Implantable enzyme-based monitoring systems adapted for long term use
First Claim
1. An implantable monitoring system comprising an enzyme solution and a reservoir, within the monitoring system, for replenishing the enzyme system;
- further comprising a sensor assembly for sensing a concentration of a substance being monitored;
wherein said sensor assembly includes a plurality of electrodes on a first side of a substrate and at least one hermetically sealed microprocessor on a second side of the substrate; and
further comprising hermetically sealed and electrically insulated conductive pathways from the at least one microprocessor to the plurality of electrodes;
further comprising said electrode assembly bathed in an electrolyte solution;
further comprising hermetically sealed and electrically insulated leads to a command center that supplies electrical power to the sensor assembly.
1 Assignment
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Accused Products
Abstract
Improved implantable monitoring systems suitable for long-term in vivo use to measure the concentration of one or more prescribed substances, such as glucose are described herein. In particular, an implantable enzyme-based glucose monitoring system is described that includes at least one of the following: means for replenishing the enzyme solution as it is consumed by the enzymatic reaction; means for replenishing the electrolyte solution bathing the electrode assembly; and microprocessing means proximal the electrode assembly. In preferred embodiments a microprocessor assembly is hermetically associated with the substrate to which the electrode assembly is affixed. Further, the monitoring systems employ one or more reservoir systems in fluid communication with enzyme and electrolyte chambers wherein the enzyme and electrolyte solutions are used. In a further embodiment, the monitoring systems use enzyme and electrolyte reservoir bulbs in fluid communication with the enzyme and electrolyte reservoirs, respectively, and positioned near the skin surface, thereby providing ready access to the enzyme and electrolyte solutions without the need for explantation of the device. Further provided herein is an enzyme solution including microspheres in association with the enzyme; whereby the enzyme is immobilized by the microspheres and the microspheres are in a fluid, flowable solution. Also provided herein is a method of extending the useful life of an implantable enzyme-based monitoring system, which method includes providing means, within the system, to replenish the enzyme and/or electrolyte solution.
1058 Citations
32 Claims
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1. An implantable monitoring system comprising an enzyme solution and a reservoir, within the monitoring system, for replenishing the enzyme system;
- further comprising a sensor assembly for sensing a concentration of a substance being monitored;
wherein said sensor assembly includes a plurality of electrodes on a first side of a substrate and at least one hermetically sealed microprocessor on a second side of the substrate; and
further comprising hermetically sealed and electrically insulated conductive pathways from the at least one microprocessor to the plurality of electrodes;
further comprising said electrode assembly bathed in an electrolyte solution;
further comprising hermetically sealed and electrically insulated leads to a command center that supplies electrical power to the sensor assembly. - View Dependent Claims (2, 3)
- further comprising a sensor assembly for sensing a concentration of a substance being monitored;
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4. An implantable monitoring system comprising an electrode assembly bathed in an electrolyte solution and a reservoir, within the monitoring system, for replenishing the electrolyte system;
- further comprising a sensor assembly means for sensing a concentration of a substance being monitored;
wherein said sensor assembly includes a plurality of electrodes on a first side of a substrate and at least one hermetically sealed microprocessor on a second side of the substrate;
further comprising said electrode assembly bathed in an electrolyte solution;
further comprising hermetically sealed and electrically insulated conductive pathways from the at least one microprocessor to the plurality of electrodes;
further comprising hermetically sealed and electrically insulated leads to a command center that supplies electrical power to the sensor assembly.
- further comprising a sensor assembly means for sensing a concentration of a substance being monitored;
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5. An implantable monitoring system comprising:
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an electrode assembly and associated electronics for monitoring prescribed substances; said electronics powered by an electrical energy source; said electrode assembly wherein a supply of fresh electrolyte acts to extend its life; an electrolyte chamber; an electrolyte reservoir in fluid communications with the electrolyte chamber; and an electrolyte solution with the electrolyte chamber and the electrolyte reservoir.
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6. An implantable monitoring system comprising:
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an electrode assembly and associated electronics for monitoring prescribed substances; said electronics powered by an electrical energy source; said electrode assembly wherein a supply of fresh electrolyte acts to extend its life;
an electrolyte chamber;an electrolyte solution within the electrolyte chamber; an electrolyte reservoir in fluid communication with the electrode chamber; an enzyme chamber proximate the electrolyte chamber; an enzyme solution within the enzyme chamber; and an enzyme reservoir in fluid communication with the chamber; said electrode assembly having current through it varied by the reactant products of reaction catalyzed by the enzyme fluid; said varying current being monitored by said associated electronics.
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7. An implantable monitoring system for determining the in vivo concentration of at least one prescribed substance, the system comprising:
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a housing, at least a portion of which is permeable to the at least one prescribed substance; an enzyme chamber within the housing; an enzyme chamber within the housing; an enzyme reservoir in fluid communication with the enzyme chamber; and an enzyme solution contained within the enzyme chamber and enzyme reservoir, further comprising; an electrolyte chamber within the housing; an electrode assembly within the electrolyte chamber; said electrode assembly and associated electronics for monitoring prescribed substances; an electrolyte reservoir in fluid communication with the electrolyte chamber; an electrolyte solution contained within the electrolyte chamber and electrolyte reservoir; said electrode assembly wherein a supply of fresh electrolyte acts to extend its life; said electrode assembly having current through it varied by the reactant products of reaction catalyzed by the enzyme fluid; said varying current being monitored by associated (with the electrode) electronics.
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8. An implantable monitoring system for determining the in vivo concentration of at least one prescribed substance, the system comprising:
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a housing, at least a portion of which is permeable to the at least one prescribed substance; a substrate within the housing; an electrode assembly affixed to the substrate and having an active surface; an electrolyte chamber surrounding the active surface of the electrode assembly; an electrolyte reservoir in fluid communication with the electrolyte chamber; and an electrolyte solution contained within the electrolyte chamber and electrolyte reservoir. - View Dependent Claims (9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19)
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20. An implantable enzyme-based monitoring system comprising microspheres wherein said microspheres immobilize an enzyme which acts to catalyze a reaction of a monitored substance;
- further comprising an electrical current measuring means;
whereby reaction products of said catalytic reaction which alter a current flowing through said electrical current measuring means;
further comprising a sensor assembly for sensing a concentration of a substance being monitored;
wherein said sensor assembly includes a plurality of electrodes on a first side of a substrate and at least one hermetically sealed microprocessor on a second side of the substrate;
further comprising said electrode assembly bathed in an electrolyte solution;
further comprising hermetically sealed and electrically insulated conductive pathways from the at least one electronic circuit to the at least one electrode;
further comprising hermetically sealed and electrically insulated leads to a command center that supplies electrical power to the sensor assembly.
- further comprising an electrical current measuring means;
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21. A monitoring system adapted for implantation into a patient to measure the in vivo concentration of one or more prescribed substances and to measure the in vivo background concentration of oxygen comprising a sensor assembly which further comprises;
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a substrate; a first working electrode bonded to the substrate; a reference electrode bonded to the substrate; a collector electrode bonded to the substrate; one or more electrical conducting connection(s) which contacts with the first working electrode, one or more second electrical connection(s) which contacts with the reference electrode, and one or more third electrical connection(s) which contacts with the collector electrode; a layer of insulation deposited on substrate and on said electrical conducting connection for making electrical contacts;
wherein said layer of insulation is interspersed between said electrodes bonded to said substrate;
further comprising an active surface of each of the electrodes being exposed through the layer of insulation, whereby said first working electrode, said reference electrode and said collector electrode are each electrically isolated from each other on the substrate;an electrolyte chamber formed by a first membrane covering said electrodes and affixed to said substrate; an electrolyte solution which is held within the electrolyte chamber by said first membrane covering affixed to the substrate;
further comprising said electrolyte solution in contact with the electrodes bonded to the substrate;a housing surrounding said first membrane and the substrate;
further comprising an opening in said housing above the active surface of the first working electrode;a second membrane which covers said opening in the housing;
wherein said second membrane is permeable to the one or more prescribed substances to be measured;first and second securing means for securing the substrate within the housing, the first and second securing structures being positioned at opposite ends of the substrate such that a first pocket is formed by the housing, the first membrane and the first and second securing means; a hydrophobic membrane within the pocket and above the active surface of the second working electrode, the hydrophobic membrane filling the portion of the pocket above the second electrode;
wherein said portion of the pocket, above the active surface of the first working electrode further comprises an enzyme chamber;a prescribed enzyme solution contained within said enzyme chamber; an enzyme reservoir within said housing; an enzyme channel in fluid communication with the enzyme reservoir and the enzyme chamber; an electrolyte reservoir within the housing and isolated from the enzyme reservoir further comprising the electrolyte reservoir containing an electrolyte solution; an electrolyte channel in fluid communication with the electrolyte reservoir and the electrolyte chamber; and powered electric circuitry in a microprocessor for applying a prescribed reference voltage between the collector electrode and the reference electrode, and between the first and second working electrodes and the reference electrodes, and for measuring the electrical current that flows from the first and second working electrodes, whereby, after implantation, oxygen internal to the body penetrates the housing, the hydrophobic membrane and the first membrane means and alters the current flowing through said second working electrode, further comprising a measurement of in vivo background concentration of oxygen; and whereby, after implantation, one or more prescribed substances to be measured may penetrate into the enzyme chamber through the second membrane, react, in the presence of the prescribed enzyme, with oxygen that has penetrated into the enzyme of the prescribed enzyme, with oxygen that has penetrated into the enzyme chamber;
further comprising said products of said reaction penetrating said first membrane and altering the current flowing through the first working electrode further comprising a measurement of the concentrations of the one or more prescribed substances.
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22. A monitoring system adapted for implantation into a patient to measure the in vivo concentration of one or more prescribed substances and to measure the in vivo background concentration of oxygen comprising a sensor assembly which further comprises;
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a substrate; a first working electrode bonded to the substrate; a reference electrode bonded to the substrate; a collector electrode bonded to the substrate; one or more electrical conducting connection(s) which contacts with the first working electrode, one or more second electrical connection(s) which contacts with the reference electrode, and one or more third electrical connection(s) which contacts with the collector electrode; a layer of insulation deposited on said substrate and on said electrical conducting connection for making electrical contacts;
wherein said layer of insulation is interspersed between said electrodes bonded to said substrate;
further comprising an active surface of each of the electrodes being exposed through the layer of insulation, whereby said first working electrode, said reference electrode and said collector electrode are each electrically isolated from each other on the substrate;an electrolyte chamber formed by a first membrane covering said electrodes and affixed to said substrate; an electrolyte solution which is held within the electrolyte chamber by said first membrane covering affixed to the substrate;
further comprising said electrolyte solution in contact with the electrodes bonded to the substrate;a housing surrounding said first membrane and the substrate;
further comprising an opening in said housing above the active surface of the first working electrode;a second membrane which covers said opening in the housing;
wherein said second membrane is permeable to the one or more prescribed substances to be measured;first and second securing means for securing the substrate within the housing, the first and second securing structures being positioned at opposite ends of the substrate such that a first pocket is formed by the housing, the first membrane and the first and second securing means; a hydrophobic membrane within the pocket and above the active surface of the second working electrode, the hydrophobic membrane filling the portion of the pocket above the second electrode;
wherein said portion of the pocket, above the active surface of the first working electrode further comprises an enzyme chamber;a prescribed enzyme solution contained within said enzyme chamber; an enzyme reservoir within said housing; an enzyme channel in fluid communication with the enzyme reservoir and the enzyme chamber; an electrolyte reservoir within the housing and isolated from the enzyme reservoir;
further comprising the electrolyte reservoir containing an electrolyte solution;an electrolyte channel in fluid communication with the electrolyte reservoir and the electrolyte chamber; and powered electric circuitry in a microprocessor for applying a prescribed reference voltage between the collector electrode and the reference electrode, and between the first and second working electrodes and the reference electrodes, and for measuring the electrical current that flows from the first and second working electrodes, whereby, after implantation, oxygen internal to the body penetrates the housing, the hydrophobic membrane and the first membrane means and alters the current flowing through said second working electrode, further comprising a measurement of in vivo background concentration of oxygen; and whereby, after implantation, one or more prescribed substances to be measured may penetrate into the enzyme chamber through the second membrane, react, in the presence of the prescribed enzyme, with oxygen that has penetrated into the enzyme of the prescribed enzyme, with oxygen that has penetrated into the enzyme chamber;
further comprising said products of said reaction penetrating said first membrane and altering the current flowing through the first working electrode further comprising a measurement of the concentrations of the one or more prescribed substances,further comprising a microprocessor assembly, hermetically bonded to the substrate.
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23. A monitoring system adapted for implantation into a patient to measure the in vivo concentration of one or more prescribed substances and to measure the in vivo background concentration of oxygen comprising a sensor assembly which further comprises;
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a substrate; a first working electrode bonded to the substrate; a reference electrode bonded to the substrate; a collector electrode bonded to the substrate; one or more electrical conducting connection(s) which contacts with the first working electrode, one or more second electrical connection(s) which contacts with the reference electrode, and one or more third electrical connection(s) which contacts with the collector electrode; a layer of insulation deposited on said substrate and on said electrical conducting connection for making electrical contacts;
wherein said layer of insulation is interspersed between said electrodes bonded to said substrate;
further comprising an active surface of each of the electrodes being exposed through the layer of insulation, whereby said first working electrode, said reference electrode and said collector electrode are each electrically isolated from each other on the substrate;an electrolyte chamber formed by a first membrane covering said electrodes and affixed to said substrate; an electrolyte solution which is held within the electrolyte chamber by said first membrane covering affixed to the substrate;
further comprising said electrolyte solution in contact with the electrodes bonded to the substrate;a housing surrounding said first membrane and the substrate;
further comprising an opening in said housing above the active surface of the first working electrode;a second membrane which covers said opening in the housing;
wherein said second membrane is permeable to the one or more prescribed substances to be measured;first and second securing means for securing the substrate within the housing, the first and second securing structures being positioned at opposite ends of the substrate such that a first pocket is formed by the housing, the first membrane and the first and second securing means; a hydrophobic membrane within the pocket and above the active surface of the second working electrode, the hydrophobic membrane filling the portion of the pocket above the second electrode;
wherein said portion of the pocket, above the active surface of the first working electrode further comprises an enzyme chamber;a prescribed enzyme solution contained within said enzyme chamber; an enzyme reservoir within said housing; an enzyme channel in fluid communication with the enzyme reservoir and the enzyme chamber; an electrolyte reservoir within the housing and isolated from the enzyme reservoir;
further comprising the electrolyte reservoir containing an electrolyte solution;an electrolyte channel in fluid communication with the electrolyte reservoir and the electrolyte chamber; and powered electric circuitry in a microprocessor for applying a prescribed reference voltage between the collector electrode and the reference electrode, and between the first and second working electrodes and the reference electrodes, and for measuring the electrical current that flows from the first and second working electrodes, whereby, after implantation, oxygen internal to the body penetrates the housing, the hydrophobic membrane and the first membrane means and alters the current flowing through said second working electrode, further comprising a measurement of in vivo background concentration of oxygen; and whereby, after implantation, one or more prescribed substances to be measured may penetrate into the enzyme chamber through the second membrane, react, in the presence of the prescribed enzyme, with oxygen that has penetrated into the enzyme of the prescribed enzyme, with oxygen that has penetrated into the enzyme chamber;
further comprising said products of said reaction penetrating said first membrane and altering the current flowing through the first working electrode further comprising a measurement of the concentrations of the one or more prescribed substances more prescribed substances;further comprising a microprocessor assembly, hermetically bonded to the substrate;
wherein the securing means are epoxy plugs.
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24. A monitoring system adapted for implantation into a patient to measure the in vivo concentration of one or more prescribed substances and to measure the in vivo background concentration of oxygen comprising a sensor assembly which further comprises;
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a substrate; a first working electrode bonded to the substrate; a reference electrode bonded to the substrate; a collector electrode bonded to the substrate; one or more electrical conducting connection(s) which contacts with the first working electrode, one or more second electrical connection(s) which contacts with the reference electrode, and one or more third electrical connection(s) which contacts with the collector electrode; a layer of insulation deposited on said substrate and on said electrical conducting connection for making electrical contacts;
wherein said layer of insulation is interspersed between said electrodes bonded to said substrate;
further comprising an active surface of each of the electrodes being exposed through the layer of insulation, whereby said first working electrode, said reference electrode and said collector electrode are each electrically isolated from each other on the substrate;an electrolyte chamber formed by a first membrane covering said electrodes and affixed to said substrate; an electrolyte solution which is held within the electrolyte chamber by said first membrane covering affixed to the substrate;
further comprising said electrolyte solution in contact with the electrodes bonded to the substrate;a housing surrounding said first membrane and the substrate;
further comprising an opening in said housing above the active surface of the first working electrode;a second membrane which covers said opening in the housing;
wherein said second membrane is permeable to the one or more prescribed substances to be measured;first and second securing means for securing the substrate within the housing, the first and second securing structures being positioned at opposite ends of the substrate such that a first pocket is formed by the housing, the first membrane and the first and second securing means; a hydrophobic membrane within the pocket and above the active surface of the second working electrode, the hydrophobic membrane filling the portion of the pocket above the second electrode;
wherein said portion of the pocket, above the active surface of the first working electrode further comprises an enzyme chamber;a prescribed enzyme solution contained within said enzyme chamber; an enzyme reservoir within said housing; an enzyme channel in fluid communication with the enzyme reservoir and the enzyme chamber; an electrolyte reservoir within the housing and isolated from the enzyme reservoir;
further comprising the electrolyte reservoir containing an electrolyte solution;an electrolyte channel in fluid communication with the electrolyte reservoir and the electrolyte chamber; and powered electric circuitry in a microprocessor for applying a prescribed reference voltage between the collector electrode and the reference electrode, and between the first and second working electrodes and the reference electrodes, and for measuring the electrical current that flows from the first and second working electrodes, whereby, after implantation, oxygen internal to the body penetrates the housing, the hydrophobic membrane and the first membrane means and alters the current flowing through said second working electrode, further comprising a measurement of in vivo background concentration of oxygen; and whereby, after implantation, one or more prescribed substances to be measured may penetrate into the enzyme chamber through the second membrane, react, in the presence of the prescribed enzyme, with oxygen that has penetrated into the enzyme of the prescribed enzyme, with oxygen that has penetrated into the enzyme chamber;
further comprising said products of said reaction penetrating said first membrane and altering the current flowing through the first working electrode further comprising a measurement of the concentrations of the one or more prescribed substances, more prescribed substances;further comprising a microprocessor assembly, hermetically bonded to the substrate; wherein the securing means are epoxy plugs; wherein the prescribed enzyme solution comprises microspheres in association with a prescribed enzyme.
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25. A monitoring system adapted for implantation into a patient to measure the in vivo concentration of one or more prescribed substances and to measure the in vivo background concentration of oxygen comprising a sensor assembly which further comprises;
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a substrate; a first working electrode bonded to the substrate; a reference electrode bonded to the substrate; a collector electrode bonded to the substrate; one or more electrical conducting connection(s) which contacts with the first working electrode, one or more second electrical connection(s) which contacts with the reference electrode, and one or more third electrical connection(s) which contacts with the collector electrode; a layer of insulation deposited on said substrate and on said electrical conducting connection for making electrical contacts;
wherein said layer of insulation is interspersed between said electrodes bonded to said substrate;
further comprising an active surface of each of the electrodes being exposed through the layer of insulation, whereby said first working electrode, said reference electrode and said collector electrode are each electrically isolated from each other on the substrate;an electrolyte chamber formed by a first membrane covering said electrodes and affixed to said substrate; an electrolyte solution which is held within the electrolyte chamber by said first membrane covering affixed to the substrate;
further comprising said electrolyte solution in contact with the electrodes bonded to the substrate;a housing surrounding said first membrane and the substrate;
further comprising an opening in said housing above the active surface of the first working electrode;a second membrane which covers said opening in the housing;
wherein said second membrane is permeable to the one or more prescribed substances to be measured;first and second securing means for securing the substrate within the housing, the first and second securing structures being positioned at opposite ends of the substrate such that a first pocket is formed by the housing, the first membrane and the first and second securing means; a hydrophobic membrane within the pocket and above the active surface of the second working electrode, the hydrophobic membrane filling the portion of the pocket above the second electrode;
wherein said portion of the pocket, above the active surface of the first working electrode further comprises an enzyme chamber;a prescribed enzyme solution contained within said enzyme chamber; an enzyme reservoir within said housing; an enzyme channel in fluid communication with the enzyme reservoir and the enzyme chamber; an electrolyte reservoir within the housing and isolated from the enzyme reservoir;
further comprising the electrolyte reservoir containing an electrolyte solution;an electrolyte channel in fluid communication with the electrolyte reservoir and the electrolyte chamber; and powered electric circuitry in a microprocessor for applying a prescribed reference voltage between the collector electrode and the reference electrode, and between the first and second working electrodes and the reference electrodes, and for measuring the electrical current that flows from the first and second working electrodes, whereby, after implantation, oxygen internal to the body penetrates the housing, the hydrophobic membrane and the first membrane means and alters the current flowing through said second working electrode, further comprising a measurement of in vivo background concentration of oxygen; and whereby, after implantation, one or more prescribed substances to be measured may penetrate into the enzyme chamber through the second membrane, react, in the presence of the prescribed enzyme, with oxygen that has penetrated into the enzyme of the prescribed enzyme, with oxygen that has penetrated into the enzyme chamber;
further comprising said products of said reaction penetrating said first membrane and altering the current flowing through the first working electrode further comprising a measurement of the concentrations of the one or more prescribed substances more prescribed substances;further comprising a microprocessor assembly, hermetically bonded to the substrate; wherein the securing means are epoxy plugs; wherein the prescribed enzyme solution comprises microspheres in association with a prescribed enzyme; wherein the prescribed enzyme is glucose oxidase.
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26. In an implantable monitoring system employing an enzyme solution, a method of extending the life of the system, comprising providing at least one reservoir and at least one enzyme solution channel connecting said reservoir with a reaction region within the system, to replenish the enzyme solution;
- further comprising a sensor assembly for sensing a concentration of a substance being monitored;
wherein said sensor assembly includes a plurality of electrodes on a first side of a substrate and at least one hermetically sealed microprocessor on a second side of the substrate;
further comprising said electrode assembly bathed in an electrolyte solution;
further comprising hermetically sealed and electrically insulated conductive pathways from the at least one electronic circuit to the at least one electrode;
further comprising hermetically sealed and electrically insulated leads to a command center that supplies electrical power to the sensor assembly.
- further comprising a sensor assembly for sensing a concentration of a substance being monitored;
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27. An implantable monitoring system comprising an electrode assembly bathed in an electrolyte solution;
- further comprising one or more electrolyte reservoirs and one or more electrolyte channels, within the system, to replenish the electrolyte solution;
wherein the useable life of said electrode assembly is extended;
further comprising a sensor assembly for sensing a concentration of a substance being monitored;
wherein said sensor assembly includes a plurality of electrodes on a first side of a substrate and at least one hermetically sealed microprocessor on a second side of the substrate;
further comprising said electrode assembly bathed in an electrolyte solution;
further comprising hermetically sealed and electrically insulated conductive pathways from the at least one electronic circuit to the at least one electrode;
further comprising hermetically sealed and electrically insulated leads to a command center that supplies electrical power to the sensor assembly.
- further comprising one or more electrolyte reservoirs and one or more electrolyte channels, within the system, to replenish the electrolyte solution;
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28. An implantable monitoring system for monitoring a substance, comprising:
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a plurality of electrodes mounted on a substrate and electrically connected to a source of electric power; at least one microelectronic component mounted on the substrate for monitoring a current flowing through at least one or the electrodes during operation of the monitoring system whereby the monitored current is used in monitoring the substance; and a fluid solution within the monitoring system that is altered by operation of the monitoring system such that the monitored current no longer effectively monitors the substance; and means, within the monitoring system, for replacing the altered fluid solution with unaltered fluid solution so as to extend the life of the monitoring system. - View Dependent Claims (29, 30)
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31. An implantable monitoring system for monitoring a substance comprising a fluid solution that is altered by operation of a monitoring system and means within the monitoring system, for replacing the altered fluid solution with unaltered fluid solution;
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said implantable monitoring system further comprising a reservoir system as the means for replacing the altered fluid solution; said implantable monitoring system further comprising an electrolyte solution as the fluid solution wherein said monitoring system further comprises one or more electrode(s) connected to a source of electric power and in electrical contact with the electrolyte solution; a current measuring means for monitoring a current flowing through at least one of the electrodes during operation of the monitoring system whereby the measured current is used in monitoring the substance.
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32. An implantable monitoring system for monitoring a substance comprising a fluid solution that is altered by operation of the monitoring system and a means within the monitoring system, for replacing the altered fluid solution with unaltered fluid solution;
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said implantable monitoring system further comprising a reservoir system as the means for replacing the altered fluid solution; said implantable monitoring system further comprising two fluid solutions, one of which is an enzyme solution and the other of which is an electrolyte solution;
wherein said monitoring system further comprises one or more electrode(s) connected to a source of electric power and in electrical contact with the electrolyte solution;a current measuring means for monitoring a current flowing through at least one of the electrodes during operation of the monitoring system whereby the measured current is used in monitoring the substance.
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Specification