Synthesis of nanohydroxyapatite modified with lanthanum and cerium ions: composition and properties

Lanthanide-doped hydroxyapatite nanoparticles can be used as luminescent labels and become an alternative to organic fluorophores, as they are more stable and have a longer service life. Such materials allow tissue studies in surgery, the bone engineering and tissue regeneration. Lanthanides are known to have a high affinity for hydroxyapatite. This is due to the fact that lanthanides have ionic radii close to that of the calcium ion which is associated with their biological activity. Rare earth elements inhibit the formation of osteoclast-like cells and the process of the bone resorption. At the same time, lanthanides have a biological effect on the body, as a result bacterial growth is suppressed and, at the same time, the structure of the outer cell membrane, responsible for cell permeability, changes. Substituted hydroxyapatites were synthesized with varying content of the lanthanum (III) and cerium (III) ions. The formation of substituted hydroxyapatite was proven by X-ray diffraction and infrared spectroscopy. The parameters of the crystal lattices of the synthesized phases were shown to change, indicating the replacement of calcium ions by rare earth element ions in the hydroxyapatite structure. The presence of rare earth element ions in solid phases was proven by inductively coupled plasma atomic emission spectroscopy. The study of the resorption of thesynthesized samples revealed that cation-substituted hydroxyapatites are less soluble than unmodified hydroxyapatite. Thus, lanthanum (III) and cerium (III) ions can inhibit and suppress the action of osteoclasts and thereby prevent the destruction of the bone tissue maintaining its integrity. Accordingly, the material based on hydroxyapatite dosed with rare earth element ions can have a positive effect when used in bone engineering.