A simple, inexpensive, disposable electrochemical sensor for clinical and immuno-assay.

An inexpensive, rapid, disposable electrochemical system has been developed for both clinical and immunochemical assays. The three-electrode planar configuration is produced by silk screening graphite paint on to cardboard. Assays are carried out amperometrically using constant voltage and monitoring current produced by the oxidation of an electron mediator. In the case of immuno-assay the system described uses the enzyme glucose oxidase with 1,4-benzoquinone as the mediator. The assay is carried out by effecting a separation of the bound and free fractions of the immunoreactants via immobilizing the antibodies on to magnetic particles which are magnetically concentrated on the electrode surface for analysis. This concentration of the bound antigen-antibody complex with the glucose oxidase label effectively increases the concentration of the reduced mediator in the electrode vicinity, thus increasing the amperometric response to the bound fraction of the label.