Dissolution of Antheraea yamamai silkworm cocoon was carried out in various solvent systems with various dissolving conditions including dissolution salts, salt concentration, dissolving temperature, and time. General chaotropic salt for Bombyx mori silk fibroin does not work for A. yamamai silkworm cocoon. Lithium bromide 9.3 M at 100 o C also does not work to dissolve wild silkworm cocoon. However, 9 M of lithium thiocyanate treatment at 100 o C induced 100% dissolution of wild silkworm cocoon. But it could not be dissolved lower than 60 o C. Like lithium thiocyanate, less than 60 o C treatment with molten calcium nitrate 4 hydrate could not dissolve wild silkworm cocoon. As the dissolution temperature increased up to 100 o C, the solubility of wild one was reached over 90%. SDS-PAGE showed broad tailing stream pattern that means the molecule of wild silk was depolymerized with dissolution temperature and time. From the above results, the best chaotropic salt for A.yamamai silkworm cocoon is calcium nitrate 4 hydrate.
IntroductionSilk is classified into two general groups: domestic (Bombyx mori) and wild type (Antheraea yamamai, etc) (Kweon and Park, 1994). The general characteristics of A.yamamai silkworm silk were studied by my research group (Lee et al., 2015;Kweon and Park, 1994). A.yamamai silk fiber has been used as a valuable textile fiber due to unique luster and color for more than 4,000 years. Recently, silk polymer has been revealed several advantages for biological materials due to its blood compatibility, oxygen permeability, and so on (Sakabe et al., 1989;Minoura et al., 1990). Silk polymer has been studied for various applications such as cosmetics, suture and artificial eardrum (Kundu et al., 2013;Ju et al., 2014;Vepari and Kaplan, 2007;Kim et al., 2010), and so on. The reason why B.mori silk examined as possible biomaterials is that we know how to dissolve it and reshape it for the application. In the case of A.yamamai silk, it is known to have an arg-gly-asp tripeptide sequence (Ruoslahti and Pierschbacher, 1986, Minoura et al., 1995). Biocompatibility (Wang et al., 2011), gelation (Liu andZhang, 2014), degradation (You et al., 2014) and PEG modified film (Wei et al., 2014) using A.yamamai silk protein have been investigated.Until now there is no good solvent for silk materials because silk fibroin behaves like a thermoset polymer after solidification through spinning process. The only way to dissolve silk materials is concentrated chaotropic salts, which destabilize silk protein in solution and increase the solubility of fibroin (Kweon, 1998