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

• An assembly of antibody–AuNP–DNAzyme was designed for signal amplification in CE-CLIA.
• The design was based on the DNAzyme׳s high CL catalytic efficiency on AuNP surface.
• A novel CE-CLIA method was developed for quantifying CA19-9.
• The CE-CLIA method exhibited high sensitivity and selectivity for CA19-9 detection.

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.

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