Acrylic copolymer membranes for biosensors

• US 5,476,094 A
• Filed: 11/15/1993
• Issued: 12/19/1995
• Est. Priority Date: 02/11/1992
• Status: Expired due to Term

• Current Assignee: Disetronic Licensing Ag (Roche Holding AG)
• Original Assignee: Eli Lilly and Company
• Inventors: Nevin, Robert S., Allen, Douglas J.
• Primary Examiner(s): Sykes, Angela D.
• Application Number:
  US08/152,185
• Time in Patent Office: 764 Days
• Field of Search: 128/632-636, 128/637, 204/403, 204/415, 204/153.1, 204/153.12, 204/153.16-153.17
• US Class Current: 600/342
• CPC Class Codes: B01D 71/401 Polymers based on the polymerisation of acrylic acid, e.g. polyacrylate
• CPC Class Codes: B01D 71/76 Macromolecular material not specifically provided for in a single one of groups B01D71/08 - B01D71/74 rubbers in general B01D71/24
• CPC Class Codes: C12Q 1/002 Electrode membranes

Abstract

Homogeneous membranes are disclosed which are composed of acrylic copolymers and are capable of absorbing 10% to 50% of their dry weight of water. The copolymers include a hydrophilic component which comprises acrylic esters having a poly(ethylene oxide) substituent as part of the alcohol moiety. The copolymers further comprise methacrylate and/or acrylate monomer units. The membranes are useful in the fabrication of biosensors, e.g., a glucose sensor, intended for in vivo use. Variations in the ratios of the monomeric components make possible the fabrication of membranes which have varying permeabilities.

Claims

1. A homogeneous membrane adapted for use on a biosensor having sensor elements for evaluating the presence of an analyte, said membrane being for enclosing the sensor elements, said membrane comprising:

an acrylic copolymer including first monomer units consisting of an acrylic ester having a poly(ethylene oxide) substituent as part of the alcohol moiety, and second monomer units selected from methacrylates, acrylates and combinations thereof, said membrane absorbing about 10% to about 50% of its dry weight of water.

2. The membrane of claim 1 in which said second monomer units comprise methyl methacrylate.

3. The membrane of claim 1 in which said second monomer units comprise ethyl acrylate.

4. The membrane of claim 3 in which said second monomer units further comprise methyl methacrylate.

5. The membrane of claim 1 in which said membrane absorbs about 15% to about 25% of its dry weight of water.

6. The membrane of claim 1 in which the poly(ethylene oxide) substituent has an average molecular weight of from about 200 to about 2000.

7. The membrane of claim 6 in which said membrane absorbs about 15% to about 25% of its dry weight of water.

8. The membrane of claim 6 in which the poly(ethylene oxide) substituent has an average molecular weight of about 1000.

9. The membrane of claim 8 in which said poly(ethylene oxide) substituent comprises methoxy poly(ethylene oxide) methacrylate.

10. The membrane of claim 1 in which said membrane is adapted for use on an electrochemical glucose sensor, and in which said membrane has a ratio of its diffusion coefficient for oxygen to its diffusion coefficient for glucose of up to about 4000.

11. The membrane of claim 10 in which said composition absorbs about 15% to about 25% of its dry weight of water.

12. The membrane of claim 10 in which the poly(ethylene oxide) substituent has an average molecular weight of from about 200 to about 2000.

13. The membrane of claim 10 in which the diffusion ratio for said composition is about 2500 to about 3500.

14. The membrane of claim 13 in which said membrane absorbs about 15% to about 25% of its dry weight of water.

15. The membrane of claim 13 in which the poly(ethylene oxide) substituent has an average molecular weight of from about 200 to about 2000.

16. The membrane of claim 15 in which said membrane absorbs about 15% to about 25% of its dry weight of water.

17. In an implantable device for determining the level of an analyte in a body, said device comprising a biosensor having sensor elements for evaluating the presence of the analyte and including a membrane enclosing the sensor elements, said membrane providing biocompatibility, protection of the sensor elements from the surrounding biological environment, and control of diffusion of materials to the sensor elements, the improvement comprising forming said membrane from an acrylic copolymer comprising first monomer units consisting of an acrylic ester having a poly(ethylene oxide) substituent as part of the alcohol moiety, and second monomer units selected from methacrylates, acrylates and combinations thereof, said membrane absorbing about 10% to about 50% of its dry weight of water.

18. The improvement of claim 17 in which said second monomer units comprise methyl methacrylate.

19. The improvement of claim 17 in which said second monomer units comprise ethyl acrylate.

20. The improvement of claim 19 in which said second monomer units further comprise methyl methacrylate.

21. The improvement of claim 17 in which said membrane absorbs about 15% to about 25% of its dry weight of water.

22. The improvement of claim 17 in which the poly(ethylene oxide) substituent has an average molecular weight of from about 200 to about 2000.

23. The improvement of claim 22 in which the poly(ethylene oxide) substituent has an average molecular weight of about 1000.

24. The improvement of claim 17 in which said biosensor is an electrochemical glucose sensor, said membrane controlling the diffusion of oxygen and glucose to the sensor elements, said membrane having a ratio of its diffusion coefficient for oxygen to its diffusion coefficient for glucose of up to about 4000.

25. The membrane of claim 24 in which the diffusion ratio for said composition is about 2500 to about 3500.

26. The membrane of claim 24 in which said composition absorbs about 15% to about 25% of its dry weight of water.

27. The membrane of claim 24 in which the poly(ethylene oxide) substituent has an average molecular weight of from about 200 to about 2000.

28. The membrane of claim 27 in which the poly(ethylene oxide) substituent has an average molecular weight of about 1000.

29. The membrane of claim 24 in which said second monomer units comprise methyl methacrylate.

30. The membrane of claim 24 in which said second monomer units comprise ethyl acrylate.

31. The membrane of claim 30 in which said second monomer units comprise methyl methacrylate.