Preparation and characterization of biodegradable chitosan/hydroxyapatite nanocomposite rods via in situ hybridization: a potential material as internal fixation of bone fracture

A transparent and slight yellow chitosan (CS)/hydroxyapatite (HA) nanocomposite with high performed, potential application as internal fixation of bone fracture was prepared by a novel and simple in situ hybridization. The method solves the problem of the nano-sized particle aggregation in polymer matrix. XRD, TEM and SEM were used to determine component and morphology of the composite. Results indicated that nano-HA particles were dispersed well in CS matrix, which can also be proved by the transparent appearance of composite rod, and that the structure of composite is assembled by CS molecule in the order of layer-by-layer. The mechanical properties of the composite were evaluated by using bending strength and modulus, and compared with some other bone replacement materials such as PMMA and bone cement. The initial mechanical properties of bending strength and modulus of composite are 86 MPa and 3.4 GPa, respectively, which is double or triple times stronger than that of PMMA and bone cement. It was found that the bending strength and modulus of CS/HA with ratio of 100/5 (wt/wt) is slightly higher than that of pure CS rod. The addition of HA can also reduce the ratio of water absorption of composite, which postponed the retention of mechanical properties of CS/HA composite under moisture condition. The phenomenon can be predicted with the fit exponential function according the data measured.