Flow injection electrochemical enzyme immunoassay based on the use of goldbands

A flow system for the development of immunoassays, which employs an immunor eactor and an electrochemical detector based on gold bands, was designed. G old is sputtered over Kapton (a polyimide) to form the solid support in whi ch either the immunological interaction or the electronic transference take s 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 rea ction (hydrolysis of naphthylphosphate (NP) by AP) and the immunological in teraction (between IgG-AP and anti-AP) are studied. They are followed by th e amount of naphthol produced. As anti-AP inhibits the enzymatic activity o f AP, a decrease in the signal is observed. The oxidation signals of naphth ol coming either from solutions or from the enzymatic hydrolysis of NP in t he same or different reactors are highly reproducible. (C) 2000 Elsevier Sc ience B.V. All rights reserved.