Glucose oxidase/polyion complex-bilayer membrane for elimination of electroactive interferents in amperometric glucose sensor

An amperometric glucose-sensing electrode was prepared by immobilizing glucose oxidase (GOx) on a polyion complex membrane. First, a monolayer of 3-mercaptopropionic acid (MPA) was made on the surface of a gold electrode by immersing it in an ethanol solution containing MPA. Aqueous solutions of poly-l-lysine and poly-4-styrenesulfonate were successively placed on the electrode surface and allowed to dry. A GOx layer was then formed on the poly-l-lysine/poly-4-styrenesulfonate-complex layer by crosslinking the enzyme by the addition of a glutaraldehyde solution. The polyion complex layer was effective for eliminating electrochemical interferents such as l-ascorbic acid, uric acid and acetaminophen, whereas the hydrogen peroxide produced through the GOx-catalyzed reaction permeated rapidly through the layer. This resulted in a rapid response (100% response in <5 s) with a low interference level (e.g., the ratio of response for l-ascorbic acid to that for the same concentration of glucose was 0.07). The electrode was applied to the assay of glucose in beverages and sera, and could be used for more than two months.