Sensitive amperometric immunosensor with improved electrocatalytic Au@Pd urchin-shaped nanostructures for human...

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.