Enzyme-linked immunosorbent assays for rapid and quantitative detection of insecticidal crystal proteins of BT pesticides

Three enzyme-linked immunosorbent assay (ELISA) procedures i.e., one indirect ELISA applied avidin-biotin complex system(ABC-ELISA) and two direct ELISA, antigen captured (AC-ELISA) and double antibody sandwich (DAS-ELISA), were employed to rapidly and quantitatively detect insecticidal crystal proteins (ICPs) from six commercially available BT pesticides by using antiserum against ICPs of Bacillus thuringiensis subsp. kurstaki HD-1. Assay samples treated with 0.1 M NaOH to dissolve ICPS reacted in ELISA more strongly than intact or neutralized ones; The order of sensitivity between the procedures was: ABC-ELISA = DAS-ELISA > AC-ELISA. Reciprocal dilution end points of the BT pesticides detected by ABC-ELISA and DAS-ELISA were 10(5)-10(7) times and the maximum point (10(7) times) was roughly equal to 4-8 ng/ml of ICPs. ABC-ELISA and AC-ELISA showed non-specific reactions to the samples containing the crude sap of homogenized cabbage, though DAS-ELISA did not show any non-specific reactions. BT pesticide residues on cherry fruits were analyzed by ABC-ELISA and bioassay using larvae of diamondback moth. Based on the results, estimations of the residues were almost the same in both methods.