Analyte sensors for sensing ketones and methods of using the same

Abstract

The present disclosure provides analyte sensors for use in the detection of ketones. In certain embodiments, the ketone-responsive active sites of the analyte sensors disclosed herein include an enzyme system comprising a β-hydroxybutyrate dehydrogenase and an NADH oxidase disposed on the surface of a platinum working electrode. The present disclosure also provides methods of detecting ketones with the analyte sensors of the present disclosure.

Description

[0001] Cross-reference with related applications

[0002] This application claims priority to U.S. Provisional Application No. 63 / 123,897, filed December 10, 2020, and U.S. Provisional Application No. 63 / 135,373, filed January 8, 2021, by incorporation of their respective contents in their entirety, and claims priority to their respective applications.

[0003] field

[0004] The topics described in this article relate to analyte sensors for sensing ketones and methods for using them.

[0005] background

[0006] Detecting various analytes in an individual can sometimes be crucial for monitoring their health because deviations from normal analyte levels can indicate physiological conditions. For example, monitoring ketone levels allows individuals with diabetes to take appropriate corrective action to avoid the significant physiological harm of ketoacidosis. Other analytes may be desirable for monitoring other physiological conditions. In some cases, it may be desirable to monitor more than one analyte to monitor multiple physiological conditions, especially if the person has a comorbidity causing simultaneous dysregulation of two or more combined analytes.

[0007] Analytical monitoring in an individual can occur periodically or continuously over a period of time. Periodic analytical monitoring can be performed by drawing samples of bodily fluids, such as blood or urine, at set time intervals and analyzing them in vitro. Periodic in vitro analytical monitoring can be sufficient to determine the physiological status of many individuals. However, in some cases, in vitro analytical monitoring can be inconvenient or painful. Furthermore, if analyte measurements are not obtained at the appropriate time, there is no way to recover lost data. Continuous analytical monitoring can be performed using one or more sensors that are at least partially implanted (e.g., in the skin, subcutaneously, or intravenously) within the individual's tissues, enabling in vivo analysis. The implanted sensor can collect analyte data on demand, according to a set schedule, or continuously, depending on the individual's specific health needs and / or pre-measured analyte levels. For individuals with severe analyte dysregulation and / or rapidly fluctuating analyte levels, analytical monitoring with in vivo implanted sensors may be a more promising approach, but it can also be beneficial for other individuals. Since implanted analyte sensors often remain within an individual's tissues for an extended period of time, it is highly desirable that the analyte sensors be prepared from stable materials exhibiting high biocompatibility.

[0008] Many analytes represent interesting targets for physiological analysis, provided that suitable detection chemistry can be identified. To this end, enzyme-based current sensors configured for the continuous in vivo testing of glucose have been developed and improved in recent years to aid in the monitoring of the health of individuals with diabetes. Other analytes that are generally dysregulated in conjunction with glucose in individuals with diabetes include, for example, lactate, oxygen, A1c, and ketones. It is also desirable to monitor these and other analytes independently of glucose dysregulation. Analytical sensors configured for the in vivo detection of analytes other than glucose are known but have not yet been significantly improved. For example, poor sensitivity to low-abundance analytes can be particularly problematic. Accordingly, there is a need in the art for improved sensors for the in vivo detection of ketones.

[0009] summary

[0010] The intent and advantages of this disclosure will be clearly described below and will become apparent by practicing it. Additional advantages of this disclosure will be understood and obtained from the means particularly pointed out in the specification and its claims and from the accompanying drawings.

[0011] As embodied and broadly described, in order to achieve these and other advantages and in accordance with the intent of this disclosure, the subject matter includes an analyte sensor comprising: a sensor tail including at least a first working electrode, a ketone-responsive active region disposed on the surface of the first working electrode, and a ketone-permeable mass transport restriction membrane covering at least a portion of the ketone-responsive active region. In some embodiments, the ketone-responsive active region comprises an enzyme system comprising β-hydroxybutyrate dehydrogenase and NADH oxidase. In some embodiments, the first working electrode is a platinum electrode. In some embodiments, the ketone-responsive active region does not include an electron transfer reagent. In some embodiments, the ketone-responsive active region does not include superoxide dismutase.

[0012] In some embodiments, the ketone-responsive active region further includes a stabilizer and / or a crosslinking agent. In some embodiments, one or more enzymes from an enzyme system comprising β-hydroxybutyrate dehydrogenase and NADH oxidase are covalently bonded to a stabilizer in the ketone-responsive active region. In some embodiments, one or more enzymes from an enzyme system comprising β-hydroxybutyrate dehydrogenase and NADH oxidase are covalently bonded to a polymer in the ketone-responsive active region. In some embodiments, the mass transport restriction membrane comprises polyvinylpyridine, polyvinylimidazolium, a polyvinylpyridine copolymer, polyacrylate, polyurethane, polyether polyurethane, or a combination thereof. In some embodiments, the mass transport restriction membrane comprises polyvinylpyridine. Alternatively or additionally, the mass transport restriction membrane comprises a copolymer of vinylpyridine and styrene.

[0013] In some embodiments, the analyte sensor of this disclosure further includes a second working electrode and a second active region disposed on the surface of the second working electrode and responsive to a second analyte different from ketones. In some embodiments, the second active region includes at least one enzyme responsive to the second analyte. In some embodiments, a second portion of a mass transport restriction membrane covers the second active region. In some embodiments, the second analyte includes glucose.

[0014] In some embodiments, the sensor tail is configured for insertion into tissue, for example, for detecting ketone levels in vivo. In some embodiments, the ketone-responsive active region responds to ketones at a potential of about +0.2 V to about +0.5 V relative to an Ag / AgCl reference. In some embodiments, the ketone-responsive active region responds to ketones at a potential of about +0.3 V to about +0.4 V relative to an Ag / AgCl reference. In some embodiments, the ketone-responsive active region responds to ketones at a potential of about +0.35 V relative to an Ag / AgCl reference.

[0015] This disclosure also provides a method for detecting ketones. In some embodiments, the method may include providing an analyte sensor comprising (a) a sensor tail including at least a first working electrode, wherein the first working electrode is a platinum electrode; (b) a ketone-responsive active region disposed on the surface of the first working electrode, wherein the ketone-responsive active region comprises an enzyme system comprising β-hydroxybutyrate dehydrogenase and NADH oxidase; and (c) a ketone-permeable mass transport restriction membrane covering at least the ketone-responsive active region. In some embodiments, the method further includes applying a potential to the first working electrode, obtaining a first signal at or above a redox potential of the ketone-responsive active region, the first signal being proportional to the concentration of the ketone in a fluid contacting the ketone-responsive active region, and correlating the first signal with the concentration of the ketone in the fluid.

[0016] In some embodiments, the first working electrode is a platinum electrode. In some embodiments, the ketone-responsive active region does not include an electron transfer reagent. In some embodiments, the ketone-responsive active region does not include superoxide dismutase. In some embodiments, the ketone-responsive active region further includes a stabilizer and / or a crosslinking agent. In some embodiments, one or more enzymes in an enzyme system comprising β-hydroxybutyrate dehydrogenase and NADH oxidase are covalently bonded to a stabilizer in the ketone-responsive active region. In some embodiments, one or more enzymes in an enzyme system comprising β-hydroxybutyrate dehydrogenase and NADH oxidase are covalently bonded to a polymer in the ketone-responsive active region. In some embodiments, the mass transport restriction membrane comprises polyvinylpyridine, polyvinylimidazolium, a polyvinylpyridine copolymer, polyvinylpyrrolidone, polyacrylate, polyurethane, polyether polyurethane, or copolymers or combinations thereof. In some embodiments, the mass transport restriction membrane comprises polyvinylpyridine. Alternatively or additionally, the mass transport restriction membrane comprises a copolymer of vinylpyridine and styrene.

[0017] In some embodiments, the sensor tail is configured for insertion into tissue. In some embodiments, the ketone-responsive active region responds to a potential of about +0.2 V to about +0.5 V relative to an Ag / AgCl reference. In some embodiments, the ketone-responsive active region responds to a potential of about +0.3 V to about +0.4 V relative to an Ag / AgCl reference. In some embodiments, the ketone-responsive active region responds to a potential of about +0.35 V relative to an Ag / AgCl reference.

[0018] In some embodiments, the analyte sensor used in the methods of this disclosure may further include a second working electrode and a second active region disposed on the surface of the second working electrode and responsive to a second analyte different from ketones. In some embodiments, the second active region includes at least one enzyme responsive to the second analyte and a second portion of a mass transport restriction membrane covering the second active region. In some embodiments, the second analyte comprises glucose.

[0019] In some embodiments, the analyte sensor of this disclosure is used in subjects who require it. For example, but not limited to, the subject may be a diabetic subject. In some embodiments, the subject may be undergoing a ketogenic diet. In some embodiments, the subject is in a state of ketosis. Attached Figure Description

[0020] The figures below are included to illustrate certain aspects of this disclosure and should not be considered as exclusive embodiments. The disclosed subject matter can be considerably modified, altered, combined, and equivalent in form and function without departing from the scope of this disclosure.

[0021] Figure 1AThis is a system overview of sensor applicators, reader devices, monitoring systems, networks, and remote systems.

[0022] Figure 1B This is a diagram illustrating the operating environment of an example analyte monitoring system using the techniques described in this article.

[0023] Figure 1C A diagram of an exemplary sensing system is shown, which can be incorporated into the analyte sensor of this disclosure.

[0024] Figure 2A This is a block diagram illustrating an example implementation of the reader device.

[0025] Figure 2B This is a block diagram illustrating an example data receiving device for communicating with a sensor according to an exemplary embodiment of the subject matter of this disclosure.

[0026] Figure 2C and 2D This is a block diagram illustrating an example implementation of a sensor control device.

[0027] Figure 2E This is a block diagram illustrating an example of an analytical material sensor according to an exemplary embodiment of the subject matter of this disclosure.

[0028] Figure 3A This is a near-end perspective view illustrating an example implementation where a user prepares a tray for assembly.

[0029] Figure 3B This is a side view illustrating an example implementation where the user prepares the applicator device for assembly.

[0030] Figure 3C This is a near-end perspective view illustrating an example implementation where the user inserts the applicator device into the tray during assembly.

[0031] Figure 3D This is a near-end perspective view illustrating an example implementation where the user removes the applicator device from the tray during assembly.

[0032] Figure 3E This is a proximal perspective view illustrating an example implementation of a patient applying a sensor using an applicator device.

[0033] Figure 3F This is a proximal perspective view illustrating an example implementation of a patient equipped with applied sensors and an application device.

[0034] Figure 4A This is a side view illustrating an example implementation of an applicator device connected to a cover.

[0035] Figure 4BThis is a side perspective view illustrating an example implementation of the separate applicator device and cover.

[0036] Figure 4C This is a perspective view illustrating an example implementation of the applicator device's distal end and electronic housing.

[0037] Figure 4D This is a top perspective view of an exemplary applicator device in accordance with the subject matter of this disclosure.

[0038] Figure 4E yes Figure 4D Bottom perspective view of the applicator device.

[0039] Figure 4F yes Figure 4D Exploded view of the applicator device.

[0040] Figure 4G yes Figure 4D Side sectional view of the applicator device.

[0041] Figure 5 This is a near-end perspective view illustrating an example implementation of a tray with a sterilization cap attached.

[0042] Figure 6A This is a near-end perspective sectional view illustrating an example implementation of a tray with a sensor delivery assembly.

[0043] Figure 6B This is a near-end perspective view, depicting the sensor delivery assembly.

[0044] Figure 7A and 7B These are exploded top and bottom views of the exemplary sensor control device.

[0045] Figures 8A-8C An assembled and cross-sectional view of the device on the body, the device including an integrated connector for sensor assembly.

[0046] Figure 9A and 9B They are Figure 1A Side and cross-sectional side views of an example implementation of a sensor applicator, showing its connection to... Figure 2C The cover.

[0047] Figure 10A and 10B These are, respectively, the equivalent and side views of another example of a sensor control device.

[0048] Figure 11A-11C This is a progressive section side view showing the assembly of the sensor applicator, which has Figures 10A-10B Sensor control device.

[0049] Figures 12A-12C This is a progressive sectional side view showing the assembly and disassembly of an example implementation of the sensor applicator, which has Figures 10A-10B Sensor control device.

[0050] Figures 13A-13F A cross-sectional view is shown, illustrating an example implementation of the applicator during the application phase.

[0051] Figure 14 This figure illustrates an example of the in vitro sensitivity of an analyte sensor.

[0052] Figure 15 This is a diagram illustrating an example of the operational status of a sensor according to an exemplary embodiment of the subject matter of this disclosure.

[0053] Figure 16 This is a diagram illustrating an example of over-the-air programming operation and data flow for sensors based on the subject matter of this disclosure.

[0054] Figure 17 This is a diagram illustrating an example data flow that ensures the exchange of data between two devices pursuant to the subject of this disclosure.

[0055] Figures 18A-18C This shows a cross-sectional diagram of an analyte sensor, including a single active region.

[0056] Figures 19A-19C This diagram shows a cross-sectional view of an analyte sensor comprising two active regions.

[0057] Figure 20 This diagram shows a cross-sectional view of an analyte sensor comprising two active regions.

[0058] Figures 21A-21C This shows a perspective view of the analyte sensor, which includes two active regions on separate working electrodes.

[0059] Figure 22 A diagram showing a specific enzyme system, which, according to this disclosure, can be used to detect ketones.

[0060] Figure 23 Show the voltammetry of NADH and NADH + hydrogen peroxide (H2O2).

[0061] Figure 24 The results show four replicates of the current response when exposed to varying concentrations of β-hydroxybutyrate, from electrodes containing NAD+, NADH oxidase, and β-hydroxybutyrate dehydrogenase, compared to a control without NADH oxidase.

[0062] Figure 25 show Figure 24 An exemplary graph showing the sensor current response of the electrode versus the concentration of β-hydroxybutyric acid.

[0063] Detailed Explanation

[0064] This disclosure generally describes an analyte sensor that uses one or more enzymes to detect an analyte. For example, but not limited to, this disclosure provides an analyte sensor that uses multiple enzymes to detect an analyte, such as one or more ketones. In some embodiments, this disclosure also provides an analyte sensor that uses multiple enzymes to detect two different analytes, for example, using multiple enzymes to detect a ketone and a second analyte, such as glucose. Depending on the sensor construction, the analyte sensor of this disclosure can be configured to detect one or more analytes simultaneously or nearly simultaneously. This disclosure also provides a method for detecting one or more analytes using the analyte sensor of this disclosure.

[0065] Glucose-responsive analyte sensors are a well-studied and still-developing field that helps individuals with diabetes better manage their health. Although comorbid analyte dysregulation is common in individuals with diabetes, sensor chemistry suitable for detecting ketones and other analytes that are generally dysregulated has lagged significantly behind the development of more advanced glucose detection chemistry. This disclosure alleviates this deficiency by providing sensor chemistry, and particularly detection chemistry, suitable for detecting ketones with good response stability at a wide range of ketone concentrations. This detection chemistry utilizes an enzyme system to facilitate ketone detection, said enzyme system comprising at least two enzymes capable of synergistic action. As used herein, the term "synergistic" refers to paired enzymatic reactions in which the product of a first enzymatic reaction becomes the substrate of a second enzymatic reaction, and the second enzymatic reaction serves as the basis for measuring the concentration of the substrate (e.g., analyte) reacted during the first enzymatic reaction. In some embodiments, the product and / or substrate of the reaction can be a cofactor of the enzyme in the enzyme system or a reduced and / or oxidized form of a coenzyme such as NAD or NADP. Although defined by two paired enzymatic reactions, it should be recognized that in some cases more than two enzymatic reactions can also be matched. For example, the product of the first enzymatic reaction can become the substrate of the second enzymatic reaction, and the product of the second enzymatic reaction can become the substrate of the third enzymatic reaction, which serves as the basis for measuring the concentration of the substrate (e.g., analyte) reacted during the first enzymatic reaction. Suitable enzyme systems for the detection of ketones according to the present invention are discussed below.

[0066] For clarity, but not limitation, the detailed description of the subject matter of this disclosure is divided into the following sub-sections:

[0067] I. Definition; and

[0068] II. Analyte sensor;

[0069] 1. General structure of an analytical material sensor system;

[0070] 2. Enzymes;

[0071] 3. Redox mediators;

[0072] 4. Polymer backbone;

[0073] 5. Quality transport restriction film;

[0074] 6. Interference area; and

[0075] 7. Preparation;

[0076] III. Instructions for use; and

[0077] IV. Exemplary Implementation.

[0078] I. Definition

[0079] In the context of this disclosure and in the specific context in which each term is used, the terms used herein generally have their common meaning in the art. Certain terms are discussed below or in other parts of the specification to provide additional guidance to practitioners by describing the compositions and methods of this disclosure and how they are prepared and used.

[0080] As used herein, the word "a" or "an" in combination with the term "comprising" in the claims and / or description can mean "a kind," but it also corresponds to the meanings of "one or more," "at least one," and "one or more kinds."

[0081] The terms "comprising," "including," "having," "possessing," "capable of," "containing," and variations thereof, as used herein, are intended to be open-ended restrictive terms or wording that do not exclude additional actions or structures. This disclosure also contemplates that other embodiments "comprising," "consisting of," and "substantially constitute" the embodiments or elements shown herein, whether or not explicitly described.

[0082] The term "about" or "approximately" means within an acceptable range of error for a particular value, which is determined by those skilled in the art and depends in part on how the value is measured or determined, i.e., the limitations of the measurement system. For example, according to practice in the art, "about" can mean within three or more standard deviations. Alternatively, "about" can mean up to 20%, preferably up to 10%, more preferably up to 5%, and even more preferably up to 1% of a given value. Alternatively, particularly with respect to biological systems or processes, the term can mean within one order of magnitude of the value, preferably within five times, and more preferably within two times.

[0083] As used herein, "analyte sensor" or "sensor" can refer to any device capable of receiving sensor information from a user, including, but not limited to, body temperature sensors, blood pressure sensors, pulse or heart rate sensors, glucose level sensors, analyte sensors, body activity sensors, body motion sensors, or any other sensors used to collect physical or biological information. Analytes measured by an analyte sensor can include, for example, but not limited to, glucose, ketones, lactate, oxygen, hemoglobin A1C, albumin, alcohols, alkaline phosphatase, alanine aminotransferase, aspartate aminotransferase, bilirubin, blood urea nitrogen, calcium, carbon dioxide, chloride, creatinine, hematocrit, lactate, magnesium, oxygen, pH, phosphorus, potassium, sodium, total protein, uric acid, etc.

[0084] The term "biological fluid," as used herein, refers to any bodily fluid or bodily fluid derivative in which an analyte can be measured. Non-limiting examples of biological fluids include skin fluids, interstitial fluids, plasma, blood, lymph, synovial fluid, cerebrospinal fluid, saliva, bronchoalveolar lavage fluid, amniotic fluid, sweat, tears, etc. In some embodiments, the biological fluid is a skin fluid or interstitial fluid.

[0085] The term "electrolysis" as used herein refers to the electro-oxidation or electro-reduction of a compound directly at an electrode or via one or more electron transfer agents (e.g., redox mediators or enzymes).

[0086] As used herein, the term "homogeneous membrane" refers to a membrane containing a single type of membrane polymer.

[0087] As used herein, the term "multicomponent membrane" refers to a membrane comprising two or more types of membrane polymers.

[0088] As used herein, the term "polyvinylpyridine-based polymer" refers to a polymer or copolymer that contains polyvinylpyridine (e.g., poly(2-vinylpyridine) or poly(4-vinylpyridine)) or a derivative thereof.

[0089] As used herein, the term "redox mediator" refers to an electron transfer agent used to carry electrons between an analyte or an enzyme that reduces or oxidizes an analyte and an electrode, either directly or via one or more additional electron transfer agents. In some embodiments, redox mediators comprising a polymer backbone may also be referred to as "redox polymers."

[0090] The term "reference electrode" as used herein can refer to a reference electrode or an electrode that serves as both a reference and a counter electrode. Similarly, the term "counter electrode" as used herein can refer to a counter electrode and a counter electrode that also serves as a reference electrode.

[0091] II. Analyte Sensor

[0092] Before describing the subject matter of the invention in detail, it should be understood that this disclosure is not limited to the specific embodiments described, as variations are certainly possible. It should also be understood that the terminology used herein is for the purpose of describing specific embodiments only and is not intended to be limiting, as the scope of this disclosure will be limited only by the appended claims.

[0093] The public documents discussed herein are provided solely because they were published prior to the filing date of this application. Nothing herein is to be construed as an admission that this disclosure is not earlier than those disclosures by virtue of prior publication. Furthermore, the dates of the disclosures provided may differ from the actual dates of disclosures that may require independent verification.

[0094] Generally, embodiments of this disclosure include systems, apparatus, and methods for inserting an analyte sensor into an applicator for use in an in vivo analyte monitoring system. The applicator can be provided to a user in a sterile package, including an electronic housing of a sensor control device. According to some embodiments, a separate structure, such as a container, can also be provided to the user as a sterile package including a sensor module and a tip module. The user can connect the sensor module to the electronic housing and the tip to the applicator, the assembly process involving inserting the applicator into the container in a specified manner. In other embodiments, the applicator, sensor control device, sensor module, and tip module can be provided in a single package. The applicator can be used to position the sensor control device on the human body, where the sensor contacts the wearer's bodily fluids. The embodiments provided herein are various improvements that reduce the possibility of improper sensor insertion or damage or adverse physiological responses. Other improvements and advantages are also provided. Various configurations of these devices are described in detail with reference to embodiments that are merely examples.

[0095] In addition, many embodiments include in vivo analyte sensors, which are structurally configured such that at least a portion of the sensor is located or can be located within the user's body to obtain information about at least one analyte in the body. However, it should be noted that the embodiments disclosed herein can be used in in vivo analyte monitoring systems incorporating in vitro functionality, as well as entirely in vitro or ex vivo analyte monitoring systems, including completely non-invasive systems.

[0096] Furthermore, each embodiment of the methods disclosed herein, and the systems and apparatuses capable of performing those embodiments, are covered within the scope of this disclosure. For example, embodiments of sensor control devices are disclosed, and these devices can have one or more sensors, analyte monitoring circuitry (e.g., analog circuitry), memory (e.g., for storing instructions), power supply, communication circuitry, transmitter, receiver, processor, and / or controller (e.g., for executing instructions), which are capable of performing or facilitating the performance of any various method steps. These sensor control device embodiments can be used and are capable of performing those steps executed by the sensor control device, which are derived from any of the various methods described herein.

[0097] Furthermore, the systems and methods presented herein can be used to operate sensors used in analyte monitoring systems, such as, but not limited to, health, wellness, diet, research, information, or any intent involving sensing analytes over time. As used herein, "analyte sensor" or "sensor" can refer to any device capable of receiving sensor information from a user, including, for example purposes, including but not limited to, body temperature sensors, blood pressure sensors, pulse or heart rate sensors, glucose level sensors, analyte sensors, body activity sensors, body motion sensors, or any other sensors that collect physical or biological information. The analyte sensor of this disclosure measures ketones. In some embodiments, the analyte sensor of this disclosure can also measure analytes including but not limited to glucose, ketones, lactate, oxygen, hemoglobin A1C, albumin, alcohols, alkaline phosphatase, alanine aminotransferase, aspartate aminotransferase, bilirubin, blood urea nitrogen, calcium, carbon dioxide, chloride, creatinine, hematocrit, lactate, magnesium, oxygen, pH, phosphorus, potassium, sodium, total protein, uric acid, etc.

[0098] As mentioned, this document describes numerous embodiments of systems, apparatuses, and methods that provide improved assembly and application of skin sensor insertion devices for in vivo analyte monitoring systems. In particular, several embodiments of this disclosure are designed to improve sensor insertion methods for in vivo analyte monitoring systems, and especially to prevent premature retraction of the insertion tip during sensor insertion. For example, some embodiments include a skin sensor insertion mechanism with increased firing velocity and delayed tip retraction. In other embodiments, the tip retraction mechanism can be motion-activated, retracting the tip only when the user pulls the applicator away from the skin. Thus, these embodiments reduce the likelihood of premature retraction of the insertion tip during sensor insertion; reduce the likelihood of improper sensor insertion; and reduce the likelihood of sensor damage during sensor insertion, to name just a few advantages. Several embodiments of this disclosure also provide improved insertion tip modules adapted to small-scale skin sensors and relatively shallow insertion paths in the subject's skin layer. Furthermore, several embodiments of this disclosure are designed to prevent undesirable axial and / or rotational movement of the applicator assembly during sensor insertion. Accordingly, these embodiments can reduce the likelihood of skin sensor misalignment, stimulation at the insertion site, damage to surrounding tissues, and capillary rupture causing blood contamination of skin fluids, to name just a few advantages. Furthermore, to mitigate inaccurate sensor readings that can be caused by trauma to the insertion site, several embodiments of this disclosure can reduce the depth of needle penetration relative to the sensor tip during insertion.

[0099] However, before describing these aspects of the implementation in detail, it is desirable to first describe examples of devices that can exist, such as in vivo analyte monitoring systems, and examples of their operation, all of which can be used in the implementations described herein.

[0100] Various types of in vivo analyte monitoring systems exist. For example, a "continuous analyte monitoring" system (or "continuous glucose monitoring" system) can continuously send data from a sensor control device to a reader device without prompting, such as automatically according to a schedule. As another example, a "rapid analyte monitoring" system (or "rapid glucose monitoring" system, or simply "rapid" system) can respond to data scans or requests to transfer data from the sensor control device via a reader device, for example, using near field communication (NFC) or radio frequency identification (RFID) schemes. In vivo analyte monitoring systems can also operate without manual finger-prick calibration.

[0101] An in vivo analyte monitoring system is distinguishable from an "ex vivo" system that contacts biological samples outside the body (or "extracorporeal"). It generally includes a metering device with a port that receives an analyte test strip carrying the user's bodily fluids and can analyze the bodily fluids to determine the user's blood glucose level.

[0102] An in vivo monitoring system can include sensors that, when located inside the body, contact the user's bodily fluids and sense the levels of analytes contained therein. The sensors can be part of a sensor control unit located on the user's body and containing electronics and a power source capable of performing and controlling analyte sensing. Sensor control units and variations thereof can also be referred to as "sensor control units," "on-body electronics" devices or units, "on-body" devices or units, or "sensor data communication" devices or units, to name just a few.

[0103] In vivo monitoring systems can also include devices that receive sensed analyte data from sensor control devices and process the sensed analyte data and / or display the sensed analyte data to a user in any number of formats. Such devices and variations may be referred to as "handheld reader devices," "reader devices" (or simply "readers"), "handheld electronic devices" (or simply "handheld"), "portable data processing" devices or units, "data receivers," "receiver" devices or units (or simply "receivers"), or "remote" devices or units, to name just a few. Other devices, such as personal computers, have also been used in or incorporated into in vivo and in vitro monitoring systems.

[0104] 1. General structure of an analyte sensor system

[0105] A. Exemplary in vivo analyte monitoring system

[0106] Before further describing the analyte sensors and their components in detail, an overview of suitable in vivo analyte sensor constructions and sensor systems using the analyte sensors will be provided to enable a better understanding of embodiments of the present disclosure.

[0107] Figure 1A This is a conceptual diagram illustrating an example implementation of an analyte monitoring system 100, which includes a sensor applicator 150, a sensor control device 102, and a reader device 120. Here, the sensor applicator 150 is used to deliver the sensor control device 102 to a monitoring location on the user's skin, wherein the sensor 104 is held in place for a period of time by an adhesive patch 105. The sensor control device 102 is further described in... Figure 2B and 2CThe device can communicate with the reader device 120 via communication path 140 using wired or wireless technologies. Examples of wireless solutions include Bluetooth, Bluetooth Low Energy (BLE, BTLE, Bluetooth SMART, etc.), Near Field Communication (NFC), etc. Users can monitor applications installed in the memory on the reader device 120 using screen 122 and input 121, and the device battery can be recharged via power port 123. Further details of the reader device 120 are described below. Figure 2A Description. Reader device 120 is capable of communicating with local computer system 170 via communication path 141 using wired or wireless technology. Local computer system 170 may include one or more of the following: laptop, desktop, tablet, tablet phone, smartphone, set-top box, video game console, or other computing device, and wireless communication may include any of a number of feasible wireless networking schemes, including Bluetooth, Bluetooth Low Energy (BTLE), Wi-Fi, or others. Using the wired or wireless technology described above, local computer system 170 can communicate with network 190 via communication path 143, similar to how reader device 120 communicates with network 190 via communication path 142. Network 190 can be any of a variety of networks, such as private and public networks, local area networks (LANs) or wide area networks (WANs). Trusted computer system 180 may include a server and be capable of providing authentication services and secure data storage, and can communicate with network 190 via communication path 144 using wired or wireless technology.

[0108] Figure 1B The operating environment of the analyte monitoring system 100a is described, embodying the techniques described herein. The analyte monitoring system 100a may include component systems designed to provide monitoring of parameters of a human or animal body, such as analyte levels, or to provide other operations based on various component configurations. As illustrated herein, the system may include a low-power analyte sensor 110, or simply "sensor," worn or attached to the body of a user, to collect information from the user or body. As illustrated herein, the analyte sensor 110 may be a sealed, disposable device with a predetermined effective lifespan (e.g., 1 day, 14 days, 30 days, etc.). The sensor 110 may be applied to the skin of the user's body and remain attached for the duration of its lifespan, or may be designed to be selectively removed and remain functional upon reapplication. The low-power analyte monitoring system 100a may also include a data readout device 120 or a multi-target data receiver 130, configured as described herein to facilitate the acquisition and transmission of data (including analyte data) from the analyte sensor 110.

[0109] As illustrated herein, the analyte monitoring system 100a may include software or firmware libraries or applications that are provided to third parties, for example, via a remote application server 1150 or a storefront server 160, and incorporated into multi-target hardware devices 130, such as mobile phones, tablets, personal computing devices, or other similar computing devices, capable of communicating with the analyte sensor 110 via a communication link. The multi-target hardware may also include embedding devices, including but not limited to insulin pumps or insulin pens, having an embedding library configured to communicate with the analyte sensor 110. Although the example embodiments of the analyte monitoring system 100a only include one implementation of each example device, this disclosure contemplates that the analyte monitoring system 100a incorporates multiple components interacting throughout the system. For example, but not limited to, as illustrated herein, the data reading device 120 and / or the multi-target data receiving device 130 may include multiple devices. As illustrated herein, the multiple data receiving devices 130 may communicate directly with the sensor 110 as described herein. Additionally or alternatively, the data receiving device 130 may communicate with the second data receiving device 130 to provide analyte data or visualization or analysis of the data for a second display to a user or other authorized participant.

[0110] Figure 1CA diagram illustrating an exemplary sensing system capable of incorporating the analyte sensor of this disclosure is shown. As shown, the sensing system 100 includes a sensor control device 102 and a reader device 120 configured to communicate with each other via a local communication path or link 140 (which can be wired or wireless, one-way or two-way, and encrypted or unencrypted). The reader device 120 can serve as an output medium for observing analyte concentrations determined by the sensor 104 or its associated processor and for providing prompts or notifications, and, according to some embodiments, allows input from one or more users. The reader device 120 can be a multi-purpose smartphone or a dedicated electronic reader device. Although only one reader device 120 is shown, multiple reader devices 120 can exist in some cases. The reader device 120 can also communicate with a remote terminal 90170 and / or a trusted computer system 90180 via communication paths / links 90141 and / or 90142 (which can also be wired or wireless, one-way or two-way, and encrypted or unencrypted). The reader device 120 can also, or alternatively, communicate with a network 1500 (e.g., a mobile phone network, the Internet, or a cloud server) via a communication path / link 151. The network 1500 can further be communicatively coupled to a remote terminal 90170 via a communication path / link 152 and / or to a trusted computer system 90180 via a communication path / link 153. Alternatively, the sensor 104 can communicate directly with the remote terminal 90170 and / or the trusted computer system 90180 without the intermediary reader device 120. For example, but not limited to, according to some embodiments, the sensor 104 can communicate directly with the remote terminal 90170 and / or the trusted computer system 90180 via a communication link to the network 1500, as described in US Patent Application Publication 2011 / 0213225, which is incorporated herein by reference in its entirety. For each communication path or link, any suitable electronic communication scheme can be used, such as Near Field Communication (NFC), Radio Frequency Identification (RFID), Bluetooth® or Bluetooth® Low Energy, WiFi, etc. According to some embodiments, the remote terminal 90170 and / or the trusted computer system 90180 can be accessible to individuals other than the primary user who are interested in the user's analytics level. The reader device 120 can include a display 122 and optional input components 121. According to some embodiments, the display 122 can include a touchscreen interface.

[0111] The sensor control device 102 includes a sensor housing 103 capable of housing circuitry and a power supply for operating the sensor 104. Optionally, the power supply and / or operating circuitry can be omitted. A processor (not shown) is communicatively coupled to the sensor 104, wherein the processor is physically located within the sensor housing 103 or the reader device 120. According to some embodiments, the sensor 104 protrudes from the underside of the sensor housing 103 and extends through an adhesive layer 105 suitable for attaching the sensor housing 103 to a tissue surface such as skin.

[0112] Sensor 104 is adapted for at least partial insertion into the dermis or subcutaneous layer of a relevant tissue, such as skin. Sensor 104 may include a sensor tail of sufficient length for insertion to a desired depth in a given tissue. The sensor tail may include at least one working electrode. In some configurations, the sensor tail may include an active region for detecting an analyte. A counter electrode may be present in combination with at least one working electrode. Specific electrode configurations on the sensor tail are described in more detail below.

[0113] The active region can be configured to detect a specific analyte. In some embodiments, the active region of the sensor disclosed herein is configured to detect ketones. In some embodiments, the active region can be configured to detect two or more analytes. In some embodiments, additional analytes detected by the sensor of this disclosure include any analyte that is imbalanced with ketones. For example, but not limited to, the analyte sensor of this disclosure can detect ketones and additional analytes such as creatinine, oxygen, glucose, and / or lactate. In some embodiments, the additional analyte is glucose.

[0114] In some embodiments of this disclosure, one or more analytes can be monitored in any relevant biological fluid, such as skin fluid, interstitial fluid, plasma, blood, lymph, synovial fluid, cerebrospinal fluid, saliva, bronchoalveolar lavage fluid, amniotic fluid, etc. In some embodiments, the analyte sensor of this disclosure is adaptable to test skin fluid or interstitial fluid to determine the concentration of one or more analytes in vivo. In some embodiments, the biological fluid is interstitial fluid.

[0115] Still refer to Figure 1CSensor 104 can automatically transmit data to reader device 120. For example, but not limited to, it can automatically and periodically communicate analyte concentration data (i.e., glucose and / or ketone concentrations), such as at a certain frequency or after a certain time interval, wherein the data is stored in memory until transmission (e.g., every minute, five minutes, or other predetermined time intervals). In some embodiments, sensor 104 can communicate with reader device 120 in a non-automatic manner and without following a set schedule. For example, but not limited to, data can be communicated from sensor 104 using RFID technology when the sensor electronics enter the communication range of reader device 120. Data can remain stored in the memory of sensor 104 until communication reaches reader device 120. Thus, the user does not need to be in close proximity to reader device 120 at all times, but can upload data at convenient times. In some embodiments, a combination of automatic and non-automatic data transfer can be implemented. For example, but not limited to, data transfer can continue automatically until reader device 120 is no longer within the communication range of sensor 104.

[0116] The introducer can be briefly present to facilitate the introduction of sensor 104 into the tissue. In some exemplary embodiments, the introducer can include a needle or similar tip. Those skilled in the art will readily appreciate that other types of introducers, such as sheaths or blades, can be present in alternative embodiments. More specifically, the needle or other introducer can be briefly located near sensor 104 before tissue insertion and then withdrawn. In its presence, the needle or other introducer can facilitate the insertion of sensor 104 into the tissue by opening an inlet / outlet path that allows sensor 104 to follow. For example, but not limited to, according to one or more embodiments, the needle can facilitate epidermal penetration as a pathway to the dermis, allowing sensor 104 implantation. After opening the inlet / outlet path, the needle or other introducer can be withdrawn without posing a risk of sharpness. In some embodiments, a suitable needle can be solid or hollow, beveled or non-beveled, and / or have a circular or non-circular cross-section. In a more specific embodiment, a suitable needle can be comparable to an acupuncture needle in cross-sectional diameter and / or tip design, having a cross-sectional diameter of approximately 250 micrometers. However, suitable needles can have larger or smaller cross-sectional diameters if required for certain specific applications.

[0117] In some embodiments, the tip of the needle (when present) is angled above the end of the sensor 104, thereby allowing the needle to penetrate the tissue first and open the entry / exit path for the sensor 104. In some embodiments, the sensor 104 may be located in the lumen or groove of the needle, where the needle similarly opens the entry / exit path for the sensor 104. In either case, the needle is subsequently withdrawn after facilitating sensor insertion.

[0118] B. Exemplary Reader Device

[0119] Figure 2A This is a block diagram illustrating an exemplary implementation of a reader device configured as a smartphone. Here, the reader device 120 may include a display 122, an input component 121, and a processing core 206, which includes a communication processor 222 connected to a memory 223 and an application processor 224 connected to a memory 225. It may also include a separate memory 230, an RF transceiver 228 with an antenna 229, and a power supply 226 with a power management module 238. It may further include a multi-function transceiver 232 capable of communicating with the antenna 234 via Wi-Fi, NFC, Bluetooth, BTLE, and GPS. As those skilled in the art will understand, these components are electrically and communicatively connected in a manner that enables the device to function.

[0120] C. Construction of a demonstrative data receiving device

[0121] For illustrative purposes and not for limitation, such as Figure 2B The illustrated example is a data receiving device 120 used in the subject matter of this disclosure. It can include the data receiving device 120 and an associated multi-target data receiving device 130, including components related to the discussion of the analyte sensor 110, their operation, and additional components. In specific embodiments, the data receiving device 120 and the multi-target data receiving device 130 can be or include components supplied by third parties and are not necessarily limited to devices manufactured by the same manufacturer as the sensor 110.

[0122] like Figure 2B As shown, the data receiving device 120 includes an ASIC 4000, comprising a microcontroller 4010, a memory 4020, and a storage 4030, and is communicatively connected to a communication module 4040. Power to the components of the data receiving device 120 can be delivered via a power module 4050, which, as illustrated herein, may include a rechargeable battery. The data receiving device 120 may also include a display 4070 for facilitating the analysis of analyte data received from the analyte sensor 110 or other devices (e.g., user device 1140 or remote application server 1150). The data receiving device 120 may include separate user interface components (e.g., a physical key, a light sensor, a microphone, etc.).

[0123] Communication module 4040 may include BLE module 4041 and NFC module 4042. Data receiving device 120 may be configured to wirelessly connect to analyte sensor 110 and transmit commands to and receive data from analyte sensor 110. As illustrated herein, referring to analyte sensor 110 as described herein, data receiving device 120 may be configured to operate as an NFC scanner and BLE endpoint via a specific module of communication module 4040 (e.g., BLE module 4042 or NFC module 4043). For example, data receiving device 120 may issue commands to analyte sensor 110 using a first module of communication module 4040 (e.g., a command to start sensor data broadcast mode; a pairing command to identify data receiving device 120), and receive and transmit data to analyte sensor 110 using a second module of communication module 4040. Data receiving device 120 may be configured to communicate with user device 1140 via Universal Serial Bus (USB) module 4045 of communication module 4040.

[0124] As another example, communication module 4040 may include, for example, cellular radio module 4044. Cellular radio module 4044 may include one or more radio transceivers for communicating over a broadband cellular network, including but not limited to third-generation (3G), fourth-generation (4G), and fifth-generation (5G) networks. Additionally, communication module 4040 of data receiving device 120 may include Wi-Fi radio module 4043 for communicating over a wireless local area network according to one or more IEEE 802.11 standards (e.g., 802.11a, 802.11b, 802.11g, 802.11n (i.e., Wi-Fi 4), 802.11ac (i.e., Wi-Fi 5), 802.11ax (i.e., Wi-Fi 6)). Using cellular radio module 4044 or Wi-Fi radio module 4043, data receiving device 120 may communicate with remote application server 1150 to receive analyte data or provide updates or input received from a user (e.g., through one or more user interfaces). Although not explicitly stated, the communication module 5040 of the analyzer sensor 110 may similarly include a cellular radio module or a Wi-Fi radio module.

[0125] As illustrated herein, the onboard storage 4030 of the data receiving device 120 can store analyte data received from the analyte sensor 110. Furthermore, the data receiving device 120, the multi-target data receiving device 130, or the user device 1140 can be configured to communicate with a remote application server 1150 via a wide area network. As illustrated herein, the analyte sensor 110 can provide data to the data receiving device 120 or the multi-target data receiving device 130. The data receiving device 120 can transmit data to the user computing device 1140. The user computing device 1140 (or the multi-target data receiving device 130) can then transmit the data to the remote application server 1150 for processing and analysis.

[0126] As illustrated herein, the data receiving device 120 may also include sensing hardware 4060, which is similar to or extends from the sensing hardware 5060 of the analyte sensor 110. In specific embodiments, the data receiving device 120 may be configured to operate in coordination with the analyte sensor 110 and based on analyte data received from the analyte sensor 110. For example, where the analyte sensor 110 is a glucose sensor, the data receiving device 120 may be or include an insulin pump or insulin pen. Accordingly, a compatible device 130 may adjust the insulin dose for the user based on the glucose value received from the analyte sensor.

[0127] D. Exemplary sensor control device

[0128] Figure 2C and 2D This is a block diagram illustrating an exemplary embodiment of a sensor control device 102, which has an analyte sensor 104 and sensor electronics 160 (including analyte monitoring circuitry) capable of dedicating most of its processing power to making the final result data suitable for display to a user. Figure 2C The image describes a single semiconductor chip 161, which can be a custom application-specific integrated circuit (ASIC). The ASIC 161 shows several high-level functional units, including an analog front-end (AFE) 162, power management (or control) circuitry 164, a processor 166, and communication circuitry 168 (which can function as a transmitter, receiver, transceiver, passive circuitry, or other means depending on the communication scheme). In this embodiment, both the AFE 162 and the processor 166 serve as analyte monitoring circuitry, but in other embodiments, one of these circuits can perform analyte monitoring functionality. The processor 166 can include one or more processors, microprocessors, controllers, and / or microcontrollers, each of which can be a discrete chip or distributed across many different chips (and portions thereof).

[0129] Memory 163 is also included in ASIC 161 and can be shared by various functional units present in ASIC 161, or distributed among two or more of them. Memory 163 can also be a separate chip. Memory 163 can be volatile and / or non-volatile memory. In this embodiment, ASIC 161 is connected to power supply 170, which can be a button battery, etc. AFE 162 is interfaced with in vivo analyte sensor 104 and receives measurement data from it and outputs the data digitally to processor 166, which in turn processes the data to obtain final results such as glucose discrete and trend values. This data can then be provided to communication circuitry 168 for transmission via antenna 171 to reader device 120 (not shown), where, for example, the resident software application requires minimal further processing to display the data.

[0130] Figure 2D similar Figure 2C The system comprises two discrete semiconductor chips, 162 and 174, which can be packaged together or separately. Here, AFE 162 resides on ASIC 161. On chip 174, processor 166 is integrated with power management circuitry 164 and communication circuitry 168. AFE 162 includes memory 163, while chip 174 includes memory 165, which can be separate or distributed within it. In one example implementation, AFE 162 is combined with power management circuitry 164 and processor 166 on one chip, while communication circuitry 168 is on a separate chip. In yet another example implementation, AFE 162 and communication circuitry 168 are both on one chip, while processor 166 and power management circuitry 164 are on yet another chip. It should be noted that other chip combinations are possible, including three or more chips, each responsible for its own separate functional description or sharing one or more functions for fail-safe redundancy.

[0131] For illustrative purposes and not for limitation, reference is made to exemplary embodiments of the analyte sensor 110 used in the subject matter of this disclosure, such as... Figure 2E As shown. Figure 2E A block diagram of an example analyzer sensor 110 according to an exemplary implementation is shown, which is compatible with the security architecture and communication scheme described herein.

[0132] As illustrated herein, the analyte sensor 110 may include an application-specific integrated circuit ("ASIC") 5000 that is communicatively connected to the communication module 5040. The ASIC 5000 may include a microcontroller core 5010, onboard memory 5020, and storage memory 5030. Storage memory 5030 may store data used in an authentication and cryptographic security architecture. Storage memory 5030 may store programming instructions for the sensor 110. As illustrated herein, some communication chips may be embedded in the ASIC 5000 (e.g., an NFC transceiver 5025). The ASIC 5000 may receive power from a power module 5050, such as an onboard battery, or from NFC pulses. The storage memory 5030 of the ASIC 5000 may be programmed to include information such as identification information of the sensor 110 for authentication and tracking purposes. Storage memory 5030 may also be programmed with configuration or calibration parameters for use with the sensor 110 and its various components. The storage memory 5030 may include rewritable or one-time programmable (OTP) memory. The storage memory 5030 may be updated using the techniques described herein to extend the usefulness of the sensor 110.

[0133] As illustrated herein, the communication module 5040 of sensor 110 may be or include one or more modules to support communication between analyte sensor 110 and other devices of analyte monitoring system 100. As an example only and not a limitation, the communication module 5040 may include a Bluetooth Low Energy ("BLE") module 5041. As used herein, Bluetooth Low Energy ("BLE") refers to a short-range communication scheme optimized to simplify pairing Bluetooth devices for end users. The communication module 5040 can transmit and receive data and commands by interacting with a communication module that performs similar functions to data receiving device 120 or user device 1140. The communication module 5040 may include additional or alternative chips for similar short-range communication schemes, such as personal area networks according to IEEE 802.15 or IEEE 802.11 standards, infrared communication according to the Infrared Data Association (IrDA) standard, etc.

[0134] To perform its function, sensor 110 may also include suitable sensing hardware 5060 appropriate for its function. As illustrated herein, sensing hardware 5060 may include an analyte sensor that is positioned percutaneously or subcutaneously in contact with the subject's bodily fluids. The analyte sensor can generate sensor data containing values ​​corresponding to the levels of one or more analytes in the bodily fluids.

[0135] E. Demonstration assembly process of sensor control device

[0136] Users can obtain components of the sensor control device 102 in multiple packages, which require final assembly by the user before delivery to the appropriate user location. Figures 3A-3D An example implementation of the sensor control device 102 assembly process performed by a user includes preparing separate components and then connecting the components to prepare the sensor for delivery. Figure 3E-3F An example implementation describes the delivery of the sensor control device 102 to the appropriate user location by selecting an appropriate delivery location and applying the device 102 to that location.

[0137] Figure 3A This is a near-end perspective view illustrating an example implementation of a user preparing container 810, configured here as a tray (although other packaging could be used), for the assembly process. The user can perform this preparation by removing the lid 812 from the tray 810 to expose the platform 808, for example, by peeling off the non-attached portion of the lid 812 from the tray 810, thus removing the attached portion of the lid 812. In various embodiments, the removal of the lid 812 can be appropriate, provided that the platform 808 is sufficiently exposed within the tray 810. The lid 812 can then be set aside.

[0138] Figure 3B This is a side view illustrating an example embodiment where a user prepares the applicator device 150 for assembly. The applicator device 150 can be provided in a sterile package sealed by a cap 708. Preparation of the applicator device 150 can include removing the outer casing 702 from the cap 708 to expose the sheath 704. Figure 3C This allows the following: unscrewing (or otherwise removing) the cover 708 from the outer casing 702. The cover 708 can then be set aside.

[0139] Figure 3C This is a near-end perspective view illustrating an exemplary implementation where the user inserts the applicator device 150 into the tray 810 during assembly. Initially, the user is able to insert the sheath 704 into the platform 808 within the tray 810 after aligning the housing orientation feature 1302 (or slot or recess) and the tray orientation feature 924 (support or positioning recess). Inserting the sheath 704 into the platform 808 temporarily releases the sheath 704 relative to the housing 702 and temporarily releases the platform 808 relative to the tray 810. At this stage, removing the applicator device 150 from the tray 810 will result in the same state as before the initial insertion of the applicator device 150 into the tray 810 (i.e., the process can be reversed or canceled at this point and then repeated without consequence).

[0140] The sheath 704 is able to maintain its position relative to the housing 702 within the platform 808, while the housing 702 is advanced distally, engaging with the platform 808 and thus advancing the platform 808 distally relative to the tray 810. This step releases and folds the platform 808 within the tray 810. The sheath 704 is able to contact and disengage a locking feature (not shown) in the tray 810, releasing the sheath 704 relative to the housing 702 and preventing the sheath 704 from moving (relatively), while the housing 702 continues to advance the platform 808 distally. At the endpoint of the advancement of the housing 702 and the platform 808, the sheath 704 is permanently released relative to the housing 702. At the distal endpoint of the advancement of the housing 702, the tip and sensor (not shown) in the tray 810 are able to engage with the electronic housing (not shown) in the housing 702. The operation and interaction of the applicator device 150 and the tray 810 are further described below.

[0141] Figure 3D This is a proximal perspective view illustrating an exemplary embodiment of a user removing the applicator device 150 from the tray 810 during assembly. The user can remove the applicator 150 from the tray 810 by pushing the housing 702 proximally relative to the tray 810 or by other movements having the same end effect of disengaging the applicator 150 and the tray 810. When the applicator device 150 is removed, the sensor control device 102 (not shown) therein is fully assembled (tip, sensor, electronics) and in the delivery position.

[0142] Figure 3E This is a proximal perspective view illustrating an exemplary embodiment of the patient application sensor control device 102, wherein the applicator device 150 is used to target a skin area, such as the upper abdomen or other suitable location. The housing 702 is advanced distally, within which the sheath 704 is folded, and the sensor is used at the target location, thereby adhering the adhesive layer on the underside of the sensor control device 102 to the skin. The tip automatically retracts when the housing 702 is fully advanced, while the sensor (not shown) remains in position to measure analyte levels.

[0143] Figure 3F This is a proximal perspective view illustrating an example implementation of the sensor control device 102 at the patient application site. The user can then remove the applicator 150 from the application site.

[0144] Compared with existing technical systems, the system referenced in this paper... Figures 3A-3FThe system 100, as described in other sections, can reduce or eliminate the chance of accidental breakage, permanent deformation, or incorrect assembly of the applicator components. Because the applicator housing 702 directly engages the platform 808 when the sheath 704 is released, rather than being indirectly connected via the sheath 704, the relative angularity between the sheath 704 and the housing 702 does not cause breakage or permanent deformation of the arm or other components. The possibility of relatively high forces (as in conventional devices) during assembly is reduced, which in turn reduces the chance of unsuccessful user assembly.

[0145] F. Exemplary sensor applicator device

[0146] Figure 4A This is a side view illustrating an example implementation of the applicator device 150 connected to the nut 708. This is an example of how the applicator 150 is transported to and received by the user, and subsequently assembled by the user with the sensor. Figure 4B It is a side perspective view depicting the applicator 150 and cover 708 after separation. Figure 4C This is a perspective view illustrating an exemplary embodiment of the distal end of the applicator device 150, wherein the electronics housing 706 and adhesive patch 105 are removed from their positions within the sensor carrier 710 of the sheath 704 when the cover 708 is in place.

[0147] For illustrative purposes only and not for limiting reference. Figure 4D -G, The applicator device 20150 can be provided to the user as a single integrated assembly. Figure 4D and 4E Top and bottom perspective views of the applicator device 20150 are provided respectively. Figure 4F An exploded view of the applicator device 20150 is provided. Figure 4GA side sectional view is provided. The perspective view illustrates how the applicator 20150 is transported to and received by the user. Exploded and sectional views illustrate the components of the applicator device 20150. The applicator device 20150 may include a housing 20702, a gasket 20701, a sheath 20704, a tip carrier 201102, a spring 205612, a sensor carrier 20710 (also referred to as a "disc carrier"), a tip hub 205014, a sensor control device (also referred to as a "disc") 20102, an adhesive patch 20105, a desiccant 20502, a cap 20708, a serial number mark 20709, and a tamper evidence feature 20712. As received by the user, only the housing 20702, cap 20708, tamper evidence feature 20712, and mark 20709 are visible. The tampering evidence feature 20712 can be, for example, an adhesive label attached to the outer casing 20702 and the cover 20708 respectively, and the tampering evidence feature 20712 can indicate to the user that the outer casing 20702 and the cover 20708 have been detached beforehand by being destroyed, for example, irreparably destroyed, upon detachment. These features are described in more detail below.

[0148] G. Exemplary tray and sensor module assembly

[0149] Figure 5 This is a near-end perspective view illustrating an example implementation of a tray 810 having a sterilization cap 812 removably connected thereto, which may represent how the package is transported to and received by the user, and subsequently assembled.

[0150] Figure 6A This is a near-end perspective sectional view depicting the sensor delivery assembly in tray 810. Platform 808 is slidably connected within tray 810. Desiccant 502 is stationary relative to tray 810. Sensor module 504 is housed within tray 810.

[0151] Figure 6B This is a near-end perspective view, describing sensor module 504 in more detail. Here, the retaining arm extension 1834 of platform 808 releasably secures sensor module 504 in place. Module 2200 is connected to connector 2300, tip module 2500, and sensor (not shown), allowing them to be removed together with sensor module 504 during assembly.

[0152] H. Exemplary applicator and sensor control device for one-piece construction

[0153] Please refer to the following briefly: Figure 1A and 3A-3F, for two-piece construction systems, tray 810 and sensor applicator 150 are provided to the user as separate packages, requiring the user to open the individual packages and ultimately assemble the system. In some applications, the discrete sealed packaging allows tray 810 and sensor applicator 150 to be sterilized in separate sterilization processes that are unique to the contents of each package and otherwise incompatible with the contents of the other package. More specifically, tray 810, which includes sensor module 504 comprising module 2200, connector 2300, tip module 2500, and sensor (not shown), can be sterilized by radiation, such as electron beam (or "e-beam") radiation. Suitable radiation sterilization processes include, but are not limited to, electron beam (e-beam) radiation, gamma-ray radiation, X-ray radiation, or any combination thereof. However, radiation sterilization can damage the electronic components arranged within the electronic housing of sensor control device 102. Therefore, if the sensor applicator 150 (which contains the electronic housing of the sensor control device 102) requires sterilization, it can be sterilized by other methods, such as gaseous chemical sterilization with ethylene oxide, for example. However, gaseous chemical sterilization can damage the enzymes or other chemical and biological agents contained on the sensor 110. Due to this sterilization incompatibility, the tray 810 and the sensor applicator 150 are generally sterilized in separate sterilization processes and subsequently packaged separately, requiring the user to ultimately assemble the components for use.

[0154] Figure 7A and 7B These are exploded top and bottom views of the sensor control device 3702, according to one or more embodiments. The housing 3706 and support 3708 operate as opposing clamshells, enclosing or substantially enclosing various electronic components of the sensor control device 3702. As illustrated, the sensor control device 3702 may include a printed circuit board assembly (PCBA) 3802, which includes a printed circuit board (PCB) 3804 having multiple electronic modules 3806 connected thereto. Examples of electronic modules 3806 include, but are not limited to, resistors, transistors, capacitors, sensors, diodes, and switches. In conventional sensor control devices, the PCB assembly is typically stacked on only one side of the PCB. In contrast, the PCB assembly 3806 in the sensor control device 3702 can be distributed across both sides of the PCB 3804 (i.e., the upper and lower surfaces).

[0155] In addition to the electronic module 3806, PCBA 3802 may also include a data processing unit 3808 mounted on PCB 3804. The data processing unit 3808 may include, for example, an application-specific integrated circuit (ASIC) configured to perform one or more functions or routines related to the operation of the sensor control device 3702. More specifically, the data processing unit 3808 may be configured to perform data processing functions, which may include, but are not limited to, filtering and encoding of data signals, each corresponding to a user's sampling analysis level. The data processing unit 3808 may also include an antenna or otherwise communicate with an antenna for communication with the reader device 106. Figure 1A ).

[0156] A battery aperture 3810 can be defined within a PCB 3804, and its dimensions receive a battery 3812 and provide a base, the battery being configured to power the sensor control device 3702. Axial battery contacts 3814a and radial battery contacts 3814b can be connected to the PCB 3804 and extend into the battery aperture 3810 to facilitate power transfer from the battery 3812 to the PCB 3804. As their names suggest, the axial battery contact 3814a can be configured to provide axial contacts for the battery 3812, while the radial battery contact 3814b can provide radial contacts for the battery 3812. Positioning the battery 3812 within the battery aperture 3810 with battery contacts 3814a, b helps reduce the height H of the sensor control device 3702, allowing the PCB 3804 to be centrally positioned with its components distributed on both sides (i.e., the upper and lower surfaces). This also helps facilitate the chamber 3718 provided on the electronics housing 3704.

[0157] Sensor 3716 may be centrally positioned relative to PCB 3804 and includes a tail 3816, a marker 3818, and a neck 3820 interconnecting the tail 3816 and the marker 3818. Tail 3816 may be configured to extend through a central aperture 3720 of bracket 3708 for transdermal reception under the user's skin. Furthermore, tail 3816 may contain enzymes or other chemicals to aid in analyte monitoring.

[0158] The marker 3818 may include a generally planar surface having one or more sensor contacts 3822 (shown on) arranged thereon. Figure 7B (Three of them). Sensor contact 3822 can be configured with one or more corresponding circuit contacts 3824 provided on PCB 3804 (shown in Figure 7AThe three contacts are aligned and engaged. In some embodiments, sensor contact 3822 may comprise carbon-impregnated polymer printed or otherwise digitally applied to marker 3818. Prior sensor control devices generally include connectors made of silicone rubber encapsulating one or more suitable carbon-impregnated polymer modules, which act as conductive contacts between the sensor and the PCB. In contrast, the currently disclosed sensor contact 3822 provides a direct connection between sensor 3716 and PCB 3804, eliminating the need for prior art connectors and advantageously reducing height H. Furthermore, eliminating the need for suitable carbon-impregnated polymer modules eliminates significant circuit impedance and thus improves circuit conductivity.

[0159] The sensor control device 3702 may also include a suitable element 3826, which can be arranged to intervene in the inner surface of the marker 3818 and the housing 3706. More specifically, when the housing 3706 and the bracket 3708 are assembled together, the suitable element 3826 may be configured to provide a passive biasing load on the marker 3818, which forces the sensor contact 3822 to be continuously connected to the corresponding circuit contact 3824. In the described embodiment, the suitable element 3826 is an elastomeric O-ring, but may alternatively include any other type of biasing device or mechanism, such as a compression spring, without departing from the scope of this disclosure.

[0160] The sensor control device 3702 may also include one or more electromagnetic shields, shown as a first shield 3828a and a second shield. The housing 3706 may provide or otherwise define the first timing container 3830a. Figure 7B ) and the second timing container 3830b ( Figure 7B ), while bracket 3708 can provide or otherwise define the first timing column 3832a ( Figure 7A ) and the second timing column 3832b ( Figure 7A Pairing the first and second timing containers 3830a, b with the first and second timing columns 3832a, b respectively will properly align the housing 3706 with the bracket 3708.

[0161] Special reference Figure 7A The inner surface of the bracket 3708 may provide or otherwise define a plurality of pockets or recesses configured to accommodate various component portions of the sensor control device 3702 when the housing 3706 mates with the bracket 3708. For example, the inner surface of the bracket 3708 may define a battery positioner 3834 configured to accommodate a portion of the battery 3812 when the sensor control device 3702 is assembled. An adjacent contact pocket 3836 may be configured to accommodate a portion of an axial contact 3814a.

[0162] Furthermore, multiple module pockets 3838 can be defined in the inner surface of the bracket 3708 to accommodate various electronic modules 3806 arranged at the bottom of the PCB 3804. Additionally, a shield positioner 3840 can be defined in the inner surface of the bracket 3708 to accommodate at least a portion of the second shield 3828b during the assembly of the sensor control device 3702. The battery positioner 3834, contact pocket 3836, module pockets 3838, and shield positioner 3840 all extend shortly into the inner surface of the bracket 3708, and as a result, the overall height H of the sensor control device 3702 can be reduced relative to the preceding sensor control device. The module pockets 3838 can also help minimize the diameter of the PCB 3804 by allowing PCB assemblies to be arranged on both sides (i.e., the upper and lower surfaces).

[0163] Still refer to Figure 7A The support 3708 may also include a plurality of carrier gripping features 3842 (two shown) defined around the outer periphery of the support 3708. The carrier gripping features 3842 are axially offset from the bottom 3844 of the support 3708, where a transfer adhesive (not shown) can be applied during assembly. In contrast to prior sensor controls that generally include a tapered carrier gripping feature intersecting the bottom of the support, the carrier gripping features 3842 of this disclosure are offset from the plane in which the transfer adhesive is applied (i.e., the bottom 3844). This can prove advantageous, as it helps ensure that the delivery system does not accidentally adhere the transfer adhesive during assembly. Furthermore, the carrier gripping features 3842 of this disclosure eliminate the need for toothed transfer adhesive, which simplifies the manufacture of the transfer adhesive and eliminates the need for precise control of the transfer adhesive relative to the support 3708. This also increases the bonding area and, consequently, the bonding strength.

[0164] Reference Figure 7B The bottom 3844 of the support 3708 may be provided with or otherwise defined with a plurality of grooves 3846, which may be defined at or near the outer periphery of the support 3708 and equidistant from each other. Transfer adhesive (not shown) may be attached to the bottom 3844, and the grooves 3846 may be configured to facilitate the transfer of moisture from the sensor control device 3702 to the area around the support 3708 during use. In some embodiments, the spacing of the grooves 3846 may intersect a module pocket 3838 defined on the opposite side (inner surface) of the support 3708. Figure 7A It will be recognized that the alternating positions of the groove 3846 and the module pocket 3838 ensure that the opposing features on both sides of the bracket 3708 do not extend into each other. This helps to maximize the use of material in the bracket 3708 and thereby helps to maintain the minimum height H of the sensor control device 3702. The module pocket 3838 also significantly reduces the mold sink and improves the flatness of the bottom 3844 where the transfer adhesive is bonded.

[0165] Still refer to Figure 7B The inner surface of the housing 3706 may also provide or otherwise define a plurality of pockets or recesses configured to accommodate various component portions of the sensor control device 3702 when the housing 3706 is mated with the bracket 3708. For example, the inner surface of the housing 3706 may define an opposing battery locator 3848, which may be positioned relative to the battery locator 3834 of the bracket 3708. Figure 7A A portion of the battery 3812 is arranged and configured to accommodate the sensor control unit 3702 during assembly. Conversely, the battery locator 3848 extends shortly into the inner surface of the housing 3706, which helps to reduce the overall height H of the sensor control unit 3702.

[0166] A tip and sensor positioner 3852 may also be provided or otherwise defined on the inner surface of housing 3706. The tip and sensor positioner 3852 may be configured to receive both a portion of the tip (not shown) and the sensor 3716. Furthermore, the tip and sensor positioner 3852 may be configured to align with a corresponding tip and sensor positioner 2054 provided on the inner surface of bracket 3708. Figure 7A ) and / or paired with it.

[0167] According to embodiments of this disclosure, Figures 8A to 8C This describes alternative sensor assembly / electronic device assembly connection methods. As shown, sensor assembly 14702 includes sensor 14704, connector bracket 14706, and tip 14708. Notably, a recess or container 14710 may be defined at the bottom of the electronic device assembly 14712 bracket and provide a location in which sensor assembly 14702 can be received and connected to electronic device assembly 14712, thereby fully assembling the sensor control device. The profile of sensor assembly 14702 may match or be shaped in a complementary manner to container 14710, which includes an elastomeric sealing element 14714 (including a conductive material that connects to the circuit board and aligns with the electrical contacts of sensor 14704). Thus, when sensor assembly 14702 is engaged or attached to electronic device assembly 14712 by driving sensor assembly 14702 into the integrally formed recess 14710 in electronic device assembly 14712, a... Figure 8C The described body device 14714. This embodiment provides an integrated connector for sensor assembly 14702 in electronic device assembly 14712.

[0168] Additional information regarding sensor components is provided in US Publication No. 2013 / 0150691 and US Publication No. 2021 / 0204841, each of which is incorporated herein by reference in its entirety.

[0169] According to embodiments of this disclosure, the sensor control device 102 can be modified to provide a one-piece construction that can withstand sterilization techniques specifically designed for one-piece sensor control devices. This one-piece construction allows the sensor applicator 150 and sensor control device 102 to be transported to the user in a single sealed package, eliminating the need for any final user assembly step. Instead, the user only needs to open one package and subsequently deliver the sensor control device 102 to the target monitoring location. The one-piece system construction described herein can prove advantageous in eliminating component parts, various manufacturing process steps, and user assembly steps. As a result, packaging and waste are reduced, and the possibility of user error or system contamination is mitigated.

[0170] Figure 9A and 9B These are side and cross-sectional side views, illustrating an exemplary embodiment of a sensor applicator 5102 with an applicator cover 210 connected thereto. More specifically, Figure 9A Describes how the sensor applicator 5102 might be transported to and received by the user, and Figure 9B The sensor control device 4402 arranged within the sensor applicator 5102 is described. Accordingly, the fully assembled sensor control device 4402 may be pre-assembled and installed within the sensor applicator 5102 and subsequently delivered to the user, thereby eliminating any additional assembly steps that the user would otherwise have to perform.

[0171] A fully assembled sensor control unit 4402 can be loaded onto a sensor applicator 5102, and an applicator cap 210 can subsequently be connected to the sensor applicator 5102. In some embodiments, the applicator cap 210 may be threaded onto a housing 208 and include a tamper ring 4702. Upon rotation (e.g., unscrewing) of the applicator cap 210 relative to the housing 208, the tamper ring 4702 may shear off and thereby release the applicator cap 210 from the sensor applicator 5102.

[0172] According to this disclosure, when loaded into the sensor applicator 5102, the sensor control device 4402 can undergo gaseous chemical sterilization 4704, which is configured to sterilize the electronics housing 4404 and any other exposed portions of the sensor control device 4402. To achieve this, chemicals can be injected into a sterilization chamber 4706 defined by the sensor applicator 5102 and an interconnected cap 210. In some applications, chemicals can be injected into the sterilization chamber 4706 via one or more vents 4708 defined at the proximal end 610 of the applicator cap 210. Examples of chemicals that can be used for gaseous chemical sterilization 4704 include, but are not limited to, ethylene oxide, evaporated hydrogen peroxide, nitrogen oxides (e.g., nitrous oxide, nitrogen dioxide, etc.), and vapors.

[0173] Because the distal portion of sensor 4410 and tip 4412 are sealed within sensor cover 4416, the chemicals used during the gaseous chemical sterilization process do not interact with the enzymes, chemicals, and biological agents provided on the tail 4524 and other sensor components, such as the membrane coating that regulates the flow of analytes.

[0174] Once the desired sterilization assurance level has been achieved in sterilization chamber 4706, the gaseous solution can be removed and sterilization chamber 4706 can be ventilated. Ventilation can be achieved by a series of vacuum cycles followed by recirculation of gas (e.g., nitrogen) or filtered air through sterilization chamber 4706. Once sterilization chamber 4706 is properly ventilated, vent 4708 can be closed with a seal 4712 (shown in dashed lines).

[0175] In some embodiments, seal 4712 may comprise two or more layers of different materials. The first layer may be made of a synthetic material (e.g., fast-spun high-density polyethylene fiber), such as Tyvek® available from DuPont®. Tyvek® is highly durable and puncture-resistant, and allows vapor permeation. The Tyvek® layer can be applied before and after the gaseous chemical sterilization process, and a foil or other vapor and moisture-resistant layer can be sealed (e.g., heat-sealed) over the Tyvek® layer to prevent contaminants and moisture from entering sterilization chamber 4706. In other embodiments, seal 4712 may comprise a single protective layer applied to applicator cap 210. In these embodiments, the single layer may be gas-permeable to the sterilization process, but also able to block moisture and other harmful elements once the sterilization process is complete.

[0176] With the seal 4712 in place, the applicator cap 210 provides a barrier against external contamination and thereby maintains a sterile environment for the assembled sensor control device 4402 until the user removes (detaches) the applicator cap 210. The applicator cap 210 also creates a dust-free environment during transport and storage, preventing the adhesive patch 4714 from becoming soiled.

[0177] Figure 10A and 10B These are, respectively, an isometric view and a side view of another example of a sensor control device 5002, according to one or more embodiments of this disclosure. The sensor control device 5002 may, in some respects, be comparable to... Figure 1A The sensor control device 5002 is similar to that of the sensor control device 102, and therefore can be best understood by referring to it. Furthermore, the sensor control device 5002 can replace... Figure 1A The sensor control device 102, and therefore can be used with Figure 1A When used in conjunction with the sensor applicator 150, it can deliver the sensor control device 5002 to the target monitoring location on the user's skin.

[0178] However, unlike Figure 1A The sensor control device 102, sensor control device 5002 may comprise a one-piece system construction, which does not require the user to unpack multiple packages and finally assemble the sensor control device 5002 before application. Instead, upon user acquisition, the sensor control device 5002 may be fully assembled and properly located in the sensor applicator 150 ( Figure 1A Inside. To use the sensor control device 5002, the user only needs to open one barrier (e.g., Figure 3B The applicator cover 708 is then used to quickly deliver the sensor control device 5002 to the target monitoring location.

[0179] As described, the sensor control device 5002 includes an electronics housing 5004, which is generally disc-shaped and may have a circular cross-section. However, in other embodiments, the electronics housing 5004 may exhibit other cross-sectional shapes, such as oval or polygonal, without departing from the scope of this disclosure. The electronics housing 5004 may be configured to house or contain various electrical components for operating the sensor control device 5002. In at least one embodiment, an adhesive patch (not shown) may be arranged on the bottom of the electronics housing 5004. The adhesive patch may be similar to... Figure 1A The adhesive patch 105 can help the sensor control device 5002 to adhere to the user's skin.

[0180] As described, the sensor control device 5002 includes an electronic housing 5004, which includes a shell 5006 and a bracket 5008 mating with the shell 5006. The shell 5006 can be secured to the bracket 5008 by various means, such as snap-fit ​​connection, interference fit, acoustic welding, one or more mechanical fasteners (e.g., screws), washers, adhesives, or any combination thereof. In some cases, the shell 5006 can be secured to the bracket 5008 to create a sealed interface therebetween.

[0181] The sensor control device 5002 may also include a sensor 5090 (partially visible) and a tip 5012 (partially visible) for assisting in the percutaneous delivery of the sensor 5090 under the user's skin during application of the sensor control device 5002. As illustrated, corresponding portions of the sensor 5090 and the tip 5012 extend distally from the bottom of the electronics housing 5004 (e.g., a bracket 5008). The tip 5012 may include a tip hub 5014 configured to secure and carry the tip 5012. Figure 10BIdeally, the tip hub 5014 may include or otherwise define a mating element 5016. For connection of the tip 5012 to the sensor control device 5002, the tip 5012 may be axially advanced through the electronics housing 5004 until it reaches the upper surface of the tip hub 5014 engaging the housing 5006, and the mating element 5016 extends distally from the bottom of the support 5008. As the tip 5012 penetrates the electronics housing 5004, the exposed portion of the sensor 5090 may be received within the hollow or recessed (arched) portion of the tip 5012. The remaining portion of the sensor 5090 is arranged inside the electronics housing 5004.

[0182] The sensor control device 5002 may also include a sensor cover 5018, in Figures 10A-10B The sensor cover 5016 is removable from or detached from the electronics housing 5004. At or near the bottom of the support 5008, the sensor cover 5016 can be removably connected to the sensor control device 5002 (e.g., the electronics housing 5004). The sensor cover 5018 helps provide a sealing barrier that surrounds and protects the exposed portions of the sensor 5090 and tip 5012 from gaseous chemical sterilization. As illustrated, the sensor cover 5018 may comprise a generally cylindrical body having a first end 5020a and a second end 5020b opposite to the first end 5020a. The first end 5020a can be opened to provide access to an internal chamber 5022 defined within the body. Conversely, the second end 5020b can be closed and may provide or otherwise define a connection feature 5024. As described herein, the connection feature 5024 helps connect the sensor cover 5018 to the cover of a sensor applicator (e.g., sensor applicator 150 of Figures 1 and 3A-3F). Figure 3B The applicator cover 708 is paired with the sensor cover 5018, which can help remove the sensor cover 5018 from the sensor control device 5002 when the cover is removed from the sensor applicator.

[0183] At or near the bottom of the bracket 5008, the sensor cover 5018 can be removably connected to the electronics housing 5004. More specifically, the sensor cover 5018 can be removably connected to a mating element 5016 extending distally from the bottom of the bracket 5008. For example, in at least one embodiment, the mating element 5016 can define a set of external threads 5026a (…). Figure 10B ), which is defined by a set of internal threads 5026b through the sensor cover 5018 ( Figure 10AThe components are mating. In some embodiments, the external and internal threads 5026a, b may include a flat thread design (e.g., lacking helical curvature), which may prove advantageous in molded parts. Alternatively, the external and internal threads 5026a, b may include a helical threaded connection. Accordingly, the sensor cover 5018 may be threadedly connected to the sensor control device 5002 at the mating element 5016 of the tip hub 5014. In other embodiments, the sensor cover 5018 may be removably connected to the mating element 5016 via other engagement types, including but not limited to interference or friction fits, or to fragile elements or materials that can be broken with minimal separation force (e.g., axial or rotational force).

[0184] In some embodiments, the sensor cover 5018 may comprise an integral (single) structure extending between the first end and the second ends 5020a, b. However, in other embodiments, the sensor cover 5018 may comprise two or more component parts. For example, in the illustrated embodiment, the sensor cover 5018 may include a sealing ring 5028 disposed at the first end 5020a and a desiccant cover 5030 disposed at the second end 5020b. The sealing ring 5028 may be configured to help seal the inner chamber 5022, as described in more detail below. In at least one embodiment, the sealing ring 5028 may comprise an elastomeric O-ring. The desiccant cover 5030 may contain or contain a desiccant to help maintain a preferred humidity level in the inner chamber 5022. The desiccant cover 5030 may also define or otherwise provide a connection feature 5024 for the sensor cover 5018.

[0185] Figure 11A-11C This is a progressive sectional side view showing the assembly of a sensor applicator 5102 with a sensor control device 5002, according to one or more embodiments. Once the sensor control device 5002 is fully assembled, it can then be loaded into the sensor applicator 5102. (Refer to...) Figure 11A The tip hub 5014 may include or otherwise define a hub spring claw 5302, which is configured to facilitate connection of the sensor control device 5002 to the sensor applicator 5102. More specifically, the sensor control device 5002 may be pushed into the sensor applicator 5102 and the hub spring claw 5302 may be received by a corresponding arm 5304 of the tip carrier 5306 located in the sensor applicator 5102.

[0186] exist Figure 11BIn this embodiment, the sensor control device 5002 is received by the tip carrier 5306 and thus secured in the sensor applicator 5102. Once the sensor control device 5002 is loaded into the sensor applicator 5102, the applicator cover 210 can be connected to the sensor applicator 5102. In some embodiments, the applicator cover 210 and the housing 208 may have opposing sets of mating threads 5308, which allow the applicator cover 210 to be screwed onto the housing 208 in a clockwise (or counterclockwise) direction and thereby secure the applicator cover 210 to the sensor applicator 5102.

[0187] As illustrated, the sheath 212 is also located within the sensor applicator 5102, and the sensor applicator 5102 may include a sheath locking mechanism 5310 configured to ensure that the sheath 212 does not prematurely fold during a vibration event. In the illustrated embodiment, the sheath locking mechanism 5310 may be included in a threaded connection between the applicator cap 210 and the sheath 212. More specifically, one or more internal threads 53l2a may be defined or otherwise provided on the inner surface of the applicator cap 210, and one or more external threads 53l2b may be defined or otherwise provided on the sheath 212. The internal and external threads 53l2a,b may be configured to thread-mate with the sensor applicator 5102 at thread 5308 along with the applicator cap 210. The internal and external threads 53l2a,b may have the same thread pitch as thread 5308, such that the applicator cap 210 can be helically connected to the housing 208.

[0188] exist Figure 11C The image shows the applicator cap 210 fully threaded (connected) to the housing 208. As illustrated, the applicator cap 210 may also provide and otherwise define a cap post 5314, which is centrally located inside the applicator cap 210 and extends proximally from its bottom. The cap post 5314 may be configured to receive at least a portion of the sensor cap 5018 as it is screwed onto the housing 208 along with the applicator cap 210.

[0189] With the sensor control device 5002 loaded into the sensor applicator 5102 and the applicator cover 210 properly secured, the sensor control device 5002 can then be subjected to gaseous chemical sterilization, which is configured to sterilize the electronics housing 5004 and any other exposed portions of the sensor control device 5002. Because the distal portions of the sensor 5090 and tip 5012 are sealed within the sensor cover 5018, the chemicals used during the gaseous chemical sterilization process cannot interact with the enzymes, chemicals, and biological substances provided on the tail 5104 and other sensor components, such as the membrane coating that regulates the analyte inflow.

[0190] Figures 12A-12CThis is a progressive sectional side view showing the assembly and disassembly of a sensor applicator 5102 with sensor control device 5002 according to one or more additional embodiments. The fully assembled sensor control device 5002 can be loaded into the sensor applicator 5102 by connecting a hub spring claw 5302 to an arm 5304 of a tip carrier 5306 located in the sensor applicator 5102, as generally described above.

[0191] In the described embodiment, the sheath arm 5604 of the sheath 212 can be configured to interact with a first positioning recess 5702a and a second positioning recess 5702b defined within the housing 208. The first positioning recess 5702a may alternatively be referred to as a "locking" positioning recess, and the second positioning recess 5702b may alternatively be referred to as a "launching" positioning recess. When the sensor control device 5002 is initially installed in the sensor applicator 5102, the sheath arm 5604 can be received in the first positioning recess 5702a. As discussed below, the sheath 212 can be activated to move the sheath arm 5604 to the second positioning recess 5702b, which positions the sensor applicator 5102 in the launching position.

[0192] exist Figure 12B In this configuration, the applicator cap 210 is aligned with and pushed toward the housing 208, thereby receiving the sheath 212 within the applicator cap 210. Instead of rotating the applicator cap 210 relative to the housing 208, the threads of the applicator cap 210 can be engaged with the corresponding threads of the housing 208, thus connecting the applicator cap 210 to the housing 208. An axial cut or groove 5703 (one shown) defined in the applicator cap 210 allows the portion of the applicator cap 210 near its threads to bend outwards to engage with the threads of the housing 208. As the applicator cap 210 engages with the housing 208, the sensor cap 5018 can correspondingly engage with the cap post 5314.

[0193] and Figure 11A-11CSimilarly, the sensor applicator 5102 may include a sheath locking mechanism configured to ensure that the sheath 212 does not fold prematurely during a vibration event. In the illustrated embodiment, the sheath locking mechanism includes one or more ribs 5704 (one shown) defined near the base of the sheath 212, configured to interact with one or more ribs 5706 (two shown) and a shoulder 5708 defined near the base of the applicator cap 210. The ribs 5704 may be configured to lock between the ribs 5706 and the shoulder 5708 while attaching the applicator cap 210 to the housing 208. More specifically, once the applicator cap 210 is engaged with the housing 208, the applicator cap 210 may be rotated (e.g., clockwise) to position the ribs 5704 of the sheath 212 between the ribs 5706 and the shoulder 5708 of the applicator cap 210 and thereby "lock" the applicator cap 210 in place until the user reverses the rotation of the applicator cap 210 to remove it for use. The connection between rib 5704 and rib 5706 and shoulder 5708 of applicator cover 210 also prevents sheath 212 from folding prematurely.

[0194] exist Figure 12C In the middle, remove the applicator cover 210 from the housing 208. (As follows) Figures 21A-21C In one embodiment, the applicator cap 210 can be removed by rotating the applicator cap 210 in the opposite direction, which correspondingly rotates the cap post 5314 in the same direction and causes the sensor cap 5018 to disengage from the mating element 5016, as generally described above. Furthermore, removing the sensor cap 5018 from the sensor control device 5002 exposes the sensor 5090 and the distal portion of the tip 5012.

[0195] As the applicator cap 210 is unscrewed from the housing 208, a rib 5704 defined on the sheath 212 can slidably engage the top of a rib 5706 defined on the applicator cap 210. The top of the rib 5706 can provide a corresponding inclined surface, which causes the sheath 212 to rotate upward with the applicator cap 210, and the upward movement of the sheath 212 causes the sheath arm 5604 to bend and disengage from its connection with the first positioning groove 5702a and be received in the second positioning groove 5702b. As the sheath 212 moves into the second positioning groove 5702b, the radial shoulder 5614 moves and disengages from its radial connection with the carrier arm 5608, which allows the passive force of the spring 5612 to push upward on the tip carrier 5306 and force the carrier arm 5608 to disengage from its connection with the groove 5610. As the tip carrier 5306 moves upward within the housing 208, the mating element 5016 can retract accordingly until it becomes flush, substantially flush, or nearly flush with the bottom of the sensor control device 5002. At this point, the sensor applicator 5102 is in the firing position. Accordingly, in this embodiment, removing the applicator cover 210 causes the mating element 5016 to retract accordingly.

[0196] I. Exemplary launching mechanisms for one-piece and two-piece applicators

[0197] Figures 13A-13F Detailed examples of implementations of the internal device mechanics are provided, illustrating the "launching" of the applicator 216 to apply the sensor control device 222 to the user and including a safe retraction tip 1030 to return the used applicator 216. Generally, these figures represent an exemplary procedure that drives the tip 1030 (supporting the sensor connected to the sensor control device 222) into the user's skin, withdraws the tip while leaving effective contact between the sensor and the user's interstitial fluid, and attaches the sensor control device to the user's skin with an adhesive. Those skilled in the art will recognize variations of the activities described for alternative applicator assembly implementations and components by referring to the figures. Furthermore, the applicator 216 may be a sensor applicator having a one-piece or two-piece construction as disclosed herein.

[0198] Now refer to Figure 13A A sensor 1102 is loaded within the tip 1030, positioned directly above the user's skin 1104. Rails 1106 (optionally three) of the upper guide portion 1108 can be provided to control the movement of the applicator 216 relative to the sheath 318. The sheath 318 is held in the applicator 216 by a positioning groove feature 1110, such that a suitable downward force along the longitudinal axis of the applicator 216 will cause the resistance provided by the positioning groove feature 1110 to be overcome, thereby allowing the tip 1030 and the sensor control device 222 to translate along the longitudinal axis into (and above) the user's skin 1104. Furthermore, the capture arm 1112 of the sensor carrier 1022 engages the tip retraction assembly 1024 to hold the tip 1030 in position relative to the sensor control device 222.

[0199] exist Figure 13B In this process, the user forcefully overcomes or ignores the positioning groove feature 1110, and the sheath 318 folds into the housing 314, driving the sensor control device 222 (with the connecting portion) to translate downward along the longitudinal axis as indicated by arrow L. The inner diameter of the guide portion 1108 on the sheath 318 constrains the position of the carrier arm 1112 throughout the entire stroke of the sensor / tip insertion process. The complementary surface 1116 of the opposite tip retraction assembly 1024 holds the carrier arm 1112 in place on the stop surface 1114, where the return spring 1118 is fully energized. According to an embodiment, instead of the user forcefully driving the sensor control device 222 to translate downward along the longitudinal axis as indicated by arrow L, the housing 314 may include a button (e.g., but not limited to a push button) that activates an active spring (e.g., but not limited to a coil spring) to drive the sensor control device 222.

[0200] exist Figure 13CIn the process, sensor 1102 and tip 1030 have reached full insertion depth. During this process, carrier arm 1112 passes through the inner diameter of upper guide portion 1108. Then, the compressive force of helical return spring 1118 radially outward drives tilting stop surface 1114, and the released force drives tip retraction assembly 1024, which pulls (slotted or otherwise configured) tip 1030 away from the user and away from sensor 1102. Figure 13D As indicated by arrow R.

[0201] like Figure 13E As shown, with the tip 1030 fully retracted, the upper guide portion 1108 of the sheath 318 is configured as the final locking feature 1120. (As...) Figure 13F As shown, the used applicator assembly 216 is removed from the insertion site, leaving the sensor control device 222, and the tip 1030 is securely fixed within the applicator assembly 216. The used applicator assembly 216 is now ready for processing.

[0202] When the sensor control device 222 is applied, the operation of the applicator 216 is designed to provide the user with the sensation that the insertion and retraction of the tip 1030 are both automatically performed by the internal mechanics of the applicator 216. In other words, the invention avoids the user experiencing the sensation of manually driving the tip 1030 against their own skin. Thus, once the user applies sufficient force to overcome the resistance of the positioning groove feature of the applicator 216, the resulting action of the applicator 216 will feel like a "triggered" automated response. The user will not perceive that they are providing additional force to drive the tip 1030 into their skin, even though the user provides full driving force and no additional deflection / driving means are used to insert the tip 1030. As above Figure 13C In detail, the retraction of the tip 1030 is automatically performed by the helical return spring 1118 of the applicator 216.

[0203] Regarding any applicator implementation and any of its components described herein, including but not limited to tip, tip module, and sensor module implementations, those skilled in the art will understand that these implementations can be sized and configured for sensors configured to sense analyte levels in bodily fluids within the subject's epidermis, dermis, or subcutaneous tissue. In some implementations, such as the analyte sensor disclosed herein, both the tip and distal portions can be sized and configured to be located at a specific distal depth (i.e., the furthest point of penetration in the tissue or layer of the subject's body, such as in the epidermis, dermis, or subcutaneous tissue). Regarding certain applicator implementations, those skilled in the art will understand that some implementations of the tip can be sized and configured to be located at different distal depths in the subject's body relative to the final distal depth of the analyte sensor. For example, in some implementations, the tip can be located at a first distal depth in the subject's epidermis before retraction, while the distal portion of the analyte sensor can be located at a second distal depth in the subject's dermis. In other implementations, the tip can be located at a first distal depth in the subject's dermis before retraction, while the distal portion of the analyte sensor can be located at a second distal depth in the subject's subcutaneous tissue. In other embodiments, the tip can be located at a first end depth before retraction, while the analyte sensor can be located at a second end depth, wherein both the first and second end depths are in the same layer or tissue of the subject's body.

[0204] Additionally, with respect to any applicator implementation described herein, those skilled in the art will understand that the analyte sensor and one or more structural components connected thereto, including, but not limited to, one or more spring mechanisms, can be arranged in the applicator at an off-center position relative to one or more axes of the applicator. For example, in some applicator implementations, the analyte sensor and spring mechanism can be arranged at a first off-center position relative to the applicator axis on a first side of the applicator, while the sensor electronics can be arranged at a second off-center position relative to the applicator axis on a second side of the applicator. In other applicator implementations, the analyte sensor, spring mechanism, and sensor electronics can be arranged at an off-center position relative to the applicator axis on the same side. Those skilled in the art will understand that other arrangements and configurations in which any or all of the applicator's analyte sensors, spring mechanisms, sensor electronics, and other components are arranged at a central or off-center position relative to one or more applicator axes are possible and fully within the scope of this disclosure.

[0205] Additional details describing suitable apparatus, systems, methods, components, their operation, and related features are found in Rao et al. International Publication No. WO2018 / 136898, Thomas et al. International Publication No. WO2019 / 236850, Thomas et al. International Publication No. WO2019 / 236859, Thomas et al. International Publication No. WO2019 / 236876, and US Patent Publication No. 2020 / 0196919, filed June 6, 2019, all of which are incorporated herein by reference. Further details describing embodiments of the applicator, its components, and variations thereof are found in US Patent Publications Nos. 2013 / 0150691, 2016 / 0331283, and 2018 / 0235520, all of which are incorporated herein by reference and used for all purposes. Further details of embodiments of the tip module, tip, its components and variations thereof are described in US Patent Publication No. 2014 / 0171771, which is incorporated herein by reference in its entirety and for all purposes.

[0206] J. Exemplary methods for calibrating analyte sensors

[0207] Biochemical sensors can be described by one or more sensing characteristics. A common sensing characteristic is called the sensitivity of a biochemical sensor, which is a measure of how responsive the sensor is to the concentration of a chemical or composition it is designed to detect. For electrochemical sensors, this response can be in the form of current (current method) or charge (coulomb method). For other types of sensors, the response can take different forms, such as photon intensity (e.g., optical light). The sensitivity of a biochemical analyte sensor can vary depending on many factors, including whether the sensor is in vitro or in vivo.

[0208] Figure 14This figure illustrates the in vitro sensitivity of a current analyte sensor. In vitro sensitivity can be obtained by testing the sensor in vitro at various analyte concentrations and then performing regression (e.g., linear or nonlinear) or other curve fitting on the resulting data. In this example, the analyte sensor sensitivity is linear or substantially linear and can be modeled according to the formula y = mx + b, where y is the sensor's output current, x is the analyte level (or concentration), m is the slope of the sensitivity, and b is the intercept of the sensitivity, where the intercept generally corresponds to the background signal (e.g., noise). For sensors with linear or substantially linear responses, the analyte level corresponding to a given current can be determined from the slope and intercept of the sensitivity. Sensors with nonlinear sensitivity require additional information to determine the analyte level corresponding to the sensor's output current, and those skilled in the art are familiar with methods for modeling nonlinear sensitivity. In some embodiments of in vivo sensors, the in vitro sensitivity can be the same as the in vivo sensitivity, but in other embodiments, a transfer (or transformation) function is used to convert the in vitro sensitivity into an in vivo sensitivity feasible for the sensor desired for in vivo use.

[0209] Calibration is a technique that improves or maintains accuracy by adjusting the sensor's measurement output to reduce the difference from the sensor's expected output. One or more parameters describing the sensor's sensing characteristics, such as its sensitivity, are used in the calibration process.

[0210] Some in vivo analyte monitoring systems require calibration after sensor implantation in a user or patient, either through user interaction or automatically via the system itself. For example, in cases requiring user interaction, the user performs an in vitro measurement (e.g., blood glucose (BG) measurement, using a finger prick and an in vitro test strip) and inputs it into the system while the analyte sensor is implanted. The system then compares the in vitro measurement with the in vivo signal and uses the difference to determine an estimate of the sensor's in vivo sensitivity. The in vivo sensitivity can then be used in an algorithmic process to translate the sensor-collected data into a value indicating the user's analyte level. This and other processes requiring user action for calibration are called "user calibration." Due to the instability of sensor sensitivity (and thus sensitivity drifting or changing over time), the system may require user calibration. Consequently, multiple user calibrations may be required (e.g., according to a periodic (e.g., daily) schedule, a variable schedule, or on demand) to maintain accuracy. While the embodiments described herein can incorporate a degree of user calibration for a particular implementation, this is generally not preferred because it requires painful or strenuous BG measurements and can introduce user error.

[0211] Some in vivo analyte monitoring systems can regularly adjust calibration parameters using automated measurements of sensor characteristics performed by the system itself (e.g., processing circuitry executing software). Repeated adjustment of sensor sensitivity based on system- (rather than user-) variable measurements is generally referred to as "system" (or automated) calibration, and can be performed alongside user calibration, such as early bio-growth (BG) measurements, or without user calibration. Similar to repeated user calibration, repeated system calibration is generally required due to sensor sensitivity drift over time. Therefore, while the embodiments described herein can utilize a degree of automated system calibration, it is preferable that the sensor sensitivity remains relatively stable over time, thus eliminating the need for post-implantation calibration.

[0212] Some in vivo analyte monitoring systems operate using factory-calibrated sensors. Factory calibration refers to the determination or estimation of one or more calibration parameters before distribution to users or healthcare professionals (HCPs). Calibration parameters can be determined by the sensor manufacturer (or the manufacturer of other components of the sensor control unit, if the two differ). Many in vivo sensor manufacturing processes produce sensors in batches, referred to as production batches, production stage batches, or simply batches. A single batch can contain thousands of sensors.

[0213] The sensor can include a calibration code or parameter, which can be generated or determined during the manufacturing process of one or more sensors and encoded or programmed into the data processing unit of the analyte monitoring system as part of the manufacturing process, or provided on the sensor itself, such as as a barcode, laser tag, RFID tag, or other machine-readable information provided on the sensor. Providing this code to a receiver (or other data processing unit) can avoid user calibration during in-body use of the sensor, or reduce the frequency of in-body calibration during sensor wear. In embodiments where the calibration code or parameter is provided on the sensor itself, the calibration code or parameter can be automatically transmitted or provided to the data processing unit of the analyte monitoring system before or at the start of sensor use.

[0214] Some in vivo analyte monitoring systems operate using sensors that can be one or more of factory-calibrated, system-calibrated, and / or user-calibrated. For example, a sensor can provide a calibration code or parameter that allows for factory calibration. If information (e.g., user input) is provided to a receiver, the sensor can operate as a factory-calibrated sensor. If no information is provided to the receiver, the sensor can operate as a user-calibrated sensor and / or a system-calibrated sensor.

[0215] In a further aspect, programmed or executable instructions can be provided or stored in the data processing unit and / or receiver / controller unit of the analyte monitoring system to provide time-varying adjustment algorithms to the in vivo sensor during use. For example, based on retrospective statistical analysis of the analyte sensor used in vivo and the corresponding glucose level feedback, predetermined or analyzed curves or databases can be generated over time and configured to provide additional adjustments to one or more in vivo sensor parameters to compensate for possible sensor stability drift or other factors.

[0216] According to the subject matter of this disclosure, an analyte monitoring system can be configured to compensate for or adjust sensor sensitivity based on sensor drift characteristics. A time-varying parameter β(t) can be defined or determined based on the behavior of the analytical sensor during in vivo use, and the time-varying drift characteristics can be determined. In some aspects, the compensation or adjustment of sensor sensitivity can be programmed in the receiver unit, the controller of the analyte monitoring system, or the data processor, so that compensation or adjustment, or both, can be performed automatically and / or iteratively upon receiving sensor data from the analyte sensor. According to the subject matter of this disclosure, the adjustment or compensation algorithm can be initialized or executed by the user (rather than self-initialized or executed), thereby adjusting or compensating the analyte sensor sensitivity curve upon user initialization or activation of the corresponding function or routine, or upon user input of a sensor calibration code.

[0217] According to the subject matter of this disclosure, it is possible to nondestructively inspect individual sensors in a batch of sensors (in some cases excluding sample sensors used for in vitro testing) to determine or measure their characteristics, such as film thickness, at one or more points on the sensor, and to measure or determine other characteristics, including physical characteristics such as the surface area / volume of the active region. The measurements or determinations can be performed automatically using, for example, an optical scanner or other suitable measuring device or system, and the sensor characteristics determined for each sensor in the batch can be compared with corresponding average values ​​based on the sample sensors, allowing for possible corrections to calibration parameters or codes assigned to each sensor. For example, for a calibration parameter defined as sensor sensitivity, sensitivity is approximately inversely proportional to film thickness, such that, for example, a sensor having a measurement film thickness that is approximately 4% greater than the average film thickness of sampled sensors from the same batch of sensors, the sensitivity assigned to that sensor in one embodiment is the average sensitivity determined from the sampled sensors divided by 1.04. Similarly, since sensitivity is approximately proportional to the active area of ​​the sensor, a sensor having a measurement active area that is approximately 3% less than the average active area of ​​sampled sensors from the same batch of sensors, the sensitivity assigned to that sensor is the average sensitivity multiplied by 0.97. By performing multiple consecutive adjustments to each inspection or measurement of the sensor, the assigned sensitivity can be determined from the average sensitivity of the sampling sensor. In some embodiments, in addition to film thickness and / or the surface area or volume of the active sensing region, the inspection or measurement of each sensor can also additionally include measuring film consistency or texture.

[0218] Additional information regarding sensor calibration is provided in US Publication No. 2010 / 00230285 and US Publication No. 2019 / 0274598, both of which are incorporated herein by reference in their entirety.

[0219] K. Exemplary Bluetooth Communication Solution

[0220] The storage memory 5030 of sensor 110 may include software blocks relating to communication schemes for the communication module. For example, storage memory 5030 may include BLE service software blocks that provide an interface making the BLE module 5041 available to the computing hardware of sensor 110. These software functions may include a BLE logic interface and an interface analysis program. The BLE services provided by communication module 5040 may include general access feature services, general attribute services, general access services, device information services, data transmission services, and security services. The data transmission service may be the primary service, used to transmit data such as sensor control data, sensor status data, analyte measurement data (historical and current), and event log data. Sensor status data may include error data, current activity time, and software status. Analyte measurement data may include information such as current and historical coarse measurements, current and historical values ​​after processing with appropriate algorithms or models, projections and trends of measurement levels, comparisons of other values ​​with patient-specific averages, behavioral calls determined by algorithms or models, and other similar data types.

[0221] Based on various aspects of this disclosure and as illustrated herein, by adjusting the hardware of sensor 110 and the characteristics of the communication scheme or medium supported by the radio, sensor 110 can be configured to communicate simultaneously with multiple devices. For example, the BLE module 5041 of communication module 5040 can be provided by software or firmware to enable multiple simultaneous connections between: sensor 110 as a central device and other devices as peripheral devices, or sensor 110 as a peripheral device and other devices as a central device.

[0222] The use of communication schemes such as BLE for connection and subsequent communication dialogue between two devices can be characterized by similar physical channels operating between the two devices (e.g., sensor 110 and data receiving device 120). A physical channel can include a single channel or a series of channels, including, but not limited to, a series of channels using a protocol determined by a common clock and channel hopping or frequency hopping procedure. Communication dialogues can use similar amounts of available communication spectrum, and multiple such dialogues can exist in close proximity. In some embodiments, different groups of devices in a communication dialogue use different physical channels or series of channels to manage interference from neighboring devices.

[0223] For illustrative purposes and not for limitation, reference is made to an exemplary implementation of a sensor-receiver connection procedure used in the subject matter of this disclosure. First, sensor 110 repeatedly advertises its connectivity information to its environment to search for data receiving device 120. Sensor 110 is capable of periodically repeating the broadcast until a connection is established. Data receiving device 120 detects the broadcast packets and scans and filters for data connections offered by sensor 110 via the broadcast packets. Subsequently, data receiving device 120 sends a scan request command, and sensor 110 responds with a scan response packet providing additional details. Then, data receiving device 120 sends a connection request using the Bluetooth device address associated with data receiving device 120. Data receiving device 120 is also capable of continuously requesting to establish a connection with sensor 110 having a specific Bluetooth device address. The devices then establish an initial connection, allowing them to begin exchanging data. The devices begin the process of initializing a data exchange service and performing a mutual authentication procedure.

[0224] During the initial connection between sensor 110 and data receiving device 120, data receiving device 120 is able to initialize a service, feature, and attribute discovery process. Data receiving device 120 can evaluate these features of sensor 110 and store them for use during subsequent connections. Subsequently, the device issues a notification of a customized security service for mutual authentication between sensor 110 and data receiving device 120. The mutual authentication process can be automated and requires no user interaction. After successful completion of the mutual authentication process, sensor 110 sends a connection parameter update requesting data receiving device 120 to use connection parameter settings preferred by sensor 110 and configured for maximum lifespan.

[0225] Data receiving device 120 then performs a sensor control program to backfill historical data, current data, event logs, and plant data. For example, for each type of data, data receiving device 120 sends a request to initiate the backfilling process. The request can specify a series of records based on, for example, measurements, timestamps, or similar parameters, as needed. Sensor 110 responds with the requested data until all previously unsent data in sensor 110's memory is delivered to data receiving device 120. Sensor 110 can respond to data receiving device 120's backfilling request to indicate that all data has been sent. Once backfilling is complete, data receiving device 120 can alert sensor 110 that it is ready to receive periodic measurement readings. Sensor 110 can repeatedly send readings in response to multiple notifications. As illustrated herein, multiple notifications can be redundant to ensure correct data transmission. Alternatively, multiple notifications can form a single payload.

[0226] For illustrative purposes and not for limitation, reference is made to an exemplary implementation of the procedure for sending a shutdown command to sensor 110. If sensor 110 is in, for example, an error state, an insertion failure state, or a sensor expired state, a shutdown operation is performed. If sensor 110 is not in those states, sensor 110 can record the command and perform shutdown if sensor 110 transitions to an error state or a sensor expired state. Data receiving device 120 sends a shutdown command in an appropriately formatted manner to sensor 110. If sensor 110 is processing other commands, sensor 110 will respond with a standard error response, indicating that sensor 110 is busy. Otherwise, sensor 110 sends a response upon receiving the command. Additionally, sensor 110 sends a success notification via sensor control features to confirm that sensor 110 has received the command. Sensor 110 records the shutdown command. At a later appropriate opportunity (e.g., depending on the current sensor state, as described herein), sensor 110 will shut down.

[0227] L. Exemplary sensor status and activation

[0228] For illustrative purposes and not for limitation, the exemplary implementation described in the high-level description of state machine diagram 6000 is as follows: Figure 15 The diagram illustrates the actions that sensor 110 can perform. After initialization, the sensor enters state 6005, which pertains to the manufacturing of sensor 110. In manufacturing state 6005, sensor 110 can be configured for operation, for example, it can be written to storage memory 5030. At various times in state 6005, sensor 110 checks received commands to enter storage state 6015. Upon entering storage state 6015, the sensor performs a software integrity check. While in storage state 6015, the sensor can also receive activation request commands, subsequently entering insertion detection state 6025.

[0229] Upon entering state 6025, sensor 110 can store information relating to a device verified to communicate with the sensor, as set during activation, or initialize an algorithm involved in performing and interpreting measurements from sensing hardware 5060. Sensor 110 can also initialize a lifecycle timer responsible for maintaining an active count of sensor 110 operation time and begin communicating with the verification device to transmit recorded data. In insertion detection state 6025, the sensor can enter state 6030, where sensor 110 checks whether the operation time is equal to a predetermined threshold. This operation time threshold corresponds to a timeout function used to determine whether insertion has been successful. If the operation time has reached the threshold, sensor 110 proceeds to state 6035, where sensor 110 checks whether the average data read is greater than a threshold amount corresponding to the expected data read volume, triggering a successful insertion detection. If the data read volume is below the threshold during state 6035, the sensor proceeds to state 6040, corresponding to insertion failure. If the data read volume meets the threshold, the sensor proceeds to the active pairing state 6055.

[0230] The active pairing state 6055 of sensor 110 reflects the normal operating state of sensor 110, which is performed by recording measured values, processing measured values, and reporting them as needed. In the active pairing state 6055, sensor 110 sends measurement results or attempts to establish a connection with receiving device 120. Sensor 110 also increases its operating time. Once sensor 110 reaches a predetermined threshold operating time (e.g., once the operating time reaches a predetermined threshold), sensor 110 transitions to the active expiration state 6065. The active expiration state 6065 of sensor 110 reflects the state in which sensor 110 has operated for its maximum predetermined amount of time.

[0231] When in the activation expiration state 6065, the sensor 110 can generally perform operations involving slowing down operation and ensuring that collected measurements are safely transmitted to the receiving device as needed. For example, in the activation expiration state 6065, the sensor 110 can transmit collected data and, if no connection is available, can increase its effort to locate and establish a connection with a nearby verification device. In the activation expiration state 6065, the sensor 110 can receive a shutdown command in state 6070. If no shutdown command is received, the sensor 110 in state 6075 can also check whether the operating time has exceeded a final operating threshold. The final operating threshold can be based on the battery life of the sensor 110. The normal endpoint state 6080 corresponds to the final operation of the sensor 110 and finally shuts down the sensor 110.

[0232] Before sensor activation, ASIC 5000 is in a low-power storage mode. For example, when the power supply voltage driving ASIC 5000 in an RF field (e.g., an NFC field) exceeds a reset threshold, the activation process can begin, causing sensor 110 to enter a wake-up state. While in the wake-up state, ASIC 5000 enters the activation procedure state. ASIC 5000 then wakes up communication module 5040. Communication module 5040 is initialized, triggering a power-on self-test (POST). The POST can include ASIC 5000 communicating with communication module 5040 using a pre-defined programmable procedure for reading and writing data to verify that the memory and one-time programmable memory are not damaged.

[0233] When the ASIC 5000 first enters measurement mode, an insertion detection procedure is performed to confirm that the sensor 110 has been properly installed on the patient's body before appropriate measurements can be taken. First, the sensor 110 interprets the command to activate the measurement configuration process, causing the ASIC 5000 to enter measurement command mode. The sensor 110 then temporarily enters a measurement lifecycle state to perform multiple consecutive measurements to detect whether the insertion was successful. The communication module 5040 or the ASIC 5000 evaluates the measurement results to determine if the insertion was successful. If the insertion is considered successful, the sensor 110 enters the measurement state, where it begins periodic measurements using the sensing hardware 5060. If the sensor 110 determines that the insertion was unsuccessful, it is triggered to enter an insertion failure mode, in which the ASIC 5000 is commanded to return to storage mode while the communication module 5040 disables itself.

[0234] M. Exemplary in-flight update

[0235] Figure 1B Further illustrative examples of the operating environment are provided to illustrate the over-the-air ("OTA") updates used in the techniques described herein. The operator of the analyte monitoring system 100 can package updates for the data receiving device 120 or sensor 110 into updates for applications executed on the multi-target data receiving device 130. Utilizing the available communication channels between the data receiving device 120, the multi-target data receiving device 130, and the sensor 110, the multi-target data receiving device 130 can receive periodic updates for the data receiving device 120 or sensor 110 and initiate update installation on the data receiving device 120 or sensor 110. The multi-target data receiving device 130 acts as an installation or update platform for the data receiving device 120 or sensor 110 because applications enabling communication between the multi-target data receiving device 130 and the analyte sensor 110, the data receiving device 120, and / or the remote application server 1150 can update the software or firmware on the data receiving device 120 or sensor 110 without wide area network capabilities.

[0236] As illustrated herein, a remote application server 1150, operated by the manufacturer of the analyte sensor 110 and / or the operator of the analyte monitoring system 100, can provide software and firmware updates to the devices of the analyte monitoring system 100. In a specific embodiment, the remote application server 1150 can provide updated software and firmware to the user device 1140 or directly to the multi-target data receiving device. As illustrated herein, the remote application server 1150 can also provide application software updates to the application store server 160 using an interface provided by the application store. The multi-target data receiving device 130 can periodically contact the application store server 160 to download and install updates.

[0237] After the multi-target data receiving device 130 downloads an application update, including firmware or software updates, for the data receiving device 120 or sensor 110, a connection is established between the data receiving device 120 or sensor 110 and the multi-target data receiving device 130. The multi-target data receiving device 130 determines that the firmware or software update is available for the data receiving device 120 or sensor 110. The multi-target data receiving device 130 is capable of preparing the software or firmware update for delivery to the data receiving device 120 or sensor 110. For example, the multi-target data receiving device 130 can compress or cut the data related to the software or firmware update, encrypt or decrypt the firmware or software update, or perform an integrity check on the firmware or software update. The multi-target data receiving device 130 sends the data for the firmware or software update to the data receiving device 120 or sensor 110. The multi-target data receiving device 130 is also capable of sending commands to the data receiving device 120 or sensor 110 to initiate the update. Additionally or alternatively, the multi-target data receiving device 130 may provide notifications to the user of the multi-target data receiving device 130 and include instructions to facilitate updates, such as instructions to keep the data receiving device 120 and the multi-target data receiving device 130 connected to power and in proximity until the update is complete.

[0238] Data receiving device 120 or sensor 110 receives data for updating and commands to initiate the update from multi-target data receiving device 130. Data receiving device 120 can then install firmware or software updates. To install the update, data receiving device 120 or sensor 110 can enter a so-called "safe" mode with limited operational capabilities or reboot itself in this mode. Once the update is complete, data receiving device 120 or sensor 110 re-enters or reboots into standard operating mode. Data receiving device 120 or sensor 110 can perform one or more self-tests to determine that the firmware or software update was successfully installed. Multi-target data receiving device 130 can receive a notification of a successful update. Multi-target data receiving device 130 can then report confirmation of a successful update to remote application server 1150.

[0239] In a specific embodiment, the storage memory 5030 of sensor 110 includes one-time programmable (OTP) memory. The term OTP memory can refer to memory that includes access restrictions and security to facilitate writing to a specific address or segment of memory a predetermined number of times. Memory 5030 can be pre-arranged into multiple pre-allocated memory blocks or containers. Containers are pre-allocated to a fixed size. If storage memory 5030 is one-time programmable memory, containers can be considered to be in a non-programmable state. Additional containers that have not yet been written to can be placed in a programmable or writable state. Containerizing storage memory 5030 in this way improves the transportability of code and data to be written to storage memory 5030. Software updates for devices (e.g., the sensor devices described herein) stored in OTP memory can be performed such that only the code in one or more pre-written containers is replaced with update code written to one or more new containers, rather than replacing all the code in the memory. In a second embodiment, the memory is not pre-arranged. Instead, the space allocated for data is dynamically allocated or determined on demand. Incremental updates can be issued because containers of varying sizes can be defined when an update is anticipated.

[0240] Figure 16 This is a diagram illustrating example operations and data flow for over-the-air (OTA) programming of the storage memory 5030 in sensor device 110 and for using the memory after OTA programming during the execution of sensor device 110, in accordance with the subject matter of this disclosure. Figure 5 In the example OTA programming 500 described herein, a request is sent from an external device (e.g., data receiving device 130) to initiate OTA programming (or reprogramming). At 511, the communication module 5040 of the sensor device 110 receives the OTA programming command. The communication module 5040 sends the OTA programming command to the microcontroller 5010 of the sensor device 110.

[0241] At 531, after receiving the OTA programming command, the microcontroller 5010 confirms the OTA programming command. The microcontroller 5010 can determine, for example, whether the OTA programming command is signed with an appropriate digital signature token. Upon determining that the OTA programming command is valid, the microcontroller 5010 can set the sensor device to OTA programming mode. At 532, the microcontroller 5010 can confirm the OTA programming data. At 533, the microcontroller 5010 can reset the sensor device 110 to reinitialize it to a programming state. Once the sensor device 110 has transitioned to the OTA programming state, the microcontroller 5010 can begin writing data to the rewritable memory 540 (e.g., memory 5020) of the sensor device at 534 and to the OTP memory 550 (e.g., storage memory 5030) of the sensor device at 535. The data written by the microcontroller 5010 can be based on the confirmed OTA programming data. The microcontroller 5010 can write data to cause one or more programming blocks or areas of the OTP memory 550 to be marked as invalid or inaccessible. Data written to free or unused portions of the OTP memory can be used to replace faulty or inaccessible programming blocks in the OTP memory 550. After the microcontroller 5010 writes data to each memory at steps 534 and 535, the microcontroller 5010 can perform one or more software integrity checks to ensure that no errors were introduced into the programming blocks during the writing process. Once the microcontroller 5010 can determine that the data has been written without errors, the microcontroller 5010 can continue the standard operation of the sensor device.

[0242] In execution mode, at 536, the microcontroller 5010 can retrieve a programming manifest or configuration file from the rewritable memory 540. The programming manifest or configuration file can include a list of valid software programming blocks and can include instructions for executing the sensor 110 program. By following the programming manifest or configuration file, the microcontroller 5010 can determine which memory block of the OTP memory 550 is suitable for execution and avoid executing expired or invalid programming blocks or referencing expired data. At 537, the microcontroller 5010 can selectively reclaim memory blocks from the OTP memory 550. At 538, the microcontroller 5010 can use the reclaimed memory blocks by executing stored programming code or using variables stored in the memory.

[0243] N. Exemplary safety and other constructive features

[0244] As illustrated herein, a first layer of security for communication between the analyte sensor 110 and other devices can be established based on a security scheme specified and integrated therein by a communication scheme for communication. A second layer of security can be based on a communication scheme requiring close proximity to the communication devices. Additionally, some packets and / or some data included in packets can be encrypted, while data in other packets and / or packets may be encrypted or unencrypted in other ways. Alternatively or additionally, application-layer encryption can be used with one or more block ciphers or stream ciphers to establish mutual authentication and encrypted communication with other devices in the analyte monitoring system 100.

[0245] The ASIC 5000 of the analyte sensor 110 can be configured to dynamically generate authentication and encryption keys using data stored in the storage memory 5030. The storage memory 5030 can also be pre-programmed with a set of valid authentication and encryption keys for use with specific types of devices. The ASIC 5000 can be further configured to use received data for authentication procedures with other devices and to use the generated keys for sensitive data before transmission. The generated keys can be unique to the analyte sensor 110, unique to a pair of devices, unique to a communication dialogue between the analyte sensor 110 and other devices, unique to a message sent during a communication dialogue, or unique to a data block contained in a message.

[0246] Both sensor 110 and data receiving device 120 are capable of ensuring that other participants in the communication conversation are authorized, such as issuing commands or receiving data. In a specific embodiment, authentication can be performed through two features. First, the participant claiming their identity provides a verified certificate signed by the device manufacturer or the operator of the analyte monitoring system 100. Second, authentication can be performed using a public key and a private key and a shared secret derived from them, established by the device of the analyte monitoring system 100 or by the operator of the analyte monitoring system 100. To verify the identity of other participants, participants can provide evidence that they have control of their private keys.

[0247] Manufacturers of the analyte sensor 110 and data receiving device 120, or providers of the multi-target data receiving device 130, can provide the information and programming necessary for secure communication of the devices through secure programming and updates. For example, manufacturers can provide information that can be used to generate encryption keys for each device, including a fixed root key for the analyte sensor 110 and optionally for the data receiving device 120, which can be combined with device-specific information and operational data (e.g., entropy-based random values) to generate unique encryption values ​​for devices, conversations, or data transmissions on demand.

[0248] Analyte data relating to users is sensitive, at least in part because the information can be used for various purposes, including health monitoring and dosage decisions. In addition to user data, the analyte monitoring system 100 can perform security hardening to prevent reverse engineering by unauthorized actors. Communication links can be encrypted with device-specific or session-specific encryption keys. Encrypted or unencrypted communication between any two devices can be verified using transmission integrity checks embedded in the communication. The operation of the analyte sensor 110 can be protected against tampering by restricting access to the read / write functionality of the memory 5020 via the communication interface. The sensor can be configured to authorize access only to known or "trusted" devices provided in a "whitelist," or only to devices that can provide a manufacturer-assigned code or otherwise authenticated users. The whitelist can represent an exclusive scope, meaning that connection identifiers other than those included in the whitelist will not be used; or a preferred scope where the whitelist is searched first, but other devices can still be used. If the requester cannot complete the login process within a predetermined time period (e.g., within 4 seconds) via the communication interface, the sensor 110 can further reject and close the connection request. These features protect against specific denial-of-service attacks, especially those on BLE interfaces.

[0249] As illustrated herein, the analyte monitoring system 100 can use periodic key rotation to further reduce the likelihood of key leakage and exploitation. The key rotation strategy used by the analyte monitoring system 100 can be designed to support reverse compatibility with field-deployed or distributed devices. For example, the analyte monitoring system 100 can use keys from downstream devices (e.g., in-field devices or devices where updates are not feasible) that are designed to be compatible with multi-generation keys used by upstream devices.

[0250] For illustrative purposes and not for limitation, such as Figure 17The exemplary embodiment shown with reference to message sequence diagram 600 for the purposes of this disclosure illustrates an example of data exchange between a pair of devices, specifically sensor 110 and data receiving device 120. As illustrated herein, data receiving device 120 can be either a data receiving device 120 or a multi-target data receiving device 130. In step 605, data receiving device 120 can transmit a sensor activation command 605 to sensor 110, for example via a short-range communication scheme. Prior to step 605, sensor 110 can be in a primary sleep state, retaining its battery until full activation is required. After activation during step 610, sensor 110 can collect data or perform other appropriate operations on sensor hardware 5060. In step 615, data receiving device 120 can initialize verification request command 615. In response to verification request command 615, both sensor 110 and data receiving device 120 can participate in mutual verification process 620. The mutual verification process 620 can involve the transfer of data, including challenge parameters, which allows sensor 110 and data receiving device 120 to ensure that the other device fully adheres to the consent security framework described herein. Mutual verification can be based on a mechanism of mutual verification between two or more individuals, requiring or not requiring an online trusted third party to verify the key established via challenge-response. Mutual verification can be performed with two, three, four, or five verifications or similar forms.

[0251] Following a successful mutual authentication process 620, in step 625, sensor 110 can provide sensor secret 625 to data receiving device 120. The sensor secret can contain a sensor-unique value and be derived from a random value generated during manufacturing. The sensor secret can be encrypted before or during transmission to prevent third-party access. Sensor secret 625 can be encrypted via one or more keys generated through or in response to the mutual authentication process 620. In step 630, data receiving device 120 can derive a sensor-unique encryption key from the sensor secret. The sensor-unique encryption key can also be session-unique. Thus, the sensor-unique encryption key can be determined by each device without transmission between sensor 110 and data receiving device 120. In step 635, sensor 110 can encrypt data to include in the payload. In step 640, sensor 110 can transmit the encrypted payload 640 to data receiving device 120 using a communication link established between sensor 110 and data receiving device 120 using an appropriate communication model. In step 645, the data receiving device 120 is able to decrypt the payload using the sensor-specific encryption key derived during step 630. After step 645, the sensor 110 is able to deliver additional (including newly collected) data, and the data receiving device 120 is able to process the received data appropriately.

[0252] As discussed herein, sensor 110 can be a device with limited processing power, battery supply, and storage. The encryption techniques used by sensor 110 (e.g., the choice of cryptographic algorithms or implementations) can be selected, at least in part, based on these limitations. Data receiving device 120 can be a more powerful device with fewer of these limitations. Therefore, data receiving device 120 can use more sophisticated, computationally intensive encryption techniques, such as cryptographic algorithms and implementations.

[0253] O. Exemplary payload / communication frequency

[0254] The analyzer sensor 110 can be configured to alter its discoverability behavior in an attempt to increase the likelihood that the receiving device will receive appropriate data packets and / or provide an acknowledgment signal or otherwise reduce limitations that could lead to the failure to receive an acknowledgment signal. Altering the discoverability behavior of the analyzer sensor 110 can include, for example, but not limited to, changing the frequency at which connection data is included in the data packets, changing the frequency at which data packets are generally transmitted, lengthening or shortening the broadcast window of the data packets, changing the amount of time the analyzer sensor 110 listens for acknowledgment or scan signals after broadcasting, including directed transmission to one or more devices that have previously communicated with the analyzer sensor 110 (e.g., through one or more attempts) and / or to one or more devices on a whitelist, changing the transmission power associated with the communication module when broadcasting data packets (e.g., increasing broadcast range or reducing power consumption and extending the analyzer sensor's battery life), changing the rate at which data packets are prepared and broadcast, or a combination of one or more other variations. Additionally or alternatively, the receiving device can similarly adjust parameters relating to the device's listening behavior to increase the likelihood of receiving data packets including connection data.

[0255] As illustrated herein, the analyzer sensor 110 can be configured to broadcast data packets using two types of windows. The first window refers to the rate at which the analyzer sensor 110 is configured to operate its communication hardware. The second window refers to the rate at which the analyzer sensor 110 is configured to actively transmit data packets (e.g., broadcast). For example, the first window could refer to the analyzer sensor 110 operating its communication hardware to send and / or receive data packets (including connection data) during the first 2 seconds of each 60-second time period. The second window could refer to the analyzer sensor 110 transmitting data packets every 60 milliseconds during each 2-second window. For the remainder of the 2-second window, the analyzer sensor 110 is scanning. The analyzer sensor 110 can extend or shorten each window to adjust its detectability behavior.

[0256] In specific implementations, the discoverability behavior of the analyte sensor can be stored in a discoverability configuration file and can be modified based on one or more factors, such as the state of the analyte sensor 110, and / or by applying rules based on the state of the analyte sensor 110. For example, when the battery level of the analyte sensor 110 is below a certain amount, a rule can cause the analyte sensor 110 to reduce the power consumed during the broadcast process. As another example, configuration settings related to broadcasting or otherwise transmitting packets can be adjusted based on: ambient temperature, the temperature of the analyte sensor 110, or the temperature of certain components of the communication hardware of the analyte sensor 110. In addition to adjusting the transmission power, other parameters related to the transmission capability or process of the communication hardware of the analyte sensor 110 can be adjusted, including but not limited to transmission rate, frequency, and timing. As yet another example, when analyte data indicates that a subject is experiencing or will experience a negative health event, a rule can cause the analyte sensor 110 to increase its discoverability to alert the receiving device of the negative health event.

[0257] P. Exemplary sensor sensitivity initialization / adjustment characteristics

[0258] As illustrated herein, certain calibration characteristics of the sensing hardware 5060 of the analyte sensor 110 can be adjusted based on external or internal environmental characteristics and to compensate for degradation of the sensing hardware 5060 during prolonged periods of non-use (e.g., "shelf time" before use). The calibration characteristics of the sensing hardware 5060 can be adjusted autonomously by the sensor 110 (e.g., by operating the ASIC 5000 to adjust characteristics in memory 5020 or storage 5030) or by other means of the analyte monitoring system 100.

[0259] For example, the sensor sensitivity of sensing hardware 5060 can be adjusted based on external temperature data or time since manufacturing. When monitoring external temperature during sensor storage, the subject matter of this disclosure can adaptively change the compensation for sensor sensitivity over time as the device experiences changing storage conditions. For illustrative purposes and not as a limitation, adaptive sensitivity adjustment can be performed in an "active" storage mode, in which the analyte sensor 110 is periodically woken up to measure temperature. These features can conserve battery power in the analyte device and extend the lifespan of the analyte sensor. At each temperature measurement, the analyte sensor 110 can calculate a sensitivity adjustment for that time interval based on the measured temperature. The temperature-weighted adjustment can then be accumulated over the active storage mode period to calculate the total sensor sensitivity adjustment value at the end of the active storage mode (e.g., at insertion). Similarly, at insertion, sensor 110 can determine the time difference between the manufacture of sensor 110 (capable of being written to memory 5030 of ASIC 5000) or sensing hardware 5060 and adjust the sensor sensitivity or other calibration features according to one or more known decay rates or formulas.

[0260] Additionally, for illustrative purposes and not for limitation, as illustrated herein, sensor sensitivity adjustment can be responsible for other sensor conditions such as sensor drift. Sensor sensitivity adjustment can be hard-coded into sensor 110 during manufacturing, for example, based on an estimate of the average degree of sensor drift in the case of sensor drift. Sensor 110 can use a calibration function having time-varying functions for sensor offset and gain, which can be responsible for drift over the duration of sensor wear. Thus, sensor 110 can use a function to convert interstitial current into interstitial glucose, which uses a device condition function describing the drift of sensor 110 over time, and which can represent sensor sensitivity and, when combined with a glucose curve baseline, can be device-specific. The function responsible for sensor sensitivity and drift can improve the accuracy of sensor 110 over the duration of wear without involving user calibration.

[0261] Q. Exemplary model-based analyte measurement

[0262] Sensor 110 detects raw measurements from sensing hardware 5060. Processing on the sensor can be performed, for example, by one or more models trained to understand the raw measurements. The model can be a machine learning model trained off-device that detects, predicts, or understands the raw measurements to detect, predict, or understand the level of one or more analytes. Additional trained models can operate on the output of the machine learning model, which is trained to interact with the raw measurements. For example, the model can be used to detect, predict, or recommend events based on the type of analyte detected by sensing hardware 5060 and the raw measurements. Events can include the start or completion of a physical activity, eating, administering medical treatment or medication, emergency health events, and other events of a similar nature.

[0263] The model can be provided to sensor 110, data receiving device 120, or multi-target data receiving device 130 during manufacturing or during firmware or software updates. The model can be refined periodically, for example by the manufacturer of sensor 110 or the operator of analyte monitoring system 100 based on data received from sensor 110 and data receiving devices for individual users or a total of multiple users. In some embodiments, sensor 110 includes sufficient computing components to aid in further training or refining the machine learning model, such as based on the unique characteristics of the users to whom sensor 110 is attached. The machine learning model can include, for example, but not limited to, models trained using or encompassing the following: decision tree analysis, gradient boosting, ADA boosting, artificial neural networks and their variants, linear discriminant analysis, nearest neighbor analysis, support vector machines, supervised or unsupervised classification, etc. In addition to machine learning models, the model can also include algorithm- or rule-based models. After receiving data from sensor 110 (or other downstream devices), model-based processing can be performed by other devices, including data receiving device 120 or multi-target data receiving device 130.

[0264] R. Exemplary Alarm Characteristics

[0265] The data transmitted between sensor 110 and data receiving device 120 may include raw or processed measurements. The data transmitted between sensor 110 and data receiving device 120 may also include alarms or notifications for display to a user. Data receiving device 120 may display or transmit notifications to a user based on raw or processed measurements, or may display alarms upon receipt from sensor 110. Alarms that can be triggered for display to a user include those based on: direct analysis of a value (e.g., a single reading exceeding or failing to meet a threshold), analysis of a value trend (e.g., an average reading exceeding or failing to meet a threshold over a set time period; slope); analysis of a value prediction (e.g., an algorithmic calculation based on the analysis of a value exceeding or failing to meet a threshold), sensor alerts (e.g., detection of a possible fault), communication alerts (e.g., a continuous threshold period of no communication between sensor 110 and data receiving device 120; an unknown device attempting or failing to initiate a communication dialogue with sensor 110), reminders (e.g., a reminder to charge data receiving device 120; a reminder to take medication or perform other activities), and other alerts of a similar nature. For illustrative purposes and not as a limitation, as illustrated herein, the alarm parameters described herein may be user-configurable or fixed during manufacturing, or a combination of user-configurable and user-unconfigurable parameters.

[0266] S. Exemplary electrode construction

[0267] The characteristic is that the sensor configuration, designed for detecting a single active region of a corresponding individual analyte, can use either a two-electrode or three-electrode detection mode, as described herein. Figures 18A-18C Further description. The feature is a sensor configuration for detecting two distinct active regions of a separate analyte on separate working electrodes or on the same working electrode, as described below. Figure 19A-21C Described separately. Sensor constructions with multiple working electrodes are particularly advantageous for incorporating two different active regions in the same sensor tail, because it is easier to determine the signal contribution from each active region.

[0268] In the case where a single working electrode exists in the analyte sensor, a three-electrode sensor configuration can include a working electrode, a counter electrode, and a reference electrode. A corresponding two-electrode sensor configuration can include a working electrode and a second electrode, wherein the second electrode can serve as both a counter electrode and a reference electrode (i.e., a counter / reference electrode). The electrodes can be at least partially stacked (layered) and / or laterally spaced at the sensor tail. Suitable sensor configurations can be substantially flat or substantially cylindrical. In any sensor configuration disclosed herein, the electrodes can be electrically isolated from each other by a dielectric material or similar insulator.

[0269] The characteristic feature is that the analyte sensor with multiple working electrodes can similarly include at least one additional electrode. In the presence of one additional electrode, said additional electrode can serve as a counter / reference electrode for each of the multiple working electrodes. In the presence of two additional electrodes, one of said additional electrodes can serve as a counter electrode for each of the multiple working electrodes, while the other of said additional electrodes can serve as a reference electrode for each of the multiple working electrodes.

[0270] Figure 18A A diagram illustrating an exemplary two-electrode analyte sensor configuration that may be used in this disclosure. As shown, the analyte sensor 200 includes a substrate 30212 disposed between a working electrode 214 and a counter / reference electrode 30216. Alternatively, the working electrode 214 and the counter / reference electrode 30216 may be located on the same side of the substrate 30212, with a dielectric material (configuration not shown) interposed therebetween. An active region 218 is disposed as at least one layer on at least a portion of the working electrode 214. The active region 218 may comprise multiple spots or a single spot configured for detecting analytes (e.g., ketones), as discussed further herein. In some embodiments, the active region 218 includes an enzyme system comprising NADH oxidase and β-hydroxybutyrate dehydrogenase.

[0271] Still refer to Figure 18A Membrane 220 covers at least the active region 218. In some embodiments, membrane 220 may also cover some or all of the working electrode 214 and / or the counter / reference electrode 30216, or the entire analyte sensor 200. One or both sides of the analyte sensor 200 may be covered by membrane 220. Membrane 220 may comprise one or more polymer membrane materials that have the ability to restrict the analyte flux to the active region 218 (i.e., membrane 220 is a mass transport-limiting membrane with some permeability to the analyte, such as a ketone). As disclosed herein and further described below, in certain sensor configurations, membrane 220 may be crosslinked with a branched crosslinking agent. For example, but not limited to, membrane 220 may be crosslinked with a branched glycidyl ether. The composition and thickness of membrane 220 may be varied to promote the flux of the desired analyte (e.g., a ketone) to the active region 218, thereby providing the desired signal strength and stability. The analyte sensor 200 can be used to test analytes by any of the following electrochemical detection techniques: coulometric, galvanometric, voltammetric, or potentiometric.

[0272] In some embodiments, one or more films are deposited on an exposed electroactive surface, such as the platinum surface of a working electrode, including interfering regions and mass transport limiting films. For example, but not limited to, interfering regions can be disposed on the working electrode, active regions can be disposed on the interfering regions, and mass transport limiting films can be disposed on the active regions.

[0273] Figure 18B and 18C A diagram illustrating an exemplary three-electrode analyte sensor construction is shown, which is also compatible with its use in this disclosure. The three-electrode analyte sensor construction can be similar to... Figure 18A The exceptions shown for analyte sensors 201 and 202 are those that include an additional electrode 217. Figure 18B and 18C With the additional electrode 217 present, the counter / reference electrode 30216 can act as either a counter electrode or a reference electrode, while the additional electrode 217 performs another electrode function not otherwise explained. The working electrode 214 continues to perform its original function. The additional electrode 217 can be disposed on the working electrode 214 or electrode 30216, with a dielectric material spacer layer between them. For example, but not limited to, such as... Figure 18B The dielectric layers 219a, 219b, and 219c separate electrodes 214, 30216, and 217 from each other and provide electrical isolation. Alternatively, at least one of electrodes 214, 30216, and 217 can be located on the opposite side of the substrate 30212, as... Figure 18C As shown. Thus, in some embodiments, electrode 214 (working electrode) and electrode 30216 (counter electrode) can be located on opposite surfaces of substrate 30212, wherein electrode 217 (reference electrode) is located on one of electrodes 214 or 30216 and spaced apart from it by a dielectric material. A reference material layer 30230 (e.g., Ag / AgCl) can be present on electrode 217, wherein the location of the reference material layer 30230 is not limited. Figure 18B and 18C Those described in [the text]. As shown in [the text]. Figure 18A The active region 218 (for detecting ketones) in sensor 200, analyte sensors 201 and 202 can comprise multiple spots or a single spot. Additionally, analyte sensors 201 and 202 can be used to test analytes via any of the following electrochemical detection techniques: coulometric, galvanometric, voltammetric, or potentiometric.

[0274] Similar to analyte sensor 200, in analyte sensors 201 and 202, membrane 220 can also cover active region 218 and other sensor components, thereby acting as a mass transport limiting membrane. In some embodiments, additional electrode 217 can be covered by membrane 220. Although Figure 18B and 18C Electrodes 214, 30216, and 217 have been described as being covered by film 220. It should be understood that in some embodiments only the working electrode 214 is covered. Furthermore, the thickness of the film 220 for each of electrodes 214, 30216, and 217 can be the same or different. This is as is seen in a two-electrode analyte sensor configuration. Figure 18A),exist Figure 18B and 18C In the sensor construction, the membrane 220 can cover one or both sides of the analyte sensors 201 and 202, or it can cover the entire analyte sensors 201 and 202. Accordingly, shown in Figure 18B and 18C The three-electrode sensor configuration should be understood as not being limited to the embodiments disclosed herein, wherein alternative electrode and / or layer configurations are also within the scope of this disclosure.

[0275] Figure 19A The exemplary configuration of the display sensor 203 has a single working electrode on which two different active regions are arranged. Figure 19A similar Figure 18A An exception is the presence of two active regions on the working electrode 214: a first active region 218a and a second active region 218b, which respond to different analytes and are laterally spaced from each other on the surface of the working electrode 214. Active regions 218a and 218b can comprise multiple sites or a single site configured for detecting each analyte. The composition of the membrane 220 can vary or be identical in active regions 218a and 218b. The first active region 218a and the second active region 218b can be configured to detect their respective analytes at different working electrode potentials, as discussed further below. In some embodiments, either or both of active regions 218a and 218b can be configured to detect ketones, for example, by using an enzyme system comprising NADH oxidase and β-hydroxybutyrate dehydrogenase. In some embodiments, only one active region of 218a and 218b is configured to detect ketones, for example, by using an enzyme system comprising NADH oxidase and β-hydroxybutyrate dehydrogenase. In some embodiments, another active region is configured to detect a second analyte, such as lactic acid, glucose, creatinine, and / or oxygen. In some embodiments, the second analyte is glucose.

[0276] Figure 19B and 19C Cross-sectional diagrams of exemplary three-electrode sensor configurations of sensors 204 and 205 are shown, each characterized by a single working electrode having a first active region 218a and a second active region 218b disposed thereon. Figure 19B and 19C Similar in other respects Figure 18B and 18C And one can better understand them by referring to them. For example... Figure 19A The composition of the membrane 220 in active regions 218a and 218b can vary or be the same.

[0277] An exemplary sensor configuration having multiple working electrodes, particularly two working electrodes, is described in further detail with reference to FIG4-21C. Although the following description primarily relates to a sensor configuration with two working electrodes, it should be recognized that more than two working electrodes can be incorporated by extending the disclosure herein. Additional working electrodes can be used to endow the analyte sensor with additional sensing capabilities beyond just the first and second analytes, for example, for detecting a third and / or fourth analyte.

[0278] Figure 4 shows a cross-sectional view of an exemplary analyte sensor configuration with two working electrodes (a reference electrode and a counter electrode), compatible with use in the disclosure herein. As shown, the analyte sensor 300 includes working electrodes 304 and 306 disposed on opposite surfaces of a substrate 302. A first active region 310a is disposed on the surface of the working electrode 304, while a second active region 310b is disposed on the surface of the working electrode 306. A counter electrode 320 is electrically isolated from the working electrode 304 by a dielectric layer 322, while a reference electrode 321 is electrically isolated from the working electrode 306 by a dielectric layer 323. Outer dielectric layers 330 and 332 are located on the reference electrode 321 and the counter electrode 320, respectively. According to various embodiments, a membrane 340 is capable of covering at least the active regions 310a and 310b, wherein other components of the analyte sensor 300 or the entire analyte sensor 300 may also optionally be covered by the first membrane portion 340a and / or the second membrane portion 340b. Furthermore, membrane 340 can be continuous but vary in composition within the first membrane portion 340a and the second membrane portion 340b (i.e., on the active regions 310a and 310b) to provide different permeability values ​​for differentially adjusting analyte flux at various locations. For example, different membrane formulations can be sprayed and / or printed onto opposite surfaces of the analyte sensor 300. Impregnation coating techniques can also be suitable, particularly for depositing at least a portion of the bilayer membrane onto one of the active regions 310a and 310b. Accordingly, according to specific embodiments of this disclosure, one of the first membrane portion 340a and the second membrane portion 340b can comprise a bilayer membrane while the other of the first membrane portion 340a and the second membrane portion 340b can comprise a single membrane polymer. Similar to analyte sensors 200, 201, and 202, analyte sensor 300 can be operated by any coulometric, current, voltammetric, or potentiochemical detection technique for testing ketones (and / or a second analyte). In some embodiments, the analyte sensor can include more than one membrane 340, such as two or more membranes. For example, but not limited to, the analyte sensor can include a membrane covering one or more active regions, such as 310a and 310a, and an additional membrane covering the entire sensor, such as... Figure 20As shown. In some embodiments, either or both of active regions 310a and 310b can be configured to detect ketones, for example, by using an enzyme system comprising NADH oxidase and β-hydroxybutyrate dehydrogenase. In some embodiments, only one active region of 310a and 310b is configured to detect ketones, for example, by using an enzyme system comprising NADH oxidase and β-hydroxybutyrate dehydrogenase. In some embodiments, the other active region is configured to detect a second analyte. In some embodiments, the second analyte is glucose.

[0279] It has multiple working electrodes and is different from Figure 20 The alternative sensor configuration shown can be characterized by having counter / reference electrodes instead of separate counter and reference electrodes 320, 321, and / or by having a different layer and / or film arrangement than those explicitly described. For example, but not limited to, the positioning of the counter electrode 320 and reference electrode 321 can be... Figure 20 The descriptions in the text are reversed. Furthermore, working electrodes 304 and 306 do not necessarily require... Figure 20 The arrangement shown is located on the opposite side of substrate 302.

[0280] While suitable sensor constructions can feature substantially planar electrodes, it should be recognized that sensor constructions featuring non-planar electrodes can be advantageous and particularly suitable for the purposes disclosed herein. In particular, substantially cylindrical electrodes arranged concentrically relative to each other can facilitate the deposition of mass transport-limiting films, as described below. Especially, concentric working electrodes spaced apart along the length of the sensor tail can facilitate film deposition through successive dip-coating operations, in a manner similar to those described above for substantially planar sensor constructions. Figures 21A-21C The display features are shown in a perspective view of an analyte sensor with two working electrodes arranged concentrically relative to each other. It should be recognized that a sensor configuration with a concentric electrode arrangement but lacking a second working electrode is also possible in this disclosure.

[0281] Figure 21AA perspective view showing an exemplary sensor configuration is displayed, in which a plurality of electrodes are substantially cylindrical and concentrically arranged around a central substrate. As shown, the analyte sensor 400 includes a central substrate 402 around which all electrodes and a dielectric layer are arranged concentrically. In particular, a working electrode 410 is disposed on the surface of the central substrate 402, and a dielectric layer 412 is disposed on a portion of the working electrode 410 distal to the sensor tip 404. A working electrode 420 is disposed on the dielectric layer 412, and a dielectric layer 422 is disposed on a portion of the working electrode 420 distal to the sensor tip 404. A counter electrode 430 is disposed on the dielectric layer 422, and a dielectric layer 432 is disposed on a portion of the counter electrode 430 distal to the sensor tip 404. A reference electrode 440 is disposed on the dielectric layer 432, and a dielectric layer 442 is disposed on a portion of the reference electrode 440 distal to the sensor tip 404. Thus, the exposed surfaces of the working electrode 410, working electrode 420, counter electrode 430 and reference electrode 440 are spaced apart from each other along the longitudinal axis B of the analyte sensor 400.

[0282] Also refer to Figure 21A A first active region 414a and a second active region 414b, responding to different or the same analyte, are respectively disposed on the exposed surfaces of working electrodes 410 and 420, thereby allowing fluid contact for sensing. In some embodiments, either or both of active regions 414a and 414b can be configured to detect ketones, for example, by using an enzyme system comprising NADH oxidase and β-hydroxybutyrate dehydrogenase. In some embodiments, only one active region of 414a and 414b is configured to detect ketones, for example, by using an enzyme system comprising NADH oxidase and β-hydroxybutyrate dehydrogenase. In some embodiments, the other active region is configured to detect a second analyte. In some embodiments, the second analyte is glucose. Although active regions 414a and 414b are already... Figure 21A The description is of three discrete points, but it should be recognized that in alternative sensor constructions, there can be fewer or more than three points, forming a continuous layer including the active region.

[0283] exist Figure 21A In the sensor 400, the upper portion of the working electrodes 410 and 420 and the active regions 414a and 414b disposed thereon are covered by a membrane 450. Figure 21B This illustrates an alternative sensor configuration in which the entire sensor 401 is covered by a membrane 450. The membrane 450 may be identical or varied in composition in the active regions 414a and 414b. For example, the membrane 450 may comprise a bilayer covering the active region 414a and be a homogeneous membrane covering the active region 414b.

[0284] It should also be recognized that various electrodes in Figure 21A and 21BThe positions of the electrodes can differ from those explicitly depicted. For example, the positions of the counter electrode 430 and the reference electrode 440 can differ from those explicitly depicted. Figure 21A and 21B The construction described herein is the opposite. Similarly, the positions of the working electrodes 410 and 420 are not limited to those described herein. Figure 21A and 21B Those explicitly described in the text. Figure 21C Display relative Figure 21B The alternative sensor configuration shown includes a counter electrode 430 and a reference electrode 440 positioned closer to the sensor tip 404, and working electrodes 410 and 420 positioned further away from the sensor tip 404. Positioning the working electrodes 410 and 420 further away from the sensor tip 404 is advantageous because it provides a larger surface area for the deposition of active regions 414a and 414b (exemplarily shown in…). Figure 21C (Five discrete sensing points), thereby promoting increased signal strength in some cases. Similarly, the central substrate 402 can be omitted in any concentric sensor construction disclosed herein, where the innermost electrode can replace the layer supporting the subsequently deposited layer.

[0285] In some embodiments, the electrodes are wire electrodes. In some embodiments, the sensor tail includes a working electrode and a reference electrode spirally wound around a working electrode. In some embodiments, an insulator is disposed between the working electrode and the reference electrode. In some embodiments, a portion of the electrode is exposed to allow one or more enzymes to react with the analyte on the electrode, as described below. In some embodiments, each electrode is formed from a fine wire having a diameter of about 0.001 inches or less to about 0.010 inches or more. In some embodiments, the working electrode has a diameter of about 0.001 inches or less to about 0.010 inches or more, for example, about 0.002 inches to about 0.008 inches or about 0.004 inches to about 0.005 inches. In some embodiments, the electrodes are formed from a self-plated insulator, a plated wire, or a bulk conductive material. In some embodiments, the working electrode includes a wire forming a self-conductive material, such as platinum, platinum-iridium, palladium, graphite, gold, carbon, conductive polymers, alloys, etc. In some embodiments, the electrode can be formed using various fabrication techniques (e.g., monolithic metal processing, depositing metal onto a substrate, etc.), and the electrode can be formed as a self-plated metal wire (e.g., platinum-plated steel wire) or a monolithic metal (e.g., platinum wire). In some embodiments, the electrode is formed as a self-platinum-coated tantalum metal wire.

[0286] In some embodiments, the reference electrode, which can serve as a single reference electrode or as a dual reference and counter electrode, is formed of silver, silver / silver chloride, etc. In some embodiments, the reference electrode is arranged alongside and / or twisted around the working electrode. In some embodiments, the reference electrode is spirally wound around the working electrode. In some embodiments, the wire assembly can be coated or attached with an insulating material to provide insulating adhesion.

[0287] In some embodiments, additional electrodes can be included in the sensor tail section. Examples include, but are not limited to, a three-electrode system (working electrode, reference electrode, and counter electrode) and / or an additional working electrode (e.g., an electrode for detecting a second analyte). In some embodiments where the sensor includes two working electrodes, the two working electrodes can be arranged side-by-side, with a reference electrode arranged around them (e.g., spirally wrapped around two or more working electrodes). In some embodiments, the two or more working electrodes can extend parallel to each other. In some embodiments, the reference electrode coils around the working electrodes and extends distally towards the sensor tail section (i.e., the in vivo end). In some embodiments, the reference electrode extends (e.g., spirally) towards the exposed area of ​​the working electrodes.

[0288] In some embodiments, one or more working electrodes are spirally wound around a reference electrode. In some embodiments providing two or more working electrodes, the working electrodes can be formed in a double-helix, triple-helix, quadruple-helix, or other helical configuration along the length of the sensor tail (e.g., around the reference electrode, insulating rod, or other support structure). In some embodiments, the electrodes, such as two or more working electrodes, are coaxially formed. For example, but not limited to, all electrodes share the same central axis.

[0289] In some embodiments, the working electrode comprises a tube in which a reference electrode is arranged or coiled, with an insulator included therein. Alternatively, the reference electrode comprises a tube in which the working electrode is arranged or coiled, with an insulator included therein. In some embodiments, a polymer (e.g., insulating) rod is provided, wherein one or more electrodes (e.g., one or more electrode layers) are arranged (e.g., by electroplating). In some embodiments, a metal (e.g., steel or tantalum) rod or wire covered with an insulating material (described herein) is provided, on which one or more working and reference electrodes are arranged. For example, but not limited to, this disclosure provides a sensor, such as a sensor tail, comprising one or more tantalum wires, wherein platinum is arranged on a portion of the one or more tantalum wires to serve as a working electrode. In some embodiments, platinum-plated tantalum wires are covered with an insulating material, wherein the insulating material portion is covered with a silver / silver chloride composition to serve as a reference and / or counter electrode.

[0290] In some embodiments where an insulator is disposed on a working electrode (e.g., on a platinum electrode surface), a portion of the insulator can be peeled off or removed to expose the electroactive surface of the working electrode. For example, but not limited to, a portion of the insulator can be removed manually, by stimulated excimer laser, chemical etching, laser ablation, sandblasting, etc. Alternatively, a portion of the electrode can be masked before depositing the insulator to maintain the exposed electroactive surface. In some embodiments, the peeled and / or removed portion of the insulator can be about 0.1 mm (about 0.004 inches) or less in length to about 2 mm (about 0.078 inches) or more, for example, about 0.5 mm (about 0.02 inches) to about 0.75 mm (0.03 inches) in length. In some embodiments, the insulator is a non-conductive polymer. In some embodiments, the insulator comprises parylene, fluorinated polymers, polyethylene terephthalate, polyvinylpyrrolidone, polyurethane, polyimide, and other non-conductive polymers. In some embodiments, glass or ceramic materials can also be used in the insulating layer. In some embodiments, the insulator comprises parylene. In some embodiments, the insulator comprises polyurethane. In some embodiments, the insulator comprises polyurethane and polyvinylpyrrolidone.

[0291] The active region of the analyte sensor and several components of the membrane are further described below.

[0292] 2. Enzymes

[0293] The active regions of the analyte sensors disclosed herein can be configured to detect one or more analytes. In some embodiments, the analyte sensors of this disclosure can include more than one active region, wherein each active region is configured to detect the same analyte or different analytes. Non-limiting examples of analytes that can be detected by the analyte sensors of this disclosure include ketones, glucose, oxygen, creatinine, alcohols such as ethanol, and lactic acid. In some embodiments, the analyte is one or more ketones.

[0294] In some embodiments, the analyte sensor of this disclosure may include a ketone-responsive active region, a glucose-responsive active region, a lactate-responsive active region, a creatinine-responsive active region, an alcohol-responsive active region, or a combination thereof. In some embodiments, the ketone-responsive active region may include one or more enzymes for detecting ketones. In some embodiments, the glucose-responsive active region may include one or more enzymes for detecting glucose. In some embodiments, the lactate-responsive active region may include one or more enzymes for detecting lactate. In some embodiments, the creatinine-responsive active region may include one or more enzymes for detecting creatinine. In some embodiments, the alcohol-responsive active region may include one or more enzymes for detecting alcohols. In some embodiments, the active region may include an enzyme system comprising two or more enzymes that co-respond to the analyte.

[0295] In some embodiments, the analyte sensor of this disclosure includes at least one active region configured to detect ketones. Specific enzyme systems capable of detecting ketones are described in... Figure 22 In the described enzymatic reaction, β-hydroxybutyrate acts as a substitute for the ketones formed in the body. For example... Figure 22 As shown, the coenzyme pair can be used to detect ketones according to the present invention. For example, but not limited to, the coenzyme pair can include a dehydrogenase and an oxidase. In some embodiments, the dehydrogenase is β-hydroxybutyrate dehydrogenase. In some embodiments, the oxidase is NADH oxidase. The enzyme cofactors NAD+ and NADH help facilitate the detection of ketones as disclosed herein. Figure 22 The diagram illustrates a synergistic enzymatic reaction. In the presence of this synergistic enzyme pair in the ketone-responsive active region, β-hydroxybutyrate dehydrogenase (HBDH) is able to react β-hydroxybutyrate with oxidized nicotinamide adenine dinucleotide (NAD). + The oxygen is converted into acetoacetic acid and reduced nicotinamide adenine dinucleotide (NADH), respectively. NADH oxidase (NADHOx) then catalyzes the reaction of molecular oxygen and NADH to produce hydrogen peroxide and NAD+. Hydrogen peroxide can then be catalytically oxidized at the anode, i.e., the working electrode, according to the following reaction.

[0296] [1]

[0297] The electron transfer during this reaction provides the basis for ketone detection at the working electrode and eliminates the need for redox mediators. The obtained electrochemical signal can then be correlated with the amount of ketone initially present in the sample.

[0298] In some embodiments, the working electrode comprises a metal capable of oxidizing hydrogen peroxide. In some embodiments, the working electrode may comprise platinum, a platinum alloy, carbon, or a combination thereof. In some embodiments, the working electrode is a platinum electrode. In some embodiments, the working electrode may comprise a platinum-carbon mixture.

[0299] Ketone-sensing enzyme systems comprising β-hydroxybutyrate dehydrogenase and NADH oxidase offer several advantages over previously disclosed enzyme systems. For example, the enzyme system eliminates the need for electron transfer reagents such as redox mediators like osmium complexes. Furthermore, irreversible oxidation of NADH can be prevented at lower potentials. For instance, previously disclosed systems require applying a potential of approximately +0.7 V relative to an Ag / AgCl reference. At this potential, NADH can still be irreversibly oxidized, which is undesirable. As disclosed herein, potentials less than approximately +0.7 V relative to an Ag / AgCl reference, such as less than approximately +0.6 V, less than approximately +0.5 V, or less than approximately +0.4 V relative to an Ag / AgCl reference, are applied to the sensors (e.g., working electrodes or enzyme systems) of this disclosure. In some embodiments, the potential applied to the enzyme system of this disclosure is approximately +0.2 V to approximately +0.5 V relative to an Ag / AgCl reference, such as approximately +0.3 V to approximately +0.4 V relative to an Ag / AgCl reference. In some embodiments, the potential applied to the enzyme system of this disclosure is approximately +0.35 V relative to the Ag / AgCl reference. At this potential, NADH is not oxidized, for example, irreversibly oxidized.

[0300] In some embodiments, the analyte sensor of this disclosure may include a sensor tail comprising at least one working electrode and a ketone-responsive active region (e.g., active region 218 or 310a) disposed on the surface of the working electrode, wherein the ketone-responsive active region comprises an enzyme system comprising a dehydrogenase and an oxidase. In some embodiments, the enzyme system comprises β-hydroxybutyrate dehydrogenase and NADH oxidase. In some embodiments, the enzyme system substantially consists of β-hydroxybutyrate dehydrogenase and NADH oxidase. In some embodiments, the enzyme system consists of β-hydroxybutyrate dehydrogenase and NADH oxidase. In some embodiments, the enzyme system does not include superoxide dismutase.

[0301] In some embodiments, the ketone-responsive active region may comprise β-hydroxybutyrate dehydrogenase:NADH oxidase in ratios of about 40:1 to about 1:40, for example, about 35:1 to about 1:35, about 30:1 to about 1:30, about 25:1 to about 1:25, about 20:1 to about 1:20, about 15:1 to about 1:15, about 10:1 to about 1:10, about 9:1 to about 1:9, about 8:1 to about 1:8, about 7:1 to about 1:7, about 6:1 to about 1:6, about 5:1 to about 1:5, about 4:1 to about 1:4, about 3:1 to about 1:3, about 2:1 to about 1:2, about 2:1, or about 1:1. In some embodiments, the ketone-responsive active region may comprise β-hydroxybutyrate dehydrogenase:NADH oxidase in ratios of about 5:1 to about 1:5. In some embodiments, the ketone-responsive active region may comprise a β-hydroxybutyrate dehydrogenase:NADH oxidase ratio of about 3:1 to about 1:3. In some embodiments, the ketone-responsive active region may comprise a β-hydroxybutyrate dehydrogenase:NADH oxidase ratio of about 2:1 to about 1:2. In some embodiments, the ketone-responsive active region may comprise a β-hydroxybutyrate dehydrogenase:NADH oxidase ratio of about 2:1.

[0302] In some embodiments, the ketone-responsive active region may include one or more enzymes of an enzyme system, such as β-hydroxybutyrate dehydrogenase and / or NADH oxidase, in amounts of about 10% to about 80% by weight, for example, about 15% to about 75%, about 20% to about 70%, about 25% to about 65%, or about 30% to about 60% by weight. In some embodiments, the ketone-responsive active region may include two enzymes of an enzyme system, such as β-hydroxybutyrate dehydrogenase and NADH oxidase, in amounts of about 10% to about 80% by weight, for example, about 15% to about 75%, about 20% to about 70%, about 25% to about 65%, about 30% to about 60% by weight, about 20% to about 60%, or about 20% to about 50% by weight. In some embodiments, the ketone-responsive active region may include β-hydroxybutyrate dehydrogenase in amounts of about 10% to about 80% by weight, for example, about 15% to about 75%, about 20% to about 70%, about 25% to about 65%, or about 30% to about 60% by weight. In some embodiments, the ketone-responsive active region may include about 10% to about 80% by weight, for example, about 15% to about 75%, about 20% to about 70%, about 25% to about 65%, or about 30% to about 60% by weight of NADH oxidase.

[0303] In some embodiments, the ketone-responsive active region may include about 15% to about 35% by weight of an enzyme system, such as β-hydroxybutyrate dehydrogenase and / or NADH oxidase. In some embodiments, the ketone-responsive active region may include about 10% to about 50% by weight, for example, about 15% to about 45%, about 20% to about 40%, about 20% to about 35%, or about 20% to about 30% by weight of β-hydroxybutyrate dehydrogenase. In some embodiments, the ketone-responsive active region may include about 15% to about 35% by weight of β-hydroxybutyrate dehydrogenase. In some embodiments, the ketone-responsive active region may include about 10% to about 50% by weight, for example, about 15% to about 45%, about 20% to about 40%, about 20% to about 35%, or about 20% to about 30% by weight of NADH oxidase. In some embodiments, the ketone-responsive active region may include about 15% to about 35% by weight of NADH oxidase.

[0304] In some embodiments, the ketone-responsive active region may also include a stabilizer, for example, for stabilizing the enzyme. For example, but not limited to, the stabilizer may be albumin, such as serum albumin. Non-limiting examples of serum albumin include bovine serum albumin and human serum albumin. In some embodiments, the stabilizer is human serum albumin. In some embodiments, the stabilizer is bovine serum albumin. In some embodiments, the stabilizer may be catalase. In some embodiments, the ketone-responsive active region may include stabilizers in ratios of enzymes of an enzyme system, such as NADH oxidase and β-hydroxybutyrate dehydrogenase, of about 40:1 to about 1:40, for example, about 35:1 to about 1:35, about 30:1 to about 1:30, about 25:1 to about 1:25, about 20:1 to about 1:20, about 15:1 to about 1:15, about 10:1 to about 1:10, about 9:1 to about 1:9, about 8:1 to about 1:8, about 7:1 to about 1:7, about 6:1 to about 1:6, about 5:1 to about 1:5, about 4:1 to about 1:4, about 3:1 to about 1:3, about 2:1 to about 1:2, or about 1:1. In some embodiments, the ketone-responsive active region may include stabilizers in ratios of enzymes of an enzyme system, such as NADH oxidase and β-hydroxybutyrate dehydrogenase, of about 2:1 to about 1:2. In some embodiments, the ketone-responsive active region may include a stabilizer in the following ratio: NADH oxidase: about 40:1 to about 1:40, for example about 35:1 to about 1:35, about 30:1 to about 1:30, about 25:1 to about 1:25, about 20:1 to about 1:20, about 15:1 to about 1:15, about 10:1 to about 1:10, about 9:1 to about 1:9, about 8:1 to about 1:8, about 7:1 to about 1:7, about 6:1 to about 1:6, about 5:1 to about 1:5, about 4:1 to about 1:4, about 3:1 to about 1:3, about 2:1 to about 1:2, or about 1:1. In some embodiments, the ketone-responsive active region may include a stabilizer in the following ratio: NADH oxidase: about 2:1 to about 1:2. In some embodiments, the ketone-responsive active region may include a stabilizer in the following ratio: β-hydroxybutyrate dehydrogenase: about 40:1 to about 1:40, for example about 35:1 to about 1:35, about 30:1 to about 1:30, about 25:1 to about 1:25, about 20:1 to about 1:20, about 15:1 to about 1:15, about 10:1 to about 1:10, about 9:1 to about 1:9, about 8:1 to about 1:8, about 7:1 to about 1:7, about 6:1 to about 1:6, about 5:1 to about 1:5, about 4:1 to about 1:4, about 3:1 to about 1:3, about 2:1 to about 1:2, or about 1:1. In some embodiments, the ketone-responsive active region may include a stabilizer in the following ratio: β-hydroxybutyrate dehydrogenase: about 2:1 to about 1:2.In some embodiments, the ketone-responsive active region may include about 10% to about 50% by weight, for example, about 15% to about 45%, about 20% to about 40%, about 20% to about 35%, or about 20% to about 30% by weight of a stabilizer. In some embodiments, the ketone-responsive active region may include about 15% to about 35% by weight of a stabilizer.

[0305] In some embodiments, the ketone-responsive active region may further comprise a cofactor (or a derivative thereof) of an enzyme of the enzyme system disclosed herein. Non-limiting examples of cofactors include NADH or NADPH or derivatives thereof. In some embodiments, the cofactor is NADH or a derivative thereof. In some embodiments, the ketone-responsive active region may comprise a cofactor in the following ratios: NADH oxidase: about 40:1 to about 1:40, for example about 35:1 to about 1:35, about 30:1 to about 1:30, about 25:1 to about 1:25, about 20:1 to about 1:20, about 15:1 to about 1:15, about 10:1 to about 1:10, about 9:1 to about 1:9, about 8:1 to about 1:8, about 7:1 to about 1:7, about 6:1 to about 1:6, about 5:1 to about 1:5, about 4:1 to about 1:4, about 3:1 to about 1:3, about 2:1 to about 1:2, or about 1:1. In some embodiments, the ketone-responsive active region may include cofactors in the following ratios: NADH oxidase: about 2:1 to about 1:2. In some embodiments, the ketone-responsive active region may include cofactors in the following ratios: β-hydroxybutyrate dehydrogenase: about 40:1 to about 1:40, for example about 35:1 to about 1:35, about 30:1 to about 1:30, about 25:1 to about 1:25, about 20:1 to about 1:20, about 15:1 to about 1:15, about 10:1 to about 1:10, about 9:1 to about 1:9, about 8:1 to about 1:8, about 7:1 to about 1:7, about 6:1 to about 1:6, about 5:1 to about 1:5, about 4:1 to about 1:4, about 3:1 to about 1:3, about 2:1 to about 1:2, or about 1:1. In some embodiments, the ketone-responsive active region may include cofactors in the following ratios: β-hydroxybutyrate dehydrogenase: about 2:1 to about 1:2. In some embodiments, the ketone-responsive active region may include about 10% to about 50% by weight, for example, about 15% to about 45%, about 20% to about 40%, about 20% to about 35%, or about 20% to about 30% by weight of cofactors. In some embodiments, the ketone-responsive active region may include about 15% to about 35% by weight of cofactors. In some embodiments, cofactors such as NADH may be physically retained within the ketone-responsive active region. For example, but not limited to, a membrane coating the ketone-responsive active region may help retain the cofactors within the ketone-responsive active region while still allowing sufficient ketone to diffuse inwards to allow for its detection.

[0306] In some embodiments, the ketone-responsive active region is disposed on a portion of the working electrode. For example, but not limited to, the ketone-responsive active region is disposed in the form of spots on a portion of the working electrode, such as two or more spots on the working electrode. In some embodiments, the ketone-responsive active region is disposed in a slotted manner on a portion of the working electrode. In some embodiments, the ketone-responsive active region is disposed along the entire length of the working electrode or in a continuous manner on the working electrode. In some embodiments, the ketone-responsive active region has a diameter of approximately 0.01 mm. 2 To approximately 2.0 mm 2 For example, about 0.1 mm 2 To approximately 1.0 mm 2 or approximately 0.2 mm 2 To approximately 0.5 mm 2 The area.

[0307] In some embodiments, the analyte sensor of this disclosure can include a second active region for detecting analytes other than ketones, for example on the same working electrode as the ketone-responsive active region or on a second working electrode. In some embodiments, the second active region is a glucose-responsive active region, a lactate-responsive active region, a creatinine-responsive active region, or an alcohol-responsive active region.

[0308] In some embodiments, the second active region of the analyte sensor of this disclosure may include one or more enzymes for glucose detection. For example, but not limited to, the analyte sensor of this disclosure may include an active region (e.g., a second active region) containing one or more enzymes for glucose detection, for example, disposed on a second working electrode. In some embodiments, the analyte sensor may include an active site containing glucose oxidase and / or glucose dehydrogenase for glucose detection. In some embodiments, glucose can be detected using glucose oxidase present in the second active region, which produces H2O2 as a product. H2O2 reacts with an electrochemically reactive surface of the second working electrode, such as a platinum surface, to generate a detectable current.

[0309] In some embodiments, the second active region may include one or more enzymes for detecting lactate. For example, but not limited to, the analyte sensor of this disclosure may include an active region (e.g., a second active region) containing one or more enzymes, such as an enzyme system, for detecting lactate, for example, disposed on a second working electrode. In some embodiments, the analyte sensor may include an active site containing lactate dehydrogenase and / or lactate oxidase.

[0310] In some embodiments, the second enzyme-responsive active region of the analyte sensor of this disclosure (e.g., present on the second working electrode) can include one or more enzymes for the detection of alcohols. For example, but not limited to, the analyte sensor of this disclosure can include an active region (e.g., a second active region) containing one or more enzymes, such as an enzyme system, for the detection of alcohols, for example, disposed on the second working electrode. In some embodiments, the analyte sensor can include an active site containing an alcohol dehydrogenase.

[0311] In some embodiments, the second enzyme-responsive active region of the analyte sensor of this disclosure (e.g., present on the second working electrode) can include one or more enzymes for detecting creatinine. For example, but not limited to, the analyte sensor of this disclosure can include an active region (e.g., a second active region) containing one or more enzymes, such as an enzyme system, for detecting creatinine, for example, disposed on the second working electrode. In some embodiments, the analyte sensor can include an active site containing an amidolytic enzyme, a creatine amidolytic enzyme, and / or a sarcosine oxidase.

[0312] In some embodiments, the analyte sensor can include two working electrodes, for example, a first active region disposed on a first working electrode and a second active region disposed on a second working electrode. In some embodiments, the first and second active regions are configured to detect different analytes. In some embodiments, the first active region is configured to detect ketones. In some embodiments, the second active region is configured to detect analytes other than ketones, such as glucose, creatinine, lactate, and / or alcohols. For example, but not limited to, the analyte sensor disclosed herein can be characterized by a ketone-responsive active region on the surface of a first working electrode and second active regions, such as glucose-responsive active regions, configured to detect different analytes on different working electrodes, such as the surface of a second working electrode. In some embodiments, the analyte sensor can include a sensor tail having at least a first and a second working electrode, a ketone-responsive active region disposed on the surface of the first working electrode, and a glucose-responsive active region comprising a glucose-responsive enzyme disposed on the surface of the second working electrode. For example, but not limited to, when the sensor is configured to detect two or more analytes, the detection of each analyte can include applying potentials separately to each working electrode to obtain separate signals from each analyte. The signals obtained from each analyte can then be correlated with the analyte concentration using a calibration curve or function, or by using a lookup table. In some embodiments, the correlation between the analyte signal and the analyte concentration can be performed using a processor.

[0313] In some other analyte sensor configurations, a first active region and a second active region can be arranged on a single working electrode. A first signal can be obtained, for example, from the first active region at a low potential, and a second signal containing signal contributions from both active regions can be obtained at a higher potential. Subtracting the first signal from the second signal allows determination of the signal contribution caused by the second analyte. The signal contributions from each analyte can then be correlated with the analyte concentration in a manner similar to those described for sensor configurations with multiple working electrodes. In some embodiments, where a ketone-responsive active region and a second active region configured to detect different analytes, such as a glucose-responsive active region, are arranged on a single working electrode in this manner, one of the active regions can be configured such that it can be interrogated separately to facilitate the detection of each analyte. For example, the ketone-responsive active region or the glucose-responsive active region can generate signals independently of the other active region.

[0314] It should also be recognized that the sensitivity (output current) of the analyte sensor to each analyte can be varied by changing the coverage (area or size) of the active region, the area ratio of the active regions to each other, and the characteristics, thickness, and / or composition of the mass transport limiting membrane covering the active region. These parameters can be readily changed by those skilled in the art once they have obtained the benefits disclosed herein.

[0315] 3. Redox mediators

[0316] In some embodiments, the analyte sensors disclosed herein may include electron transfer reagents. As discussed above, electron transfer reagents are not included in the ketone-responsive active region due to the composition of the ketone-responsive active region in any exemplary sensor construction disclosed herein, such as the enzyme composition and the working electrode composition. For example, but not limited to, ketone-responsive active regions comprising enzyme systems (including β-hydroxybutyrate dehydrogenase and NADH oxidase) do not include electron transfer reagents, such as redox mediators, such as osmium redox mediators.

[0317] In some embodiments, the active region in the analyte sensor of this disclosure, configured to detect another analyte such as glucose, may include an electron transfer reagent. For example, but not limited to, the analyte sensor of this disclosure may include a sensor tail having at least a first working electrode and a second working electrode, a ketone-responsive active region comprising β-hydroxybutyrate dehydrogenase and NADH oxidase disposed on the surface of the first working electrode, and a glucose-responsive active region comprising a glucose-responsive enzyme and an electron transfer reagent disposed on the surface of the second working electrode. In some embodiments, the first working electrode comprises platinum and the ketone-responsive active region does not include an electron transfer reagent. In some embodiments, the ketone-responsive active region generates hydrogen peroxide in the presence of ketones, which is directly oxidized on the platinum-containing working electrode surface without the need for an electron transfer reagent, for example, generating a detectable current related to the ketone concentration in the sample. Alternatively or additionally, in some embodiments, the second working electrode comprises platinum and the glucose-responsive active region disposed on the second working electrode does not include an electron transfer reagent. In some implementations, the glucose-responsive active region generates hydrogen peroxide in the presence of glucose, which is directly oxidized on the surface of a platinum-containing working electrode without the need for electron transfer reagents, such as generating a detectable current related to the glucose concentration in the sample.

[0318] Suitable electron transfer reagents can facilitate electron transport to the adjacent working electrode after the analyte undergoes an enzymatic redox reaction in the corresponding active region, thereby generating a current indicating the presence of a specific analyte. The amount of current generated is proportional to the amount of analyte present.

[0319] In some embodiments, suitable electron transfer agents may comprise electroreducible and electrooxidizable ions, complexes, or molecules (e.g., quinones) having a redox potential of several hundred millivolts above or below the standard mercurous chloride electrode (SCE) redox potential. In some embodiments, redox mediators may comprise osmium complexes and other transition metal complexes, such as those described in US Patent Nos. 6,134,461 and 6,605,200, all of which are incorporated herein by reference. Additional examples of suitable redox mediators include those described in US Patent Nos. 6,736,957, 7,501,053, and 7,754,093, the respective disclosures of which are also incorporated herein by reference. Other examples of suitable redox mediators include metal compounds or complexes of ruthenium, osmium, iron (e.g., ferrocene or hexacyanoferrate), or cobalt, such as those comprising their metallocene compounds. Suitable ligands for metal complexes can also include, for example, bidentate or higher-dentate ligands such as bipyridine, biimidazole, phenanthrene, or pyridyl (imidazole). Other suitable bidentate ligands can include, for example, amino acids, oxalic acid, acetylacetone, diaminoalkanes, or o-diaminoaromatics. Any combination of monodentate, bidentate, tridentate, tetradentate, or higher-dentate ligands can be present in metal complexes to achieve a fully coordinated sphere.

[0320] In some embodiments, the electron transfer agents disclosed herein can contain suitable functional groups to facilitate covalent bonding with a polymer (also referred to herein as a polymer backbone) in the active region, as discussed further below. For example, but not limited to, the electron transfer agents used in this disclosure can include polymer-bound electron transfer agents. Suitable non-limiting examples of polymer-bound electron transfer agents include those described in US Patent Nos. 8,444,834, 8,268,143, and 6,605,201, the entire disclosure of which is incorporated herein by reference. In some embodiments, the electron transfer agent is a bidentate osmium complex bound to a polymer described herein, such as the polymer backbone described in Section 4 below. In some embodiments, the polymer-bound electron transfer agent shown in Figure 3 of US Patent No. 8,444,834 can be used in the sensors of this disclosure.

[0321] 4. Polymer backbone

[0322] In some embodiments, one or more active sites for facilitating analyte detection may comprise a polymer covalently bound to an enzyme and / or redox mediator. Any suitable polymer backbone may be present in the active region for facilitating analyte detection via covalent bonding to an enzyme and / or redox mediator. Non-limiting examples of suitable polymers in the active region include polyvinylpyridines such as poly(4-vinylpyridine) and / or poly(2-vinylpyridine), and polyvinylimidazoles such as poly(N-vinylimidazole) and poly(1-vinylimidazole), or copolymers thereof, where, for example, quaternized pyridine groups act as attachment sites for redox mediators or enzymes. Exemplary copolymers suitable for inclusion in the active region include those containing monomer units such as styrene, acrylamide, methacrylamide, or acrylonitrile. In some embodiments, polymers that may be present in the active region include polyurethanes or copolymers thereof, and / or polyvinylpyrrolidone. In some embodiments, the polymers that can be present in the active regions include, but are not limited to, those described in US Patent 6,605,200 (which is incorporated herein by reference in its entirety), such as poly(acrylic acid), styrene / maleic anhydride copolymer, methyl vinyl ether / maleic anhydride copolymer (GANTREZ polymer), poly(vinyl benzyl chloride), poly(allylamine), polylysine, poly(4-vinylpyridine) quaternized with carboxypentyl, and poly(sodium 4-styrene sulfonate). In some embodiments where the analyte sensor includes two active sites, the polymers in the active regions can be the same or different.

[0323] In some embodiments, the polymer is polyvinylpyridine or a copolymer thereof. In some embodiments, the polymer is a copolymer of vinylpyridine and styrene.

[0324] In some embodiments, when an enzyme system having multiple enzymes, including NADH oxidase, is present in a given active region, all of the multiple enzymes are covalently bonded to the polymer. In some other embodiments, only a portion of the multiple enzymes are covalently bonded to the polymer. For example, but not limited to, one or more enzymes in the enzyme system are covalently bonded to the polymer and at least one enzyme is non-covalently bound to the polymer, such that the non-covalently bonded enzyme is physically retained in the polymer. In some embodiments, β-hydroxybutyrate dehydrogenase and NADH oxidase are covalently bonded to the polymer in the ketone-responsive active region of the analyte sensor of this disclosure. In some embodiments, β-hydroxybutyrate dehydrogenase is covalently bonded to the polymer and NADH oxidase is non-covalently bound to the polymer. Alternatively, NADH oxidase is covalently bonded to the polymer and β-hydroxybutyrate dehydrogenase is non-covalently bound to the polymer. In some embodiments, NAD... +It can covalently bond to the polymer. In some embodiments, NAD+ does not covalently bond to the polymer. + In some embodiments where they are not covalently bonded, they can be physically retained within the ketone-responsive active region. In some embodiments, the film coating the ketone-responsive active region can help to transfer NAD+. + The membrane remains within the ketone-responsive active region while still allowing sufficient ketone to diffuse inward for detection. Suitable membrane polymers for coating the ketone-responsive active region are discussed further herein.

[0325] Alternatively or additionally, the active region, such as the ketone-responsive active region, does not include polyvinylpyridine or a copolymer of vinylpyridine and styrene. In some embodiments, one or more enzymes present in the active region can be immobilized in the active region using a crosslinking agent as described herein in the presence of a stabilizer. For example, but not limited to, one or more enzymes in the ketone-responsive active region of this disclosure, such as NADH oxidase and / or β-hydroxybutyrate dehydrogenase, can be immobilized in the active region using a crosslinking agent such as polyethylene glycol diglycidyl ether. In some embodiments, one or more enzymes in the ketone-responsive active region, such as NADH oxidase and / or β-hydroxybutyrate dehydrogenase, can be covalently bonded to a stabilizer in the active region using a crosslinking agent. In some embodiments, the stabilizer is serum albumin, such as bovine serum albumin (BSA).

[0326] In some embodiments, covalent bonding of one or more enzymes and / or redox mediators to polymers and / or stabilizers in a given active region can occur via a crosslinking agent introduced with a suitable crosslinking agent. Suitable crosslinking agents can include one or more crosslinkable functional groups, such as, but not limited to, vinyl, alkoxy, acetoxy, alkenoxy, oxime, amino, hydroxyl, cyano, halogen, acrylate / ester, epoxide, and isocyanate groups. In some embodiments, the crosslinking agent comprises one or more, two or more, three or more, or four or more (one or more, two or more, three or more, or four or more) epoxide groups. For example, but not limited to, crosslinking agents used in this disclosure can include one, two, three, and four ethylene oxides. In some embodiments, the crosslinking agent used to react with free amino groups in the enzyme (e.g., with free side-chain amines in lysine) can include crosslinking agents such as polyethylene glycol dibutyl ether, polypropylene glycol dimethyl ether, polyalkylene glycol allyl methyl ether, polyethylene glycol diglycidyl ether (PEGDGE) or other polyepoxides, cyanuric chloride, N-hydroxysuccinimide, imine esters, epichlorohydrin, or derivatives thereof. In some embodiments, the crosslinking agent is PEGDGE, which has, for example, an average molecular weight (M) of about 200 to 1,000, for example, about 400.n In some embodiments, the cross-linking agent is PEGDGE 400. In some embodiments, the cross-linking agent can be glutaraldehyde. Suitable cross-linking agents for reacting with free carboxylic acid groups in the enzyme can include, for example, carbodiimides. In some embodiments, the cross-linking of the enzyme with the polymer or stabilizer is generally an intermolecular cross-linking.

[0327] In some embodiments, the ketone-responsive active region may include cross-linking agents in the following ratios: one or more enzymes of an enzyme system, such as NADH oxidase and / or β-hydroxybutyrate dehydrogenase: about 40:1 to about 1:40, for example, about 35:1 to about 1:35, about 30:1 to about 1:30, about 25:1 to about 1:25, about 20:1 to about 1:20, about 15:1 to about 1:15, about 10:1 to about 1:10, about 9:1 to about 1:9, about 8:1 to about 1:8, about 7:1 to about 1:7, about 6:1 to about 1:6, about 5:1 to about 1:5, about 4:1 to about 1:4, about 3:1 to about 1:3, about 2:1 to about 1:2, or about 1:1. In some embodiments, the ketone-responsive active region may include cross-linking agents in the following ratios: one or more enzymes of an enzyme system, such as NADH oxidase and / or β-hydroxybutyrate dehydrogenase: about 5:1 to about 1:5. In some embodiments, the ketone-responsive active region may include cross-linking agents in a ratio of about 3:1 to about 1:3 for one or more enzymes of the enzyme system, such as NADH oxidase and / or β-hydroxybutyrate dehydrogenase. In some embodiments, the ketone-responsive active region may include cross-linking agents in a ratio of about 2:1 to about 1:2 for one or more enzymes of the enzyme system, such as NADH oxidase and / or β-hydroxybutyrate dehydrogenase. In some embodiments, the ketone-responsive active region may include about 5% to about 50% by weight of the cross-linking agent. In some embodiments, the ketone-responsive active region may include about 5% to about 20% by weight, for example, about 10% to about 15% by weight of the cross-linking agent.

[0328] 5. Quality transport restriction film

[0329] In some embodiments, the analyte sensor disclosed herein also includes an analyte-permeable membrane that covers at least one active region, such as a first active region and / or a second active region.

[0330] In some implementations, the membrane coating the analyte-responsive active region can act as a mass transport restriction membrane and / or improve biocompatibility. The mass transport restriction membrane can act as a diffusion restriction barrier, thereby reducing the mass transport rate of the analyte. For example, but not limited to, restricting the access of an analyte, such as a ketone, to the analyte-responsive active region with a mass transport restriction membrane can help prevent sensor overload (saturation), thereby improving detection efficiency and accuracy.

[0331] In some embodiments, the mass transport restriction membrane can be homogeneous and can be single-component (containing a single membrane polymer). Alternatively, the mass transport restriction membrane can be multi-component (containing two or more different membrane polymers). In some embodiments, the mass transport restriction membrane can comprise two or more layers, such as bilayer or trilayer membranes. In some embodiments, each layer can contain different polymers or different concentrations or thicknesses of the same polymer. In some embodiments, the ketone-responsive active region can be covered by a multilayer membrane, such as a bilayer membrane, while the second analyte-responsive active region can be covered by a single membrane. In some embodiments, the ketone-responsive active region can be covered by a multilayer membrane, such as a bilayer membrane, while the second analyte-responsive active region can be covered by a multilayer membrane, such as a bilayer membrane.

[0332] In some embodiments, the mass transport restriction film may comprise a crosslinked polymer containing heterocyclic nitrogen groups. In some embodiments, the mass transport restriction film may comprise a polyvinylpyridine-based polymer. Non-limiting examples of polyvinylpyridine-based polymers are disclosed in US Patent Publication No. 2003 / 0042137 (e.g., Formula 2b), the entire contents of which are incorporated herein by reference. In some embodiments, the mass transport restriction film may include polyvinylpyridine (e.g., poly(4-vinylpyridine) or poly(4-vinylpyridine)), polyvinylimidazole, polyvinylpyridine copolymers (e.g., copolymers of vinylpyridine and styrene), polyacrylates, polyurethanes, polyether polyurethanes, silicones, polytetrafluoroethylene, polyethylene-co-tetrafluoroethylene, polyolefins, polyesters, polycarbonates, bio-stabilized polytetrafluoroethylene, homopolymers, copolymers or trimers of polyurethanes, polypropylene, polyvinyl chloride, polyvinylidene fluoride, polybutylene terephthalate, polymethyl methacrylate, polyetheretherketone, fibrous polymers, polysulfones, and their block copolymers, including, for example, diblock, triblock, alternating, random and graft copolymers, or chemically related substances.

[0333] In some embodiments, the membranes used in this disclosure, such as one-component membranes, may comprise polyvinylpyridine (e.g., poly(4-vinylpyridine) and / or poly(2-vinylpyridine)). In some embodiments, the membranes used in this disclosure, such as one-component membranes, may comprise poly(4-vinylpyridine). In some embodiments, the membranes used in this disclosure, such as one-component membranes, may comprise copolymers of vinylpyridine and styrene. In some embodiments, the membrane may comprise a polyvinylpyridine-co-styrene copolymer. For example, but not limited to, the polyvinylpyridine-co-styrene copolymer used in this disclosure may comprise a polyvinylpyridine-co-styrene copolymer in which a portion of the pyridine nitrogen atoms are functionalized with a non-crosslinked polyethylene glycol tail and a portion of the pyridine nitrogen atoms are functionalized with alkyl sulfonic acid groups. In some embodiments, the derivatized polyvinylpyridine-co-styrene copolymer used as the membrane polymer may be polymer 10Q5 described in US Patent No. 8,761,857, the entire contents of which are incorporated herein by reference. In some embodiments, the polyvinylpyridine-based polymer has a molecular weight of about 50 Da to about 500 kDa.

[0334] In some embodiments, the membrane may comprise polymers, such as, but not limited to, poly(styrene co-maleic anhydride), dodecylamine, and poly(propylene glycol)-block-poly(ethylene glycol)-block-poly(propylene glycol) (2-aminopropyl ether), which are crosslinked with poly(propylene glycol)-block-poly(ethylene glycol)-block-poly(propylene glycol) di(2-aminopropyl ether); poly(N-isopropylacrylamide); copolymers of poly(ethylene oxide) and poly(propylene oxide); or combinations thereof.

[0335] In some embodiments, the membrane comprises a polyurethane membrane containing both hydrophilic and hydrophobic regions. In some embodiments, the hydrophobic polymeric component is polyurethane, polyurethane urea, or poly(ether-urethane-urea). In some embodiments, the polyurethane is a polymer prepared by the condensation reaction of a diisocyanate and a difunctional hydroxyl-containing substance. In some embodiments, the polyurethane urea is a polymer prepared by the condensation reaction of a diisocyanate and a difunctional amine-containing substance. In some embodiments, the diisocyanate used herein includes aliphatic diisocyanates, for example containing about 4 to about 8 methylene units; or diisocyanates containing a cyclic aliphatic moiety. Additional non-limiting examples of polymers capable of being used to produce membranes of the sensors disclosed herein include vinyl polymers, polyethers, polyesters, polyamides, inorganic polymers (e.g., polysiloxanes and polycarbosiloxanes), natural polymers (e.g., fibrous and protein-based substances), and mixtures (e.g., blends or layered structures) or combinations thereof. In some embodiments, the hydrophilic polymeric component is polyethylene oxide and / or polyethylene glycol. For example, but not limited to, the hydrophobic-hydrophilic copolymer component used in this disclosure is a polyurethane polymer containing about 10% to about 50%, for example, about 20% hydrophilic polyethylene oxide.

[0336] In some embodiments, the membrane comprises a silicone polymer / hydrophobic-hydrophilic polymer blend. In some embodiments, the hydrophobic-hydrophilic polymer used in the blend can be any suitable hydrophobic-hydrophilic polymer, such as, but not limited to, polyvinylpyrrolidone, polyhydroxyethyl methacrylate, polyvinyl alcohol, polyacrylate, polyethers such as polyethylene glycol or polypropylene oxide, and copolymers thereof, including, for example, diblock, triblock, alternating, random, comb-shaped, star-shaped, dendritic, and graft copolymers. In some embodiments, the hydrophobic-hydrophilic polymer is a copolymer of poly(ethylene oxide) (PEO) and poly(propylene oxide) (PPO). Non-limiting examples of PEO and PPO copolymers include PEO-PPO diblock copolymers, PPO-PEO-PPO triblock copolymers, PEO-PPO-PEO triblock copolymers, alternating block copolymers of PEO-PPO, random copolymers of ethylene oxide and propylene oxide, and blends thereof. In some embodiments, the copolymer can be substituted with hydroxyl substituents.

[0337] In some embodiments, hydrophilic or hydrophobic modifiers can be used to "fine-tune" the permeability of the resulting membrane to analytes such as ketones. In some embodiments, hydrophilic modifiers such as polyethylene glycol, hydroxyl or polyhydroxyl modifiers, and any combination thereof can be used to enhance the biocompatibility of the polymer or the resulting membrane.

[0338] In some embodiments where multiple active regions exist, the mass transport restriction film can coat each active region, including different options on different active regions, which can be achieved by sequential impregnation coating operations, thereby creating a bilayer film portion on the working electrode located closer to the sensor tip.

[0339] In some embodiments where multiple active regions exist, separate mass transport restriction films can cover each active region. For example, but not limited to, a mass transport restriction film can be disposed on a first active region, such as a ketone-responsive active region, while a separate second mass transport restriction film can cover a second active region, such as a glucose-responsive active region. In some embodiments, the two mass transport restriction films are spatially separated and do not overlap each other. In some embodiments, the first mass transport restriction film does not overlap with the second mass transport restriction film, and the second mass transport restriction film does not overlap with the first mass transport restriction film. In some embodiments, the first mass transport restriction film comprises a different polymer than the second mass transport restriction film. Alternatively, the first mass transport restriction film comprises the same polymer as the second mass transport restriction film. In some embodiments, the first mass transport restriction film comprises the same polymer as the second mass transport restriction film but comprises a different crosslinking agent.

[0340] In some embodiments, the composition of the mass transport restriction membrane disposed on an analyte sensor having two active regions can be the same or different in the positions where the mass transport restriction membrane covers the active regions. For example, but not limited to, the mass transport restriction membrane portion covering the ketone-responsive active region can be multi-component and / or the mass transport restriction membrane portion covering the second analyte-responsive region, such as the glucose-responsive active region, can be single-component. Alternatively, the mass transport restriction membrane portion covering the ketone-responsive active region can be single-component and / or the mass transport restriction membrane portion covering the second analyte-responsive region, such as the glucose-responsive active region, can be multi-component. In some embodiments, the mass transport restriction membrane covering the ketone-responsive active region can be single-component, and the mass transport restriction membrane covering the second analyte-responsive region, such as the glucose-responsive active region, can also be single-component. In some embodiments, the mass transport restriction membrane covering the ketone-responsive active region comprises a different polymer than the mass transport restriction membrane covering the second analyte-responsive region, such as the glucose-responsive active region.

[0341] In some embodiments of this disclosure, the ketone-responsive active region can be coated with a one-component membrane comprising polyvinylpyridine (e.g., poly(4-vinylpyridine)); while the second analyte-responsive region, such as the glucose-responsive active region, can be coated with a membrane comprising a polyvinylpyridine-co-styrene copolymer. In some embodiments, the membrane coating the second analyte-responsive region, such as the glucose-responsive active region, can also coat the membrane covering the ketone-responsive active region, thereby, for example, creating a bilayer membrane over the ketone-responsive active region. In some embodiments, the glucose-responsive active region can be coated with a membrane comprising polyurethane, polyurethane urea, or poly(ether-urethane-urea). In some embodiments, the glucose-responsive active region can be coated with a membrane comprising polyurethane.

[0342] In some embodiments of this disclosure, the ketone-responsive active region and the second analyte-responsive region, such as the glucose-responsive active region, can be coated with a membrane comprising a polyvinylpyridine-co-styrene copolymer. In some embodiments, the multicomponent membrane can be presented as a bilayer membrane or a homogeneous mixture of two or more membrane polymers. The homogeneous mixture can be deposited as follows: two or more membrane polymers are combined in solution, and then the solution is deposited on the working electrode. In some embodiments of this disclosure, the ketone-responsive active region can be coated with a multicomponent membrane comprising polyvinylpyridine and a polyvinylpyridine-co-styrene copolymer (or a derivative thereof) as a bilayer membrane or a homogeneous mixture, while the second analyte-responsive region, such as the glucose-responsive active region, can be coated with a membrane comprising a polyvinylpyridine-co-styrene copolymer (or a derivative thereof). In some embodiments of this disclosure, the ketone-responsive active region can be coated with a multi-component membrane comprising polyvinylpyridine and a polyvinylpyridine-co-styrene copolymer (or a derivative thereof) as a bilayer membrane, while the second analyte-responsive region, such as the glucose-responsive active region, can be coated with a single-component membrane comprising a polyvinylpyridine-co-styrene copolymer (or a derivative thereof).

[0343] Suitable copolymers of vinylpyridine and styrene (polyvinylpyridine-co-styrene copolymers) can have a styrene content ranging from about 0.01% to about 50% molar percentage, or about 0.05% to about 45% molar percentage, or about 0.1% to about 40% molar percentage, or about 0.5% to about 35% molar percentage, or about 1% to about 30% molar percentage, or about 2% to about 25% molar percentage, or about 5% to about 20% molar percentage. Substituted styrene can be used similarly and in similar amounts. Suitable copolymers of vinylpyridine and styrene can have a molecular weight of 5 kDa or more, or about 10 kDa or more, or about 15 kDa or more, or about 20 kDa or more, or about 25 kDa or more, or about 30 kDa or more, or about 40 kDa or more, or about 50 kDa or more, or about 75 kDa or more, or about 90 kDa or more, or about 100 kDa or more. In non-limiting examples, suitable copolymers of vinylpyridine and styrene can have molecular weights ranging from about 5 kDa to about 150 kDa, or about 10 kDa to about 125 kDa, or about 15 kDa to about 100 kDa, or about 20 kDa to about 80 kDa, or about 25 kDa to about 75 kDa, or about 30 kDa to about 60 kDa.

[0344] In some other embodiments, the membrane polymer coating one or more active regions can be crosslinked with the crosslinking agents disclosed herein and in Section 4 above. In some embodiments where two mass transport restricting membranes are present, such as a first mass transport restricting membrane and a second mass transport restricting membrane, each membrane can be crosslinked with different crosslinking agents. For example, but not limited to, the crosslinking agent can, for example, create a membrane that restricts the diffusion of certain compounds (e.g., analytes in the membrane) more or less by influencing the pore size in the membrane. For example, but not limited to, in a sensor configured to detect ketones and glucose, a mass transport restricting membrane coating ketone-responsive regions can have a pore size that restricts the diffusion of compounds larger than ketones (e.g., glucose) through the membrane.

[0345] In some embodiments, the crosslinking agent used in this disclosure may include polyepoxides, carbodiimides, cyanuric chloride, triglycidylglycerol, N-hydroxysuccinimide, imine esters, epichlorohydrin, or derivatives thereof. In some embodiments, the membrane polymer coating one or more active regions may be crosslinked with a branched crosslinking agent, for example, one that can reduce the amount of extractables available from the mass transport-restricted membrane. Non-limiting examples of branched crosslinking agents include branched glycidyl ether crosslinking agents, such as those comprising two or three or more crosslinkable groups. In some embodiments, the branched crosslinking agent may comprise two or more crosslinkable groups, such as polyethylene glycol diglycidyl ether. In some embodiments, the branched crosslinking agent may comprise three or more crosslinkable groups, such as polyethylene glycol tetraglycidyl ether. In some embodiments, the mass transport restriction film may comprise a copolymer of polyvinylpyridine or vinylpyridine and styrene, crosslinked with a branched glycidyl ether (e.g., polyethylene glycol tetraglycidyl ether or polyethylene glycol diglycidyl ether) crosslinking agent comprising two or three crosslinkable groups. In some embodiments, the epoxide groups of the polyepoxide, such as polyethylene glycol tetraglycidyl ether or polyethylene glycol diglycidyl ether, may form covalent bonds with pyridine or imidazole via ring-opening of the epoxide to bridge the crosslinking agent bulk and the hydroxyalkyl groups of the heterocyclic membrane polymer.

[0346] In some embodiments, the crosslinking agent is polyethylene glycol diglycidyl ether (PEGDGE). In some embodiments, the PEGDGE used to promote crosslinking (e.g., intermolecular crosslinking) between two or more membrane polymer backbones can exhibit a wide range of suitable molecular weights. In some embodiments, the molecular weight range of PEGDGE can be from about 100 g / mol to about 5,000 g / mol. The number of ethylene glycol repeating units in each arm of the PEGDGE can be the same or different, and can generally vary within a range in a given sample to produce an average molecular weight. In some embodiments, the PEGDGE used in this disclosure has an average molecular weight (M) of about 200 to 1,000, for example, about 400. n In some embodiments, the crosslinking agent is PEGDGE 400.

[0347] In some embodiments, polyethylene glycol tetraglycidyl ethers used to promote crosslinking (e.g., intermolecular crosslinking) between two or more membrane polymer backbones can exhibit a wide range of suitable molecular weights. Up to four polymer backbones can be crosslinked using a single molecule of the polyethylene glycol tetraglycidyl ether crosslinking agent. In some embodiments, the molecular weight range of the polyethylene glycol tetraglycidyl ether can be from about 1,000 g / mol to about 5,000 g / mol. The number of ethylene glycol repeating units in each arm of the polyethylene glycol tetraglycidyl ether can be the same or different, and can generally vary within a range in a given sample to produce an average molecular weight.

[0348] In some embodiments, polydimethylsiloxane (PDMS) can be incorporated into any mass transport restriction film disclosed herein.

[0349] In some embodiments, the analyte sensor described herein can include a sensor tail comprising at least a first working electrode, a first active region disposed on the surface of the first working electrode, and a first analyte-permeable mass transport restriction membrane covering at least the first active region. In some embodiments, the first active region comprises an enzyme system responsive to a first analyte, such as a ketone, comprising at least one enzyme (optionally covalently bonded to a first polymer and / or stabilizer) and responsive to the first analyte. For example, but not limited to, the analyte sensor described herein can include a sensor tail comprising at least a first working platinum electrode, a ketone-responsive active region comprising an enzyme system on the surface of the first working electrode, the enzyme system comprising β-hydroxybutyrate dehydrogenase and NADH oxidase (one or both of which are optionally covalently bonded to a polymer and / or stabilizer), and a ketone-permeable mass transport restriction membrane covering the ketone-responsive active region. In some embodiments, the mass transport restriction membrane comprises a membrane polymer crosslinked with a branched glycidyl ether crosslinker comprising two or more crosslinkable groups (e.g., polyethylene glycol diglycidyl ether or polyethylene glycol tetraglycidyl ether).

[0350] In some embodiments, the analyte sensor of this disclosure includes a sensor tail including at least a first working electrode and a second working electrode spaced apart from each other along the length of the sensor tail. In some embodiments, a first active region is disposed on the surface of the first working electrode and a second active region is disposed on the surface of the second working electrode, wherein the first active region and the second active region respond to different analytes. For example, but not limited to, the first active region is a ketone-responsive active region. In some embodiments, the second active region is responsive to glucose. In some embodiments, a mass transport limiting membrane covers the first and second active regions, wherein the mass transport limiting membrane comprises a bilayer membrane portion covering the first active region and a homogeneous membrane portion covering the second active region. In some embodiments, each layer of the bilayer membrane portion comprises a different membrane polymer. In some embodiments, the lower layer of the bilayer portion on the first active region comprises a membrane polymer different from that of the homogeneous membrane portion on the second active region, such as a polyvinylpyridine polymer.

[0351] In some embodiments, when the first and second active regions configured for testing different analytes are arranged on separate working electrodes, the mass transport limiting membrane can have different permeability values ​​for the first and second analytes. For example, but not limited to, the mass transport limiting membrane covering at least one active region can comprise a mixture of a first membrane polymer and a second membrane polymer, or a bilayer of the first and second membrane polymers. A homogeneous membrane can cover active regions not covered by the mixture or bilayer, wherein the homogeneous membrane comprises only one of the first or second membrane polymers. Advantageously, the analyte sensor construction disclosed herein conveniently enables continuous membranes having a homogeneous membrane portion to be placed on the first active region of the analyte sensor and a multi-component membrane portion to be placed on the second active region, thereby simultaneously leveling the permeability values ​​for each analyte, thus providing improved sensitivity and detection accuracy. In certain embodiments, continuous membrane deposition can occur through successive impregnation coating operations.

[0352] 6. Interference Area

[0353] In some embodiments, the sensor of this disclosure, such as the sensor tail, may further include an interfering region. In some embodiments, the interfering region may include a polymer region that restricts the flow of one or more interfering substances, for example, to the working electrode surface. In some embodiments, the interfering region may act as a molecular filter that allows the analyte and other substances to be measured at the working electrode to pass through while preventing other substances, such as interfering substances, from passing through. In some embodiments, the interfering substance may affect the signal obtained at the working electrode. Non-limiting examples of interfering substances include acetaminophen, ascorbate / ester, ascorbic acid, bilirubin, cholesterol, creatinine, dopamine, ephedrine, ibuprofen, L-DOPA, methyldopa, salicylates / esters, tetracycline, tolazoline, tolbutamide, triglycerides, urea, and uric acid.

[0354] In some embodiments, the interfering region is located between the working electrode and one or more active regions, such as ketone-responsive active regions. In some embodiments, non-limiting examples of polymers that can be used in the interfering region include polyurethanes, polymers with side-attached ionic groups, and polymers with controlled pore sizes. In some embodiments, the interfering region is formed from one or more fibrous derivatives. Non-limiting examples of fibrous derivatives include polymers such as cellulose acetate, cellulose acetate butyrate, 2-hydroxyethyl cellulose, cellulose acetate phthalate, cellulose acetate propionate, cellulose trimellitate, etc.

[0355] In some embodiments, the interfering region comprises a thin hydrophobic film that is non-expandable and restricts the diffusion of high molecular weight substances. For example, but not limited to, the interfering region can be permeable to relatively low molecular weight substances such as hydrogen peroxide, while restricting the passage of higher molecular weight substances such as ketones, glucose, acetaminophen, and / or ascorbic acid.

[0356] In some embodiments, the interfering region can be deposited directly onto the working electrode, such as the platinum surface of the working electrode. In some embodiments, the interfering region has a thickness ranging from, for example, a dry thickness of: about 0.1 µm to about 1,000 µm, for example, about 1 µm to about 500 µm, about 10 µm to about 100 µm, or about 10 µm to about 100 µm. In some embodiments, the interfering region can have a thickness of: about 0.1 µm to about 10 µm, for example, about 0.5 µm to about 10 µm, about 1 µm to about 10 µm, about 1 µm to about 5 µm, or about 0.1 µm to about 5 µm. In some embodiments, the sensor can be immersed in the interfering region solution more than once. For example, but not limited to, the sensor (or working electrode) of this disclosure can be immersed in the interfering region solution at least two, at least three, at least four, or at least five times to obtain the desired interfering region thickness.

[0357] 7. Preparation

[0358] This disclosure also provides a method for fabricating an analyte sensor comprising one or more active sites. In some embodiments, the method includes screen printing one or more working electrodes. In some embodiments, one of the working electrodes is a platinum electrode. In some embodiments, a conductive material of one or more working electrodes, such as a platinum-containing conductive material, is screen printed onto a substrate.

[0359] In some embodiments, the method may further include adding the enzyme-containing composition to the surface of a working electrode to generate active sites on the working electrode. For example, but not limited to, the composition may include β-hydroxybutyrate dehydrogenase and NADH oxidase, for example, in the amounts and / or ratios disclosed herein. In some embodiments, the composition may further include a cofactor of the enzyme present in the composition, such as NAD, for example, in the amounts and / or ratios disclosed herein. In some embodiments, the composition may further include a crosslinking agent (e.g., polyethylene glycol diglycidyl ether) and a stabilizer (e.g., BSA), for example, in the amounts and / or ratios disclosed herein. In some embodiments, the method may further include immobilizing the enzyme composition.

[0360] In some embodiments, the method may further include adding a membrane composition onto the enzyme composition, such as a cured enzyme composition. In some embodiments, the membrane composition may include a polymer such as polyvinylpyridine, and / or a crosslinking agent such as polyethylene glycol diglycidyl ether. In some embodiments, the membrane is applied to the enzyme composition of the working electrode by impregnation coating (or similar techniques), spray coating, coating, inkjet printing, roll coating, etc. In some embodiments, the method may include curing the membrane polymer composition.

[0361] In some embodiments, the analyte sensor may further include a second working electrode, and the method for fabricating the sensor includes depositing a second enzyme composition, for example, on the surface of the second working electrode for detecting a second analyte. In some embodiments, the method may further include curing or drying the second enzyme composition and depositing a second membrane composition on top of the second enzyme composition.

[0362] In some embodiments, a first impregnation coating operation deposits a first membrane polymer onto a first active region (e.g., a ketone-responsive active region), and a second impregnation coating operation deposits a second membrane polymer onto both the first and second active regions (e.g., a second analyte-responsive active region), thereby defining a bilayer membrane portion on the first active region and a homogeneous membrane portion on the second active region. In some embodiments, the first and second membrane polymers are different from each other. In some embodiments, the lower layer of the bilayer membrane portion and the homogeneous membrane portion contain the same membrane polymer. In some embodiments, the upper layer of the bilayer membrane portion and the homogeneous membrane portion contain the same membrane polymer. In some embodiments, the lower layer of the bilayer membrane portion and the homogeneous membrane portion contain different membrane polymers.

[0363] In some embodiments, a first impregnation coating operation deposits a first membrane polymer onto both the first and second active regions, and a second impregnation coating operation deposits a second membrane polymer onto the first active region, thereby defining a bilayer membrane portion on the first active region. In some embodiments, the first and second membrane polymers are different from each other.

[0364] Generally, membrane thickness is controlled by the concentration of the membrane solution, the number of membrane solution droplets applied, the number of times the sensor is immersed in the membrane solution or sprayed with the membrane solution, the volume of membrane solution sprayed onto the sensor, and any combination of these factors. In some embodiments, the membranes described herein can have thicknesses ranging from about 0.1 micrometers (µm) to about 1,000 µm, for example, from about 1 µm to about 500 µm, from about 10 µm to about 100 µm, or from about 10 µm to about 100 µm. In some embodiments, the sensor can be immersed in the membrane solution more than once. For example, but not limited to, the sensor (or working electrode) of this disclosure can be immersed in the membrane solution at least two, at least three, at least four, or at least five times to obtain the desired membrane thickness.

[0365] In some embodiments, the membrane can cover one or more active regions, and in some embodiments, the active regions can have a thickness of about 0.1 µm to about 10 µm, for example, about 0.5 µm to about 10 µm, about 1 µm to about 10 µm, about 1 µm to about 5 µm, or about 0.1 µm to about 5 µm. In some embodiments, a series of microdroplets can be applied on top of each other to achieve the desired active region and / or membrane thickness without substantially increasing the diameter of the applied microdroplets (i.e., maintaining the desired diameter or range). In some embodiments, each individual microdroplet can be applied and then allowed to cool or dry, followed by the application of one or more additional microdroplets. For example, but not limited to, adding at least one microdroplet, at least two microdroplets, at least three microdroplets, at least four microdroplets, or at least five microdroplets on top of each other to achieve the desired active region thickness.

[0366] III. Usage Method

[0367] This disclosure also provides methods for using the analyte sensors disclosed herein. In some embodiments, this disclosure provides methods for detecting analytes. For example, but not limited to, this disclosure provides methods for detecting one or more analytes including ketones, glucose, alcohols, lactic acid, and / or creatinine, or combinations thereof. In some embodiments, this disclosure provides methods for detecting one or more ketones. In some embodiments, this disclosure provides methods for detecting one or more ketones and a second analyte. In some embodiments, the second analyte can be selected from glucose, alcohols, lactic acid, and creatinine. In some embodiments, the second analyte comprises glucose.

[0368] In some embodiments, this disclosure provides methods for detecting ketone levels in subjects who require it. In some embodiments, this disclosure provides methods for detecting ketone levels in the body of a subject. In some embodiments, this disclosure provides methods for detecting ketone levels in the interstitial fluid of a subject. In some embodiments, this disclosure provides methods for detecting ketone levels in diabetic subjects. In some embodiments, this disclosure provides methods for detecting ketone levels in subjects undergoing a ketogenic diet. In some embodiments, this disclosure provides methods for detecting ketone levels in subjects in a ketogenic state or for detecting ketone levels in subjects to maintain a ketogenic state. In some embodiments, the analyte sensor of this disclosure can be used to ensure that a subject adheres to a ketogenic diet. For example, but not limited to, the analyte sensor of this disclosure can be used to measure ketone levels in a sample to inform the subject to adjust or modify their diet to maintain ketosis. In some embodiments, this disclosure provides methods for detecting ketone levels in subjects at risk of developing ketoacidosis. In some embodiments, this disclosure provides methods for detecting ketone levels in subjects at risk of developing diabetic ketoacidosis. In some embodiments, the sensor of this disclosure can be used to monitor and / or prevent diabetic ketoacidosis. For example, but not limited to, the sensors of this disclosure include sensing chemistry for detecting ketones and glucose, for monitoring and / or preventing diabetic ketoacidosis in subjects (e.g., diabetic subjects). Alternatively or additionally, the sensors of this disclosure can be used in combination with glucose sensors to monitor and / or prevent diabetic ketoacidosis. In some embodiments, the sensors of this disclosure can be used with applications for monitoring ketone levels in subjects, such as for monitoring adherence to a ketogenic diet, for maintaining ketosis and / or monitoring and / or preventing diabetic ketoacidosis.

[0369] In some embodiments, a method for detecting ketones includes: (i) providing an analyte sensor comprising: (a) a sensor tail including at least a first working electrode; (b) a ketone-responsive active region disposed on the surface of the first working electrode and responsive (e.g., at a low potential) to ketones, wherein the ketone-responsive active region includes an enzyme system comprising β-hydroxybutyrate dehydrogenase and NADH oxidase responsive to ketones, and optionally including a first polymer; and (c) a ketone-permeable mass transport restriction membrane covering the ketone-responsive active region; (ii) applying a potential, such as a low potential, to the first working electrode; (iii) obtaining a first signal at or above a redox potential of the ketone-responsive active region, the first signal being proportional to the concentration of the ketone in a fluid contacting the ketone-responsive active region; and (iv) correlating the first signal with the concentration of the ketone in the fluid. In some embodiments, the potential applied to the first working electrode is a potential at which NADH is not oxidized. In some embodiments, the potential applied to the first working electrode is a potential at which NADH is not reversibly oxidized. In some embodiments, the potential applied to the first working electrode is about +0.2 V to about +0.5 V relative to the Ag / AgCl reference. In some embodiments, the potential applied to the first working electrode is about +0.3 V to about +0.4 V relative to the Ag / AgCl reference, for example, about +0.35 V relative to the Ag / AgCl reference.

[0370] In some embodiments, the method of this disclosure may include: (i) exposing an analyte sensor to a fluid containing a ketone; wherein the analyte sensor includes: (a) a sensor tail comprising at least a first working electrode; (b) a ketone-responsive active region disposed on the surface of the first working electrode and responsive (e.g., at a low potential) to a ketone, wherein the ketone-responsive active region comprises an enzyme system comprising β-hydroxybutyrate dehydrogenase and NADH oxidase responsive to a ketone, and optionally comprises a first polymer; and (c) a ketone-permeable mass transport restriction membrane covering the ketone-responsive active region; (ii) applying a potential, such as a low potential, to the first working electrode; (iii) obtaining a first signal at or above a redox potential of the ketone-responsive active region, the first signal being proportional to the concentration of the ketone in the fluid; and (iv) correlating the first signal with the concentration of the ketone in the fluid. In some embodiments, the potential applied to the first working electrode is a potential at which NADH is not oxidized. In some embodiments, the potential applied to the first working electrode is a potential at which NADH is not reversibly oxidized. In some embodiments, the potential applied to the first working electrode is about +0.2 V to about +0.5 V relative to the Ag / AgCl reference. In some embodiments, the potential applied to the first working electrode is about +0.3 V to about +0.4 V relative to the Ag / AgCl reference, for example, about +0.35 V relative to the Ag / AgCl reference.

[0371] In some embodiments, the method of this disclosure may further include detecting a second analyte by providing an analyte sensor including a second active region and / or exposing the analyte sensor including the second active region to a fluid containing a ketone and a second analyte, such as glucose. In some embodiments, the analyte sensor used in the method for detecting a ketone and a second analyte may further include a second working electrode; and a second active region disposed on the surface of the second working electrode and responding differently to a second analyte than the first analyte, wherein the second active region comprises a second polymer, at least one enzyme covalently bonded to the second polymer in response to the second analyte, and optionally a redox mediator covalently bonded to the second polymer; wherein a portion of a mass transport limiting membrane, such as a second portion, covers the second active region. Alternatively, the second active site may be covered by a separate and / or different second mass transport limiting membrane from the mass transport limiting membrane covering the ketone-responsive active region. In some embodiments, the at least one enzyme responding to the second analyte comprises an enzyme system comprising multiple enzymes that commonly respond to the second analyte. In some embodiments, the second analyte comprises glucose.

[0372] In some embodiments, the membrane polymer comprises polyvinylpyridine or polyvinylimidazole. In some embodiments, the membrane polymer comprises a copolymer of vinylpyridine and styrene. In some embodiments, the mass transport restriction membrane of the analyte sensor comprises a membrane polymer crosslinked with a branched crosslinking agent comprising two or more, or three or more, crosslinkable groups. In some embodiments, the branched crosslinking agent comprises polyethylene glycol diglycidyl ether. In some embodiments, the branched crosslinking agent comprises polyethylene glycol tetraglycidyl ether.

[0373] IV. Exemplary Implementation

[0374] A. In some non-limiting embodiments, the subject matter of this disclosure provides an analyte sensor comprising:

[0375] (i) A sensor tail including at least a first working electrode;

[0376] (ii) a ketone-responsive active region disposed on the surface of a first working electrode, wherein the ketone-responsive active region comprises an enzyme system comprising β-hydroxybutyrate dehydrogenase and NADH oxidase; and

[0377] (iii) A ketone-permeable mass transport restriction membrane, which covers at least a portion of the ketone-responsive active region.

[0378] A1. A analyte sensor, wherein the ketone-responsive active region does not include an electron transfer reagent.

[0379] A2. An analyte sensor of A or A1, wherein the ketone-responsive active region does not include superoxide dismutase.

[0380] A3. An analyte sensor of any one of A-A2, wherein the working electrode comprises platinum.

[0381] A4. An analyte sensor of any one of A-A2, wherein the ketone-responsive active region further comprises a stabilizer.

[0382] The analyte sensor for A5 and A4, wherein the stabilizer is serum albumin.

[0383] A6. An analyte sensor of any one of A-A5, wherein the ketone-responsive active region further comprises a crosslinking agent.

[0384] The analyte sensors of A7 and A6, wherein the crosslinking agent is polyethylene glycol diglycidyl ether.

[0385] A8. An analyte sensor of any one of A-A7, wherein the mass transport restriction membrane comprises polyvinylpyridine, polyvinylimidazole, polyvinylpyridine copolymer, polyacrylate, polyurethane, polyether polyurethane, or a combination thereof.

[0386] A9. An analyte sensor of any one of A-A7, wherein the mass transport restriction membrane comprises a copolymer or combination of polyvinylpyridine, polyvinylimidazole, vinylpyridine and styrene.

[0387] Analyte sensors of type A10, A8, or A9, wherein the mass transport restriction membrane contains polyvinylpyridine.

[0388] A11. An analyte sensor of any one of A-A10, wherein the tail of the sensor is configured for insertion into tissue.

[0389] A12. An analyte sensor of any one of A-A11, wherein the ratio of β-hydroxybutyrate dehydrogenase to NADH oxidase present in the ketone-responsive active region is about 5:1 to about 1:5.

[0390] A13. An analyte sensor of any one of A-A12, wherein the ratio of β-hydroxybutyrate dehydrogenase to NADH oxidase present in the ketone-responsive active region is about 2:1 to about 1:2.

[0391] A14. An analyte sensor of any one of A-A13, wherein the amounts of β-hydroxybutyrate dehydrogenase and NADH oxidase present in the ketone-responsive active region are approximately 10% to approximately 80% by weight of the ketone-responsive active region.

[0392] A15. An analyte sensor of any one of A-A14, wherein the ketone-responsive active region responds to the ketone at a potential of about +0.2 V to about +0.5 V relative to the Ag / AgCl reference.

[0393] A16. An analyte sensor of any one of A-A15, wherein the ketone-responsive active region responds to the ketone at a potential of about +0.3 V to about +0.4 V relative to the Ag / AgCl reference.

[0394] A17. An analyte sensor of any one of A-A16, wherein the analyte sensor further comprises: (iv) a second working electrode; and (v) a second active region disposed on the surface of the second working electrode and responsive to a second analyte different from that of a ketone, wherein the second active region comprises at least one enzyme responsive to the second analyte.

[0395] The analyte sensor of A18 and A17, wherein a second portion of the mass transport restriction membrane covers a second active region.

[0396] The analyte sensor of A19 and A17, wherein a second mass transport restriction membrane covers a second active region.

[0397] The analyte sensor of A20 and A17, wherein a second mass transport restriction membrane covers a second active region and a first active region.

[0398] A21. An analyte sensor of any one of A17-A20, wherein the second analyte comprises glucose, lactic acid, creatine anhydride or alcohol.

[0399] A22. Analyte sensor of A21, wherein the second analyte contains glucose.

[0400] A23. An analyte sensor of any one of A-A22, wherein the analyte sensor is configured to detect ketones in the interstitial fluid of a subject.

[0401] A24. An analyte sensor of any one of A-A23, wherein the analyte sensor is implanted in a subject with diabetes.

[0402] A25. An analyte sensor of any one of A-A24, wherein the analyte sensor is implanted in a subject who has or is at risk of developing ketoacidosis.

[0403] A26. An analyte sensor of any one of A-A24, wherein the analyte sensor is implanted in a subject on a ketogenic diet.

[0404] A27. An analyte sensor of any one of A-A24, wherein the analyte sensor is implanted in a subject in or requiring maintenance of ketosis.

[0405] A28. An analyte sensor of any one of A-A27, wherein hydrogen peroxide generated by the reaction of an enzyme system with a ketone in a ketone-responsive active region is detected at the working electrode.

[0406] An analyte sensor of any one of A29-A28, wherein the ketone-responsive active region further comprises a polymer.

[0407] A30. An analyte sensor of any one of A-A29, wherein the polymer comprises polyurethane.

[0408] B. In some non-limiting embodiments, the subject matter of this disclosure provides a method for detecting ketones, wherein the method includes:

[0409] (i) providing an analyte sensor comprising: (a) a sensor tail including at least a first working electrode; (b) a ketone-responsive active region disposed on the surface of the first working electrode, wherein the ketone-responsive active region comprises an enzyme system comprising β-hydroxybutyrate dehydrogenase and NADH oxidase; and (c) a ketone-permeable mass transport restriction membrane covering at least a portion of the ketone-responsive active region.

[0410] (ii) Apply a potential to the first working electrode;

[0411] (iii) A first signal is obtained at or above the redox potential of the ketone-responsive active region, the first signal being proportional to the concentration of the ketone in the fluid contacting the ketone-responsive active region; and

[0412] (iv) Correlate the first signal with the concentration of ketone in the fluid.

[0413] Method B1. B, wherein the ketone-responsive active region does not include an electron transfer reagent.

[0414] Methods B2, B, or B1, wherein the ketone-responsive active region does not include superoxide dismutase.

[0415] B3. Any of the methods in B-B2, wherein the working electrode comprises platinum.

[0416] B4. The method of any one of B-B3, wherein the ketone-responsive active region further comprises a stabilizer.

[0417] Method B5. B4, in which the stabilizer is serum albumin.

[0418] B6. The method of any one of B-B5, wherein the ketone-responsive active region further comprises a crosslinking agent.

[0419] Methods B7 and B6, wherein the crosslinking agent is polyethylene glycol diglycidyl ether.

[0420] B8. The method of any one of B-B7, wherein the mass transport restriction film comprises a copolymer or combination of polyvinylpyridine, polyvinylimidazolium, vinylpyridine and styrene.

[0421] Methods B9 and B8, wherein the mass transport restriction film comprises polyvinylpyridine.

[0422] Methods B10 and B8, wherein the mass transport restriction film comprises polyurethane.

[0423] The method of any one of B11-B10, wherein the ketone-responsive active region further comprises a polymer.

[0424] Methods B12 and B11, wherein the polymer comprises polyurethane.

[0425] B13. The method of any one of B-B12, wherein the tail of the sensor is configured for insertion into tissue.

[0426] B14. The method of any one of B-B13, wherein the ratio of β-hydroxybutyrate dehydrogenase to NADH oxidase present in the ketone-responsive active region is about 5:1 to about 1:5.

[0427] B15. The method of any one of B-B14, wherein the ratio of β-hydroxybutyrate dehydrogenase to NADH oxidase present in the ketone-responsive active region is about 2:1 to about 1:2.

[0428] B16. The method of any one of B-B15, wherein the amounts of β-hydroxybutyrate dehydrogenase and NADH oxidase present in the ketone-responsive active region are about 10% to about 80% by weight of the ketone-responsive active region.

[0429] The method of any one of B17. B-B16, wherein the ketone-responsive active region responds to the ketone at a potential of about +0.2 V to about +0.5 V relative to the Ag / AgCl reference.

[0430] The method of any one of B18. B-B17, wherein the ketone-responsive active region responds to the ketone at a potential of about +0.3 V to about +0.4 V relative to the Ag / AgCl reference.

[0431] B19. The method of any one of B-B18, wherein the analyte sensor further comprises: (d) a second working electrode; and (e) a second active region disposed on the surface of the second working electrode and responding differently to a second analyte than the ketone.

[0432] The method of B20. B19, wherein a second portion of the mass transport restriction membrane covers a second active region.

[0433] The method of B21. B19, wherein a second mass transport restriction membrane covers a second active region.

[0434] B22. Any of the methods in B19-B21, wherein the second analyte comprises glucose, lactic acid, creatine anhydride, or alcohol.

[0435] Method B23. B22, in which the second analyte is glucose.

[0436] B24. Any of the methods in B-B23, wherein the fluid is interstitial fluid from the subject.

[0437] B25. The method of any one of B-B24, wherein the analyte sensor is implanted in a subject with diabetes.

[0438] B26. The method of any one of B-B25, wherein the analyte sensor is implanted in a subject who has or is at risk of developing ketoacidosis.

[0439] B27. The method of any one of B-B26, wherein the analyte sensor is implanted in a subject on a ketogenic diet.

[0440] B28. The method of any one of B-B27, wherein the analyte sensor is implanted in a subject in or requiring maintenance of ketosis.

[0441] B29. The method of any one of B-B28, wherein hydrogen peroxide generated by the reaction of an enzyme system with a ketone in a ketone-responsive active region is detected at the working electrode.

[0442] C. Any of the analyte sensors in A-A30 are used to detect ketones in subjects who require them.

[0443] C1. C is used in the analysis of a sensor in a subject with diabetes.

[0444] C2. C is used in analyte sensors where subjects experience or are at risk of developing ketoacidosis.

[0445] C3. C is used as an analyte sensor in subjects on a ketogenic diet.

[0446] C4. C is used in analyte sensors where subjects are in or need to maintain ketosis.

[0447] Example

[0448] The subject matter of this disclosure will be better understood by referring to the following embodiments, which are provided as examples of the subject matter of this disclosure and not as limitations.

[0449] Example 1: Electrode Potential Selection

[0450] This application provides a method for selecting electrode potentials for analyte sensors having ketone-responsive active regions, as disclosed herein.

[0451] The oxidizing properties of hydrogen peroxide and NADH were determined using a platinum (Pt) electrode in phosphate-buffered saline (PBS). The solution was maintained at 33°C. Linear sweep voltammetry was performed using a CH Instrument CHI1030B potentiostat, and the results were recorded relative to an Ag / AgCl reference electrode. The results are shown below. Figure 23 .like Figure 23 As shown, the oxidation potential of NADH is approximately +0.6 V relative to the Ag / AgCl reference. Additionally, Figure 23 The potential displayed is +0.35 V relative to the Ag / AgCl reference, where hydrogen peroxide oxidizes at a plateau while NADH oxidation is very low. This potential was chosen as the operating potential for the ketone sensor described herein and used in Example 2.

[0452] Example 2: Ketone Sensor

[0453] This application provides a sensor for detecting β-hydroxybutyric acid (which is used as an in vivo substitute for ketones) in embodiments. For this embodiment, using... Figure 22 An enzyme system was used to facilitate the detection of ketones. In particular, an enzyme system including NADH oxidase (NADHOx) and hydroxybutyrate dehydrogenase (HBDH) was used to detect β-hydroxybutyrate. The chemical composition of the sensor is shown in Table 1. Each component was in 10 mM 2-(N-morpholino)ethanesulfonic acid (MES) buffer at pH 5.5.

[0454] Table 1

[0455]

[0456] A Pt electrode was used as the sensor electrode. The formulations in Table 1 were deposited onto the Pt electrode. A control sensor was also prepared using the same sensing chemical formulations in Table 1, but without NADHOx. The sensor was allowed to cure overnight. After curing, the sensor was immersed in a mixture of polyvinylpyridine (PVP) and polyethylene glycol diglycidyl ether 400 (PEGDGE400). The sensor was then allowed to cure again overnight. Beaker tests were subsequently performed at 33°C in 100 mM PBS buffer. The sensor current was recorded using a CH Instrument CHI1030B potentiostat at +0.35 V relative to the Ag / AgCl reference electrode.

[0457] Figure 24 The current responses of four NADHOx sensors and a control are shown. As shown, the current increases over several minutes after exposure to a new β-hydroxybutyric acid concentration followed by stabilization. It is also shown that this effect was not observed for the control sensor, which provides an indication that hydrogen peroxide formation occurs via the suggested sensing mechanism. Figure 25 Exemplary graphs are provided for the current response versus β-hydroxybutyrate concentration for each NADHOx sensor and control.

[0458]

[0459] Although the subject matter and advantages of this disclosure have been described in detail, it should be understood that various changes, substitutions, and modifications can be made to this document without departing from the spirit and scope of this disclosure. Furthermore, the scope of this application is not intended to be limited to the specific embodiments of the processes, mechanisms, preparations, and compositions of matter, methods, and procedures described in the specification. Those skilled in the art will readily understand from the subject matter of this disclosure that existing or subsequently developed processes, mechanisms, preparations, compositions of matter, methods, or steps can perform substantially the same function or achieve substantially the same results using corresponding embodiments described herein. Accordingly, the appended claims are intended to include such processes, mechanisms, preparations, compositions of matter, methods, or steps within their scope.

[0460] All patents, patent applications, publications, product descriptions, schemes, and serial accessions cited throughout this application are incorporated herein by reference in their entirety for the purpose of all purposes.

Claims

1. An analyte sensor for in vivo detection of β-hydroxybutyric acid, comprising: (i) A sensor tail including at least a first working electrode, the first working electrode comprising a conductive material that oxidizes hydrogen peroxide; (ii) A β-hydroxybutyrate-responsive active region disposed on the surface of the first working electrode, wherein the β-hydroxybutyrate-responsive active region comprises an enzyme system comprising β-hydroxybutyrate dehydrogenase and oxidized nicotinamide adenine dinucleotide (NAD). + ), reduced nicotinamide adenine dinucleotide (NADH) and NADH oxidase; and (iii) A β-hydroxybutyric acid-permeable mass transport-limiting membrane, which covers at least a portion of the β-hydroxybutyric acid-responsive active region. The β-hydroxybutyric acid responsive active region is β-hydroxybutyric acid responsive at a potential of approximately +0.2 V to approximately +0.5 V relative to the Ag / AgCl reference. β-hydroxybutyrate dehydrogenase converts β-hydroxybutyrate and NAD+ + It is converted into acetoacetic acid and NADH. NADH oxidase catalyzes the reaction of molecular oxygen and NADH to produce hydrogen peroxide and NAD. + Furthermore, hydrogen peroxide is oxidized at the working electrode to generate a first signal proportional to the concentration of β-hydroxybutyric acid, and The sensor's tail is configured for insertion into tissue to detect β-hydroxybutyrate levels in vivo.

2. The analyte sensor of claim 1, wherein the β-hydroxybutyric acid responsive active region does not include an electron transfer reagent.

3. The analyte sensor of claim 1, wherein the β-hydroxybutyrate responsive active region does not include superoxide dismutase.

4. The analyte sensor of claim 1, wherein the β-hydroxybutyric acid responsive active region further comprises a stabilizer.

5. The analyte sensor of claim 1, wherein the mass transport restriction membrane comprises polyvinylpyridine, polyvinylimidazole, polyvinylpyridine copolymer, polyacrylate, polyurethane, polyether polyurethane, or a combination thereof.

6. The analyte sensor of claim 5, wherein the mass transport limiting membrane comprises polyvinylpyridine.

7. The analyte sensor according to any one of claims 1-6, further comprising: (iv) Second working electrode; and (v) A second active region disposed on the surface of a second working electrode and responding to a second analyte different from β-hydroxybutyric acid, wherein the second active region contains at least one enzyme that responds to the second analyte.

8. The analyte sensor of claim 7, further comprising a second mass transport restriction membrane, the second mass transport restriction membrane covering the second active region.

9. The analyte sensor of claim 7, wherein the second analyte is glucose.

10. A method for detecting β-hydroxybutyric acid, the method comprising: (i) Exposing the analyte sensor of any one of claims 1-6 to a fluid containing β-hydroxybutyric acid; (ii) Apply a potential to the first working electrode; (iii) Obtain a first signal at or above the redox potential of the β-hydroxybutyric acid responsive active region; and (iv) Correlate the first signal with the concentration of β-hydroxybutyric acid in the fluid.

11. The method of claim 10, wherein the β-hydroxybutyric acid responsive active region does not include an electron transfer reagent.

12. The method of claim 10, wherein the first working electrode comprises platinum.

13. The method of claim 10, wherein the β-hydroxybutyric acid responsive active region further comprises a stabilizer.

14. The method of claim 10, wherein the mass transport restriction film comprises polyvinylpyridine, polyvinylimidazole, polyvinylpyridine copolymer, polyacrylate, polyurethane, polyether polyurethane, or a combination thereof.

15. The method of claim 14, wherein the mass transport restriction film comprises polyvinylpyridine.

16. The method of claim 10, wherein the potential applied to the first working electrode is about +0.2 V to about +0.5 V relative to the Ag / AgCl reference.

17. The method of claim 10, wherein the analyte sensor further comprises: (iv) Second working electrode; and (v) A second active region disposed on the surface of the second working electrode and responding differently to a second analyte than β-hydroxybutyric acid; The second mass transport restriction membrane covers the second active region.

18. The analyte sensor of claim 8, wherein the second membrane further covers the β-hydroxybutyric acid responsive active region.

19. The analyte sensor of any one of claims 1-6, wherein the conductive material comprises platinum.

20. The method of claim 10, wherein the β-hydroxybutyrate responsive active region does not include superoxide dismutase.

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