In the procurement of stable sup(99m)Tc labeled protein using bifunctional chelating agent

Recently, technetium-99m (sup(99m)Tc) labeling of proteins through the use of a bifunctional chelating agent (BCA) has been reported. In previous work, a BCA containing a di(N-methylthiosemicarbazone) (DTS) moiety for sup(99m)Tc has offered good potential; however, conjugation with bulky proteins has induced some steric interference in the sup(99m)Tc labeling step using the stannous chloride method. In order to minimize this effect, changes in the hydrocarbon chain length (spacer) between the DTS and the protein binding site (carboxyl group), as well as the chemical state of the reducing agent, stannous chloride, were considered of interest. DTS molecules with variable spacer length (n=0,2,4) were synthesized, coupled with human serum albumin and labeled with sup(99m)Tc. Also, stannous chloride prepared in different media was evaluated. Validity of the present approach is tested and discussed. (author)