Polyaniline/Polyaniline Nanocomposites As Signal Amplification Tags For Sensitive Electrochemical Immunoassay

Immunoassay, based on the antigen-antibody specific recognition interactions, has become one of the predominant analytical techniques for the detection of biomolecules in clinical diagnosis, environment and food because it not only shortens the assay time, but also shows great sensitivity, specificity, and stability. Electrochemical immunoassay gains increasing interest due to their high sensitivity and simple equipments. Herein, we demonstrate a few electrochemical immunoassay strategies for the detection of carcinoembryonic antibody (CEA), thyroid-stimulating hormone (TSH) and immunoglobulin G (IgG) as matrices by using polyaniline/polyaniline nanocomposites as signal amplification tags. The thesis includes four chapters as follows:The first chapter mainly includes the contents as follows:(1) the electrochemical immunosensor and its development; (2) tumor marker; (3) polyaniline/polyaniline nanocomposites and their application in the electrochemical immunoassay.The second chapter constructs a new homogeneous immunoassay strategy coupling with a home-made flow-through magneto-controlled microfluidic device by using anti-CEA-conjugated core-shell gold-Fe3O4 nanocomposites as immunosensing probes and MPANFs and HRP as molecular tags, for the determination of CEA. Under optimal conditions, the dynamic concentration range spanned from 1.0 pg mL-1 to 50 ng mL-1 and the detection limit was 0.1 pg mL-1 CEA.The third chapter reports that nanogold-polyaniline-nanogold microspheres (GPGs), as a novel class of molecular tags, was synthesized and functionalized with horseradish peroxidase-conjugated thyroid-stimulating hormone antibody for sensitive electrochemical immunoassay of thyroid-stimulating hormone (TSH). The electrochemical immunoassay exhibited a wide dynamic range from 0.01 to 20 μIU mL-1 with a detection limit (LOD) of 0.005 μIU mL-1 TSH.The fourth chapter devises a redox-active nanocatalyst, Au(Ⅲ)-promoted polyaniline gold nanosphere (GPGS) as molecular tags for highly efficient electrochemical immunoassay of human IgG. Gold nanoparticals can catalyze the reduction of p-nitrophenol (NP) to p-aminophenol (AP) in the presence of NaBH4. Then the produced AP molecules can be oxidized to p-quinone imine (QI) with the help of polyaniline, which can be reduced again to AP via NaBH4. The catalytic recycling resulted in the amplification of the electrochemical signal. A linear dependence between the peak currents and the logarithm of IgG was obtained in the range from 0.01 pg mL-1 to 100 ng mL-1 with a detection limit (LOD) of 1.0 fg mL-1.