Method of stabilising or reactivating a creatinine sensor with a divalent manganese ion

• US 20060275860A1
• Filed: 05/16/2006
• Published: 12/07/2006
• Est. Priority Date: 05/17/2005
• Status: Active Grant

• Current Assignee: Radiometer Medical ApS (Danaher Corporation)
• Original Assignee: Radiometer Medical ApS (Danaher Corporation)
• Inventors: Kristensen, Tina, Ostergaard, Jens, Kjaer, Thomas
• Granted Patent: US 7,888,061 B2
• Time in Patent Office: Days
• US Class Current: 435/27
• CPC Class Codes: C12Q 1/34 involving hydrolase
• CPC Class Codes: G01N 2333/978 acting on carbon to nitrogen bonds other than peptide bonds (3.5)

Abstract

A method is provided for stabilising a creatinine sensor comprising creatininase as a bioactive molecule. The creatininase is stabilised by exposing it to a sufficient amount of a divalent manganese ion. This result may be obtained by exposing the sensor to a solution comprising the divalent manganese ion or by introducing a composition within the sensor providing sustained release of the divalent manganese ion.

Claims

1. A method of stabilising or reactivating a creatinine sensor comprising creatininase as a bioactive molecule, comprising exposing the creatininase to an amount of a solution of a divalent manganese ion sufficient to increase the stability or to increase the activity of the sensor, wherein the solution comprises the divalent manganese ion in a concentration of in the range of about 0.01 to about 150 μ

M.

2. The method according to claim 1, wherein the concentration of the divalent manganese ion is in the range of about 0.01 to about 130 μ

M.

3. The method according to claim 2, wherein the concentration of the divalent manganese ion is in the range of about 0.1 to about 100 μ

M.

4. The method according to claim 3, wherein the concentration of the divalent manganese ion is in the range of about 0.1 to about 50 μ

M.

5. The method according to claim 1, wherein the creatininase is exposed to the amount of the divalent manganese ion by conveying the solution comprising the divalent manganese ion to the creatininase.

6. The method according to claim 1, wherein the solution is prepared by passing a suitable liquid over a filter comprising a composition that releases the divalent manganese ion for a sustained period of time prior to exposing the creatininase to the solution.

7. The method according to claim 1, wherein the amount of the divalent manganese ion is prepared as a solution by contacting a suitable liquid with a composition present within the sensor that releases the divalent manganese ion for a sustained period of time and then exposing the solution to the creatininase.

8. The method according to claim 6 or claim 7, wherein the composition comprises a sparingly soluble salt of the divalent manganese ion.

9. The method according to claim 8, wherein the sparingly soluble salt of the divalent manganese ion is selected from the group consisting of carbonate, citrate, tartrate, oxalate, orthophosphate, selenide, sulphide, hydroxide, oxalate, orthophosphate, selenite, and mixtures thereof.

10. The sensor according to claim 9, wherein the sparingly soluble salt is selected from the group consisting of carbonate, citrate, and tartrate.

11. The method according to claim 1, wherein the creatininase is exposed to the solution of the divalent manganese ion for at least about 50% of the time, and wherein the concentration of the divalent manganese ion in said solution is in the range of about 5 to about 10 μ

M.

12. The method according to claim 1, wherein the creatininase is further exposed to a solution comprising a cation complexing agent.

13. The method according to claim 12, wherein the cation complexing agent is ethylenediamine tetraacetic acid (EDTA).

14. The method according to claim 12 or claim 13, wherein the creatininase is exposed to the divalent manganese ion for at least about 50% of the time, and wherein the concentration of the cation complexing agent is in the range of about 1 to about 4 μ

M.

15. A stabilised creatinine sensor comprising creatininase as a bioactive molecule, and a composition that releases an amount of a divalent manganese ion for a sustained period of time sufficient to stabilise or reactivate the sensor.

16. The sensor according to claim 15, wherein the composition comprises a sparingly soluble salt of the divalent manganese ion.

17. The sensor according to claim 16, wherein the sparingly soluble salt of the divalent manganese ion is selected from the group consisting of carbonate, citrate, tartrate, oxalate, orthophosphate, selenide, sulphide, hydroxide, oxalate, orthophosphate, selenite, and mixtures thereof.

18. The sensor according to claim 17, wherein the sparingly soluble salt is selected from the group consisting of carbonate, citrate, and tartrate.

19. The sensor according to claim 15, wherein the composition comprises a polymeric matrix.

20. The sensor according to claim 15, wherein the creatininase and the composition are entrapped within a membrane.

21. The sensor according to claim 15, wherein the sensor further comprises creatinase and sarcosine oxidase as bioactive molecules.

30. An apparatus for determining creatinine in a physiological fluid, comprising a creatinine sensor comprising creatininase as a bioactive molecule, wherein the creatinine sensor is the sensor according to claim 15 or a sensor comprising the membrane according to claim 22.

22. A membrane for a creatinine sensor comprising creatininase as a bioactive molecule and a composition that releases an amount of a divalent manganese ion for a sustained period of time sufficient to stabilise or reactivate the sensor.

23. The membrane according to claim 22, wherein the composition comprises a sparingly soluble salt of the divalent manganese ion.

24. The membrane according to claim 23, wherein the sparingly soluble salt of the divalent metal ion is selected from the group consisting of carbonate, citrate, tartrate, oxalate, orthophosphate, selenide, sulphide, hydroxide, oxalate, orthophosphate, selenite, and mixtures thereof.

25. The membrane according to claim 24, wherein the sparingly soluble salt is selected from the group consisting of carbonate, citrate, and tartrate.

26. The membrane according to claim 22, wherein the composition comprises a polymeric matrix.

27. The membrane according to claim 22, wherein the membrane further comprises creatinase and sarcosine oxidase as bioactive molecules.

28. An apparatus for determining creatinine in a physiological fluid, comprising a creatinine sensor comprising creatininase as a bioactive molecule, a solution of a divalent manganese ion in a concentration of in the range of about 0.01 to about 150 μ

M, and a device for exposing the creatininase to the divalent manganese ion of the solution.

29. An apparatus for determining creatinine in a physiological fluid, comprising a creatinine sensor comprising creatininase as a bioactive molecule, a filter comprising a composition that upon wetting releases a divalent manganese ion for a sustained period of time, a device for passing a suitable liquid over the filter to obtain a solution of a divalent manganese ion in a concentration of in the range of about 0.01 to about 150 μ

M, and a device for exposing the creatininase to the divalent manganese ion of the solution.