Techniques to improve polyurethane membranes for implantable glucose sensors

• US 20060068208A1
• Filed: 11/16/2005
• Published: 03/30/2006
• Est. Priority Date: 05/22/2002
• Status: Abandoned Application

• Current Assignee: DexCom Incorporated
• Original Assignee: DexCom Incorporated
• Inventors: Shults, Mark C., Tapsak, Mark A., Rhodes, Rathbun K., McClure, Jason D.
• Time in patent office: 0 Days
• US Class Current: 428/423.100
• CPC Class Codes: A61B 2562/028 Microscale sensors, e.g. electromechanical sensors [MEMS]
• CPC Class Codes: A61B 2562/125 characterised by the manufacture of electrodes
• CPC Class Codes: A61B 5/14532 for measuring glucose, e.g. by tissue impedance measurement
• CPC Class Codes: A61B 5/1473 invasive, e.g. introduced into the body by a catheter A61B5/1482 takes precedence
• CPC Class Codes: A61B 5/1486 using enzyme electrodes, e.g. with immobilised oxidase
• CPC Class Codes: A61B 5/14865 invasive, e.g. introduced into the body by a catheter or needle or using implanted sensors
• CPC Class Codes: A61L 31/12 Composite materials, i.e. containing one material dispersed in a matrix of the same or different material
• CPC Class Codes: B01D 69/141 Heterogeneous membranes, e.g. containing dispersed material; Mixed matrix membranes
• CPC Class Codes: B01D 71/54 Polyureas; Polyurethanes
• CPC Class Codes: B01D 71/80 Block polymers
• CPC Class Codes: B05D 3/007 After-treatment
• CPC Class Codes: B05D 5/00 Processes for applying liquids or other fluent materials to surfaces to obtain special surface effects, finishes or structures
• CPC Class Codes: C12Q 1/002 Electrode membranes
• CPC Class Codes: C12Q 1/006 for glucose
• CPC Class Codes: Y10T 428/31551 Of polyamidoester [polyurethane, polyisocyanate, polycarbamate, etc.]

Abstract

The invention provides an implantable membrane for regulating the transport of analytes therethrough that includes a matrix including a first polymer; and a second polymer dispersed throughout the matrix, wherein the second polymer forms a network of microdomains which when hydrated are not observable using photomicroscopy at 400× magnification or less. In one aspect, the homogeneous membrane of the present invention has hydrophilic domains dispersed substantially throughout a hydrophobic matrix to provide an optimum balance between oxygen and glucose transport to an electrochemical glucose sensor.

Claims

1. A method of fabricating a device for measuring a concentration of an analyte, the method comprising the steps of:

providing a sensor configured to measure the analyte or a product of a reaction representative of the analyte;

forming a composition comprising a blend of a first polymer and a second polymer, wherein the first polymer is at least partially hydrophilic and the second polymer is at least partially hydrophobic;

maintaining the composition at a temperature sufficient to maintain solubility of the first polymer and the second polymer;

forming a film from the composition at the temperature;

drying the film to form a membrane; and

coupling the membrane to the sensor.

2. The method of claim 1, wherein the first polymer and the second polymer have similar backbone structures.

3. The method of claim 1, wherein the first polymer and the second polymer have miscible backbone structures.

4. The method of claim 1, wherein the first polymer and the second polymer have soluble backbone structures.

5. The method of claim 1, wherein the step of forming a composition comprises forming a physical mixture.

6. The method of claim 1, the step of forming a composition comprises forming a mixture substantially without chemical reaction of the first polymer and the second polymer.

7. The method of claim 1, wherein the step of forming a film comprises casting a film onto a substrate.

8. The method of claim 1, wherein the step of forming a film comprises casting a film onto the sensor.

9. The method of claim 1, wherein the step of maintaining the composition at a temperature comprises heating the composition at a temperature of at least about 70°

C.

10. The method of claim 9, wherein the step of drying the film comprises drying at a temperature of at least about 120°

C.

11. The method of claim 1, wherein the first polymer comprises a substantially hydrophobic homopolymer and the second polymer comprises a hydrophobic-hydrophilic copolymer.

12. The method of claim 1, wherein the first polymer comprises a hydrophobic-hydrophilic copolymer and the second polymer comprises a hydrophobic-hydrophilic copolymer.

13. The method of claim 1, wherein the first polymer comprises a hydrophobic homopolymer and the second polymer comprises a hydrophilic homopolymer.

14. The method of claim 1, wherein the first polymer comprises polyethylene oxide.

15. The method of claim 1, wherein the second polymer comprises polyurethane.

16. The method of claim 1, wherein the second polymer comprises polysiloxane.

17. An implantable sensor formed in accordance with the method of claim 1.

18. A glucose sensor formed in accordance with the method of claim 1.

19. A method for forming a sensor, the method comprising the steps of:

providing a sensor configured to measure an analyte or a product of a reaction representative of the analyte;

forming a composition comprising a matrix comprising a substantially hydrophobic polymer, and a hydrophobic-hydrophilic polymer dispersed throughout the matrix;

maintaining the composition at a temperature sufficient to maintain solubility of the a substantially hydrophobic polymer and the hydrophobic-hydrophilic polymer;

casting a film from the composition at the temperature; and

drying the film to form a membrane.

20. The method of claim 19, further comprising the step of measuring the analyte, wherein the membrane restricts a flux of the analyte through the membrane.

21. The method of claim 20, wherein the sensor comprises an electrochemically reactive surface area, and wherein the analyte substantially uniformly flows through the membrane when the membrane is placed in an aqueous environment.