Biosensor Membrane Composition, Biosensor, and Methods for Making Same

Abstract

Selectively permeable membranes for biosensors are provided. In one embodiment, the membrane includes a polymer mixture that includes a polyurethane component, a siloxane component, and a hydrogel component, the components in the mixture in amounts of about 60 to about 80 wt % polyurethane, about 10 to about 20 wt % siloxane, and about 10 to about 20 wt % hydrogel. The membrane has a surface restructured to be hydrophilic, with the restructured surface being crosslinked via reactive end groups on at least one of the polyurethane, the siloxane, and the hydrogel components.

I claim: 
     
         1 . A selectively permeable membrane for a biosensor, comprising:
 a polymer mixture which comprises a polyurethane component, a siloxane component, and a hydrogel component, the components being present in the mixture in amounts of about 60 to about 80 wt % polyurethane, about 10 to about 20 wt % siloxane, and about 10 to about 20 wt % hydrogel,   wherein the membrane has a surface restructured to be hydrophilic, and the polymer mixture of the membrane with the restructured surface is crosslinked via reactive end groups on at least one of the polyurethane component, the siloxane component, and the hydrogel component.   
     
     
         2 . The membrane of  claim 1 , wherein the polyurethane component comprises a BIOSPAN™ polyether-based polyurethane polymer. 
     
     
         3 . The membrane of  claim 1 , wherein the siloxane component comprises polydimethylsiloxane. 
     
     
         4 . The membrane of  claim 1 , wherein the hydrogel component comprises polyethylene glycol which is bis(amine) terminated. 
     
     
         5 . The membrane of  claim 1 , wherein the components are present in the mixture in amounts of about 75 wt % polyurethane, about 15 wt % siloxane, and about 10 wt % hydrogel. 
     
     
         6 . A biosensor comprising:
 a substrate;   at least one electrode disposed on the substrate;   at least one enzyme layer disposed on the at least one electrode; and   at least one selectively permeable membrane fixed on the at least one enzyme layer, wherein the at least one selectively permeable membrane comprises a polymer mixture which comprises a polyurethane component, a siloxane component, and a hydrogel component, the components being present in the mixture in amounts of about 60 to about 80 wt % polyurethane, about 10 to about 20 wt % siloxane, and about 10 to about 20 wt % hydrogel,   wherein the at least one selectively permeable membrane has a surface restructured to be hydrophilic, and the polymer mixture of the membrane with the restructured surface is crosslinked via reactive end groups on at least one of the polyurethane component, the siloxane component, and the hydrogel component.   
     
     
         7 . The membrane of  claim 6 , wherein the polyurethane component comprises a BIOSPAN™ polyether-based polyurethane polymer. 
     
     
         8 . The membrane of  claim 6 , wherein the siloxane component comprises polydimethylsiloxane. 
     
     
         9 . The membrane of  claim 6 , wherein the hydrogel component comprises polyethylene glycol which is bis(amine) terminated. 
     
     
         10 . The membrane of  claim 6 , wherein the components are present in the mixture in amounts of about 75 wt % polyurethane, about 15 wt % siloxane, and about 10 wt % hydrogel. 
     
     
         11 . The membrane of  claim 6 , wherein the at least one enzyme layer comprises glucose oxidase. 
     
     
         12 . A method for making a selectively permeable membrane comprising:
 mixing a polyurethane component, a siloxane component, and a hydrogel component together with a first solvent for the components to form a polymer solution mixture;   depositing the polymer solution mixture on a substrate;   evaporating the first solvent from the polymer solution mixture to form a film of a polymer mixture, the film having a surface opposing the substrate;   applying a solvent mixture onto the surface of the film to partially re-dissolve and swell the film, wherein the solvent mixture comprises a hydrophilic constituent and a hydrophobic constituent; and   evaporating the solvent mixture from the partially redissolved and swollen film to reform the surface with hydrophilic molecules of the polymer mixture redistributed toward the reformed surface.   
     
     
         13 . The method of  claim 12 , wherein the polymer mixture comprises about 60 to about 80 wt % polyurethane, about 10 to about 20 wt % siloxane, and about 10 to about 20 wt % hydrogel. 
     
     
         14 . The method of  claim 12 , wherein the first solvent comprises tetrahydrofuran or another volatile organic solvent. 
     
     
         15 . The method of  claim 12 , wherein the solvent mixture comprises water and tetrahydrofuran in volume ratio of about 1:2. 
     
     
         16 . The method of  claim 12 , further comprising cross-linking the polymer mixture. 
     
     
         17 . A biosensor comprising:
 a substrate;   at least one electrode disposed on the substrate;   at least one enzyme layer disposed on the at least one electrode; and   at least one selectively permeable membrane fixed on the at least one enzyme layer, wherein the at least one selectively permeable membrane comprises a solvent cast film which comprises a mixture of a first polyether-based thermoplastic polyurethane copolymer, and a polyether-based polyurethane copolymer, wherein the polyether-based thermoplastic polyurethane copolymer, or the polyether-based polyurethane copolymer, or both comprise at least one siloxane repeat unit.   
     
     
         18 . The biosensor of  claim 17 , wherein when the polyether-based polyurethane copolymer comprises at least one siloxane repeat unit, the copolymers are present in the film in a proportion in the range of about 1:3 to about 1:4 polyether-based thermoplastic polyurethane copolymer to polyether-based polyurethane copolymer. 
     
     
         19 . The biosensor of  claim 17 , wherein the membrane further comprises a second polyether-based thermoplastic polyurethane copolymer. 
     
     
         20 . The biosensor of  claim 19 , wherein the second polyether-based thermoplastic polyurethane copolymer comprises at least one siloxane repeat unit. 
     
     
         21 . The biosensor of  claim 19 , wherein when the thermoplastic polyurethane copolymer comprises at least one siloxane repeat unit, the copolymers are present in the film in a proportion in the range of about 2:1:1 polyether-based polyurethane copolymer to polyether-based thermoplastic polyurethane copolymer to second polyether-based thermoplastic polyurethane copolymer. 
     
     
         22 . A method for making a selectively permeable membrane comprising:
 applying onto a substrate a polymer solution mixture which comprises a mixture of a first polyether-based thermoplastic polyurethane copolymer, and a polyether-based polyurethane copolymer, wherein the polyether-based thermoplastic polyurethane copolymer, or the polyether-based polyurethane copolymer, or both comprise at least one siloxane repeat unit, in solution with a volatile organic solvent; and   evaporating the volatile organic solvent from the polymer solution mixture to form a film of a polymer mixture on the substrate.   
     
     
         23 . The method of  claim 22 , wherein when the polyether-based polyurethane copolymer comprises at least one siloxane repeat unit, the copolymers are present in the film in a proportion in the range of about 1:3 to about 1:4 polyether-based thermoplastic polyurethane copolymer to polyether-based polyurethane copolymer. 
     
     
         24 . The method of  claim 22 , wherein the mixture further comprises a second polyether-based thermoplastic polyurethane copolymer. 
     
     
         25 . The method of  claim 24 , wherein the second polyether-based thermoplastic polyurethane copolymer comprises at least one siloxane repeat unit. 
     
     
         26 . The method of  claim 24 , wherein when the polyether-based thermoplastic polyurethane copolymer comprises at least one siloxane repeat unit, the copolymers are present in the film in a proportion in the range of about 2:1:1 polyether-based polyurethane copolymer to polyether-based thermoplastic polyurethane copolymer to second polyether-based thermoplastic polyurethane copolymer.