4 0 braided absorbable sutures

C57BL/6J mice were divided into three groups randomly. Animals were anaesthetized with 2% inhalation of isofluorane. A linear scalp incision was made from the nasal bone to the occiput, and full-thickness flaps were elevated. The periosteum overlying the calvarial bone was completely resected. A trephine was used to create a 5-mm craniotomy defect centred on the parietal calvarial bone, and the wounds were copiously irrigated with Hanks’ balanced salt solution while drilling. The calvarial disk was removed carefully to avoid injury to the underlying dura or brain. After careful haemostasis, the cell-free miRNA-releasing scaffolds were placed in the defects. The incisions were closed with 4-0 braided absorbable sutures (Covidien, USA), and the mice recovered from anaesthesia on a heating pad. All mice were killed and calvaria were harvested at 8 weeks after the implantation.