Decoration of Reduced Graphene Oxide Nanosheets with Aryldiazonium Salts and Gold Nanoparticles toward a Label-Free Amperometric Immunosensor for Detecting Cytokine Tumor Necrosis Factor-alpha in Live Cells

摘要

In this study, a label-free electrochemical immunosensor was developed for detection of cytokine tumor necrosis factor-alpha (TNF-alpha). First, AuNPs loaded reduced graphene oxides nanocomposites (RGO-ph-AuNP) were prepared, and then, a mixed layer of 4-carbxyphenyl and 4-aminophenyl phosphorylcholine (PPC) was modified to the surface of AuNPs for the subsequent modification of anti-TNF-alpha capture antibody (Ab(1)) to form the capture surface (Au-RGO-ph-AuNP-ph-PPC(ph-COOH)) for the analyte TNF-alpha with the antifouling property. For reporting the presence of analyte, the anti-TNF-a detection antibody (Ab(2)) was modified to the graphene oxides which have been modified with the 4-ferrocenylaniline through diazonium chemistry to form Ab(2)-GO-ph-Fc. Then, a sandwich assay was formed on gold surfaces for the quantitative detection of TNF-alpha based on the electrochemical signal of ferrocene:X-ray photoelectron spectra (XPS), transmission electron microscopy (TEM), Fourier transform infrared spectroscopy (FT-IR), UV-vis, and electrochemistry were used for characterization of the stepwise fabrications on the interface. The prepared electrochemical immunosensor was successfully used for the detection of TNF-a over the range of 0.1-150 pg mL(-1). The lowest detection limit of this immunosensor is 0.1 pg mL(-1) TNF-alpha in 50 mM phosphate buffer at pH 7.0. The fabricated immunosensor provided high selectivity and stability and can be used to detect TNF-alpha secreted by live BV-2 cells with comparable accuracy to enzyme-linked immunosorbent assay (ELISA) but with lower limit of detection.