Simultaneous detection of five biomarkers of lung cancer by electrochemical immunoassay

Four kinds of redox species including three kinds of polymerized dye-gold composites and one kind of a polyaniline-gold composite were synthesized by a one-pot method at room temperature. Gold in these composites plays the roles of improving the conductivity and fixing the detection antibodies. The four composites together with hexacyanocobaltate were used as redox active species for simultaneous detection of five biomarkers of lung cancer including the carcinoembryonic antigen (CEA), neuron specific enolase (NSE), carbohydrate antigen 125 (CA125), cytokeratin 19 fragment antigen 21–1 (Cyfra21–1), and squamous cell carcinoma antigen (SCCA). The immunoassays display good linear relationship between the current response and the logarithm of the analyte. The analytical ranges extend from 1 to 150 ng⋅mL-1 for CEA, NSE and Cyfra21–1, from 1 to 150 U⋅mL-1 for CA125, and from 0.1 to 100 ng⋅mL-1 for SCCA. The corresponding detection limits are 0.2 ng⋅mL-1, 0.9 ng⋅mL-1, 0.4 ng⋅mL-1, 0.9 U⋅mL-1 and 30 pg⋅mL-1, respectively. The immunoassay was applied to the analysis of human serum samples, and the results were found to agree well with those of the enzyme-linked immunosorbent assay.