Chapter 5 - Inspiration from Natural Silks and Their Proteins

Abstract

Abstract Natural silks show remarkable mechanical properties, for example, high strength and toughness, despite being spun from aqueous solution by insects and spiders under mild ambient conditions. The excellent properties of silks result from their hierarchical organized structure which is expressed in the alternate crystal and amorphous sequence elements in the molecular chain of silk proteins. This chapter reviews the structure of the various silks, but with focus on silkworm silk and spider dragline (major ampullate silk). Subsequently, the relationship between mechanical properties and structure is discussed. Understanding the mechanism of the natural spinning and the factors affecting the properties of silk allows control of the properties of materials based on silk proteins in general and in particular those of artificial silks spun from regenerated as well as recombinant silk proteins. Besides the excellent mechanical properties, silks and silk proteins also have attractive biomedical properties, namely biocompatibility and biodegradability in combination with interesting physicochemical properties. The ongoing efforts for using silk proteins in artificial spinning, biomedicine, and bioengineering are reviewed. In addition, it has been found that the amino acid sequencing and secondary structure of silk proteins is quite similar to the silk-like protein active in the biomineralization process of mollusk. Accordingly, silk proteins have important potential in regulating inorganic crystal growth and producing high-performance organic/inorganic hybrid materials. For instance, inducing hydroxyl apatite deposition on silk-protein-based material creates a novel composite applicable in bone regeneration and repair.