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

The schematic illustration of stepwise fabrication process of the immunosensor: BSA/anti-AFP/CS–MnO 2/MWNTs–Ag/GCE. 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.