Radiolabeled nanoporous hydroxyapatite microspheres: An advanced material for potential use in radiation synovectomy

The design and fabrication of porous and biocompatible inorganic materials having high adsorption capacity for therapeutic radioisotopes can trigger development of 'next-generation' radiopharmaceuticals for use in clinical nuclear medicine. In this study, nanoporous hydroxyapaptite (HA) microspheres of 1-10 mu m diameter were synthesized by sol-gel technique followed by spray drying. The synthesized microparticles exhibited remarkably high sorption capacity for 90Y (141 +/- 5 mg Y/mg) and 166Ho (262 +/- 3 mg Ho/mg), which enabled the use of low specific activity radioisotopes produced in medium flux research reactors. Sorption of 90Y and 166Ho in nano -porous HA followed Langmuir-Freundlich adsorption isotherm and pseudo second order kinetics, indicating that the process was chemisorption. A chelator-free radiolabeling technique was developed for loading clinically relevant doses of radioisotopes such as 90Y and 166Ho in the HA matrix for use in treatment of arthritis. As a proof of concept, 90Y labeled formulation was administered in a patient with painful arthritis of knee joint. Selective localization of the radiolabeled agent in the synovial cavity was demonstrated by SPECT/CT imaging which demonstrated its potential for use in radiation synovectomy.