Mechanical Enhancement of Silk Fibroin Hydrogel Generated From Genetically-Modified Bombyx mori Cocoons and Promotes Osteogenesis.

Regenerated silk fibroin (RSF) from Bombyx mori is well known for its outstanding biocompatibility, biodegradability, and mechanical characteristics. Spider silk has even better strength and extensibility and is considered one of the best silk fibers in nature. Silkworm fibroin heavy chain in fibroin and major ampullate spidroin-1 in spider silk from the spider Nephila clavipes share similar molecular weight and repetitive structure, which makes the genetic modification of silkworms possible. In our study, a novel hydrogel generated from genetically modified Bombyx mori cocoons was characterized and evaluated for potential clinical application. For the crosslinking of the hydrogel, horseradish peroxidase and H2O2 were added to the RSF solution to create a double crosslinking structure. As a result, genetically modified regenerated silk fibroin (GMRSF) hydrogels exhibited better mechanical characteristics compared with RSF hydrogels. Additionally, compared with RSF hydrogels, GMRSF hydrogels exhibited stronger osteogenic differentiation function on rat bone mesenchymal stem cells (BMSCs). In vivo, GMRSF hydrogel also showed better osteogenic differentiation function. While the mechanism behind this remains unclear, the outstanding osteogenesis ability of GMRSF sheds light on applications in orthopaedic diseases in the future such as bone defects.