It is a novel method for fac-[188Re(CO)3(H2O)3]+ to radiolabel albumin human serum (IgG) indirectly by the pyridyl-containing bis(2-pyridylmethyl)-amino)-acetic acid (L2H). The results show that radiolabeling efficiency of IgG with 188Re(CO)3-L2H-TFP active ester can be higher than 82% under optimized condition. We studied also the labeling stability over 48 h at 37℃ in 0.9% NaCl or bovine serum albumin with both the labeled products. And it shows that the indirect labeling product (90%) has higher radiochemical purity than the direct labeling product (60%). In summary

the symmetric pyridyl-containing tridentate ligand H2L is a potent bifunctional chelator for the future biomolecules labeling of fac-[188Re(CO)3(H2O)3]+.