Development of macromolecular Sn(II) complex for preparation of 99Tcm radiopharmaceuticals

Macromolecular Sn(II) complex (R-Sn) was developed using a chelating resin containing aminophosphonic acid groups as a reducing agent of 99Tcm(VII) in the preparation of 99Tcm radiopharmaceuticals. Since Sn(II) was bonded strongly to the resin by chelation, release of Sn from R-Sn was rarely observed in saline solution. 99Tcm labelling with a yield greater than 90% was performed by mixing R-Sn, 99Tcm pertechnetate solution and a ligand, such as human serum albumin and diethylenetriamine pentaacetic acid, for a short time. The 99Tcm radiopharmaceuticals were almost free from Sn(II) and the reducing activity of R-Sn was quite stable despite long-term storage without any special care.