Techniques to improve polyurethane membranes for implantable glucose sensors

Abstract

The invention provides an implantable membrane for regulating the transport of analytes therethrough that includes a matrix including a first polymer; and a second polymer dispersed throughout the matrix, wherein the second polymer forms a network of microdomains which when hydrated are not observable using photomicroscopy at 400× magnification or less. In one aspect, the homogeneous membrane of the present invention has hydrophilic domains dispersed substantially throughout a hydrophobic matrix to provide an optimum balance between oxygen and glucose transport to an electrochemical glucose sensor.

What is claimed is: 
     
         1 . A method for fabricating a device for measuring a concentration of an analyte, the method comprising:
 providing a sensor mechanism configured to measure an analyte or a product of a reaction associated with the analyte;   forming a solution comprising a blend of a first polymer and a second polymer, wherein a segment of the first polymer and a segment of the second polymer are both formed of a same monomer unit;   maintaining the solution at a temperature sufficient to maintain solubility of the first polymer and the second polymer;   applying the solution to the sensor mechanism;   forming a film from the solution at the temperature; and   drying the film to form a membrane.   
     
     
         2 . The method of  claim 1 , wherein the monomer unit is selected from the group consisting of a polyurethane, a vinyl polymer, a polyether, a polyester, a polyamide, a polysiloxane, and a polycarbosiloxane. 
     
     
         3 . The method of  claim 1 , wherein the second polymer is a hydrophobic-hydrophilic co-polymer comprising a hydrophobic segment and a hydrophilic segment. 
     
     
         4 . The method of  claim 1 , wherein the second polymer comprises a polyurethane segment. 
     
     
         5 . The method of  claim 1 , wherein the membrane has a thickness of from about 5 microns to about 100 microns. 
     
     
         6 . The method of  claim 1 , wherein the analyte is glucose. 
     
     
         7 . The method of  claim 6 , wherein the membrane has an oxygen-to-glucose permeability ratio of approximately 200:1. 
     
     
         8 . The method of  claim 1 , wherein maintaining the solution at a temperature comprises heating the solution to a temperature of at least about 70° C. 
     
     
         9 . The method of  claim 1 , wherein the first polymer is a homopolymer. 
     
     
         10 . A method for fabricating a device for measuring a concentration of an analyte, the method comprising:
 providing a sensor mechanism configured to measure an analyte or a product of a reaction associated with the analyte;   forming a solution comprising a blend of a first polymer and a second polymer, wherein the first polymer is a hydrophilic polymer comprising a hydrophilic segment, wherein the second polymer is a hydrophobic-hydrophilic co-polymer comprising a hydrophobic segment and a hydrophilic segment, and wherein the hydrophilic segment of the first polymer and the hydrophilic segment of the second polymer are both formed of a same block; and   applying the solution to the sensor mechanism.   
     
     
         11 . The method of  claim 10 , further comprising:
 maintaining the solution at a temperature sufficient to maintain solubility of the first polymer and the second polymer.   
     
     
         12 . The method of  claim 11 , wherein maintaining the solution at a temperature comprises heating the solution to a temperature of at least about 70° C. 
     
     
         13 . The method of  claim 11 , further comprising:
 forming a film from the solution at the temperature; and   drying the film to form a membrane.   
     
     
         14 . The method of  claim 13 , wherein the membrane has a thickness of from about 5 microns to about 100 microns. 
     
     
         15 . The method of  claim 10 , wherein the second polymer comprises at least one block selected from the group consisting of a polyurethane, a vinyl polymer, a polyether, a polyester, a polyamide, a polysiloxane, a polycarbosiloxane, a polyethylene oxide, and copolymers thereof. 
     
     
         16 . The method of  claim 10 , wherein the analyte is glucose. 
     
     
         17 . The method of  claim 16 , wherein the membrane has an oxygen-to-glucose permeability ratio of approximately 200:1. 
     
     
         18 . The method of  claim 10 , wherein the first polymer is a homopolymer. 
     
     
         19 . A method for fabricating a device for measuring a concentration of an analyte, the method comprising:
 providing a sensor mechanism configured to measure an analyte or a product of a reaction associated with the analyte;   forming a solution comprising a matrix comprising a first polymer, wherein the solution further comprises a second polymer dispersed throughout the matrix, wherein the first polymer forms a network of hydrophilic microdomains throughout the matrix to create a pathway for analyte diffusion across a membrane, and wherein a segment of the first polymer and a segment of the second polymer are both formed of a same monomer unit;   maintaining the solution at a temperature sufficient to maintain solubility of the first polymer and the second polymer;   applying the solution to the sensor mechanism;   forming a film from the solution at the temperature; and   drying the film to form the membrane.   
     
     
         20 . The method of  claim 19 , wherein the monomer unit is selected from the group consisting of a polyurethane, a vinyl polymer, a polyether, a polyester, a polyamide, a polysiloxane, and a polycarbosiloxane. 
     
     
         21 . The method of  claim 19 , wherein the second polymer is a hydrophobic-hydrophilic co-polymer comprising a hydrophobic segment and a hydrophilic segment. 
     
     
         22 . The method of  claim 19 , wherein the second polymer comprises a polyurethane segment. 
     
     
         23 . The method of  claim 19 , wherein the membrane has a thickness of from about 5 microns to about 100 microns. 
     
     
         24 . The method of  claim 19 , wherein the analyte is glucose. 
     
     
         25 . The method of  claim 24 , wherein the membrane has an oxygen-to-glucose permeability ratio of approximately 200:1. 
     
     
         26 . The method of  claim 19 , wherein maintaining the solution at a temperature comprises heating the solution to a temperature of at least about 70° C. 
     
     
         27 . The method of  claim 19 , wherein the first polymer is a homopolymer.