Phytic acid-based copper(ii) ion-selective electrode on graphene oxide for potentiometric immunoassay of breast cancer antigen 15-3

A potentiometric immunoassay based on a copper(ii) ion-selective electrode (Cu-ISE) was designed for the quantitative determination of carbohydrate antigen 15-3 (CA 15-3; a tumor marker associated with breast cancer). To construct such a Cu-ISE-based assay system, a sandwiched immunoreaction was carried out on a capture antibody-coated microplate by using a cupric oxide (CuO) nanoparticle-labeled detection antibody, whereas the Cu-ISE was prepared on a gold-disk electrode by using phytic acid-functionalized graphene oxide nanosheets as the transducer. Followed by forming the immunocomplexes, the dissolved Cu2+ ions from CuO nanoparticles by acids were specifically chelated with immobilized phytic acid on the electrode because of the highly efficient complexing ability, thereby resulting in a change of the electrode potential. Under optimum conditions, the Cu-ISE-based potentiometric immunosensor yielded a near Nernstian slope (12.01 +/- 0.66 mV dec(-1)) for the detection of CA 15-3 within a dynamic linear range of 0.01-100 U mL(-1) with a low detection limit of 5.3 mU mL(-1). Moreover, the Cu-ISE-based immunoassay showed good reproducibility, high specificity and long-time stability. Furthermore, it was applied for the determination of CA 15-3 in human serum specimens, providing well-matched results in comparison with the referenced CA 15-3 ELISA kit. Importantly, the Cu-ISE-based immunoassay provides a promising alternative for simple and reliable screening of disease-related biomarkers.