Epoxy enhanced polymer membrane to increase durability of biosensors
The present invention provides a polymer membrane enhanced with cured epoxy resin for use as the outer membrane of biosensors. The membrane includes approximately 30-80% epoxy resin adhesives, 10-60% polymer such as poly(vinyl chloride), polycarbonate and polyurethane and 0-30% plasticizers and 5-15% surface modifier reagent such as polyethylene oxide-containing block copolymers. Utilizing the polymer membrane of the present invention, a three-layered sensing element has been developed. This sensing element will be particularly useful for miniaturized biosensors used for in vitro blood measurements or for continuous in vivo monitoring such as implantable biosensors. This element includes an enzyme layer, an interference-eliminating layer and the novel polymer member of the present invention as the outer polymer layer. This novel sensing element shows excellent response characteristics in solutions and has an extremely long lifetime. This technology is particularly useful for improving the lifetime of implantable biosensors.
1. A multilayered implantable glucose sensing element comprising:
a core substrate comprising an electrochemically conductive material;
an immobilized glucose oxidase enzyme layer adjacent to and surrounding the surface of the electrochemically conductive material; and
a cured layer of an epoxy resin composition; said cured layer external to and surrounding the immobilized glucose oxidase enzyme layer;
wherein the core substrate and the immobilized glucose oxidase layer are sealed within the sensing element.
2. The glucose sensing element of claim 1 , wherein the enzyme layer is immobilized by a technique selected from the group consisting of electropolymerization, chemical cross-linking and electropolymerization followed by chemical cross-linking.
3. The glucose sensing element of claim 1 , wherein the electrochemically conductive material is selected from the group consisting of gold, platinum and carbon.
4. The glucose sensing element of claim 1 , wherein the epoxy resin composition comprises:
about 10% to about 60% by weight of epoxy resin adhesive;
about 5% to about 15% by weight polyethylene oxide-containing block copolymer; and
about 30% to about 80% by weight of a polymer, other than said epoxy resin adhesive and said polyethylene oxide-containing block copolymer.
5. The glucose sensing element of claim 4 , wherein the epoxy resin composition further comprises up to about 30% by weight of one or more plasticizers.
6. The glucose sensing element of claim 4 , further comprising an interference-eliminating layer between the immobilized glucose oxidase enzyme layer and the cured layer of epoxy resin composition.