Neutron Activation Preparation of ¹⁶⁶Ho-Albumin Microspheres as a Promising Radiopharmaceutical for Tumor Therapy

Abstract

A procedure of activation with thermal neutrons of ¹⁶⁵Ho incorporated in the particle matrix was developed for preparing human blood albumin microspheres (AMs) labeled with ¹⁶⁶Ho. Since the specific activity of ¹⁶⁶Ho-AMs depends on the content of stable ¹⁶⁵Ho in AMs, the features of incorporation of stable holmium in the AM matrix were studied. The content of ¹⁶⁵Ho in AMs was determined by neutron activation analysis. It was found that ¹⁶⁵Ho is incorporated in the solid matrix in the course of its preparation by thermal denaturation of albumin in vegetable oil. The concentration of ¹⁶⁵Ho in AMs increases with increasing initial content of Ho₂O₃ in olive oil. With increasing particle size, the content of ¹⁶⁵Ho in AMs also increases and reaches a maximum (60%) in the fraction of AM particles with a diameter of 40–60 μm prepared at the highest content of Ho₂O₃ in the olive oil of 3.575 mg ml⁻¹. Thus, the coarser the AM fractions, the more active preparation will be obtained upon irradiation with thermal neutrons.