Biodegradable Samarium-153–labelled microspheres for hepatic radioembolization: preparation, characterization and radiolabelling evaluation after neutron activation

Abstract

A biocompatible and biodegradable radioactive samarium-153 (153Sm)-labelled Poly-(L-lactic acid) (PLLA) microspheres was developed for hepatic radioembolization. Samarium acetylacetonate was encapsulated in PLLA microspheres using oil-in-water solvent evaporation method. Physicochemical characterization of the microspheres were analysed using Field Emission Scanning Electron Microscopy, Energy Dispersive X-ray spectroscopy and particle size analyser. The prepared microspheres were irradiated in a nuclear reactor with a neutron flux of 1.49 × 1012 n.cm-2.s-1, converting 152Sm to 153Sm (Emax = 807.6 keV, half-life = 46.3 h). Gamma spectroscopy was carried out to determine the presence of radionuclide impurities while the in-vitro radiolabelling efficiency was performed to analyse the retention of 153Sm on the microspheres. The Sm-labelled PLLA microspheres was found spherical with the diameters within 20-60 μm, as indicated by the scanning electron microscopy and particle size distribution results. Gamma spectrometry suggested that no long half-life radioimpurities present after neutron activation. The 153Sm-labelled PLLA microspheres has achieved a nominal activity of 5.9 GBq.g-1 after 6 h neutron activation. The formulation showed more than 97% radiolabelling efficiency in saline and human blood plasma over 550 h. The 153Sm-labelled PLLA microspheres are potentially useful for hepatic radioembolization due to their biodegradability, favourable radiation characteristics and excellent radiolabelling efficiency. The preparation of the formulation does not involve ionizing radiation and hence reduces the costs of production.