Highly conducting gold nanoparticles–graphene nanohybrid films for ultrasensitive detection of carcinoembryonic antigen

A new label-free amperometric immunosensor was developed for detection of carcinoembryonic antigen (CEA) based on chitosan-ferrocene (CS-Fc) and nano-TiO2 (CS-Fc + TiO2) complex film and gold nanoparticles–graphene (Au–Gra) nanohybrid. CS-Fc + TiO2 composite membrane was first modified on a bare glass carbon electrode. Then Au–Gra nanohybrid was formed on the CS-Fc + TiO2 membrane by self-assembly strategy. Next, further immobilization of anti-CEA was constructed according to the strong interaction between Au–Gra and the amido groups of anti-CEA. Since Au–Gra nanohybrid films provided a congenial microenvironment for the immobilization of biomolecules, the surface coverage of antibody protein could be enhanced and the sensitivity of the immunosensor has been improved. The good electronic conductive characteristic might be attributed to the synergistic effect of graphene nanosheets and Au NPs. The modified process was characterized by scanning electron microscope (SEM) and cyclic voltammetry (CV). Under optimized conditions, the resulting biosensor displayed good amperometric response to CEA with linear range from 0.01 to 80 ng/mL and a detection limit of 3.4 pg/mL (signal/noise = 3). The results demonstrated that the immunosensor has advantages of high conduction, sensitivity, and long life time. This assay approach showed a great potential in clinical applications and detection of low level proteins.