The impact of technetium-99m-radiopharmaceuticals' design on their biological behavior

The coordination has a great and not always predictable impact on the in-vivo behaviour of the small molecule into which the technetium-bearing chelate units is integrated. The different valence state of technetium in the complexes with some ligands changes the properties of these complexes, such as physico-chemical parameters and biological behaviour. The change of their biological behaviour has a great impact on quality of imaging study and on radiation dose to the patient. The results of the labelling of DPD and EHIDA with 99mTc(I) and their biological behaviour, in comparison with the same one for 99mTc(III)-DPD and 99mTc(III)-EHIDA complexes, confirmed that different oxidation state of 99mTc make possible forming variety of complexes with quite a different and unexpected biological behaviour. (author)