Electrochemiluminescence of CdSe quantum dots for highly sensitive competitive immunosensing

A competitive immunosensor using CdSe quantum dots (QDs) as a label was highly proposed for the detection of a tumor marker. CdSe QDs were characterized by transmission electron microscope image, photoluminescence spectra and ultraviolet–visible absorption spectra. The fabrication process of the immunosensor was traced with electrochemical impedance spectra. Using α-fetoprotein (AFP) as a model, a simple electrochemiluminescence immunosensing platform based on CdSe QDs using competitive binding between conjugated antibody-CdSe QDs and free AFP with immobilized AFP on Au electrode was developed. Under the optimum conditions, the proposed electrochemiluminescence method could detect AFP ranging from 0.05 to 100   μg/L with a detection limit of 0.005   μg/L. The proposed immunosensor showed good analytical performance and was successfully applied to detecting level of AFP in human serum samples, which would provide a new and promising direction for clinical application.