Testosterone is an androgenic steroid hormone with anabolic effects, forbidden by the International Olympic Committee and other international sports associations. Doping inspections are usually made by chromatographic methods that need expensive instrumentation and complex sample preparation procedures that decrease analytical efficiency. In this context, the use of electrochemical immunosensors could offer alternative advantages for doping control.
In this work, a disposable electrochemical immunosensor for the detection of testosterone using gold screen-printed electrodes (AuSPEs) and magnetic beads (MBs) modified with protein A, is presented. A competitive immunoassay format involving testosterone labeled with horseradish peroxidase (HRP) was employed. Anti-testosterone antibody was immobilized onto protein A –MBs, and the resulting conjugate was trapped with a small magnet on the surface of a TTF-modified AuSPE. Testoterone determination was made by H2O2 addition, using amperometric detection at -0.15 V vs Ag/AgCl.
All the experimental variables involved in the assay, i.e. the amount of anti-testosterone immobilized or the time of incubation, were optimized. A calibration plot was obtained for testosterone with a linear range between 1 and 100 ng / mL, which covers the concentration levels required for the analysis of biological samples. Reproducibility and stability tests of the immunosensor, together with the cross reactivity profiles of the antibody, have been evaluated. Furthermore, the detection of testosterone in serum and urine is performed with good results.
