Duplex voltammetric immunoassay for the cancer biomarkers carcinoembryonic antigen and alpha-fetoprotein by using metal-organic framework probes and a glassy carbon electrode modified with thiolated polyaniline nanofibers

This paper describes stable and highly dispersed aqueous colloids of polyaniline (PANI) nanofibers that were prepared by a chemical method and used to modify a glassy carbon electrode (GCE). The materials combines the good electrical conductivity and network structure of PANI nanofibers with the complexing capacity of mercaptosuccinic acid. The modified GCEs exhibit high sensitivity to Cd(II) and Pb(II) ions, with detection limits of 50 ng.L-1 and 200 ng.L(-)1, respectively. The modified GCE was applied to the simultaneous determination of the cancer biomarkers carcinoembryonic antigen (CEA) and alpha-fetoprotein (AFP) by using particles of metal-organic frameworks (MOFs) prepared from Pb(II) or Cd(I I) and 2-aminoterephthalic acid. The particles are used as electrochemical labels for secondary anti-CEA and secondary anti-AFP antibody in a sandwich assay. The two ions in the MOFs labels on the secondary antibody can be detected best at voltages of -0.63 and -0.88 V (vs Ag/AgCl), respectively. The assay has a linear response in the 0.3 pg.mL(-1) to 3 ng.mL(-1) concentration range of both CEA and AFP, and the respective detection limits are 0.03 pg.mL(-1) and 0.1 pg.mL(-1). In our preception, this assay has a wide scope in that it may be applied to a variety of sandwich types of immunoassays.