Resonance Scattering Spectral Detection of Ultratrace CEA Using Immunonanogold-VC-HAuCl4 Catalytic Reaction

A 10 nm nanogold particle was used to label monoclone CEA antibody to prepare an immunonanogold resonance scattering probe (AuCEAAb) for detection of CEA. In the pH 6.8 Na₂HPO₄-NaH₂PO₄ buffer solution and in the presence of PEG-6000, the immunoreaction between CEA and AuCEAAb took place to form the immunonanogold complex that can be removed by centrifugation technique. The supernatant containing AuCEAAb exhibited catalytic effect on the gold particle reaction of HAuCl₄-VC in the presence of cetyltrimethylammonium bromide (CTMAB). The gold particle exhibited a resonance scattering peak at 600 nm. Using the resonance scattering spectral technology as the detection, a new immunonanogold catalytic resonance scattering method was established to detect CEA. Under the chosen conditions, the resonance scattering intensity at 600 nm (I_{600 nm}) decreased with the CEA concentration increasing. The decreased intensity ΔI_{600 nm} was linear to CEA concentration (C_CEA) in the range of 0.064-3.2 ng·mL^-1, with the regression equation of ΔI_{600 nm} = 32.5 C_CEA + 2.56, correlation coefficient of 0.9945, and detection limit of 0.01 ng·mL^-1. This method was applied to the analysis of CEA in serum samples, with satisfactory results.