A dramatically enhanced electrochemiluminescence assay for CA125 based on dendrimer multiply labeled luminol on Fe3O4 nanoparticles

A novel electrochemiluminescence immunosensor for carbohydrate antigen 125 detection based on dendrimer and magnetic nanoparticles were developed in this study. In the assay, carbohydrate antigen 125 was used as a model analyte, and the detection was based on a sandwich structure formed by the first antibody, the carbohydrate antigen 125 and a second antibody labeled with luminol through poly(diethylenetriaminepentaacetic acid-ethylene glycol) ester dendrimer. The sandwich system was then modified on Fe3O4 magnetic nanoparticles and immobilized on a magnetic force-controlled carbon paste electrode with the help of a magnet to form the immunosensor. The result showed that the ECL immunosensor was ultrasensitive to carbohydrate antigen 125 detection at a concentration of 0.2-100 μU/mL with a detection limit of 0.032 μU/mL. The signal was enhanced dramatically than that produced by luminol labeled only, so was the sensitivity of the immunosensor, partly because much more probe molecules could be immobilized on the electrode surface. This also proved that dendrimers could be a useful material for the fabrication of ultrasensitive sensors. The proposed immunosensor was successfully applied to detect CA125 in real human plasma samples, which was compared with the result of conventional ELISA methods.