Disposable Electrochemical Immunosensor Based on Dual-Labeled Gold Nanoprobe (Ab-Au-HRP) for Detection of Alpha-Fetoprotein

A disposable electrochemical immunosensor for detection of human alpha-fetoprotein (AFP) has been developed in this study, using monoclonal antibody against AFP and horseradish peroxidase co-modified colloidal gold nanoparticles (Ab-Au-HRP) as trace label and screen-printed carbon electrodes (SPCEs) as signal transducers. The immunosensor was based on a sandwich immunoassay scheme in which the nanoprobe Ab-Au-HRP was dispensed on the polyester membrane as conjugate pad. The other monoclonal antibody against AFP, as capture antibody, was immobilized onto the nitrocellulose membrane which was mounted on the carbon surface of the screen-printed electrodes. An absorbent paper was mounted downstream to draw the sample to successively flow through the conjugate, capture and absorbent pads. The resulting sandwich immune reaction was evaluated by electrochemical detection, through addition of a single-component substrate for HRP. Under optimum conditions, the current value was linearly increased with an increased AFP concentration from 0.5 to 350 ng/mL, at a relatively low detection limit of 0.25 ng/mL at 3 sigma. Excellent analytical performance, fabrication reproducibility and operational stability for the proposed immunosensor indicated its promising application in clinical diagnostics and self-exams.