Studies On Electrochemical Immunosensors Based On Inorganic Nanomaterials For α-fetoprotein

The expression of alpha-fetoprotein (a-fetoprotein, AFP) in hepatoma cells is a high specific protein. Many HCC patients (70～80%) in the incubation period have the characteristics of high AFP gene expression. The traditional medical theory holds that high expression of AFP gene is a process of liver cancer associated with the epiphenomenon, and is deemed as a liver cancer-specific tumor marker. It is reported that the AFP extracellular bind to its receptor and mediate the growth of information transfer. Cells within the AFP can not only inhibite the apoptosis signal transduction, but also promote the transmission of growth signals, which display new discoveries of anti-apoptosis and promoting proliferation for AFP, This study have endowed AFP new cognition of functionalization and new target for treating liver cancer.Therefore, the development of new detection methods for detection of AFP is of important theoretical and practical application value.Electrochemical immunosensor is based on the combination of electroanalysis technology and specific immunoreaction. Among various electrochemical immunosensors, the amperometric immunosensor is the most sophisticated because it, avoids separation, washing, realizes easily, and achieves rapid immunoassay compared with other electrochemical immunoassay sensing technology. In our work, we successfully construct amperometric AFP immunosensor by utilizing inorganic nanomaterial for their advantages such as the adsorption ability, the surface with functional group density, short time to reach equilibrium.The prepared immunosensor exhibitmuch easier process and higher sensitivity compared with the traditional method for determination of AFP.The main works and conclusions are as follows:1. An Immunosensor for AFP Antigen Based on Gold Nanoparticles and Titanic Oxide-BSA Composite.Titanic oxide nanoparticles own many advantages compared to conventional materials, such as, non-toxic, excellent electrical properties, good thermal stability, weak moisture absorption and good film-formation. A highly sensitive amperometric immunosensor for the determination of AFP is developed based on the composite of bovine serum albumin (BSA) and TiO2(BSA/TiO2),which is employed to link gold nanoparticles (nano-Au) for the immobilization of anti-AFP. The results show that the immunosensor presents highly sensitivity, good selectivity and a broad liner response from 0.01～80 ng/mL with a detection limit of 0.003 ng/mL.2. Study on the self assembly reagentless amperometric immunosensor based on gold nanoparticles and magnetic nanocomposite.Fe3O4 nanoparticles, a typical magnetic nano-materials, are proved to be easy to separate,be enriched,and extract the advantages of bio-sensors commonly prepared. A new reagentless amperometric immunosensor was successfully fabricated based on theα-fetoprotein antibody (anti-AFP) molecule coupled at Fe3O4@Thionine and gold nanoparticles. Firstly, magnetic nanoparticles and Fe3O4@Thionine Nanoparticles were prepared. Then, Fe3O4@Thionine nanoparticles was assembled on nafion modified glassy carbon electrode via electrostatic adsorption and covalent bonding. Finally, gold nanoparticles were absorbed on the electrode surface for the immobilization of anti-AFP. The proposed immunosensor possessed high sensitivity and good stability. Transmission electron microscopy (TEM) was used to investigate the nanoparticles composite and stepwise fabrication process of the immunosensor is characterized by the cyclic voltammetrys. The results show that, Fe3O4@Thionine modified immunosensor showed a good redox activity, avoiding the adding og electroactive materialsn. Compared with tranditional methods, the proposed nanomaterialsbased immunoassay displays the lower detection limit and the higher sensitivity.3. An Immunosensor for AFP Antigen Based on MCNTS/L-Cysteine and Au@Fe3O4 Nanocomposite.DMF dispersed MWNTS was firstly modified on electrode surface, which was in further eletrodeposited a nano-Au layer for immobilization of L-cysteine. Subsequently,Fe3O4@Au nanocompositeswere absorbed on the modified electrode surface by the SH-Au bond for increasing the specific surface area and further immobilizing anti-AFP. Finally, bovine serum albumin (BSA) was used to block the non-specific adsorption sites of the immunosensor to obtain a highly sensitive and stable immunosensor. Experiments by transmission electron microscopy (TEM) are carried out to characterize the prepared MWNTs and Fe3O4@ Au composite nanoparticles. Compared with the immunosensor based on the gold nanoparticles to immobilizethe antibodies, the proposed method can significantly increase the adsorption capacity of alpha-fetoprotein antibody to improve the sensitivity of immunosensor. Meanwhile, the sensor does not require the preparation of labeled biological molecules.avoid the competition or sandwich reaction and make the experiment easier. Under optimal conditions, the sensor has a good response to AFP. in the detection range of 0.1～150 ng/mL, and detection limit of 0.03 ng/mL.