Study On Electrochemical Immunosensors Based On Signal Amplification Of Nanomaterials

Electrochemical immunosensor plays an important role in pharmaceutical and clinical fields because of the advantages such as fast analysis, good accuracy, high sensitivity and simple detection process. This thesis have developed several methods of signal amplification, and constructed different types of immunosensor based on silver and polyaniline-gold multicomponent nanomaterials.Firstly, the immunosensor based on glassy carbon electrode and silver nanocubes was investigated. The silver nanocubes were prepared by polyol reduction using Na2S as control agent. A simple label-free electrochemical immunosensor was fabricated using chitosan embedding antibody, and the immunocomplex was immobilized on the surface of glassy carbon electrode modified with silver nanocubes. The electrochemical behaviors of the immunosensor were characterized by differential pulse voltammetry (DPV). Under the optimal conditions, the electrochemical immunosensor exhibited excellent analytical performance:the detection range of carcinoembryonic antigen (CEA) was from 0.25 to 150 ng mL-1 with low detection limit of 0.09 ng mL-1 (signal/noise=3). The immunosensor was applied to human serum samples to detect CEA.Then, we constructed an immunosensor based on polyaniline-gold nanomaterials and gold electrode. The polyaniline-gold nanomaterials were synthesized by interface reaction and characterized by scanning electron microscope (SEM) and transmission electron microscopy (TEM). The antibodies were fixed by the host-guest interaction of CM-?-CD and ADA-Ab1. The detection was finished after polyaniline-gold nanoparticles labeled probes reacted with CEA. Good conductivity of polyaniline-gold nanoparticles increased signal intensity response and improved the sensitivity of the sensor. Under optimal conditions, the sensor is linear in the range of 0.50-200 ng mL-1, and the detection limit is 0.20 ng mL-1.Lastly, a sandwich-type electrochemical immunosensor was fabricated based on polyaniline-gold nanoparticles on a gap-based interdigitated electrodes (IDEs). After hydroxylation and amination of IDEs' surface, oriented immobilization of antibodies were further finished through crosslinking reaction and the host-guest interaction. When polyaniline-gold nanoparticles-labeled probes were modified on the surface of electrode, the IDEs were connected to give out increased current signals, and the detection for CEA was achieved. The modification processes of electrode were characterized by contact angle and X-ray photoelectron spectroscopy, atomic force microscopy (AFM) and electrochemical impedance (EIS). The concentration of the cyclodextrin and the dosage of adamantane modified antibody on the influence of the sensor were investigated. The fabricated immunosensor exhibits excellent analytical performance for the detection of CEA with a wide linear range from 0.010 ng mL--1 to 1000 ng mL-1 and low detection limit (0.006 ng mL-1), and provide an enormous application potential for clinical analysis.