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Abstract

An improved electrode assembly is disclosed for use in assaying glucose in solution, e.g., in undiluted whole blood. The assembly includes a sensor electrode and a special overlaying multi-layer membrane that can be sterilized by gamma radiation without reducing the activity of a glucose oxidase enzyme located in an intermediate layer of the membrane. An outer layer of the membrane is formed with microscopic pores having a predetermined density and predetermined size, for reliably controlling the flux of glucose and oxygen from the solution to the intermediate layer, where they react in the presence of the glucose oxidase enzyme to form reactions products that include hydrogen peroxide. The outer layer thus functions as a diffusion barrier, to eliminate the adverse effects of any oxygen deficit that might be present. In addition, an inner layer of the membrane functions as an interference barrier, for controlling the permeation of the hydrogen peroxide reaction product to the underlying electrode. The inner layer includes a relatively thick, porous backing film, formed for example of porous polyester, and a relatively thin, porous overlaying film, formed for example of polysulfone.

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First Claim