In-situ reinforced hydroxyapatite/chitosan composite rods

Calcium phosphate microfibrils were fabricated by a homogeneous low-temperature deposition method in an aqueous solution. Chitosan (CS) rods were prepared via an in-situ precipitation processing, and hydroxyapatite(HA^*)/CS composite rods were prepared on the base of the in-situ precipitation processing. The calcium phosphate microfibrils were transformed to hydroxyapatite style through the in-situ precipitation method. X-ray diffractometer (XRD) and scanning electron microscope (SEM) were performed to characterize structure and morphology of the calcium phosphate microfibrils and the hydroxyapatite crystals. Moreover, the transformation mechanism from calcium phosphate to hydroxyapatite was also discussed. XRD results show that the calcium phosphate transforms to hudroxyapatite through the in-situ precipitation processing. SEM results exhibit that the hydroxyapatite crystals are dispersed uniformly in the composites and formed an inlayed and occlusive structure with the CS matrix, which led to significant improvement in mechanical properties of the HA^*/CS composite rods. Results indicate that the HA^*/CS composites show much better mechanical properties than a commercial HA reinforced CS matrix composites. Flexural properties of the HA^*/CS composites are increased with increasing HA^* concentration within its saturated solubility, mass fraction 3.3%. Flexural strength and flexural modulus of the HA^*/CS composites with 3.3% hydroxyapatite are 159.6 MPa and 5.1 GPa, respectively, which are 85.6% and 54.5% higher than the neat CS rod. The mechanical properties of the HA^*/CS composites are much higher than cancellous bone, and close to compact bone.