Mulberry silk, spider dragline and recombinant silks

Silks stand out among the natural fibres Consisting primarily of highly structured proteins, they exhibit a wide range of different properties, from high tensile strength to extreme extensibility and from chemical resistance to bioactivity In some of their properties, specifically in toughness and biocompatibility, silks can easily outperform most natural and synthetic fibres. Silk materials will be able to combine 5000-year-old, traditional techniques of agriculture with modern biotechnology and material design in a truly unique way. Tables shows selected silk producing species the name of their silk if commercially available and their diet and grade of domestication as well as tensile properties of selected man-made and natural fibres. It will be reviewed here first, starting with the structure and properties of the material mulberry silk and nephila dragline silk, followed by its production and finally its processing and applications as biomaterial. The potential and attraction of recombinant (regenerated) silks is undisputable. It is of course difficult to judge the potential of such a young field of technology. However, considenng that regenerated, recombinant and natural silks can be used in cell culture applications and that the US cell culture market alone was USD 714.5 million in 2005, an economic impact of some hundreds of millions should be expected. Other fields also stand to benefit from the outstanding mechanical properties found in silks. From highperformance textiles, impact protection foils and composite materials to rope safety-cores, nanotechnology and even cryotechnology - the potential for silk materials has yet to be realised. One thing is certain: the success of future silk materials will depend firmly on the development of practical fibre formation and re-formation processes.