A Label-free Immunosensor Based on K[Fe(CN)] and Aldehyde-Functionalized Pyridinium

A novel aldehyde-functionalized pyridinium was successfully synthesized. Using K[Fe(CN)] as a redox species modified on the surface of the electrode through Poly(diallyldimethylammonium chloride), we developed a label-free immunosensor based on aldehyde-functionalized pyridinium that was applied to simplify antibody immobilization on the electrode surface, in which no additional chemical cross-linking was required. In addition, the introduction of K[Fe(CN)] on the surface of electrode avoided the use of other redox species in the electrolyte solution. Under the optimal experimental conditions, differential pulse voltammetry (DPV) signals corresponding to different α-Fetoprotein (AFP) concentrations were measured. After antigens with different concentrations reacted with antibodies immobilized on the electrode surface, the peak current of DPV gradually decreased with increasing concentrations of AFP. The calibration curve showed a good linear relation in the range from 0.01 to 20 ng·mL with the linear regression equation of y = -3.23x + 22.42 (R=0.9943). The detection limit is 0.004 ng·mL based on a signal-to-noise ratio of 3. The constructed immunosensor is simple, label-free and specific, thus, provides a good diagnostic tool for detection of α-Fetoprotein and other cancer markers.