Silk fibroin-based injectable hydrogels as instructive milieu for tissue regeneration

Hydrogels produced by starting from natural-derived polymers, have become especially attractive in the field of tissue engineering for regenerating a wide variety of tissues and organs. Biologically inspired materials has become an increasingly widespread strategy towards innovative approaches in tissue engineering and regenerative medicine, because nature can provide a powerful set of “smart” material with hierarchical organization, specific bioactivity, and self-assembling capability in response to environmental stimuli. Silk fibroin is a good example of a natural biopolymer for its molecular and supra-molecular structure, its bio recognition due to molecular ligands, and it’s ability to self-assemble depending on the process and on the specific work-environment. Fibroin can be processed by various techniques to obtain different structures with unique properties in terms of crosstalk ability with the system biological environment. Silk fibroin-based hydrogel physically cross-linked and chemically stabilized, were prepared and evaluated as a 3D instructive biological milieu for tissue regeneration field. Fibroin-based gels can be prepared by treating fibroin solutions with acids, with thermal treatments or addition of electrolytes to the fibroin solution, via shear stresses or sonication and, as recently reported, by supercritical carbon dioxide. Hydrogels have been validated in the last years in vitro and in vivo for the reconstruction of bone, and cartilage. More recently, fibroin was conjugated with IKVAV peptide to improve the specific bioactivity for stem cells-based brain tissue regeneration, and gelation was induced by ultrasound treatment. The lecture will review structure-composition processing-dependent, and different biological outcome of fibroin-based hydrogels. In particular, the presentation will focus on a new potential application in the brain tissue regeneration. Results obtained by in vitro culturing encapsulated human neural stem cells (hNSC) and endothelial cells (OEC) isolated from human peripheral blood in co-culture system with human bone morrow-derived mesenchymal stem cells (MSC) will be discussed.