Electrochemical immunosensor for the prostate specific antigen detection based on carbon nanotube and gold nanoparticle amplification strategy

We describe a highly sensitive electrochemical sandwich-type immunosensor for the prostate specific antigen (PSA), a biomarker related to prostate cancer. A glassy carbon electrode was covalently modified with multi-walled carbon nanotubes to which the anti-PSA was immobilized. Following addition of a sample containing PSA, a secondary antibody is added that consists of gold nanoparticles modified with secondary antibody and 6-ferrocenyl hexanethiol acting as the signal molecule. This approach represents a multiple signal amplification strategy in that the functionalized carbon nanotubes improve the electron transfer on the surface of the electrode, while the gold nanoparticles act as carriers for capturing large quantities of Ab2 and ferrocene. The modifying processes were characterized by cyclic voltammetry and electrochemical impedance spectroscopy. Under the optimal conditions, the differential pulse voltammetric signals (acquired at a typical potential of 0.31 V vs. SCE) is linearly related to the concentration of PSA in the 10 pg.mL−1 to 100 ng.mL−1 range. The detection limit is 5.4 pg.mL−1. When applied to the determination of PSA in spiked human serum, the recoveries were between 92.4 and 120.0 %. We perceive that this immunosensor holds great promise in the field of clinical screening for cancer biomarkers.