Features of synthesis of sodium and carbonate containing biphasic calcium phosphates and their cytotoxicity

Biphasic calcium phosphates (BCP) (hydroxyapatite/beta-tricalcium phosphate = HAP/beta-TCP) were synthesized from aqueous solutions in different weight ratios of components containing 0.5-2 wt % of Na+ and up to 3 wt % of CO32-. According to powder XRD data, the increasing of Na+ amount in the initial solution (molar ratio Na+/Ca2+ = 0.02-0.1) led to growing of the content of phase based on beta-Ca-3(PO4)(2) (TCP-up to 90wt%) while the addition of carbonate-anions (CO32-/PO43- = 0.1) caused to increase of apatite-type phase content (up to 90wt%) in the obtained compositions. Cytotoxicity of synthesized biphasic calcium phosphates was determined by MTT test. Cells were incubated with different amount (0.05-20 mg/ml) of composites for 24 h. It was found that addition of 20 mg/ml of biphasic calcium phosphate with ratio HAP/beta-TCP = 90/10 wt% decreased cell viability of 3T3 cells (the embryonal mouse fibroblast cell line) by only 20% while presence of sample with ratio HAP/beta-TCP = 10/90wt% led to an enhancement in optical density which could be a result of an increase in the number of cells or in cell density. The found conditions for preparation of biphasic calcium phosphates in different weight ratios (HAP/beta-TCP) containing different amounts of sodium cations (0.5-2%wt) and up to 3%wt of carbonate can be further used in the development of materials with the required resorption rate for orthopedics.