Direct 99mTc labeling of human immunoglobulin with an insoluble macromolecular Sn(II) complex

An insoluble macromolecular Sn(II)(R-Sn) complex which strongly binds Sn(II) by chelation was applied to the direct 99mTc labeling of human immunoglobulin(IgG) to minimize the influence of Sn(II). 99mTc labeling was achieved at greater than 90% yield simply by the short-term mixing of IgGa containing > 2-SH groups per IgG molecule, 99mTc pertechnetate, and the R-Sn complex in pH 7 solution. The 99mTc-IgGa obtained by this labeling method has high stability based on the thiol-specific binding of 99mTc without transchelation from another weakly bound 99mTc-complex.