An ultrasensitive sandwich-type electrochemical immunosensor based on the signal amplification strategy of echinoidea-shaped Au@Ag-Cu2O nanoparticles for prostate specific antigen detection.

Highly sensitive determination of tumor markers plays an important role in early diagnosis of cancer. Herein, a novel and ultrasensitive sandwich-type electrochemical immunosensor was fabricated for quantitative detection of prostate specific antigen (PSA). In this process, gold nanoparticles functionalized nitrogen-doped graphene quantum dots (Au@N-GQDs) was synthesized through a simple and green hydrothermal procedure to enhance conductivity, specific electrode surface area and quantity of immobilized primary antibodies (Ab1). Subsequently, the prepared echinoidea-shaped nanocomposites (Au@Ag-Cu2O) composed of Au@Ag core-shell nanoparticles and disordered cuprous oxide were prepared successfully to label the secondary antibodies (Ab2), which convened the advantages of good biocompatibility and high specific surface area. Because of the synergetic effect present in Au, Ag and Cu2O, the novel nanocomposites exhibited excellent electrocatalytic activity towards the reduction of hydrogen peroxide (H2O2) for the amplified detection of PSA. Therefore, the as-proposed immunosensor for the detection of PSA possessed wide dynamic range from 0.01pg/mL to 100ng/mL with a low detection limit of 0.003pg/mL (S/N = 3). Furthermore, this sandwich-type immunosensor revealed high sensitivity, high selectivity and long-term stability, which had promising application in bioassay analysis.