Influence of Sr2+ in calcium phosphates formation on the surface of Al2O3/ZrO2 nanocomposites

Abstract This study investigated the influence of Sr2+ ions incorporation in calcium phosphates formation on the surface of Al2O3/ZrO2 (5 vol%) nanocomposites. For this, Al2O3/ZrO2 samples were shaped, calcined (400 °C for 1 h), and sintered (1500 °C for 2 h). After surface treatment with aqueous phosphoric acid solution (H3PO4), the nanocomposite was biomimetically coated with Simulated Body Fluid (SBF) solutions 5x enriched with different concentrations of Sr2+ ions for 14 days. The samples were then characterized by confocal microscopy, scanning electron microscopy (SEM), contact angle and X-ray diffraction. In general, the formation of phases attributed to both calcium phosphates and strontium on the surfaces of nanocomposites was observed, evidencing the partial replacement of calcium ion (Ca2+) by strontium ion (Sr2+) in the structure of phosphates. Thus, the following phases were identified: tricalcium α-phosphate (α-TCP), tricalcium β-phosphate (β-TCP), tetracalcium phosphate (TTCP), hydroxyapatite (HAp), strontium phosphate (SrP) and Sr-incorporated HAp (Sr-HAp). Moreover, Sr2+ ions incorporation in the structure of phosphates also influenced their morphology. Therefore, Sr2+ ions increase adsorption, bioactivity and osteoconduction of calcium phosphates.