Chemical and biological evaluation of technetium (I) tricarbonyl complexes with EHIDA and DPD. 99m (I) complexes of EHIDA and DPD.

Background: 99mTc-phosphate and 99mTc-IDA complexes, made by the addition of 99mTcO4- to the kits, have been applied to bone and gallbladder imaging respectively, for many years. In this paper, an effort to label DPD and EHIDA with [99mTc(CO)3(H2O)3]+ was carried out.

Material And Methods: DPD and EHIDA were synthesised and prepared in kit form in INS "Vinca". A carbonyl labelling agent Isolink (Mallinckrodt Medical B.V.) and a carbonyl precursor (NCRS Demokritos) were applied. The samples of each compound were added to a vial containing 99mTc-carbonyl precursor, in which original pH (10/11) was neutralised to a pH of around 5.5 or 7.5, the same one as the pH of the investigated compounds. After heating, the reaction products were analysed by HPLC equipped with UV and g-detector, with TEAP 0.05 M, methanol and water as solvent. The biological evaluation of 99m99mTc(I)-coordinated compounds, as well as 99mTc-DPD and 99mTc-EHIDA complexes, involved a bio distribution examination on Wistar rats.

Results: The results have shown that hydrophilic organometallic [99mTc(CO)3(H2O)3]+ precursor facilitates the formation of Tc (I) complexes with these ligands, based on the tricarbonyltechnetium (I) core. The changes in structure of DPD and EHIDA labelled molecules influenced biological behaviour: 99Tc(CO)3 -DPD did not accumulate in bone (< 1% of the complex was found in the femur), while 99Tc(CO)3-EHIDA has shown slower billiary excretion and faster filtration through the kidneys.

Discussion: The results of the labelling of DPD and EHIDA with [99mTc(CO)3(H2O)3]+ and their chemical and biological behaviour, in comparison with the same one for 99mTc-DPD and 99mTc-EHIDA, confirmed that different oxidation states of technetium make the formation of a variety of complexes with quite different behaviour possible.