An ultrasensitive sandwich-type electrochemical immunosensor based on the signal amplification strategy of mesoporous core–shell Pd@Pt nanoparticles/amino group functionalized graphene nanocomposite

Herein, a novel and sensitive sandwich-type electrochemical immunosensor was fabricated for quantitative monitoring of prostate specific antigen (PSA). The sulfo group functionalized multi-walled carbon nanotubes (MWCNTs-SO 3 H) were used as substrate material to increase the specific surface area and enhance the conductivity of the glassy carbon electrode. Gold nanoparticles (Au NPs) were introduced to enhance the load capacity of the substrate material for primary antibodies (Ab 1 ) and accelerate the electron transfer on the electrode interface. The mesoporous core-shell Pd@Pt nanoparticle loaded by amino group functionalized graphene (M-Pd@Pt/NH 2 -GS) with high specific surface area, high indexed facets, and good biocompatibility was not only as the carriers of secondary antibodies (Ab 2 ) but also catalyzed the reduction of hydrogen peroxide (H 2 O 2 ), which effectually amplified the current signal in detection of PSA. The as-proposed immunosensor exhibited high sensitivity and stability on the detection of PSA. A linear relationship between current signals and the concentrations of PSA was obtained in the range from 10   fg/mL to 50   ng/mL and the detection limit of PSA was 3.3   fg/mL (signal-to-noise ratio of 3). Furthermore, the as-proposed immunosensor showed excellent performance in detection of human serum samples. The results suggest that the proposed immunosensor will be promising in the diagnostics application for accurately quantitative detection of PSA.