A Rapid and Highly Selective Resonance Scattering Spectral Assay for Trace Carcinoembryonic Antigen

Gold nanoparticles, in size of 10 nm, were used to label monoclonal carcinoembryonic antigen antibody (CEAAb) to obtain an immunonanogold resonance scattering (RS) spectral probe (AuCEAAb) for the measurement of trace carcinoembryonic antigen (CEA). In pH 6.8 Na 2 HPO 4 ‐NaH 2 PO 4 buffer solution and the presence of polyethylene glycol (PEG)‐6000, the AuCEAAb combined with CEA to form the nanogold‐labeled immunocomplex clusters in average size of 227 nm, which exhibited two scattering peaks at about 320 and 581 nm. The enhanced RS intensity at 581 nm (Δ I 581 nm ) is proportional to CEA concentration in the range of 1.0–50.0 ng/mL, with a detection limit (DL) of 0.52 ng/mL. The immunonanogold RS assay was utilized to determine CEA in serum samples with high sensitivity, good selectivity and simplicity.