Production of specific antibodies and development of a non-isotopic immunoassay for carbamazepine by the carbonyl metallo-immunoassay (CMIA) method.

As part of our ongoing work to extend the range of applications of the non-isotopic carbonyl metalloimmunoassay (CMIA), previously developed in our laboratory, we describe here the first CMIA study of carbamazepine. The CMIA method uses a metal carbonyl complex as a non-isotopic tracer, and in this case we chose to employ the dicobalt hexacarbonyl moiety (Co2(CO)6) attached to an alkyne. Two organometallic tracers, 3 and 7, were synthesized, differentiated by the nature and length of the spacer arm of the Co2(CO)6 moiety. Two different coupling methods were subsequently used to synthesize the immunogens 1 and 2, the first one used a carbodiimide, while the second, employed dimethyl adipimidate as coupling agent. Titer values of the antisera obtained by injection of these immunogens into rabbits, were determined by CMIA, using one of the organometallic complexes, 3 or 7, as tracer. Both antisera had higher titer values with the long-chain tracer, 7, than with the short-chain tracer, 3. However these titer values were very different: low for antiserum 1 and high for antiserum 2. The cross-reactivity of antiserum 2 with other antiepileptic drugs was negligible. For competition curves, there was good sensitivity with the antibody 2/3 pairing, while a broad assay range was obtained with antibody 2/7 pairing. These results demonstrate the viability of CMIA as an immunoassay method for carbamazepine, and open the way to development of a simultaneous multiassay by CMIA of the principal antiepileptic drugs.