Flow-injection chemiluminescent immunoassay for alpha-fetoprotein based on epoxysilane modified glass microbeads

A flow-injection chemiluminescent immunoassay system based on a novel transparent immunoaffinity reactor is proposed for the quantitation of alpha-fetoprotein. The reactor prepared with alpha-fetoprotein immobilized epoxysilane modified glass microbeads was used as an immunosensor for chemiluminescent detection. With a non-competitive immunoassay format, the proposed immunosensor system is a low cost, flexible and rapid assay for alpha-fetoprotein. After an off-line incubation of the analyte alpha-fetoprotein with horseradish peroxidase-labeled alpha-fetoprotein antibody as enzyme tracer, the mixture was injected into the reactor, which led to trapping of the free enzyme tracer by the reactor. The trapped enzyme tracer was detected by the p-iodophenol-luminol-H2O2 chemiluminescence system. Under optimal conditions, the decrease in chemiluminescence intensity was proportional to the alpha-fetoprotein concentration in the range of 5.0-100 ng/ml with a detection limit of 2.7 ng/ml at a signal/noise ratio of 3. The immunosensor system showed an acceptable reproducibility and stability. Clinical serum samples were assayed with this method and the results were in acceptable agreement with those obtained from immunoradiometric assay.