Abstract: Incorporation of hydroxyapatite(HA) with chitosan(CS) could improve the bioactivity and the bone-bonding ability of CS/HA composite, which maybe sacrifice its mechanical properties. The CS/HA nanocomposite with a high performance was prepared via in-situ compositing route. The key of in-situ compositing is that a pre-precipitated CS membrane was used to obstruct the CS/HA precursor from NaOH aqueous solution. The CS membrane controlled the process of CS precipitation and transformation of HA from the precursor due to changing of pH simultaneously and tardily. XRD were carried out to determine the component of CS/HA composite. TEM and SEM were performed to investigate the morphology of HA granules and CS/HA composite. The results showed that the in-situ formed calcium phosphate in CS was exactly HA, and that nano-size HA granules(30—50 nm width, 100 nm length) were dispersed in CS matrix uniformly. The result of SEM shows that the structure of CS/HA composite prepared by in-situ compositing is layered-by-layered, which can further prove the mechanism of in-situ compositing. The mechanical properties of CS/HA were evaluated by the three point bending test. The bending strength and modulus of CS/HA(mass ratio 100/5) are 86 MPa and 3.4 GPa, which is much higher than that of cancellous bone, 22 MPa. This material is of potential application as bone substituent in hard tissue reparation.

Key words: Chitosan, Hydroxyapatite, In-situ compositing, Layered structure