Strontium modified biocements with zero order release kinetics

Strontium-substituted β-TCP with the general formula Ca(3−x)Srx(PO4)2 (0 < x < 1) was synthesized by calcination of powder mixtures with the appropriate stoichiometry and reacted with acidic monocalcium phosphate monohydrate (MCPM) to form a cementitious matrix of secondary calcium phosphates. The use of Sr-substituted β-TCP as a reactant not only induced strontium substitution in the setting products but surprisingly it also favoured the formation of monetite (CaHPO4) as setting product, whereas Sr-free cements set to brushite (CaHPO4·2H2O). Release experiments under dynamic conditions for up to 15 days revealed the release of Sr2+ ions at dose ranges of 12–30 ppm with zero order release kinetic. Cement cytocompatibility was investigated by culturing human osteoblast cell line hFOB1.19 on cement surfaces whereas Sr-containing cements were as good as Sr-free cements in providing a template for cell growth and function.