Antibody-Antigen Binding Events: The Effects of Antibody Orientation and Antigen Properties on the Immunoassay Sensitivity

The sensitivity of an immunoassay depends on a complex combination of the physicochemical characteristics of antigens, antibodies, and reaction surfaces, which are the main elements on which the analytical principle of this technique is based. Among these characteristics is possible to include the type of surfaces, the affinity and avidity constants of antibodies, as well as antigen properties. This chapter focuses on the importance of the capturing surface in determining the analytical sensitivity of an immunoassay. It is an established knowledge that the sensitivity of immunoassays is affected by the orientation, the valence, and the spatial distribution of the capturing antibody. In addition, the size and the number of epitopes on the antigens (monovalent or multivalent) can influence the performances of these assays. In this chapter, the authors discuss how the combination of these factors reflects on the sensitivity of immunoassays.