Biotin‐Labeled Electropolymerized Network of Gold Nanoparticles for Amperometric Immunodetection of Human Fibrinogen

Water‐soluble gold nanoparticles (3.1±0.6 nm) with polymerization ability and affinity to streptavidin are prepared by reducing HAuCl 4 in the presence of the capping ligands 2‐mercaptoethanesulfonic acid, biotin–cysteamine, and p ‐aminothiophenol. This colloid, HAuCl 4 , is used to modify gold electrodes by forming a 3D electropolymerized network of bis‐aniline‐cross‐linked nanoparticles on the metal surface. The modified electrode is used as a scaffold for the assembly of an amperometric immunosensor system to detect human fibrinogen. The immunosensor shows excellent analytical characteristics, with a dynamic range of detection between 0.018 and 2.208 μg mL −1 , a detection limit of 4 ng mL −1 , and a half‐maximal inhibitory concentration ( IC 50 ) of 177 ng mL −1 . The immunosensor is markedly stable, retaining full analytical capacity after 45 days of storage at 4 °C.