Preparation of Tc-99m-macroaggregated albumin from recombinant human albumin for lung perfusion imaging

Human serum albumin (HSA) extracted from pooled blood taken from human donors is used in the production of 99mTc-labelled macroaggregated albumin (MAA) for lung perfusion imaging. However, concerns for the safety of blood-derived products due to potential contamination by infective agents (e.g. new variant CJD), make alternative production methods necessary. Recombinant DNA technology is a promising method of albumin production avoiding problems associated with human-derived HSA. This paper presents results comparing MAA prepared from recombinant human albumin (rHA, Recombumin®) (rMAA) with in-house produced HSA MAA (hMAA) and commercially available MAA (cMAA). 99mTc-MAA was prepared using previously published production methods by heating a mixture of albumin and stannous chloride in acetate buffer (pH 5.4) at 70 °C for 20 min. Parameters investigated include aggregate size, radiolabelling efficiency, radiochemical and aggregate stability at 4 °C and in vitro (in whole human blood) at 37 °C and biodistribution studies. Results showed that rMAA could be produced with similar morphology, labelling efficiency and stability to hMAA and cMAA. Our findings confirm that rHA shows significant potential as a direct replacement for HSA in commercially available MAA.