SYNTHESIS OF NANOHYDROXIAPATITE DOPED WITH STRONTIUM IONS: INFLUENCE OF sr2+ ON THE STRUCTURAL PROPERTIES OF NANOPARTICLES AND MICROPOROUS CERAMIC BIOMATERIALS

Abstract

At present, ion-functionalized hydroxyapatite (HA-X) allows the development of new proposals for biomedical implants with greater similarity to natural hydroxyapatite, while some of these ions encourage biological processes for early implant osseointegration. In particular, doping with Sr²⁺ is very interesting due to the known dual role of this ion of influencing bone metabolism, favoring osteosynthesis and, at the same time, limiting osteoclasty. This work evaluates the effectiveness of the wet synthesis coupled to ultrasound to obtain HA-Sr with 0, 10, 20% molar substitution of the Ca²⁺ ion. The particles were characterized by Infrared Spectroscopy, X-Ray Diffraction, X-Ray Photoelectron Spectroscopy and Dynamic Light Scattering. Ceramics were prepared from the synthesized apatites by sintering at 900 °C/6 h, which were analyzed by Scanning Electron Microscopy and their in vitro bioactivity was studied by immersion in Simulated Body Fluid solution. The results obtained indicated good efficacy of the methodology used to obtain the HA-Sr. It was detected that particles were nanometric, that with the incorporation of Sr²⁺ the crystallite sizes decrease from ~50nm to ~30nm, the crystallinity fraction decreases by almost 80% (from 74.3% to 12.5%), while the volume of the unit cell increased. The presence of Sr²⁺ in the hydroxyapatite significantly increased the shrinkage of the ceramic pieces and decreased their total porosity. At the same time, it increased the size of the ceramic grains, decreased the dimensions of the pores and narrowed their distributions. It was also shown that the presence of Sr²⁺ accelerates the bioactivity of ceramics, making them suitable