Determination of HIgG and anti-HIgG using a single potentiometric immunosensor and two different “competitive methods”: Application to the analysis of globulin G in human serum

A potentiometric immunosensor for the determination of both human immunoglobulin G, HIgG, and anti-human immunoglobulin G was fabricated and characterized. The immunosensor investigated utilized a gaseous diffusion potentiometric electrode for NH3 as transducer. The development of this immunosensor involved the immobilization of human immunoglobulin G (HIgG) on a polymeric membrane overlapping the electrode head. Furthermore, the urease enzyme was used as marker, thus allowing anti-HIgG conjugated with urease to be obtained. Two different polymeric membranes on which HIgG were immobilized, namely “Pall-Biodyne” or “Immobilon”, were also employed alternatively and two different competitive measurement geometries allowed both HIgG and anti-HIgG to be checked using a single potentiometric immunosensor. Lastly applications to the analysis of immunoglobulin G in human serum were implemented and good results were obtained.