Electrochemical immunosensor for highly sensitive and quantitative detection of tumor necrosis factor-α in human serum.

Highly sensitive and selective biosensors for accurate determination of specific protein biomarkers at low levels in serum are a prerequisite for the present healthcare systems. Therefore, here we developed a label-free impedimetric method for tumor necrosis factor-alpha (TNF-α) detection using reduced graphene oxide (RGO) with gold nanoparticles (AuNP) on an indium tin oxide (ITO) microdisk electrodes. The detection mechanism relies on resistance change occurs due to [Fe(CN)6]3-/4- redox probe movement towards the conductive channels of the AuNP-RGO films gated by the recognition of the target biomarker by its anti-TNF-α antibody. The conductivity of the AuNP-RGO structures enhanced by 10-fold in comparison with bare electrode chips. The observed resistance changes at 2Hz (ΔR at 2Hz) enabled the quantification of various concentrations of TNF-α in human serum (CHS-TNF-α). The antibody-adsorbed electrode showed a good increment of resistance change (ΔR) with additions of antigen concentration. The sensor possesses a linear range of 1-1000pg/ml had a detection limit of 0.67pg/ml (38.51fM) and 0.78pg/ml (44.83fM) in PBS and human serum, respectively.