Bioceramic fibrous scaffolds built with calcium silicate/hydroxyapatite nanofibers showing advantages for bone regeneration

Abstract

Bioceramic materials currently applied in bone repairing mainly base on calcium phosphate compounds like hydroxyapatite (HA), however, issues including slow degradation rate and insufficient bioactivity limit their efficiency in promoting bone regeneration. Calcium silicate (CS) is a promising alternative for the purpose thanks to its degradability and bioactive Si4+ release ability, while its fast degradation rate will cause pH problem and does not match the rhythm of osteogenesis. Herein, 3D composite bioceramic scaffolds were fabricated by blending different weight fractions (1:0, 3:1, 1:1, 1:3 or 0:1) of CS nanofibers (CSNFs) and HA nanowires (HANWs) via steps of fiber-dispersing, freeze-drying and sintering. With subsequent polymer coating, the porous structure and mechanical properties of the CSNF/HANW scaffolds were improved and scaffold performances were further regulated in dependence on the hydrophobicity/hydrophilicity and degradation rates of the polymers. Poly(l-lactide) (PLLA), poly(lactide-co-caprolactone) (PLCL) and gelatin were applied as the polymer coating. It was found that PLLA- and PLCL-coating would slow down the scaffold degradation and ion release rate compared to the gelatin-coating, while the increasing fraction of CSNFs would accelerate these events to increase medium pH due to the alkalinity of the bioceramic material. Finally, proliferation and osteogenic differentiation of bone marrow mesenchymal stromal cells (BMSCs) achieved desirable outcomes on gelatin-coated CSNF/HANW scaffolds with their fractions of 1:1 and 1:3, strongly suggesting the potential of these scaffolds for bone regeneration.