Biosensors and methods for making and using them

• US 20070135698A1
• Filed: 12/13/2005
• Published: 06/14/2007
• Est. Priority Date: 12/13/2005
• Status: Active Grant

• Current Assignee: Medtronic Minimed Incorporated (Medtronic Plc)
• Original Assignee: Medtronic Minimed Incorporated (Medtronic Plc)
• Inventors: Shah, Rajiv, Hoss, Udo, Soundararajan, Gopikrishnan, Gottlieb, Rebecca, Pendo, Shaun, Grovender, Eric
• Granted Patent: US 7,813,780 B2
• Time in Patent Office: Days
• US Class Current: 600/348
• CPC Class Codes: C12Q 1/006 for glucose

Abstract

Embodiments of the invention provide analyte sensors having optimized permselective membranes and methods for making and using such sensors. Embodiments of the invention also provide analyte sensors such as those having porous matrices coated with an analyte sensing composition and methods for making and using such sensors. Illustrative embodiments include electrochemical glucose sensors having glucose oxidase coatings.

Claims

1. A membrane for use with an implantable analyte sensor comprising:

a first layer comprising a biocompatible polymer composition that is;

impermeable to immunoglobulins; and

permeable to oxygen, glucose and lactate; and

a second layer coupled to the first layer comprising functionalized poly(dimethyl siloxane), functionalized poly(dimethyl siloxane) copolymer or a mixture of functionalized poly(dimethyl siloxane) and functionalized poly(dimethyl siloxane) copolymer,

wherein the membrane is more permeable to oxygen than glucose and/or lactate.

2. The membrane of claim 1, wherein the first layer comprises a plurality of pores disposed therein.

3. The membrane of claim 1, wherein the second layer comprises a plurality of pores disposed therein.

4. The membrane of claim 3, wherein at least one of the plurality of pores disposed in the second layer contains functionalized poly(dimethyl siloxane), functionalized poly(dimethyl siloxane) copolymer or a mixture of functionalized poly(dimethyl siloxane) and functionalized poly(dimethyl siloxane) copolymer of the second layer.

5. The membrane of claim 1, further comprising an adhesive layer disposed between the first and second layers, wherein the adhesive layer promotes adhesion between the first and second layers.

6. The membrane of claim 2, wherein the average diameter of the plurality of pores is between 2 microns and 40 microns.

7. The membrane of claim 2, wherein the average depth of the plurality of pores is between 50 microns and 250 microns.

10. The membrane of claim 1, wherein the first or second layer comprises a plurality of pores disposed therein and further wherein at least one of the plurality of pores contains a biocompatible hydrophilic polymer that facilitates hydration of an implantable analyte sensor.

11. The membrane of claim 10, wherein the hydrophilic polymer comprises an ethylene glycol or propylene glycol block copolymer or a mixture thereof.

12. The membrane of claim 10, wherein the hydrophilic polymer is a hydrogel.

13. The membrane of claim 10, wherein the biocompatible hydrophilic polymer enhances the wetting of a component in the sensor via capillary action.

14. The membrane of claim 10, wherein the biocompatible hydrophilic polymer is selectively disposed in a subset of the plurality of pores, wherein the subset of the plurality pores have a diameter or depth that is at least 10%, 20%, 30%, 40% or 50% larger than the average diameter of the plurality of pores or at least 10%, 20%, 30%, 40% or 50% larger than the average depth of the plurality of pores.

8. The membrane of 2, wherein the implantable analyte sensor is a glucose sensor that comprises a layer of glucose oxidase and further wherein the size of the pores is controlled to optimize the relative concentrations of glucose and oxygen that react with the glucose oxidase.

9. The membrane of 2, wherein the implantable analyte sensor is a glucose sensor that comprises a layer of glucose oxidase and further wherein the geometry of the pores is controlled to optimize the relative concentrations of glucose and oxygen that react with the glucose oxidase.

15. A method of immobilizing a protein on a rigid macroporous polymer comprising the steps of:

(a) combining the protein with the rigid macroporous polymer having functional moieties capable of crosslinking to a protein; and

(b) adding a crosslinking agent capable of immobilizing the protein on the rigid macroporous polymer by crosslinking the functional moieties of the protein with the functional moieties of the rigid macroporous polymer so that the protein is immobilized on the rigid macroporous polymer.

16. The method of claim 15, wherein the rigid macroporous polymer having functional moieties capable of crosslinking to a protein is made by combining a rigid macroporous polymer having reactive epoxide moieties with a nucleophilic compound so that a rigid macroporous polymer having functional moieties capable of crosslinking to a protein is made.

17. A method of immobilizing a protein on a rigid macroporous polymer comprising combining a protein having a sulfhydryl, amine, carboxyl or hydroxyl moiety with a rigid macroporous polymer having reactive epoxide moieties under reaction conditions that allow a nucleophilic reaction to occur between the sulfhydryl, amine, carboxyl or hydroxyl moieties on the protein and the epoxide moieties on the rigid macroporous polymer so that the protein is immobilized on the rigid macroporous polymer.

18. The method of claim 17, wherein at least one nucleophilic moiety on the protein is blocked prior to combining the protein with the rigid macroporous polymer.

19. A composition comprising a porous matrix having a surface coated with an immobilized enzyme, wherein the composition is implantable within a mammal.

20. The composition of claim 19, wherein the porous matrix is capable of acting as an electrode in an electrochemical sensor.

21. The composition of claim 19, wherein the enzyme is glucose oxidase, glucose dehydrogenase, lactate oxidase, hexokinase or lactate dehydrogenase.

22. The composition of claim 21, wherein the electrode consumes hydrogen peroxide in the electrochemical sensor.

23. The composition of claim 19, wherein the matrix comprises a micro-porous polymer.

24. The composition of claim 19, wherein the matrix comprises a micro-porous metal.

25. The composition of claim 19, wherein the matrix comprises a micro-porous a ceramic.

26. The composition of claim 19, wherein the porous matrix comprises a lattice of particles.

27. The composition of claim 26, wherein the particles are spherical.

28. The composition of claim 19, wherein the porous matrix is at least 1, 10, 100, or 1000 microns thick.

29. The composition of claim 19, wherein the porous matrix has a surface area that is at least 2, 4, 6, 8, 10, 12, 14, 16 or 18 times the surface area of a non-porous matrix of same dimensions.

30. The composition of claim 19, wherein the enzyme coated on the surface is in a coating layer having a thickness selected from the group consisting of less than 1, 0.5, 0.25 and 0.1 microns.

31. The composition of claim 19, wherein the porosity range of the porous matrix is 40%-99%.

32. An analyte sensor apparatus for implantation within a mammal, the analyte sensor apparatus comprising a porous matrix having a surface coated with an immobilized enzyme.

33. The analyte sensor apparatus of claim 32, wherein:

the porous matrix comprises a working electrode; and

the immobilized enzyme is disposed within an analyte sensing layer disposed on the working electrode, such that the analyte sensing layer detectably alters the electrical current at the working electrode in the conductive layer in the presence of an analyte.

34. The analyte sensor apparatus of claim 33, further comprising an analyte modulating layer disposed on the analyte sensing layer, wherein the analyte modulating layer modulates the diffusion of the analyte therethrough.

35. The analyte sensor apparatus of claim 34, further comprising an adhesion promoting layer disposed on the analyte sensing layer, wherein the adhesion promoting layer promotes the adhesion between the analyte sensing layer and an analyte modulating layer disposed on the analyte sensing layer.

36. The analyte sensor apparatus of claim 34, further comprising a protein layer disposed between the analyte sensing layer and the analyte modulating layer.

37. The analyte sensor apparatus of claim 34, further comprising an interference rejection layer disposed between the surface of the working electrode and the analyte sensing layer.

38. The analyte sensor apparatus of claim 34, further comprising a cover layer disposed on at least a portion of the analyte modulating layer, wherein the cover layer further includes an aperture that exposes at least a portion of the analyte modulating layer to a solution comprising the analyte to be sensed.

39. The analyte sensor apparatus of claim 33, wherein the analyte sensing layer comprises an enzyme selected from the group consisting of glucose oxidase, glucose dehydrogenase, lactate oxidase, hexokinase and lactate dehydrogenase.

40. The analyte sensor apparatus of claim 39, wherein the analyte sensing layer further comprises a carrier protein in a substantially fixed ratio with the enzyme.

41. The analyte sensor apparatus of claim 40, wherein the enzyme and the carrier protein are distributed in a substantially uniform manner throughout the enzyme layer.

44. A kit comprising a container and, within the container, an analyte sensor apparatus according to claim 33 and instructions for using the analyte sensor apparatus.

42. A method of sensing an analyte within the body of a mammal, the method comprising implanting an analyte sensor in to the mammal, the analyte sensor comprising:

a conductive micro-porous matrix that functions as a working electrode;

an analyte sensing layer disposed on the micro-porous matrix, wherein the analyte sensing layer detectably alters the electrical current at the micro-porous matrix in the presence of an analyte;

an optional protein layer disposed on the analyte sensing layer;

an adhesion promoting layer disposed on the analyte sensing layer or the optional protein layer, wherein the adhesion promoting layer promotes the adhesion between the analyte sensing layer and an analyte modulating layer disposed on the analyte sensing layer; and

an analyte modulating layer disposed on the analyte sensing layer, wherein the analyte modulating layer modulates the diffusion of the analyte therethrough;

an optional cover layer disposed on at least a portion of the analyte modulating layer, wherein the cover layer further includes an aperture over at least a portion of the analyte modulating layer; and

sensing an alteration in current at the working electrode and correlating the alteration in current with the presence of the analyte, so that the analyte is sensed.

43. The method of claim 42, wherein the analyte sensor is polarized anodically such that the working electrode where the alteration in current is sensed is an anode.

45. A method of making a metallic mold for forming a polymerized composition of a predetermined geometry comprising:

(a) providing a base substrate;

(b) disposing a conductive layer on to (a portion) the base substrate;

(c) disposing a positive photoresist layer on to the conductive layer;

(d) disposing a sacrificial metal layer on to the positive photoresist layer;

(e) disposing a negative photoresist layer on to the sacrificial metal layer;

(f) developing the negative photoresist layer via UV photolithography;

(removing the areas of the sacrificial metal layer exposed by the development of the negative resist layer using an etchant;

(h) exposing components (a)-(g) to UV photolithography;

(i) developing the positive photoresist layer via a developing solvent;

(j) electroplating components (a)-(i) with a layer of conductive material; and

(k) removing the positive photoresist layer, the sacrificial metal layer, and the negative photoresist layer from the so layered substrate using a solvent so that the mold is made.

46. A printing process for making a porous metallic matrix, the process comprising

(a) forming an ink of fine metallic particles suspended in a porogenic carrier solvent;

(b) printing the ink onto a substrate;

(c) optionally repeating step (b) to obtain a film of a desired thickness;

(d) drying the printed metallic matrix to remove porogenic carrier solvent;

(e) firing the resulting porous bed of metallic powder so as to bond the metallic particles together;

so that a porous metallic matrix is made.