Simultaneous electrochemical immunoassay using CdS/DNA and PbS/DNA nanochains as labels

An electrochemical method for the simultaneous detection of two different tumor markers, carcinoembryonic antigen (CEA) and α-fetoprotein (AFP), in one-pot, using CdS/DNA and PbS/DNA nanochains as labels was developed. Herein, magnetic beads (MBs) as bimolecule immobilizing carriers, were used for co-immobilization of primary anti-CEA and anti-AFP antibodies. The distinguishable signal labels were synthesized by in situ growth of CdS and PbS nanoparticles on DNA chains, respectively, which were further employed to label the corresponding secondary antibodies. A sandwich-type immunoassay format was formed by the biorecognition of the antigens and corresponding antibodies. The assay was based on the peak currents of Cd2+ and Pb2+ dissolved from CdS and PbS nanoparticles by HNO3 using square wave stripping voltammetry. Experimental results show that the multiplexed electrochemical immunoassay has enabled the simultaneous monitoring of CEA and AFP in a single run with wide working ranges of 0.1– 100 ng mL−1 for CEA and 0.5–200 ng mL−1 for AFP. The detection limits reach to 3.3 pg mL−1 for CEA and 7.8 pg mL−1 for AFP.

Highlight
► CdS and PbS QDs/DNA nanochains were prepared by in situ growth method.
► QDs/DNA nanochains were used to label secondary CEA and AFP antibody to amplify the signal.
► The linear shape of DNA can help to reduce the steric hindrance compared to the sphere carriers.
► The protocol enabled the simultaneous monitoring of CEA and AFP in a single run.
► The approach showed wide working ranges and lower detection limits.