An amperometric immunosensor for osteoproteogerin based on gold nanoparticles deposited conducting polymer

An amperometric immunosensor was fabricated for the detection of osteoproteogerin (OPG) by covalently immobilizing a monoclonal OPG antibody (anti-OPG) onto the gold nanoparticles (AuNPs) deposited functionalized conducting polymer (5,2′:5′,2″-terthiophene-3′-carboxylic acid). AuNPs were electrochemically deposited onto the conducting polymer using cyclic voltammetry. The particle size of deposited AuNPs was controlled by varying the scan rate and was characterized by scanning electron microscopy (SEM) and X-ray photoelectron spectroscopy (XPS). The immobilization of anti-OPG was also confirmed using XPS. The principle of immunosensor was based on a competitive immunoassay between free-OPG and labeled-OPG for the active sites of anti-OPG. HRP was used as a label that electrochemically catalyzes the H₂O₂ reduction. The catalytic reduction was monitored amperometrically at −0.4 V vs. Ag/AgCl. The immunosensor showed a linear range between 2.5 and 25 pg/ml and the detection limit was determined to be 2 pg/ml. The proposed immunosensor was successfully applied for real human samples to detect OPG.