![]() ![]() Three Ga radionuclides are available for the radiolabeling of biomolecules as potential imaging pharmaceuticals. Ga has two naturally occurring stable isotopes, 69Ga and 71Ga, with 60.11% and 39.89% natural abundance, respectively. 5 These properties led to the development of 68Ga-labeled DOTA-TATE, DOTA-TOC, PSMA-11, and PSMA-617 as commercial and potential PET imaging pharmaceuticals, respectively. Generally, acyclic (HBED-CC) * and macrocyclic polyaminocarboxylates (NOTA and DOTA)* chelating agents have been found to form thermodynamically stable and kinetically inert metal chelates. The design of a Ga-based imaging pharmaceutical involves using a bifunctional chelating agent that (1) is capable of keeping the metal bound to a chelator in the in vivo environment, and (2) conjugates to a receptor-specific biomolecule. Due to the strong affinity of Ga 3+ for hydroxide, it tends to demetallate from its complexes to form soluble Ga(OH) 4 − and has a strong binding affinity toward transferrin. All of the hydrolyzed species, except Ga(OH) 4 −, are insoluble in the aqueous medium. Due to high charge density, Ga 3+ is highly acidic with a pK a of 2.6 and is easily hydrolyzed to Ga(OH) n (where n = 1–4) under even acidic conditions. Electropositive Ga, with the most common and stable oxidation state of +3, 47–62 pm ionic radius, and sluggish water-exchange rate, belongs to group 13 of the periodic table of the elements. 4 Ga was named from the Latin word Gallia for Gaul, the native place of Boisbaudran in France. 3 Four years later, Boisbaudran discovered Ga element from the observation of two violet lines in the spectrum of a material separated from zinc blend. 1, 2 The objective of the present report is to summarize the background and the current status of the production and supply of 68Ga.Īs a history and background, Mendeleev, in 1871, predicted an unknown element, eka-aluminum, in his periodic table and believed that it would be directly below aluminum with 68 atomic mass. In addition, worldwide clinical trials with 68Ga-labeled Prostate-Specific Membrane Antigen (PSMA) target-specific ligands, PSMA-11 and PSMA-617, are ongoing for prostate cancer imaging. For example, 68Ga-labeled somatostatin receptor-specific peptides, DOTA-TATE (NETSPOT) and DOTA-TOC in the United States and DOTA-TOC (SomaKit) in the European Union, are being used successfully for neuroendocrine tumor imaging. ![]() The interest in Gallium-68 ( 68Ga) has increased tremendously in the recent past due to (1) it becoming a routinely used radioisotope in clinical positron emission tomography (PET) imaging facilities around the world, and (2) its coordination chemistry applies to the development of 177Lu-labeled theranostic agents.
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