Electrochemical immunoassays were developed for the analysis of HER2-ECD, a cancer biomarker. A sandwich assay was performed using SPCEs modified with (1) gold nanoparticles (AuNP), (2) carboxylic acid-functionalized multiwalled-carbon nanotubes (MWCNT) and AuNP or using (3) carboxylic acid-functionalized magnetic beads. The antibody-antigen interaction was detected using an antibody labelled with alkaline phosphatase and 3-indoxyl phosphate and silver ions as the enzymatic substrate. The signal of the enzymatically generated metallic silver was recorded by linear sweep voltammetry (LSV). The total assay time was 2h20min. The obtained LODs were 8.5 ng/mL for SPCE-AuNP, 0.16 ng/mL for SPCE-MWCNT/AuNP and 2.8 ng/mL for SPCE-MBs.
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