Formulation of poorly water-soluble substances using self-assembling spider silk protein

In nature self-assembly of soluble monomeric proteins to defined supramolecular structures is an essential process in the formation of morphologically distinct biological materials like cells, tissues, diatoms or mollusk shells. Using these proteins, complex structures in the nanometer and micrometer scale can be generated that are hardly obtainable by other methods. The engineered ADF4(C16) spider silk protein is mimicking the sequence of the dragline silk protein ADF4 of the spider Araneus diadematus and can be synthesized by a biotechnological production process using Escherichia coli (E. coli) as host organism. From the soluble ADF4(C16) monomers assembly of nanofibers, microbeads and films is possible. The purified monomeric ADF4(C16) strongly interacts with hydrophobic surfaces and particles of poorly water-soluble substances. Based on this effect ADF4(C16) could be used for colloidal stabilization of hydrophobic particles in aqueous environment. Poorly water-soluble substances can also be encapsulated in ADF4(C16) microbeads during self-assembly. The release of the encapsulated ingredients was induced by proteolytic cleavage of the microbead structure. These results show that ADF4(C16) protein microbeads have a high potential as a storage and delivery system for poorly water-soluble active ingredients in several application fields like cosmetics, pharma or nutrition.