Magnetic electrochemiluminescent immunoassay with quantum dots label for highly efficient detection of the tumor marker α-fetoprotein

A versatile electrochemiluminescent (ECL) immunoassay based on the use of magnetic nanoparticles (MNPs) that act as the carrier for the immobilization of the primary antibody (Ab 1 ) against α-fetoprotein (AFP) has been developed. CdTe quantum dots (QDs) were used to label the same antibody to give a secondary antibody (Ab 2) for use in a sandwich immunoassay. On formation of the MNP-Ab 1 /AFP/QD-Ab 2 sandwich immunocomplex, a strong ECL signal has been obtained at a peak potential of −   1.69   V. The principle of the ECL detection for target AFP was on account of the increment concentration of QD-Ab 2 conjugates after immunoreaction, which resulted in the increase in ECL intensity. The linear response range was between 1.0 and 200   ng   mL −   1 , and the detection limit was 0.32   ng   mL −   1 for the detection model of AFP. The assay was applied to the determination of AFP in serum by the standard addition method. The immunoassay presented here allows for easy separation and purification of AFP, exhibit strong ECL, highly sensitive, well reproducible and precise. In our preception, it has great potential for detecting other proteinic tumor biomarkers.