The Study Of Novel Methods Of Electrochemcial Immunosensor Based On Nanofilm For The Detection Of AFP

Tumor has become a harmful high-risk disease for human health. As a commontumor marker, alpha-fetoprotein(AFP) is internationally recognized and widely usedin many disease supplementary diagnosis, such as hepatocellular carcinoma,reproductive system tumors, and embryonal tumours. Electrochemical sensor, basedon immune response and the overcome of traditional analysis(such as ELISA) limitswhich include low sensitivity, processes high sensitivity, selectivity, low prices, andeasy operation. It has also been applied in clinical medicine and biological fieldbroadly. In recent years, more and more researches about the electrochemicalimmunosensor are developed, and the electrochemical immunosensor has become thehot area of research nationally and internationally.This research proposed thatelectrochemical immunosensor was applied to detect AFP. Therein, the effectiveimmobilization of bio-active substances onto the electrode surface is the key factor forthe electrochemical immunosensor preparations. In this paper, we have constructedthe electrochemical immunosensors to detect AFP with two different methods toprepare the nanofilm to fix antibody on the electrode surface.The results of theresearch were satisfactory.First, the electrode surface was modified with polycalconcarboxylic acid byelectropolymerization in this paper. Then, AFP antibody was immobilized to themodified electrode surface by diimine reagent(EDC+NHS) through activestructure(-COOH). According to antigen antibody reaction, sandwich electrochemicalimmunosensor for the detection of AFP has been constructed. The different modifiedelectrodes were characterized via scanning electron microscopy (SEM),electrochemical impedance spectroscopy(EIS) and cyclic voltammograms(CV). Inaddition, experimental conditions were optimized. The approach shows that theimmunosensor has high sensitivity, good stability and reproducibility. Under optimal conditions，the linear range covered from0.5to200ng mL-1, the detection limit hadbeen as0.5ng mL-1and RSD is2.6%.Furthermore, the electrode surface was modified by chitosan-CNT(CS-CNT)nanocomposites through coating method in this paper. And antibody was immobilizedonto the glassy carbon electrode surface through glutaraldehyde as a cross-linker.According to antigen antibodiy reaction, sandwich electrochemical immunosensor fordetection of AFP has been constructed. The modified electrodes were characterized bythe means of cyclic voltammograms(CV) and the experimental conditions wereoptimized. The approach shows that the immunosensor has high sensitivity, goodselectivity and high stability. Under optimal conditions，the immunosensor is highsensitive to AFP with a detection limit of0.05ng mL-1,the linear range of0.05to20ng mL-1and20to200ng mL-1, moreover RSD is9.6%.Finally,AFP real samples were dectected by both of above different modifyingmethods.Compared with the clinical results, it shows that the relative error of bothmethods were less than10%.In the paper,it indicates that the new methods could beused to detect practical samples accurately.