Modification of HAp nanoparticles using phosphonate ligands

Hydroxyapatite is a biocompatible and biodegradable material used in orthopaedic implants and often exploited for the construction of bioactive cargo delivery systems. Phosphonic acids were studied as colloid stabilising agents for hydroxyapatite nanoparticles (HAp-NPs). Hydroxyapatite nanoparticles were prepared by precipitation of Ca(NO₃)₂ and (NH₄)2HPO₄ at pH 11. The precipitate was washed with ultrapure water, lyophilized and grinded. Stabilized samples were prepared from already-made HAp-NPs suspended in water by addition of phosphonic acids solution and sonification of the mixture. The hydrodynamic size of resulting particles was measured using dynamic light scattering. The HAp-NPs were labelled with ^99mTc obtained from the ⁹⁹Mo/⁹⁹mTc generator and ²²³Ra obtained from the ²²⁷Ac/²²⁷Th/²²³Ra generator. Subsequent in vitro stability studies were carried out in bovine serum, bovine plasma, saline and 5% albumin solution. Finally, in vivo studies were performed with the selected composite compounds [^99mTc]-HDP-HAp a [²²³Ra]-NPMIDA-HAp. (authors)