3D Superelastic Scaffolds Constructed from Flexible Inorganic Nanofibers with Self-Fitting Capability and Tailorable Gradient for Bone Regeneration

Repair of bone defects with irregular shapes or at soft tissue insertion sites faces a huge challenge. Scaffolds capable of adapting to bone cavities, generating stiffness gradients, and inducing osteogenesis are necessary. Herein, a superelastic 3D ceramic fibrous scaffold is developed by assembly of intrinsically rigid, structurally flexible electrospun SiO2 nanofibers with chitosan as bonding sites (SiO2 NF-CS) via a lyophilization technique. SiO2 NF-CS scaffolds exhibit excellent elasticity (full recovery from 80% compression), fast recovery rate (>500 mm min(-1)), and good fatigue resistance (>10 000 cycles of compression) in an aqueous medium. SiO2 NF-CS scaffolds induce human mesenchymal stem cell (hMSC) elongation and differentiation into osteoblasts. In vivo self-fitting capability is demonstrated by implanting compressed SiO2 NF-CS scaffolds into different shaped mandibular defects in rabbits, with a spontaneous recovery and full filling of defects. Rat calvarial defect repair validates enhanced bone formation and vascularization by cell (hMSC) histomorphology analysis. Further, subchondral bone scaffolds with gradations in SiO2 nanofibers are developed, leading to a stiffness gradient and spatially chondrogenic and osteogenic differentiation of hMSCs. This work presents a type of 3D ceramic fibrous scaffold, which can closely match bone defects with irregular shapes or at different implant sites, and is promising for clinical translation.