Silk hydrogels from non-mulberry and mulberry silkworm cocoons processed with ionic liquids

Matrices based on silk fibroin from the non-mulberry silkworm Antheraea mylitta and the mulberry silkworm Bombyx mori have demonstrated good applicability in regenerative medicine. However, the cocoons of A. mylitta are underutilized in part due to their lack of solubility in traditional organic solvents. Therefore, the present work investigates the solubilization and processing of degummed fibers obtained from the cocoons of both silkworm species into hydrogels using ionic liquids (ILs). The developed hydrogels exhibited a rubbery consistency, viscoelastic behavior and rapid degradation in the presence of protease XIV. Scanning electron and confocal microscopy images suggest that human adipose stem cells (hASCs) are able to adhere to and migrate at different levels within the hydrogel structures. Moreover, the MTS assay demonstrated the maintenance of cell metabolic activity for up to 28days, while DNA quantification showed that hASCs were able to proliferate on the seeded hydrogels. The findings indicate that complete IL removal from the fabricated hydrogels results in a positive hASCs cellular response. Thus the present approach provides a unique opportunity to broaden the processability and application of silk fibroin obtained from A. mylitta cocoons for regenerative medicine, namely cartilage regeneration.

The authors acknowledge financial support from the Portuguese Foundation for Science and Technology (Grants SFRH/BPD/45307/2008 and SFRH/BD/64070/2009), the Fundo Social Europeu, and the Programa Diferencial de Potencial Humano. This work was partially supported by the FEDER through POCTEP 0330_IBERO-MARE_1_P and also by the Department of Biotechnology, Government of India. S.C.K. is grateful to R.L.R. and S.S.S. for their excellent hospitality during his stay at the 3B's laboratory, Guimaraes, Portugal. R.L.R. also offers his sincere thanks to S.C.K. for providing hospitality during his short visits to his laboratory in the Indian Institute of Technology, Kharagpur.