silk assembled with poly(methacrylic) and tannic acids at pH=3.5 disintegrated at pH~5; while silk/poly(N-vinylcaprolactam) interactions were stable at low and high pH values but resulting in thinner films at high pH. The results suggest that the intermolecular interactions are primary driven by hydrogen bonding with a considerable contribution of hydrophobic forces. We also demonstrated that cubical, spherical and platelet capsules with silk-containing walls can be constructed using particulate sacrificial templates. This work sets a foundation for future explorations of natural and synthetic macromolecules assemblies as biomimetic materials with tunable properties.