Electrode systems for electrochemical sensors

Abstract

The present invention relates generally to systems and methods for improved electrochemical measurement of analytes. The preferred embodiments employ electrode systems including an analyte-measuring electrode for measuring the analyte or the product of an enzyme reaction with the analyte and an auxiliary electrode configured to generate oxygen and/or reduce electrochemical interferants. Oxygen generation by the auxiliary electrode advantageously improves oxygen availability to the enzyme and/or counter electrode; thereby enabling the electrochemical sensors of the preferred embodiments to function even during ischemic conditions. Interferant modification by the auxiliary electrode advantageously renders them substantially non-reactive at the analyte-measuring electrode, thereby reducing or eliminating inaccuracies in the analyte signal due to electrochemical interferants.

1 . An electrochemical sensor for determining a presence or a concentration of an analyte in a fluid, the sensor comprising:
 a membrane system comprising an enzyme, wherein the enzyme reacts with the analyte;   an electroactive surface comprising a working electrode, the working electrode comprising a conductive material and configured to measure a product of the reaction of the enzyme with the analyte; and   an auxiliary electrode comprising a conductive material and configured to generate oxygen, wherein the auxiliary electrode is situated such that the oxygen generated diffuses to the enzyme or to the electroactive surface.   
     
     
         2 . The electrochemical sensor of  claim 1 , wherein the auxiliary electrode comprises a conductive material selected from the group consisting of a conductive metal, a conductive polymer, and a blend of a conductive metal and a conductive polymer. 
     
     
         3 . The electrochemical sensor of  claim 1 , wherein the auxiliary electrode comprises a form selected from the group consisting of a mesh, a grid, and a plurality of spaced wires. 
     
     
         4 . The electrochemical sensor of  claim 1 , wherein the auxiliary electrode comprises a polymer, wherein the polymer is situated on a surface of the auxiliary electrode. 
     
     
         5 . The electrochemical sensor of  claim 4 , wherein the polymer comprises a material that is impermeable to glucose but is permeable to oxygen. 
     
     
         6 . The electrochemical sensor of  claim 4 , wherein the polymer comprises a material that is impermeable to glucose but is permeable to oxygen and permeable to interfering species. 
     
     
         7 . The electrochemical sensor of  claim 6 , wherein the polymer comprises a material having a molecular weight that blocks glucose and allows transport therethrough of oxygen, urate, ascorbate, and acetaminophen. 
     
     
         8 . The electrochemical sensor of  claim 4 , wherein the polymer comprises a material that is permeable to glucose and oxygen. 
     
     
         9 . The electrochemical sensor of  claim 4 , wherein the polymer comprises a material that is permeable to glucose, oxygen, and interfering species. 
     
     
         10 . The electrochemical sensor of  claim 9 , wherein the polymer comprises a material having a molecular weight that allows transport therethrough of oxygen, glucose, urate, ascorbate, and acetaminophen. 
     
     
         11 . The electrochemical sensor of  claim 1 , wherein the auxiliary electrode is configured to be set at a potential of at least about +0.6 V. 
     
     
         12 . The electrochemical sensor of  claim 1 , wherein the auxiliary electrode is configured to electrochemically modify an electrochemical interferant to render the electrochemical interferent substantially electrochemically non-reactive at the working electrode. 
     
     
         13 . The electrochemical sensor of  claim 12 , wherein the auxiliary electrode is configured to be set at a potential of at least about +0.1 V. 
     
     
         14 . An electrochemical sensor for determining a presence or a concentration of an analyte in a fluid, the sensor comprising:
 a membrane system comprising an enzyme, wherein the enzyme reacts with the analyte;   an electroactive surface comprising a working electrode, the working electrode comprising a conductive material and configured to measure a product of the reaction of the enzyme with the analyte; and   an auxiliary electrode comprising a conductive material and configured to modify an electrochemical interferant such that the electrochemical interferent is rendered substantially electrochemically non-reactive at the working electrode.   
     
     
         15 . The electrochemical sensor of  claim 14 , wherein the auxiliary electrode comprises a conductive material selected from the group consisting of a conductive metal, a conductive polymer, and a blend of a conductive metal and a conductive polymer. 
     
     
         16 . The electrochemical sensor of  claim 14 , wherein the auxiliary electrode comprises a form selected from the group consisting of a mesh, a grid, and a plurality of spaced wires. 
     
     
         17 . The electrochemical sensor of  claim 14 , wherein the auxiliary electrode comprises a polymer, wherein the polymer is situated on a surface of the auxiliary electrode. 
     
     
         18 . The electrochemical sensor of  claim 17 , wherein the polymer comprises a material that is permeable to an electrochemical interferant. 
     
     
         19 . The electrochemical sensor of  claim 17 , wherein the polymer comprises a material that is impermeable to glucose but is permeable to oxygen. 
     
     
         20 . The electrochemical sensor of  claim 17 , wherein the polymer comprises a material that is impermeable to glucose but is permeable to oxygen and interferants. 
     
     
         21 . The electrochemical sensor of  claim 17 , wherein the polymer comprises a material having a molecular weight that blocks glucose and allows transport therethrough of oxygen, urate, ascorbate, and acetaminophen. 
     
     
         22 . The electrochemical sensor of  claim 17 , wherein the polymer comprises a material that is permeable to glucose and oxygen. 
     
     
         23 . The electrochemical sensor of  claim 17 , wherein the polymer comprises a material that is permeable to glucose, oxygen, and interferants. 
     
     
         24 . The electrochemical sensor of  claim 23 , wherein the polymer comprises a material having a molecular weight that allows transport therethrough of oxygen, glucose, urate, ascorbate, and acetaminophen. 
     
     
         25 . The electrochemical sensor of  claim 14 , wherein the auxiliary electrode is configured to be set at a potential of at least about +0.1V. 
     
     
         26 . The electrochemical sensor of  claim 14 , wherein the auxiliary electrode is configured to generate oxygen. 
     
     
         27 . The electrochemical sensor of  claim 26 , wherein the auxiliary electrode is configured to be set at a potential of at least about +0.6 V. 
     
     
         28 . An electrochemical sensor comprising:
 an electroactive surface configured to measure an analyte; and   an auxiliary interferant-modifying electrode configured to modify an electrochemical interferant such that the electrochemical interferant is rendered substantially non-reactive at the electroactive surface.   
     
     
         29 . The electrochemical sensor of  claim 28 , wherein the auxiliary interferant-modifying electrode comprises a conductive material selected from the group consisting of a conductive metal, a conductive polymer, and a blend of a conductive metal and a conductive polymer. 
     
     
         30 . The electrochemical sensor of  claim 28 , wherein the auxiliary interferant-modifying electrode comprises a form selected from the group consisting of a mesh, a grid, and a plurality of spaced wires. 
     
     
         31 . The electrochemical sensor of  claim 28 , wherein the auxiliary interferant-modifying electrode comprises a polymer, wherein the polymer is situated on a surface of the auxiliary interferant-modifying electrode.