Sensitive amperometric immunosensor with improved electrocatalytic Au@Pd urchin-shaped nanostructures for human epididymis specific protein 4 antigen detection.

Sensitive detection of early ovarian cancer is imminent for women's health. Human epididymis specific protein 4 antigen (HE4 Ag), as a novel tumor marker, has good specificity and sensitivity in ovarian cancer markers, especially for the detection of early ovarian cancer. In this work, a novel and ultrasensitive sandwich-type amperometric electrochemical immunosensor was constructed using amine modified graphene supported gold nanorods (Au NRs/NH2-GS) as a sensor platform and core-shell Au@Pd urchin-shaped nanostructures (Au@Pd USs) as a label of the secondary antibodies (Ab2, Au@Pd USs-Ab2) to realize the quantitative determination of HE4 Ag. The Au NRs/NH2-GS were used for increasing the electrode surface area and effectively immobilizing primary antibodies (Ab1) due to its good water-solubility. The Au@Pd USs have special morphology with high crystal surface index and good stability, capable of loading secondary antibodies (Ab2) and providing a larger active site for the catalysis of hydrogen peroxide (H2O2). The proposed immunosensor displays excellent performance for HE4 Ag detection over the range from 1 pmol L-1 to 50 nmol L-1 with a detection limit of 0.33 pmol L-1 (signal-to-noise ratio of 3). Moreover, the designed immunosensor exhibits excellent reproducibility, selectivity, and stability, which shows great potential in clinical diagnosis.