Study Of Preparation And Cytocompatibility Of Nano Silicon-substituted Hydroxyapatite

Due to its chemical similarity to inorganic structure of bone and its contain of Ca, P elements, HA is a well-known bioactive ceramic material with great biocompatibility and osteoinductivity. While implanted into human body, a chemical bonding can be formed between bone tissue and the calcium and phosphate ions from the dissolution of the material surface, which will lead the growth of new tissue. Recent studies have shown that the incorporation of Silicate into crystal structure of HA can greatly improve its in vivo and vitro bioactivity. Prolyl-4-hydroxylase is a key enzyme in collagen biosynthesis and its activity directly indicates the speed of collagen biosynthesis.In this thesis, different level of silicon-substituted hydroxyapatite were prepared by aqueous precipitation methods, which assume silicated anions substitute phosphate ones. The chemical formula of Si-HA is Ca10(PO4)6-x(SiO4)x(OH)2-x and the molar ratio of Ca/P+Si is 1.67. The morphology, structure, chemical component and crystal phase of the materials were determined by TEM, XRF, FTIR and XRD respectively. The results showed that silicated anions substituted some phosphate ones in the crystal lattice ,leading changes in structure and unit cell parameters of HA. Nano Si-HA with small amount of carbonate ions were prepared.To investigate the cytocompatibility of Si-HA, Mesenchymal stem cells from SD rat were cultured in the material leaching liquor of different level of silicon content. We tested the P4H activities of the cells using a ELISA kit to examine the impact of material on biomineralization. The results indicated that Si-HA has an improved cytocompatibility and P4H is related to the molecular mechanism in which Si-HA promotes bone healing. Porous scaffolds of silicon-substituted hydroxyapatite were fabricated by a paraffin microsphere approach whereafter its mechanical property and cytocompatibility were evaluated. The results imply a good porosity and cytocompatibility, but the mechanical property of the scaffold requires improvement.