Outer membrane compositions for creatinine/creatine sensors
Disclosed herein are compositions for permeable outer diffusion control membranes for creatinine and creatine sensors and methods of making such membranes.
1. A biosensor comprising:
an electrode;
an enzyme layer on the electrode; and
a diffusion membrane on the enzyme layer, the diffusion membrane comprising at least two different types of polyurethane materials, the at least two different types of polyurethane materials comprising (i) 50% to 55% w/w of 20% water uptake polyurethane and (ii) 45% to 50% w/w of 60% water uptake polyurethane;
wherein the diffusion membrane has a creatinine to creatine diffusion ratio of at least 2.0.
2. The biosensor of claim 1 , wherein the at least two different types of polyurethane materials comprise (i) 55% w/w of 20% water uptake polyurethane and (ii) 45% w/w of 60% water uptake polyurethane.
3. The biosensor of claim 1 , wherein the at least two different types of polyurethane materials comprise at least three different types of polyurethane materials.
4. The biosensor of claim 3 , wherein the at least three different types of polyurethane materials comprise 50% water uptake polyurethane.
5. The biosensor of claim 1 , wherein the at least two different types of polyurethane materials comprise at least four different types of polyurethane materials.
6. The biosensor of claim 1 , wherein the at least two different types of polyurethane materials comprise 45% w/w of 60% water uptake polyurethane.
7. The biosensor of claim 1 , wherein the enzyme layer comprises at least one of creatininase, creatinase, or sarcosine oxidase.
8. The biosensor of claim 1 , wherein the creatinine to creatine diffusion ratio is at least 3.0.
9. The biosensor of claim 1 , wherein the creatinine to creatine diffusion ratio is stable over a 5-month shelf life at ambient storage.
10. The biosensor of claim 1 , wherein the electrode comprises metal.
11. The biosensor of claim 10 , wherein the metal comprises at least one of platinum, gold, palladium, or alloys comprised of platinum, gold, or palladium.
12. The biosensor of claim 1 , wherein the electrode comprises carbon, graphite, or carbon nanotubes.
13. The biosensor of claim 1 , wherein the enzyme layer comprises creatininase, creatinase, and sarcosine oxidase.
14. The biosensor of claim 13 , wherein the creatinine to creatine diffusion ratio is at least 3.0.
15. The biosensor of claim 1 , wherein the biosensor is configured to measure creatine and/or creatinine in a body fluid sample.
16. The biosensor of claim 15 , wherein the body fluid sample comprises blood, plasma, or serum.
17. The biosensor of claim 1 , wherein the creatinine to creatine diffusion ratio is stable over a 5 -month shelf life at ambient storage.
18. The biosensor of claim 1 , wherein the electrode comprises metal or carbon.
19. The biosensor of claim 18 , wherein the metal comprises at least one of platinum, gold, palladium, or alloys comprised of platinum, gold, or palladium.
20. The biosensor of claim 19 , wherein the carbon comprises graphite or carbon nanotubes.
21. The biosensor of claim 18 , wherein the enzyme layer comprises two or more of creatininase, creatinase, or sarcosine oxidase.
22. The biosensor of claim 21 , wherein the biosensor is configured to measure creatine and/or creatinine in a body fluid sample.
23. The biosensor of claim 22 , wherein the body fluid sample comprises blood, plasma, or serum.
24. A disposable cartridge housing the biosensor of claim 1 .
25. A method of making the diffusion membrane of the biosensor of claim 1 , comprising:
a) dissolving at least two different polyurethane resins in an organic solvent or mixture of solvents to create a polyurethane mixture;
b) casting a layer of the polyurethane mixture onto a support material;
c) allowing the solvent or mixture of solvents to evaporate; and
d) repeating b) and c) 1-3 times.
26. The method of claim 25 , wherein the different polyurethane resins have different water uptake percentages.
27. The method of claim 25 , wherein the organic solvent comprises at least one of methylene chloride, dimethylformamide, dimethylacetamide, tetrahydrofuran, cyclohexanone, isopropanol, or a mixture of two or more of: methylene chloride, dimethylformamide, dimethylacetamide, tetrahydrofuran, cyclohexanone, or isopropanol.
28. The method of claim 25 , wherein the support material comprises the electrode and the enzyme layer.
29. The method of claim 25 , wherein b) and c) are repeated two times.