Monoclonal antibody-based flow-through immunosensor for analysis of carbaryl

Immunosensor systems have been developed for the rapid and sensitive determination of pesticides, using the insecticide carbaryl as a model analyte. The systems are based on the principle of heterogenous competitive enzyme immunoassay and used mouse monoclonal anti-carbaryl antibodies either in solution (indirect format) or immobilized (direct format). In both formats, enzyme label (horseradish peroxidase, HRP) and fluorometric detection were employed. In the direct format, antibodies were immobilized on a hydrazide-derivatized agarose gel, and 6-[((1-naphthyloxy)carbonyl)amino]hexanoic acid (CNH hapten) conjugated to HRP was used as the enzyme tracer. The limit detection was 26 ng L-1 (11 min/assay), and the useful life of the sensor was 60-70 cycles. In the indirect format, CNH conjugated to bovine serum albumin was immobilized on an N-hydroxysuccinimide-derivatized agarose gel, and a a rabbit anti-mouse antibody labeled with HRP was used as at secondary immunoreagent. The limit of detection was 284 ng L-1 (17 min/assay), and the useful life of the sensor was 160-200 cycles. The developed methods were applied to the analysis of commercial drinking water and apple juice spiked with carbaryl. Interassay RSD ranged from 9 to 39% in the direct format and from 4 to 28% in the indirect format. Recoveries were between 62 and 109% in the direct format and between 78 and 124% in the indirect format. The results were compared with those obtained by enzyme-linked immunosorbent assay as reference method and indicated the suitability of the immunosensor for quality control in water and food analysis.