Amperometric immunosensor for the determination of α-1-fetoprotein based on multiwalled carbon nanotube-silver nanoparticle composite.

A new amperometric immunosensor for the determination of α-1-fetoprotein (AFP) has been constructed. First, a multiwalled carbon nanotube-silver (MWNT-Ag) composite was modified on the surface of a glassy carbon electrode. Then, chitosan-MnO(2) (CS-MnO(2)) with excellent film forming ability was dipped onto the MWNT-Ag-modified electrode. Subsequently, gold nanoparticles were electrodeposited on the electrode to immobilize anti-AFP. The assembly processes were characterized with cyclic voltammetry, electrochemical impedance spectroscopy, and scanning electron microscopy. MWNT-Ag composite was characterized by transmission electron microscopy, X-ray photoelectron spectroscopy, and UV-vis spectroscopy. The system was optimized to realize a reliable determination of AFP in the range of 0.25-250 ng/ml with a detection limit of 0.08 ng/ml (S/N=3). The proposed immunosensor showed a rapid and highly sensitive amperometric response to AFP with acceptable stability and reproducibility.