A highly sensitive amperometric immunosensor for the determination of carcinoembryonic antigen (CEA) was developed. In the solution of nano-Pt doped (Pt-CS), multi-wall carbon nanotubes (MWNT) were ultrasonically dispersed to give a multi-wall carbon nanotube-Pt-chitosan composite (MWNT-Pt-CS). Firstly, this composite was modified on a glassy carbon electrode surface, and then thionine was coated onto it. Subsequently, gold nanoparticles (nano-Au) were adsorbed onto the composite surface through the amino groups of thionine and chitosan for immobilizing CEA antibodies. Finally, horseradish peroxidase (HRP) was employed to block the possible remaining active sites of nano-Au layer to avoid the non-specific adsorption. Under the optimized conditions, the response current of the proposed immunosensor decreased linearly in two concentration ranges of CEA from 0.5 to 10 ng/mL and from 10 to 120 ng/mL with a detection limit of 0.2 ng/mL.

Key words: immunosensor, carcinoembryonic antigen, gold nanoparticle, multi-wall carbon nanotube-Pt-chitosan composite