In this work, we developed a disposable amperometric sandwich-type immunoassay to detect prostate specific antigen (PSA). A self-assembled peptide nanotube (PNT), gold nanoparticle (AuNP) and polyaniline (PANI) composite (PANI/AuNP-PNT) were used to modify a pencil graphite electrode (PGE). Anti-PSA (Abl) was immobilized on the modified electrode (PANI/AuNP-PNT/PGE) to capture PSA. Horseradish peroxidase (HRP) labeled anti-PSA (HRP-Ab2) was used as a tracer antibody. The modified electrodes were characterized with scanning electron microscopy (SEM), thermogravimetric analysis (TGA), energy dispersive X-ray spectroscopy (EDS), transmission electron microscopy (TEM), cyclic voltammetry (CV), and electrochemical impedance spectroscopy (EIS). PSA concentration in phosphate buffer (pH = 7.4) was determined with electro-catalytic reduction of H2O2 on the modified working electrode by using the chronoamperometric method. Limit of detection was found out to be 0.68 ng/mL in a linear range of 1-100 ng/mL with a high regression (R-2 = 0.990). To show the practicality of the modified biosensor in real matrixes, it was successfully applied for the detection of PSA in blood serum samples. The proposed method was also compared with enzyme-linked immunosorbent assay (ELISA) and compatible results were obtained. The developed immunoassay exhibited good reproducibility together with high stability and provides an efficient approach to detect PSA cost-effectively compared to traditional methods. (C) 2017 Elsevier Inc. All rights reserved.