A new immune resonance scattering spectral assay for trace fibrinogen with gold nanoparticle label

Gold nanoparticles in size of 9.0 nm was prepared by the trisodium citrate and used to label goat anti-human fibrinogen. In the pH 6.2 buffer solution and in the presence of polyethylene glycol (PEG), the immune reaction between gold-labeled goat anti-human fibrinogen and fibrinogen took place and the labeled gold nanoparticles were released from the goat anti-human fibrinogen, and the released gold particles aggregated which leaded the resonance scattering intensity at 560 nm (I560 nm) to enhance greatly. The I560nm is proportional to the fibrinogen concentration in the range from 0.027 to 1.07 μg mL−1. The detection limit is 1.14 ng mL−1. This simple assay was applied to determination of fibrinogen in human plasma, with satisfactory results.