MONOCLONAL ELISA FOR 2,4-DICHLOROPHENOXYACETIC ACID - CHARACTERIZATION OF ANTIBODIES AND ASSAY OPTIMIZATION

Twelve monoclonal antibodies (MAbs) against the widely used herbicide 2,4-D were produced by hybridomas from two fusions of murine myeloma c ells and spleen cells isolated from BALB/c mice immunized with hapten conjugated via the carboxyl group to thyroglobulin. To evaluate the se nsitivity and selectivity of MAbs, competitive indirect ELISA was used . MAb E2/G2 exhibited the highest sensitivity toward 2,4-D (IC50 = 0.8 ng/mL) and a favorable selectivity toward 18 structurally related sub stances. Besides the expected high cross-reactivity with methyl ester 2,4-D (104.8%-), cross-reactivity with MCPA (13.8%) and with 2,4,5-T ( 9.5%) was found. Cross-reactivity with other structural analogs did no t exceed 2.7%. Optimization studies showed that in competitive ELISAs for 2,4-D coating conjugates with hapten densities of 2.3 and 3.3 mol of 2,4-D/mol of BSA were more sensitive than conjugates with hapten de nsities of 15.9 and 26.5 mol of 2,4-D/mol of BSA. The best dose-respon se curves presented in this study were almost linear in the concentrat ion range 0.2-10 ng/mL.