Silk

Abstract

Silks are naturally spun fibrous proteins most often associated with silkworms and spiders. Silk fibers are unusual in combining strength, toughness, and resistance to mechanical compression. The proteins are characterized by a β‐sheet secondary structure for the highly crystalline regions, as well as regions of lower crystallinity. Silkworm cocoon fibers have been used in textiles for thousands of years. Silk production by spiders has not been domesticated to date. Water‐soluble silk proteins are synthesized and stored in glands until spun into fibers, via micellar and gel states, at which point they become insoluble in water upon spinning. The silk spinning process is regulated by the organism and involves the extrusion of the silk gel in a liquid crystalline state through spinnerettes. Silk fibers are mechanically stable to approximately 200°C. Membranes, hydrogels, fibers, and foams have been formed from reconstituted silks that provide useful means to explore structure development, to entrap enzymes, and for use as biomaterial scaffolds such as for tissue engineering. Worldwide production of silkworm silk for textiles is expected to increase, and future applications will depend on biotechnological approaches to generate suitable levels of specifically tailored silk compositions.