Serum stability of 67Cu chelates: comparison with 111In and 57Co.
Simple chelates and chelate conjugated monoclonal antibodies labeled with 111In, 57Co and 67Cu demonstrate marked differences in stability when exposed to a serum environment. Among these radiometals, on DTPA, the order of stability is 111In greater than 57Co much greater than 67Cu. On benzyl-EDTA, the order of stability is 111In congruent to 57Co much greater than 67Cu. Among those investigated, the only serum stable 67Cu chelate found was 67Cu-TETA. The order of stability observed for 57Co vs 67Cu is contrary to published equilibrium constants. These in vitro studies suggest that the in vivo behavior of metal chelates exposed to a complex molecular environment may not be predicted by classically determined equilibrium constants.
D000911:Antibodies, Monoclonal; D002614:Chelating Agents; D003037:Cobalt Radioisotopes / Q000097:blood*; D003300:Copper / Q000097:blood*; D004355:Drug Stability; D006801:Humans; D007204:Indium / Q000097:blood*; D004369:Pentetic Acid; D011865:Radioisotope Dilution Technique; D011868:Radioisotopes / Q000097:blood*
D000911:Antibodies, Monoclonal; D002614:Chelating Agents; D003037:Cobalt Radioisotopes; D011868:Radioisotopes; D007204:Indium; D003300:Copper; D004369:Pentetic Acid