One-Step Gas Foaming Strategy for Constructing Strontium Nanoparticle Decorated 3D Scaffolds: a New Platform for Repairing Critical Bone Defects

The management of critical-sized bone defects poses significant clinical challenges, particularly in the battlefield and trauma-related injuries. However, bone tissue engineering scaffolds that satisfy high porosity and good angiogenic and osteogenic functions are scarce. In this study, 3D nanofiber scaffolds decorated with strontium nanoparticles (3DS-Sr) were fabricated by combining electrospinning and gas foaming. Sodium borohydride (NaBH₄) served a dual role as both a reducing and gas-foaming agent, enabling a one-step process for expansion and modification. In vitro experimental results demonstrated that 3DS-Sr possessed an integrated multilayered porous structure. It promoted angiogenesis by upregulating the expression of hypoxia-inducible factor-1α (HIF-1α) protein and phosphorylation of ERK through the sustained release of Sr²⁺ and created a favorable microenvironment for osteogenesis by activating the Wnt/β-catenin pathway. In vivo experiments indicated that 3DS-Sr promoted cranial bone regeneration by synergistically promoting the effects of vascularization and osteogenesis. In summary, this study proposed a bioactive bone scaffold in a "one stone, two birds" manner, providing a promising strategy for bone defect repair.