Preparation of Au-Pt nanostructures by combining top-down with bottom-up strategies and application in label-free electrochemical immunosensor for detection of NMP22

A novel label-free amperometric immunosensor for sensitive detection of nuclear matrix protein 22 (NMP22) was developed based on Au-Pt bimetallic nanostructures, which were prepared by combining top-down with bottom-up strategies. Nanoporous gold (NPG) was prepared by “top-down” dealloying of commercial Au/Ag alloy film. After deposition of NPG on an electrode, Pt nanoparticles (PtNPs) were further decorated on NPG by “bottom-up” electrodeposition. The prepared bimetallic nanostructures combine the merits of both NPG and PtNPs, and show a high electrocatalytic activity towards the reduction of H2O2. The label-free immunosensor was constructed by directly immobilizing antibody of NMP22 (anti-NMP22) on the surface of bimetallic nanostructures. The immunoreaction induced amperometric response could be detected and negatively correlated to the concentration of NMP22. Bimetallic nanostructure morphologies and detection conditions were investigated to obtain the best sensing performance. Under the optimal conditions, a linear range from 0.01 ng/mL to 10 ng/mL and a detection limit of 3.33 pg/mL were obtained. The proposed immunosensor showed high sensitivity, good selectivity, stability, reproducibility, and regeneration for the detection of NMP22, and it was evaluated in urine samples, receiving satisfactory results.