IMPROVED SENSITIVITY OF ENZYME-IMMUNOASSAY FOR COCAINE AND BENZOYLECGONINE USING HETEROLOGOUS HAPTEN-ENZYME CONJUGATES

Antibodies for cocaine and benzoylecgonine were prepared by establishe d methods using diazotized 4-aminococaine or 4-aminobenzoylecgonine co njugated to bovine serum albumin as immunogens. Enzyme immunoassay was first developed using diazotized 4-aminococaine or 4-aminobenzoylecog onine conjugated to horseradish peroxidase as the enzyme labels. The I C(50)s of cocaine and benzoylecgonine were 4 ng/ml and 2 ng/ml for the ir respective antibodies. However, the IC(50)s Of cocaine and benzoyle cgonine decreased to 0.4 ng/ml and 0.1 ng/ml respectively when two het erologous haptens, 4-formylcocaine and 4-formyl benzoylecgonine, were synthesized and used for enzyme labeling. The sensitivity of the assay s was considerably improved using the heterologous bridge strategy.