bioactivity enhancement of hydroxyapatite by silicon substitution

objective: silicon is an effective element in bone biomineralization; hence si-substituted hydroxyapatite can be a relevant bioceramic as bone materials substitution. materials and methods: stoichiometric hydroxyapatite (ha) and si-substituted hydroxyapatite (si-ha) with different contents of si substitution were synthesized successfully by a hydrothermal method using ca(no3)2, (nh4)3po4 or (nh4)2hpo4 and si(och2ch3)4 (teos) as starting materials. results: crystalline phases, chemical composition, microstructure and morphology of synthesized powders were investigated using x-ray diffraction (xrd), fourier transform ir spectroscopy (ftir), inductively coupled plasma aes (icp-aes) and scanning electron microscopy (sem) techniques. the results proved silicon substitution in hydroxyapatite structure and revealed that the substitution of phosphate groups by silicate groups caused some oh- loss to maintain charge balance and the lattice parameters slightly changed with respect to stoichiometric ha. conclusion: si-incorporation reduces the crystallites size of si-ha and crystallinity, thus the solubility of si-ha powders increases, and as a result si- substitution has improved bioactivity behavior of ha. based on in-vitro tests; soaking and incubating the specimens in simulated body fluid (sbf) and mtt assays (dimethylthiazol assay), si-substituted hydroxyapatite is more bioactive than pure hydroxyapatite.