A homogeneous electrogenerated chemiluminescence (ECL) immunoassay for highly sensitive quantification of specific biomarkers based on immunomagnetic beads and homogeneous detection on a magnetic electrode was developed, for the first time. The magnetic electrode is made of a glassy carbon electrode and a series of ring permanent magnets. D-Dimer antigen was taken as a model analyte while biotinylated D-dimer antibody bound on the streptavidin-coated magnetic beads was utilized as a magnetic capture probe and ruthenium complex-labeled D-dimer antibody was employed as an ECL probe. After a fixed amount of magnetic capture probe and the ECL probe was introduced into analyte D-dimer solution, the "sandwich" immunoconjugates on the magnetic beads were formed in tested solution and then magnetically concentrated on the surface of the magnetic electrode. The homogeneous ECL immunoassay for quantification of specific biomarker was directly carried out in the presence of co-reactant tripropylamine. The low detection limit of 1 ng/mL in magnetic enrich time of 2 min and the good magnetic regeneration for the detection of D-dimer were achieved. The magnetic bead shield ECL emission was extensively discussed. This work demonstrates that the homogeneous (separation-free) ECL immunoassay using magnetic beads and magnetic electrode is a promising approach to quantify the biomarkers with high sensitivity and selectivity and in a short time. This approach can be easily extended to ECL and electrochemical biosensing for other biomarkers. Graphical abstract.
Keywords: D-Dimer; Electrogenerated chemiluminescence; Homogeneous immunoassays; Magnetic beads; Magnetic electrode.