Electrochemical characterization of surface modified gold electrode for the detection of C-reactive protein
ABSTRACT A label-free, electrochemical impedance electrode is reported by immobilizing protein antibody, aCRP-Ab, through a self assembled monolayer (SAM) of 11-mercaptoundecanoic acid (MUA) and 3-mercapto propionic acid (MPA) via carbodiimide coupling reaction using N-(3-dimethylaminopropyl)-N'-ethyl carbodiimide hydrochloride (EDC) and N-Hydroxy Succinimide (NHS) on gold (Au) electrode. The electrode (aCRP-Ab/NHS/MUA/MPA/Au) was characterized by scanning electron microscopy (SEM), Atomic force microscopy (AFM) and electrochemical techniques. The electrochemical performance of the electrode was studied by electrochemical impedance spectroscopy. The results showed an increased electron-transfer resistance with the immobilization of CRP antibody (aCRP-Ab) on the modified Au electrode and on their subsequent coupling with protein CRP antigen (aCRP-Ag) at the electrode surface in the presence of [Fe (CN) 6]3-/4- as redox probe. The modified Au electrode exhibits an electrochemical impedance response to antigen, aCRP-Ag, concentration in a linear range from 45 ng to 5.84 µg/ml with a lowest detection limit of 30 ng/ml.