Polycarbonate urea/urethane polymers for use with analyte 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 polymer composition having carbonate and aromatic isocyanate chains, a composition observed to provide such membranes with improved material properties such as enhanced thermal and hydrolytic stability.
1. A method of making an analyte sensor for implantation within a mammal comprising the steps of:
providing a base layer;
forming a conductive layer on the base layer, wherein the conductive layer includes a working electrode;
forming an analyte sensing layer on the conductive layer, wherein the analyte sensing layer includes an oxidoreductase; and
forming an analyte modulating layer on the analyte sensing layer, wherein:
the analyte modulating layer comprises a polyurea-urethane copolymer formed from a reaction mixture comprising:
(a) a diisocyanate;
(b) a hydrophilic polymer comprising a hydrophilic diol or hydrophilic diamine;
(c) a siloxane having an amino, hydroxyl or carboxylic acid functional group at a terminus; and
(d) a polycarbonate diol, wherein:
the diisocyanate comprises a hexamethylene diisocyanate and/or a methylene diphenyl diisocyanate;
the hydrophilic polymer comprising a hydrophilic diol or hydrophilic diamine comprises a polyetheramine;
the siloxane having an amino, hydroxyl or carboxylic acid functional group at a terminus comprises a polydimethylsiloxane; and
the polycarbonate diol comprises a poly(1,6-hexyl carbonate) diol and/or a poly(1,6 hexyl-1,5 pentyl carbonate) diol; and
the diisocyanate comprises:
from 17% to 23% weight percent hexamethylene diisocyanate; and
from 0% to 8.5% weight percent methylene diphenyl diisocyanate; and
the polydimethylsiloxane comprises from 14% to 32% weight percent polydimethylsiloxane-A15; and
the polycarbonate diol comprises from 7.5% to 19% weight percent poly(1,6-hexyl carbonate) diol.
2. The method of claim 1 , wherein the polyurea-urethane copolymer is formed from the reaction mixture selected to exhibit an improved thermal stability over time as compared to an equivalent analyte sensor having an analyte modulating layer formed from a comparative reaction mixture that does not include the polycarbonate diol; wherein said improved thermal stability over time comprises a loss of polyurea-urethane copolymer molecular weight after aging at 100% relative humidity (RH) at 60° C. over 6 days that is at least 10% less than the loss of molecular weight after aging at 100% relative humidity (RH) at 60° C. over 6 days that is observed in a polyurea-urethane copolymer formed from a reaction mixture that does not include the polycarbonate diol.
3. The method of claim 1 , wherein the polyurea-urethane copolymer is formed from a reaction mixture selected to exhibit an improved resistance to degradation/damage caused by ebeam radiation and/or ethylene oxide as compared to an equivalent analyte sensor having an analyte modulating layer formed from a reaction mixture that does not include the polycarbonate diol.
4. The method of claim 1 , wherein the polyurea-urethane copolymer is formed from a reaction mixture selected to exhibit an improved thermal stability over time as compared to an equivalent analyte sensor having an analyte modulating layer formed from a reaction mixture that does not include the polycarbonate diol.
5. The method of claim 1 , wherein the polyurea-urethane copolymer is formed from a reaction mixture selected to exhibit an improved resistance to oxidation over time as compared to an equivalent analyte sensor having an analyte modulating layer formed from a reaction mixture that does not include the polycarbonate diol.
6. The method of claim 1 , wherein the polyurea-urethane copolymer is formed from a reaction mixture selected to exhibit less deformation over time as compared to an equivalent analyte sensor having an analyte modulating layer formed from a reaction mixture that does not include the polycarbonate diol.
7. The method of claim 1 , wherein:
the analyte modulating layer comprises the polyurea-urethane copolymer formed from a reaction mixture comprising:
(a) a diisocyanate present in amounts from 2% to 25% in the polyurea-urethane copolymer formed from the reaction mixture;
(b) a hydrophilic polymer comprising a hydrophilic diol or hydrophilic diamine;
(c) a siloxane having an amino, hydroxyl or carboxylic acid functional group at a terminus; and
(d) a polycarbonate diol, wherein:
the diisocyanate comprises a hexamethylene diisocyanate and/or a methylene diphenyl diisocyanate;
the hydrophilic polymer comprising a hydrophilic diol or hydrophilic diamine comprises a polyetheramine;
the siloxane having an amino, hydroxyl or carboxylic acid functional group at a terminus comprises a polydimethylsiloxane; and
the polycarbonate diol comprises a poly(1,6-hexyl carbonate) diol and/or a poly(1,6 hexyl-1,5 pentyl carbonate) diol.
8. The method of claim 1 , wherein the polyurea-urethane copolymer is formed from a reaction mixture selected to exhibit a more uniform glucose permeability profile over time as compared to an equivalent analyte sensor lacking the polyurea-urethane copolymer.
9. The method of claim 1 , wherein the analyte sensor is a glucose sensor.
10. The method of claim 1 , wherein the conductive layer comprises a plurality of working electrodes and/or counter electrodes and/or reference electrodes; and 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.