Gold-silver core-shell nanoparticle-based impedimetric immunosensor for detection of iron homeostasis biomarker hepcidin

An impedimetric immunosensor based on gold-silver core-shell nanoparticles for hepcidin detection is reported. The core-shell nanoparticles were prepared by seed-mediated method and characterized by dynamic light scattering, UV-Vis, XRD, field emission-scanning electron micrograph imaging, energy dispersive spectroscopy, and atomic force microscopy. The immunosensor was fabricated with core-shell nanoparticles and cysteamine employing covalent chemistry (amide bond formation) strategy for ensuring proper orientation of anti-hepcidin antibody on to the amine-functionalized nanomaterial decorated electrodes. The hepcidin detection principle was based on the variation of charge transfer resistance (Delta R-ct) relative to the Fe(CN)(6)(4-/3-) electrochemical probe in the presence of the biomarker. The frequency range was 10(-1) to 10(5) Hz at the scan rate of 10 mV s(-1)and a potential of 0.1 V. Based on the antigen-antibody interaction in 40 min at pH 7.0, a linear relationship between Delta R-ct and hepcidin concentration was obtained in the range 0.01 to 100 ng/mL with a detection limit of 0.857 pg/mL. Furthermore, the designed immunosensor had acceptable reproducibility, stability, selectivity, and reusability. It was successfully applied to the detection of hepcidin in spiked human serum samples and acceptable recovery (90-95.9%) was obtained.