Reverse-micelle synthesis of electrochemically encoded quantum dot barcodes: application to electronic coding of a cancer marker.

Reproducible electrochemically encoded quantum dot (QD) barcodes were prepared using the reverse-micelle synthetic approach. The encoding elements, Zn(2+), Cd(2+), and Pb(2+), were confined within a single QD, which eliminates the cumbersome encapsulation process used by other common nanoparticle-based barcode preparation schemes. The distinct voltammetric stripping patterns of Zn(2+), Cd(2+) and Pb(2+) at distinguishable potentials with controllable current intensities offer excellent encoding capability for the prepared electrochemical (EC) QDs. Additionally, the simultaneous modification of the QD barcode surface with organic ligands during the preparation process make them potentially useful in biomedical research. For proof of concept of their application in bioassays, the EC QD barcodes were further employed as tags for an immunoassay of a cancer marker, carcinoembryonic antigen (CEA). The voltammetric stripping response of the dissolved bardcode tags was proportional to log[CEA] in the range from 0.01 to 80 ng mL(-1), with a detection limit of 3.3 pg mL(-1). The synthesized EC QD barcodes hold considerable potential in biodetection, encrypted information, and product tracking.