A novel label-free immunosensor for detection of VEGF using FFT admittance voltammetry

This study presents a novel, label-free electrochemical immunosensor for the detection of vascular endothelial growth factor (VEGF), a crucial tumor biomarker. The immunosensor was developed by electrochemical deposition of gold nanoparticles-reduced graphene oxide (AuNPs-rGO) nanocomposite on glassy carbon (GC) and screen-printed carbon (SPC) electrodes. A specific monoclonal antibody against VEGF was immobilized on the electrode surface through a carbodiimide coupling reaction. Field Emission Scanning Electron Microscopy (FE-SEM), X-ray Diffraction (XRD), cyclic voltammetry (CV), and electrochemical impedance spectroscopy (EIS) have been used to characterize the developed immunosensor. For quantitative measurement of VEGF, fast Fourier transformation admittance voltammetry was employed by applying a special potential waveform on the immunosensor and sampling the currents. The response was determined by measuring changes in the electrode admittance caused by the adsorption of VEGF molecules, without the use of a redox probe. Under optimal conditions, the immunosensor responses were within a linear detection range for VEGF from 0.1 to 10,000 pg/ml and from 10 to 10,000 pg/ml, with notably low detection limits of 29.1 fg/ml and 352 fg/ml for the modified GC and SPC electrodes, respectively. The sensor exhibits minimal interference from common serum proteins, making it a promising candidate for sensitive, low-cost commercialization.