Ultrasensitive electrochemical immunosensors for clinical immunoassay using gold nanoparticle coated multi-walled carbon nanotubes as labels and horseradish peroxidase as an enhancer

摘要

A novel electrochemical immunosensor for the ultrasensitive detection of ?±-fetoprotein (AFP) is described with the use of a gold nanoparticle/(3-mercaptopropyl) trimethoxysilane modified electrode as a desirable platform and gold nanoparticle functionalized multi-walled carbon nanotube (MWCNT) nanocomposite labeled secondary antibodies (Ab2) as a signal tag. At first, gold nanoparticles (AuNPs) were attached on the MWCNTs surface using poly(diallyldimethylammoniumchloride) (PDDA) as a linkage reagent to obtain AuNPa€“MWCNT nanocomposites. Subsequently, horseradish peroxidase (HRP) and thionine (Thi) labeled secondary antibodies (Thi-Ab2) were used to bind AuNPa€“MWCNT nanocomposites with a high load amount and good biological activity. Moreover, the immunosensor can provide amplified signals because of the increased surface area and biocompatibility of AuNPa€“MWCNT nanocomposites. On the other hand, the AuNP functionalized (3-mercaptopropyl) trimethoxysilanes (MPTS) were used for the biosensor platform to increase the surface area as well as improving the electronic transmission rate to capture a large amount of primary antibodies (Ab1). Thus, amplified signals can be obtained by an electrochemical sandwich immunoassay protocol in the presence of H2O2. The proposed sensing strategy provides a wide linear dynamic range from 0.01 to 50 ng mLa?’1 with a low detection limit of 3 pg mLa?’1 (S/N = 3). Significantly, the developed immunoassay method showed a good stability, selectivity and reproducibility.