Electrochemical immunoassay of carcinoembryonic antigen based on a lead sulfidenanoparticle label

Abstract

We describe a lead sulfide nanoparticle (PbS NP)-based electrochemical immunoassay todetect a tumor biomarker, carcinoembryonic antigen (CEA). Cubic PbS NPswere prepared and functionalized with thioglycolic acid (TGA), which stabilizedthe formed NPs and offered carboxyl groups to conjugate with CEA antibodies.PbS NP conjugated with monoclonal CEA antibody was used as a label in animmunorecognition event. After a complete sandwich immunoreaction among the primaryCEA antibody (immobilized on the carboxyl-modified magnetic beads), CEA and thePbS-labeled secondary antibody (PbS-anti-CEA), PbS labels were captured to themagnetic-bead (MB) surface through the antibody–antigen immunocomplex.Electrochemical stripping analysis of the captured PbS was used to quantify theconcentration of CEA after an acid-dissolution step. The MBs and the magneticseparation platform were used to integrate a facile antibody immobilization withimmunoreactions and the isolation of immunocomplexes from reaction solutions inthe immunoassay. The voltammetric response is highly linear over the range of1–50 ng ml−1 CEA, and the limit of detection is estimated to be0.5 ng ml−1. The performance of this nanoparticle-based electrochemical immunoassay was successfullyevaluated with human serum spiked with CEA, indicating that this convenient andsensitive technique offers great promise for rapid, simple and cost-effective analysis oftumor biomarkers in biological fluids.