A label-free electrochemical immunosensor based on Au@Pd/Ag yolk-bimetallic shell nanoparticles and amination graphene for detection of nuclear matrix protein 22

A sensitive label-free electrochemical immunosensor was developed based on Au@Pd/Ag yolk-bimetallic shell nanoparticles (Au@Pd/Ag NPs) and amination graphene (NH2-GS) for the detection of nuclear matrix protein 22 (NMP22). Au@Pd/Ag NPs were loaded on the surface of NH2-GS (NH2-GS/Au@Pd/Ag) by covalent binding between noble metal NPs and amino groups. A glassy carbon electrode (GCE, 4 mm in diameter) was used as the working electrode for the assembly of NPs and NH2-GS. Due to the large specific surface area and excellent electrical conductivity of NH2-GS/Au@Pd/Ag, the electroactivity of K3[Fe(CN)6] as electron transfer mediator was promoted and the amount of NMP22 antibody immobilized was enhanced significantly. Under optimum conditions, the immunosensor exhibited high selectivity and a wide linear range from 0.01 to 18 ng/mL with a detection limit of 3.3 pg/mL. For real sample analysis, the recovery of standard addition was 97.4–99.3% and the relative standard deviation (RSD) was 4.83–7.21%, which indicated that the proposed method exhibited great potential as a reliable technique for the determination of NMP22 for clinical research and diagnostic applications.