Sensor membrane for dexamethasone suppression

Abstract

Embodiments of the present invention provide amperometric analyte sensors having optimized elements, such as dexamethasone inhibiting membranes, and methods for making and using such sensors. The amperometric analyte sensor device includes: a substrate layer; a conductive layer disposed on the base layer and including a working electrode; a dexamethasone suppression membrane disposed over the electroactive surface of the working electrode, where the interference suppression membrane comprises a polyHema composition and an analyte sensing layer. Although embodiments of the invention may be used in a variety of situations, typical embodiments of the invention include glucose sensors for managing diabetes.

Description

[0001] CROSS-REFERENCE TO RELATED APPLICATIONS

[0002] This application claims the benefit under 35 U.S.C. § 119(e) of co-pending and commonly assigned U.S. Provisional Patent Application No. 63 / 562,394, filed on March 7, 2024, entitled “SENSOR MEMBRANES FOR DEXAMETHOSONE REJECTION,” which is incorporated herein by reference. Technical Field

[0003] Amperometric analyte sensors (e.g., glucose sensors for managing diabetes) and methods and materials for making and using such sensors. Background Art

[0004] Analyte sensors, such as biosensors, include devices that use biological elements to convert a chemical analyte in a matrix into a detectable signal. There are many types of biosensors for a wide variety of analytes. The most studied type of biosensor is the amperometric glucose sensor, which is crucial for successful glucose level control in diabetes.

[0005] A typical glucose sensor works based on the following chemical reaction:

[0006]

[0007] H2O2→O2+2H + +2e - Formula 2

[0008] Glucose oxidase catalyzes the reaction between glucose and oxygen to produce gluconic acid and hydrogen peroxide (Equation 1). H2O2 undergoes an electrochemical reaction, as shown in Equation 2, and the current can be measured by a potentiostat. These reactions, which occur in various oxidoreductases known in the art, are used in many sensor designs.

[0009] Dexamethasone acetate (DXAC) can be used as an anti-inflammatory agent with implantable analytical sensors, for example to extend the sensor's in vivo lifespan. However, when exposed to DXAC, amperometric sensor readings (also known as iSig) can be negatively impacted. For example, certain continuous glucose monitoring (CGM) amperometric sensors are designed to experience a decrease in iSig when exposed to DXAC. In such cases, it would be desirable to minimize the effects of DXAC on such sensors in order to maintain and improve sensor accuracy.

[0010] For the reasons stated above, it would be desirable to devise methods and materials for overcoming the difficulties with amperometric sensors caused by the use of dexamethasone. Summary of the Invention

[0011] Embodiments of the present invention described herein include a dexamethasone acetate inhibitory membrane (DRM) that is made of selected materials to prevent dexamethasone from penetrating into the sensing element of the current-type sensor. In illustrative embodiments, the membrane can be composed of various poly (2-hydroxyethyl methacrylate) ("poly-Hema") compositions of various formulations and can be incorporated into the sensor at various locations. The DRM can be composed of a polymerization reaction mixture (e.g., a mixture comprising HEMA monomers) of pre-polymerized polyHEMA or polyHEMA molecules that do not have pre-polymerized polyHEMA. Embodiments of the present invention can further customize the thickness and permeability of the DRM layer so that it does not interfere with (or limit) the glucose diffusion rate of the sensor while preventing dexamethasone from affecting the glucose sensor signal. In addition, the DRM can be a thin layer (like a cover layer) placed on top of the outermost chemical layer of the glucose sensor (which is typically a glucose limiting membrane (GLM)). Alternatively, the DRM can be placed below the GLM. In certain embodiments of the present invention, an additional advantage is that the DRM layer can further reduce the impact of acetaminophen (AC) and other interferents on the glucose sensor signal, thereby further improving the sensor signal accuracy.

[0012] As described above, the present invention provides methods and materials designed to maintain and improve sensor accuracy and address sensor reading difficulties caused by dexamethasone. Embodiments of the present invention include membrane compositions that can be used, for example, as a barrier to dexamethasone in amperometric analyte sensors and sensor systems, such as amperometric glucose sensors commonly used for diabetes management. Specifically, embodiments of the present invention include dexamethasone-inhibiting membranes (DRMs). Sensors including these membranes have demonstrated dexamethasone inhibition, excellent oxygen effect properties, and in vivo and in vitro performance.

[0013] The invention disclosed herein has numerous embodiments. Embodiments of the invention include, for example, methods of making a sensor device for implantation in a mammal. Generally, these methods include the steps of providing a substrate layer; forming a conductive layer on the substrate layer, wherein the conductive layer comprises a working electrode; forming a dexamethasone-inhibiting membrane above the working electrode; forming an analyte sensing layer, wherein the analyte sensing layer comprises an oxidoreductase; and forming an analyte modulating layer, wherein the analyte modulating layer comprises a composition that modulates diffusion of the analyte through the analyte modulating layer.

[0014] In certain embodiments of the method of making a sensor device for implantation in a mammal, the dexamethasone-inhibiting membrane comprises approximately: 50% (w / v) to 80% (w / v) tetra(ethylene glycol) diacrylate in combination with 0.5% (w / v) to 10% (w / v) methacryloxyethyl phosphorylcholine (MPC). In some embodiments of the method of making a sensor device for implantation in a mammal, the dexamethasone-inhibiting membrane comprises approximately: 60% (w / v) to 70% (w / v) tetra(ethylene glycol) diacrylate in combination with 1.0% (w / v) to 1% (w / v) methacryloxyethyl phosphorylcholine (MPC).

[0015] Embodiments of the present invention also include sensor devices for implantation in a mammal. Generally, such sensors include: a substrate layer; a conductive layer disposed on the substrate layer, wherein the conductive layer includes a working electrode; a dexamethasone-inhibiting membrane disposed on the working electrode, wherein the dexamethasone-inhibiting membrane includes a poly(2-hydroxyethyl methacrylate) composition; an analyte-sensing layer disposed above the dexamethasone-inhibiting membrane, wherein the analyte-sensing layer includes an oxidoreductase; and an analyte-modulating layer disposed above the analyte-sensing layer, wherein the analyte-modulating layer includes a composition that modulates diffusion of the analyte through the analyte-modulating layer.

[0016] Other embodiments of the present invention include methods for estimating the concentration of an analyte (such as glucose in vivo), which methods include placing a sensor device disclosed herein in an in vivo environment of a subject, wherein the environment includes an analyte (such as glucose in vivo); and estimating the concentration of the analyte; such that the concentration of the in vivo analyte is estimated.

[0017] For those skilled in the art, other objects, features and advantages of the present invention will become apparent from the following detailed description. However, it should be understood that although the detailed description and specific examples indicate some embodiments of the present invention, they are provided by way of illustration and not limitation. Without departing from the spirit of the present invention, many changes and modifications may be made within the scope of the present invention, and the present invention includes all such modifications. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] Figure 1A schematic diagram of the well-known reaction between glucose and glucose oxidase is provided. As shown in a step-by-step manner, the reaction involves glucose oxidase (GOx), glucose, and oxygen in water. In the reduction half of the reaction, two protons and an electron are transferred from β-D-glucose to the enzyme that produces d-gluconolactone. In the oxidation half of the reaction, the enzyme is oxidized by molecular oxygen to produce hydrogen peroxide. d-gluconolactone then reacts with water to hydrolyze the lactone ring and produce gluconic acid. In certain electrochemical sensors of the present invention, the hydrogen peroxide produced by this reaction is oxidized at the working electrode (H2O2 → 2H + +O2+2e - ).

[0019] Figure 2A A diagrammatic view of an embodiment of an amperometric analyte sensor to which a dexamethasone inhibitory membrane can be added is provided. Figure 2B A diagrammatic view of an embodiment of an amperometric analyte sensor having a dexamethasone-inhibiting membrane 120 is provided.

[0020] Figure 3A and Figure 3B is a diagram showing the design of a Dex-repressing membrane (DRM). Figure 3A Three panels are provided showing diagrammatic representations of an embodiment of an amperometric analyte sensor having a dexamethasone-inhibiting membrane. The upper left and upper right panels provide diagrammatic representations of an embodiment of an amperometric analyte sensor comprising multiple layered elements including a dexamethasone-inhibiting membrane. The lower panel provides cartoon representations of methods and molecules that can be used to make a PHEMA membrane. Figure 3B Three panels are provided that illustrate diagrammatic representations of an embodiment of an amperometric analyte sensor having a dexamethasone-inhibiting membrane. The left panel provides a diagrammatic representation of an embodiment of an amperometric analyte sensor comprising a plurality of layered elements including a dexamethasone-inhibiting membrane disposed within a layer. The middle panel provides a diagrammatic representation of an embodiment of an amperometric analyte sensor comprising a plurality of layered elements including a dexamethasone-inhibiting membrane disposed as an outer layer. The right panel provides a diagrammatic representation of an embodiment of an amperometric analyte sensor comprising a plurality of layered elements including a dexamethasone-inhibiting membrane disposed as an outer layer and a dexamethasone-inhibiting membrane disposed within a layer.

[0021] Figure 4 A schematic diagram of various dexamethasone-inhibiting membrane formulations in tabular form is provided, showing PHEMA membranes with varying permeabilities. The top panel includes illustrative dexamethasone-inhibiting membrane compositions and their ratios. The bottom panel includes illustrative dexamethasone-inhibiting membrane compositions with varying permeability profiles.

[0022] Figure 5Data from a study of sensors with DRMs compared to control sensors that did not include a DRM are provided, with normalized iSig traces shown. The figure provides data from normalized iSig sensor readings from these two sensor embodiments in the presence of dexamethasone. The data shows that sensors including DRMs exhibited smaller fluctuations in iSig (nA) after exposure to DXAC; as well as improved stability (i.e., smaller changes in glucose response (day 2 vs. day 4)) after exposure to acetaminophen (AC) and DXAC. The data in the upper left graph shows that sensors including DRMs exhibited improved / faster break-in times.

[0023] Figure 6 Figure 1 shows a sensitivity analysis, which provides data (nA / mg / dl) for a sensitivity analysis study of sensors with DRMs made from different formulations compared to a control sensor that did not include the DRM. For example, as shown by the boxed data points on the right side of the figure, sensors designed to include poly(2-hydroxyethyl methacrylate) compositions containing 50% (w / v) to 80% (w / v) tetra(ethylene glycol) diacrylate in combination with 0% (w / v) to 10% (w / v) methacryloxyethyl phosphorylcholine (MPC) were more stable (showing less sensitivity change from day 2 to day 4) compared to the control sensor that did not include the DRM. DETAILED DESCRIPTION

[0024] Unless otherwise defined, all technical terms, symbols and other scientific terms used herein are intended to have the meanings commonly understood by those skilled in the art to which the present invention belongs. In some cases, for clarity and / or for ease of reference, the terms with commonly understood meanings are defined herein, and including these definitions herein should not necessarily be interpreted as representing that the meanings commonly understood with this area are substantially different. Many techniques and procedures described or quoted herein are well understood and are often adopted by those skilled in the art using conventional methods. Where appropriate, unless otherwise specified, the procedures relating to the use of commercially available test kits and reagents are generally carried out according to the schemes and / or parameters defined by the manufacturers. In addition, some texts from related art are reproduced herein to more clearly describe various embodiments of the present invention. A plurality of terms are defined below.

[0025] All publications mentioned herein are clearly incorporated herein by reference, to disclose and describe the method and / or material relevant to the cited publications. The publications cited herein are cited for their disclosures before the date of submission of the present application. Any content herein should not be construed as admitting that the inventor has no right to rely on an earlier priority date of the present invention or on an earlier date than this publication. In addition, the actual publication date may be different from that shown, and needs independent verification.

[0026] It must be noted that, as used herein and in the appended claims, the singular forms "a," "an," and "the" include plural referents unless the context clearly indicates otherwise. Thus, for example, reference to "an oxidoreductase" includes a plurality of such oxidoreductases and equivalents thereof known to those skilled in the art, and so forth. All numbers recited in the specification and associated claims, which refer to values ​​that can be characterized by numerical values ​​other than integers (e.g., the concentration of a compound in a solution), are understood to be modified by the term "about."

[0027] The term "oxidoreductase" is used according to its art-recognized meaning, i.e., an enzyme that catalyzes the transfer of electrons from one molecule (reductant, also known as hydrogen or electron donor) to another molecule (oxidant, also known as hydrogen or electron acceptor). Typical oxidoreductases include glucose oxidase and lactate oxidase. The terms "carrier polypeptide" or "carrier protein" are used according to their art-recognized meaning and include additives to maintain the stability of the polypeptide, e.g., the ability of the oxidoreductase polypeptide to maintain certain qualitative characteristics of the composition comprising the polypeptide, such as physical and chemical properties (e.g., the ability to oxidize glucose), over a period of time. A typical carrier protein commonly used in the art is albumin.

[0028] The term "analyte" as used herein is a broad term and is used in its ordinary sense, including but not limited to referring to a substance or chemical component in a fluid that can be analyzed, such as a biological fluid (e.g., blood, interstitial fluid, cerebrospinal fluid, lymph or urine). Analytes can include naturally occurring substances, artificial substances, metabolites and / or reaction products. In some embodiments, the analyte for measurement by the sensing region, device and method is glucose. However, other analytes are also contemplated, including but not limited to lactic acid. In certain embodiments, salts, sugars, proteins, fats, vitamins and hormones naturally occurring in blood or interstitial fluid can constitute analytes. Analytes can be naturally present in biological fluids or endogenous; for example, metabolites, hormones, antigens, antibodies, etc. Alternatively, analytes can be introduced into the human body or exogenous, for example, contrast agents for imaging, radioisotopes, chemical reagents, fluorocarbon-based synthetic blood or drugs or pharmaceutical compositions, including but not limited to insulin. Metabolites of drugs and pharmaceutical compositions are also considered analytes.

[0029] As used herein, the term "sensor" is a broad term and is used in its ordinary sense to include, but is not limited to, one or more portions of an analyte monitoring device that detects an analyte. In one embodiment, the sensor comprises an electrochemical cell having a working electrode, a reference electrode, and optionally a counter electrode that passes through the sensor body and is fixed within the sensor body, thereby forming an electrochemically reactive surface at one location on the body, forming an electrical connection at another location on the body, and forming a membrane system that adheres to the body and covers the electrochemically reactive surface. During typical operation of the sensor, a biological sample (e.g., blood or interstitial fluid) or a portion thereof contacts (directly or after passing through one or more membranes or domains) an enzyme (e.g., glucose oxidase); a reaction of the biological sample (or portion thereof) results in the formation of a reaction product that allows the level of an analyte in the biological sample to be determined.

[0030] As used herein, the terms "electrochemical reaction surface" and "electroactive surface" are broad terms and are used in their ordinary sense, including but not limited to the surface of an electrode where an electrochemical reaction occurs. In one example, a working electrode (e.g., a working electrode composed of platinum black) measures hydrogen peroxide produced by an enzyme-catalyzed reaction of the analyte being detected by generating an electric current. For example, the detection of glucose analyte using glucose oxidase produces H2O2 as a byproduct. H2O2 reacts with the surface of the working electrode to produce two protons (2H + ), two electrons (2e - ) and an oxygen molecule (O2), thereby generating the current that is detected. In the case of the counter electrode, the reducible species such as O2 is reduced on the electrode surface to balance the current generated by the working electrode.

[0031] As used herein, the term "sensing region" is a broad term and is used in its ordinary sense, including but not limited to the region of a monitoring device responsible for detecting a specific analyte. In an illustrative embodiment, the sensing region may include a non-conductive body, a working electrode, a reference electrode, and a counter electrode, the counter electrode passing through the body and fixed within the body, thereby forming an electrochemically reactive surface on the body, forming an electronic connection device at another location of the body, and forming one or more layers covering the electrochemically reactive surface.

[0032] As discussed in detail below, embodiments of the present invention relate to the use of electrochemical sensors that exhibit a series of novel elements, including the selection of dexamethasone inhibitory membranes to have a unique set of technically desirable material properties. The electrochemical sensors of the present invention are designed to be implanted to measure the concentration of an analyte of interest (e.g., glucose) or to indicate the concentration of an analyte in a fluid or the concentration of a substance present. Typically, these sensors comprise reagents selected to suppress or improve immune or inflammatory responses, such as dexamethasone. In some embodiments, the sensor is a continuous device, such as a subcutaneous, transcutaneous, or intravascular device. In some embodiments, the device can analyze multiple intermittent blood samples. The sensor embodiments disclosed herein can use any known method, including invasive, minimally invasive, and non-invasive sensing technologies, to provide an output signal indicating the concentration of an analyte of interest. Typically, the type of sensor is a product or reactant of an enzymatic reaction between an analyte and an enzyme in the presence of oxygen, as a measurement of an analyte in vivo or in vitro. Such sensors typically include a membrane surrounding the enzyme through which the analyte migrates. The product is then measured using an electrochemical method, and the output of the electrode system therefore serves as a measure of the analyte. In some embodiments, the sensor can use amperometric titration techniques, coulometric titration techniques, conductometric titration techniques, and / or potentiometric titration techniques to measure the analyte.

[0033] The embodiments of the invention disclosed herein provide sensors of the type used, for example, for subcutaneous or transcutaneous monitoring of blood glucose levels in diabetic patients. A variety of implantable electrochemical biosensors have been developed for the treatment of diabetes and other life-threatening diseases. Many existing sensor designs use some form of immobilized enzyme to achieve their biospecificity. The embodiments of the invention described herein can be adapted and implemented with a variety of known electrochemical sensors, including, for example, U.S. Patent Application No. 20050115832, U.S. Patent Nos. 6,001,067, 6,702,857, 6,212,416, 6,119,028, 6,400,974, 6,595,919, 6,141,573, 6,122,536, 6,512 ,939, 5,605,152, 4,431,004, 4,703,756, 6,514,718, 5,985,129, 5,390,691, 5,391,250, 5,482,473, 5,299,571, 5,568,806, 5,494,562, 6,120,676, 6,542,765, and PCT International Publication WO 01 / 58348, WO 04 / 021877, WO 03 / 034902, WO 03 / 035117, WO 03 / 035891, WO 03 / 023388, WO 03 / 022128, WO 03 / 022352, WO 03 / 023708, WO 03 / 036255, WO 03 / 036310, WO 08 / 042625 and WO 03 / 074107, and European Patent Application No. EP 1 153 571, the contents of each of which are incorporated herein by reference.

[0034] As discussed in detail below, embodiments of the present invention disclosed herein provide sensor elements with enhanced material properties and / or architecture configurations and are configured to include sensor systems (e.g., including sensors and sensor systems such as associated electronic components such as monitors, processors). The disclosure further provides methods for manufacturing and using such sensors and / or architecture configurations. Although some embodiments of the present invention relate to ketones (see, for example, U.S. patent application serial number 17 / 501, No. 292, the content of which is incorporated by reference), glucose (see, for example, U.S. patent application serial number 15 / 140,129, the content of which is incorporated by reference), various elements disclosed herein (e.g., dexamethasone inhibition membrane) may be applicable to any sensor in various sensors known in the art. Analyte sensor elements, architecture, and methods for manufacturing and using these elements disclosed herein can be used to establish various layered sensor structures. Such sensors of the present invention exhibit surprising flexibility and multifunctionality, allow various sensor configurations to be designed to inspect the characteristics of various analyte species.

[0035] Specific aspects of embodiments of the present invention are discussed in detail in the following sections.

[0036] I. Typical Elements, Configurations, and Analyte Sensor Embodiments of the Invention

[0037] It is known in the art that various sensors and sensor elements for detecting and / or measuring current-type sensors for biological analytes such as glucose are included. Many glucose sensors are based on oxygen (Clark-type) current-type transducers (see, for example, Yang et al., Electroanalysis 1997, 9, No. 16: 1252-1256; Clark et al., Ann.NY Acad.Sci., 1962, 102, 29; Updike et al., Nature 1967, 214, 986; and Wilkins et al., Med.Engin.Physics, 1996, 18, 273.3-51). Many in vivo glucose sensors utilize current-type sensors because such transducers are relatively easy to manufacture and can be easily miniaturized using conventional techniques. However, the problem associated with the use of implantable current-type sensors including dexamethasone is signal interference. As discussed in detail below, these problems are solved by novel membranes disclosed herein, which regulate the transport properties of dexamethasone that can generate signals in current-type sensors. Therefore, these membranes can be used with any of a variety of amperometric sensors for use in sensors for analytes susceptible to interference by dexamethasone.

[0038] Amperometric sensors typically include multiple layered elements, including, for example, a substrate layer with electrodes, an enzyme layer, and an analyte diffusion control (e.g., glucose limiting) membrane. In some sensor embodiments, an adhesion promoter layer is added to promote close attachment of the various layers, such as the diffusion control membrane and the enzyme layer. Figure 2A One such sensor embodiment is shown in FIG. The embodiments of the invention disclosed herein may further include a dexamethasone inhibitory membrane (DRM) designed to inhibit and / or prevent dexamethasone from approaching the sensor electrodes and confounding the measurement of the signal generated by the analyte to be measured. Figure 4 An illustrative embodiment of a sensor having a dexamethasone-inhibiting membrane is shown in .

[0039] The dexamethasone inhibitory membrane compositions and associated methods disclosed herein significantly improve sensor reliability. Embodiments of the dexamethasone inhibitory membrane disclosed herein include materials configured to exhibit a range of material properties that can be used in various contexts and, for example, overcome many technical problems observed in sensors such as electrochemical glucose sensors that are implanted in the body and utilize a chemical reaction between glucose and glucose oxidase to generate a measurable signal. Specifically, various embodiments of dexamethasone inhibitory membranes (DRMs) are provided that slow the diffusion of interfering dexamethasone molecules. Embodiments of the present invention include membrane compositions that can be used, for example, in amperometric sensors (e.g., glucose sensors used by individuals with diabetes) to suppress false signals caused by dexamethasone.

[0040] In addition to the material properties described above, in various embodiments, the molecular structure of the dexamethasone-inhibiting membrane material is free of electrochemically reactive moieties that, for example, could generate spurious signals (directly or indirectly) at the electrode surface. Furthermore, for sensors comprising multiple layered elements, in certain embodiments, the material of the dexamethasone-inhibiting layer exhibits adhesive properties, allowing it to adhere to rough surfaces, such as platinum black compositions, which comprise some electrode surfaces, while also allowing it to adhere to various other substrates, such as adjacent layers comprising bioactive molecules, such as glucose oxidase (i.e., exhibiting adhesive properties that inhibit delamination of the sensor layers).

[0041] Furthermore, sensors comprising multiple layers designed to measure analytes in aqueous environments (e.g., sensors implanted in vivo) typically require wetting of the layers before and during measurement of accurate analyte readings. Because the properties of a material may affect its rate of hydration, in various embodiments, the material properties of the dexamethasone-inhibiting membrane used in an aqueous environment promote sensor wetting ("running-in"), for example, to minimize the time period between the introduction of the sensor into an aqueous environment and the ability of the sensor to provide an accurate signal corresponding to the analyte concentration in that environment.

[0042] In the context of electrochemical glucose sensors that utilize a chemical reaction between glucose and glucose oxidase to generate a measurable signal, various embodiments of the dexamethasone inhibitory membrane do not exacerbate (and in some cases, actually reduce) what is known in the art as the "hypoxia problem." Specifically, because glucose oxidase-based sensors require both oxygen (O2) and glucose to generate a signal, the presence of an excess of oxygen relative to glucose is essential for the operation of glucose oxidase-based glucose sensors. However, because the oxygen concentration in subcutaneous tissue is much lower than the glucose concentration, oxygen may be the limiting reactant in the reaction between glucose, oxygen, and glucose oxidase in the sensor, a situation that compromises the sensor's ability to generate a signal that is strictly dependent on glucose concentration. In this case, because the properties of the DRM material may affect the rate at which compounds diffuse through the material to the site of the measurable chemical reaction, the material properties of the dexamethasone inhibitory membrane used in electrochemical glucose sensors that utilize a chemical reaction between glucose and glucose oxidase to generate a measurable signal should not, for example, favor the diffusion of glucose over the diffusion of oxygen in a manner that would create a hypoxia problem.

[0043] A. Typical sensor architecture found in embodiments of the present invention

[0044] Figure 2A The figure shows a cross-section of a typical sensor embodiment 100 of the present invention. This sensor embodiment is formed of multiple components, which are generally in the form of layers of various conductive and non-conductive components arranged on each other according to the art-recognized methods disclosed herein and / or the specific methods of the present invention. The components of the sensor are generally characterized as layers herein because, for example, it allows for easy characterization of the sensor structure shown in Figure 2. However, the skilled person will understand that in certain embodiments of the present invention, the sensor components are combined so that the multiple components form one or more heterogeneous layers. In this case, the skilled person will understand that in various embodiments of the present invention, the order of layering the components can be changed.

[0045] Figure 2AThe embodiment shown in may include a base layer 102 supporting the sensor 100 (e.g., disposed below the conductive layer 104). The base layer 102 may be made of a material such as a metal and / or ceramic and / or polymer substrate, which may be self-supporting or may be further supported by another material known in the art. Embodiments of the present invention include a conductive layer 104 disposed on and / or in combination with the base layer 102. Typically, the conductive layer 104 includes one or more electrodes. The operating sensor 100 typically includes a plurality of electrodes, such as a working electrode, a counter electrode, and a reference electrode. Other embodiments may also include a plurality of working electrodes and / or counter electrodes and / or reference electrodes and / or one or more electrodes that perform multiple functions, such as an electrode that serves as both a reference electrode and a counter electrode.

[0046] As discussed in detail below, many known techniques and materials may be used to create the base layer 102 and / or the conductive layer 104. In certain embodiments of the present invention, the circuitry of the sensor is defined by etching the conductive layer 104 into a desired conductive path pattern. A typical circuit for the sensor 100 includes two or more adjacent conductive paths having an area at a proximal end to form a contact pad and an area at a distal end to form a sensor electrode. An electrically insulating covering layer 106, such as a polymer coating, may be provided over portions of the sensor 100. Various sensor stacks are contemplated. For example, in Figure 2A In the embodiment of the present invention, an insulating layer may be disposed above layer 104 (the conductive layer). Acceptable polymer coatings for the insulating protective cover layer 106 may include, but are not limited to, non-toxic biocompatible polymers such as silicone compounds, polyimides, biocompatible solder resists, epoxy-acrylate copolymers, and the like. In the sensor of the present invention, one or more exposed areas or holes 108 may be formed through the cover layer 106 to open the conductive layer 104 to the external environment and, for example, allow an analyte (such as glucose) to pass through the sensor layer and be sensed by the sensing element. The holes 108 may be formed by a variety of techniques, including laser ablation, masking, chemical milling or etching, or photolithographic development. In certain embodiments of the present invention, a second photoresist may also be applied to the protective layer 106 during manufacturing to define areas where the protective layer is to be removed to form the one or more holes 108. The exposed electrodes and / or contact pads may also undergo secondary processing (e.g., through the holes 108) such as additional electroplating processes to prepare the surface and / or enhance the conductive areas.

[0047] exist Figure 2A In the sensor configuration shown in , the analyte sensing layer 110 (which is typically a sensor chemistry layer, meaning that the material in this layer undergoes a chemical reaction to produce a signal that can be sensed by the conductive layer) is disposed on one or more of the exposed electrodes of the conductive layer 104. Figure 2BIn the sensor configuration shown in , the interference suppression membrane 120 is arranged on one or more exposed electrodes in the exposed electrodes of the conductive layer 104, wherein the analyte sensing layer 110 is then arranged on this interference suppression membrane 120. Typically, the analyte sensing layer 110 is an enzyme layer. Most typically, the analyte sensing layer 110 includes an enzyme capable of producing and / or utilizing oxygen and / or hydrogen peroxide, such as glucose oxidase. Optionally, the enzyme in the analyte sensing layer is combined with a second carrier protein (such as human serum albumin, bovine serum albumin, etc.). In an illustrative embodiment, the oxidoreductase (such as glucose oxidase) in the analyte sensing layer 110 reacts with glucose to produce hydrogen peroxide, which is a compound that regulates the current at the electrode afterwards. Since this regulation of current depends on the concentration of hydrogen peroxide, and the concentration of hydrogen peroxide is related to the concentration of glucose, the concentration of glucose can be determined by monitoring this regulation of current. In a specific embodiment of the invention, hydrogen peroxide is oxidized at a working electrode (also referred to herein as an anode working electrode) as an anode, and the current generated is directly proportional to the concentration of hydrogen peroxide. This modulation of the current caused by changes in hydrogen peroxide concentration can be monitored by any of a variety of sensor detector devices, such as a universal sensor amperometric biosensor detector or one of various other similar devices known in the art, such as those manufactured by Medtronic TM MiniMed TM Glucose monitoring devices produced by.

[0048] In an embodiment of the present invention, the analyte sensing layer 110 may be applied over a portion of the conductive layer or over the entire area of ​​the conductive layer. Typically, the analyte sensing layer 110 is disposed on a working electrode, which may be an anode or a cathode. Optionally, the analyte sensing layer 110 is also disposed on a counter electrode and / or a reference electrode. Although the thickness of the analyte sensing layer 110 may be up to about 1000 microns (μm), the analyte sensing layer may be relatively thin compared to the thickness found in sensors previously described in the art, and the thickness is typically, for example, less than 1 micron, 0.5 micron, 0.25 micron, or 0.1 micron. In other cases, the thickness of the analyte sensing layer 110 is between 3.5 microns and 10 microns. As discussed in detail below, some methods for producing a thin analyte sensing layer 110 include: brushing the layer onto a substrate (e.g., the reactive surface of a platinum black electrode), as well as spin coating, slit coating, dip coating and drying, low shear spraying, inkjet printing, silk screen printing, etc.

[0049] Typically, the analyte sensing layer 110 is coated and / or arranged near one or more additional layers. Optionally, one or more additional layers include a protein layer 116 arranged on the analyte sensing layer 110. Typically, the protein layer 116 includes proteins, such as human serum albumin, bovine serum albumin, etc. Typically, the protein layer 116 includes human serum albumin. In some embodiments of the present invention, the additional layer includes an analyte regulating layer 112, which is arranged above the analyte sensing layer 110 to regulate the proximity of the analyte to the analyte sensing layer 110. For example, the analyte regulating membrane layer 112 may include a glucose limiting membrane, which regulates the amount of glucose contacted with the enzyme (such as glucose oxidase) present in the analyte sensing layer. Such glucose limiting membranes can be made of a variety of materials known to be suitable for such purposes, for example, silicone compounds such as polydimethylsiloxane, polyurethane, polyurea acetate cellulose, NAFION, polyester sulfonic acid (for example, Kodak AQ), hydrogels or any other suitable hydrophilic membranes known to those skilled in the art.

[0050] As shown in Figure 2, in typical embodiments of the present invention, an adhesion promoter layer 114 is provided between the analyte modulating layer 112 and the analyte sensing layer 110 to promote their contact and / or adhesion. In specific embodiments of the present invention, as shown in Figure 2, an adhesion promoter layer 114 is provided between the analyte modulating layer 112 and the protein layer 116 to promote their contact and / or adhesion. The adhesion promoter layer 114 can be made of any of a variety of materials known in the art to promote bonding between such layers. Typically, the adhesion promoter layer 114 includes a silane compound. In alternative embodiments, the protein or similar molecules in the analyte sensing layer 110 can be fully cross-linked or otherwise prepared to allow the analyte modulating membrane layer 112 to be provided in direct contact with the analyte sensing layer 110 in the absence of the adhesion promoter layer 114.

[0051] Discussed below are embodiments of typical components used to make the sensors disclosed herein.

[0052] B. Typical Analyte Sensor Components Used in Embodiments of the Invention

[0053] The following disclosure provides examples of typical elements / ingredients used in sensor embodiments of the present invention. Although these elements can be described as discrete units (e.g., layers), it will be understood by those skilled in the art that sensors can be designed to contain elements having some or all of the combinations of material properties and / or functions of the elements / ingredients discussed below (e.g., elements serving as supporting substrate components and / or conductive components and / or for both analyte sensing components and further serving as a matrix for electrodes in the sensor). It will be understood by those skilled in the art that these thin film analyte sensors can be applicable to many sensor systems, such as the sensor systems described herein.

[0054] Base ingredients

[0055] The sensors of the present invention generally include a substrate component (see, e.g. Figure 2A 102 in the device). The term "base component" is used herein according to art-recognized terminology and refers to a component in the device that generally provides a support matrix for multiple components stacked on top of each other and including the functional sensor. In one form, the base component comprises a thin film sheet of insulating (e.g., electrically insulating and / or impermeable) material. This base component can be made of a variety of materials with desired qualities (such as dielectric properties, impermeability, and airtightness). Some materials include metal and / or ceramic and / or polymer substrates, etc.

[0056] The base component may be self-supporting or may be further supported by another material known in the art. Figure 2A In one embodiment of the sensor configuration shown in , the substrate component 102 comprises a ceramic. Alternatively, the substrate component comprises a polymer material, such as, polyimide. In an illustrative embodiment, the ceramic substrate comprises a composition that is primarily Al2O3 (e.g., 96%). The use of alumina as an insulating substrate component for use with implantable devices is disclosed in U.S. Patents 4,940,858, 4,678,868, and 6,472,122, which are incorporated herein by reference. The substrate component of the present invention may further comprise other elements known in the art, such as sealed through-holes (see, for example, WO03 / 023388). Depending on the specific sensor design, the substrate component may be a relatively thick component (e.g., thicker than 50 microns, 100 microns, 200 microns, 300 microns, 400 microns, 500 microns, or 1000 microns). Alternatively, non-conductive ceramics such as alumina, for example, less than about 30 microns, may be utilized in thin components.

[0057] Conductive components

[0058] The electrochemical sensors of the present invention generally include a conductive component including at least one electrode disposed on a substrate component, the at least one electrode being used to measure the analyte to be determined or its byproducts (e.g., oxygen and / or hydrogen peroxide) (see, e.g., Figure 2A Element 104 in). The term "conductive component" is used herein according to terms generally recognized in the art and refers to a conductive sensor element, such as an electrode, capable of measuring a detectable signal and conducting the signal to a detection device. An illustrative example of a conductive component is a conductive component that can measure an increase or decrease in current in response to exposure to a stimulus (such as a concentration change of an analyte or its byproducts) compared to a reference electrode that does not experience a concentration change of an analyte (a co-reactant (e.g., oxygen) used when the analyte interacts with a composition (e.g., enzyme glucose oxidase) present in the analyte sensing component 110, or a reaction product (e.g., hydrogen peroxide) of this interaction). Illustrative examples of such elements include electrodes that can generate a variable detectable signal in the presence of a variable concentration of molecules (such as hydrogen peroxide or oxygen). Typically, one of these electrodes in the conductive component is a working electrode, which can be made of a non-corrosive metal or carbon. The carbon working electrode can be glassy or graphitic and can be made of a solid or paste. The metal working electrode can be made of a platinum group metal including palladium or gold, or made of a non-corrosive metal conductive oxide, such as ruthenium dioxide. Alternatively, the electrode can include a silver / silver chloride electrode composition. The working electrode can be a wire or a thin conductive film applied to a substrate, for example, by coating or printing. Typically, only a portion of the surface of the metal or carbon conductor is in electrolytic contact with the solution containing the analyte. This portion is referred to as the working surface of the electrode. The remaining surface of the electrode is typically isolated from the solution by an electrically insulating cover component 106. Examples of useful materials for producing this protective cover component 106 include polymers, such as polyimides, polytetrafluoroethylene, polyhexafluoropropylene, and siloxanes such as polysiloxanes.

[0059] In addition to the working electrode, the analyte sensor of the present invention typically also includes a reference electrode or a combined reference electrode and counter electrode (also called a quasi-reference electrode or counter electrode / reference electrode). If the sensor does not have a counter electrode / reference electrode, it may include a separate counter electrode, which may be made of the same or different material as the working electrode. Typical sensors of the present invention have one or more working electrodes and one or more counter electrodes, reference electrodes and / or counter electrode / reference electrodes. One embodiment of the sensor of the present invention has two, three or four or more working electrodes. These working electrodes in the sensor can be connected as a whole or kept separate.

[0060] Typically, for in vivo use, embodiments of the present invention are implanted subcutaneously in the skin of a mammal to be in direct contact with the mammal's body fluids (such as blood). Alternatively, the sensor can be implanted in other areas of the mammal's body, such as within the peritoneum or subcutaneous space. When multiple working electrodes are used, the multiple working electrodes can be implanted together or at different locations in the body. Counter electrodes, reference electrodes, and / or counter / reference electrodes can also be implanted near one or more working electrodes or at other locations in the mammal's body. Embodiments of the present invention include sensors comprising electrodes composed of nanostructured materials. As used herein, "nanostructured material" is an object manufactured to have at least one dimension less than 100 nm. Examples include, but are not limited to, single-walled nanotubes, double-walled nanotubes, multi-walled nanotubes, nanotube bundles, fullerenes, cocoons, nanowires, nanofibers, onions, and the like.

[0061] Dexamethasone inhibitory component

[0062] The electrochemical sensors of the present invention typically include a dexamethasone inhibitory component disposed between the electrode surface and the environment to be measured. Embodiments of the present invention described herein include a dexamethasone acetate inhibitory membrane (DRM) made of a selected material to prevent dexamethasone from penetrating into the sensing element of the current-type sensor. In illustrative embodiments, the membrane can be composed of various poly(2-hydroxyethyl methacrylate) ("poly-Hema") compositions in various forms and can be incorporated into the sensor at various locations. The DRM may or may not be composed of pre-polymerized poly-HEMA. Embodiments of the present invention customize the thickness and permeability of the DRM layer so that it does not interfere with (or limit) the analyte diffusion rate of the sensor while preventing dexamethasone from affecting the sensor signal.

[0063] Interference suppression component

[0064] The electrochemical sensor of the present invention may include an interference suppression component arranged between the electrode surface and the environment to be measured. Specifically, some sensor embodiments rely on the oxidation and / or reduction of hydrogen peroxide produced by the enzymatic reaction on the surface of the working electrode under a constant applied potential. Because the current-type detection based on the direct oxidation of hydrogen peroxide requires a relatively high oxidation potential, the sensor using this detection scheme may experience interference from oxidizable species (such as ascorbic acid, uric acid and acetaminophen) present in biological fluids. In this case, the term "interference suppression component" is used herein according to terms generally recognized in the art, and refers to a coating or film in the sensor that is used to suppress false signals generated by such oxidizable species that interfere with the detection of the signal generated by the analyte to be sensed. Some interference suppression components work via size exclusion (e.g., by excluding interfering species of a specific size).

[0065] Further disclosed herein are compositions having undesirable clustering of material properties that may render the additional compositions ideal for use as interference rejection membranes in certain amperometric glucose sensors, and methods for making and using the same.

[0066] Analyte sensing component

[0067] The electrochemical sensor of the present invention includes an analyte sensing component disposed on an electrode of the sensor (see, e.g., Figure 2A 110 in). The term "analyte sensing component" is used herein according to a specialized term generally recognized in the art, and refers to a component comprising an analyte or a material that can identify the presence of which is to be detected by an analyte sensor device or react therewith. Typically, this material in the analyte sensing component typically produces a detectable signal via the electrode of a conductive component after interacting with the analyte to be sensed. In this regard, the electrodes of the analyte sensing component and the conductive component work in a combined manner to produce an electrical signal read by a device associated with the analyte sensor. Typically, the analyte sensing component includes an oxidoreductase (e.g., glucose oxidase) that can react with a molecule and / or produce a molecule, and the concentration change of the molecule can be measured by measuring the current change at the electrode of the conductive component (e.g., oxygen and / or hydrogen peroxide). The enzyme that can produce a molecule (such as hydrogen peroxide) can be arranged on an electrode according to many methods known in the art. The analyte sensing component can coat all or part of the different electrodes of the sensor. In this case, the analyte sensing component can coat the electrodes to the same extent. Alternatively, the analyte sensing component may coat different electrodes to different extents, eg, the working electrode may have a coated surface that is greater than the coated surface of the counter and / or reference electrodes.

[0068] Typical sensor embodiments of this element of the invention utilize an enzyme (e.g., glucose oxidase) that has been combined with a second protein (e.g., albumin) in a fixed ratio (e.g., an enzyme typically optimized for glucose oxidase stability properties) and then applied to the surface of an electrode to form a thin enzyme component. In typical embodiments, the analyte sensing component includes a mixture of GOx and HSA. In typical embodiments of the analyte sensing component with GOx, the GOx reacts with glucose present in the sensing environment (e.g., the body of a mammal) and detects the presence of glucose in the body according to the present invention. Figure 1 The reaction shown in produces hydrogen peroxide, wherein the hydrogen peroxide so produced is detected at the working electrode in the conductive component at the anode.

[0069] As described above, the enzyme and the second protein (e.g., albumin) are typically treated to form a cross-linked matrix (e.g., by adding a cross-linking agent to the protein mixture). As is known in the art, cross-linking conditions can be manipulated to adjust factors such as the enzyme's ability to maintain biological activity, its mechanical and / or operational stability. Illustrative cross-linking procedures are described in U.S. Patent Application Serial No. 10 / 335,506 and PCT Publication WO 03 / 035891, which are incorporated herein by reference. For example, an amine cross-linking agent (such as, but not limited to, glutaraldehyde) can be added to the protein mixture.

[0070] Protein content

[0071] The electrochemical sensors of the present invention optionally include a protein component disposed between the analyte sensing component and the analyte modulating component (see, e.g., Figure 2A Element 116 in). The term "protein component" is used herein according to art-recognized terminology and refers to a component containing a carrier protein, etc., which is selected to be compatible with the analyte sensing component and / or the analyte modulating component. In typical embodiments, the protein component includes albumin, such as human serum albumin. The HSA concentration may vary between about 0.5%-30% (w / v). Typically, the HSA concentration is about 1 w / v-10% w / v, and most typically about 5% w / v. In alternative embodiments of the present invention, collagen or BSA or other structural proteins used in these cases may be used instead of HSA or in addition to HSA. This component is typically cross-linked to the analyte sensing component according to art-recognized protocols.

[0072] Adhesion promoting ingredients

[0073] The electrochemical sensors of the present invention may include one or more adhesion promoting (AP) components (see e.g. Figure 2A 114 in). The term "adhesion promoting component" is used herein according to a specialized term generally recognized in the art and refers to a component comprising a material selected to promote adhesion between adjacent components in a sensor. Typically, the adhesion promoting component is disposed between the analyte sensing component and the analyte modulating component. Typically, the adhesion promoting component is disposed between an optional protein component and an analyte modulating component. The adhesion promoter component can be made of any of a variety of materials known in the art to promote bonding between these components and can be applied by any of a variety of methods known in the art. The adhesion promoter component typically includes a silane compound, such as γ-aminopropyltrimethoxysilane.

[0074] The use of silane coupling agents, particularly silane coupling agents of the formula R'Si(OR)3, where R' is typically an aliphatic group with a terminal amine and R is a lower alkyl group, to promote adhesion is known in the art (see, e.g., U.S. Patent No. 5,212,050, which is incorporated herein by reference). For example, silanes such as gamma-aminopropyltriethoxysilane and glutaraldehyde are used in a stepwise process to bind bovine serum albumin (BSA) and glucose oxidase (GO). X Chemically modified electrodes in which the electrodes are attached to and co-crosslinked with the electrode surface are known in the art (see, for example, Yao, T. Acta Analytical Chemica Sinica 1983, 148, 27-33).

[0075] In certain embodiments of the present invention, the adhesion promoting component further includes one or more compounds that can also be present in adjacent components for limiting the diffusion of analytes such as glucose through analyte modulation components, such as polydimethylsiloxane (PDMS) compounds. In illustrative embodiments, the formulation includes 0.5%-20% PDMS, typically 5%-15% PDMS, and most typically 10% PDMS. In certain embodiments of the present invention, the adhesion promoting component is cross-linked within the layered sensor system and correspondingly includes a reagent selected to enable partial cross-linking of the proximal components such as the analyte modulation components. In illustrative embodiments of the present invention, the adhesion promoting component includes a reagent selected to enable partial cross-linking of proteins present in proximal components such as analyte sensing components and / or protein components and / or to enable partial cross-linking of siloxanes present in compounds provided in proximal layers such as analyte modulation layers.

[0076] Analyte Modulating Components

[0077] The electrochemical sensor of the present invention includes an analyte modulating component disposed on the sensor (see, e.g., Figure 2A 112 in). The term "analyte modulating component" is used herein according to a specialized term generally recognized in the art, and refers to a component that typically forms a film on the sensor that operates to regulate the diffusion of one or more analytes (such as glucose) through the composition. In certain embodiments of the present invention, the analyte modulating component is an analyte limiting membrane (e.g., a glucose limiting membrane) that operates to prevent or limit the diffusion of one or more analytes (such as glucose) through the composition. In other embodiments of the present invention, the analyte modulating component is used to promote the diffusion of one or more analytes through the composition. Optionally, such analyte modulating components can be formed to prevent or limit the diffusion of one type of molecule (e.g., glucose) through the composition, while allowing or even promoting other types of molecules (e.g., O2) to diffuse through the composition.

[0078] About glucose sensor, in known enzyme electrode, glucose and oxygen from blood and some interfering substances (such as ascorbic acid and uric acid) diffuse through the primary membrane of sensor.When glucose, oxygen and interfering substances arrive analyte sensing component, enzyme (such as glucose oxidase) catalyzes glucose and converts it into hydrogen peroxide and gluconolactone.Hydrogen peroxide can diffuse back through analyte regulating component, or it can diffuse to electrode, at this electrode, hydrogen peroxide can react to form oxygen and proton to produce electric current that is directly proportional to glucose concentration.Sensor membrane assembly has multiple functions, including selectively allowing glucose to pass therethrough.In this case, illustrative analyte modulation component is semipermeable membrane, and this semipermeable membrane allows water, oxygen and at least one selective analyte to pass through and has water absorption capacity, and this membrane has water-soluble hydrophilic polymer.

[0079] Various illustrative analyte modulation compositions are known in the art and are described in, for example, U.S. Patents 6,319,540, 5,882,494, 5,786,439, 5,777,060, 5,771,868, and 5,391,250, the disclosure of each of which is incorporated herein by reference. The hydrogels described therein are particularly suitable for use with various implantable devices, for which it is advantageous to provide a surrounding water component. In some embodiments of the present invention, the analyte modulation composition comprises PDMS. In certain embodiments of the present invention, the analyte modulation component comprises a reagent selected to enable the crosslinking of the siloxane moieties present in the proximal component. In closely related embodiments of the present invention, the adhesion promoting component comprises a reagent selected to enable the crosslinking of the amine or carboxyl moieties of the proteins present in the proximal component.

[0080] Covering ingredients

[0081] The electrochemical sensors of the present invention include one or more covering components, which are typically electrically insulating protective components (see, e.g. Figure 2A Element 106 in). Typically, such covering components can be in the form of a coating, sheath or tube and are disposed on at least a portion of the analyte modulating component. Acceptable polymer coatings used as insulating protective covering components may include, but are not limited to, non-toxic biocompatible polymers such as silicone compounds, polyimides, biocompatible solder resists, epoxy acrylate copolymers, and the like. Further, these coatings may be photoimageable to facilitate photolithographic formation of holes through the conductive component. Typical covering components include spinning on silicone. As known in the art, this component can be a commercially available RTV (room temperature vulcanization) silicone composition. In this case, a typical chemical is polydimethylsiloxane (acetoxy).

[0082] C. Typical Analyte Sensor System Embodiments of the Invention

[0083] The sensor elements and embodiments of the sensors disclosed herein can be operably coupled to a variety of other system elements (e.g., structural elements such as puncture members, insertion kits, etc., and electronic components such as processors, monitors, drug infusion pumps, etc.) that are commonly used with analyte sensors, for example, making them suitable for use in various scenarios (e.g., implanted in mammals). One embodiment of the present invention includes a method for monitoring a user's physiological characteristics using an embodiment of the present invention, the embodiment including an input element that can receive a signal based on a sensed physiological characteristic value of the user from a sensor; and a processor for analyzing the received signal. In a typical embodiment of the present invention, the processor determines the dynamic behavior of the physiological characteristic value and provides an observable indicator based on the dynamic behavior of the physiological characteristic value so determined. In some embodiments, the physiological characteristic value is a measure of the user's blood glucose concentration. In other embodiments, the process of analyzing the received signal and determining the dynamic behavior includes repeatedly measuring the physiological characteristic value to obtain a series of physiological characteristic values, so as to, for example, incorporate comparative redundancy into the sensor device in a manner designed to provide confirmation information about sensor function, analyte concentration measurement, the presence of interference, etc.

[0084] Embodiments of the present invention include devices that display data from measurements of sensed physiological characteristics (e.g., blood glucose concentration) in a manner and form that is customized to allow the user of the device to easily monitor and (if necessary) adjust the physiological state of the characteristic (e.g., adjust blood glucose concentration via insulin administration). An illustrative embodiment of the present invention is a device that includes a sensor input that is capable of receiving a signal from a sensor that is based on a sensed physiological characteristic value of a user; a memory for storing multiple measurements of the sensed physiological characteristic value of the user from the received signal from the sensor; and a display for presenting text and / or graphical representations (e.g., text, line graphs, bar graphs, grid patterns, etc., or a combination thereof) of the multiple measurements of the sensed physiological characteristic value. Typically, the graphical representation displays real-time measurements of the sensed physiological characteristic value. Such devices can be used in a variety of situations, such as in combination with other medical devices. In some embodiments of the present invention, the device is used in combination with at least one other medical device (e.g., a glucose sensor).

[0085] The illustrative system embodiment consists of a glucose sensor, a transmitter and a pump receiver and a glucose meter. In this system, a radio signal from the transmitter can be periodically (e.g., every 5 minutes) sent to the pump receiver to provide real-time sensor glucose (SG) values. The value / graph is displayed on the monitor of the pump receiver so that the user can use his or her own insulin pump to self-monitor blood glucose and deliver insulin. Typically, the embodiments of the device disclosed herein communicate with a second medical device via a wired or wireless connection. Wireless communication may include, for example, receiving a radiation signal emitted, as occurs when transmitting signals via RF telemetry, infrared transmission, optical transmission, sound waves, and ultrasonic transmission. Optionally, the device is a component of a drug infusion pump (e.g., an insulin pump). Typically, in such devices, physiological characteristic values ​​include multiple measurement results of blood glucose.

[0086] D. Exemplary Embodiments of the Invention and Associated Features

[0087] In the individuality that uses analyte sensor in non-hospital environment (for example, diabetic patient uses glucose sensor to manage their disease) relatively long sensor initialization and / or start-up cycle also can be problematic, and this is due to the inconvenience to user and delays receiving both information relevant to user's health.In recent years, the use of glucose sensor, insulin infusion pump etc. in diabetes management has increased, and this is because for example research shows, when patient uses insulin in the mode of closely matching with the rise and fall of physiological insulin concentration in healthy individual, the morbidity and mortality problem associated with this chronic disease is significantly reduced.Therefore, medical staff instructs the patient with chronic disease such as diabetes to play an active role in its disease management, particularly closely monitors and regulates blood glucose level.In this case, because many diabetic patients do not have medical training, so they may abandon the optimal monitoring and regulation to blood glucose level due to the complexity associated with this type of management, for example, a two-hour start-up cycle, which may be inconvenient for the patient's active daily routine. For these reasons, sensors and sensor systems designed to include elements and / or configurations of elements that can reduce sensor initialization and / or startup times (e.g., the hydrophilic dexamethasone-inhibiting membranes disclosed herein) are highly desirable where such sensors are operated by diabetic patients without medical training because they facilitate convenient management of their disease by patients, an action shown to reduce the well-known morbidity and mortality problems observed in individuals with chronic diabetes.

[0088] Although the analyte sensors and sensor systems disclosed herein are generally designed to be implanted in a mammal, the invention disclosed herein is not limited to any particular environment, but can be used in a variety of contexts, for example, for analyzing most in vivo and in vitro fluid samples, including biological fluids such as interstitial fluid, whole blood, lymph, plasma, serum, saliva, urine, feces, sweat, mucus, tears, cerebrospinal fluid, nasal secretions, cervical or vaginal secretions, semen, pleural fluid, amniotic fluid, peritoneal fluid, middle ear effusion, joint fluid, gastric fluid, etc. In addition, solid or dried samples can be dissolved in an appropriate solvent to provide a liquid mixture suitable for analysis.

[0089] The invention disclosed herein has many embodiments. One illustrative embodiment of the invention is an analyte sensor device comprising: an elongated (i.e., length significantly greater than width) substrate layer; a conductive layer disposed on the substrate layer and comprising a reference electrode, a working electrode, and a counter electrode; a dexamethasone inhibitory membrane disposed on the conductive layer; an analyte sensing layer disposed on the dexamethasone inhibitory membrane; an analyte modulating layer disposed on the analyte sensing layer, wherein the analyte modulating layer comprises a composition that modulates diffusion of an analyte through the analyte modulating layer; and a covering layer disposed on the analyte sensor device, wherein the covering layer comprises a pore positioned on the covering layer to facilitate proximity of the analyte to and diffusion through the analyte modulating layer; and proximity of the analyte sensing layer. Typical embodiments of the invention are composed of biocompatible materials and / or have structural features designed for implantation in a mammal. Method embodiments of the invention include methods of making and using the sensor embodiments disclosed herein. Certain embodiments of the present invention include methods of using specific sensor elements and / or specific clusters of sensor elements to produce and / or facilitate one or more functions of the sensor embodiments disclosed herein.

[0090] As disclosed herein, those skilled in the art will understand that a conductive layer disposed on a substrate layer and comprising a working electrode, a counter electrode, and a reference electrode includes embodiments in which the conductive layer is disposed on at least a portion of the substrate layer and does not necessarily completely cover the substrate layer. Those skilled in the art will understand that this refers to other layers within the sensor, such as an analyte sensing layer disposed on the conductive layer, encompassing sensor embodiments in which the analyte sensing layer is disposed on at least a portion of the conductive layer; and an analyte modulating layer disposed on the analyte sensing layer, encompassing an analyte modulating layer disposed on at least a portion of the analyte sensing layer, and the like. Optionally, the electrodes may be disposed on a single surface or side of the sensor structure. Alternatively, the electrodes may be disposed on multiple surfaces or sides of the sensor structure (and may be connected to the surface on which the electrodes are disposed, for example, via vias through the sensor material). In certain embodiments of the present invention, the reactive surfaces of the electrodes have different relative areas / sizes, such as a 1× reference electrode, a 2.6× working electrode, and a 3.6× counter electrode.

[0091] In certain embodiments of the present invention, elements of the device, such as electrodes or holes, are designed to have specific configurations and / or be made of specific materials and / or be positioned relative to other elements in order to facilitate the function of the sensor. For example, without being bound by a specific theory or mechanism of action, it appears that sensor embodiments (e.g., simple three-electrode embodiments) may be more susceptible to changes in the local environment around a single electrode. For example, bubbles at or near the top of a reference electrode or another electrode, and / or stagnant or semi-stagnant fluid pools at or near the top of a reference electrode or another electrode may therefore impair sensor performance. In this case, a distributed electrode configuration appears to be advantageous because the distribution of electrode areas allows the sensor to compensate for signal losses in small local areas (e.g., situations that may occur due to lack of hydration, fluid stagnation, the patient's immune response, etc.).

[0092] A typical analyte sensor device embodiment includes a plurality of working electrodes, a counter electrode, and a reference electrode. Optionally, the plurality of working electrodes, the counter electrode, and the reference electrode are grouped together as a unit and are positionally distributed on the conductive layer in a repeating unit pattern. Alternatively, the plurality of working electrodes, the counter electrode, and the reference electrode are grouped together and are positionally distributed on the conductive layer in a non-repeating unit pattern. In certain embodiments of the present invention, the elongated base layer is made of a material that allows the sensor to twist and bend when implanted in the body; and the electrodes are grouped in a configuration that promotes in vivo fluid to approach at least one working electrode as the sensor device twists and bends when implanted in the body. In some embodiments, the electrodes are grouped in a configuration that allows the sensor to continue to function optimally if a portion of the sensor having one or more electrodes is removed from the in vivo environment and exposed to an in vitro environment.

[0093] Optionally, embodiments of the present invention include multiple working electrodes and / or counter electrodes and / or reference electrodes (e.g., to provide redundant sensing capabilities). Such embodiments of the present invention can be used in embodiments of the present invention that include a processor (e.g., a processor connected to a program suitable for a signal subtraction / elimination process) that is designed to exclude background signals in the body, for example, by comparing the signal at a working electrode coated with GOx with the signal at a working electrode not coated with GOx (e.g., background detection is followed by a signal subtraction / elimination process to obtain a true signal). Certain of these embodiments of the present invention are particularly useful for sensing glucose at the upper and lower ends of the glucose signal curve. Similar embodiments of the present invention are used to exclude interference, for example, by comparing the signal at a working electrode coated with GOx with the signal at a working electrode not coated with GOx. Embodiments of the present invention may include a coating of a Prussian blue composition on an electrode, the location and amount of which is sufficient to adjust the potential of the electrode of the device. Related embodiments of the present invention include methods for adjusting the potential of an electrode of the disclosed sensor device (e.g., by using a Prussian blue composition). Prussian blue formulas are known in the art and include Fe4[Fe(CN6]3xH20, CI No. 77510 and KFe[Fe(Cn)6]xH20 id CI No. 77520.

[0094] In typical embodiments of the present invention, the sensor is operatively coupled to another element (e.g., an electronic component), such as an element designed to transmit and / or receive signals, a monitor, a pump, a processor, and the like. For example, in some embodiments of the present invention, the sensor is operatively coupled to a sensor input capable of receiving a signal from the sensor based on a value of a physiological property sensed in a mammal; and a processor coupled to the sensor input, wherein the processor is capable of characterizing one or more signals received from the sensor. A variety of sensor configurations as disclosed herein can be used in such systems. Optionally, for example, the sensor includes three working electrodes, a counter electrode, and a reference electrode. In certain embodiments, at least one working electrode is coated with an analyte sensing layer comprising glucose oxidase (and optionally two are coated with GOx), and at least one working electrode is not coated with an analyte sensing layer comprising glucose oxidase. Such embodiments of the present invention can be used, for example, in sensor embodiments designed to eliminate background signals in vivo, for example by comparing the signal at a GOx-coated working electrode with the signal at a GOx-uncoated working electrode (e.g., background detection followed by a signal subtraction / elimination process to obtain the true signal).

[0095] In some embodiments of the sensor insertion kit device, the first and second (and / or third, etc.) electrochemical sensors include a working electrode, a counter electrode, and a reference electrode. Alternatively, a plurality of electrochemical sensors include a plurality of working electrodes, a counter electrode, and a reference electrode, for example, electrodes with a distributed configuration as disclosed in U.S. patent application serial number 11 / 633,254, the contents of which are incorporated by reference. In certain embodiments of the present invention, at least two of the plurality of sensors are designed to measure signals generated by the same physiological characteristic, such as blood glucose concentration. Embodiments of the present invention may include, for example, a plurality of electrochemical sensors having working electrodes coated with an oxidoreductase such as glucose oxidase, and used in methods designed to sample and compare glucose concentrations observed at a plurality of in vivo insertion sites. Alternatively, at least two of the plurality of sensors in the sensor device are designed to measure signals generated by different characteristics, for example, a first characteristic including a background signal or an interfering signal (e.g., "interference noise") unrelated to blood glucose and a second characteristic including blood glucose concentration. In an illustrative embodiment of the present invention, the first sensor is designed to measure glucose oxidase and includes one or more working electrodes coated with glucose oxidase, while the second comparison sensor is designed to measure a background signal or an interfering signal that is not related to blood glucose and does not have one or more working electrodes coated with glucose oxidase.

[0096] In certain embodiments of the present invention, sensor systems utilizing voltage pulsing and / or switching as disclosed herein are used in methods designed to overcome problems that can occur with implantable sensors and sensor systems due to lack of hydration (e.g., slow startup initialization times) and / or fluid stagnation by enhancing the ability of fluid to flow around the implanted component in a manner that inhibits the possibility of bubbles or stagnant pools of fluid forming and / or remaining on top of or near the electrodes in a manner that impairs sensor function. Furthermore, embodiments of the present invention utilizing voltage pulsing and / or switching can be combined with certain complementary elements disclosed herein to further overcome problems caused by lack of hydration, fluid stagnation, a patient's immune response, and the like (e.g., distributed electrode configurations, multi-electrode sensors, multi-sensor devices with multiple implant sites, and the like).

[0097] In some embodiments of the present invention, the processor can compare the first signal received from the working electrode in response to the first working potential with the second signal received from the working electrode in response to the second working potential, wherein the comparison of the first signal and the second signal at the first working potential and the second working potential can be used to identify the signal generated by the interfering compound. In one such embodiment of the present invention, a working electrode is coated with glucose oxidase, and the other is not, and the interfering compound is acetaminophen, ascorbic acid, bilirubin, cholesterol, creatinine, dopamine, ephedrine, ibuprofen, L-dopa, methyldopa, salicylate, tetracycline, tolbutamide, triglycerides or uric acid. Optionally, a pulse and / or variable (e.g., switched) voltage is used to obtain a signal from the working electrode. Typically, at least one voltage is 280 millivolts, 535 millivolts or 635 millivolts. Related embodiments of the present invention include methods for identifying and / or characterizing one or more signals generated by the interfering compounds in various sensor embodiments of the present invention (e.g., by comparing the signal from the electrode coated with the analyte sensing compound with the signal of the comparison electrode not coated with the analyte sensing compound). Optionally, such methods use pulsed and / or varying working potentials to observe signals at the electrodes.

[0098] The sensor of the present invention can also be incorporated into a variety of medical systems known in the art. The sensor of the present invention can be used in, for example, a closed-loop infusion system designed to control the rate at which a drug is infused into a user's body. Such a closed-loop infusion system can include a sensor and an associated meter that generates an input to a controller that in turn operates a delivery system (e.g., a system that calculates the dose to be delivered by a drug infusion pump). In such cases, the meter associated with the sensor can also transmit commands to the delivery system and can be used to remotely control the delivery system. Typically, the sensor is a subcutaneous sensor that contacts interstitial fluid to monitor the glucose concentration in the user's body, and the liquid infused into the user's body by the delivery system contains insulin. Illustrative systems are disclosed in, for example, U.S. Patents 6,558,351 and 6,551,276; PCT Applications US 99 / 21703 and US99 / 22993; and WO 2004 / 008956 and WO 2004 / 009161, all of which are incorporated herein by reference.

[0099] Certain embodiments of the present invention measure peroxide and have the advantageous property of being suitable for implantation in various locations within a mammal, including subcutaneous and intravenous implantation, as well as in various non-vascular areas. Due to the potential for oxygen noise issues with oxygen sensors implanted in non-vascular areas, peroxide sensor designs that allow for implantation in non-vascular areas offer advantages over certain sensor device designs that measure oxygen. For example, in such implantable oxygen sensor device designs, oxygen noise at the reference sensor can compromise the signal-to-noise ratio, thereby interfering with the implantable oxygen sensor device's ability to obtain stable glucose readings in such environments. Thus, the sensors of the present invention overcome the difficulties observed with such oxygen sensors in non-vascular areas.

[0100] In some embodiments of the present invention, the analyte sensor device is designed to work via anodic polarization so that a change in current is detected at the anode working electrode in the conductive layer of the analyte sensor device. The structural design features that can be associated with anodic polarization include designing an appropriate sensor configuration, which includes a working electrode as an anode, a counter electrode as a cathode, and a reference electrode, and then selectively setting an appropriate analyte sensing layer on an appropriate portion of the anode surface within the design configuration. Optionally, this anodic polarization structural design includes anodes, cathodes, and / or working electrodes with different surface areas. For example, this structural design includes features in which the coating surface of the working electrode (anode) and / or the working electrode is larger or smaller than the coating surface of the counter electrode (cathode) and / or the counter electrode (for example, the sensor is designed to have a 1X area for the reference electrode, a 2.6X area for the working electrode, and a 3.6X area for the counter electrode). In this case, the current change that can be detected at the anode working electrode is associated with the concentration of the analyte. In certain illustrative examples of this embodiment of the present invention, the working electrode measures and utilizes hydrogen peroxide in the oxidation reaction (see, for example Figure 1 ), hydrogen peroxide is produced by the reaction of enzymes such as glucose oxidase or lactate oxidase with glucose or lactate, respectively.

[0101] II. Illustrative Methods and Materials for Making Analyte Sensor Devices of the Present Invention

[0102] Numerous articles, US patents, and patent applications describe the prior art with the general methods and materials disclosed herein, and further describe various elements (and methods for their manufacture) that can be used with the sensor designs disclosed herein. These include, for example, U.S. Patent Nos. 6,413,393; 6,368,274; 5,786,439; 5,777,060; 5,391,250; 5,390,671; 5,165,407; 4,890,620; 5,390,671; 5,390,691; 5,391,250; 5,482,473; 5,299,571; 5,568,806; U.S. Patent Application 20020090738; and PCT International Publication Nos. WO 01 / 58348, WO 03 / 034902, WO 03 / 035117, WO 03 / 035891, WO 03 / 023388, WO 03 / 022128, WO 03 / 022352, WO 03 / 023708, WO 03 / 036255, WO 03 / 036310, and WO 03 / 074107, the contents of each of which are incorporated herein by reference.

[0103] Typical sensors for monitoring glucose concentration in diabetic patients are further described in Shichiri et al., "In Vivo Characteristics of Needle-Type Glucose Sensor - Measurements of Subcutaneous Glucose Concentrations in Human Volunteers," Horm. Metab. Res., Supplement Series 20: 17-20 (1988); Bruckel et al., "In Vivo Measurement of Subcutaneous Glucose Concentrations with an Enzymatic Glucose Sensor and a Wick Method," Klin. Wochenschr. 67: 491-495 (1989); and Pickup et al., "In Vivo Molecular Sensing in Diabetes Mellitus: An Implantable Glucose Sensor Using Direct Electron Transfer."

[0015] Other sensors are described, for example, in Reach et al., Advances in Implantable Devices, A. Turner (ed.), London, JAI Press, Chapter 1 (1993), which is incorporated herein by reference.

[0104] A. General Methods for Fabricating Analyte Sensors

[0105] A typical embodiment of the invention disclosed herein is a method of making a sensor device for implantation in a mammal, the method comprising the steps of: providing a substrate layer; forming a conductive layer on the substrate layer, wherein the conductive layer comprises electrodes (and typically a working electrode, a reference electrode, and a counter electrode); forming a dexamethasone-inhibiting membrane on the conductive layer, forming an analyte-sensing layer on the dexamethasone-inhibiting membrane, wherein the analyte-sensing layer comprises a composition that can change the current at the electrode in the conductive layer in the presence of an analyte; optionally forming a protein layer on the analyte-sensing layer; forming an adhesion-promoting layer on the analyte-sensing layer or the optional protein layer; forming an analyte-modulating layer disposed on the adhesion-promoting layer, wherein the analyte-modulating layer comprises a composition that modulates the diffusion of an analyte through the analyte-modulating layer; and forming a covering layer disposed on at least a portion of the analyte-modulating layer, wherein the covering layer further comprises pores located above at least a portion of the analyte-modulating layer. In certain embodiments of the invention, the analyte-modulating layer comprises a hydrophilic comb copolymer having a central chain and a plurality of side chains coupled to the central chain, wherein at least one side chain comprises a siloxane moiety. In some embodiments of these methods, the analyte sensor device is formed in a planar geometric configuration.

[0106] As disclosed herein, the various layers of the sensor can be manufactured to exhibit a variety of different properties that can be manipulated depending on the specific design of the sensor. For example, the adhesion promoting layer includes a compound selected to stabilize the overall sensor structure, typically a silane composition. In some embodiments of the present invention, the analyte sensing layer is formed by a spin coating process and has a thickness selected from the group consisting of: less than 1 micron, 0.5 micron, 0.25 micron, and 0.1 micron in height. In other embodiments of the present invention, the analyte sensing layer is formed by a slot coating process and has a thickness between 3.5 microns and 10 microns.

[0107] The method of making a sensor generally includes forming a protein layer on an analyte sensing layer, wherein the protein in the protein layer is an albumin selected from the group consisting of bovine serum albumin and human serum albumin. The method of making a sensor generally includes forming an analyte sensing layer, wherein the analyte sensing layer includes an enzyme composition selected from the group consisting of glucose oxidase, glucose dehydrogenase, lactate oxidase, hexokinase, and lactate dehydrogenase. In such methods, the analyte sensing layer generally includes a carrier protein composition having a substantially fixed ratio with the enzyme, and the enzyme and carrier protein are distributed in a substantially uniform manner throughout the analyte sensing layer.

[0108] B. Typical Protocols and Materials Used in Fabricating Analyte Sensors

[0109] The disclosure provided herein includes sensors and sensor designs that can be produced using a combination of various well-known technologies. The disclosure further provides methods for applying very thin enzyme coatings to these types of sensors and sensors produced by these methods. In this case, some embodiments of the present invention include methods for manufacturing such sensors on substrates according to methods generally recognized in the art. In certain embodiments, the substrate includes a rigid and flat structure suitable for photolithography masks and etching methods. In this regard, the substrate generally defines an upper surface with highly uniform flatness. Polished glass plates can be used to define a smooth upper surface. Alternative substrate materials include, for example, stainless steel, aluminum, and plastic materials, such as delrin (delrin) etc. In other embodiments, the substrate is non-rigid and can be another layer of film or insulator used as a substrate, for example, plastics such as polyimide.

[0110] The initial steps in the method of the present invention generally include forming a base layer for the sensor. The base layer can be placed on the substrate in any desired manner, such as by controlled spin coating. In addition, if there is not enough adhesion between the base layer and the base layer, an adhesive can be used. A base layer of insulating material is formed on the substrate, which is usually done by applying the base layer material to the substrate in liquid form and then rotating the substrate to obtain a thin, substantially uniform thickness base layer. These steps are repeated to create a base layer of sufficient thickness, followed by a series of photolithography and / or chemical masking and etching steps to form the conductors discussed below. In an illustrative form, the base layer includes a thin film sheet with an insulating material, such as a ceramic or polyimide substrate. The base layer can include an aluminum oxide substrate, a polyimide substrate, a glass sheet, a controlled pore glass, or a planarized plastic liquid crystal polymer. The base layer can be obtained from any material containing one or more of various elements, including but not limited to carbon, nitrogen, oxygen, silicon, sapphire, diamond, aluminum, copper, gallium, arsenic, lanthanum, neodymium, strontium, titanium, yttrium, or a combination thereof. Additionally, the substrate can be coated onto a solid support by a variety of methods well known in the art including physical vapor deposition or spin coating with materials such as spin glass, chalcogenides, graphite, silica, organic synthetic polymers, and the like.

[0111] The method of the present invention further comprises producing a conductive layer with one or more sensing elements. Typically, these sensing elements are electrodes formed by one of various methods known in the art such as photolithography, etching and rinsing for defining the geometry of the active electrode. The electrode can then be made electrochemically active, for example, by electro-depositing Pt black to the working electrode and the counter electrode, and then electro-depositing silver chloride after electro-depositing silver on the reference electrode. The sensor layer (such as the analyte sensing enzyme layer) can then be arranged on the sensing layer by electrochemical deposition or other methods (such as spin coating) except electrochemical deposition, followed by steam cross-linking with dialdehyde (glutaraldehyde) or carbodiimide.

[0112] The electrodes of the present invention can be formed from a variety of materials known in the art. For example, the electrodes can be made of late transition noble metals. Metals such as gold, platinum, silver, rhodium, iridium, ruthenium, palladium or osmium may be suitable for various embodiments of the present invention. In certain sensor embodiments, other compositions such as carbon or mercury are also useful. Among these metals, silver, gold or platinum are commonly used as reference electrode metals. A subsequently chlorinated silver electrode is commonly used as a reference electrode. These metals can be deposited by any means known in the art, including the electrodeposition methods cited above, or by electroless deposition, which may involve depositing the metal onto a previously metallized area when the substrate is immersed in a solution containing a metal salt and a reducing agent. The electroless method continues when the reducing agent contributes electrons to the conductive (metallized) surface, accompanied by reduction of the metal salt at the conductive surface. The result is a layer of adsorbed metal. (For additional discussion of electroless methods, see: Wise, EM Palladium: Recovery, Properties, and Uses, Academic Press, New York, NY (1988); Wong, K. et al., Plating and Surface Finishing, 1988, 75, 70-76; Matsuoka, M. et al., supra, 1988, 75, 102-106; and Pearlstein, F., "Electroless Plating," in Modern Electroplating, Lowenheim, FA, ed., Wiley, New York, NY (1974), Chapter 31.) However, such metal deposition processes must produce structures with excellent metal-to-metal adhesion and minimal surface contamination to provide a high density of active sites to the catalytic metal electrode surface. Such a high density of active sites is a necessary property for efficient redox conversion of electroactive species such as hydrogen peroxide.

[0113] In an exemplary embodiment of the present invention, a substrate is first coated with a thin film conductive layer by electrodeposition, surface sputtering or other suitable method steps. In one embodiment, this conductive layer can be provided as a plurality of thin film conductive layers, such as an initial chromium-based layer suitable for chemical adhesion to a polyimide substrate, followed by a gold-based thin film layer and a chromium-based thin film layer formed in sequence. In alternative embodiments, other electrode layer structures or materials can be used. The conductive layer is then covered with a selected photoresist coating according to conventional photolithographic techniques, and a contact mask can be applied over the photoresist coating for suitable photoimaging. The contact mask typically contains one or more conductor trace patterns for appropriately exposing the photoresist coating, followed by an etching step to retain a plurality of conductive sensor traces on the substrate. In an illustrative sensor configuration designed for use as a subcutaneous glucose sensor, each sensor trace can include three parallel sensor elements corresponding to three separate electrodes (such as a working electrode, a counter electrode, and a reference electrode).

[0114] Portions of the sensor conductive layer are typically covered by an insulating covering layer, which is typically a material such as a silicone polymer and / or polyimide. The insulating covering layer can be applied in any desired manner. In an exemplary procedure, the insulating covering layer is applied over the sensor traces as a liquid layer, after which the substrate is rotated to distribute the liquid material as a thin film over the sensor traces and extend the liquid material as a thin film beyond the edge margin of the sensor traces in sealing contact with the substrate layer. This liquid material can then undergo one or more suitable radiation and / or chemical and / or thermal curing steps as known in the art. In alternative embodiments, the liquid material can be applied using a spraying technique or any other desired application method. Various insulating layer materials can be used, such as photoimageable epoxy acrylates, with illustrative materials including photoimageable polyimide available from OCG, Inc. of West Paterson, NJ as product number 7020.

[0115] In certain embodiments of the present invention, the materials used to form one or more layers of the sensor stack are selected to control their diffusion coefficients for one or more compounds, such as O or glucose. Typically, for example, the material forming the dexamethasone inhibitory membrane and / or the material forming the analyte modulating layer is selected so that the diffusivity of the O diffusion coefficient through the layer is at least 1.0×10-1 at 37° C. in phosphate buffered saline. -5 cm 2 / s (e.g. 1.0×10 -5 cm 2 / s and 3.0×10 -5 cm 2Similarly, in illustrative embodiments of the present invention, the material forming the dexamethasone inhibitory membrane and / or the material forming the analyte modulating layer is selected to exhibit a kinetic energy of at least 1×10 - 8 cm 2 / s glucose permeability.

[0116] In the illustrative sensor embodiment used as glucose sensor, enzyme (usually glucose oxidase) is coated with enzyme to limit working electrode. Can provide the coating identical with working electrode to one or two electrodes in other electrodes. Alternatively, can provide other suitable chemical substances such as other enzymes etc. uncoated to other two electrodes, or be provided with chemical substances to limit the reference electrode and the counter electrode of electrochemical sensor. The method for producing enzyme coating comprises spin coating process, soaking and drying process, low shear spraying process, inkjet printing process, screen process etc. Usually, this type of coating is cross-linked by steam after its application. Surprisingly, the material properties of the sensor produced by these processes exceed the material properties of the sensor with the coating produced by electrodeposition, and this material properties comprises the life-span, linearity, regularity and the signal-to-noise ratio of improvement of raising. In addition, the embodiment of the present invention utilizing the glucose oxidase coating formed by this type of process is designed to recycle hydrogen peroxide and improve the biocompatibility profile of this type of sensor.

[0117] Sensors produced using processes such as spin coating also avoid other issues associated with electrodeposition, such as issues related to material stress placed on the sensor during the electrodeposition process. Specifically, it has been observed that the electrodeposition process generates mechanical stresses on the sensor, such as those caused by tension and / or compression. In some cases, such mechanical stresses can produce sensors with coatings that are prone to cracking or delamination to some extent. This is not observed in coatings applied to sensors via spin coating or other low-stress processes.

[0118] In some embodiments of the present invention, the sensor is manufactured by applying an analyte regulating layer comprising a hydrophilic membrane coating, which can regulate the amount of analyte that can approach the enzyme of the sensor layer. For example, the cover layer added to the glucose sensor of the present invention can include a glucose limiting membrane that regulates the amount of glucose approaching the glucose oxidase layer on the electrode. Such glucose limiting membranes can be made of a variety of materials known to be suitable for such purposes, for example, siloxanes such as polydimethylsiloxane, polyurethane, cellulose acetate, NAFION, polyester sulfonic acid (for example, Kodak AQ), hydrogels or any other membrane known to those skilled in the art for such purposes. In certain embodiments of the present invention, the analyte regulating layer includes a hydrophilic comb copolymer having a central chain and multiple side chains coupled to the central chain, wherein at least one side chain includes a siloxane moiety. In some embodiments of the present invention relating to sensors with hydrogen peroxide recycling capabilities, the membrane layer provided on the glucose oxidase layer acts to suppress the release of hydrogen peroxide into the environment in which the sensor is placed and promotes hydrogen peroxide molecules to approach the electrode sensing element.

[0119] In some embodiments of the method of the present invention, the adhesion promoter layer is arranged between the cover layer (for example, analyte regulating membrane layer) and the analyte sensing layer to promote its contact and is selected to be able to increase the stability of the sensor device. As described herein, the composition of the adhesion promoter layer is selected to provide many desired characteristics in addition to the ability to provide sensor stability. For example, some compositions used in the adhesion promoter layer are selected to work in dexamethasone inhibition and control the mass transfer of the desired analyte. The adhesion promoter layer can be made of any of the various materials for promoting the adhesion between such layers known in the art, and can be applied by any of the various methods known in the art. The adhesion promoter layer generally includes a silane compound, such as γ-aminopropyltrimethoxysilane. In certain embodiments of the present invention, the adhesion promoter layer and / or the analyte regulating layer include the reagent selected according to the ability of the siloxane part present in its cross-linked proximal layer. In other embodiments of the present invention, the adhesion promoter layer and / or the analyte regulating layer include the reagent selected according to the ability of the amine or carboxyl part of the protein present in its cross-linked proximal layer. In an optional embodiment, the AP layer also includes polydimethylsiloxane (PDMS), a polymer commonly found in analyte modulating layers such as glucose limiting membranes. In illustrative embodiments, the formulation includes 0.5%-20% PDMS, typically 5%-15% PDMS, and most typically 10% PDMS. Adding PDMS to the AP layer is advantageous in reducing the likelihood of holes or gaps forming in the AP layer during sensor fabrication.

[0120] An illustrative embodiment of the present invention is a method for manufacturing a sensor electrode by providing an electroactive surface that can be used as an electrode (e.g., platinum), forming a dexamethasone inhibitory film on the electroactive surface, spin coating, slot coating or spray coating an enzyme layer on the DRM, and then forming an analyte contact layer (e.g., an analyte regulating layer, such as a glucose limiting membrane) on the electrode, wherein the analyte contact layer regulates the amount of analyte that can contact the enzyme layer. In some methods, the enzyme layer is steam cross-linked on the sensor layer. In typical embodiments of the present invention, the sensor is formed to include at least one working electrode and at least one counter electrode. In certain embodiments, the DRM is formed on at least a portion of the working electrode and at least a portion of the counter electrode. Typically, the enzyme layer includes one or more enzymes, such as glucose oxidase, glucose dehydrogenase, lactate oxidase, hexokinase or lactate dehydrogenase and / or similar enzymes. In a specific method, the enzyme layer includes glucose oxidase, which is stabilized by being coated on the sensor layer with a carrier protein at a fixed ratio. Typically, the carrier protein is albumin. Typically, such methods include the step of forming an adhesion promoter layer between the glucose oxidase layer and the analyte contact layer. Optionally, prior to forming the analyte contact layer, layers such as the DRM and / or adhesion promoter layer are cured.

[0121] The finished sensors produced by such methods are typically quickly and easily removed from the supporting substrate (if used), for example, by cutting along a line on the substrate surrounding each sensor. The cutting step can use methods commonly used in the art, such as a method including a UV laser cutting device, which is used to cut the base layer and cover layer and the functional coating along a line surrounding or encircling each sensor (typically with at least a slight outwardly spaced relationship from the conductive element), so that enough interconnected base layer and cover layer material remains to seal the side edges of the finished sensor. In addition, cutting techniques commonly used for cutting ceramic substrates can be used with appropriate sensor embodiments. Because the base layer is typically not directly physically attached or only minimally directly attached to the underlying supporting substrate, the sensor can be quickly and easily lifted from the supporting substrate without the need for significant further processing steps or potential damage caused by stress caused by physically pulling or peeling the attached sensor from the supporting substrate. Thereafter, the supporting substrate can be subsequently cleaned and reused, or otherwise discarded. The functional coating can be applied before or after the other sensor components are removed from the supporting substrate (e.g., by cutting).

[0122] III. Methods for Using the Analyte Sensor Devices of the Present Invention

[0123] A related embodiment of the present invention is a method of sensing an analyte in a mammal, the method comprising implanting an analyte sensor embodiment disclosed herein into the mammal, and then sensing one or more electrical fluctuations, such as a change in current, at a working electrode and correlating the change in current with the presence of an analyte, such that the analyte is sensed. In one such method, the analyte sensor device senses glucose in the mammal. In alternative methods, the analyte sensor device senses lactate, potassium, calcium, oxygen, pH, and / or any physiologically relevant analyte in the mammal.

[0124] Some analyte sensors with the structure discussed above have many highly desirable properties that allow various methods for sensing analytes in mammals. For example, in such methods, an analyte sensor device implanted in a mammal is used to sense an analyte in the mammal for more than 1 month, 2 months, 3 months, 4 months, 5 months, or 6 months. Typically, the analyte sensor device so implanted in a mammal senses a change in current in response to the analyte within 15 minutes, 10 minutes, 5 minutes, or 2 minutes of the analyte contacting the sensor. In such methods, the sensor can be implanted in various locations in the mammal, such as in both vascular and non-vascular spaces.

[0125] IV. Kits and Sensor Kits of the Present Invention

[0126] In another embodiment of the present invention, a test kit and / or sensor kit for sensing an analyte as described above is provided. Test kit and / or sensor kit generally include a container, a label and an analyte sensor as described above. Suitable containers include, for example, packaging, bottles, vials, syringes and test tubes that are easy to open made of materials such as metal foil. The container can be formed from a variety of materials, such as metal (e.g., foil) paper products, glass or plastic. A label on or associated with the container indicates that the sensor is used to analyze the selected analyte. In some embodiments, the container is equipped with a porous matrix coated with a layer of enzyme such as glucose oxidase. The test kit and / or sensor kit may also include other materials desired from a commercial and user perspective, including elements or devices designed to facilitate the introduction of the sensor into the analyte environment, other buffers, diluents, filters, needles, syringes and packaging inserts with instructions for use.

[0127] in conclusion

[0128] This section concludes the description of the preferred embodiments of the present invention. The foregoing description of one or more embodiments of the present invention has been presented for the purposes of illustration and description. It is not intended to be exhaustive or to limit the invention to the precise forms disclosed. Many modifications and variations are possible in light of the above teachings.

[0129] All publications, patents, and patent applications cited herein are hereby incorporated by reference in their entirety for all purposes.

Claims

1. A method of manufacturing a sensor device for implantation in a mammal, the method comprising the steps of: Provides a base layer; forming a conductive layer on the base layer, wherein the conductive layer includes a working electrode; Dexamethasone inhibition film formation; forming an analyte sensing layer, wherein the analyte sensing layer comprises an oxidoreductase; and An analyte modulating layer is formed, wherein the analyte modulating layer comprises a composition that modulates diffusion of the analyte through the analyte modulating layer.

2. The method of claim 1, wherein the method comprises disposing a dexamethasone compound on the sensor.

3. The method of claim 1, wherein the dexamethasone-inhibiting membrane comprises a poly (2-hydroxyethyl methacrylate) composition.

4. The method of claim 3, wherein the poly(2-hydroxyethyl methacrylate) composition comprises a poly(2-hydroxyethyl methacrylate) polymer.

5. The method of claim 1, wherein the poly(2-hydroxyethyl methacrylate) composition comprises prepolymerized poly(2-hydroxyethyl methacrylate) monomer.

6. The method of claim 1, wherein the dexamethasone-inhibiting membrane comprises about: 50% (w / v) to 80% (w / v) tetra(ethylene glycol) diacrylate; in combination with 0.5% (w / v) to 10% (w / v) methacryloxyethyl phosphorylcholine (MPC).

7. The method of claim 1, wherein the dexamethasone-inhibiting membrane comprises about: 60% (w / v) to 70% (w / v) tetra(ethylene glycol) diacrylate; in combination with 1.0% (w / v) to 1% (w / v) methacryloxyethyl phosphorylcholine (MPC).

8. A sensor device for implantation in a mammal, the sensor device comprising: basal layer; a conductive layer, the conductive layer being disposed on the base layer, wherein the conductive layer comprises a working electrode; a dexamethasone inhibitory membrane, wherein the dexamethasone inhibitory membrane is disposed above the working electrode; an analyte sensing layer, wherein the analyte sensing layer comprises an oxidoreductase; and An analyte modulating layer, wherein the analyte modulating layer comprises a composition that modulates diffusion of the analyte through the analyte modulating layer.

9. The sensor device of claim 8, further comprising a dexamethasone compound.

10. The sensor device of claim 8, wherein the dexamethasone-inhibiting membrane comprises a poly (2-hydroxyethyl methacrylate) composition. 11 . The sensor device of claim 10 , wherein the poly(2-hydroxyethyl methacrylate) composition comprises a poly(2-hydroxyethyl methacrylate) polymer. 12 . The sensor device of claim 10 , wherein the poly(2-hydroxyethyl methacrylate) composition comprises pre-polymerized poly(2-hydroxyethyl methacrylate) monomers.

13. The sensor device of claim 10, wherein the dexamethasone-inhibiting film comprises approximately: 50% (w / v) to 80% (w / v) tetra(ethylene glycol) diacrylate; in combination with 0.5% (w / v) to 10% (w / v) methacryloxyethyl phosphorylcholine (MPC).

14. The sensor device of claim 8, wherein the dexamethasone-inhibiting film comprises approximately: 60% (w / v) to 70% (w / v) tetra(ethylene glycol) diacrylate; in combination with 1.0% (w / v) to 1% (w / v) methacryloxyethyl phosphorylcholine (MPC).

15. A method for estimating glucose concentration in a body, the method comprising: placing the sensor device of claim 1 into an in vivo environment of a subject, wherein the environment comprises glucose; as well as estimating the concentration of the glucose; This allows estimation of the glucose concentration in the body.

16. The method of claim 13, wherein the sensor device comprises a dexamethasone compound.

17. The method of claim 13, wherein the dexamethasone-inhibiting membrane comprises a poly (2-hydroxyethyl methacrylate) composition.

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