Single Vial Kit Formulation of Technetium-99m-L,L -Ethylene Dicysteine: Its Characterisation, Biodistribution and Comparison with Commercially Available 99mTc-L, L-EC Kits

Protection of the thiol function of L,L-EC by S-thiomethylation allowed automatic deprotection during 99mTc – chelation without the use of any additional reagents. After radiolabeling (either at pH 8.5 or > 8.5), this precursor of L,L- EC produced the desired chelate that was compared to 99mTc L,L-EC, the standard chelate, by HPLC, biodistribution and scintigraphic studies. This led to the development of a single vial kit for 99mTc L,L-EC. The chromatographic and biological properties of this kit were comparable to those of the commercially available EC kits, e.g. TCK-43 and TC-IK-25. This method of chelation from S-thiomethylated precursor has been extended to prepare the corresponding technetium-99 and rhenium chelates. These chelates of the protected ligands were chromatographically (HPLC) and spectroscopically comparable to the corresponding Tc and Re chelates obtained from the unprotected precursor. The results suggest that 99mTc L,L-EC could be prepared from S-thiomethyl EC at pH 8.5 or higher, and this method of chelation could be used for the development of single vial EC kit.