Novel Silk Materials from Unique Silkworm Varieties

Abstract

Herein, we have introduced two novel silk materials, developed using unique silkworm varieties. A silkworm variety, “Sericin Hope” was reared using conventional breeding techniques. Sericin Hope produces thin cocoons made exclusively of sericin, a family of hydrophilic glue-like silk proteins. Native sericin is easily extracted from these cocoons, and can be used to create self-standing pure protein materials, such as films and hydrogels. These materials can be used in cosmetics, cell culture, and tissue regeneration. Transgenic techniques were used to generate novel silkworm varieties with unique characteristics, which cannot be produced by conventional breeding. The ability to use synthetic amino acids during protein biosynthesis was endowed upon silkworms, using a transgenic technique. Consequently, an azido-bearing synthetic amino acid, 4-azidophenylalanine (AzPhe) was successfully incorporated during protein synthesis, to produce AzPhe-incorporated silk fibroin. Azido groups in the AzPhe-incorporated silk fibroin or “clickable silk” can be selectively modified by click reactions. Cell culture substrates, whose cell adhesive properties can be controlled by light, were developed using clickable silk. Spatial patterning of mouse fibroblasts was achieved using this technique.