Investigating an organ-targeting platform based on hydroxyapatite nanoparticles using a novel in situ method of radioactive 125Iodine labeling

Abstract

In this study, we have investigated the synthesis of nanoparticles of hydroxyapatite (HAp) and hydroxyapatite coated with chitosan (HAp/Ch) and the chitosan-poly-d,l-lactide-co-glycolide polymer blend (HAp/Ch-PLGA) as an organ-targeting system. We have examined and defined the final destination, as well as the dynamics and the pathways of the synthesized particles following intravenous administration in vivo.The XRD, ZP, FT-IR and SEM analyses have confirmed that the hydroxyapatite nanoparticles with d50=72nm are coated with polymers. Radioactive 125-Iodine (125I), a low energy gamma emitter, was used to develop a novel in situ method for the radiolabeling of particles and investigation of their biodistribution. 125I-labeled particles exhibited high stability in saline and serum over the second day, which justified their use in the following in vivo studies.The biodistribution of 125I-labeled particles after intravenous injection in rats differed significantly: HAp particles mostly targeted the liver, HAp/Ch the spleen and the liver, while HAp/Ch-PLGA targeted the lungs. Twenty-four hours post injection, HAp particles were excreted completely, while both 125I-HAp/Ch and 125I-HAp/Ch-PLGA were retained in the body for a prolonged period of time with more than 20% of radioactivity still found in different organs.