An electrochemical immunosensor on a carbon nanofiber/gold nanoparticles platform for the detection of alpha-feto protein cancer biomarker

We report an alpha – fetoprotein (AFP) cancer biomarker electrochemical immunosensor detected on a carbon nanofiber (CNF) and gold nanoparticles (AuNPs) platform. Functionalised carbon nanofiber and gold nanoparticles were immobilised through drop drying and electrodeposition techniques respectively on a glassy carbon electrode (GCE). AFP antibody was immobilised on the platform overnight followed by blocking of nonspecific binding sites with bovine serum albumin (BSA) for 4 h. The AFP antigen was incubated on the platform for 40 min at 35 °C for the antigen – antibody interaction. CNF and AuNPs were characterised by electron microscopy and Fourier transform infrared (FTIR) spectroscopy. The modified electrodes and the immunosensor were characterised by cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS) techniques. The electrochemical response of the GCE/CNF/AuNPs electrode and the resulting immunosensor was significantly enhanced by the nanocomposite of CNF and AuNPs. The electrochemical immunosensing measurement for AFP was carried out under optimal conditions at a concentration range from 0.005 to 500 ng mL⁻¹ in 5 mM ferri/ferrocyanide solution. A low limit of detection of 0.50 pg mL⁻¹ from square wave voltammetry (SWV) and 0.48 pg mL⁻¹ from EIS measurements were obtained. The immunosensor exhibited good sensitivity, good selectivity, good repeatability, and was stable at 4 °C over a period of three weeks.