Enhancing the Gelation and Bioactivity of Injectable Silk Fibroin Hydrogel with Laponite Nanoplatelets

Regenerated silk fibroin (RSF) of Bombyx mori silk fiber is a promising natural material for bone defect repair. However, a lack of specific integrin and growth factor for osteoinduction significantly hinders its application in this area. In this study, the role of Laponite nanoplatelet (LAP), a bioactive clay that can promote osteoblast growth, in the formation of RSF hydrogel, as well as the various properties of RSF/LAP hybrid hydrogel, was closely investigated. The results indicate that LAP could serve as a medium to accelerate hydrophobic interaction among the RSF molecules and a disruptor to limit the growth of β-sheet domain during the gelation of RSF. Rheological measurement suggests that the RSF/LAP hydrogel is injectable as it displays thixotropy in the room temperature. Proliferation and differentiation results of the primary osteoblasts encapsulated in hydrogel show that RSF/LAP hydrogel can promote the cell proliferation and enhance the osteogenic differentiation. The transcript levels for alkaline phosphatase, osteocalcin, osteopontin, and collagen type I osteogenic markers obviously improve with RSF/LAP hydrogel compared to the controls at 14 days, especially with the higher contents of LAP. Overall, the results suggest that the RSF/LAP hydrogel have great potential to be utilized as an injectable biomaterial for irregular bone defect repair.