Development of a biosensor-based immunoassay for screening of chloramphenicol residues in milk

Biosensor immunoassays were developed recently for antibiotics with an esta blished maximum residue limit (MRL). In this study, according to the regula tory banning of chloramphenicol (CAP) use for food producing animals, the m ain objectives were: the specificity of the biosensor assay and the lowest detection limit possible. The assay was based on the inhibition of the bind ing of polyclonal antibodies against CAP to immobilized CAP on a sensor chi p by CAP in solution. The response varied inversely with the antibiotic con centration in the sample. Two different antibodies and two immobilization p rotocols were tested. As in ELISA tests the antibody influenced the assay p erformances. Moreover, we showed that particular care should be concentrate d on the immobilization step because it is a critical point in the assay de velopment. Three different protocols were developed in milk. The best assay was obtained with antibody 1 in milk on the CAP base surface because of it s very low detection limit (0.1 mug l(-1)) and the decreased consumption of antibody (four times less than on the CAP surface). This assay is rapid (3 min/run), sensitive, and specific for CAP and CAP glucuronide. It could be integrated in a multi-residue screening test and applied to other matrices (bile, urine, meat).