A straightforward way to attach the capture antibody to the vessel surface is by physical adsorption. No special tubes or linking groups are needed. A solution containing the antibody is added to the wells and incubated overnight allowing the antibodies to adsorb to the surface. Some will have their antigen binding site facing upwards being accessible and some will have the antigen binding site hidden. The capture antibody can also be attached through a streptavidin-biotin link. This requires that the capture antibody is biotinylated and that the surface is coated with streptavidin. With this setup the capture antibody can either be attached to the surface before being exposed to the antigen or it can be incubated in the test solution to bind antigen and then immobilized to surface. The assay time with this approach is much shorter than with physical adsorption. Drawback is that streptavidin coated plates are many times more expensive than regular plates.
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