Study of C<sub>3</sub>S/Nano-HAp/Collagen Composite Bone Cement

Abstract

Composite bone cement composed of tricalcium silicate (Ca3SiO5, C3S), hydroxyapatite particle (nano-HAp) and collagen was prepared and investigated in this study. We synthesized C3S through a solid-state reaction and modified it by adding zinc oxide (ZnO) in order to stabilize the C3S phase during preparation. In order to achieve proper setting time and better powder characteristics, a series of different molar ratio of ZnO to CaCO3 precursors were tested. An optimized composition, Zn02.5Ca2.75SiO5, was chosen for further studies. Zn02.5Ca2.75SiO5 powder was mixed with 10 wt% NaH2PO4 solution with the liquid to powder (L/P) ratio of 2:5. The setting time was measured to be within one hour, and the pH value maintained between 8 and 10. Furthermore, 5 wt% nano-HAp particle and 2 wt% type I collagen were mixed to comprise the composite bone cement. The set product had a compressive strength up to 85 MPa. The set materials were further tested in vitro by culturing the mouse fibroblast cell line L929. Through the cytotoxicity tests (MTT) of the extracts in medium, the results revealed that the set matter had a good biocompatibility. When the cells were directly seeded onto the material, the cells attached well and would out-stretch their pseudopodia through SEM observation. The results of in vivo test through subcutaneous implantation in rat showed that the material was well biocompatible with neovessel formation. The results indicate that this novel composite bone cement exhibits good properties and biocompatibility as well as a desirable biomaterial. Keywords: Bone cement, collagen, in vitro study, in vivo study, nano hydroxyapatite particle, tricalcium silicate.