Resonance Rayleigh scattering assay for EGFR using antibody immobilized gold nanoparticles

: A highly selectivity determination of epidermal growth factor receptor (EGFR) has been described in the article. Antibody immobilized cysteamine (Cys) functionalized gold nanoparticles (AuNP) were proposed as immunosensors, and resonance Rayleigh scattering (RRS) was used for detection. First, Cys stabilized AuNPs (Cys-AuNP) were prepared by the reduction of chloroauric acid with sodium borohydride in the presence of Cys. Further, anti-EGFR antibody (Cetuximab, C225) was covalently linked to the Cys-AuNP by carbodiimide-mediated amidation protocol to yield the C225-AuNP immunoprobe. The prepared conjugations were characterized by ultraviolet-visible (UV-vis) spectroscopy, transmission electron microscopy (TEM), Fourier transform infrared (FT-IR) and sodium dodecyl sulphate-polyacrylamide gel electrophoresis (SDS-PAGE). Based on the specific binding of C225 to EGFR, an RRS method was established to determine the concentration of EGFR. Under the optimal conditions, the concentration of EGFR was related to the intensity of RRS in the range 30-130 ng ml-1 with a low detection limit of 4.0 ng ml-1 . Meanwhile, the proposed immunosensor exhibited excellent selectivity and anti-interference property. The method was applied to the determination of EGFR in human serum and cancer cell lysate samples with satisfactory results.