Electrochemical Impedance Immunosensor for the Detection of C-Reactive Protein in Aqueous Solution

A label-free electrochemical impedance immunosensor is reported by immobilizing protein antibody, αCRP-Ab, through a self assembled monolayer (SAM) of 3-aminopropyltriethoxysilane (APTES) using a cross linker, Bis[sulfosuccinimidyl] suberate (BS3), on indium tin oxide (ITO) coated glass electrode. The immunosensor (αCRP-Ab/BS3/APTES/ITOglass) was characterized by scanning electron microscopy (SEM), atomic force microscopy (AFM) and electrochemical techniques. The electrochemical performance of the immunosensor was studied by electrochemical impedance spectroscopy. The results showed an increasing electron-transfer resistance with the immobilization of CRP antibody (αCRP-Ab) on the modified ITO coated glass electrode surface and on their coupling with protein CRP antigen (αCRP-Ag) at the immunosensor surface in the presence of [Fe(CN)6]3−/4− as redox probe. The immunosensor exhibits an electrochemical impedance response to antigen, αCRP-Ab, concentrations in a linear range from 8.5 ng to 9.12 μg mL−1 a with a lowest detection limit of 3.5 ng mL−1 antigen