Gold nanolabels for new enhanced chemiluminescence immunoassay of alpha-fetoprotein based on magnetic beads.

Gold'n'beads: A chemiluminescence immunoassay for the sensitive and rapid determination of AFP has been developed, employing bromophenol blue as a novel chemiluminescence enhancer by taking advantages of easy separation by magnetic beads and signal amplification by gold nanoparticles based on a sandwich-type immunoreaction (see scheme).A novel and sensitive chemiluminescence immunoassay (CLIA) has been developed by employing a new chemiluminescence (CL) enhancer, bromophenol blue (BPB), for the determination of alpha-fetoprotein (AFP) based on magnetic beads (MBs) and colloidal gold nanoparticles (AuNPs) modified with HRP-labeled anti-AFP antibodies. BPB, as a chemical indicator, was found to act as a novel and highly signal enhancer of the peroxidase-catalyzed CL reaction of luminol with hydrogen peroxide. After optimizing the CL reaction conditions, this new luminol-H(2)O(2)-HRP-BPB CL system was applied to a sandwich-type CLIA based on the magnetic separation and the amplification feature of AuNPs as HRP labels. A linear range was obtained when the concentrations of AFP were from 0.1 to 5.0 ng mL(-1) (R=0.9997) with the detection limit of 0.01 ng mL(-1) (3sigma), which is one order of magnitude lower than that obtained without using AuNPs, and much lower than that typically achieved by ELISA. The present method was successfully applied to the determination of AFP in human serum samples. The results indicated that this proposed protocol could be quite promising for the application in immunoassays.