A bioinspired bilayer periosteum-mimicking membrane for enhanced osteogenesis and angiogenesis in guided bone regeneration

Guided bone regeneration (GBR) membranes with osteoinductive and angiogenic capabilities are essential for the effective repair of large bone defects. In this study, we design and fabricate a biomimetic bilayer GBR membrane composed of a nano-hydroxyapatite/type I collagen/ polycaprolactone (HC layer) and chitosan/ polycaprolactone (CP layer) composite via electrospinning strategy. The core-shell fibrous architecture replicates the natural periosteum's fibrous hierarchy and provides controlled collagen release, mechanical integrity, and enhanced interfacial functionality. The physical, chemical, and mechanical properties of the membranes were comprehensively characterized, and in vitro assays demonstrated excellent cell adhesion, proliferation, and osteogenic differentiation of pre-osteoblasts on the bilayered membrane. In addition, the membrane promoted endothelial cell migration, tube formation, and upregulation of angiogenesis-related genes, confirming its pro-angiogenic capacity. Furthermore, in vivo evaluation using a critical-sized rat calvarial defect model revealed that the bilayered membrane significantly enhanced new bone formation compared to commercial HAO membranes, as confirmed by micro-CT and histological analysis. This work provides a mechanically robust, biologically active, and structurally biomimetic GBR membrane capable of promoting both osteogenesis and angiogenesis in a coordinated manner. The proposed strategy offers promising potential for the clinical treatment of complex bone defects.