Organometallic Complexes for SPECT Imaging and/or Radionuclide Therapy

Abstract

This article reviews Re and Tc organometallic chemistry and radiochemistry, focusing on the most relevant aspects to design radiotools for molecular imaging and therapy. The review comprises an overview of organometallic Re and Tc complexes with relevance to the field, particularly M(I) tricarbonyl complexes stabilized by a huge variety of ligands. These include Werner type chelators, cyclopentadienyls, carboranes, and poly(mercaptoazolyl)borates, which permitted the hitherto unprecedented use of M–C and M–H bonds. The most relevant biomolecules labeled with the different organometallic cores will also be reviewed, as well as the opportunities offered by the tricarbonyl approach to design high-performance perfusion agents.

fac‐[Re(H2O)3(CO)3]+ Complexed with Histidine and Imidazole in Aqueous Solution: Speciation, Affinity and Binding Features

“…Technetium(I) and Rhenium(I) compounds, especially the aqueous complexes, have recently assumed an important role for diagnostic and therapeutic applications . In particular, the development of a one‐pot synthetic procedure to prepare in mild conditions organometallic M(I)‐tricarbonyl complexes (M=Tc or Re) has stimulated a growing interest towards these compounds for the applications in nuclear medicine.…”

“…In particular, the development of a one‐pot synthetic procedure to prepare in mild conditions organometallic M(I)‐tricarbonyl complexes (M=Tc or Re) has stimulated a growing interest towards these compounds for the applications in nuclear medicine. Radiopharmaceuticals based on 99m Tc(I)‐tricarbonyl complexes have been widely explored as imaging agents, whereas 186 Re(I) and 188 Re(I) compounds have been mainly investigated for therapeutic purposes . Furthermore, the spectral properties of Rhenium(I) tricarbonyl complexes have been exploited in fluorescence microscopy…”

“…In fact, the three water molecules can be replaced by ligands to obtain very stable d 6 low‐spin complexes . Ligands possessing coordinating N, P, O, S atoms have been described, demonstrating that sp 2 nitrogens, as found in aromatic heterocycles, have a better affinity for the metal‐carbonyl fac‐[M(CO) 3 ] + core …”

“…High stable complexes can be obtained using ligands able to replace all three water molecules . These compounds will be more stable to trans‐chelation reactions, as occurring in vivo, and avoid the generation of free metal.…”

Synthesis of tripeptide derivatized cyclopentadienyl complexes of technetium and rhenium as radiopharmaceutical probes

“…somatostatin derivatives for neuroendocrine tumours, other promising candidates such as neuropeptide Y (NPY), c(RCDyK), c(RCDfK), Lys3-BBN, monocyte chemotactic peptide-1 and MG (minigastrin) are amongst the subjects of current preclinical evaluation. 8,9 Small, synthetic, receptor-binding peptides are excellent vectors for specific receptor-imaging, primarily due to the availability of numerous peptides with a broad range of biological activities against many chronic diseases and their favourable pharmacokinetic characteristics, especially combined with their flexibility in chemical modification and radiolabeling. The high binding affinity of a peptide for its receptor induces its retention in receptor over-expressing tissues.…”