A reagentless amperometric immunosensor based on gold nanoparticles/thionine/Nafion-membrane-modified gold electrode for determination of α-1-fetoprotein

A conventional three-electrode system is fabricated to prepare a novel modified amperometric immunosensor for rapid determination of alpha-1-fetoprotein (AFP) in human serum. The immunosensor was prepared by entrapping thionine (Thi) into Nation (Nf) to form a composite Thi/Nf membrane, which yield an interface containing amine groups to assemble gold nanoparticles (nano-Au) layer for immobilization of alpha-1-fetoprotein antibody (anti-AFP). The stepwise self-assemble procedure of the immunosensor was further characterized by means of electrochemical impedance spectroscopy (EIS) and cyclic voltammetry (CV). The factors influencing the performance of the resulting immunosensor were studied in detail. After the immunosensor was incubated with AFP at 37 degrees C for 10 min, the CVs current decreased linearly in concentration ranges of AFP from 5.0 to 200.0 ng/mL with a detection limit of 2.4 ng/mL. Moreover, the studied immunosensor exhibited good accuracy, high sensitivity and long-term stability (> 3 months). The proposed method is economical and efficient, making it potentially attractive for clinical immunoassays. (c) 2005 Elsevier B.V. All rights reserved.