Synthesis and Characterization of Biphasic Calcium Phosphate Substituted Cerium as a Potential Osteoporotic Bone Filler

Abstract

Biphasic calcium phosphate substituted cerium (BCP/Ce) is a potential material for osteoporotic bone filler. Synthesis of BCP/Ce was conducted by the sol-gel method. This work aimed to study the influence of cerium as a precursor on the crystal structures, surface properties, and agglomeration of BCP/Ce. A series of samples were prepared by various Ce percentages (0.5–16%) and a constant molar ratio of (Ca + Ce)/P = 1.2. A structural study by Rietveld refinement calculation confirmed that synthesis without Ce produced BCP that contained hydroxyapatite (HA) and β-tricalcium phosphate (β-TCP) at a ratio of 93:7. The presence of Ce increased β-TCP content to 73% for the use of Ce 8%. None of Ca in the HA structure was replaced by Ce. Otherwise, Ce replaced Ca in β-TCP structure by isomorphic substitution at the Wyckoff site of 6a (0,0,-0.085) or Ca (4) position. As the maximum occupancy of Ca (4) = 43%, about 17% of that was substituted by Ce for the use of 14% Ce. Ce was found in two states as Ce³⁺ and Ce⁴⁺ ions with Ce³⁺/Ce⁴⁺ ratio > 1. The presence of Ce on the particle surface caused a change in the particle shape, from plate-like to spherical. The particle size decreased to <100 nm with the increase of Ce content. The rise of Ce content in BCP decreased the luminescent property due to the increase of oxygen vacancies. The negative value of Zeta potential confirms that BCP/Ce surface can accommodate bone cell proliferation.