A novel strontium-loaded silk fibroin nanofibrous membrane for guided bone regeneration: in vitro and in vivo studies

The silk fibroin (SF) nanofibrous membrane is a good candidate for clinical application in bone and periodontal regenerative therapy. Strontium (Sr), as a natural element in human bone, can hinder osteoclast activity and promote bone formation. This study aims to evaluate in vitro and in vivo the feasibility of strontium-loaded silk fibroin nanofibrous membrane (Sr-SFM) for guided bone regeneration (GBR). The Sr-SFM was fabricated by electrospinning, and the structure characteristics and strontium ion release pattern were analyzed. To examine the biocompatibility of Sr-SFM, we investigated cell morphology, proliferation and differentiation. The GBR efficacy of Sr-SFM was evaluated in rat calvarial defects. The Sr-SFM exhibited uniform nanofibrous structure and a sustained release of strontium over a 14-day period. In vitro tests, the cell numbers and ALP activities of rBMSCs cultured in Sr-SFMs were significantly higher than that in pure SFM. In vivo test at 6 weeks, both micro-CT and histological analyses showed that the Sr-SFM group got significantly greater bone formation than pure SFM or uncovered groups. In conclusion, the Sr-SFMs developed in this study showed long-term release of Sr2+, improved cell proliferation and osteogenic differentiation of hMSCs in vitro, and increased new bone formation in vivo, strongly suggesting their potential application towards GBR.