Silicon-substituted calcium phosphate compounds: Synthesis, characterization, and bioactivity evaluation

Suphasinee L Seet

ABSTRACT: Hydroxyapatite (HA), the main component of bone and teeth, can improve its structure by incorporation of traces of silicon (Si). This paper reports a synthesis of Si-substituted calcium phosphate compounds via a chemical precipitation process. The solutions of hydroxyapatite and fumed silica were homogeneously mixed before precipitation using ammonia. The resultant solutions were then filtered and the obtained powders were calcined at various temperatures. It was found that the phase of as-precipitated powders was HA with an average size of 15 nm. However, β-tricalcium phosphate (TCP) was formed at the calcined temperature of 800 °C. From Fourier-transform infrared spectroscopy spectra, the Si-O peaks were observed when the as-precipitated powder was heated. It was concluded that there was a substitution of silicate ions for phosphate ions in the HA or β-TCP structure. To evaluate the effect of silicon on the bioactivity in vitro, pure HA and silicon-substituted HA (Si-HA) powders were uniaxially pressed and the samples were soaked in simulated body fluid at 37 °C for various periods of time. It was found that after 2 weeks of soaking, the surface of the Si-HA sample was covered by apatite layers, whereas that of pure HA remained unchanged even after 4 weeks. These results showed that the presence of silicon can enhance the bioactivity of HA.

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Department of Physics, Faculty of Science, Khonkaen University, Khonkaen 40002, Thailand

* Corresponding author, E-mail: lsupha@kku.ac.th, suphasinee@gmail.com

Received 4 Feb 2009, Accepted 16 Jul 2009