Ultrasonication and genipin cross-linking to prepare novel silk fibroin-gelatin composite hydrogel

Hydrogels are highly desirable tissue engineering scaffolds due to their high water content and structural similarity to a natural extra cellular matrix. However, the extensive use of hydrogels is limited by their low strength and facile degradation. By combining mechanical integrity and slow degradation of silk fibroin with excellent bioactivity of gelatin, a novel biocompatible protein-based composite hydrogel of silk fibroin and gelatin was developed. The gelation of silk fibroin aqueous solution was accelerated by ultrasonication, and gelatin derived from porcine skin was immobilized into the hydrogel network by the silk fibroin β-sheets. After that, genipin was used to post-cross-link the hydrogel to form a compact and stable hydrogel network. This hydrogel composite was a mechanically robust biomaterial with predictable long-term degradation characteristics. MG63 cells readily attached, spread, and proliferated on the surface of the hydrogels as demonstrated by fluorescein diacetate/propidium iodide staining and mitochondrial activity (3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyl tetrazolium bromide) assay. Furthermore, the physicochemical and biological properties of hydrogel were fine-tunable by altering the ratio of silk fibroin and gelatin. The silk fibroin/gelatin composite hydrogels are anticipated to have the potential as cartilage or non-load-bearing bone tissue engineering and regeneration.