An approach for immunoradiometric assay with metallic radionuclides: gallium-67-deferoxamine-dialdehyde starch-IgG.
Radiogallium (Ga) labeling of an immunoglobulin-G-deferoxamine conjugate (DF-IgG) to a high-specific radioactivity was performed to allow the development of a radiometallic immunoradiometric assay (IRMA) system. To increase the specific radioactivity of Ga-DF-IgG, we used dialdehyde starch (DAS) as a multi-site spacer for the binding of DF to IgG. Six DF molecules bound to each IgG molecule after DAS conjugation. DF-DAS-IgG was then labeled with the previously reported 67Ga labeling solution, producing labeled IgG with a specific radioactivity of 11,766 MBq/mg IgG. Using this method, we labeled an anti-CA125 tumor-associated antigen monoclonal antibody (130-22), allowing the first application of 67Ga-DF-DAS-IgG to an IRMA system. With this system, a higher sensitivity could be obtained than with 125I IRMA. In addition, a very high correlation (r = 0.995) was obtained between serum CA125 levels as determined by 67Ga IRMA and 125I IRMA. Gallium-67-labeled antibodies with a high-specific radioactivity appear to hold promise for use in highly sensitive radioassay systems.
Furukawa
T
T
Department of Hygiene, Kansai Medical University, Moriguchi, Japan.
Fujibayashi
Y
Y
Fukunaga
M
M
Saga
T
T
Endo
K
K
Yokoyama
A
A
D015295:Antigens, Tumor-Associated, Carbohydrate / Q000097:blood; D003676:Deferoxamine / Q000138:chemical synthesis*; D005340:Fibrinogen / Q000138:chemical synthesis*; D005710:Gallium Radioisotopes; D006801:Humans; D007074:Immunoglobulin G / Q000138:chemical synthesis*; D015592:Immunoradiometric Assay / Q000379:methods*; D007553:Isotope Labeling; D013213:Starch / Q000031:analogs & derivatives* / Q000138:chemical synthesis
D015295:Antigens, Tumor-Associated, Carbohydrate; D005710:Gallium Radioisotopes; D007074:Immunoglobulin G; C056464:gallium(67)-deferoxamine-dialdehyde starch-fibrinogen conjugate; D005340:Fibrinogen; D013213:Starch; D003676:Deferoxamine