Studies On Eelectrochemical Immunoelectrode For Detection Of HIgG And α-fetoprotein

Immunoglobulin G(IgG) is one of the most important antibodies in human serum. The content of IgG are nearly 70%— 80% in immunoglobulin, it is a unique immunoglobulin that could get across placenta. IgG plays an important role in protection of human health, which can attack bacterium, virus and toxin, a- fetoprotein in human serum is normally excreted during fetal and neonatal development by the liver, yolksac, and in small amount of this protein produced from intestines and stomach. AFP levels decrease rapidly after birth, and for normal adult, the production of AFP is almost completely switched off and the levels are below 20 ng/mL. The elevated serum AFP to abnormally high values occurs in several malignant diseases, usually including non-seminomatous tesicular cancer and primary hepatocellular carcinoma. Also, elevated serum AFP concentrations have been found in patients with other non-cancerous diseases, such as ataxia telangiectasia, hereditary tyrosinemia, neonatal hyperbilirubinemia, acute viral hepatitis, chronic active hepatitis, and cirrhosis. It is very important in clinic determination.Electrochemical immunosensor has the advantages of immunity technology and electrochemical technology. The detection of the immunoassay is based on the change in the amperometric or potentiometric response before and after antigen-antibody reaction. The shift of response exhibits a linear dependence on the concentration of analytes. This method is highly sensitive, inexpensive, easy-to-use and portable. In this article, we have constructed several immunoelectrodes immobilized antibody onto substrate electrode based on nanoAu and nanoAg particles as matrixes. The detailed materials are shown as follows:1. A highly sensitive potentiometric immunosensor has been developed for fast detection of human IgG based on Nafion, gold nanoparticles and Gelatin as matrixes on platinum disk electrode. The assemble procedure was characterized by cyclic voltammetry and electrochemicalimpedance technique. The detection is based on the change of electric potential before and after the antigen-antibody reaction. Compared with the normal methods, this strategy could allow for antibody immobilized with a higher loading amount and better retained immunoactivity. As a model immunosensor, it successfully detected IgG in the concentration range 5~960 ng/mL with a detection limit of 2.0 ng/mL. Furthermore, there are several distinct advantages such as direct, rapid, simple and without multiple separation-labeling steps2. Gold nanoparticles were electrodeposited on the surface of glass carbon (GC) electrode, then anti-AFP was absorbed by gold nanoparticles to prepare a biosensor. The effect of electrodeposition time and absorption time on the electrochemical behavior of biosensor was studied. Other experimental conditions such as pH and temperature were studied too. The current response of the biosensor is in linear relationship with concentration of AFP in the range of 2 ng/mL ~ 60 ng/mL. This approach has some advantage such as simply, a short response time and a satisfied detection range.3. We report a new type of potentiometric immunosensor for the determination of human IgG. Gelatin-silver film as gentle carrier was used to immobilize anti-IgG on the surface of platinum disk electrode. Glutaraldehyde was employed to improve the character of complex film. The immunoelectrode can maintain bioactivity and the detection of IgG is very sensitively. Tests revealed linearity for hlgG in the response range from 1 to 631 ng/mL with a correlation coefficient of 0.9980. The assay also demonstrates that the immunoelectrode exhibits fast response (< 3 min) and long lifetime (at least 120 days). This immunoelectrode was applied to the determination of hlgG in human serum samples with satisfactory results.4. Polyvinyl chloride (PVC) has proved an especially excellent membrane material for its stability and homogeneous. Nanoparticels has good biocompatibility. These properties are used to immobilize a -fetoprotein (AFP) antibody which was activated previously. The detection of antigen is based on the change on the electric potential before and after the antigen-antibody reaction. Tests revealed linearity for AFP in the response range from 3.2 to 190.5 ng/mL with a limited detection of 1.0 ng/Ml, a correlation coefficient of 0.9951. The assay also demonstrate that the immunosensor exhibits a high level of sensitivity {AE = -45.388 Log [AFP] + 24.78), The proposed electrode was very easy to prepare, low cost and fast response time, good reproducibility, and can be used as detection membrane for AFP one-off.