Sericin Protein / Calcium Phosphate Composite Preparation Process Research

Human bone and teeth are composed by protein and hydroxyapatite (HA) with different morphologies and the sizes of HA crystallite with sheet-like morphology in bone and with rod-like morphology in teeth are about 25 nm×3 nm and 130 nm×30 nm, respectively. A series of researches in getting organic-inorganic hybrid materials via biomimetic synthesis and controlling the crystallinity, morphology and size of the HA crystal have been taken to make the HA being the excellent material. In this paper, silk sericin (SS) was selected as organic template for crystal formation and SS/HA compostie was prepared via co-precipitation method. The effect of reaction condition, including pH values, reaction temperature and time, on crystal formation has been investigated using XRD, FTIR, TEM, HRTEM and FESEM. The results were as follows:1. The pH value had a notable influence on the morphology of SS/HA crystal. Sheet-, needle- and enamel-like HA assemblies were gained and the size of nano-particles decreased with pH value increasing. In particular, HA crystals obtained at pH 12 were assembled along the c-axis by the smaller crystals, which were similar to enamel prisms structure.2. Crystallinity of particle was improved with the increase of reaction temperature and higher temperature resulted larger size of the crystal. It had little influence in the morphology of crystal when the pH value was low, while affected obviously that of crystal obtained at higher pH value. The result showed that morphologies of formed particle changed gradually from spherical to needle-like and then rod-like with a change of reaction temperature from 25℃to 70℃.3. Effect of reaction time on the HA formation was investigated at pH 10 and 50℃. It was found that reaction time mainly affected samples in terms of crystallinity and longer reaction time lead to higher crystallinity of particle. Furthermore, morphology of the crystal changes from sphere to needle-like assembly. The SS/apatite composite maybe firstly formed ACP, then fused together and transformed to HA.The results showed that it is possible to control the size and morphology of hydroxyapatite by selecting appropriate synthesis condition. This research may provide new insight into the control of morphologies of hydroxyapatite and the biomimetic synthesis of novel inorganic materials.