Comparison of multi-sulfonamide biosensor immunoassays

Three different group-specific anti-sulfonamide antibodies were compared in inhibition assay formats in an optical biosensor (BIACORE 3000) using CM5 sensor chips coated with three different sulfonamide derivatives. The antibodies used were an anti-sulfamethazine monoclonal antibody (Mab) 21C7, the sulfonamide binding protein (SBP) in the Qflex Kit Sulfonamides and a recently developed mutant antibody (M.3.4). Each of these antibodies showed interactions with all 17 sulfonamides tested and one (Mab 21C7) was sensitive for the N4-acetyl metabolites also. The limits of detection of the different sulfonamides in chicken serum varied between 7 and >1000 ng ml¿1 (Mab 21C7), 15 and 340 ng ml¿1 (Qflex) and 4 and 82 ng ml¿1 (Mutant M.3.4). The mutant M.3.4 based assay was found to be the most sensitive towards most of the sulfonamides whereas the Qflex Kit Sulfonamides detected the five sulfonamides registered for application in poultry in The Netherlands within the narrowest measurement range