Nanostructured Electrochemical Immunosensor based on Gold Nanowires for the Detection of Model Protein

Nowadays the demand for new devices capable of accurate, fast, and in situ real-time analyses is growing rapidly in the medical field. These devices could have various applications, such as clinical diagnosis and remote patient monitoring. In this work, an electrochemical immunosensor based on Gold Nanowire (GNWs) was developed for the detection of a model protein. Human immunoglobulin G (H-IgG) was selected as model analyte because of its physical, chemical, and biological features like many other biomarkers. GNWs were obtained through electrochemical template deposition into nanoporous polycarbonate membrane. To achieve the best morphology, various deposition conditions have been analyzed such as deposition time and Au precursor concentration in the deposition bath. The best deposition conditions were selected, ensuring the formation of mechanically stable nanowires. To detect proteins, a sandwich configuration was assembled on the surface of the electrode through several incubation steps. The sandwich configuration consists of a) a primary antibody covalently attached on the electrode surface, b) the antigen to be detected (H-IgG) that is selectively bound by the primary antibody, and c) a secondary labelled antibody. The immunosensor is electrochemically active thanks to the presence of gold nanoparticles (GNPs) tagging the secondary antibody. Given that GNPs catalyze hydrogen evolution reaction, the electrode has been used to measure the current density of the hydrogen evolution, which is indirectly related to the concentration of H-IgG antigens. In this way the calibration curve was constructed obtaining linear range of 1-1000 ng mL-1 with a high sensitivity.