Rapid assay of trace ceruloplasmin using an immunonanogold resonance scattering spectral probe.

Nanogold particles of size 15 nm were used to label goat anti-human ceruloplasmin (GCP) to obtain an immunonanogold probe (AuGCP) for ceruloplasmin (CP). In a pH 7.8 citric acid-Na(2)HPO(4) buffer solution and in the presence of polyethylene glycol (PEG), an immunoreaction between AuGCP and CP took place, and the released nanogold particles aggregated to bigger clusters, which caused the resonance scattering (RS) intensity at 552 nm (I(552nm)) to be enhanced greatly. The enhanced intensity DeltaI was proportional to the CP concentration (C(CP)) in the range from 0.0030 to 1.26 microg/mL, with a regress equation of DeltaI = 101.0C(CP) + 1.8, a correlation coefficient of 0.9970, and a detection limit of 1.1 ng/mL CP. This simple and sensitive RS immunoassay was applied to the determination of CP in human plasma, with satisfactory results.