Preparation of technetium-99 m human albumin nanospheres for use in the measurement of reticuloendothelial clearance capacity

Background: The rate at which radioactive albumin particles clear from the bloodstream is used to measure reticuloendothelial capacity. Traditionally, iodine radioisotopes have been used. Non-active albumin particles mixed with the technetium-99 m labelled particles of the readily available radiopharmaceutical 99 mTc Albumin Nanocolloid (ANC) would be more convenient. Aim: To prepare human albumin nanospheres (HAN) with a diameter similar to 99 mTc-ANC and to investigate their stability. Experimental: HAN were prepared by heating 30 g/l albumin solution pH 10 at 70°C for 20 min then 75°C for 17.5 min, adjusting to pH 7.5 and sterilizing by filtration. Seven batches were prepared. The HAN diameter was measured by photon correlation spectroscopy at 0–3 months. Various measures of stability were performed. Results: The mean diameter of the HAN was 3.9 ± 1.9, 4.0 ± 1.5, 4.4 ± 1.6 and 4.2 ± 2.0 nm at 0, 1, 2 and 3 months. After mixing HAN and 99 mTc-ANC, no changes in particle size or radiolabelling of ANC were detected. Conclusions: HAN with a diameter comparable to the particles in 99 mTc-ANC were prepared successfully. The diameter of HAN does not change over 3 months or after mixing with 99 mTc-ANC. The particle size and labelling efficiency of 99 mTc-ANC are not affected by the addition of HAN. Copyright © 2011 John Wiley & Sons, Ltd.