Development and evaluation of albumin microspheres as a radiopharmaceutical

Human serum albumin emulsion (HSAM), prepared using albumin and cottonseed oil and having microspheres of about 1 μm, was investigated. The iodination of these microspheres using 2 methods were compared using iodine 125 (125I). The blood clearance of technetium-99m-sulfur (99Tc) colloid nd 125I-HSAM in rabbits was studied. A NaI(Tl) well crystal detector was positioned at the ear vein to allow continual monitoring. The average half-time was 56.9 sec for 125I-HSAM and 69.3 sec for 99Tc colloid. Male mice were used for the investigation of liver uptake and distribution of 125I-HSAM and 99Tc colloid. The liver uptake of 125I-HSAM reached a maximum of 85.7 +- 3.7% of the whole body count rate and 88 +- 3.7% of injected dose 6 minutes after injection. The liver uptake of 99Tc colloid reached a maximum of 89.2 +- 3.5% of injected dose 4 minutes after injection. Six time periods, 6 min, 2, 8, 32, 128, and 512 hr after injection were chosen for the biodegradability study of 125I-HSAM in the liver of mice. Radioactivity in the liver at each time period was expressed as a % of the injected dose and also as a fraction of the 6 min value. The fraction of radioactivity in the liver at 6 min was taken at 1.00. The fraction of radioactivity remaining in the liver at 32 hr and 512 hr was 0.35 +- 0.02 and 0.06 +- 0.01 respectively