Gold nanoparticle-based redox signal enhancement for sensitive detection of human chorionic gonadotropin hormone

A sensitive immunosensor for the detection of pregnancy marker, human chorionic gonadotropin hormone (hCG), was developed using the direct electrical detection of Au nanoparticles. We utilized disposable screen-printed carbon strips (SPCSs) for the development of our immunosensor, which provided cost-effective tests with the required antigen sample volume as small as 2 mu L. After the recognition reaction between the surface -immobilized primary antibody and hCG, the captured antigen was sandwiched with a secondary antibody that was labeled with An nanoparticles. Au nanoparticles were exposed to a preoxidation process at 1.2 V for 40 s, which was subsequently followed with a reduction scan on the same surface using differential pulse voltammetry (DPV). We could observe Au nanoparticle-labeled antigen-antibody complexes immobilized on the surface of SPCS using scanning electron microscopy (SEM). Additionally, the number of An nanoparticles on the immunosensor was determined using SEM images, and showed a linear relationship with the current intensity obtained from the DPV measurements with a detection limit of 36 pg/mL hCG (612 fM, 3.6 x 10(-4) IU/mL). Our immunosensor system, a combination of the screen-printing technology with Au nanoparticles provides a promising biosensor for various applications in life sciences.