Structural characterization and functionalization of engineered spider silk films

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 FTIR-spectroscopy. 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 beta-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.