Flow injection electrochemical enzyme immunoassay based on the use of gold bands Original Research Article

A flow system for the development of immunoassays, which employs an immunoreactor and an electrochemical detector based on gold bands, was designed. Gold is sputtered over Kapton (a polyimide) to form the solid support in which either the immunological interaction or the electronic transference takes place. IgG labelled with alkaline phosphatase (AP) is physically adsorbed on the gold surface of the reactor. The employment of two eight-way valves allows an independent treatment of reactor and detector. The enzymatic reaction (hydrolysis of naphthylphosphate (NP) by AP) and the immunological interaction (between IgG–AP and anti-AP) are studied. They are followed by the amount of naphthol produced. As anti-AP inhibits the enzymatic activity of AP, a decrease in the signal is observed. The oxidation signals of naphthol coming either from solutions or from the enzymatic hydrolysis of NP in the same or different reactors are highly reproducible.