A label-free and sensitive impedimetric immunosensor for TNF ? biomarker detection based on epoxysilane-modified disposable ITO-PET electrode

The present study constructed a simple and cost-effective electrochemical immunosensor based on 3-glycidoxypropyltriethoxysilane (GPTES) monolayer coated indium tin oxide-polyethylene terephthalate (ITO-PET) electrode for selective and sensitive determination of Tumour necrosis factor ? (TNF ?) cancer biomarker. GPTES was a well-known surface coupling silane agent which had epoxy groups to bind antibodies. Anti-TNF ? antibodies were chosen as biorecognition elements and they attached covalently on the GPTES modified ITO-PET electrode. Electrochemical determination of immunoreaction between anti-TNF ? antibodies and TNF ? antigens was the basic principle of the proposed immunosensor. The electrochemical characterisation of the designed biosensor was tested with electrochemical impedance spectroscopy (EIS) and cyclic voltammetry (CV) techniques. In addition, the surface morphological characteristics of the ITO-PET electrodes after several modification stages were monitored by scanning electron microscopy (SEM) and atomic force microscopy (AFM) imaging. The analytical success of the proposed immunosensor was tested with respect to linear detection range, detection limit, repeatability, reproducibility, reusability, regeneration and long-term stability. The present biosensor had a wide linear range from 0.01 to 1.5 pg/mL and a low detection limit of 3.1 fg/mL. Finally, the biosensor successfully detected TNF ? cancer biomarker in human serum samples with high recovery ranges.