Silk: Source, Chemistry, and Properties

Silk fiber, a natural protein-based fibrous material, can be sourced from either moths or spiders. The predominant source for commercial silk fiber production is the Bombyx mori moth, renowned for its exceptional strength properties. For nearly 5000 years, silkworm silk fibers have been integral to textile manufacturing. These fibers, spun by various insects and spiders, exhibit a unique combination of mechanical attributes, including high strength, extensibility, and compressibility. B. mori silk primarily comprises two key proteins: fibroin and sericin. Fibroin microfibrils are organized into filaments, constituting the core structure of silk fibers. During the spinning process, each worm’s salivary glands produce two fibroin filaments, which are subsequently enveloped by sericin—a hydrophilic and adhesive protein—to form the structural unit. This inherent biocompatibility has positioned silk as a fundamental material for constructing blood vessels, muscle ligaments, membranes, tissue walls, and more. This chapter centers on exploring the diverse sources and chemistry of silk-based proteins, as well as the critical properties that underscore silk’s significance as a pivotal biomaterial in drug delivery applications.