Effect of Tin(II) Chloride Amount on 99mTc-Labeling of One 6-Hydrazinonicotinamide-Conjugated Peptide in the Presence of Tricine/Nicotinic Acid

The use of tin(II) chloride in amount above its required mole ratio as reducing agent can lead to instability of peptide-based radiopharmaceuticals. In this work, we optimize the radiolabeling conditions, especially tin(II) chloride amount for Tc-99m-labeling of one 6-hydrazinonicotinamide (HYNIC) conjugated peptide in the presence of tricine and nicotinic acid (NA). Implementation of this procedure leads to Tc-99m-labeling of this HYNIC-conjugated peptide in high radiochemical yield (>95%). By comparison, our experimental results can provide an efficacious strategy for Tc-99m-labeling of HYNIC-conjugated biomolecules in the presence of tricine/NA. The resulting Tc-99m-labeled peptide, without the need for any chemical modification and pretreatment, shows good stability in saline and human serum. This work can provide a new perspective for Tc-99m-labeling of HYNIC-conjugated biomolecules.