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 . An implantable device for measuring an analyte in a hydrophilic body fluid, comprising:
 (a) a polymeric membrane comprising (i) a matrix comprising a first polymer; and (ii) a second polymer dispersed throughout said matrix, wherein said second polymer forms a network of microdomains which are not photomicroscopically observable when hydrated at 400× magnification or less; and   (b) a proximal layer of enzyme reactive with said analyte.   
     
     
         2 . A method of monitoring glucose levels, comprising:
 (a) providing (i) a host, and (ii) an implantable device according to  claim 1 ; and   (b) implanting said device in said host.   
     
     
         3 . A method for preparing an implantable membrane comprising the steps of:
 (a) forming a composition comprising a dispersion of a second polymer within a matrix of a first polymer, said dispersion forming a network of microdomains which are not photomicroscopically observable when hydrated at 400× magnification or less;   (b) maintaining said composition at a temperature sufficient to maintain said first polymer and said second polymer substantially soluble;   (c) applying said composition at said temperature to a substrate to form a film thereon; and   (d) permitting said resultant film to dry to form said membrane.