Ratiometric ultrasensitive electrochemical immunosensor based on redox substrate and immunoprobe.

Zhongxue Tang,Zhanfang Ma

doi:10.1038/srep35440

Abstract

In this work, we presented a ratiometric electrochemical immunosensor based on redox substrate and immunoprobe. Carboxymethyl cellulose-Au-Pb2+ (CMC-Au-Pb2+) and carbon-Au-Cu2+ (C-Au-Cu2+) nanocomposites were firstly synthesized and implemented as redox substrate and immunoprobe with strong current signals at −0.45 V and 0.15 V, respectively. Human immunoglobulin G (IgG) was used as a model analyte to examine the analytical performance of the proposed method. The current signals of CMC-Au-Pb2+ (Isubstrate) and C-Au-Cu2+ (Iprobe) were monitored. The effect of redox substrate and immunoprobe behaved as a better linear relationship between Iprobe/Isubstrate and Lg CIgG (ng mL−1). By measuring the signal ratio Iprobe/Isubstrate, the sandwich immunosensor for IgG exhibited a wide linear range from 1 fg mL−1 to 100 ng mL−1, which was two orders of magnitude higher than other previous works. The limit of detection reached 0.26 fg mL−1. Furthermore, for human serum samples, the results from this method were consistent with those of the enzyme linked immunosorbent assay (ELISA), demonstrating that the proposed immunoassay was of great potential in clinical diagnosis.

Highlights

In this work, we presented a ratiometric electrochemical immunosensor based on redox substrate and immunoprobe
Transmission electron microscopy (TEM) images revealed that Au nanoparticle (AuNP) about 10 nm in diameter was densely distributed on the as-synthesized carboxymethyl cellulose-Au (CMC-Au) film (Fig. 1A,B and S1A)
Scanning electron microscopy (SEM) images indicated that an even CMC-Au film turned out to be rough after coating Pb2+ (Fig. S1B)

Summary

Introduction

We presented a ratiometric electrochemical immunosensor based on redox substrate and immunoprobe. Some DNA-assisted two-channel ratiometric electrochemical immunoassays have been reported[17,18] In these methods, DNA hybridization was employed, using the redox species-labeled oligonucleotides to functionalize antibodies and substrate, to monitor the immunoreaction. The DNA-assisted ratiometric electrochemical immunoassay exhibited good reproducibility and sensitivity, the limitation of this approach was that the complex, expensive and time-consuming preparation of the redox species-labeled oligonucleotides and the oligonucleotide-tagged antibodies was involved. If these obstacles were resolved by DNA-free method, the two-channel ratiometric immunoassay will be of great significance in clinical diagnosis

Methods

Results

Conclusion