Mechanical properties and in-vivo performance of calcium phosphate cement-chitosan fibre composite.

Self-hardened calcium phosphate cement (CPC) sets to form hydroxyapatite and possesses excellent osteoconductivity. However, lack of macroporosity and low strength constrain its application in bone tissue engineering. Recent studies have incorporated various fibres into CPC to improve its mechanical strength. The present approach focused on the reinforcement of CPC with chitosan fibres and then the effects of the fibre structure on the mechanical properties and macrochannels formation characteristics of CPC-fibre composite were investigated. Chitosan fibres of diameter 200 microm were used to fabricate two types of three-dimensional structure, which were then coated with collagen and incorporated into CPC to fabricate CPC-fibre implants with a fibre volume content of 5 per cent. The compressive strength of the CPC-fibre implant was 33 MPa when the strain was 2.4 per cent, which is fourfold higher than that of the CPC control. Nine cylindrical implants including six CPC-fibre implants were implanted in the bone defects of nine dogs and were then post-operatively observed. After 20 weeks in vivo, new callus from the healthy tissue of the defect entirely integrated with the CPC-fibre implant and new bone was formed as the implant degraded. Scanning electronic microscopy images indicated that macrochannels were formed in the CPC-fibre implants with the degradation of fibres, but only micropores with a scale of less than 50 microm could be observed in the CPC control. Briefly, the incorporation of a suitable chitosan-fibre structure into a CPC implant not only could improve its mechanical properties but also facilitated the bone repair process in vivo.