Kinetics of protein binding in solid-phase immunoassays: theory.

In a solid-phase immunoassay, binding between an antigen and its specific antibody takes place at the boundary of a liquid and a solid phase. One of the reactants (receptor) is immobilized on a surface. The other reactant (ligand) is initially free in solution. We present a theory describing the kinetics of immunochemical reaction in such a system. A single essential restriction of the theory is the assumption that the reaction conditions are uniform along the binding surface. In general, the reaction rate as a function of time can be obtained numerically as a solution of a nonlinear integral equation. For some special cases, analytical solutions are available. Various immunoassay geometries are considered, in particular, the case when the reaction is carried out on a microspot.