Acridinium esters as high-specific-activity labels in immunoassay

Abstract

A chemiluminescent acridinium ester has been synthesized that reacts spontaneously with proteins to yield stable, immunoreactive derivatives of high specific activity. The compound has been used to prepare chemiluminescent monoclonal antibodies to human α1-fetoprotein having average incorporation ratios as great as 2.8 mol of label per mole of antibody, which corresponds to a detection limit of approximately 8 x 10-19 mol. These antibodies have been used in the preliminary development of a two-site immunochemiluminometric assay for human α1-fetoprotein, which requires only a 30-min incubation and a quantification time of 5 s per sample.