Ultrasensitive enhanced chemiluminescence enzyme immunoassay for the determination of alpha-fetoprotein amplified by double-codified gold nanoparticles labels.

A novel enhanced chemiluminescent (CL) immunoassay for ultrasensitive determination of alpha-fetoprotein (AFP) was reported. The method made full use of 4-(4'-iodo)phenylphenol (IPP) as a new potential signal enhancer and double-codified gold nanoparticles (DC-AuNPs) labels modified with horseradish peroxidase (HRP)-conjugated anti-AFP used for further signal amplification. This protocol involved a sandwich format, in which the antigen in the sample was first captured by the immobilized primary antibody on the surface of magnetic beads, and then recognized by the second antibody labeled with DC-AuNPs. The combination of the remarkable sensitivity of the enhanced CL method and the use of AuNPs as an anti-AFP-HRP carrier for the enzymatic signal amplification, provided a linear response range of AFP from 0.008 to 0.3 ng mL(-1) with an extremely low detection limit of 5 pg mL(-1), much lower than those achieved by the classical enzyme-linked immunosorbent assay (ELISA). This new system can be easily extended to a variety of immunodetection as well as DNA analysis.