An electrochemical immunosensor for the tumor marker α-fetoprotein using a glassy carbon electrode modified with a poly(5-formylindole), single-wall carbon nanotubes, and coated with gold nanoparticles and antibody

We report on a label-free electrochemical immunosensor for alpha-fetoprotein (alpha-FP). It is based on the use of a glassy carbon electrode that was first modified with conducting poly(5-formylindole) and single-walled carbon nanotubes (P5FIn/SWNTs), and then coated with gold nanoparticles and the respective antibody. The presence of aldehyde groups warrants direct immobilization of the antibody and results in a convenient method for fabricating of the immunosensor. Gold nanoparticles (GNPs) were deposited on the P5FIn/SWNTs composite material, and the modified electrode was applied to the detection of alpha-FP. The analytical signal is obtained by measuring the change of amperometric response at a typical working voltage of 100 mV before and after the immunoreaction. The detection limit is 200 fg mL(-1). The immunosensor is simple, sensitive, specific and reproducible. It has the potential for reliable point-of-care diagnosis of tumor or other diseases.