Diffusion resistance layer for analyte sensors

Abstract

Disclosed are devices for determining an analyte concentration (e.g., glucose). The devices comprise a sensor configured to generate a signal associated with a concentration of an analyte and a sensing membrane located over the sensor. The sensing membrane comprises an enzyme layer, wherein the enzyme layer comprises an enzyme and a polymer comprising polyurethane and/or polyurea segments and one or more zwitterionic repeating units. The enzyme layer protects the enzyme and prevents it from leaching from the sensing membrane into a host or deactivating.

What is claimed is: 
     
         1 . A device for measurement of an analyte concentration, the device comprising:
 a transcutaneous sensor configured to generate a signal associated with the analyte concentration; and   a sensing membrane located over the transcutaneous sensor, the sensing membrane comprising a diffusion-resistance layer comprising a base polymer, the base polymer comprising polyurethane segments and one or more polycarbonate or polyester segments and having a lowest glass transition temperature as measured using ASTM D3418 of greater than −50° C., wherein the base polymer comprises 5% to 50% by weight hard segment and 5% to 50% by weight soft segment, wherein the base polymer comprises less than 1 wt. % polysiloxane.   
     
     
         2 . The device of  claim 1 , wherein the lowest glass transition temperature of the base polymer is greater than 0° C. 
     
     
         3 . The device of  claim 1 , wherein the lowest glass transition temperature of the base polymer is from 0° C. to 66° C. 
     
     
         4 . The device of  claim 1 , wherein the lowest glass transition temperature of the base polymer is from 20° C. to 60° C. 
     
     
         5 . The device of  claim 1 , wherein the lowest glass transition temperature of the base polymer is from 0° C. to 30° C. 
     
     
         6 . The device of  claim 1 , wherein the lowest glass transition temperature of the base polymer is from 30° C. to 60° C. 
     
     
         7 . The device of  claim 1 , wherein the ultimate tensile strength of the base polymer is greater than 8250 psi. 
     
     
         8 . The device of  claim 1 , wherein the base polymer is a polyurethane copolymer chosen from a polycarbonate-urethane, a polyether-urethane, a polyester-urethane, and/or copolymers thereof. 
     
     
         9 . The device of  claim 1 , wherein the base polymer comprises a polymer selected from epoxies, polystyrene, polyoxymethylene, polyethers, polyacrylics, polymethacrylics, polyamides, a poly(ether ketone), a poly(ether imide), and/or copolymers thereof. 
     
     
         10 . The device of  claim 1 , wherein the diffusion-resistance layer further comprises a hydrophilic polymer. 
     
     
         11 . The device of  claim 10 , wherein the hydrophilic polymer is selected from polyvinyl alcohol, polyethylene glycol, polyacrylamide, polyacetate, polyethylene oxide, polyethyleneamine, polyvinylpyrrolidone, polyoxazoline, and/or mixtures thereof. 
     
     
         12 . The device of  claim 10 , wherein the hydrophilic polymer is blended with the base polymer. 
     
     
         13 . The device of  claim 10 , wherein the hydrophilic polymer is covalently bonded to the base polymer. 
     
     
         14 . The device of  claim 10 , wherein the base polymer or the hydrophilic polymer comprises a crosslinker or several crosslinkers, wherein the crosslinker comprises a polymer or an oligomer selected from a polyfunctional isocyanate, a polyfunctional aziridine, or a polyfunctional carbodiimide. 
     
     
         15 . The device of  claim 1 , wherein the diffusion-resistance layer comprises a blend of a polycarbonate-urethane base polymer and polyvinylpyrrolidone. 
     
     
         16 . The device of  claim 1 , wherein the diffusion-resistance layer is from 0.01 μm to about 250 μm thick. 
     
     
         17 . The device of  claim 1 , wherein the transcutaneous sensor has a drift of less than or equal to 10% over 10 days. 
     
     
         18 . The device of  claim 1 , wherein the transcutaneous sensor comprises an electrode. 
     
     
         19 . The device of  claim 1 , wherein the device is configured for continuous measurement of the analyte concentration. 
     
     
         20 . The device of  claim 1 , wherein the analyte concentration is a glucose concentration. 
     
     
         21 . The device of  claim 1 , wherein the base polymer has an ultimate tensile strength as measured by ASTM D1708 that is greater than 6000 psi. 
     
     
         22 . The device of  claim 1 , wherein the base polymer has a plurality of glass transition temperatures as measured using ASTM D3418. 
     
     
         23 . A device for measurement of an analyte concentration, the device comprising:
 a transcutaneous sensor configured to generate a signal associated with the analyte concentration; and   a sensing membrane located over the transcutaneous sensor, the sensing membrane comprising a diffusion-resistance layer comprising a base polymer, wherein the base polymer includes polyurethane segments and one or more polycarbonate or polyester segments, wherein the transcutaneous sensor has less than 10% change in signal at 2 hours after start and the base polymer comprises 5% to 50% by weight hard segment and 5% to 50% by weight soft segment, wherein the base polymer comprises less than 1 wt. % polysiloxane.   
     
     
         24 . The device of  claim 23 , wherein the base polymer further comprises polyurea segments. 
     
     
         25 . The device of  claim 23 , wherein the diffusion-resistance layer base polymer further comprises polyurea segments.