Strong, elastic and degradation-tolerated hydrogels composed of chitosan, silk fibroin and bioglass nanoparticles with factor-bestowed activity for bone tissue engineering

Polymer hydrogels intended for use in bone repair need to be strong, elastic, and capable of enduring degradation. However, many natural polymer hydrogels lack these essential properties and thus, are unsuitable for bone repair applications. Here, a new type of multi-network hydrogel with improved mechanical and degradation-resistant properties has been developed for use in bone repair. The hydrogel is composed of thiolated chitosan (TCH), silk fibroin (SF), and thiolated bioglass (TBG) nanoparticles (NPs). The multi-networks are built through sulfhydryl self-crosslinking, diepoxide crosslinker-involved linkages of amino or hydroxyl groups, and enzyme-mediated phenol hydroxyl crosslinking. Additionally, mesoporous TBG NPs serve as a vehicle for loading stromal cell-derived factor-1 (SDF-1) to provide the gel with cell-recruiting activity. The formulated TCH/SF/TBG hydrogels exhibit remarkably enhanced strength, elasticity, and improved degradation tolerance compared to some gels made from only TCH or SF. Furthermore, TCH/SF/TBG gels can support the growth of seeded cells and the deposition of matrix components. Some TCH/SF/TBG gels also demonstrate the ability to release SDF-1 in an approximately linear manner for a few weeks while retaining the chemotactic properties of the released SDF-1. Overall, the multi-network hydrogel has the potential as an in situ forming material for cellrecruiting bone repair and regeneration.