No abstract

The engineered spider silk protein eADF4(C16) reveals similarities to amphiphilic block copolymers. Drop cast of protein solutions on different hydrophobic as well as hydrophilic templates out of different starting solvents (hexafluoroisopropanol, formic acid and aqueous buffers) generated silk films varying in structure and surface properties. Here, the underlying secondary structure of the proteins, the mechanical integrity at increased temperatures, homogeneity and surface topography of silk films, as well as the wettability were investigated in detail. Interestingly, the used templates had impact on microphase separation of the silk molecules as seen by the content of b-sheet structures; as well as on silk film surface hydrophobicities.

Due to their biocompatibility, their extraordinary mechanical properties and the ability to be processed into various shapes, natural polymers like spider silk proteins are promising candidates for materials' applications. However, for many applications, additional specific functionalization is necessary. Here, we present recombinantly produced engineered spider silk proteins based on one dragline silk component of the European garden spider Araneus diadematus. The proteins have been engineered in order to incorporate cysteine which allows site-specific functionalization. These cysteine containing variant silk proteins are characterized in terms of structure, assembly and chemical reactivity in solution. Further, films composed of these proteins were structurally investigated by CD-and FTIRspectroscopy. Comparison of the variants with the original cysteine-free silk protein revealed no apparent differences in solution and in the films. Functionalization of the thiol groups of these silk protein-based films with molecules such as nanogold, dyes, biotin and b-galactosidase demonstrates the potential of such films for a broad range of applications which opens up new possibilities in materials research based on silk polymers.

The performance of biomaterials largely depends on the materials biocompatibility, which is directly related to unwanted side effects like foreign body responses and inflammation, and the potential of interaction of cells with its surface, for example, cell adhesion. In the distinct application of catheters, low or even no cell adhesion is eligible. To influence the properties of existing and commonly used biomaterials and to further increase their biocompatibility, a coating with a recombinantly produced spider silk protein as outer layer was applied on three selected catheter polymers (polyurethane, polytetrafluoroethylene, silicone) and evaluated based on cell adhesion. The tested cell types, HaCaT keratinocytes (epidermal cells), B50 neuronal cells, C2C12 myoblasts (muscle cells) and BALB/3T3 fibroblasts (connective tissue), exhibited low or no adhesion on the silk-coated materials. In combination with the lack of toxicity, the good biocompatibility, and the low body response, it could be shown that silk coatings have a high potential as a biomedical coating material, e.g., for catheters.