Fabrication of a simple and sensitive QDs-based electrochemiluminescence immunosensor using a nanostructured composite material for the detection of tumor markers alpha-fetoprotein

A simple and sensitive label-free QDs-based electrochemiluminescence (ECL) immunosensor for detecting tumor markers alpha-fetoprotein is reported. This probe is fabricated using a nanostructured composite material (PICA–MWNT) obtained by the direct electrodeposition of indole-6-carboxylic acid (ICA) monomers and carboxylic groups terminated multiwalled carbon nanotubes (MWNTs) in one step. The obtained composite material, with 2-aminoethanethiol modified CdSe nanoclusters as luminescent particles, has a larger surface area and a considerable amount of functionalized carboxylic acid groups. Thus, QDs/PICA–MWNT will probably display good biocompatibility, high ECL intensity, and stability, which is promising for the enhancement of detection signals and synergistic improvement of sensitivity. The ECL signals are logarithmically linear with the concentration of alpha-fetoprotein in a wide determination range from 0.002 to 2000 ng mL−1, and the corresponding detection limit was 0.4 pg mL−1. This proposed ECL sensor exhibits high stability, good selectivity, and reproducibility, which offers a new insight into the fabrication of immunoassays for detecting other relevant biomarkers, and it has the potential for a reliable point-of-care diagnostics of tumor or other diseases.