Potentiometric Immunoassay (PIA)- Mixed Potential Shift by an Antigen/Antibody Reaction

Abstract

This paper presents a method for the direct potentiometric detection of a specific antigen/antibody reaction. The method is based on a principle called "modulation of a mixed potential" at an ionselective electrode (ISE). The ion-selective membrane of an ISE is covered with antibody resp. antigen molecules. A high sensitivity is obtained when the mixed potential is especially unstable which is in general the case if a mixed potential between cations andanionsis built up across the phase boundary ofthe ion-selective membrane towards the sample solution. If the antigen binds to its specific antibody, a directly detectable shift results in the mixed potential. If the "immunoelectrode" is completed by a reference electrode, the corresponding changes of the cell voltage vs. concentration of antigen resp. antibody follows a typical immunological calibration curve. Since no labeled antigen Tesp. antibody molecule is needed, the necessary ISE is simple to construct andthe instrumentation is quite teasonable, PIA will be a very attractive method.