Integrated electrochemical immunosensor with gold nanoparticles for the determination of progesterone

Integrated immunosensors are based on the spatial integration of the sensing layer and the detection system. In this study, we report an integrated immunosensor to determine progesterone (P4) in bovine serum samples. P4 is a steroidal hormone with a vital role in the maintenance of human and animal health. Therefore, an integrated immunosensor for the determination of P4 based on direct attachment of anti-progesterone monoclonal antibody (mAbP4) on a modified gold disk (Au disk) electrode with gold nanoparticles (AuNP) lodged on a cysteamine (cys) self-assembled monolayer (mAbP4-AuNP-cys-Au disk) is reported. The immunosensor is based on a competitive assay involving P4 labeled with horseradish peroxidase (HRP), which oxidizes pyrocatechol (H2Q), in the presence of hydrogen peroxide (H2O2), to benzoquinone (Q). Its back electrochemical reduction to H2Q is detected on the surface of mAbP4-AuNP-cys-Au disk electrode. Different experimental variables involved in the immunosensor preparation such as the gold nanoparticles loading, the amount of mAbP4 immobilized, and the cysteamine immobilization time were optimized. The calibration curve showed an IC50 of 0.54 ng mL−1, and a detection limit (DL) of 0.08 ng mL−1, with a linear range from 8 × 10−2 to 7 ng mL−1. Good percent relative standard deviations (% RSD) values were obtained for bovine serum samples containing 1 and 10 ng mL−1, i.e., about 6%. The recovery values were 109.6 and 110.1% for 1 and 10 ng mL−1, respectively. The assays are fast, selective and very sensitive. Thus, the immunosensor shows to be a very useful tool to determine P4 in bovine serum samples without any pretreatment.