Directly labeling ferrite nanoparticles with Tc-99m radioisotope for diagnostic applications

We report a novel approach of directly labeling the radioisotope Tc99m with magnetite (Fe/sub 3/O/sub 4/) nanoparticles for diagnostic applications. The magnetite nanoparticles were first synthesized from aqueous solutions of Fe(II) and Fe(III) chloride, with addition of ammonium hydroxide. Subsequently, the radioisotope Tc-99m were mixed directly into the reaction solution with ferrite precipitation. The labeling efficiency, of ferrite nanoparticles bound with Tc-99m, is above 99%. As prepared radioactive ferrite nanoparticles were intravenously injected into rats. The biodistribution of radioactivity, monitored by gamma-camera, has shown the uptake of radiomicrospheres can be restrained and transferable in vivo in the living animals by applying an external Nd-Fe-B magnet. Final fate of the radiomicrospheres is to be related with the surface charge of particles. Modification of surface charge of the radiolabeled ferrite nanobeads for clinical targeted diagnosis is discussed.