Biomimetic triphasic strontium-substituted calcium phosphate (CaP) powders were prepared by wet precipitation method at 50°C, using CaCO3 , (NH2 )2 COH3 PO4 , and Sr(NO3 )2 as reagents. Calcite was prepared from biogenic source (cuttlefish bone). The synthesized powders have been characterized by elemental analysis, Fourier transform infrared spectrometry, X-ray diffraction, Rietveld refinement studies and cell viability test. Phase transformation and ion release were analyzed during 7 days of incubation in simulated body fluid at 37°C. The raw precipitated powders were composed of calcium deficient carbonated hydroxyapatite (HA), octacalcium phosphate (OCP), and amorphous calcium phosphate (ACP). After heat treatment at 1200°C β-tricalcium phosphate (β-TCP) was detected. Strontium substitution for calcium results in an increase of lattice parameters in HA, OCP, and β-TCP. Sr2+ occupy the Ca(1) site in HA, Ca(3,4,7,8) sites in OCP and Ca(1,2,3,4) sites in β-TCP. Along with Sr2+ substitution, presence of Mg2+ and Na+ ions was detected as a result of using biogenic calcium carbonate. The culture of human embryonic kidney cells indicated noncytotoxicity of the prepared CaP powders with emphasis on the cell proliferation during 3 days of culture.
Keywords: Rietveld refinement; cosubstitution; hydroxyapatite; octacalcium phosphate; strontium.
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