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, alpha CRP-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 (alpha CRP-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 (alpha CRP-Ab) on the modified ITO coated glass electrode surface and on their coupling with protein CRP antigen (alpha CRP-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, alpha CRP-Ab, concentrations in a linear range from 8.5 ng to 9.12 mu g mL(-1) a with a lowest detection limit of 3.5 ng mL(-1) antigen.