Signal amplification in capillary electrophoresis based chemiluminescent immunoassays by using an antibody–gold nanoparticle–DNAzyme assembly

A signal amplification strategy based on antibody–gold nanoparticle–DNAzyme assembly in capillary electrophoresis based chemiluminescent immunoassays (CE-CLIA) was developed. In this CE-CLIA, antibody–AuNP–G-quadruplex/hemin was incubated with limited amount of antigen, and the formed immunocomplex and unreacted antibody–AuNP–G-quadruplex/hemin were then separated by CE and detected by CL. Due to the strong CL catalytic ability of G-quadruplex/hemin DNAzyme and a high loading ratio of DNAzyme on each AuNP, the assay was very sensitive. By taking carbohydrate antigen 19-9 (CA19-9), one of the most important carbohydrate tumor marker as the model analyte, the proposed CE-CLIA method for CA19-9 detection showed a linear range from 0.025 to 1.00 U/mL with a detection limit of 0.016 U/mL (signal/noise=3), which was more sensitive than the methods previously reported for CA19-9 quantification. The method was applied to quantify CA19-9 in human serum samples, and analytical results were in a good agreement with those obtained by using an established ELISA method.