Preparation and properties of three-dimensional hydroxyapatite/chitosan nanocomposite rods.

To meet the demand for the bone fracture internal fixation, hydroxyapatite/chitosan (HA/CS) nanocomposite rods were reinforced via a covalently crosslinking method. The bending strength and bending modulus of the crosslinked HA/CS (5/100, wt/wt) rods could arrive at 178 MPa and 5.2 GPa, respectively, increased by 107% and 52.9% compared with uncrosslinked HA/CS (5/100, wt/wt) rods. XRD analysis indicated that the crystallinity of CS decreased after the network structure formed. CS crystal plane space (d) became smaller after crosslinking, but HA nanoparticles could prevent the decrease of d. HA nanoparticles (100 nm in length, 20-30 nm in width) were uniformly dispersed in a CS matrix. Increasing the content of HA, the acicular morphology of HA particles became vague, but crosslinking could make the acicular morphology clear over again, because the size of HA nanoparticles became smaller after crosslinking. A microstructure was observed by SEM, indicating that a layer-by-layer structure of the composite rods became much tighter through crosslinking, and the cracks turned around when they reached another layer to absorb energy. Consequently, HA/CS nanocomposite rods with high mechanical performance should be one novel device used for internal fixation of bone fracture.