Quantitative detection of human chorionic gonadotropin antigen via immunogold chromatographic test strips

Abstract

An immunogold chromatographic assay was developed for quantitative determination of human chorionic gonadotropin (HCG) antigen. The monoclonal antibody to beta-HCG antigen (Mab II) conjugated gold nanoparticles (GNPs) were sprayed onto a conjugation pad for specific binding with the target protein to form an immunocomplex. The monoclonal antibody to alfa-HCG antigen (Mab I) was immobilized on the test line (T zone) of the nitrocellulose membrane (NC membrane) to capture the immunocomplex of gold nanoparticle labeled Mab II and HCG protein. Therefore, GNPs would aggregate on the test line of the NC membrane in the presence of HCG, which could be easily distinguished by the naked-eye. As for quantitative detection, the gray value of the red color in the T zone was proportional to the corresponding sample concentration. The gray value versus logarithm concentration curve presented a good linear relationship in the range of 10–600 ng mL⁻¹. The duration of the assay was within 15 min and no professional large-scale analytical instrument was necessary for quantification. When applied in human serum analysis, the strips could reach the requirements of the clinic tests.