Experimental biodistribution studies of 99mTc-recombinant human serum albumin (rHSA): a new generation of radiopharmaceutical.

Recombinant human serum albumin (rHSA) produced by cultured fermentation has been prepared in the form of microcapsules nominally 3-5 microns in diameter and radiolabelled with technetium-99m following reduction with stannous chloride. Radiochemical purity was assessed by chromatography on instant thin-layer chromatography and found to be greater than 90%. No evidence of aggregation was seen by microscopic examination. Imaging biodistribution studies in New Zealand white rabbits demonstrated targeting to the liver or lung, respectively, depending upon the size and surfactant properties of the microcapsules. This communication is the first to show scintigraphic studies using 99mTc-labelled rHSA with the potential for lung, liver and cardiovascular imaging and demonstrates that recombinant DNA technology offers an important new source of materials suitable for use as radiopharmaceuticals without the need for pooled human blood products.