Immunoassay detection using functionalized gold nanoparticle probes coupled with resonance Rayleigh scattering

Functionalized gold nanoparticle probes coupling with resonance Rayleigh scattering (RRS) has been developed for the picomolar detection of transferrin. This assay relies on the specific immune recognition of nanoprobe that is modified with anti-transferrin antibody on gold nanoparticle surface through cysteamine bioconjugation. Transmission electron microscopy (TEM), laser light scattering and UV–vis absorption spectroscopy were employed to construct and characterize the nanostructures and spectroscopic characteristics of nanoprobes. Furthermore, the experiment conditions, such as nanoprobe concentration, reaction temperature, incubation time, pH value, salt concentration and coexisting substances, are optimized. The combination of signal amplification of nanoprobes with high sensitivity of RRS technique allow the detection limit of transferrin to reach 85 pM, and the linear detection range from 85 pM to 3.4 nM. This method has been successfully applied to detect transferrin of human serum samples with good reproducibility, and it has the potential of being widely used in clinical diagnosis.