Studies On Electrochemical Immunosensors Based On Nanomaterials For α-1-fetoprotein, Carcinoembryonic Antigen And Human Chorionic Gonadotrophin

Malignant tumor is attributed to be one of systemic diseasese in Modern Medicine and directly threating the healthy of human. Most kinds of tumors can been cure at the prophase, therefore the detection of tiny tumor marker become very important. Aizawa and his assistants made a kind of amperometric immunosensor for HCG in human blood seurm firstly at 1979. After this work, investigators began to detect others tumor marker as alpha-Fetoprotein (AFP), Carcinoembryonic antigen (CEA), carbohydrate antigen 19-9 (CA19-9), carbohydrate antigen 125 (CA125) and so on. The research of electrochemical immnosensor is most early, multifarious and full-blown in all kinds of immunosenor, usually cooperate with various kinds of electroanalytical technique, such as stripping voltammetry, impulse voltammetry and impulse finite difference method. Electrochemical immnosensor performance highly sensibility and selectivity, simple pretreatment procedure, fast analytical time, lower price and portability and other advantages.In this thesis, we have constructed several immunosensors of detection of AFP, CEA and HCG, based on use various nanomaterals and immobilization methods of biorecognition molecule, such as adsorption, covalence electrostatic interaction, covalent conjunction and electrochemical polymerization.1. A sensitive amperometric immunosensor for alpha-Fetoprotein based on carbon nanotube/DNA/Thi/nano-Au modified glassy carbon electrode.A novel amperometric immunosensor for the determination of alpha-fetoprotein (AFP) was constructed by using films of multi-wall carbon nanotubes/DNA/thionine/gold nanoparticles (nano-Au). Firstly, multi-wall carbon nanotubes (MWCNT) dispersed by PDDA was immobilized on the nano-Au film which was electrochemically deposited on the surface of glassy carbon electrode, then negatively charged DNA film was absorbed on the positively charged Poly (diallydimethlammonium chloride) (PDDA). Subsequently, thionine was held on the electrode via the electrostatic force between positive thionine and the DNA. Finally, the nano-Au was retained on the thionine film for immobilization of AFP antibody (anti-AFP). The modified process was characterized by cyclic voltammetry (CV) and scanning electron microscope (SEM). The factors possibly influenced the performance of the proposed immunosensors were studied in detail. Under optimal conditions, the proposed immunosensor exhibited a good electrochemical behavior to AFP in a two concentration rang of 0.01 to 10.0 ng·mL-1 and from 10.0 to 200.0 ng·mL-1 with a relatively low detection limit of 0.04 ng·mL-1 at 3 times the background noise. Moreover, the selectivity, repeatability and stability of the proposed immunosensor were acceptable.2. Nickel Hexacyanoferrate-Cysteine-Au Nanocomposite Modified Gold electrode for Electrochemical Sensing of Carcinoembryonic antigen.A new highly sensitive amperometric immunosensor for the determination of carcinoembryonic antigen (CEA) is prepared by immobilizing newly synthesized nickel hexacyanoferrate-Cysteine-Au nanocomposites on a gold electrode. The modified process is characterized by cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS). Under optimal conditions, the proposed immunosensor exhibits a wide linear range from 0.05 to 160.0 ng·mL-1 towards CEA with a detection limit of 0.02 ng·mL-1 (S/N=3). The preparation of the proposed biosensor is convenient, and it exhibits high selectivity, long-time stability and good repeatability.3. Nano-Pt conjunctive functionalized carbon nanotube label for amplified immunoanalysisAt first, sulfhydrylation carbon nanotube was obtained by carbon nanotube modified with DNA and thionine gradually. The functionalized CNT was dispersed in hydrochloroplatinic acid and reduced in situ, thus the surface of it will be marked by platinum nanoparticles. Then, the nano-Pt conjunctive functionalized CNT (Pt-CNT) was preparation. Double antibody sandwich method immunosensor been prepared by using bioconjugates featuring horseradish peroxidase (HRP) labels and secondary antibodies (Ab2) linked to Pt-CNT simultaneously. This approach provided a detection limit of 0.005 mIU·mL-1 and the linear range covered from 0.01 to 80.0 mIU·mL Moreover, the immunosensor exhibited high selectivity, good stability.