Subcutaneous Glucose Electrode

Abstract

A small diameter flexible electrode designed for subcutaneous in vivo amperometric monitoring of glucose is described. The electrode is designed to allow “one-point” in vivo calibration, i.e., to have zero output current at zero glucose concentration, even in the presence of other electroreactive species of serum or blood. The electrode is preferably three or four-layered, with the layers serially deposited within a recess upon the tip of a polyamide insulated gold wire. A first glucose concentration-to-current transducing layer is overcoated with an electrically insulating and glucose flux limiting layer (second layer) on which, optionally, an immobilized interference-eliminating horseradish peroxidase based film is deposited (third layer). An outer (fourth) layer is biocompatible.

1 . (canceled) 
   
   
       2 . A method of detecting an analyte in a host, comprising:
 a) inserting a sensor through a host's skin and into the host, wherein the sensor is a component of an analyte sensing device configured for transcutaneous insertion into the host, wherein the sensor has an architecture with at least one dimension less than about 1 mm, and wherein a biointerface covers at least a portion of the sensor, whereby fluid flows into the biointerface upon insertion of the sensor into the host;   b) detecting from the sensor a signal indicative of a presence or a concentration of the analyte in the host; and   c) removing the sensor from the host.   
   
   
       3 . The method of  claim 2 , further comprising repeating steps a) through c) within about 14 days or less. 
   
   
       4 . The method of  claim 2 , further comprising coupling an electronics unit to the sensor. 
   
   
       5 . A method for fabricating an analyte sensor configured for insertion into a host's soft tissue, the method comprising:
 forming a biointerface having a plurality of passageways and a solid portion on at least a sensing portion of a sensor,   wherein the sensor is configured to measure an analyte in the host, and wherein the sensor has an architecture with at least one dimension less than about 1 mm.   
   
   
       6 . The method of  claim 5 , wherein the step of forming a biointerface comprises a method selected from the group consisting of writing, lyophilizing, and weaving. 
   
   
       7 . The method of  claim 5 , wherein the step of forming a biointerface comprises electrospinning the biointerface onto the sensor, writing the biointerface onto the sensor, lyophilizing the biointerface onto the sensor, and weaving the biointerface onto the sensor. 
   
   
       8 . The method of  claim 5 , wherein the step of forming a biointerface comprises forming the biointerface directly on the sensor. 
   
   
       9 . The method of  claim 5 , wherein the step of forming a biointerface comprises pre-forming the biointerface and then at least one of applying the preformed biointerface to the sensor, and inserting the sensor into the preformed biointerface. 
   
   
       10 . The method of  claim 5 , wherein the step of forming a biointerface comprises:
 forming a selectively removable porogen on the sensor, wherein the porogen comprises particles formed onto the sensor and solidified to form a solidified mass of continuously interconnected particles;   filling the porogen with a material;   substantially solidifying the material; and   removing the mass of continuously interconnected particles from contact with the sensor and solidified material to thereby form a solid portion that defines a plurality of passageways of the biointerface.   
   
   
       11 . The method of  claim 5 , wherein the step of forming a biointerface comprises writing a biointerface onto the sensor using a computer-aided machine. 
   
   
       12 . A method for fabricating an analyte sensor configured to be wholly implanted in a host's soft tissue, the method comprising:
 providing a sensor configured to measure an analyte in the host, wherein the sensor has an architecture with at least one dimension less than about 1 mm; and   coating a biointerface onto the sensor, the biointerface comprising a plurality of cavities and a solid portion.   
   
   
       13 . The method of  claim 12 , wherein the coating step comprises a method selected from the group consisting of writing, lyophilizing, and weaving. 
   
   
       14 . The method of  claim 12 , further comprising a step of curing the biointerface. 
   
   
       15 . The method of  claim 12 , wherein the coating step comprises:
 forming a selectively removable porogen onto the sensor, wherein the porogen comprises particles formed onto the sensor and solidified to form a solidified mass of continuously interconnected particles;   filling the porogen with a material;   substantially solidifying the material; and   removing the mass of continuously interconnected particles from contact with the sensor and solidified material to thereby form a solid portion that defines a plurality of passageways of the biointerface.   
   
   
       16 . The method of  claim 12 , wherein the coating step comprises writing a biointerface onto the sensor using a computer-aided machine. 
   
   
       17 . The method of  claim 12 , further comprising a step of curing the biointerface. 
   
   
       18 . A method for making an analyte sensor configured for insertion into a host's soft tissue, the method comprising:
 providing a sensor configured to measure an analyte in a host, wherein the sensor has an architecture with at least one dimension less than about 1 mm; and   directly writing a porous biointerface, wherein the porous biointerface is written based on a predefined pattern stored in a computer system.   
   
   
       19 . The method of  claim 18 , further comprising a step of curing the biointerface during direct writing step or after the direct writing step. 
   
   
       20 . The method of  claim 18 , wherein the porous biointerface is directly written onto the sensor. 
   
   
       21 . The method of  claim 18 , wherein the porous biointerface is directly written onto a substrate and then applied to the sensor.