Bone-like layer growth and adhesion of osteoblast-like cells on calcium-deficient hydroxyapatite synthesized at different pH

Calcium-deficient hydroxyapatite (DAp) was synthesized by hydrolysis of alpha-TCP at different pH. Ca/P ratio of DAp increased with increasing pH during the hydrolysis. In addition, DAp which was synthesized at lower pH, showed higher solubility in the simulated body fluid (SBF) and had a more negatively charged surface than that at higher pH. Bone-like crystals were formed on DAp which have been soaked in SBF at 309.5 K in vitro. DAp demonstrated faster formation of a bone-like layer than stoichiometric hydroxyapatite (HAp). Moreover, the formation of the crystals on DAp synthesized at lower pH was much faster than that at higher pH. The adhesion of MC3T3-E1 osteoblast-like cells was also influenced by pH during the synthesis of DAp; the number of adhering cells increased with a decrease in the pH. Therefore, high solubility and negative charge of DAp, especially that synthesized at lower pH resulted in fast formation of bone-like crystals and good cell adhesion