Technetium and rhenium: coordination chemistry and nuclear medical applications

Metal-containing peptide nucleic acid conjugates

“…109 Tc has been the most commonly used radioisotope, probably due its ideal radio nuclear properties and the convenient availability from a commercial generator. [143][144][145][146] However, other radio-metals such as 64 Cu or 111 In have also been employed. Of interest for in vivo pharmacokinetics, our groups recently reported the biodistribution studies of a 12-mer PNA bioconjugate labeled with a tricarbonyl 99m Tc complex in Wistar rats.…”

Ligand exchange and complex formation kinetics studied by NMR exemplified on fac-[(CO)3M(H2O)]+ (M=Mn, Tc, Re)

“…Because the majority of compounds that have been labelled with 99m Tc can also be labelled with 186 Re or 188 Re these complexes form couples that can be used for diagnosis (Tc) and therapy (Re) [20]. The three isotopes mentioned can be obtained from generator systems and have a half-life ranging from 6 h ( 99m Tc) to 69 d ( 186 Re) (Table 1) [25,26]. Although no stable isotope of technetium exists its chemistry can be performed without severe radiation protection because the most stable isotope, 99 Tc, has a half-life of 2.11 × 10 5 years and is a weak ␤ − emitter without accompanying ␥-radiation.…”

“…This permits the handling of small amounts of 99 Tc in normal glassware like NMR tubes, since the ␤ − particles are shielded by even thin walls. Secondary X-rays become important only with larger amounts of 99 Tc [26]. Rhenium is found in nature as a mixture of two isotopes, 185 Re, which is stable, and 187 Re, which is a weak ␤ − emitter with a very long half-life of 4.35 × 10 10 years ( Table 1).…”

Polyester Dendrimers

“…This group was interested in the preparation of high generations of well-defined and robust Tc is the most commonly used medical isotope in diagnostic medicine due to its ideal half-life (6 h) and γ-energy (140 keV), low dose burden to patients, and the universal availability of low cost 99 Mo/ 99m Tc-generators [206]. A single high-affinity Tc ligand at the core of the dendrimer was desired to ensure that radiolabeling occurs in a well-defined, site-specific manner and at only a single point within the dendrimer skeleton.…”