Supported protein G on gold electrode: characterization and immunosensor application.

In this work, we study the electrochemical properties of protein layer grafted on gold electrode for C-reactive protein detection. Two CRP-antibody immobilization methods were used: the first method is based on direct physisorption of CRP-antibody onto the gold surface and the second method is based on oriented CRP-antibody with protein G intermediate layer. The two developed immunosensors were tested against CRP antigen in phosphate buffer saline solution and in human plasma. The electrochemical characterization of each immobilized layers was achieved by cyclic voltammetry and impedance spectroscopy. The morphology of the deposited biomolecules was observed by Atomic Force Microscopy and the roughness was measured. Moreover, contact angle measurement was used for wettability studies. The response of the developed immunosensors was reproducible, rapid, and highly stable and a detection limit of 100 fg/mL and 10 pg/mL antigen was observed with and without protein G respectively. The developed immunosensors was used for CRP detection in human plasma.