An Indirect Perfluorosulfonated Ionomer-Coated Electrochemical Immunosensor for the Detection of the Protein Human Chorionic Gonadotrophin

Abstract

The development of an amperometric immunosensor for the detection of human chorionic gonadotrophin (hCG) is described. In this immunosensor, Nafion was used to immobilize an anti-hCG monoclonal antibody onto a glassy carbon electrode. A systematic study on the effects of experimental parameters such as the quantity of ethanol present in the Nafion solution, the percentage composition of Nafion, the pH of the immobilization buffer, and the concentration of antibody used for entrapment experiments on the binding between the immobilized antibody and 125I-labeled hCG has been carried out. Two immobilization methods, coimmobilization and adsorption immobilization, have then been attempted. A binding of approximately 3% was obtained in the former method, while 5.5% binding was achieved in the latter. On the basis of these results, adsorption immobilization was employed to entrap antibody on the electrode surface. A sandwich assay was then developed for hCG in which the enzyme horseradish peroxidase was conjugated to a second anti-hCG monoclonal antibody. The activity of the enzyme was determined electrochemically by the reduction of benzoquinone to hydroquinone. Binding of hCG to immobilized antibody determines the quantity of enzyme-conjugated antibody at the electrode surface, permitting the quantification of hCG. By a standard additions calibration method of hCG performed in blank human serum samples, the immunosensor exhibits a limit of linearity at 200 mIU mL-1 and a detection limit of 11.2 mIU mL-1 (based on twice the standard deviation of the blank solution).

Gold Nanoparticle‐Based Redox Signal Enhancement for Sensitive Detection of Human Chorionic Gonadotropin Hormone

“…This value was lower than the previously reported ones for the detection of hCG based on the electrochemical detection principles; i.e., 1.4 mIU/mL using HRP-labeled secondary antibody based on the direct electron transfer to the electrode surface [9], 11.2 mIU/mL using HRP-labeled secondary antibody by the reduction of benzoquinone to hydroquinone [47], and nearly equal to the 0.3 mIU/mL using HRP-labeled secondary antibody on an electrode modified with Au nanoparticle/titania sol-gelcomposite membrane [13]. The high sensitivity of our immunosensor was attributed to the combination of the high performance of our SPCSs with high-affinity antibodies and the direct redox-enhanced detection of Au nanoparticles.…”

Gold Nanoparticles Doped Three‐Dimensional Sol‐gel Matrix for Amperometric Human Chorionic Gonadotrophin Immunosensor

“…The proposed detection limit was relatively lower than those of 2 mIU mL À1 [34], 2.5 mIU mL À1 [32], 11.2 mIU mL À1 [13] and 100 mIU mL À1 [46] reported with heterogeneous hCG immunoassays based on electrochemical analytical principle. Thus, the proposed method could be used for detection of low level of hCG in serum sample.…”

“…Compared with the common optical detection methods, electrochemical immunoassays and immunosensors which are useful in the case of point-ofcare testing and in vivo monitoring appear to provide a promising platform with a wide application, especially for determination of clinically important substances [2,8,13], due to the simple and fast analytical process and inexpensive and miniaturizable instrumentation [14,15].…”

High sensitivity DNA detection using gold nanoparticle functionalised polyaniline nanofibres

“…4, the initial current in the absence of any deliberately added enzyme substrate was measured. Following addition of the enzyme substrate, 200 M H 2 O 2 , to the cell (Chetcuti et al, 1999), the system was allowed to equilibrate for 10 min before the current was measured. The electrode response (Williams et al, 2003) is defined as the difference in current before and after the addition of H 2 O 2 .…”