Application of antibody-nanogold-ionic liquid-carbon paste electrode for sensitive electrochemical immunoassay of thyroid-stimulating hormone

A novel electrochemical immunosensor based on carbon paste electrode (CPE) composed of ionic liquid (IL) and graphite was constructed. It demonstrated good efficiency for quick (each test in 30 s) determination of thyroid stimulating hormone (TSH). Electrode surface was modified by gold nanoparticles in order to immobilize of the thyroid stimulating hormone antibody (anti-TSH) on the CPE. The immunoassay structure was established by sandwiching the antigen (TSH) between the thyroid stimulating hormone antibody on the CPE surface modified with gold nanoparticles and the secondary antibody, polyclonal anti-human-TSH labeled with horseradish peroxidase (HRP-labeled anti-TSH). The signal of differential pulse voltammetry (DPV) was used as a basis for the determination of TSH concentration. This signal is generated by the reaction between O-aminophenol (OAP) and H2O2 catalyzed by HRP. The proposed immunosensor is able to measure the concentration of TSH in a linear range between 0.2 and 90.0 ng/mL with a detection limit 0.1 ± 0.02 ng/mL. In addition, high sensitivity and acceptable stability were achieved by this immunosensor which is promising in the clinical assay of TSH.