Electrochemical Immunoassay Using Diffusion Layer Dispersion Effect of Electrodes

Diffusion layer dispersed electrodes were presented for application in electrochemical immunoassays. The diffusion layer refers to the region on the electrode surface where concentration gradients occur during the redox reactions of the target analytes. To control the diffusion layer, electrodes of the same area and size were fabricated, and the shape of the diffusion layer was controlled by adjusting each electrode distance. To estimate the properties of the electrodes, cyclic voltammetry (CV) analysis was performed using ferricyanide ([Fe(CN)₆^–3]) and 3,3′5,5′-tetramethylbenzidine (TMB) as a model redox couple. Changes in the diffusion layer shape according to electrode distance were compared through simulation. The redox currents for the target analytes increased as electrode distance increased. These results indicate that even if the electrode shape and area are the same, dispersing the diffusion layer by adjusting the distance between the electrodes can affect the microelectrode characteristics. Finally, the diffusion layer dispersed electrode was applied for the medical diagnosis of the human hepatitis B virus (hHBV) antigen, and the human hepatitis C virus (hHCV) antibody was compared with conventional assay methods, such as TMB-based chromogenic detection.