A novel label-free electrochemical immunosensor for ultra-sensitively detecting prostate specific antigen based on the enhanced catalytic currents of oxygen reduction catalyzed by core-shell Au@Pt nanocrystals

Herein, bimetallic core-shell Au@Pt nanocrystals (Au@Pt NCs) were prepared by a simple one-pot aqueous method using 2-pyrrolidone-5-carboxylic acid sodium salt (PCA-Na) as a new and green growth-directing agent. The obtained architectures displayed excellent catalytic activity towards oxygen reduction reaction (ORR) compared with commercial Pt/C catalyst. A novel immunosensor was constructed via assembly prostate specific antibody on the surface of Au@Pt NCs. It was found that the ORR currents were significantly suppressed due to the specific antigen-antibody reaction. The ultra-sensitive determination of prostate specific antigen (PSA) was realized on account of the immunocomplex impeding the redox probe accessible to the electrode. The immunosensor exhibited good analytical performance for the assay of PSA with the wide linear range of 0.1 ~ 50 ng mL-1 and low detection limit of 0.018 ng mL-1 (S/N = 3), coupled with the improved stability, reproducibility and selectivity.