Study of nanostructured fibroin/dextran matrixes for controlled protein release.

• Dextran sulphate (DSS) forms nano- and microdomains in silk fibroin (SF) films. • DSS domains act as active porogens upon incubation in aqueous media. • The presence of DSS induces the formation of beta sheet crystals in SF. • Protein release kinetics can be tuned by selecting different SF/DSS compositions. • SF/DSS blends represent a flexible system for sustained protein delivery. Microporous films are structures with attractive features as high porosity and high intrinsic surface area. Unfortunately, most biocompatible materials useful for the preparation of such microporous films are suboptimal for drug delivery due to poor processability and/or drug encapsulation properties. Silk fibroin (SF) is a biocompatible protein with good drug release properties and suitable characteristics for pharmaceutical processing. Dextran sulphate (DSS) is an anionic polysaccharide with the capacity to interact and stabilize many proteins. In the current study, we evaluate the effect of DSS on the physical properties of SF/DSS blend films, how it affects the molecular and microscopic structure of the system and its capacity for providing controlled release of a model protein. Using this system, micro- and nanostructured films could be prepared through a green, water-only process. It was found that DSS acted both as a modifier of SF secondary structure and as a functional porogen, where the size of nano- and micropores varied with the blending ratios. High ratios showed higher swelling, porosity and crystallinity, resulting in modified protein release kinetics, as compared to pure SF films. Considering both their mild preparation method and their physical and pharmaceutical properties, SF/DSS films stand out as ideal systems for sustained protein delivery applications. [ABSTRACT FROM AUTHOR]