Tissue Engineering Scaffolds from Proteins in Disposed Bombyx mori Silkworm Pupae

Both animal and plant proteins are preferred for biomedical applications due their biocompatibility and ability to be converted into different shapes and sizes. In addition, proteins have various functional groups that provide the ability to carry different biological entities required for various diagnostics and treatments. The proteins in silk, namely, fibroin and sericin have been used for medical applications for centuries. Silk fibroin and sericin are obtained from the cocoons and the silkworms (pupae) are discarded as waste. The weight of pupae generated is roughly equivalent to the weight of the empty cocoons. Although pupae contain 30 to 40% proteins, 25–30% oil and about 30 to 40% carbohydrates, they currently have limited applications. In this study, we have extracted the proteins in the spent silkworm pupae using mild alkali. The extracted proteins were characterized for their composition and structure. The proteins were converted into films through solution casting and compression molding and the films obtained were studied for their chemical and physical properties. Biocompatibility of the films for tissue engineering and other medical applications and potential of the films to be used for food packaging was also studied. Proteins extracted from the pupae (SWP) have amino acid composition different than fibroin and sericin in silk fibers with glutamic acid (12.7%), glycine (9%) leucine, alanine and arginine (8%) being the major components. Compression molded films were marginally stronger (4.7–5.7 MPa) but solution cast films have considerably high elongation (up to 32%). Crosslinking with citric acid improved the strength and stability and made the films suitable for food and medical applications. Fibroblasts cells were able to attach and proliferate on the films suggesting that the films were biocompatible. Hence, spent pupae offer a low cost, renewable source for proteins and flexible options to develop value added biomaterials for medical applications and bioproducts for the food industry.