Open Access

99mTc tricarbonyl glycine monomers, trimers, and pentamers were synthesized and evaluated for their radi-olabeling and in vivo distribution characteristics. We synthesized a 99mTc-tricarbonyl precursor with a low oxidation state (I). 99mTc(CO)3(H2O)3+ was then made to react with monomeric and oligomeric glycine for the development of bifunctional chelating sequences for biomolecules. Labeling yields of 99mTc-tricarbo-nyl glycine monomers and oligomers were checked by high-performance liquid chromatography. The labeling yields of 99mTc-tricarbonyl glycine and glycine oligomers were more than 95%. We evaluated the characteristics of 99mTc-tricarbonyl glycine oligomers by carrying out a lipophilicity test and an imaging study. The octanol-water partition coefficient of 99mTc tricarbonyl glycine oligomers indicated hydrophilic properties. Single-photon emission computed tomography imaging of 99mTc-tricarbonyl glycine oligomers showed rapid renal excretion through the kidneys with a low uptake in the liver, especially of 99mTc tricar-bonyl triglycine. Furthermore, we verified that the addition of triglycine to prototype biomolecules (AGRGDS and RRPYIL) results in the improvement of radiolabeling yield. From these results, we con-clude that triglycine has good characteristics for use as a bifunctional chelating sequence for a 99mTc-tricar-bonyl-based biomolecular imaging probe. Key words: 99mTc-tricarbonyl precursor, Glycine oligomer, Imaging moiety, Biomolecule tracin