Binding properties of a monoclonal antibody against the Cry1Ab from <Emphasis Type="Italic">Bacillus Thuringensis</Emphasis> for the development of a capillary electrophoresis competitive immunoassay

Experimental work performed was aimed at the assessment of a competitive capillary electrophoresis immunoassay with laser-induced fluorescence (CEIA-LIF) detection for the determination of the Cry1Ab endotoxin from Bacillus thuringensis. The binding constant of a monoclonal antibody, raised against the insecticide protein Cry1Ab, was determined on a microplate by indirect enzyme-linked immunosorbent assay (ELISA) and compared with that obtained in-capillary under nonequilibrium separation conditions. The two binding constants appear comparable—(5.0 ± 1.2) × 10⁶ M⁻¹ and (9.06 ± 5.7) × 10⁶ M⁻¹—reflecting good preservation of the antibody binding behavior in the capillary electrophoresis format. These results allow use of a calibration curve possible between 0.2 and 150 nM of endotoxin protein, with a limit of detection of 0.5 nM (33 μg L⁻¹). Preliminary recovery experiments on maize extracts spiked with known amounts of Cry1Ab endotoxin also showed promising results in detecting the toxin in complex real matrices.