Monolayers antibody-antigene

Hapten monolayer electrode sensor assembly was used to detect triazine in a flow injection analysis mode. The interaction of the electrode with different antibody concentrations resulted in the formation of an antibody-antigen (Ab-Ag) complex which insulated the electrode towards the [Fe(CN)6] /Fe(CN)6] " redox probe and diis in turn resulted in no charge transfer. The extent of insulation depends on the antibody concentration and the time of exposure to the antibody solution. The decrease in amperometric response of the antigenic monolayer to corresponding antibody solution for a fixed time produces a quantitative measurement of the antibody concentration. Typical responses obtained for cyanazine-hapten monolayer electrode to different antibody concentrations is shown in Figure 4. The lowest detection limit achieved for cyanazine sensor was 4.0 pg/ml at a response time of few minutes and a less-than 2% cross-reactivity to atrazine, simazine and other metabolites. 

Polymer-coated microelectrodes containing one or several monolayers fabricated by electropolymerization of thiophene, bithiophene and 3-methylthiophene at low potential with a low counterion content or with low afiinity ions, can be readily exchanged by ion-exchange technique by proteins, antibodies, antigens and drugs in order to immobilize these molecules [217]. 

I. Vikholm, E. Gyorvary, and J. Peltonen, Incorporation of lipid-tagged single-chain antibodies into lipid monolayers and the interaction with antigen. Langmuir 12, 3276-3281 (1996). 

R. Blonder, E. Katz, Y. Cohen, N. Itzhak, A. Riklin, and I. Willner, Application of redox enzymes for probing the antigen—antibody association at monolayer interfaces development of amperometric immunosensor electrodes. Anal. Chem. 68, 3151—3157 (1996). 

An ordered antibody array has also been assembled on the solid surface by a combination of Langmuir Blodgett (LB) film method and self-assembling method. An ordered monolayer of protein A is deposited on the solid surface by LB method, which is followed by self-assembling of antibody. Individual antigen molecules which are complexed with the antibody array have been quantitated selectively by atomic force microscopy (AFM). 

Fig.34 Schematic procedure of the Prot. A monolayer film on water, followed by self-assembling of antibody and antigen...

FIGURE 5.26. Antigen-antibody construction of a monolayer glucose oxidase electrode with an attached ferrocenium cosuhstrate and cyclic voltammetric response in a phosphate buffer (pH 8) at 25°C and a scan rate of 0.04 V/s. a Attached ferrocene alone, h Addition of the substrate, c Primary plots, d Secondary plot. The numbers on the curves in parts h and c are the values of the substrate concentration in mM. Adapted from Figure 2 in reference 24, with permission from the American Chemical Society. 

Still with an enzyme monolayer, the synthesis and current responses of a system that involves simultaneous attachment of the cosubstrate to the electrode coating are then described. The next step consists in constructing a multilayered coating constituted by successive layers of enzyme built thanks to antigen-antibody interactions. Sensing the diffusion of the cosubstrate through the film thus constructed provides evidence for spatial order and an estimate of the distances between layers. 

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