Polymer membranes for continuous analyte sensors

Abstract

Devices and methods are described for providing continuous measurement of an analyte concentration. In some embodiments, the devices include a membrane that has an interference domain designed to reduce the permeation of one or more interferents.

What is claimed is: 
     
         1 . A method for forming a membrane on an implantable device configured for continuous measurement of an analyte concentration, comprising:
 applying a first solution to an implantable sensor or a layer deposited thereon, the first solution having a first pH and comprising polycations;   drying the first solution to form a polycationic layer;   applying a second solution to the polycationic layer, the second solution having a second pH and comprising polyanions; and   drying the second solution to form a polyanionic layer.   
     
     
         2 . The method of  claim 1 , wherein the first pH is approximately a pK b  of the polycations. 
     
     
         3 . The method of  claim 1 , wherein the first pH is from about 9 to 10. 
     
     
         4 . The method of  claim 1 , wherein the second pH is approximately a pK a  of the polyanions. 
     
     
         5 . The method of  claim 1 , wherein the second pH is from about 2 to 3. 
     
     
         6 . The method of  claim 1 , further comprising applying a solution comprising an enzyme onto at least one of a polycationic layer or a polyanionic layer to form an enzyme layer. 
     
     
         7 . The method of  claim 6 , wherein the analyte is glucose, and wherein the enzyme is glucose oxidase. 
     
     
         8 . An implantable device for continuous measurement of glucose concentration, the device comprising:
 an electrode configured to generate a signal indicative of a concentration of glucose in a host; and   a membrane located over the electrode, the membrane comprising:
 a first domain that comprises an enzyme configured to react with glucose; 
 a second domain configured to reduce passage therethrough of an interferent, the second domain comprising a plurality of alternating polyelectrolyte layers, wherein the plurality of alternating polyelectrolyte layers comprise at least one of a polycationic layer and a polyanionic layer. 
   
     
     
         9 . The implantable device of  claim 8 , wherein the second domain comprises an odd number of alternating polyelectrolyte layers. 
     
     
         10 . The imlantable device of  claim 8 , wherein the second domain comprises a plurality of polycationic layers, and wherein the polycationic layers form the most distal layer and the most proximal layer of the second domain. 
     
     
         11 . The implantable device of  claim 8 , wherein the second domain comprises at least three alternating polyelectrolyte layers. 
     
     
         12 . The implantable device of  claim 11 , wherein the first and third most distal layers with respect to the electrode are polycationic layers, and the second most distal layer with respect to the electrode is a polyanionic layer. 
     
     
         13 . The implantable device of  claim 8 , wherein the second domain comprises at least five alternating polyelectrolyte layers. 
     
     
         14 . The implantable device of  claim 13 , wherein the first, third, and fifth most distal layers with respect to the electrode are polycationic layers, and the second and fourth most distal layers with respect to the electrode are polyanionic layers. 
     
     
         15 . The imlantable device of  claim 8 , wherein the second domain comprises at least seven alternating polyelectrolyte layers. 
     
     
         16 . The implantable device of  claim 15 , wherein the first, third, fifth, and seventh most distal layers with respect to the electrode are polycationic layers, and the second, fourth, and sixth most distal layers with respect to the sensor are polyanionic layers. 
     
     
         17 . The implantable device of  claim 8 , wherein the first domain is distal to the second domain with respect to the electrode. 
     
     
         18 . The implantable device of  claim 8 , wherein the electrode comprises an electroactive surface. 
     
     
         19 . The implantable device of  claim 18 , wherein the second domain contacts the electroactive surface. 
     
     
         20 . The imlantable device of  claim 8 , wherein the polycationic layer comprises a polycation with an average linear charge density from about 2 to 10 e/Å, and wherein the polyanionic layer comprises a polyanion with an average linear charge density from about 2 to 10 e/Å. 
     
     
         21 . The implantable device of  claim 8 , wherein the polycationic layer comprises a polycation with an average linear charge density from about 2 to 3 e/Å, and wherein the polyanionic layer comprises a polyanion with an average linear charge density from about 2 to 3 e/Å.