Bioinspired nanostructured hydroxyapatite/collagen three-dimensional porous scaffolds for bone tissue engineering

Abstract

During the biomineralization process of bone minerals, amorphous calcium phosphate (ACP) is converted to apatite crystals by using octacalcium phosphate (OCP) and brushite (DCPD) as transitory precursors, resulting in the formation of hybrid nanostructured collagen/apatite composites. Herein, we report, for the first time, the bioinspired synthesis of a collagen/hydroxyapatite (HA) porous scaffold (CHPS) according to the following stages: (i) fabrication of collagen fibre porous scaffold (CFPS) by a needle-punching process; (ii) deposition of brushite/chitosan (DCPD/CS) on CHPS by a dip-coating method; and (iii) formation of CHPS by in situ conversion of DCPD to HA. The CHPS exhibits three-dimensional (3D) interconnected porous structures with pore sizes of around 60 μm. HA crystals distribute homogeneously on the CHPS, and display wheat-like shapes with a length of approximately 200 nm and a width of approximately 80 nm. The in vitro cell tests by using human bone marrow stromal cells (hBMSCs) indicate that the HA crystals in the CHPS not only promote the cell adhesion and proliferation of the hBMSCs, but also stimulate osteogenic differentiation. The in vivo results reveal that the CHPS exhibits better osteoinductivity than the CFPS because of its similar chemical components, crystallinity and crystallographic texture to natural bone. Moreover, the CHPS can stimulate new bone formation in rat critical-sized calvarial defects within 8 weeks. The CHPS possesses a favourable pore structure, and excellent biocompatibility and osteoinductivity, and thus it has great potential applications for bone tissue engineering.