A label-free electrochemical immunoassay for IgG detection based on the electron transfer

In this study, a highly selective, label-free electrochemical immunoassay strategy based on the charge transport through the multilayer films associated with the electrocatalytic reduction of Fe(CN)₆]³⁻ is proposed using human immunoglobulin G (human IgG) as the model analyte. The antibody-antigen complex formed on the sensing interface can efficiently induce change of the surface charge characteristics, the conductivity of multilayer film and/or electron transfer distance, resulting in an immunoreaction signal. The current reduction is proportional to the amount of analyte. Under the optimized experimental conditions, the proposed sensing strategy provides a linear dynamic range from 10 to 10⁴ ng mL⁻¹ and a detection limit of 3 ng mL⁻¹, indicating an improved analytical performance. This possibly makes it a potential alternative in bioanalysis of proteins and other molecules.