Thermally stable glucose limiting membrane for glucose sensors
Embodiments of the invention provide compositions useful in analyte sensors as well as methods for making and using such compositions and sensors. In typical embodiments of the invention, the sensor is a glucose sensor comprising an analyte modulating membrane formed from a polymeric reaction mixture formed to include limiting amounts of catalyst and/or polycarbonate compounds so as to provide such membranes with improved material properties such as enhanced thermal and hydrolytic stability.
1. An amperometric analyte sensor comprising:
a base layer;
a conductive layer disposed on the base layer and comprising a working electrode;
an analyte sensing layer disposed on the conductive layer; and
an analyte modulating layer disposed on the analyte sensing layer, wherein the analyte modulating layer:
(a) is formed by a reaction mixture comprising:
from 17% to 23% weight percent hexamethylene diisocyanate;
from 0% to 8.5% weight percent methylene diphenyl diisocyanate;
from 14% to 48% weight percent polydimethylsiloxane having amino terminal groups; and
from 7.5% to 19% weight percent poly(1,6-hexyl carbonate) diol; and
a catalyst present in the reaction mixture in amounts less than 0.2% of reaction mixture components; and
(b) exhibits a greater thermal stability than a comparable analyte modulating layer formed from a reaction mixture where the catalyst is present in the formulation in amounts greater than or equal to 0.2% of the reaction mixture.
2. The amperometric analyte sensor of claim 1 , wherein the amperometric analyte sensor is a glucose sensor comprising an architecture adapted to measure glucose in interstitial fluids.
3. The amperometric analyte sensor of claim 1 , further comprising at least one of:
a protein layer disposed on the analyte sensing layer; or
a cover layer disposed on the analyte sensor apparatus, wherein the cover layer comprises an aperture positioned on the cover layer so as to facilitate an analyte present in an in vivo environment from contacting and diffusing through an analyte modulating layer; and contacting the analyte sensing layer.
4. The amperometric analyte sensor of claim 1 , wherein the conductive layer comprises a plurality of electrodes including a working electrode, a counter electrode and a reference electrode.
5. The amperometric analyte sensor of claim 4 , wherein the conductive layer comprises a plurality of working electrodes and/or counter electrodes and/or reference electrodes; and optionally the plurality of working, counter and reference electrodes are grouped together as a unit and positionally distributed on the conductive layer in a repeating pattern of units.
6. The amperometric analyte sensor of claim 1 , wherein the analyte modulating layer is formed by a reaction mixture further comprising a polycarbonate.
7. The amperometric analyte sensor of claim 1 , wherein the catalyst is present in the reaction mixture in amounts less than 0.11% of the reaction mixture.
8. The amperometric analyte sensor of claim 1 , wherein the analyte modulating layer comprises:
about 22% hexamethylene diisocyanate;
about 3.5% methylene diphenyl diisocyanate;
about 22.5% polydimethylsiloxane having amino terminal groups; and
about 7.5% poly(1,6-hexyl carbonate) diol.
9. The amperometric analyte sensor of claim 1 , wherein water is included as a chain extender in the reaction mixture.
10. The amperometric analyte sensor of claim 1 , wherein thermal stability of the analyte modulating layer is measured by observing changes in molecular weight of the analyte modulating layer maintained at a temperature of 60° C. over at least 3, 5 or 7 days.
11. An amperometric analyte sensor comprising:
a base layer;
a conductive layer disposed on the base layer and comprising a working electrode;
an analyte sensing layer disposed on the conductive layer; and
an analyte modulating layer disposed on the analyte sensing layer, wherein the analyte modulating layer:
(a) is formed by a reaction mixture comprising:
from 17% to 23% weight percent hexamethylene diisocyanate;
from 0% to 8.5% weight percent methylene diphenyl diisocyanate;
from 14% to 48% weight percent polydimethylsiloxane having amino terminal groups;
a polycarbonate diol; and
a catalyst present in the reaction mixture in amounts less than 0.2% of reaction mixture components; and
(b) exhibits a greater thermal stability than a comparable analyte modulating layer formed from a reaction mixture where the catalyst is present in the formulation in amounts greater than or equal to 0.2% of the reaction mixture.
12. The amperometric analyte sensor of claim 11 , wherein the amperometric analyte sensor is a glucose sensor comprising an architecture adapted to measure glucose in interstitial fluids.
13. The amperometric analyte sensor of claim 11 , wherein the catalyst is present in the reaction mixture in amounts less than 0.11% of the reaction mixture.