Hydroxyapatite is a calcium phosphate with the formula Ca10(PO4)6(OH)10 and it is the main constituent of mineral phase of bone. This biomaterial is widely used after bone tumor surgery for treatment of bone defects and for coating of the metallic implants which are applied for total hip-joint replacement and artificial tooth sockets. However, most of the bone implants are weak in osteoconduction, osteoinduction, and osteogenesis. The aim of this study was to synthesis mesoporous hydroxyapatite under reflux condition and to prepare hydroxyapatite thin film with different thicknesses by dip-coating method. To confirm the mesoporous structure of synthesized hydroxyapatite, BET analysis was performed. It has been revealed that HAP nanoparticles have BET surface area (SBET) of 38.425 m2/g, pore volume (VP) of 0.37 cm3/g and average pore size (DP) of 38.7 Å. The thickness and morphology of the hydroxyapatite films were then investigated by a field emission scanning electron microscopy (FE-SEM). Based on the data from FE-SEM images, hydroxyapatite films displayed a granular surface and uniformed thickness between 63 nm to 940 nm. Osteoblast-like Saos-2 cells were cultured on thin films up to 14 days. By increase the hydroxyapatite thickness, Saos-2 cells showed a much great tendency for adhesion on the surface of hydroxyapatite films, however, the proliferation of cells decreased in a time dependent manner. Moreover, precise assessment showed that hydroxyapatite films have ability to induce osteogenic differentiation in Saos-2 cells, which was quantified by monitoring ALP activity and calcium deposition. A significant increase was observed in ALP activity in Saos-2 cells by increase the thickness of hydroxyapatite film. Corresponding with these results, calcium mineralization also augmented in attached cells, which was determined by Alizarin-Red staining. Collectively, based on high osteoinduction and osteogenesis properties of the prepared mesoporous hydroxyapatite film, it could be considered as an appropriate candidate in treatment of bone defects after bone tumor surgery.

Keywords