Technetium-99m labeling of a molecule bearing easily reducible groups.
Chemical stability of the naphthol-azo dye Evans Blue (EB) was examined in the presence of acidic stannous chloride (SnCl(2)), with a view to preparing an instant cold kit. EB was found to be reactive toward this reducing agent, yielding the metal-chelating molecule 1,7-diamino-8-naphthol-2,4-disulfonic acid at high acidity and high stannous concentrations. This reduction reaction was undesirable in the cold kit preparation. The conditions were determined where reduction was inhibited, at pH = 5.0 and with a mole ratio of EB to SnCl(2) = [10:1], effecting the facile preparation of stable cold kits. Successful (99m)Tc-labeling of an EB cold kit using these conditions resulted in the desired product with 98% radiochemical purity. Based on the radiolabeling efficiencies of chosen model compounds, it was rationalized that (99m)Tc metal predominantly coordinated with the 1-amino-8-hydroxy groups in the EB molecule to form (99m)Tc-EB.
Tsopelas
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Royal Adelaide Hospital Radiopharmacy, Nuclear Medicine Department, South, Adelaide, Australia. ctsopela@mail.rah.sa.gov.au
D002614:Chelating Agents / Q000737:chemistry; D004396:Coloring Agents / Q000737:chemistry; D005070:Evans Blue / Q000737:chemistry; D007202:Indicators and Reagents; D007553:Isotope Labeling; D015609:Organotechnetium Compounds / Q000138:chemical synthesis* / Q000737:chemistry; D010084:Oxidation-Reduction; D011786:Quality Control; D019275:Radiopharmaceuticals / Q000138:chemical synthesis* / Q000737:chemistry; D011933:Reagent Kits, Diagnostic; D017971:Tin Compounds / Q000737:chemistry
D002614:Chelating Agents; D004396:Coloring Agents; D007202:Indicators and Reagents; D015609:Organotechnetium Compounds; D019275:Radiopharmaceuticals; D011933:Reagent Kits, Diagnostic; D017971:Tin Compounds; C023599:stannous chloride; D005070:Evans Blue