Systems, devices, and methods related to ketone sensors

Abstract

Systems, devices, and methods related to ketone sensors are provided. [Solution] A system for an in vivo ketone sensor is provided having a distal portion configured to be placed in contact with a user's interstitial fluid and a proximal portion. The sensor includes a working electrode, a sensing layer having β-hydroxybutyrate dehydrogenase, and a membrane layer configured to restrict transport of one or more biomolecules. The in vivo ketone sensor is configured to generate a signal at the working electrode corresponding to the amount of ketones in the interstitial fluid. The system includes a sensor control unit having at least one contact in electrical communication with the proximal portion of the sensor, the sensor control unit configured to receive the generated signal and convert it into ketone concentration data using a sensitivity associated with the in vivo ketone sensor. A transmitter configured to communicate the ketone concentration data to a remote device is also included.

Description

[Technical Field]

[0001] The subject matter described herein generally relates to systems, devices, and methods for determining or utilizing calibration information specific to individual medical devices, such as physiological sensors, and / or the manufacture of physiological sensors. [Background technology]

[0002] There is a vast and growing market for monitoring the health and condition of humans and other living animals. Information describing the physical or physiological state of humans can be used in countless ways to aid and improve quality of life and to diagnose and treat undesirable human conditions.

[0003] A common device used to gather such information is a physiological sensor, such as a biochemical sensor, or a device capable of sensing the chemical attributes of a biological entity. Biochemical sensors come in many forms and can be used to sense attributes of fluids, tissues, or gases that form part of or are produced by a biological entity, such as a human. These biochemical sensors can be used on or in the body itself, or on biological material that has already been removed from the body.

[0004] The performance of a biochemical sensor can be characterized in several ways, and a particularly important property may be the accuracy of the biochemical sensor, or the degree to which the biochemical sensor accurately measures the concentration or content of the chemical being measured. The precision of the biochemical sensor, or the degree to which the measurements are accurate or precise, may also be important.

[0005] Although biochemical sensors often have complex and well-researched designs, they can still be subject to some degree of performance variation. This can be caused by multiple factors, including variations in the manufacturing process and variations in the materials of construction used to fabricate the sensor. These variations can cause sensors of the same design and manufacturing process to have measurable differences in their performance. For these and other reasons, there is a need to improve the performance of manufactured biochemical sensors.

[0006] Furthermore, if cells do not receive enough glucose for energy production, the body begins to burn fat to produce ketone bodies (ketones), an alternative energy source. The production of ketones as an energy source can be physiological, as in fasting or a low-carbohydrate diet, or harmful, as in diabetic ketoacidosis. In individuals on a low-carbohydrate (ketogenic) diet, which significantly reduces carbohydrate intake and replaces it with fat, the body uses ketones instead of glucose for energy. A significant reduction in carbohydrates can put the body into a metabolic state called ketosis. Ketogenic diets are used for a variety of reasons in medicine, including the management of pediatric epilepsy and weight loss. In patients with type 2 diabetes, nutritional ketosis is associated with sustained improvements in atherogenic lipid and lipoprotein profiles.

[0007] Similarly, when the body's insulin is insufficient, the resulting lack of intracellular glucose causes the body to produce ketones for fuel. However, if ketones accumulate in the blood faster than they can be metabolized, the body becomes acidic. While ketoacidosis can occur in people with type 2 diabetes, it remains a significant risk for people with type 1 diabetes. For example, among people with diabetes managed with an insulin pump, approximately 3% of people between the ages of 13 and 49 experienced diabetic ketoacidosis more than once in the past three months.

[0008] Currently, ketone levels are most frequently measured using urine or blood ketone test strips. However, urine or blood ketone levels using strip-based technology are limited because they only provide transient information confirming an already ongoing ketosis or DKA event. Early identification of ketone production could potentially warn of impending ketoacidosis, reducing and potentially preventing DKA complications. Real-time, continuous ketone monitoring can also assist clinicians in managing ketoacidosis. For individuals on a low-carbohydrate diet, sensors can serve as a tool to monitor the effectiveness of the diet and indicate the effect of diet or exercise on ketone levels. For these and other reasons, there is a need for improved ketone level measurement. Summary of the Invention

[0009] Provided herein are several exemplary embodiments that can be used to improve the performance of medical devices, such as biochemical sensors, as well as devices and systems that utilize these sensors. These exemplary embodiments relate to improved techniques for evaluating and predicting the performance of biochemical sensors when used by patients, healthcare professionals (HCPs), or other users. Many of these exemplary embodiments relate to determining calibration information based on parameters measured, recorded, or otherwise obtained during the manufacturing process. These parameters may be individualized or specific to individual sensors, and the calibration information determined therefrom may likewise be individualized or specific to the individual sensors.

[0010] In many exemplary embodiments, calibration information is also determined by reference to actual testing of a sensor's sensing capabilities or characteristics. Data obtained from these tests, along with one or more parameters obtained during the manufacturing process, can be used to determine, estimate, extrapolate, or otherwise predict the performance of a sensor distributed to a user. Tests used to evaluate sensing characteristics, such as in vitro tests, are often destructive, contaminating, or otherwise render the tested sensor unsuitable for distribution to a user. In some embodiments, tests are performed on one or more sensors, and the results obtained therefrom are used, along with the manufacturing parameters of a different, untested sensor, to predict the performance of that untested sensor. In this manner, the performance of a particular sensor can be predicted without subjecting the sensor to in vitro testing.

[0011] Information representing the expected performance of a sensor can be embodied as calibration information, which can be made available to any device that uses the sensing signal or data generated by a biochemical sensor to determine the end result of a measurement, such as the concentration or content of a substance being sensed. While applicable on smaller scales, the embodiments described herein are particularly useful when applied to mass production processes. For example, the embodiments described herein can be applied to a group or batch of sensors that are manufactured together. For example, in certain embodiments, a subset of one or more sensors from that group or batch is subjected to in vitro testing, and the resulting test data, along with one or more manufacturing parameters obtained from a different subset of sensors from the same group or batch, is used to predict the performance of that different subset of sensors when distributed to users. Other exemplary embodiments incorporating one or more aspects described herein, as well as other exemplary embodiments different from those described herein, are also described.

[0012] Also provided herein are several exemplary embodiments of systems, devices, and methods for modifying the surface of a sensor substrate to assist in the placement and / or sizing of sensor elements. In some of these embodiments, regions of the surface of the sensor substrate can be modified with electromagnetic radiation to create modified regions. The modified regions can have surface properties that change such that the mobility of a liquid applied to the substrate surface is increased or decreased by the modified regions. The application of the liquid to the surface of the sensor substrate can be performed so that the liquid remains in a target region on the surface, the target region being determined at least in part by the location of the modified region. The electromagnetic radiation can take various forms, such as laser radiation. In these and other embodiments, the surface modification can be the creation of a well in which a sensing element can be placed. The well can be created in various ways, such as by the application of a mechanical force. Exemplary embodiments of sensors fabricated with modified regions and / or wells are within the scope of the present disclosure, as are devices, systems, and kits incorporating them.

[0013] To achieve these and other advantages, and in accordance with the objectives of the disclosed subject matter as embodied and broadly described, the disclosed subject matter is directed to a system having an in vivo ketone sensor having a distal portion configured to be placed in contact with a user's interstitial fluid and a proximal portion. The sensor can include a working electrode, a sensing layer having β-hydroxybutyrate dehydrogenase, and a membrane layer configured to restrict transport of one or more biomolecules. The in vivo ketone sensor can be further configured to generate a signal at the working electrode corresponding to the amount of ketones in the interstitial fluid. The sensor can further include a sensor control unit having at least one contact in electrical communication with the proximal portion of the sensor and a transmitter configured to communicate with a remote device. As embodied herein, the sensor control unit can be configured to receive the generated signal and convert the generated signal into ketone concentration data using a sensitivity associated with the in vivo ketone sensor. As embodied herein, the transmitter can be configured to communicate the ketone concentration data to a remote device.

[0014] As embodied herein, the membrane layer may be configured to prevent penetration of one or more interferents into the area surrounding the working electrode. As embodied herein, the remote device can include a display unit configured to display a graph of in vivo ketone concentrations over a period of time.

[0015] As embodied herein, an in vivo ketone sensor may be operably coupled to a sensor control unit after the sensor is placed in contact with interstitial fluid as embodied herein, and an in vivo ketone sensor may be operably coupled to a sensor control unit prior to placement of the sensor in contact with interstitial fluid.

[0016] As embodied herein, an in vivo ketone sensor may be operably coupled to a sensor control unit prior to placing the sensor in interstitial fluid. In some embodiments, the sensor control unit may further include an adhesive patch having an opening through which the sensor is placed.

[0017] As embodied herein, β-hydroxybutyrate dehydrogenase may be configured to catalyze the reaction of β-hydroxybutyrate to form acetoacetate.

[0018] As embodied herein, the in vivo ketone sensor can further include a reference electrode comprising silver / silver chloride. As embodied herein, the sensor control unit may be reusable.

[0019] Other systems, devices, methods, features, and advantages of the subject matter described herein will be, or will become, apparent to one with skill in the art upon examination of the following figures and detailed description. All such additional systems, methods, features, and advantages are intended to be included within this description, be within the scope of the subject matter described herein, and be protected by the accompanying claims. Features of the exemplary embodiments should in no way be construed as limiting the scope of the appended claims without express recitation of those features in the claims. [Brief explanation of the drawings]

[0020] Details of the subject matter described herein, both as to its structure and operation, will become apparent by examining the accompanying drawings, in which like reference numerals refer to like parts. The components in the figures are not necessarily to scale, emphasis instead being placed upon illustrating the principles of the subject matter. Moreover, all figures are intended to convey concepts, and relative sizes, shapes, and other detailed attributes may be shown diagrammatically rather than literally or precisely. [Figure 1]FIG. 1 is a block diagram illustrating an exemplary embodiment of an in-vivo analyte monitoring system. [Figure 2] FIG. 2 is a block diagram illustrating an exemplary embodiment of a data processing unit. [Figure 3] FIG. 3 is a block diagram illustrating an exemplary embodiment of a display device. [Figure 4] FIG. 4 is a schematic diagram illustrating an exemplary embodiment of an analyte sensor. [Figure 5A] FIG. 5A is a perspective view illustrating an exemplary embodiment of a skin-penetrating analyte sensor. [Figure 5B] FIG. 5B is a cross-sectional view of a portion of the analyte sensor of FIG. 5A. [Figure 6] 6-9 are cross-sectional views illustrating exemplary embodiments of analyte sensors. [Figure 7] 6-9 are cross-sectional views illustrating exemplary embodiments of analyte sensors. [Figure 8] 6-9 are cross-sectional views illustrating exemplary embodiments of analyte sensors. [Figure 9] 6-9 are cross-sectional views illustrating exemplary embodiments of analyte sensors. [Figure 10A] FIG. 10A is a cross-sectional view illustrating an exemplary embodiment of an analyte sensor. [Figure 10B] 10B-10C are cross-sectional views of an exemplary embodiment of an analyte sensor taken along line AA of FIG. 10A. [Figure 10C] 10B-10C are cross-sectional views of an exemplary embodiment of an analyte sensor taken along line AA of FIG. 10A. [Figure 11] FIG. 11 is a conceptual diagram illustrating an exemplary embodiment of an analyte monitoring system. [Figure 12] FIG. 12 is a block diagram illustrating an exemplary embodiment of an on-body electronic device. [Figure 13] FIG. 13 is a block diagram illustrating an exemplary embodiment of a display device. [Figure 14]FIG. 14 is a flow diagram illustrating an exemplary embodiment of information exchange within an analyte monitoring system. [Figure 15] FIG. 15 is a graph illustrating an example of the in vitro sensitivity of an analyte sensor. [Figure 16] FIG. 16 illustrates the signal output of a D-3-hydroxybutyrate dehydrogenase sensor over a 2.3 hour period at various concentrations of D-3-hydroxybutyrate, according to certain embodiments. [Figure 17] FIG. 17 shows the linearity of the sensor signal of a D-3-hydroxybutyrate dehydrogenase sensor as a function of D-3-hydroxybutyrate concentration. [Figure 18] FIG. 18 illustrates the signal output of a D-3-hydroxybutyrate dehydrogenase sensor using free NAD over a 3.6 hour period at various concentrations of D-3-hydroxybutyrate, according to certain embodiments. [Figure 19] FIG. 19 shows the linearity of the sensor signal of a D-3-hydroxybutyrate dehydrogenase sensor as a function of D-3-hydroxybutyrate concentration (ketone). [Figure 20] FIG. 20 shows the stability of the sensor signal of the D-3-hydroxybutyrate dehydrogenase sensor. [Figure 21] FIG. 21 shows the stability of the sensor signal of free and immobilized NAD sensors. [Figure 22] FIG. 22 is an exemplary plot of the change in sensor response with successive additions of aliquots of a ketone. [Figure 23] FIG. 23 is an exemplary plot of the calibrated sensor response as a function of ketone concentration. [Figure 24] FIG. 24 is an exemplary plot of the change in sensor response. [Figure 25] FIG. 25 is an exemplary plot of the response of three ketone sensors worn simultaneously by a single subject to varying body ketone concentrations. [Figure 26A]26A-26G are exemplary plots of ketone levels in interstitial fluid measured by an exemplary sensor against capillary ketone strip baseline measurements. [Figure 26B] 26A-26G are exemplary plots of ketone levels in interstitial fluid measured by an exemplary sensor against capillary ketone strip baseline measurements. [Figure 26C] 26A-26G are exemplary plots of ketone levels in interstitial fluid measured by an exemplary sensor against capillary ketone strip baseline measurements. [Figure 26D] 26A-26G are exemplary plots of ketone levels in interstitial fluid measured by an exemplary sensor against capillary ketone strip baseline measurements. [Figure 26E] 26A-26G are exemplary plots of ketone levels in interstitial fluid measured by an exemplary sensor against capillary ketone strip baseline measurements. [Figure 26F] 26A-26G are exemplary plots of ketone levels in interstitial fluid measured by an exemplary sensor against capillary ketone strip baseline measurements. [Figure 26G] 26A-26G are exemplary plots of ketone levels in interstitial fluid measured by an exemplary sensor against capillary ketone strip baseline measurements. DETAILED DESCRIPTION OF THE INVENTION

[0021] The present subject matter will be described in detail with reference to exemplary embodiments. These exemplary embodiments are set forth for illustrative purposes to aid those skilled in the art in understanding and appreciating the full scope of the present subject matter. These exemplary embodiments do not constitute an exhaustive description of all ways in which the present subject matter can be practiced, as an exhaustive description would be burdensome and unnecessary in light of the exemplary embodiments explicitly described. Thus, the inventive subject matter extends in scope beyond the specific embodiments explicitly described herein.

[0022] The subject matter described herein generally relates to advances in techniques for calibrating medical devices capable of sensing one or more biochemical attributes, as well as systems and devices for implementing these calibration techniques. In many embodiments, the techniques enable the determination of personalized calibration information that varies between and is specific to individual medical devices, as opposed to a single calibration value determined for an entire group of medical devices. There are many classes of medical devices that sense biochemical attributes, and therefore many applications in which the present subject matter can be utilized. While some of these classes of medical devices are described herein, these are merely examples and do not constitute an exhaustive description of all classes of medical devices in which the present subject matter finds utility.

[0023] Medical devices capable of sensing or monitoring chemical levels in bodily fluids can often be classified as part of either in vivo or in vitro systems. In vivo systems often include one or more medical devices that sense one or more biochemical attributes of bodily fluids within the human body by partially or totally implanting the medical device (e.g., sensor) within the human body. A common example is an in vivo analyte sensor useful for monitoring analyte levels within the human body. These analyte sensors can be designed to detect glucose or other analytes that are particularly relevant to monitoring diabetic conditions.

[0024] An in vitro system includes one or more medical devices that sense one or more biochemical attributes of a bodily fluid, such as blood, plasma, or urine, or other substance, such as a homogenized biopsy sample, drawn from the human body. In vitro systems can also be referred to as ex vivo systems. A common example is an in vitro analyte sensor, such as a test strip. In vitro test strips may be designed to detect and measure glucose or other analytes, particularly relevant to monitoring diabetic conditions.

[0025] Systems and devices that incorporate or utilize data from either in vivo or in vitro medical devices are broadly referred to herein as biochemical monitoring systems and biochemical monitoring devices, respectively. Systems and devices that incorporate or utilize data from medical devices designed to sense the level of an analyte (e.g., glucose) are referred to herein as analyte monitoring systems and analyte monitoring devices, respectively.

[0026] Exemplary embodiments of these calibration techniques will be presented by reference to their application to in vivo and in vitro medical devices. Most of the embodiments will be described with reference to in vivo medical devices, and in particular to in vivo analyte sensors. This is merely to facilitate presentation of the features and aspects of these exemplary embodiments and is not intended to limit these calibration techniques to use solely with in vivo analyte sensors. Indeed, as noted above, the present subject matter is broadly applicable to other types of medical devices, some embodiments of which will also be explicitly described.

[0027] Certain exemplary embodiments of these calibration techniques allow for the determination of personalized calibration information specific to each individual sensor, which can then be used to calibrate the output of the individual sensor, if desired. In many embodiments, the personalized calibration information is unique to each individual medical device within a common manufacturing group or lot and can vary between each individual medical device in the common group. These embodiments are in contrast to approaches in which a single calibration value is determined for an entire group or lot of medical devices, such that all medical devices within a common manufacturing group have the same calibration value.

[0028] In some exemplary embodiments, a sensing characteristic of a first subset of medical devices (e.g., a sample or baseline subset) is determined. In the case of an analyte sensor, this sensing characteristic can be, for example, the sensitivity of the sensor to the analyte. The sensing characteristic can be determined using in vitro (or in vivo use) testing of the first subset of medical devices. Examples of such testing are described in more detail herein. One or more individualized manufacturing parameters can be measured from each medical device of a different second subset of medical devices (e.g., a distribution subset intended for distribution by the manufacturer to third-party users). In some exemplary embodiments, the baseline subset and the distribution subset are taken from the same production lot. Measurement of the individualized manufacturing parameters can be performed, for example, by the manufacturer during or after the manufacturing process. The individualized manufacturing parameters can be directly or indirectly correlated to the sensing characteristic of the medical device, and numerous examples of such individualized manufacturing parameters are described herein.

[0029] Individualized calibration information can then be determined independently for each medical device in the distribution subset of medical devices using at least the individualized manufacturing parameters of each device in the distribution subset and the sensed characteristics of the baseline subset. This can result in calibration information that is unique to each medical device in the distribution subset and that can vary between medical devices due to variations in the individualized manufacturing parameters. In some embodiments, two or more individualized manufacturing parameters are used to determine the calibration information. In some embodiments, one or more qualitative manufacturing parameters are used alone or in conjunction with quantitative individualized manufacturing parameters.

[0030] As described in further detail herein, studies have confirmed that embodiments of the present subject matter provide clear improvements in the accuracy of biochemical sensing measurements made by medical devices. This represents an improvement in the operation of the calibrated medical devices themselves, which in turn leads to an improvement in the operation of monitoring systems and / or monitoring devices incorporating these medical devices, as well as an improvement in the operation of computing devices that process or otherwise utilize the improved accuracy data generated by the calibrated medical devices. Improvements have also been observed through reduced variability between medical devices, and improvements have also been observed in the manufacturing yield of medical devices.

[0031] Before describing embodiments relating to individualized calibration techniques in detail, it is desirable to first describe exemplary embodiments of in vivo and in vitro analyte monitoring systems, and examples of their operation, all of which may be used in conjunction with these calibration technique embodiments.

[0032] Exemplary Embodiments of an In-Vivo Analyte Monitoring System There are various types of analyte monitoring systems for use with in vivo sensors. For example, a "continuous analyte monitoring" system (e.g., a "continuous glucose monitoring" system) is an in vivo system that can automatically transmit data from a sensor controlling device to a reader device repeatedly or continuously without prompting, e.g., according to a schedule. As another example, a "flash analyte monitoring" system (e.g., a "flash glucose monitoring" system or simply a "flash" system) is an in vivo system that can transfer data from a sensor controlling device in response to a scan or data request by a reader device, such as using near-field communication (NFC) or radio frequency identification (RFID) protocols.

[0033] In-vivo analyte sensors may be partially or wholly implanted within the human body to contact and sense analyte levels within bodily fluids within a user. An in-vivo sensor may be part of a sensor control device that resides on the user's body and includes electronics and a power source that enable and control analyte sensing. Sensor control devices and variations thereof may also be referred to as "sensor control units," "on-body electronics" devices or units, "on-body" devices or units, "sensor data communication" devices or units, or transmitter devices or units, to name a few. The term "on body" refers to any device that resides directly on or in close proximity to the body, such as a wearable device (e.g., eyeglasses, armband, wristband or bracelet, neckband, necklace, etc.).

[0034] The in-vivo monitoring system may also include one or more reader devices that receive sensed analyte data from the sensor control device. These reader devices may process, retransmit, and / or display the sensed analyte data in any number of forms. These devices and variations thereof may be referred to as "handheld reader devices," "reader devices" (or simply "readers"), "display devices," "handheld electronic devices" (or handhelds), "portable data processing" devices or units, "data receivers," "receiver" devices or units (or simply receivers), "relay" devices or units, "remote" devices or units, "companion" devices or units, "human interface" devices or units, to name a few. Computing devices such as personal computers may be used as reader devices.

[0035] In-vivo analyte monitoring systems can also be used in conjunction with in-vitro medical devices. For example, the reader device may incorporate or be coupled to a port for receiving an in-vitro test strip carrying a user's bodily fluid, which can be analyzed to determine the user's analyte level.

[0036] In vivo sensors In vivo sensors can be formed on a substrate, e.g., a substantially planar substrate or a non-planar circular or cylindrical substrate. In many embodiments, the sensor comprises at least one conductive structure, e.g., an electrode. Sensor embodiments can be single-electrode embodiments (e.g., having one or fewer electrodes) or multi-electrode embodiments (e.g., having exactly two, exactly three, or more electrodes). Sensor embodiments often include a working electrode and can also include at least one counter electrode (or counter / reference electrode) and / or at least one reference electrode (or reference / counter electrode). The electrodes can be arranged as separate regions electrically isolated by insulating regions and can be electrically connected to a circuit for receiving (and optionally conditioning and / or processing) the electrical signal generated by the electrode. The electrodes can have planar (e.g., relatively flat) or non-planar (e.g., relatively curved or rounded, such as hemispherical, cylindrical, or irregular surfaces, and combinations thereof) surfaces. The electrodes can be arranged in layers, concentric circles, or otherwise.

[0037] Accordingly, embodiments include analyte monitoring devices and systems including analyte sensors at least partially positionable below a user's skin surface for in vivo detection of analytes, including glucose, lactate, etc., in bodily fluids. Embodiments include fully implantable analyte sensors and analyte sensors in which only a portion of the sensor is positioned below the skin and a portion of the sensor resides above the skin, for example, for contact with a sensor control device (which may include a transmitter), receiver / display unit, transceiver, processor, etc. The sensor may be positionable through a user's external skin surface for, for example, continuous or periodic monitoring (periodic according to regular intervals, irregular intervals, a schedule, frequent repetition, etc.) of the level of an analyte in the user's bodily fluid (e.g., interstitial fluid, subcutaneous fluid, dermal fluid, blood, or other bodily fluid of interest). For purposes of this description, continuous monitoring and periodic monitoring are used interchangeably unless otherwise noted. The sensor response may be correlated and / or converted to the analyte level in the blood or other fluid. In certain embodiments, an analyte sensor may be placed in contact with interstitial fluid to detect the level of glucose, which may be used to infer the glucose level in the user's bloodstream. The analyte sensor may be insertable into a vein, artery, or other part of the body that contains bodily fluid. Embodiments of the analyte sensor may be configured to monitor the level of an analyte over a period that may range from seconds, minutes, hours, days, weeks, months, or longer.

[0038] In certain embodiments, an analyte sensor, such as a glucose sensor, is capable of in vivo detection of an analyte for one hour or more, e.g., several hours or more, e.g., several days or more, e.g., three days or more, e.g., five days or more, e.g., seven days or more, e.g., several weeks or more, or one month or more. Future analyte levels may be predicted based on obtained information, e.g., the current analyte level at time t0, the rate of change of the analyte, etc. A predictive alarm may notify a user of a predicted analyte level of concern before the user's analyte level reaches the future predicted analyte level, providing the user with an opportunity to take corrective action.

[0039] In electrochemical embodiments, the sensor is placed transcutaneously, for example, at a subcutaneous site, so that the skin fluid at the site contacts the sensor. In other in vivo embodiments, placement of at least a portion of the sensor may be intravascular. The sensor operates to electrolyze a target analyte in the subcutaneous fluid or blood so that a current is generated between the working electrode and the counter electrode. A value of the current associated with the working electrode is determined. If multiple working electrodes are used, the current value from each of the working electrodes may be determined. A microprocessor can be used to collect these periodically determined current values ​​or to further process these values.

[0040] If the analyte concentration is successfully determined, it may be displayed, stored, transmitted, and / or otherwise processed to provide useful information. By way of example, the raw signal or analyte concentration may be used as a basis for determining the rate of change of the analyte concentration, which should not change at a rate greater than a predetermined threshold amount. If the rate of change of the analyte concentration exceeds a predetermined threshold, an indication may be displayed or otherwise transmitted to indicate this fact. In certain embodiments, if the rate of change of the analyte concentration exceeds a predetermined threshold, an alarm is activated to alert the user.

[0041] As demonstrated herein, the present embodiments are useful in connection with devices used to measure or monitor analytes (e.g., glucose), such as any such devices described herein. The embodiments described herein can be used to monitor and / or process information about any number of one or more different analytes. Analytes that can be monitored include, but are not limited to, acetylcholine, amylase, bilirubin, carbon dioxide, cholesterol, chorionic gonadotropin, glycosylated hemoglobin (HbA1c), creatine kinase (e.g., CK-MB), creatine, creatinine, DNA, fructosamine, glucose, glucose derivatives, glutamine, growth hormone, hormones, ketones, ketone bodies, lactate, oxygen, peroxide, prostate-specific antigen, protein, prothrombin, RNA, thyroid-stimulating hormone, troponin, and any combination thereof. For example, concentrations of drugs such as antibiotics (e.g., gentamicin, vancomycin, etc.), digitoxin, digoxin, drugs of abuse, theophylline, and warfarin may be monitored in addition to or instead of an analyte. In embodiments monitoring two or more analytes, the analytes may be monitored simultaneously or at different times. These methods may be used in conjunction with a device used to measure or monitor another analyte (e.g., ketones, ketone bodies, HbA1c, etc.), including, for example, oxygen, carbon dioxide, proteins, drugs, or another moiety of interest, or any combination thereof, found in bodily fluids, including, for example, subcutaneous fluid, dermal fluid, interstitial fluid, or other bodily fluids of interest, or any combination thereof. Generally, the device is in good contact, such as complete and substantially continuous contact, with the bodily fluid.

[0042] According to embodiments, the analyte sensor may be operably coupled to the sensor control device / unit after placing the sensor in contact with the interstitial fluid, hi some embodiments, the analyte sensor may be operably coupled to the sensor control device / unit before placing the sensor in contact with the interstitial fluid.

[0043] According to embodiments of the present disclosure, the measurement sensor is suitable for electrochemically measuring analyte concentrations, such as ketone concentrations, in bodily fluids. In these embodiments, the measurement sensor includes at least a working electrode and a counter electrode. Other embodiments may further include a reference electrode. The working electrode is typically associated with a beta-hydroxybutyrate (BHB)-responsive enzyme. A mediator may also be included. In some embodiments, the mediator is added to the sensor by the manufacturer, e.g., included in the sensor prior to use. The redox mediator may be disposed relative to the working electrode and may directly or indirectly transfer electrons between the compound and the working electrode. The redox mediator may be, for example, immobilized on the working electrode, e.g., captured on a surface, or chemically bound to the surface.

[0044] Embodiments of the present disclosure include in vivo analyte monitoring devices, systems, kits, and processes for analyte monitoring, as well as processes for making the analyte monitoring devices, systems, and kits. Included are on-body (e.g., at least some of the devices, systems, or components thereof are maintained on or in proximity to a user's body to monitor the analyte) physiological monitoring devices configured for real-time measurement / monitoring of a desired analyte level, such as a glucose level, over one or more predetermined periods, such as one or more predetermined monitoring periods. Embodiments include a transcutaneously positioned analyte sensor electrically coupled to electronics provided within a housing designed to be attached to a user's body, e.g., the user's skin surface, for the useful life of the analyte sensor or the predetermined monitoring period. For example, an on-body electronics assembly includes electronics operably coupled to the analyte sensor and provided within a housing for placement on the user's body.

[0045] Such devices and systems having analyte sensors provide continuous or periodic analyte level monitoring that is performed automatically or semi-automatically by programmed or programmable control logic or routines in the monitoring device or system. As used herein, continuous, automatic, and / or periodic monitoring refers to in vivo monitoring or detection of analyte levels by a transcutaneously placed analyte sensor.

[0046] In certain embodiments, in vivo monitored analyte level results are automatically communicated from the electronics unit to another device or component of the system. That is, when results are available, they are automatically transmitted to a display device (or other user interaction device) of the system, for example, according to a fixed or dynamic data communication schedule implemented by the system. In other embodiments, in vivo monitored analyte level results are not automatically communicated, transferred, or output to one or more devices or components of the system. In such embodiments, results are provided only in response to a query to the system. That is, results are communicated to a component or device of the system only in response to a query or request for such results. In certain embodiments, in vivo monitoring results may be recorded or stored in the system's memory and communicated or transferred to another device or component of the system only after one or more predetermined monitoring periods.

[0047] Embodiments include software and / or hardware for transforming any one of the devices, components, or systems into any one of the other devices, components, or systems, and such transformations may be user-configurable after manufacture. A transformation module, including hardware and / or software for accomplishing such transformations, may be coupleable to a given system to transform it.

[0048] Embodiments include electronics coupled to the analyte sensors that provide the functionality to operate the analyte sensors to monitor analyte levels over a predetermined monitoring period, such as, for example, about 30 days (or longer in certain embodiments), about 14 days, about 10 days, about 5 days, about 1 day, less than about 1 day, etc. In certain embodiments, the useful life of each analyte sensor may be the same as or different from the predetermined monitoring period. In certain embodiments, the electronics components that provide the functionality to operate the analyte sensors include control logic or a microprocessor coupled to a power source, such as a battery, to drive the in vivo analyte sensors to perform electrochemical reactions and generate a result signal corresponding to the monitored analyte level.

[0049] The electronics may include other components, such as one or more data storage units or memories (volatile and / or nonvolatile), communication components for communicating information corresponding to in vivo monitored analyte levels to the display device automatically when the information is available or selectively in response to a request for monitored analyte level information. In certain embodiments, data communication between the display device and the electronics coupled to the sensor is performed serially (e.g., data transfer between them is not simultaneous) or in parallel. For example, the display device in certain embodiments is configured to transmit a signal or data packet to the electronics coupled to the sensor, and upon receiving the transmitted signal or data packet, the electronics coupled to the sensor communicates back to the display device. In certain embodiments, the display device may be configured to continuously provide RF power and data / signals and detect or receive one or more return data packets or signals from the electronics coupled to the sensor when it is within a predetermined RF power range from the display device. In certain embodiments, the display device and the electronics coupled to the sensor may be configured to transmit one or more data packets simultaneously.

[0050] Embodiments also include electronics programmed to store or record data associated with monitored analyte levels in one or more data storage units or memories over the sensor's useful life or during a monitoring period. During the monitoring period, information corresponding to the monitored analyte levels may be stored but may not be displayed or output during the sensor's useful life, and the stored data may be later retrieved from memory at the end of the sensor's useful life or after the expiration of a predetermined monitoring period, for example, for clinical analysis, therapy management, etc.

[0051] In certain embodiments, the predetermined monitoring period is the same as the sensor's useful life period, and the predetermined monitoring period ends when the analyte sensor's useful life period expires (and therefore is no longer being used for in vivo analyte level monitoring). In certain embodiments, the predetermined monitoring period can include multiple sensor's useful life periods, and the predetermined monitoring period does not end when the analyte sensor's useful life period expires, but rather the expired analyte sensor is replaced with another analyte sensor during the same predetermined monitoring period. In certain embodiments, the predetermined monitoring period includes replacing multiple analyte sensors for use.

[0052] Analyte level trend information in certain embodiments is generated or constructed based on stored analyte level information over a period of time (e.g., corresponding to a temperature period, etc.) and communicated to a display device. In certain embodiments, the trend information is output graphically and / or audibly and / or tactilely and / or numerically and / or otherwise presented on a user interface of the display device to provide an indication of analyte level fluctuations over this period of time.

[0053] Embodiments include wirelessly communicating analyte level information from the on-body electronics device to a second device, such as a display device. Examples of communication protocols between the on-body electronics and the display device may include radio frequency identification (RFID) protocols or RF communication protocols. Exemplary RFID protocols include, but are not limited to, near-field communication (NFC) protocols, high frequency wireless communication protocols, and long-range communication protocols (e.g., using ultra-high frequency (UHF) communication systems) that include short communication ranges (e.g., about 12 inches (about 304.8 mm) or less, or about 6 inches (about 152.4 mm) or less, or about 3 inches (about 76.2 mm) or less, or about 2 inches (about 50.8 mm) or less) for providing signals or data from the on-body electronics to the display device.

[0054] The communication protocol in certain embodiments uses a 433 MHz frequency, a 13.56 MHz frequency, a 2.45 GHz frequency, or other suitable frequency for wireless communication between on-body electronics, including electronics coupled to an analyte sensor, and other devices, such as one or more display devices and / or personal computers. Although certain data transmission frequencies and / or data communication ranges are described above, data transmission frequencies and / or data communication ranges suitable for other data may be used between various devices of an analyte monitoring system within the scope of the present disclosure.

[0055] Embodiments include data management systems, including, for example, a data network and / or a personal computer and / or a server terminal and / or one or more remote computers, configured to receive collected or stored data from the display device for presenting analyte information and / or for further processing in conjunction with physiological monitoring for health management. For example, the display device may include one or more communication ports (wired or wireless) for connection to a data network or computer terminal for transferring collected or stored analyte-related data to another device and / or location. In certain embodiments, the analyte-related data is communicated directly from electronics coupled to the analyte sensor via a data network to a personal computer, server terminal, and / or remote computer.

[0056] In certain embodiments, even though an in-vivo analyte sensor automatically and / or continuously monitors analyte levels in vivo, e.g., the sensor automatically monitors an analyte such as ketone at predefined time intervals over its useful life, the analyte information is provided or revealed to the user (provided in a user interface device) only when desired by the user. For example, the analyte sensor may be placed in vivo and coupled to the on-body electronics for a given sensing period, e.g., about 14 days, about 21 days, or about 30 days or longer. In certain embodiments, the sensor-derived analyte information is automatically communicated from the sensor electronics assembly to a remote monitoring or display device for output to the user according to a schedule programmed in the on-body electronics (e.g., about every 1 minute, about every 5 minutes, about every 10 minutes, etc.) throughout the 14-day period. In certain embodiments, the sensor-derived analyte information is communicated from the sensor electronics assembly to a remote monitoring or display device only at user-determined times, e.g., whenever the user decides to check the analyte information. At such time, a communication system is activated and the sensor-derived information is then transmitted from the on-body electronics to a remote or display device. For example, using RFID communications, in one embodiment, a user places a display device in proximity to an on-body electronic coupled to an analyte sensor and receives real-time (and / or historical) analyte level information from the on-body electronic (hereinafter referred to as an "on-demand" reading).

[0057] In still other embodiments, information may be automatically and / or continuously communicated from the first device to the second device when analyte information is available, and the second device stores or records the received information without presenting or outputting the information to a user. In such embodiments, information is received by the second device from the first device when the information becomes available (e.g., when a sensor detects an analyte level according to a time schedule). However, the received information is initially stored on the second device and output to a user interface or output component (e.g., a display) of the second device only upon detection of a request for the information on the second device.

[0058] Thus, in certain embodiments, once the sensor electronics assembly is positioned on the body such that at least a portion of the in-vivo sensor is in contact with bodily fluid and the sensor is electrically coupled to the electronics unit, the display device can be powered on (or may be continuously powered) and sensor-derived analyte information can be communicated on-demand from the on-body electronics to the display device by executing a software algorithm stored in and accessed from the memory of the display device to generate one or more request commands, control signals, or data packets for transmission to the on-body electronics. For example, the software algorithm, executing under control of a microprocessor or application-specific integrated circuit (ASIC) of the display device, may include a routine that detects the position of the on-body electronics relative to the display device in order to initiate transmission of the generated request commands, control signals, and / or data packets.

[0059] The display device may include programming stored in memory for execution by one or more microprocessors and / or ASICs to generate and transmit one or more request commands, control signals, or data packets for transmission to the on-body electronics in response to user activation of an input mechanism on the display device, such as pressing a button on the display device or triggering a soft button associated with a data communication function. The input mechanism may alternatively or additionally be provided on or within the on-body electronics that may be configured for user activation. In certain embodiments, a voice command or audible signal may be used to prompt or instruct the microprocessor or ASIC to execute a software routine stored in memory to generate and transmit one or more request commands, control signals, or data packets to the on-body device. In embodiments that are voice-activated or responsive to voice commands or audible signals, the on-body electronics and / or display device include a microphone, a speaker, and processing routines stored in the memory of the on-body electronics and / or display device for processing the voice command and / or audible signal. In certain embodiments, placing the on-body device and the display device within a predetermined distance (e.g., in close proximity) of each other initiates one or more software routines stored in the memory of the display device to generate and transmit request commands, control signals, or data packets.

[0060] Different types and / or forms and / or amounts of information may be transmitted with each on-demand reading, including, but not limited to, one or more of: current analyte level information (e.g., real-time or most recently acquired analyte level information corresponding in time to the time the reading was initiated), rate of change of the analyte over a predetermined period of time, rate of change of the analyte (acceleration of the rate of change), and historical analyte information corresponding to analyte information acquired prior to the given reading and stored in the assembly's memory. Some or all of the real-time, historical, rate of change, rate of change (such as acceleration or deceleration) information may be transmitted to the display device for a given reading. In certain embodiments, the type and / or form and / or amount of information transmitted to the display device may be pre-programmed and / or non-alterable (e.g., preset at the time of manufacture), or may not be pre-programmed and / or non-alterable, and thus may be field selectable and / or alterable one or more times (e.g., by activating a switch on the system, etc.).

[0061] Thus, in certain embodiments, for each on-demand reading, the display device will output the current (real-time) sensor-derived analyte value (e.g., in numeric form), the current rate of analyte change (e.g., in the form of an analyte rate indicator, such as an arrow pointing in the direction indicating the current rate), and historical analyte trend data (e.g., in the form of a graphical trace) based on the sensor readings obtained by and stored in the memory of the on-body electronics. In addition, a skin or sensor temperature reading or measurement associated with each on-demand reading may be communicated from the on-body electronics to the display device. However, the temperature reading or measurement need not be output or displayed on the display device, but rather may be used in conjunction with a software routine executed by the display device to correct or compensate the analyte measurement values ​​output to the user on the display device.

[0062] As described, embodiments include an in-vivo analyte sensor and on-body electronics, which together provide a body-wearable sensor electronics assembly. In certain embodiments, the in-vivo analyte sensor is fully integrated with the on-body electronics (i.e., fixedly connected during manufacturing), while in other embodiments, they are separate but connectable after manufacturing (e.g., before, during, or after sensor insertion into the body). The on-body electronics can include an in-vivo ketone sensor (excluding the sensor portion for placement in vivo), electronics, a battery, and an antenna housed within a waterproof housing that includes or is attachable to adhesive pads. In certain embodiments, the housing can withstand immersion in about 1 meter of water for at least up to 30 minutes. In certain embodiments, the housing can withstand continuous water contact for, e.g., longer than about 30 minutes, and continue to function properly according to its intended use without water damage to the housing's electronics, e.g., if the housing is suitable for submersion.

[0063] Embodiments include a sensor insertion device, which may also be referred to herein as a sensor delivery unit or the like. The insertion device may hold the on-body electronics assembly entirely within an internal compartment; for example, the insertion device may be “pre-loaded” with the on-body electronics assembly during the manufacturing process (e.g., the on-body electronics may be packaged within a sterile internal compartment of the insertion device). In such embodiments, the insertion device can form a sensor assembly package (including sterile packaging) for a pre-use or new on-body electronics assembly and an insertion device configured to apply the on-body electronics assembly to a recipient's body.

[0064] Embodiments include a portable handheld display device, separate from the on-body electronics assembly, as a separate device that collects information from the assembly and provides sensor-derived analyte readings to a user. Such devices can be referred to in many ways as previously described. Certain embodiments may include an integrated in-vitro analyte meter. In certain embodiments, the display device includes one or more wired or wireless communication ports, such as USB, serial, or parallel, configured to establish communication between the display device and another unit (e.g., the on-body electronics, a power supply unit for recharging a battery, a PC, etc.). For example, the display device communication ports can enable charging of the display device battery using a respective charging cable and / or data exchange between the display device and its compatible informatics software.

[0065] Compatible informatics software in certain embodiments includes, but is not limited to, stand-alone or network-enabled data management software programs that reside or execute on, for example, a display device, a personal computer, or a server terminal to perform, for example, data analysis, charting, data storage, data archiving, and data communication and synchronization. Informatics software in certain embodiments can also include software for performing field-upgradable functions to upgrade firmware on the display device and / or on-body electronics unit, to upgrade resident software on the display device and / or on-body electronics unit, e.g., firmware versions that include additional features, and / or that fix software bugs or errors, etc.

[0066] Embodiments include programming embedded on a computer-readable medium, e.g., computer-based application software (which may also be referred to herein as informatics software, programming, etc.), that processes analyte information obtained from the system and / or user self-reported data. The application software may be installed on a host computer, such as a cell phone, PC, Internet-enabled human interface device such as an Internet-enabled phone, personal digital assistant, or the like, by a display device or on-body electronics unit. The informatics programming can transform data obtained and stored on the display device or on-body unit for use by a user.

[0067] As described in detail below, embodiments include devices, systems, kits, and / or methods for monitoring one or more physiological parameters, such as, but not limited to, analyte level, temperature level, heart rate, user activity level, etc., over a predetermined monitoring period. Methods of manufacture are also provided. The predetermined monitoring period may be less than about one hour, or may include about one hour or more, e.g., about several hours or more, e.g., about several days or more, e.g., about three days or more, e.g., about five days or more, e.g., about seven days or more, e.g., about ten days or more, e.g., about fourteen days or more, e.g., about several weeks, e.g., about one month or more. In certain embodiments, after expiration of the predetermined monitoring period, one or more features of the system may be automatically deactivated or disabled in the on-body electronics assembly and / or the display device.

[0068] For example, the predetermined monitoring period can begin with placement of the sensor within the body and contacting bodily fluids, such as interstitial fluid, and / or activation (or powering up to a fully operational mode) of the on-body electronics. Initialization of the on-body electronics may be performed using commands generated and transmitted by the display device in response to activation of a switch and / or by placing the display device within a predetermined distance (e.g., proximity) to the on-body electronics, or by user manual activation of a switch on the on-body electronics unit, e.g., pressing a button; such activation may be caused by an insertion device, for example, as described in U.S. Patent Application Publication No. 2011 / 0213225, the disclosure of which is incorporated by reference in its entirety.

[0069] Once initialized in response to a command received from the display device, the on-body electronics retrieves and executes software routines from its memory to fully power on the on-body electronics components, effectively placing the on-body electronics in a fully operational mode in response to receiving a wake-up command from the display device. For example, prior to receiving a command from the display device, some of the components within the on-body electronics may be powered by their internal power source, such as a battery, while another portion of the components within the on-body electronics may be powered off or at a low power, including an inactive mode with no power, or all of the components may be in an inactive mode, a power-down mode. Upon receiving the command, the remaining (or all) of the on-body electronics components are switched to an active, fully operational mode.

[0070] An embodiment of the on-body electronics may include one or more printed circuit boards having electronics including control logic implemented in an ASIC, microprocessor, memory, etc., and a transcutaneously positionable analyte sensor forming a single assembly. The on-body electronics may be configured to provide one or more signals or data packets related to the monitored analyte level upon detecting a display device of the analyte monitoring system within a predetermined proximity range for a period of time (e.g., about 2 minutes, e.g., 1 minute or less, e.g., about 30 seconds or less, e.g., about 10 seconds or less, e.g., about 5 seconds or less, e.g., about 2 seconds or less) and / or until a confirmation, such as an audible and / or visual and / or tactile (e.g., vibration) notification, is output on the display device indicating successful acquisition of the analyte-related signal from the on-body electronics. In an embodiment, an identifying notification may also be output for unsuccessful acquisition.

[0071] In certain embodiments, the monitored analyte levels may be correlated and / or converted to ketone levels in blood or other bodily fluids. Such conversion may be accomplished by on-body electronics, while in other embodiments, it may be accomplished using display device electronics.

[0072] 1 , an analyte monitoring system 100 includes an analyte sensor 101, a data processing unit 102 connectable to the sensor 101, and a primary receiver unit or display device 104. In some examples, the primary display device 104 is configured to communicate with the data processing unit 102 via a communication link 103. In particular embodiments, the primary display device 104 may be further configured to transmit data to a data processing terminal 105 for evaluating, processing, or formatting data received by the primary display device 104. The data processing terminal 105 may be configured to receive data directly from the data processing unit 102 via a communication link 107, which may optionally be configured for bidirectional communication. Additionally, the data processing unit 102 may include electronics and a transmitter or transceiver for transmitting data to and / or receiving data from the primary display device 104 and / or the data processing terminal 105 and / or optionally a secondary receiver unit or display device 106.

[0073] 1 also shows optional secondary display device 106 operably coupled to communication link 103 and configured to receive data transmitted from data processing unit 102. Secondary display device 106 may be configured to communicate with primary display device 104 and data processing terminal 105. In particular embodiments, secondary display device 106 may be configured for two-way wireless communication with each of primary display device 104 and data processing terminal 105. As described in further detail below, in some examples, secondary display device 106 may be a reduced-capability receiver compared to primary display device 104; for example, secondary display device 106 may include a limited or minimal number of functions and features compared to primary display device 104. Accordingly, secondary display device 106 may include a smaller (in one or more dimensions, including all dimensions) compact housing or may be embodied in a device including, for example, a wristwatch, an armband, a PDA, an mp3 player, a mobile phone, etc. Alternatively, the secondary display device 106 may be configured with the same or substantially similar functionality and features as the primary display device 104. The secondary display device 106 may include, for example, a docking portion configured to mate with a docking cradle unit placed at a bedside for overnight monitoring, and / or a two-way communication device. The docking cradle may be capable of recharging the power source.

[0074] The embodiment of the analyte monitoring system 100 shown in FIG. 1 shows only one analyte sensor 101, data processing unit 102, and data processing terminal 105. However, one skilled in the art will understand that the analyte monitoring system 100 may include more than one sensor 101, more than one data processing unit 102, and / or more than one data processing terminal 105. Multiple sensors may be placed on a user for analyte monitoring at the same time or at different times. In certain embodiments, analyte information obtained by a first sensor placed on a user may be used as a comparison with analyte information obtained by a second sensor. This may be useful to confirm or verify analyte information obtained from one or both of the sensors. Such redundancy may be useful when analyte information is considered in important treatment-related decisions. In certain embodiments, the first sensor may be used to calibrate the second sensor.

[0075] In a multi-component environment, each component may be configured to be uniquely identified by one or more of the other components in the system, so that communication conflicts may be easily resolved between the various components in the analyte monitoring system 100. For example, unique IDs and communication channels, etc. may be used.

[0076] In certain embodiments, the sensor 101 is physically located in or on the body of a user whose analyte level is being monitored. The sensor 101 may be configured to at least periodically sample the user's analyte level and convert the sampled analyte level into a corresponding signal for transmission by the data processing unit 102. The data processing unit 102 may be coupled to the sensor 101 such that both devices are located in or on the user's body, with at least a portion of the analyte sensor 101 being transcutaneously positioned. The data processing unit 102 may include a fixation element, such as an adhesive, for securing it to the user's body. A mount (not shown) attachable to the user and matable with the data processing unit 102 may be used. For example, the mount may include an adhesive surface. The data processing unit 102 performs data processing functions, which may include, but are not limited to, filtering and encoding data signals, each corresponding to the user's sampled analyte level, for transmission to the primary display device 104 via the communication link 103. In some embodiments, the sensor 101 or the data processing unit 102 or the combined sensor / data processing unit may be fully implantable below the surface of the user's skin.

[0077] In particular embodiments, the primary display device 104 may include an analog interface section including an RF receiver and antenna configured to communicate with the data processing unit 102 via the communication link 103, and a data processing section for processing data received from the data processing unit 102, including data decoding, error detection and correction, data clock generation, data bit recovery, etc., or any combination thereof.

[0078] During operation, the primary display device 104 in certain embodiments is configured to synchronize with the data processing unit 102 to uniquely identify the data processing unit 102, for example based on the identification information of the data processing unit 102, and then periodically receive signals transmitted from the data processing unit 102 associated with the monitoring analyte level monitored by the sensor 101.

[0079] Referring again to FIG. 1 , the data processing terminal 105 may include a portable computer, including a personal computer, laptop, or handheld device (e.g., a personal digital assistant (PDA)); a telephone, including a cellular phone (e.g., a multimedia and Internet-enabled cellular phone, including an iPhone®, Blackberry®, Android® phone, or similar phone); an mp3 player (e.g., an iPod®, etc.); a pager; and / or a drug delivery device (e.g., an infusion device), each of which may be configured for data communication with a display device via a wired or wireless connection. Additionally, the data processing terminal 105 may be connected to a data network (not shown) for storing, retrieving, updating, and / or analyzing data corresponding to the user's detected analyte level.

[0080] The data processing terminal 105 may include a drug delivery device (e.g., an infusion device), such as an insulin infusion pump, which may be configured to administer a medication (e.g., insulin) to a user and may be configured to communicate with the primary display device 104, in particular, to receive measured analyte levels. Alternatively, the primary display device 104 may be configured to integrate the infusion device therein, such that the primary display device 104 is configured to administer an appropriate medication (e.g., insulin) to the user, for example, to manage and modify a basal profile, and to determine an appropriate bolus for administration based on detected analyte levels received from the data processing unit 102. The infusion device may be an external device or may be an internal device, such as a device that is fully implantable within the user.

[0081] In certain embodiments, data processing terminal 105, which may include an infusion device, e.g., an insulin pump, may be configured to receive analyte signals from data processing unit 102 and thus incorporate the functionality of primary display device 104, including data processing for managing a user's insulin therapy and analyte monitoring. In certain embodiments, communication link 103, as well as one or more of the other communication interfaces shown in FIG. 1, may use one or more wireless communication protocols, such as, but not limited to, an RF communication protocol, an infrared communication protocol, a Bluetooth®-enabled communication protocol, an 802.11x wireless communication protocol, or an equivalent wireless communication protocol that enables secure wireless communication of several units (e.g., due to Health Insurance Portability and Accountability Act (HIPAA) requirements) while avoiding potential data collisions and interference.

[0082] 2 is a block diagram illustrating one embodiment of the data processing unit 102 of the analyte monitoring system shown in FIG. 1. User input and / or interface components may be included, or the data processing unit may not include user input and / or interface components. In certain embodiments, one or more application-specific integrated circuits (ASICs) (e.g., having processing circuitry and non-transitory memory for storing software instructions for execution by the processing circuitry) may be used to implement one or more functions or routines associated with the operation of the data processing unit (and / or display device), for example, using one or more state machines and buffers.

[0083] As seen in the embodiment of FIG. 2, the analyte sensor 101 (FIG. 1) includes four contacts, three of which are a working electrode (W) 210, a reference electrode (R) 212, and a counter electrode (C) 213, each operably coupled to the analog interface 201 of the data processing unit 102. This embodiment also shows an optional guard contact (G) 211. Fewer or more electrodes may be used. For example, the functions of the counter electrode and the reference electrode may be provided by a single counter / reference electrode. In some cases, there may be two or more working electrodes and / or reference electrodes and / or counter electrodes, etc.

[0084] 3 is a block diagram of one embodiment of a receiver / monitor unit, such as the primary display device 104 of the analyte monitoring system shown in FIG. 1. The primary display device 104 includes one or more of a test strip interface 301, an RF receiver 302, a user input 303, an optional temperature detection section 304, and a clock 305, each of which is operably coupled to a processing and storage section 307 (which may include processing circuitry and non-transitory memory that stores software instructions for execution by the processing circuitry). The primary display device 104 also includes a power supply 306 operably coupled to a power conversion and monitoring section 308. The power conversion and monitoring section 308 is further coupled to the processing and storage section 307. Also shown are a receiver serial communication section 309 and an output 310, each of which is operably coupled to the processing and storage section 307. The primary display device 104 may or may not include user input and / or interface components.

[0085] In certain embodiments, the test strip interface 301 includes an analyte testing portion (e.g., a ketone level testing portion) for receiving a blood (or other bodily fluid sample) analyte test or information related thereto. For example, the test strip interface 301 may include a test strip port for accepting a test strip (e.g., a ketone test strip). The device can determine the analyte level on the test strip and, optionally, display (or otherwise communicate) the analyte level on the output 310 of the primary display device 104. Any suitable test strip may be used, for example, a test strip that requires only a very small amount of applied sample (e.g., 3 microliters or less, e.g., 1 microliter or less, e.g., 0.5 microliters or less, e.g., 0.1 microliters or less) on the strip to obtain accurate glucose information. The ketone information obtained by the in vitro glucose testing device may be used for various purposes, calculations, etc. For example, the information may be used to calibrate the sensor 101 (FIG. 1), to confirm and increase the reliability of the sensor 101 results (e.g., if the information obtained by the sensor 101 is used in treatment-related decisions), etc.

[0086] In further embodiments, the data processing unit 102 and / or primary display device 104 and / or secondary display device 106 and / or data processing terminal / infusion device 105 may be configured to receive analyte values ​​wirelessly, for example, from a blood glucose meter via a communications link. In further embodiments, a user operating or using the analyte monitoring system 100 may manually input analyte values, for example, using a user interface (e.g., a keyboard, keypad, voice commands, etc.) incorporated into one or more of the data processing unit 102, primary display device 104, secondary display device 106, or data processing terminal / infusion device 105.

[0087] 4 schematically illustrates one embodiment of an analyte sensor 400 according to embodiments of the present disclosure. This sensor embodiment includes electrodes 401, 402, 403 on a base 404. The electrodes (and / or other features) may be applied or processed using any suitable technique, such as chemical vapor deposition (CVD), physical vapor deposition, sputtering, reactive sputtering, printing, coating, ablation (e.g., laser ablation), painting, dip coating, etching, etc. Materials include, but are not limited to, any one or more of aluminum, carbon (including graphite), cobalt, copper, gallium, gold, indium, iridium, iron, lead, magnesium, mercury (as an amalgam), nickel, niobium, osmium, palladium, platinum, rhenium, rhodium, selenium, silicon (e.g., doped polysilicon), silver, tantalum, tin, titanium, tungsten, uranium, vanadium, zinc, zirconium, mixtures thereof, and alloys, oxides, or metal compounds of these elements.

[0088] The analyte sensor 400 may be fully implantable within a user, or may be configured so that only a portion is positioned within the user (internal) and another portion is positioned outside the user (external). For example, the sensor 400 may include a first portion positionable above the surface 410 of the skin and a second portion positioned below the surface of the skin. In such embodiments, the external portion may include contacts (connected by traces to respective electrodes of the second portion) for connection to another device also external to the user, such as a sensor control device. While the embodiment of FIG. 4 shows three electrodes side-by-side on the same surface of the base 404, other configurations are contemplated, such as fewer or more electrodes, some or all electrodes on different surfaces of the base or on separate bases, some or all electrodes stacked together, electrodes of different materials and dimensions, etc.

[0089] FIG. 5A shows a perspective view of one embodiment of an analyte sensor 500 having a first portion (which in this embodiment may be characterized as a major portion) positionable above the surface of the skin 510 and a second portion (which in this embodiment may be characterized as a minor portion) positionable below the surface of the skin, e.g., including an insertion tip 530 that penetrates the skin and enters, e.g., the subcutaneous space 520, and contacts a user's biological fluids, such as interstitial fluid. A working electrode contact portion 511, a reference electrode contact portion 512, and a counter electrode contact portion 513 are disposed on the first portion of the sensor 500 located above the skin surface 510. A working electrode 501, a reference electrode 502, and a counter electrode 503 are shown on the second portion of the sensor 500, specifically the insertion tip 530. Traces may be provided from the electrodes at the tip 530 to the contacts, as shown in FIG. 5A. It should be understood that more or fewer electrodes may be provided on the sensor. For example, the sensor may include two or more working electrodes, and / or the counter and reference electrodes may be a single counter / reference electrode, and so on.

[0090] Figure 5B shows a cross-sectional view of a portion of the sensor 500 of Figure 5A. The electrodes 501, 509 / 502, 503, as well as the substrate and dielectric layers of the sensor 500, are provided in a layered configuration or structure. For example, as shown in Figure 5B, in one embodiment, the sensor 500 (such as the analyte sensor 101 of Figure 1) includes a substrate layer 504 and a first conductive layer 501, such as carbon, gold, etc., disposed on at least a portion of the substrate layer 504 and capable of providing a working electrode. Also shown disposed on at least a portion of the first conductive layer 501 is a sensing region 508.

[0091] A first insulating layer 505, such as a first dielectric layer in certain embodiments, may be disposed or laminated over at least a portion of the first conductive layer 501, and a second conductive layer 509 may be disposed or laminated over at least a portion of the first insulating (or dielectric) layer 505. As shown in Figure 5B, the second conductive layer 509, along with a second conductive material 502, such as a layer of silver / silver chloride (Ag / AgCl), may provide a reference electrode.

[0092] A second insulating layer 506, such as a second dielectric layer in certain embodiments, may be disposed or laminated on at least a portion of the second conductive layer 509. Additionally, a third conductive layer 503 may be disposed on at least a portion of the second insulating layer 506 and may provide a counter electrode 503. Finally, a third insulating layer 507 may be disposed or laminated on at least a portion of the third conductive layer 503. In this manner, the sensor 500 may be laminated such that at least a portion of each of the conductive layers is separated by a respective insulating layer (e.g., a dielectric layer). The embodiments of Figures 5A and 5B show layers having different lengths. In certain examples, some or all of the layers may have the same or different lengths and / or widths.

[0093] In certain embodiments, some or all of the electrodes 501, 502, 503 may be provided on the same side of the substrate 504 in a layered configuration as described above, or may be provided coplanar, such that two or more electrodes are disposed on the same plane (e.g., side-by-side (e.g., parallel) or at an angle relative to each other) on the substrate 504. For example, coplanar electrodes may include appropriate spacing between them and / or may include a dielectric or insulating material disposed between the conductive layers / electrodes.

[0094] Furthermore, in certain embodiments, one or more of the electrodes 501, 502, 503 may be disposed on both sides of the substrate 504. In such embodiments, the contact pads may be on the same or different sides of the substrate. For example, the electrodes may be on a first side and their respective contacts may be on a second side, and traces connecting the electrodes and contacts may traverse the substrate, for example.

[0095] Embodiments of double-sided laminated sensor configurations that may be utilized in connection with the present disclosure are described below with reference to FIGS. 6-8. FIG. 6 illustrates a cross-sectional view of a distal portion of a double-sided analyte sensor 600. The analyte sensor 600 includes an at least generally planar insulating base substrate 601, e.g., an at least generally planar dielectric base substrate, having a first conductive layer 602 covering substantially the entire first surface area, e.g., the top surface area, of the insulating base substrate 601, e.g., the conductive layer extending substantially the entire length of the substrate to the distal end and from side edge to side edge across the entire width of the substrate. A second conductive layer 603 covers substantially the entire second surface, e.g., the bottom side, of the insulating base substrate 601. However, one or both of the conductive layers may terminate proximal to the distal end and / or have a width that is less than the width of the insulating substrate 601, terminating at a selected distance from the side edges of the substrate, which distance may be equidistant or may vary from each of the side edges.

[0096] One of the first or second conductive layers, e.g., first conductive layer 602, may be configured to include the working electrode of the sensor. The opposing conductive layer, here second conductive layer 603, may be configured to include a reference electrode and / or a counter electrode. If conductive layer 603 functions as either a reference electrode or a counter electrode, but not both, a third electrode may optionally be provided on a surface region of a proximal portion of the sensor (not shown), on a separate substrate, or as an additional conductive layer disposed either above or below conductive layer 602 or 603 and separated therefrom by insulating layer(s). For example, in some embodiments in which analyte sensor 600 is configured to be partially implanted, conductive layer 603 may be configured to include a reference electrode, and a third electrode (not shown) present only on the non-implanted proximal portion of the sensor may be configured to include the counter electrode of the sensor.

[0097] The first insulating layer 604 covers at least a portion of the conductive layer 602, and the second insulating layer 605 covers at least a portion of the conductive layer 603. In one embodiment, at least one of the first insulating layer 604 and the second insulating layer 605 does not extend to the distal end of the analyte sensor 600, leaving an exposed area of ​​one or more conductive layers.

[0098] 7 shows a cross-sectional view of a distal portion of a double-sided analyte sensor 700, which includes an at least generally planar insulating base substrate 701, e.g., an at least generally planar dielectric base substrate, having a first conductive layer 702 covering substantially the entire first surface area, e.g., top surface area, of the insulating base substrate 701, e.g., the conductive layer extending substantially the entire length of the substrate to the distal end and from side edge to side edge across the entire width of the substrate. A second conductive layer 703 covers substantially the entire second surface, e.g., the bottom side, of the insulating base substrate 701. However, one or both of the conductive layers may terminate proximal to the distal end and / or have a width that is less than the width of the insulating substrate 701, terminating at a selected distance from the side edges of the substrate, which distance may be equidistant or may vary from each of the side edges.

[0099] 7, the conductive layer 702 is configured to include a working electrode, as shown and described in more detail below, including a sensing region 702A disposed on at least a portion of the first conductive layer 702. Note that although a single sensing region 702A is shown, in other embodiments, multiple spatially separated sensing elements may be utilized.

[0100] In the embodiment of FIG. 7, conductive layer 703 is configured to include a reference electrode comprising a secondary layer of conductive material 703A, for example Ag / AgCl, disposed on a distal portion of conductive layer 703.

[0101] A first insulating layer 704 covers a portion of the conductive layer 702, and a second insulating layer 705 covers a portion of the conductive layer 703. The first insulating layer 704 does not extend to the distal end of the analyte sensor 700, leaving an exposed area of ​​the conductive layer where the sensing region 702A is located. The insulating layer 705 on the bottom / reference electrode side of the sensor may extend any suitable length of the distal portion of the sensor, for example, the entire length or a portion of both the primary and secondary conductive layers. For example, as shown in FIG. 7 , the bottom insulating layer 705 extends across the entire bottom surface area of ​​the secondary conductive material 703A but terminates proximal to the distal end of the length of the conductive layer 703. Note that at least the end of the secondary conductive material 703A extending along the side edge of the substrate 701 is not covered by the insulating layer 705 and is therefore exposed to the environment during operational use.

[0102] In an alternative embodiment, as shown in FIG. 8 , an analyte sensor 800 has an insulating layer 804 on the working electrode side of an insulating base substrate 801, which may be provided before the sensing region 802A, whereby the insulating layer 804 has at least two portions spaced apart from one another on the conductive layer 802. The sensing region 802A is then provided in the space between the two portions. For example, if multiple sensing components or layers are desired, three or more spaced apart portions may be provided. The bottom insulating layer 805 has a length that terminates proximate the secondary conductive layer 803A on the bottom primary conductive layer 803. As described above, additional conductive and dielectric layers may be provided on one or both sides of the sensor.

[0103] It should be noted that although Figures 6-8 are shown or described herein as illustrating a working electrode and a reference electrode that can be provided in a particular layered configuration, the relative arrangement of these layers may be varied. For example, a counter electrode layer may be provided on one side of an insulating base substrate, while a working electrode layer and a reference electrode layer are provided in a stacked configuration on the opposite side of the insulating base substrate. In addition, by adjusting the number of conductive and insulating layers, a different number of electrodes than those shown in Figures 6-8 may be provided. For example, a three- or four-electrode sensor may be provided.

[0104] One or more membranes, which may function as one or more of the analyte flow-modulating layer, interferent-removing layer, and / or biocompatible layer, described in more detail below, may be included with, on, or around the sensor, e.g., as one or more of the outermost layers. For example, the membrane layer may be configured to prevent penetration of one or more interferents into the area surrounding the working electrode. Those skilled in the art will readily recognize that membranes can take many forms. The membrane may include only one component, or multiple components. The membrane may have a spherical shape that surrounds the sensor's terminal region (e.g., the sides and distal tip). The membrane may have a generally planar structure and may be characterized as a layer. Planar membranes may be smooth or may have minor surface (topological) variations. The membrane may also be configured as other non-planar structures. For example, the membrane may have a cylindrical or partially cylindrical shape, a hemispherical or other partially spherical shape, an irregular shape, or other rounded or curved shape.

[0105] In certain embodiments, as shown in FIG. 7 , a first membrane layer 706 is provided only on the sensing region 702A of the working electrode 702 to regulate the rate of analyte diffusion or flux to the sensing region. In embodiments in which the membrane layer is provided on a single component / material, it may be preferable to do so using the same striping configuration and method as used for the other materials / components. Here, the membrane material 706 preferably has a width greater than that of the sensing component 702A. Controlling the thickness of the membrane 706 is important because it acts to restrict analyte flux to the active region of the sensor and thus contributes to the sensor's sensitivity. Providing the membrane 706 in the form of stripes / bands facilitates controlling its thickness. A second membrane layer 707 covering the remaining surface area of ​​the sensor tail may also be provided to function as a biocompatible conformal coating and provide smooth edges across the entire sensor. In other sensor embodiments, as shown in FIG. 8 , a single homogeneous membrane 806 may be coated across the entire sensor surface area, or at least across both sides of the distal tail portion. It should be noted that membrane materials may have to be applied following singulation of the sensor precursor to coat the distal and lateral ends of the sensor. In some embodiments, the analyte sensors are dip coated after singulation to apply one or more membranes. Alternatively, the analyte sensors may be slot die coated, with each side of the analyte sensor being coated separately.

[0106] 9 illustrates a cross-sectional view of a distal portion of an exemplary double-sided analyte sensor 900 according to one embodiment of the present disclosure, the double-sided analyte sensor including an at least generally planar insulating base substrate 901, e.g., an at least generally planar dielectric base substrate, having a first conductive layer 902. A second conductive layer 903 is disposed on a first side, e.g., the bottom side, of the insulating base substrate 901. While shown extending to the distal end of the sensor, one or both of the conductive layers may terminate proximal to the distal end and / or have a width that is less than the width of the insulating substrate 901, the width terminating at a selected distance from each of the side edges of the substrate, which distance may be equidistant or may vary. See, for example, the analyte sensor assembly 900, described in more detail below, which is provided with first and second conductive layers that define electrodes, e.g., including electrode traces, having widths that are less than the width of the insulating base substrate.

[0107] 9, the conductive layer 903 is configured to include a working electrode including a sensing region 908 disposed on at least a portion of the conductive layer 903, which sensing region is described in more detail below. It should be noted that multiple spatially separated sensing components or layers may be utilized in forming the working electrode; for example, one or more sensing "dots" or regions may be provided on the conductive layer 903 as shown herein, or a single sensing component may be used (not shown).

[0108] 9, conductive layer 906 is configured to include a reference electrode including a secondary layer of conductive material 906A, e.g., Ag / AgCl, disposed on a distal portion of conductive layer 906. Similar to conductive layers 902 and 903, conductive layer 906 may terminate proximal to the distal end and / or may have a width that is less than the width of insulating substrate 901, with the width terminating at a selected distance from each of the side edges of the substrate, which distance may be equidistant or may vary, as described in more detail below with reference to FIGS.

[0109] In the embodiment shown in FIG. 9 , the conductive layer 902 is configured to include a counter electrode. A first insulating layer 904 covers a portion of the conductive layer 902, and a second insulating layer 905 covers a portion of the conductive layer 903. The first insulating layer 904 does not extend to the distal end of the analyte sensor 900, leaving an exposed area of ​​the conductive layer 902 to act as a counter electrode. The insulating layer 905 covers a portion of the conductive layer 903, leaving an exposed area of ​​the conductive layer 903 where the sensing area 908 is located. As mentioned above, in some embodiments, multiple spaced-apart sensing components or layers may be provided (as shown), while in other embodiments, a single sensing area may be provided. The insulating layer 907 on a first side, e.g., the bottom side of the sensor (in the view provided by FIG. 9 ), may extend any suitable length of the distal portion of the sensor, for example, the entire length or a portion of both the conductive layers 906 and 906A. 9, bottom insulating layer 907 extends across the entire bottom surface area of ​​secondary conductive material 906A and terminates distally at the distal end of the length of conductive layer 906. Note that at least the ends of secondary conductive material 906A that extend along the side edges of substrate 901 are not covered by insulating layer 907 and are therefore exposed to the environment during operational use.

[0110] As shown in FIG. 9 , a homogeneous membrane 909 may be coated over the entire sensor surface area, or at least over both sides of the distal tail. Note that membrane material may have to be applied following singulation of the sensor precursor to coat the distal and side ends of the sensor. In some embodiments, the analyte sensor is dip-coated after singulation to apply one or more membranes (or to apply one membrane at various stages). Alternatively, the analyte sensor may be slot-die coated, with each side of the analyte sensor being coated separately. While the membrane 909 is shown in FIG. 9 as having an angular shape that matches the underlying surface variations, it could also have a more spherical or irregular shape.

[0111] When fabricating a layered sensor, it may be desirable to utilize relatively thin insulating layers to reduce the overall width of the sensor. For example, referring to FIG. 9, insulating layers 904, 905, and 907 may be relatively thin relative to insulating substrate layer 901. For example, insulating layers 904, 905, and 907 may have thicknesses in the range of 20-25 μm, while substrate layer 901 has a thickness in the range of 0.1-0.15 mm. However, during sensor singulation, where such singulation is achieved by cutting two or more conductive layers separated by such thin insulating layers, shorts between two conductive layers may occur.

[0112] One way to address this potential problem is to provide one of the conductive layers, e.g., the electrode layers, at least in part as a relatively narrow electrode, e.g., including a relatively narrow conductive trace, so that during the singulation process, the sensor is cut on either side of the narrow electrode such that one electrode is cut without cutting the narrow electrode.

[0113] For example, referring to FIGS. 10A-10C, a sensor 1000 is shown that includes insulating layers 1003 and 1005. The insulating layers 1003 and 1005 may be thin relative to a generally flat insulating base substrate layer 1001, or vice versa. For example, the insulating layers 1003 and 1005 may have a thickness in the range of 15-30 μm, while the substrate layer 1001 has a thickness in the range of 0.1-0.15 mm. Such sensors may be manufactured in multiple sheets, with a single sheet containing multiple sensors. However, such a process generally requires singulation of the sensors before use. If such singulation requires cutting through two or more conductive layers separated by insulating layers, short circuits between the two conductive layers may occur, especially if the insulating layers are thin. To avoid such short circuits, fewer than all of the conductive layers may be cut during the singulation process. For example, at least one of the conductive layers may be at least partially provided as an electrode, e.g., comprising a conductive trace, having a narrow width relative to one or more other conductive layers, such that during the singulation process, a first conductive layer separated from a second conductive layer only by a thin insulating layer, e.g., an insulating layer having a thickness in the range of 15-30 μm, is cut while the second conductive layer is not cut.

[0114] 10A and 10C, a sensor 1000 includes an at least generally flat insulating base substrate 1001. A first conductive layer 1002 is disposed on the at least generally flat insulating base substrate 1001. A first relatively thin insulating layer 1003, e.g., an insulating layer having a thickness in the range of 15-30 μm, is disposed on the first conductive layer 1002, and a second conductive layer 1004 is disposed on the relatively thin insulating layer 1003. Finally, a second relatively thin insulating layer 1005, e.g., an insulating layer having a thickness in the range of 15-30 μm, is disposed on the second conductive layer 1004.

[0115] As shown in FIG. 10B , the first conductive layer 1002 can be an electrode having a narrow width relative to the conductive layer 1004, as shown in the cross section taken along line AA in FIG. 10B . Alternatively, the second conductive layer 1004 can be a conductive electrode having a narrow width relative to the conductive layer 1002, as shown in the cross section taken along line AA in FIG. 10C . Singulation cut lines 1006 are shown in FIGS. 10B and 10C . The sensor can be singulated, for example, by cutting on both sides of the relatively narrow conductive electrode, for example, in region 1007, as shown in FIGS. 10B and 10C . With reference to FIG. 10B , singulation by cutting along the singulation cut line 1006 results in cutting through the conductive layer 1004 but not through the conductive layer 1002. With reference to FIG. 10C , singulation by cutting along the singulation cut line 1006 results in cutting through the conductive layer 1002 but not through the conductive layer 1004.

[0116] An embodiment of a sensing area can be described as the area shown generally in Figure 5B as 508 and in Figure 9 as 908. As mentioned above, the sensing area may be provided as a single sensing element, such as shown in Figure 5B as 508, in Figure 7 as 702A, and in Figure 8 as 802A, or as multiple sensing elements, such as shown in Figure 9 as 908. Multiple sensing elements or sensing "spots" are described in U.S. Patent Application Publication No. 2012 / 0150005, which is incorporated herein by reference in its entirety.

[0117] The term "sensing area" is a broad term and can be described as the active chemical area of ​​a biosensor. Those skilled in the art will readily recognize that the sensing area can take many forms. The sensing area can include only one component or multiple components (e.g., sensing area 908 of FIG. 9). In the embodiment of FIG. 5B, for example, the sensing area is a generally planar structure and can be characterized as a layer. A planar sensing area may be smooth or may have minor surface (topological) variations. The sensing area may also have a non-planar structure. For example, the sensing area can have a cylindrical or partial cylindrical shape, a hemispherical or other partial spherical shape, an irregular shape, or other rounded or curved shape.

[0118] In certain examples, the analyte-responsive enzyme is distributed throughout the sensing area. For example, the analyte-responsive enzyme may be uniformly distributed throughout the sensing area such that the concentration of the analyte-responsive enzyme is substantially the same throughout the sensing area. In some cases, the sensing area may have a homogeneous distribution of the analyte-responsive enzyme. In certain embodiments, the redox mediator is distributed throughout the sensing area. For example, the redox mediator may be uniformly distributed throughout the sensing area such that the concentration of the redox mediator is substantially the same throughout the sensing area. In some cases, the sensing area may have a homogeneous distribution of the redox mediator. In certain embodiments, both the analyte-responsive enzyme and the redox mediator are uniformly distributed throughout the sensing area, as described above.

[0119] As described above, analyte sensors may include an analyte-responsive enzyme to provide a sensing component or sensing region. Some analytes, such as oxygen, can be directly electrooxidized or electroreduced on the sensor, more specifically, at least on the working electrode of the sensor. Other analytes, such as glucose and lactate, require the presence of at least one electron transfer agent and / or at least one catalyst to facilitate the electrooxidation or electroreduction of the analyte. Catalysts can also be used for analytes, such as oxygen, that can be directly electrooxidized or electroreduced on the working electrode. For these analytes, each working electrode includes a sensing region (e.g., see sensing region 508 in FIG. 5B ) adjacent to or on the surface of the working electrode. In many embodiments, the sensing region is formed only adjacent to or on at least a small portion of the working electrode.

[0120] The sensing region can include one or more components configured to facilitate the electrochemical oxidation or reduction of the analyte. The sensing region can include, for example, a catalyst that catalyzes a reaction of the analyte and generates a response at the working electrode, an electron transfer agent that transfers electrons between the analyte and the working electrode (or other component), or both.

[0121] A variety of different sensing area configurations can be used. The sensing area is often located in contact with or in close proximity to an electrode, such as a working electrode. In certain embodiments, the sensing area is deposited on the conductive material of the working electrode. The sensing area may extend beyond the conductive material of the working electrode. In some cases, the sensing area may extend over other electrodes, for example, over a counter electrode and / or a reference electrode (or if a counter / reference is provided).

[0122] The sensing region in direct contact with the working electrode may contain an electron transfer agent to directly or indirectly transfer electrons between the analyte and the working electrode, and / or a catalyst to facilitate reaction of the analyte. For example, a glucose, lactate, or oxygen electrode may be formed with a sensing region containing a catalyst including glucose oxidase, glucose dehydrogenase, lactate oxidase, or laccase, respectively, and an electron transfer agent to facilitate the electro-oxidation of glucose, lactate, or oxygen, respectively.

[0123] In other embodiments, the sensing region is not deposited directly on the working electrode. Instead, the sensing region 508 (FIG. 5) may be spaced apart from the working electrode, e.g., separated from the working electrode by a separation layer. The separation layer may include one or more membranes or films or a physical distance. In addition to separating the working electrode from the sensing region, the separation layer may also function as a mass transport limiting layer and / or an interferent removal layer and / or a biocompatible layer.

[0124] In certain embodiments including two or more working electrodes, one or more of the working electrodes may not have a corresponding sensing area or may have a sensing area that does not contain one or more components (e.g., an electron transfer agent and / or a catalyst) required to electrolyze the analyte. Thus, the signal at this working electrode may correspond to a background signal that can be removed from the analyte signal obtained from one or more other working electrodes associated with fully functional sensing areas, e.g., by signal subtraction.

[0125] In certain embodiments, the sensing region includes one or more electron transfer agents. Electron transfer agents that can be used are electroreducible and electrooxidizable ions or molecules with redox potentials several hundred millivolts higher or lower than the redox potential of a standard calomel electrode (SCE). Electron transfer agents can be organic, organometallic, or inorganic. Examples of organic redox species are quinones and species with quinoid structures in the oxidation state, such as Nile Blue and indophenol. Examples of organic redox species are metallocenes, including ferrocene. Examples of inorganic redox species include hexacyanoferrate(III), ruthenium hexamine, and the like. Further examples include those described in U.S. Pat. Nos. 6,736,957, 7,501,053, and 7,754,093, the disclosures of each of which are incorporated herein by reference in their entirety.

[0126] In certain embodiments, the electron transfer agent has a structure or charge that prevents or substantially reduces diffusional loss of the electron transfer agent during the period the sample is being analyzed. For example, electron transfer agents include, but are not limited to, redox species bound to a polymer, which may then be placed on or near the working electrode. The bond between the redox species and the polymer may be covalent, coordinate, or ionic. While any organic, organometallic, or inorganic redox species can be bound to a polymer and used as an electron transfer agent, in certain embodiments, the redox species is a transition metal compound or complex, such as an osmium, ruthenium, iron, or cobalt compound or complex. It will be appreciated that many redox species described for use with a polymer component may also be used without the polymer component.

[0127] An embodiment of the polymeric electron transport agent may contain a redox species covalently bound to the polymer composition. An example of this type of mediator is poly(vinylferrocene). Another type of electron transport agent contains an ionically bound redox species. This type of mediator may include a charged polymer bound to an oppositely charged redox species. An example of this type of mediator includes a negatively charged polymer bound to a positively charged redox species, such as an osmium or ruthenium polypyridyl cation. Another example of an ionically bound mediator is a positively charged polymer containing quaternized poly(4-vinylpyridine) or poly(1-vinylimidazole) bound to a negatively charged redox species, such as ferricyanide or ferrocyanide. In other embodiments, the electron transport agent includes a redox species coordinatively bound to the polymer. For example, a mediator can be formed by coordinating an osmium or cobalt 2,2'-bipyridyl complex to poly(1-vinylimidazole) or poly(4-vinylpyridine).

[0128] Suitable electron transport agents are osmium transition metal complexes having one or more ligands, each of which has a nitrogen-containing heterocycle such as 2,2'-bipyridine, 1,10-phenanthroline, 1-methyl,2-pyridylbiimidazole, or a derivative thereof. The electron transport agent may have one or more ligands covalently attached to a polymer, each of which has at least one nitrogen-containing heterocycle such as pyridine, imidazole, or a derivative thereof. One example of an electron transport agent includes (a) a polymer or copolymer having pyridine or imidazole functional groups and (b) an osmium cation complexed with two ligands, each of which is 2,2'-bipyridine, 1,10-phenanthroline, or a derivative thereof, where the two ligands are not necessarily the same. Some derivatives of 2,2'-bipyridine for complexing with osmium cations include, but are not limited to, mono-, di-, and polyalkoxy-2,2'-bipyridines, including 4,4'-dimethyl-2,2'-bipyridine and 4,4'-dimethoxy-2,2'-bipyridine. Derivatives of 1,10-phenanthroline for complexing with osmium cations include, but are not limited to, mono-, di-, and polyalkoxy-1,10-phenanthrolines, such as 4,7-dimethyl-1,10-phenanthroline and 4,7-dimethoxy-1,10-phenanthroline. Polymers for complexing with osmium cations include, but are not limited to, polymers and copolymers of poly(1-vinylimidazole) (referred to as "PVI") and poly(4-vinylpyridine) (referred to as "PVP"). Suitable copolymer substituents of poly(1-vinylimidazole) include acrylonitrile, acrylamide, and substituted or quaternized N-vinylimidazole, e.g., electron transport agents having osmium complexed to a polymer or copolymer of poly(1-vinylimidazole).

[0129] Embodiments can use electron transfer agents having a redox potential ranging from about -200 mV to about +200 mV versus a standard calomel electrode (SCE). The sensing region can also include a catalyst capable of catalyzing a reaction of the analyte. In some embodiments, the catalyst can also function as an electron transfer agent. One example of a suitable catalyst is an enzyme that catalyzes a reaction of the analyte. When the analyte of interest is glucose, catalysts including, for example, glucose oxidase, glucose dehydrogenase (e.g., pyrroloquinoline quinone (PQQ)-dependent glucose dehydrogenase, flavin adenine dinucleotide (FAD)-dependent glucose dehydrogenase, or nicotinamide adenine dinucleotide (NAD)-dependent glucose dehydrogenase) can be used. When the analyte of interest is lactate, lactate oxidase or lactate dehydrogenase can be used. Laccase can be used when the analyte of interest is oxygen, or when oxygen is produced or consumed in response to a reaction of the analyte.

[0130] In certain embodiments, the catalyst can be bound to a polymer, cross-linking the catalyst to another electron transfer agent, which can be a polymer as described above. In certain embodiments, a second catalyst can also be used. This second catalyst can be used to catalyze the reaction of a product compound resulting from the catalytic reaction of the analyte. The second catalyst can work in conjunction with the electron transfer agent to electrolyze the product compound and generate a signal at the working electrode. Alternatively, the second catalyst can be provided in the interferent removal layer to catalyze the reaction that removes the interferent.

[0131] In certain embodiments, the sensor operates at a low oxidation potential, e.g., about +40 mV vs. Ag / AgCl. The sensing region uses, for example, an osmium (Os)-based mediator designed for low-potential operation. Thus, in certain embodiments, the sensing element is a redox-active component comprising (1) an osmium-based mediator molecule containing a (bidentate) ligand, and (2) a glucose oxidase enzyme molecule. These two components are combined together in the sensing region of the sensor.

[0132] A mass transport limiting layer (not shown), e.g., an analyte flux regulating layer, is included in the sensor and acts as a diffusion-limiting barrier, slowing the mass transport rate of the analyte, e.g., glucose, lactate, or ketone, into the region surrounding the working electrode. Mass transport limiting layers are useful for limiting the flux of analytes to the working electrode in electrochemical sensors so that the sensor responds linearly over a wide range of analyte concentrations and is easily calibrated. Mass transport limiting layers may include polymers and may be biocompatible. Mass transport limiting layers can provide many functions, such as biocompatibility and / or interferent removal.

[0133] In certain embodiments, the mass transport limiting layer is a membrane composed of a crosslinked polymer containing heterocyclic nitrogen groups, such as polymers of polyvinylpyridine and polyvinylimidazole. Embodiments include membranes made of polyurethane, or polyetherurethane, or chemically related materials, or membranes made of silicone, etc.

[0134] Membranes can be formed by in situ crosslinking in an alcoholic buffer solution of polymers modified with zwitterionic moieties, non-pyridine copolymer components, and, optionally, other moieties that are either hydrophilic or hydrophobic and / or have other desirable properties. The modified polymer can be made from a precursor polymer containing heterocyclic nitrogen groups. For example, the precursor polymer can be polyvinylpyridine or polyvinylimidazole. Optionally, hydrophilic or hydrophobic modifiers can be used to "fine-tune" the permeability of the resulting membrane to analytes of interest. Optional hydrophilic modifiers, such as poly(ethylene glycol), hydroxyl, or polyhydroxyl modifiers, can be used to enhance the biocompatibility of the polymer or the resulting membrane.

[0135] The membrane can be formed in situ by applying an alcohol-buffered solution of the crosslinker and modified polymer onto the enzyme-containing sensing area and allowing the solution to cure for approximately 1-2 days or other suitable period. The crosslinker-polymer solution can be applied to the sensing area by placing one or more droplets of the membrane solution on the sensor, immersing the sensor in the membrane solution, spraying the membrane solution onto the sensor, etc. Generally, the thickness of the membrane is controlled by the concentration of the membrane solution, the number of droplets of membrane solution applied, the number of times the sensor is immersed in the membrane solution, the amount of membrane solution sprayed onto the sensor, or any combination of these factors. The membrane applied in this manner can have any combination of the following functions: (1) mass transport limitation, e.g., reducing the flux of analytes that can reach the sensing area; (2) biocompatibility enhancement; or (3) interferent reduction.

[0136] In some cases, the membrane may form one or more bonds with the sensing region. By bond, we mean any type of interaction between atoms or molecules that allows chemical compounds to associate with each other, including, but not limited to, covalent bonds, ionic bonds, dipole-dipole interactions, hydrogen bonds, London dispersion forces, etc. For example, in situ polymerization of the membrane may form crosslinks between the membrane polymer and the sensing region polymer. In certain embodiments, crosslinking the membrane to the sensing region helps reduce the occurrence of delamination of the membrane from the sensing region.

[0137] The substrate can be formed using a variety of non-conductive materials, including, for example, polymeric or plastic materials and ceramic materials. The material suitable for a particular sensor can be determined, at least in part, based on the desired application of the sensor and the properties of the material.

[0138] In some embodiments, the substrate is flexible. For example, if the sensor is configured for implantation in a user, the sensor may be made flexible to reduce pain to the user and tissue damage caused by implanting and / or wearing the sensor (although rigid sensors may be used for implantable sensors). Flexible substrates often increase user comfort and allow a wider range of activities. Suitable materials for flexible substrates include, for example, non-conductive plastic or polymer materials and other non-conductive, flexible, deformable materials. Examples of useful plastic or polymer materials include thermoplastics such as polycarbonate, polyester (e.g., Mylar™ and polyethylene terephthalate (PET)), polyvinyl chloride (PVC), polyurethane, polyether, polyamide, polyimide, or copolymers of these thermoplastics, such as PETG (glycol-modified polyethylene terephthalate).

[0139] In other embodiments, sensors are fabricated using a relatively rigid substrate, for example, to provide structural support against bending or fracture. Examples of rigid materials that can be used as substrates include poorly conductive ceramics, such as aluminum oxide and silicon dioxide. Implantable sensors with rigid substrates may have sharp tips and / or sharp edges to aid in implanting the sensor without an additional insertion device.

[0140] It will be appreciated that for many sensors and sensor applications, both rigid and flexible sensors will work appropriately. The flexibility of the sensor may be controlled and varied along a continuum, for example, by varying the composition and / or thickness of the substrate.

[0141] In addition to considerations regarding flexibility, it is often desirable for implantable sensors to have a substrate that is physiologically harmless, eg, a substrate that has been approved by a regulatory or civil agency for use in vivo.

[0142] The sensor may include optional features that facilitate insertion of the implantable sensor. For example, the sensor may have a pointed tip to facilitate insertion. Additionally, the sensor may include barbs that help secure the sensor within the user's tissue during operation. However, the barbs are typically small enough to cause little damage to the subcutaneous tissue when the sensor is removed for replacement.

[0143] The implantable sensor may also optionally have an anticoagulant disposed on the portion of the substrate that is implanted in the user. This anticoagulant can reduce or eliminate clotting of blood or other bodily fluids around the sensor, particularly after insertion of the sensor. Blood clots can clog the sensor or irreproducibly reduce the amount of analyte that diffuses into the sensor. Examples of useful anticoagulants include heparin and tissue plasminogen activator (TPA), as well as other known anticoagulants.

[0144] The anticoagulant may be applied to at least a portion of the portion of the sensor that will be implanted. The anticoagulant may be applied, for example, by bathing, spraying, brushing, or dipping. The anticoagulant may be dried onto the sensor. The anticoagulant may be immobilized on the surface of the sensor or may diffuse from the sensor surface. The amount of anticoagulant placed on the sensor may be less than the amount typically used to treat medical conditions involving blood clots and, therefore, may have only a limited local effect.

[0145] FIG. 11 illustrates an exemplary in-vivo-based analyte monitoring system 1100 in accordance with certain embodiments of the present disclosure. As shown, the analyte monitoring system 1100 includes on-body electronics 1110 electrically coupled to an in-vivo analyte sensor 1101 (a proximal portion of which is shown in FIG. 11 ) and attached to an adhesive layer 1140 for attachment to a skin surface on a user's body. The on-body electronics 1110 includes an on-body housing 1119 that defines an internal compartment. Also shown in FIG. 11 is an insertion device 1150 that, during operation, transcutaneously positions a portion of the analyte sensor 1101 in fluid contact with bodily fluids through the skin surface, and positions the portion of the analyte sensor 1101 on the skin surface and over the on-body electronics 1110 and adhesive layer 1140. In certain embodiments, the on-body electronics 1110, analyte sensor 1101, and adhesive layer 1140 are sealed within the housing of the insertion device 1150 prior to use, and in certain embodiments, the adhesive layer 1140 is also sealed within the housing or itself provides an end seal for the insertion device 1150.

[0146] Referring back to FIG. 11 , the analyte monitoring system 1100 includes a display device 1120 including a display 1122 for outputting information to a user, and input components 1121, such as buttons, actuators, touch-sensitive switches, capacitive switches, pressure-sensitive switches, jog wheels, etc., for inputting data or commands into the display device 1120 or for controlling the operation of the display device 1120. Note that some embodiments may include devices without a display or without any user interface components. These devices may be functionalized to store data as data loggers and / or provide a conduit for transferring data from on-body electronics and / or the display-less device to another device and / or location. The embodiments are described herein as display devices for illustrative purposes, which are not intended to limit the embodiments of the present disclosure in any way. It will be apparent that display-less devices may also be used in certain embodiments.

[0147] In certain embodiments, the on-body electronics 1110 may be configured to store some or all of the monitored analyte-related data received from the analyte sensor 1101 during the monitoring period in memory and maintain it in memory until the end of the usage period. In such embodiments, the stored data is retrieved from the on-body electronics 1110 at the end of the monitoring period, for example, after the analyte sensor 1101 is removed from the user by removing the on-body electronics 1110 from the skin surface where it was placed during the monitoring period. In such a data logging configuration, the real-time monitored analyte levels are not communicated to the display device 1120 or transmitted from the on-body electronics 1110 during the monitoring period, but rather are retrieved from the on-body electronics 1110 after the monitoring period.

[0148] In particular embodiments, the input component 1121 of the display device 1120 may include a microphone, and the display device 1120 may include software configured to analyze audio input received from the microphone, so that the functions and operations of the display device 1120 may be controlled by voice commands. In particular embodiments, the output component of the display device 1120 includes a speaker for outputting information as an audible signal. Similar voice response components, such as a speaker, a microphone, and software routines for generating, processing, and storing voice drive signals, may be provided with the on-body electronics 1110.

[0149] In particular embodiments, the display 1122 and input component 1121 may be integrated into a single component, e.g., a display capable of detecting the presence and location of physical contact touches on the display, such as a touchscreen user interface. In such embodiments, a user can control the operation of the display device 1120 by utilizing a set of pre-programmed movement commands, including, but not limited to, single-tapping or double-tapping the display, dragging a finger or instrument across the display, moving multiple fingers or instruments toward each other, moving multiple fingers or instruments away from each other, etc. In particular embodiments, the display includes a touchscreen having a pixel area with an LCD element and single- or dual-function capacitive elements that function as touch sensors.

[0150] The display device 1120 also includes a data communication port 1123 for wired data communication with an external device such as, for example, a remote terminal (personal computer) 1170. Exemplary embodiments of the data communication port 1123 include a USB port, a mini-USB port, an RS-232 port, an Ethernet port, a Firewire port, or other similar data communication port configured to connect to a compatible data cable. The display device 1120 may also include an integrated in-vitro glucose meter that includes an in-vitro test strip port 1124 for accepting in-vitro glucose test strips for performing in-vitro blood glucose measurements.

[0151] 11 , the display 1122 in certain embodiments is configured to display a variety of information, some or all of which may be displayed on the display 1122 simultaneously or at different times. In certain embodiments, the displayed information is user-selectable, allowing a user to customize the information shown on a given display screen. The display 1122 may include, but is not limited to, a graphical display 1138 (which may show key markers such as diet, exercise, sleep, heart rate, blood pressure, etc.) that provides a graphical output of, for example, ketone levels over a monitored period of time, a numeric display 1132 that provides, for example, monitored ketone values ​​(obtained or received in response to a request for information), and a trend or directional arrow display 1131 that indicates the rate of analyte change and / or the rate of the rate of analyte change.

[0152] 11 , the display 1122 may also include, for example, a date display 1135 that provides date information for the user, a time information display 1139 that provides time information to the user, a battery level indicator display 1133 that graphically indicates the status of the battery (rechargeable or disposable) of the display device 1120, a sensor calibration status icon display 1134 that notifies the user that analyte sensor calibration is required, for example, in monitoring systems that require periodic, routine, or a predetermined number of user calibration events, an audio / vibration settings icon display 1136 to indicate the status of audio / vibration outputs or an alarm status, and a wireless connectivity status icon display 1137 that provides an indication of wireless communication connectivity with other devices, such as on-body electronics, a data processing module 1160, and / or a remote terminal 1170. As additionally shown in FIG. 11 , the display 1122 may further include simulated touchscreen buttons 1140, 1141 for accessing menus, changing display graph output configurations, or otherwise controlling the operation of the display device 1120.

[0153] 11 , in certain embodiments, the display 1122 of the display device 1120 may be configured to output alarm and / or alert notifications, such as glucose values, which may be audible, tactile, or any combination thereof, in addition to a visual display. In one aspect, the display device 1120 may include other output components, such as a speaker, a vibration output component, etc., to provide audible and / or vibration output indications to the user in addition to the visual output indications provided on the display 1122.

[0154] After placing the on-body electronics 1110 on the skin surface to establish fluid contact with interstitial fluid (or other suitable bodily fluid) and placing the analyte sensor 1101 in vivo, the on-body electronics 1110 in certain embodiments is configured to wirelessly communicate analyte-related data (e.g., monitored analyte level and / or monitored temperature data, and / or data corresponding to stored historical analyte-related data, etc.) when the on-body electronics 1110 receives a command or request signal from the display device 1120. In certain embodiments, the on-body electronics 1110 may be configured to at least periodically broadcast real-time data associated with the monitored analyte level that is received by the display device 1120 when the display device 1120 is within communication range of the data broadcast from the on-body electronics 1110, e.g., without requiring a command or request from the display device to transmit the information.

[0155] For example, the display device 1120 may be configured to send one or more commands to the on-body electronics 1110 to initiate a data transfer, and in response, the on-body electronics 1110 may be configured to wirelessly transmit stored analyte-related data collected during the monitoring period to the display device 1120. The display device 1120 may be connected to a remote terminal 1170, such as a personal computer, and serve as a data conduit for transferring stored analyte level information from the on-body electronics 1110 to the remote terminal 1170. In certain embodiments, data received from the on-body electronics 1110 may be stored (permanently or temporarily) in one or more memories of the display device 1120. In certain other embodiments, the display device 1120 is configured as a data conduit for passing data received from the on-body electronics 1110 to the remote terminal 1170 connected to the display device 1120.

[0156] 11 , the analyte monitoring system 1100 also includes a data processing module 1160 and a remote terminal 1170. The remote terminal 1170 may include a personal computer, a server terminal, a laptop computer, or other suitable data processing device including software for data management and analysis and communication with components within the analyte monitoring system 1100. For example, the remote terminal 1170 may be connected to a local area network (LAN), a wide area network (WAN), or other data network for unidirectional or bidirectional data communication between the remote terminal 1170 and the display device 1120 and / or the data processing module 1160.

[0157] Remote terminal 1170 in certain embodiments may include one or more computer terminals located in a doctor's office or a hospital. For example, remote terminal 1170 may be located at a location other than the location of display device 1120. Remote terminal 1170 and display device 1120 may be in different rooms or different buildings. Remote terminal 1170 and display device 1120 may be at least about 1 mile (about 1.609 kilometers) apart, such as at least about 10 miles (about 16.09 kilometers) apart, or such as at least about 1100 miles (about 1770 kilometers) apart. For example, remote terminal 1170 may be in the same city as display device 1120, remote terminal 1170 may be in a different city than display device 1120, remote terminal 1170 may be in the same state as display device 1120, remote terminal 1170 may be in a different state than display device 1120, remote terminal 1170 may be in the same country as display device 1120, or remote terminal 1170 may be in a different country than display device 1120.

[0158] In certain embodiments, a separate optional data communication / processing device, such as a data processing module 1160, may be provided in the analyte monitoring system 1100. The data processing module 1160 may include components for communicating using one or more wireless communication protocols, such as, but not limited to, infrared (IR), Bluetooth, Zigbee, and 802.11 wireless LAN protocols. Additional descriptions of communication protocols, including those based on the Bluetooth and / or Zigbee protocols, can be found in U.S. Patent Application Publication No. 2006 / 0193375, which is incorporated herein by reference in its entirety for all purposes. The data processing module 1160 may further include communication ports, drivers, or connectors for establishing wired communication with one or more of the display device 1120, the on-body electronics 1110, or the remote terminal 1170, including, but not limited to, a USB connector and / or port, an Ethernet connector and / or port, a FireWire connector and / or port, or an RS-232 port and / or connector.

[0159] In certain embodiments, the data processing module 1160 is programmed to send polling or query signals to the on-body electronics 1110 at predetermined time intervals (e.g., once per minute, once every five minutes, etc.) and, in response, receive monitored analyte level information from the on-body electronics 1110. The data processing module 1160 stores the received analyte level information in its memory and / or relays or retransmits the received information to another device, such as the display device 1120. More specifically, in certain embodiments, the data processing module 1160 may be configured as a data relay device to retransmit or pass on the received analyte level data from the on-body electronics 1110 to the display device 1120 or a remote terminal (e.g., via a data network such as a cellular or WiFi data network), or both.

[0160] In certain embodiments, the on-body electronics 1110 and the data processing module 1160 may be positioned on the user's skin surface within a predetermined distance from each other (e.g., about 1-12 inches (about 25.4-304.8 mm), or about 1-10 inches (about 25.4-254 mm), or about 1-7 inches (about 25.4-177.8 mm), or about 1-5 inches (about 25.4-127 mm)) such that periodic communication is maintained between the on-body electronics 1110 and the data processing module 1160. Alternatively, the data processing module 1160 may be attached to the user's belt or clothing, thereby maintaining a desired communication distance between the on-body electronics 1110 and the data processing module 1160 for data communication. In a further aspect, the housing of the data processing module 1160 is configured to couple or engage with the on-body electronics 1110, such that the two devices are combined or integrated into a single assembly that can be placed on the skin surface. In a further embodiment, the data processing module 1160 is removably engaged or connected to the on-body electronics 1110, providing additional modularity such that the data processing module 1160 can be optionally removed or reattached as desired.

[0161] 11 , in certain embodiments, the data processing module 1160 is programmed to send a command or signal to the on-body electronics 1110 to request analyte-related data from the on-body electronics 1110 at predetermined time intervals, such as once per minute, once per five minutes, once per 30 minutes, or any other suitable or desired programmable time interval. Upon receiving the requested analyte-related data, the data processing module 1160 stores the received data. In this manner, the analyte monitoring system 1100 may be configured to receive continuously monitored analyte-related information at programmed or programmable time intervals, which may be stored and / or displayed to a user. The data stored in the data processing module 1160 may then be provided or transmitted to a display device 1120, a remote terminal 1170, or the like for subsequent data analysis, such as identifying the frequency of periods of blood glucose level fluctuations over a monitored period or the frequency of alarm event occurrences during a monitored period, for example, to improve therapy-related decisions. Using this information, a doctor, healthcare provider, or user can adjust or recommend modifications to diet, daily habits, and routines such as exercise.

[0162] In another embodiment, the data processing module 1160 sends a command or signal to the on-body electronics 1110 to receive analyte-related data in response to user activation of a switch provided on the data processing module 1160 or a user-initiated command received from the display device 1120. In further embodiments, the data processing module 1160 is configured to send a command or signal to the on-body electronics 1110 in response to receiving a user-initiated command only after a predetermined time interval has elapsed. For example, in certain embodiments, the data processing module 1160 may be programmed to automatically send a request command or signal to the on-body electronics 1110 if the user does not initiate communication within a programmed time period, such as, for example, about 5 hours since the last communication (or 10 hours since the last communication, or 24 hours since the last communication). Alternatively, the data processing module 1160 may be programmed to activate an alarm to notify the user that a predetermined period of time has elapsed since the last communication between the data processing module 1160 and the on-body electronics 1110. In this manner, the user or healthcare provider programs or configures the data processing module 1160 to provide specific compliance with the analyte monitoring plan, so that frequent determinations of analyte levels are maintained or performed by the user.

[0163] In certain embodiments, when a programmed or programmable alarm condition is detected (e.g., when a detected glucose level monitored by the analyte sensor 1101 is outside a predetermined tolerance range indicating a physiological condition requiring attention or intervention for medical treatment or analysis (e.g., ketosis, diabetic ketoacidosis, impending ketosis, impending diabetic ketoacidosis)), one or more output indications may be generated by the control logic or processor of the on-body electronics 1110 and output to a user on a user interface of the on-body electronics 1110 so that corrective action can be taken in a timely manner. Additionally or alternatively, if the display device 1120 is within communication range, the output indication or alarm data may be communicated to the display device 1120, and the processor of the display device 1120 controls the display 1122 to output one or more notifications upon detection of receipt of the alarm data.

[0164] In certain embodiments, the control logic or processor of the on-body electronics 1110 can execute a software program stored in memory to determine future or predicted analyte levels based on information obtained from the analyte sensor 1101, such as the current analyte level, the rate of change of the analyte level, the acceleration of the analyte level change, and / or analyte trend information determined based on stored monitored analyte data providing a historical trend or direction of analyte level fluctuations as a function of time during a monitoring period. Predictive alarm parameters may be programmed or programmable in the display device 1120, or the on-body electronics 1110, or both, and output to the user before their analyte level is predicted to reach a future level. This provides the user with an opportunity to take timely corrective action.

[0165] For example, information such as the change or variation in the monitored analyte level as a function of time over a monitored period, providing analyte trend information, may be determined by the control logic or processor of one or more of the display device 1120, the data processing module 1160, and / or the remote terminal 1170, and / or the on-body electronics 1110. Such information may be displayed, for example, as a graph (such as a line graph) to show the user the current and / or past and / or predicted future analyte levels measured and predicted by the analyte monitoring system 1100. Such information may be displayed as a directional arrow (see, for example, trend or directional arrow display 1131) or other icon(s) whose position on the screen relative to a reference point indicates whether the analyte level is increasing or decreasing, as well as the acceleration or deceleration of the analyte level increase or decrease. This information may be utilized by the user to determine any necessary corrective actions to ensure that the analyte level remains within an acceptable and / or clinically safe range. Other visual indicators, including color, flashing, fading, etc., as well as audio indicators, including changes in pitch, volume, or tone of an audio output, and / or vibration or other tactile indicators, may also be incorporated into the display of trend data as a means of notifying the user of the current level and / or direction and / or rate of change of the monitored analyte level. For example, based on the determined glucose rate of change, programmed clinically significant glucose threshold levels (e.g., hyperglycemic and / or hypoglycemic levels), and the current analyte level derived by the in-vivo analyte sensor, the system 1100 may include an algorithm stored in a computer-readable medium for determining the time it will take to reach a clinically significant level and outputting a notification, such as increasing the intensity of the output, before the clinically significant level is reached, e.g., 30 minutes, and / or 20 minutes, and / or 10 minutes, and / or 5 minutes, and / or 3 minutes, and / or 1 minute, etc., before the clinically significant level is predicted.

[0166] 11 , in particular embodiments, the software algorithm(s) executed by the data processing module 1160 may be stored on an external memory device, such as an SD card, microSD card, CompactFlash card, XD card, Memory Stick card, Memory Stick Duo card, or USB memory stick / device, and include an executable program stored on such device for execution upon connection to one or more of the on-body electronics 1110, remote terminal 1170, or display device 1120, respectively. In further aspects, the software algorithms for execution by the data processing module 1160 may be provided as a downloadable application for execution by the downloading communication device, such as, for example, a communication device, such as a mobile phone, including a WiFi or Internet-enabled smartphone or personal digital assistant (PDA).

[0167] Examples of smartphones include mobile phones based on the Windows®, Android™, iPhone® operating systems, Palm® WebOS™, Blackberry® operating system, or Symbian® operating system, equipped with data network connectivity for data communication over an Internet connection and / or a local area network (LAN). A PDA, such as those described above, includes a portable electronic device configured to perform, for example, data processing, data upload / download over the Internet, and includes one or more processors and data communication capabilities with a user interface (e.g., a display / output unit and / or an input unit). In such an embodiment, the remote terminal 1170 may be configured to provide executable application software to one or more of the aforementioned communication devices when communication between the remote terminal 1170 and the device is established.

[0168] On-Body Electronics In certain embodiments, the on-body electronics (or sensor control device) 1110 ( FIG. 11 ) includes at least some of the electronic components that operate the sensors and display device. The electronic components of the on-body electronics typically include a power source for operating the on-body electronics and sensors, a sensor circuit for acquiring signals from the sensors and operating the sensors, a measurement circuit for converting the sensor signals into a desired format, and at least a processing circuit (or processing electronics) for acquiring signals from the sensor circuit and / or measurement circuit and providing the signals to optional on-body electronics. In some embodiments, the processing circuit partially or fully evaluates the signals from the sensors and communicates the resulting data to optional on-body electronics and / or may activate an optional alarm system if the analyte level exceeds a threshold. The processing circuit often includes digital logic circuitry.

[0169] The on-body electronics may optionally include electronics for transmitting the sensor signals or processed data from the processing circuitry to a receiver / display unit, a data storage unit for temporarily or permanently storing data from the processing circuitry, a temperature probe circuit for receiving signals from and operating the temperature probe, a reference voltage generator for providing a reference voltage for comparison with the sensor-generated signal, and / or a watchdog circuit for monitoring operation of electronic components within the on-body electronics.

[0170] Additionally, the on-body electronics may also include digital and / or analog components that utilize semiconductor devices, including transistors. To operate these semiconductor devices, the on-body electronics may include other components, including, for example, bias control generators for precisely biasing the analog and digital semiconductor devices, oscillators for providing clock signals, and digital logic and timing components for providing timing signals and logic operations for the digital components of the circuit.

[0171] As an example of the operation of these components, the sensor circuit and optional temperature probe circuit provide a raw signal from the sensor to a measurement circuit. The measurement circuit converts the raw signal into a desired format, for example, using a current-to-voltage converter, a current-to-frequency converter, and / or a binary counter or other indicator that generates a signal proportional to the absolute value of the raw signal. This may be used, for example, to convert the raw signal into a format that can be used by digital logic circuitry. A processing circuit may then optionally evaluate the data and provide commands to operate the electronics.

[0172] FIG. 12 is a block diagram of the on-body electronics 1110 (FIG. 11) in certain embodiments. Referring to FIG. 12, the on-body electronics 1110 in certain embodiments includes a control unit 1210 (e.g., without limitation, one or more processors (or processing circuits) and / or ASICs comprising processing circuits) operably coupled to an analog front-end circuit 1270 to process signals, such as raw current signals, received from the analyte sensor 1101. Also shown in FIG. 12 is a memory 1220 operably coupled to the control unit 1210 for storing data and / or software routines for execution by the control unit 1210. The memory 1220 in certain embodiments may include an electrically erasable programmable read-only memory (EEPROM), an erasable programmable read-only memory (EPROM), a random access memory (RAM), a read-only memory (ROM), a flash memory, or one or more combinations thereof.

[0173] In certain embodiments, the control unit 1210, in addition to retrieving one or more stored software routines for execution, also accesses data or software routines stored in memory 1220 to update, store, or replace stored data or information in memory 1220. Also shown in FIG. 12 is a power source 1260, which, in certain embodiments, provides power to some or all of the components of the on-body electronics 1110. For example, in certain embodiments, the power source 1260 is configured to provide power to the components of the on-body electronics 1110 except for the communications module 1240. In such embodiments, the on-body electronics 1110 is configured to operate the analyte sensor 1101 to detect and monitor analyte levels at predetermined or programmed (or programmable) time intervals, and to generate and store, for example, a signal or data corresponding to the detected analyte level.

[0174] In particular embodiments, the power source 1260 of the on-body electronics 1110 may be switched between its internal power source (e.g., a battery) and RF power received from the display device 1120. For example, in particular embodiments, the on-body electronics 1110 may include a diode or switch in the internal power connection path within the on-body electronics 1110 such that when a predetermined level of RF power is detected by the on-body electronics 1110, the diode or switch is triggered to disable the internal power connection (e.g., create an open circuit in the power connection path) and the on-body electronics components are powered by the received RF power. The open circuit in the power connection path prevents the internal power source from being depleted or dissipated, as would be the case if an internal power source were used to power the on-body electronics 1110.

[0175] When the RF power from the display device 1120 falls below a predetermined level, a diode or switch is triggered to establish a connection between the internal power source and other components of the on-body electronics 1110, powering the on-body electronics 1110 with the internal power source. In this manner, in some embodiments, toggling between the internal power source and RF power from the display device 1120 may be configured to increase or extend the useful life of the internal power source.

[0176] However, the stored analyte-related data is not transmitted or communicated to another device, such as the display device 1120 (FIG. 11), until the communications module 1240 is separately powered, for example, with RF power from a display device 1120 located within a predetermined distance from the on-body electronics 1110. In such an embodiment, the analyte level is sampled based on predetermined or programmed time intervals as described above and stored in the memory 1220. When analyte level information is requested, for example, based on a request or send command received from another device, such as the display device 1120 (FIG. 11), using RF power from the display device, the communications module 1240 of the on-body electronics 1110 initiates data transfer to the display device 1120.

[0177] 12 , an optional output unit 1250 is provided on the on-body electronics 1110. In particular embodiments, the output unit 1250 may include an LED indicator, for example, to alert the user of one or more predetermined conditions related to the operation of the on-body electronics 1110 and / or the determined analyte level. As a non-limiting example, the on-body electronics 1110 may be programmed to assert a notification using an LED indicator or other indicator on the on-body electronics 1110 when a signal received from the analyte sensor 1101 (based on one sampled sensor data point or multiple sensor data points) indicates that the signal is outside a programmed tolerance range, potentially indicating a health risk condition such as hyperglycemia or hypoglycemia, or the onset or likelihood of such a condition. Using such a prompt or indication, the user may be timely informed of such a potential condition, and the display device 1120 may be used to obtain glucose level information from the on-body electronics 1110 to confirm the existence of such a condition so that timely corrective action can be taken.

[0178] 12 , the antenna 1230 and communication module 1240 operably coupled to the control unit 1210 may be configured to detect and process RF power when the on-body electronics 1110 is positioned within a predetermined proximity of the display device 1120 ( FIG. 11 ) that is providing or radiating RF power. Furthermore, the on-body electronics 1110 may provide analyte level information and optionally analyte trend or historical information to the display device 1120 based on stored analyte level data. In certain embodiments, the trend information may include multiple analyte level information over a predetermined period of time that is stored in the memory 1220 of the on-body electronics 1110 and provided to the display device 1120 along with the real-time analyte level information. For example, the trend information may include analyte level data for a series of time intervals since the analyte level information was last transmitted to the display device 1120. Alternatively, the trend information may include analyte level data for the past 30 minutes or 1 hour that is stored in the memory 1220 and retrieved under the control of the control unit 1210 for transmission to the display device 1120.

[0179] In certain embodiments, the on-body electronics 1110 is configured to store analyte level data in first and second FIFO buffers that are part of the memory 1220. The first FIFO buffer stores 16 (or 10 or 20) of the most recent analyte level data at 1-minute intervals. The second FIFO buffer stores the most recent 8 hours (or 10 hours or 3 hours) of analyte level data at 10-minute (or 15-minute or 20-minute) intervals. The stored analyte level data is transmitted from the on-body electronics 1110 to the display unit 1120 in response to a request received from the display unit 1120. The display unit 1120 uses the analyte level data from the first FIFO buffer to estimate the glucose rate of change and the analyte level data from the second FIFO buffer to determine historical plots or trend information.

[0180] In certain embodiments, with respect to the configuration of the on-body electronics, including the power source, the on-body electronics may be configured to detect RF control commands (ping signals) from the display device 1120. More specifically, an on / off key (OOK) detector is provided within the on-body electronics and is turned on and powered by the on-body electronics power source to detect RF control commands or ping signals from the display device 1120. Further details of the OOK detector are provided in U.S. Patent Application Publication No. 2008 / 0278333, the disclosure of which is incorporated by reference in its entirety for all purposes. In some aspects, upon detection of an RF control command, the on-body electronics determines which response packet is required and generates the response packet for transmission back to the display device 1120. In this embodiment, the analyte sensor 1101 continuously receives power from the on-body electronics power source or battery and operates to continuously monitor the analyte level during use. However, the sampled signal from the analyte sensor 1101 may not be provided to the display device 1120 until the on-body electronics receives RF power (from the display device 1120) and begins transmitting data to the display device 1120. In one embodiment, the power source for the on-body electronics may include a rechargeable battery that charges when the on-body electronics receives RF power (e.g., from the display device 1120).

[0181] 11 , in certain embodiments, the on-body electronics 1110 and the display device 1120 may be configured to communicate using an RFID (radio frequency identification) protocol. More specifically, in certain embodiments, the display device 1120 is configured to interrogate the on-body electronics 1110 (associated with an RFID tag) via an RF communications link, and in response to an RF interrogation signal from the display device 1120, the on-body electronics 1110 provides an RF response signal including data associated with, for example, a sampled analyte level from the sensor 1101. Further information regarding the operation of RFID communications can be found in U.S. Pat. No. 7,545,272, U.S. Patent Application Nos. 12 / 698,624, 12 / 699,653, 12 / 761,387, and U.S. Patent Application Publication No. 2009 / 0108992, the disclosures of all of which are incorporated herein by reference in their entirety for all purposes.

[0182] For example, in one embodiment, the display device 1120 may include a backscatter RFID reader configured to provide an RF field, and when the on-body electronics 1110 is within the transmitted RF field of the RFID reader, an antenna of the on-body electronics 1110 is tuned and then provides a reflected or response signal (e.g., a backscatter signal) to the display device 1120. The reflected or response signal may include sampled analyte level data from the analyte sensor 1101.

[0183] In certain embodiments, when the display device 1120 is positioned within a predetermined range of the on-body electronics 1110 and receives a response signal from the on-body electronics 1110, the display device 1120 is configured to output an indication (audible, visual, or other) confirming the acquisition of an analyte level measurement. That is, at any time during the 5-10 days that the user is wearing the on-body electronics 1110, the user can position the display device 1120 within a predetermined distance (e.g., about 1-5 inches (about 25.4-127 mm), or about 1-10 inches (about 25.4-254 mm), or about 1-12 inches (about 25.4-304.8 mm)) from the on-body electronics 1110, and after waiting a sample acquisition period of several seconds, an audible indication confirming receipt of real-time analyte level information will be output. The received analyte information may be output on the display 1122 of the display device 1120 (FIG. 11) for presentation to the user.

[0184] Display device Figure 13 is a block diagram of a display device 1120 as shown in Figure 11, in a particular embodiment. Although the term display device is used, the device may be configured to read data without displaying it, and may be provided without a display, such as in the case of a relay device or other device that relays signals received according to the same or a different transmission protocol (e.g., NFC-to-Bluetooth or Bluetooth Low Energy). With reference to Figure 13, the display device 1120 (Figure 11) includes a control unit 1310, such as one or more processors (or processing circuits), operably coupled to a display 1122 and an input component (e.g., a user interface) 1121. The display device 1120 may include one or more data communication ports, such as a USB port (or connector) 1123 or an RS-232 port 1330 (or any other wired communication port), for data communication with other devices, such as a data processing module 1160 (FIG. 11), a remote terminal 1170 (FIG. 11), or other handheld data processing devices, including personal computers, servers, mobile computing devices, mobile phones, pagers, or other handheld data processing devices, including mobile phones, such as internet-enabled smartphones, with data communication and processing capabilities, including data storage and output.

[0185] 13 , the display device 1120 may include a strip port 1124 configured to accept an in vitro test strip, the strip port 1124 coupled to a control unit 1310, which further includes programming for processing a sample on an in vitro test strip accepted by the strip port 1124. Any suitable in vitro test strip may be used, for example, a test strip requiring only a very small amount of applied sample (e.g., 1 microliter or less, e.g., about 0.5 microliters or less, e.g., about 0.1 microliters or less) on the strip to obtain accurate glucose information. A display device with an integrated in vitro monitor and test strip port may be configured to perform in vitro analyte monitoring without user calibration of the in vitro test strip (e.g., without human intervention).

[0186] In certain embodiments, the integrated invitrometer can accept and process a variety of different types of test strips (e.g., those that require user calibration and those that do not), some of which may use different technologies (e.g., those that operate using amperometric technology and those that operate using coulometric technology). Detailed descriptions of such test strips and devices for performing in vitro analyte monitoring are provided in U.S. Pat. Nos. 6,377,894, 6,616,819, 7,749,740, 7,418,285, U.S. Patent Application Publication Nos. 2004 / 0118704, 2006 / 0096006, 2008 / 0066305, 2008 / 0267823, 2010 / 0094610, 2010 / 0094111, and 2010 / 0094112, and U.S. Patent Application No. 12 / 695,947, the disclosures of all of which are incorporated herein by reference in their entirety for all purposes.

[0187] The ketone information obtained by the in vitro glucose testing device may be used for a variety of purposes. For example, the information may be used to confirm the results of the analyte sensor 1101 to increase the reliability of the results from the sensor 1101 indicating the monitored analyte level (e.g., if the information obtained by the sensor 1101 is used in treatment-related decisions). In certain embodiments, the analyte sensor does not require calibration by human intervention during its useful life. However, in certain embodiments, the system may be programmed to self-detect a problem and take action, such as shutting down and / or notifying the user. For example, the analyte monitoring system may be configured to detect a system malfunction, or a potential degradation of sensor stability, or a potential adverse condition related to the operation of the analyte sensor, and the system may notify the user, for example, using the display device 1120 (FIG. 11), to perform analyte sensor calibration or to compare the results received from the analyte sensor corresponding to the monitored analyte level to a reference value (e.g., a result from an in vitro blood glucose measurement).

[0188] In certain embodiments, upon detection of a potential adverse condition related to sensor operation and / or a potential degraded sensor stability condition, the system may be configured to shut down or disable (either automatically without user notification or after user notification) the output or display of monitored analyte level information received by the on-body electronics assembly. In certain embodiments, the analyte monitoring system may be temporarily shut down or disabled to provide the user with an opportunity to correct any detected adverse condition or sensor instability. In certain other embodiments, the analyte monitoring system may be permanently disabled when an adverse sensor operating condition or sensor instability is detected.

[0189] 13 , a power source 1320, such as one or more batteries, rechargeable or single-use disposable, is also provided and operably coupled to the control unit 1310 and configured to provide the display device 1120 ( FIG. 11 ) with the power necessary for operation. In addition, the display device 1120 may include an antenna 1351, such as a 433 MHz (or other equivalent) loop antenna, a 13.56 MHz antenna, or a 2.45 GHz antenna, coupled to a receiver processor 1350 (which may include, for example, a 433 MHz, 13.56 MHz, or 2.45 GHz transceiver chip) for wireless communication with the on-body electronics 1110 ( FIG. 11 ). Additionally, an inductive loop antenna 1341 is provided and coupled to a square wave driver 1340 that is operably coupled to the control unit 1310.

[0190] In certain embodiments, the data packet received from the on-body electronics and in response to the request from the display device includes, for example, one or more of the current glucose level from the analyte sensor, the current estimated rate of blood glucose change, and glucose trend history based on automatic readings taken and stored in the memory of the skin-worn electronics. For example, the current glucose level may be output on the display 1122 of the display device 1120 as a numeric value, the current estimated range of blood glucose change may be output on the display 1122 as a directional arrow 1131 ( FIG. 11 ), and the glucose trend history based on stored monitored values ​​may be output on the display 1122 as a graphical trace 1138 ( FIG. 11 ). In certain embodiments, the processor (or processing circuitry) of the display device 1120 may be programmed to output more or less information for display on the display 1122, and further, the type and amount of information output on the display 1122 may be programmed or user-programmable.

[0191] Data Communication and Processing Routines Referring now to FIG. 14 , which illustrates data and / or command exchange between the on-body electronics 1110 and the display device 1120 during an initialization and pairing routine, the display device 1120 provides an initial signal 1421 to the on-body electronics 1110. If the received initial signal 1421 includes RF energy above a predetermined threshold level (1403), an envelope detector of the on-body electronics 1110 is triggered (1404), turning on one or more oscillators of the on-body electronics 1110 and temporarily latching on the control logic or processor of the on-body electronics 1110 to retrieve and execute one or more software routines to extract the data stream from the envelope detector (1404). If the data stream from the envelope detector returns a valid query (1405), a response signal 1422 is sent to the display device 1120. The response signal 1422 from the on-body electronics 1110 includes an identification code, such as the serial number of the on-body electronics 1110. The on-body electronics 1110 then returns to the inactive shelf mode.

[0192] On the other hand, if the data stream from the envelope detector does not return a valid query from the display device 1120, the on-body electronics 1110 does not send a response signal to the display device 1120, and the serial number of the on-body electronics 1110 is not provided to the display device 1120. The on-body electronics 1110 then returns 1403 to shelf mode and remains in a powered-down state until it detects a subsequent initial signal 1421 from the display device 1120.

[0193] When the display device 1120 receives a data packet containing identification information or a serial number from the on-body electronics 1110, it extracts that information from the data packet (1412). Using the extracted serial number of the on-body electronics 1110, the display device 1120 determines whether the on-body electronics 1110 associated with the received serial number is configured. If the on-body electronics 1110 associated with the received serial number has already been configured, for example, by another display device, the display device 1120 returns to the beginning of the routine to send another initialization signal (1411) in an attempt to initialize the other on-body electronic device that has not yet been configured. In this manner, in certain embodiments, the display device 1120 is configured to pair with on-body electronics that are not already paired with or configured by another display device.

[0194] 14 , if the on-body electronics 1110 associated with the extracted serial number has not been configured (1413), the display device 1120 is configured to send a wake-up signal to the on-body electronics 1110 that includes a configuration command. In a particular embodiment, the wake-up command from the display device 1120 includes the serial number of the on-body electronics 1110, such that only on-body electronics with the same serial number included in the wake-up command detect and exit inactive shelf mode and enter active mode. More specifically, when the wake-up command including the serial number is received by the on-body electronics 1110, the control logic or one or more processors (or processing circuits) of the on-body electronics 1110 executes routines 1403, 1404, and 1405 to temporarily exit shelf mode and determine that it is not a valid query (because that determination was previously made and the serial number was sent to the display device 1120). The on-body electronics 1110 then determines whether the received serial number (received along with the wake-up command) matches its own stored serial number 1406. If the two serial numbers do not match, the routine returns to the beginning, and the on-body electronics 1110 is again placed in inactive shelf mode (1402). On the other hand, if the on-body electronics 1110 determines that the received serial number matches its stored serial number (1406), the control logic or one or more processors of the on-body electronics 1110 permanently latch on (1407), and an oscillator is turned on to wake up the on-body electronics 1110. Further, referring back to FIG. 14 , when the on-body electronics 1110 determines that the received serial number matches its own serial number (1406), the display device 1120 and the on-body electronics 1110 are successfully paired (1416).

[0195] In this manner, using a wireless signal to power on and initialize the on-body electronics 1110 can extend the shelf life of the on-body electronics 1110 because very little current is drawn or consumed from the on-body electronics 1110's power source while the on-body electronics 1110 is in an inactive shelf mode prior to operation. In certain embodiments, during the inactive shelf mode, the on-body electronics 1110 performs minimal operations requiring very low current, if any. The RF envelope detector of the on-body electronics 1110 can operate in two modes: a reduced sensitivity mode that responds to signals received less than about 1 inch (about 25.4 mm), and a normal operating mode with normal signal sensitivity that responds to receiving signals at a distance of about 3 to 12 inches (about 76.2 to 304.8 mm).

[0196] During initial pairing between the display device 1120 and the on-body electronics 1110, in certain embodiments, the display device 1120 transmits its identification information, such as, for example, a 4-byte display device ID that may include its serial number. The on-body electronics 1110 stores the received display device ID in one or more storage units or memory components and then includes the stored display device ID data in response packets or data provided to the display device 1120. In this manner, the display device 1120 can distinguish detected data packets from the on-body electronics 1110 and determine that the received or detected data packets originated from the paired or correct on-body electronics 1110. The display device ID-based pairing routine in certain embodiments avoids potential collisions between multiple devices, particularly when the on-body electronics 1110 does not selectively provide analyte-related data to a specific display device, but rather provides it to any display device within range and / or broadcasts data packets to any display device within communication range.

[0197] In a particular embodiment, the payload size from the display device 1120 to the on-body electronics 1110 is 12 bytes, which includes 4 bytes of display device ID, 4 bytes of on-body device ID, 1 byte of command data, 1 byte of spare data space, and 2 bytes for CRC (cyclic redundancy check) for error detection.

[0198] After pairing is complete, if the display device 1120 queries the on-body electronics 1110 for real-time monitored analyte information and / or logged or stored analyte data, in a particular embodiment, the response data packet sent to the display device 1120 contains a total of 418 bytes, including 34 bytes of status information, time information, and calibration data, 96 bytes of the most recent 16 1-minute glucose data points, and 288 bytes of the most recent 15-minute interval glucose data over a 12-hour period. Depending on the size or capacity of the memory or storage unit of the on-body electronics 1110, the data stored and subsequently provided to the display device 1120 may have different time resolutions and / or span longer or shorter periods of time. For example, with a larger data buffer, the glucose-related data provided to the display device 1120 may include glucose data over 24 hours at 15-minute sampling intervals, 10-minute sampling intervals, 5-minute sampling intervals, or 1-minute sampling intervals. Further, the determined variations in the monitored analyte level indicating the historical trend of the monitored analyte level may be processed and / or determined by the on-body electronics 1110, or alternatively, or in addition, the stored data may be provided to a display device 1120 which can then determine trend information for the monitored analyte level based on the received data packets.

[0199] The size of the data packets provided from the on-body electronics 1110 to the display device 1120 may vary depending on the communication protocol and / or underlying data transmission frequency, i.e., whether 433 MHz, 13.56 MHz, or 2.45 GHz is used, in addition to other parameters such as the presence of a data processing device, such as a processor or processing circuit (e.g., a central processing unit CPU) in the on-body electronics 1110 in addition to an ASIC state machine, the size of data buffers and / or memory.

[0200] In particular embodiments, upon successful activation of on-body electronics 1110 and pairing with display device 1120, a control unit of display device 1120 may be programmed to generate and output one or more visual, audible, and / or tactile notifications for output to a user on display 1122 or on a user interface of display device 1120. In particular embodiments, only one display device may be paired with one on-body electronic device at a time. Alternatively, in particular embodiments, one display device may be configured to pair with multiple on-body electronic devices simultaneously.

[0201] Once paired, the display 1122 of the display device 1120 outputs the remaining operational life of the user's analyte sensor 1101, for example, under the control of a processor of the display device 1120. Additionally, as the end of the sensor's life approaches, the display device may be configured to output a notification to alert the user that the end of the sensor's life is approaching. A schedule for such notifications may be programmed or programmable by the user and executed by the processor of the display device.

[0202] Referring back to FIG. 11 , in certain embodiments, the analyte monitoring system 1100 can store historical analyte data, along with date and / or time stamps and / or concurrent temperature measurements, in a memory, such as a memory configured as a data logger as described above. In certain embodiments, the analyte data is stored at a frequency such as about once per minute, or about once every 10 minutes, or about once per hour. Data logger embodiments can store historical analyte data for a predetermined period, e.g., a period specified by a physician, such as from about one day to about one month or more, e.g., about three days or more, e.g., about five days or more, e.g., about seven days or more, e.g., about two weeks or more, e.g., about one month or more.

[0203] Other durations may be appropriate, depending on the clinical significance of the data being observed. The analyte monitoring system 1100 may display analyte measurements to the subject during the monitoring period. In some embodiments, the data is not displayed to the subject. Optionally, the data logger may transmit historical analyte data to a receiving device located adjacent to, e.g., very close to, the data logger. For example, the receiving device may be configured to communicate with the data logger using a transmission protocol that operates at low power over distances of a fraction of an inch (1 inch ≈ 25.4 mm) to about several feet (1 foot ≈ 304.8 mm). For example, without limitation, such proximity protocols include Certified Wireless USB™, TransferJet™, Bluetooth™ (IEEE 802.15.1), WiFi™ (IEEE 802.11), ZigBee™ (IEEE 802.15.4-2006), Wibree™, etc.

[0204] The analyte data parameters may be calculated by a processor or processing circuit executing a program stored in memory. In certain embodiments, the processor executing the program stored in memory is provided within the data processing module 1160 (FIG. 11). In certain embodiments, the processor executing the program stored in memory is provided within the display device 1120. An exemplary technique for analyzing the data is an applied ambulatory glucose profile (AGP) analysis technique. Further detailed descriptions are provided in U.S. Pat. Nos. 5,262,035, 5,264,104, 5,262,305, 5,320,715, 5,593,852, 6,175,752, 6,650,471, 6,746,582, 6,284,478, 7,299,082, and U.S. patent application Ser. Nos. 10 / 745,878 and 11 / 060,365, the disclosures of all of which are incorporated herein by reference in their entirety for all purposes.

[0205] As described above, in certain aspects of the present disclosure, individual ketone measurement data may be obtained on demand or upon request from a display device, and the ketone measurements are obtained from an in vivo ketone sensor that is transcutaneously placed beneath the user's skin layer and has a portion of the sensor maintained in fluid contact with bodily fluids beneath the skin layer. Thus, in aspects of the present disclosure, a user of an analyte monitoring system can conveniently determine real-time glucose information at any time using RFID communication protocols as described above.

[0206] In one aspect, the integrated assembly including the on-body electronics and insertion device can be sterilized, packaged, and provided to a user as a single device. Furthermore, during manufacturing, the insertion device assembly can be terminally packaged to save costs and avoid the use of expensive thermoformed trays or foil seals, for example. Additionally, the insertion device may include end caps that are rotatably coupled to the insertion device body and provide a safe and sterile environment for the integrated assembly and the sensor provided within the insertion device (and avoid the use of desiccants for the sensor). The end cap-sealed insertion device may also be configured to retain the sensor within the housing from significant movement during shipping, thereby maintaining the sensor position relative to the integrated assembly and insertion device from manufacturing, assembly, and shipping until the device is ready for use by a user.

[0207] Exemplary Embodiments of Ketone Sensors The present disclosure discloses enzyme compositions comprising nicotinamide adenine dinucleotide phosphate (NAD(P)+) or a derivative thereof and an electron transfer agent having a transition metal complex. In some embodiments, the subject enzyme compositions comprise nicotinamide adenine dinucleotide phosphate (NAD(P)+) or a derivative thereof, an NAD(P)+-dependent dehydrogenase, an NAD(P)H oxidoreductase, and an electron transfer agent having a transition metal complex, including an analyte sensor having an enzyme layer comprising immobilized NAD(P)+ or a derivative thereof and an electron transfer agent comprising a transition metal complex. Embodiments of the present disclosure relate to enzyme compositions for analyte sensing, including where the subject compositions provide in vivo monitoring of an analyte over an extended period of time. When the subject enzyme compositions comprise an NAD(P)+-dependent dehydrogenase, the analyte sensors described herein provide clinically accurate electrochemical measurements of analytes catalyzed by the NAD(P)+-dependent dehydrogenase. As described in more detail below, the subject enzyme compositions provide clinically accurate electrochemical measurements of analytes measured by Clark Error Grid analysis and / or MARD analysis and / or MAD analysis. In particular, the subject enzyme compositions provide measurements by analyte sensors incorporating the subject compositions that generate a signal that increases linearly as a function of analyte concentration. Additionally, the subject enzyme compositions provide clinically accurate electrochemical measurements of analytes catalyzed by NAD(P)+-dependent dehydrogenases within 30 seconds of contacting the sensor with a fluid sample (e.g., interstitial fluid when the sensor is placed beneath the surface of the subject's skin). In certain instances, the subject enzyme compositions provide clinically accurate electrochemical measurements of analytes catalyzed by NAD(P)+-dependent dehydrogenases immediately after contacting the fluid sample with the sensor.

[0208] The subject enzyme compositions include an NAD(P)+-dependent dehydrogenase, such as glucose dehydrogenase, alcohol dehydrogenase, or D-3-hydroxybutyrate dehydrogenase. In some embodiments, the subject NAD(P)+-dependent dehydrogenase is an oxidoreductase belonging to the enzyme class 1.1.1-.

[0209] The NAD(P)+-dependent dehydrogenase may be present in the subject compositions in various amounts, including 0.05 μg to 5 μg, 0.1 μg to 4 μg, 0.2 μg to 3 μg, and 0.5 μg to 2 μg, etc. Accordingly, the amount of NAD(P)+-dependent dehydrogenase is 0.01% to 10% by weight of the total enzyme composition, including 0.05% to 9.5% by weight, such as 0.1% to 9% by weight, such as 0.5% to 8.5% by weight, such as 1% to 8% by weight, and including 2% to 7% by weight of the total enzyme composition.

[0210] The enzyme composition also includes nicotinamide adenine dinucleotide phosphate (NAD(P)+) or a derivative thereof. In some embodiments, the enzyme composition of interest includes nicotinamide adenine dinucleotide phosphate (NAD(P)+). In other embodiments, the enzyme composition includes a derivative of nicotinamide adenine dinucleotide phosphate (NAD(P)+). The derivative of nicotinamide adenine dinucleotide phosphate (NAD(P)+) is a compound of formula I:

[0211] [ka]

[0212] wherein X is alkyl, substituted alkyl, aryl, substituted aryl, acyl, and aminoacyl. In some embodiments, X is aminoacyl-substituted alkyl. In some embodiments, X is CHC(O)NH(CH) y NH2, and y is an integer from 1 to 10, e.g., from 2 to 9, e.g., from 3 to 8, including when y is 6. In particular examples, X is CH2C(O)NH(CH2)6NH2. In these embodiments, the nicotinamide adenine dinucleotide phosphate (NAD(P)) in the subject enzyme composition is + ) derivatives are:

[0213] [ka]

[0214] is. Embodiments of the enzyme composition also include an NAD(P)H oxidoreductase. In certain embodiments, the enzyme composition includes diaphorase. The amount of NAD(P)H oxidoreductase (e.g., diaphorase) present in the subject compositions ranges from 0.01 μg to 10 μg, including ranges from 0.02 μg to 9 μg, such as 0.03 μg to 8 μg, such as 0.04 μg to 7 μg, such as 0.05 μg to 5 μg, such as 0.1 μg to 4 μg, such as 0.2 μg to 3 μg, and 0.5 μg to 2 μg. Thus, the amount of NAD(P)H oxidoreductase (e.g., diaphorase) is from 0.01% to 10% by weight of the total enzyme composition, including, for example, from 0.05% to 9.5% by weight, such as from 0.1% to 9% by weight, such as from 0.5% to 8.5% by weight, such as from 1% to 8% by weight, and including, for example, from 2% to 7% by weight of the total enzyme composition.

[0215] In some embodiments, the weight ratio of NAD(P)+-dependent dehydrogenase to NAD(P)H oxidoreductase (e.g., diaphorase) is in the range of 1 to 10 NAD(P)+-dependent dehydrogenase to NAD(P)H oxidoreductase, such as 1 to 8, such as 1 to 5, such as 1 to 2, and including 1 to 1 NAD(P)+-dependent dehydrogenase to NAD(P)H oxidoreductase. In other embodiments, the weight ratio of NAD(P)+-dependent dehydrogenase to NAD(P)H oxidoreductase is in the range of 10 to 1 NAD(P)+-dependent dehydrogenase to NAD(P)H oxidoreductase, such as 8 to 1, such as 5 to 1, and including 2 to 1 NAD(P)+-dependent dehydrogenase to NAD(P)H oxidoreductase.

[0216] The enzyme compositions of interest also include electron transfer agents having transition metal complexes. These may be electroreducible and electrooxidizable ions or molecules with redox potentials several hundred millivolts higher or lower than the redox potential of a standard calomel electrode (SCE). Examples of transition metal complexes include metallocenes, including ferrocene, hexacyanoferrate(III), ruthenium hexamine, and the like. Further examples include those described in U.S. Patent Nos. 6,736,957, 7,501,053, and 7,754,093, the disclosures of each of which are incorporated herein by reference in their entirety.

[0217] In some embodiments, the electron transport agent is an osmium transition metal complex having one or more ligands, each of which has a nitrogen-containing heterocycle such as 2,2'-bipyridine, 1,10-phenanthroline, 1-methyl,2-pyridylbiimidazole, or a derivative thereof. The electron transport agent may have one or more ligands covalently attached to a polymer, each of which has at least one nitrogen-containing heterocycle, such as pyridine, imidazole, or a derivative thereof. One example of an electron transport agent includes (a) a polymer or copolymer having pyridine or imidazole functional groups and (b) an osmium cation complexed with two ligands, each of which comprises 2,2'-bipyridine, 1,10-phenanthroline, or a derivative thereof, where the two ligands are not necessarily the same. Some derivatives of 2,2'-bipyridine for complexing with osmium cations include, but are not limited to, mono-, di-, and polyalkoxy-2,2'-bipyridines, including 4,4'-dimethyl-2,2'-bipyridine and 4,4'-dimethoxy-2,2'-bipyridine. Derivatives of 1,10-phenanthroline for complexing with osmium cations include, but are not limited to, mono-, di-, and polyalkoxy-1,10-phenanthrolines, such as 4,7-dimethyl-1,10-phenanthroline and 4,7-dimethoxy-1,10-phenanthroline. Polymers for complexing with osmium cations include, but are not limited to, polymers and copolymers of poly(1-vinylimidazole) (referred to as "PVI") and poly(4-vinylpyridine) (referred to as "PVP"). Suitable copolymer substituents of poly(1-vinylimidazole) include acrylonitrile, acrylamide, and substituted or quaternized N-vinylimidazole, e.g., electron transport agents having osmium complexed to a polymer or copolymer of poly(1-vinylimidazole).

[0218] The subject enzyme composition may be heterogeneous or homogeneous. In some embodiments, each component (i.e., nicotinamide adenine dinucleotide phosphate (NAD(P)+) or a derivative thereof, NAD(P)+-dependent dehydrogenase, NAD(P)H oxidoreductase, and an electron transfer agent having a transition metal complex) is uniformly distributed throughout the composition when applied to, for example, an electrode, as described in more detail below. For example, each of nicotinamide adenine dinucleotide phosphate (NAD(P)+) or a derivative thereof, NAD(P)+-dependent dehydrogenase, NAD(P)H oxidoreductase, and an electron transfer agent having a transition metal complex may be uniformly distributed throughout the composition so that the concentration of each component is the same throughout.

[0219] In certain embodiments, the subject enzyme compositions described herein are polymers. Polymers that can be used may be branched or unbranched, and may be homopolymers formed from the polymerization of a single type of monomer, or heteropolymers containing two or more different types of monomers. Heteropolymers may be copolymers having alternating monomer subunits, or in some cases, block copolymers (e.g., diblock or triblock copolymers) containing two or more homopolymer subunits covalently linked. In some embodiments, the subject enzyme compositions comprise heterocycle-containing polymers. The term heterocycle (also referred to as "heterocyclyl") is used herein in its conventional sense to refer to any cyclic moiety containing one or more heteroatoms (i.e., atoms other than carbon), which may include, but are not limited to, N, P, O, S, Si, etc. Heterocycle-containing polymers may be heteroalkyl, heteroalkanyl, heteroalkenyl, and heteroalkynyl, as well as heteroaryl or heteroarylalkyl.

[0220] "Heteroalkyl, heteroalkanyl, heteroalkenyl, and heteroalkynyl," by themselves or as part of another substituent, refer to alkyl, alkanyl, alkenyl, and alkynyl groups, respectively, in which one or more of the carbon atoms (and any associated hydrogen atoms) are independently replaced with the same or different heteroatom groups. Representative heteroatom groups that may be included in these groups include, but are not limited to, -O-, -S-, -SS-, -OS-, -NR37R38-, .=NN=, -N=N-, -N=N-NR39R40, -PR41-, -P(O)2-, -POR42-, -OP(O)2-, -SO-, -S-(O)-, -SO2-, -SnR43R44-, where R37, R38, R39, R40, R41, R42, R43, and R44 are independently hydrogen, alkyl, substituted alkyl, aryl, substituted aryl, arylalkyl, substituted arylalkyl, cycloalkyl, substituted cycloalkyl, cycloheteroalkyl, substituted cycloheteroalkyl, heteroalkyl, substituted heteroalkyl, heteroaryl, substituted heteroaryl, heteroarylalkyl, or substituted heteroarylalkyl.

[0221] "Heteroaryl" by itself or as part of another substituent refers to a monovalent heteroaromatic radical derived by removing one hydrogen atom from a single atom of a heteroaromatic ring system. Typical heteroaryl groups include, but are not limited to, groups derived from acridine, arsindole, carbazole, β-carboline, chromane, chromene, cinnoline, furan, imidazole, indazole, indole, indoline, indolizine, isobenzofuran, isochromene, isoindole, isoindoline, isoquinoline, isothiazole, isoxazole, naphthyridine, oxadiazole, oxazole, perimidine, phenanthridine, phenanthroline, phenazine, phthalazine, pteridine, purine, pyran, pyrazine, pyrazole, pyridazine, pyridine, pyrimidine, pyrrole, pyrrolidine, quinazoline, quinoline, quinolizine, quinoxaline, tetrazole, thiadiazole, thiazole, thiophene, triazole, xanthene, benzodioxole, and the like. In certain embodiments, the heteroaryl group is a 5- to 20-membered heteroaryl. In certain embodiments, the heteroaryl group is a 5- to 10-membered heteroaryl. In certain embodiments, the heteroaryl group is derived from thiophene, pyrrole, benzothiophene, benzofuran, indole, pyridine, quinoline, imidazole, oxazole, and pyrazine.

[0222] "Heteroarylalkyl," by itself or as part of another substituent, refers to an acyclic alkyl radical in which one of the hydrogen atoms bonded to a carbon atom, typically a terminal or sp3 carbon atom, is replaced with a heteroaryl group. When specific alkyl moieties are intended, the nomenclature heteroarylalkanyl, heteroarylalkenyl, and / or heteroarylalkynyl is used. In certain embodiments, a heteroarylalkyl group is a 6- to 30-membered heteroarylalkyl, e.g., the alkanyl, alkenyl, or alkynyl portion of the heteroarylalkyl is 1- to 10-membered, and the heteroaryl portion is a 5- to 20-membered heteroaryl. In certain embodiments, a heteroarylalkyl group is a 6- to 20-membered heteroarylalkyl, e.g., the alkanyl, alkenyl, or alkynyl portion of the heteroarylalkyl is 1- to 8-membered, and the heteroaryl portion is a 5- to 12-membered heteroaryl.

[0223] In some embodiments, the heterocyclic component is an aromatic ring system. "Aromatic ring system" refers to an unsaturated cyclic or polycyclic ring system that has a conjugated π-electron system, either by itself or as part of another substituent. Specifically included in the definition of "aromatic ring system" are fused ring systems in which one or more of the rings are aromatic and one or more of the rings are saturated or unsaturated, such as fluorene, indane, indene, phenalene, etc. Exemplary aromatic ring systems include, but are not limited to, aceanthrylene, acenaphthylene, acephenanthrylene, anthracene, azulene, benzene, chrysene, coronene, fluoranthene, fluorene, hexacene, hexaphene, hexalene, as-indacene, s-indacene, indane, indene, naphthalene, octacene, octaphene, octalene, ovalene, penta-2,4-diene, pentacene, pentalene, pentaphene, perylene, phenalene, phenanthrene, picene, pleiadene, pyrene, pyranthrene, rubicene, triphenylene, and trinaphthalene.

[0224] A "heteroaromatic ring system," by itself or as part of another substituent, refers to an aromatic ring system in which one or more carbon atoms (and any associated hydrogen atoms) are independently replaced with the same or different heteroatoms. Typical heteroatoms replacing carbon atoms include, but are not limited to, N, P, O, S, Si, and the like. Specifically included within the definition of "heteroaromatic ring system" are fused ring systems in which one or more of the rings is aromatic and one or more of the rings is saturated or unsaturated, e.g., arsindole, benzodioxane, benzofuran, chromane, chromene, indole, indoline, xanthene, and the like. Typical heteroaromatic ring systems include, but are not limited to, arsindole, carbazole, β-carboline, chroman, chromene, cinnoline, furan, imidazole, indazole, indole, indoline, indolizine, isobenzofuran, isochromene, isoindole, isoindoline, isoquinoline, isothiazole, isoxazole, naphthyridine, oxadiazole, oxazole, perimidine, phenanthridine, phenanthroline, phenazine, phthalazine, pteridine, purine, pyran, pyrazine, pyrazole, pyridazine, pyridine, pyrimidine, pyrrole, pyrrolidine, quinazoline, quinoline, quinolizine, quinoxaline, tetrazole, thiadiazole, thiazole, thiophene, triazole, xanthene, and the like.

[0225] In certain embodiments, the enzyme compositions of interest include heterocyclic nitrogen-containing components such as polymers of polyvinylpyridine (PVP) and polyvinylimidazole. The polymer-enzyme composition may also include one or more cross-linking agents such that the polymer backbone enzyme composition is cross-linked. As described herein, reference to linking two or more different polymers together is intermolecular cross-linking, while linking two or more portions of the same polymer is intramolecular cross-linking. In embodiments of the present disclosure, the cross-linking agent is capable of both intermolecular and intramolecular cross-linking simultaneously.

[0226] Suitable crosslinkers may be bifunctional, trifunctional, or tetrafunctional, each having a linear or branched structure. Crosslinkers having a branched structure include multi-arm branched components, such as 3-arm branched components, 4-arm branched components, 5-arm branched components, 6-arm branched components, or more arm branched components, such as those having 7 or more arms, for example, 8 or more arms, for example, 9 or more arms, for example, 10 or more arms, and 15 or more arms. In certain examples, the multi-arm branched component is a multi-arm epoxide, such as a 3-arm epoxide or a 4-arm epoxide. When the multi-arm branched component is a multi-arm epoxide, the multi-arm branched component may be a polyethylene glycol (PEG) multi-arm epoxide or a non-polyethylene glycol (non-PEG) multi-arm epoxide. In some embodiments, the multi-arm branched component is a non-PEG multi-arm epoxide. In other embodiments, the multi-arm branched component is a PEG multi-arm epoxide. In certain embodiments, the multi-arm branched component is a 3-arm PEG epoxide or a 4-arm PEG epoxide.

[0227] Examples of crosslinkers include polyethylene glycol diglycidyl ether, N,N-diglycidyl-4-glycidyloxyaniline, and crosslinkers having the following structure:

[0228] [ka]

[0229] Examples of crosslinking agents include, but are not limited to, nitrogen-containing polyfunctional crosslinkers having the formula: In some examples, one or more bonds with one or more components of the enzyme composition may be formed, such as between one or more of nicotinamide adenine dinucleotide phosphate (NAD(P)+) or a derivative thereof, NAD(P)+-dependent dehydrogenase, NAD(P)H oxidoreductase, and an electron transfer agent. Bond refers to any type of interaction between atoms or molecules that allows chemical compounds to form associations with each other, such as, but not limited to, covalent bonds, ionic bonds, dipole-dipole interactions, hydrogen bonds, London dispersion forces, etc. For example, in situ polymerization of the enzyme composition may form crosslinks between the polymer of the composition and the NAD(P)+-dependent dehydrogenase, nicotinamide adenine dinucleotide phosphate (NAD(P)+) or a derivative thereof, NAD(P)H oxidoreductase, and an electron transfer agent. In certain embodiments, crosslinking of the polymer to one or more of the NAD(P)+-dependent dehydrogenase, nicotinamide adenine dinucleotide phosphate (NAD(P)+) or a derivative thereof, NAD(P)H oxidoreductase, and electron transport agent facilitates reducing the occurrence of detachment of the enzyme composition from the electrode.

[0230] As described herein, the subject enzymes may be used in analyte sensors to monitor the concentration of NAD(P)+-dependent dehydrogenase analytes, such as glucose, alcohol, ketone, lactate, or β-hydroxybutyrate, and the sensors may have one or more electrodes comprising an enzyme composition. In embodiments, the analyte sensor includes a working electrode comprising a conductive material, and the subject enzyme composition is proximate to (e.g., disposed on) and in contact with the conductive material. One or more other electrodes may also be included, such as one or more counter electrodes, one or more reference electrodes, and / or one or more counter / reference electrodes.

[0231] The specific configuration of the electrochemical sensor may depend on the intended application of the analyte sensor and the conditions under which the analyte sensor will operate. In certain embodiments of the present disclosure, the analyte sensor is an analyte sensor deployed entirely within a living body or a transcutaneously deployed analyte sensor configured for deployment within a subject's living body. In one example, at least a portion of the sensor can be deployed within subcutaneous tissue to test for lactate concentrations in interstitial fluid. In another example, at least a portion of the sensor may be deployed within cutaneous tissue to test for analyte concentrations in cutaneous fluid.

[0232] In embodiments, one or more of the subject enzyme compositions are disposed adjacent to (e.g., disposed on) the surface of the working electrode. In some examples, multiple enzyme compositions are disposed adjacent to (e.g., in the form of spots on) the surface of the working electrode. In some cases, a discontinuous or continuous perimeter is formed around each of the multiple enzyme compositions disposed adjacent to the surface of the working electrode. Examples of depositing multiple reagent compositions on the surface of an electrode and forming a discontinuous or continuous perimeter around each reagent composition are described in U.S. Patent Application Publication No. 2012 / 0150005 and co-pending U.S. Patent Application No. 62 / 067,813, the disclosures of which are incorporated herein by reference.

[0233] The subject enzyme composition having nicotinamide adenine dinucleotide phosphate (NAD(P)+) or a derivative thereof, an NAD(P)+-dependent dehydrogenase, an NAD(P)H oxidoreductase, and an electron transfer agent can be deposited on the surface of the working electrode as one large application covering the desired portion of the working electrode, or in the form of an array of multiple enzyme compositions, e.g., spaced apart from one another. Depending on the application, any or all of the enzyme compositions in the array can be the same or different from one another. For example, an array can be formed over a 100 mm 2 For example, 75 mm 2 or less, or 50 mm 2 For example, 25 mm 2 or less, or 10 mm 2 or less, or 5 mm 2For example, 2 mm 2 Less than or equal to 1 mm 2 Below, 0.5mm 2 or less than 0.1 mm 2 In an area of ​​less than 1000, it may contain two or more, five or more enzyme composition array features containing 10 or more, 25 or more, 50 or more, 100 or more, or even 1000 or more nicotinamide adenine dinucleotide phosphate (NAD(P)+) or derivatives thereof, NAD(P)+-dependent dehydrogenases, NAD(P)H oxidoreductases, and electron transport agents.

[0234] The shape of the deposited enzyme composition may vary within or between sensors. For example, in certain embodiments, the deposited film is circular. In other embodiments, the shape may be triangular, square, rectangular, circular, oval, or other regular or irregular polygonal shapes (e.g., when viewed from above), as well as other two-dimensional shapes such as circular, semicircular, or crescent. All or part of the electrode may be covered by the enzyme composition, for example, 5% or more, for example, 25% or more, for example, 50% or more, for example, 75% or more, and 90% or more. In certain examples, the entire electrode surface is covered by the enzyme composition (i.e., 100%).

[0235] Fabricating electrodes and / or sensors according to embodiments of the present disclosure produces reproducible enzyme compositions deposited on the surface of the electrode. For example, the enzyme compositions provided herein may deviate from each other by 5% or less, for example, 4% or less, for example, 3% or less, for example, 2% or less, for example, 1% or less, and 0.5% or less. In some embodiments, the sensing composition comprises nicotinamide adenine dinucleotide phosphate (NAD(P)+) or a derivative thereof and an electron transfer agent. In certain embodiments, the deposited enzyme compositions containing nicotinamide adenine dinucleotide phosphate (NAD(P)+) or a derivative thereof, NAD(P)+-dependent dehydrogenase, NAD(P)H oxidoreductase, and an electron transfer agent are identical without deviation from each other.

[0236] In certain embodiments, the method further comprises drying the enzyme composition deposited on the electrode, which may be carried out at room temperature or, if desired, at an elevated temperature, for example, in the range including 25°C to 100°C, for example, 30°C to 80°C, for example, 40°C to 60°C.

[0237] Examples of subject analyte sensor configurations and methods of manufacturing them are disclosed in U.S. Patent Nos. 6,175,752, 6,134,461, 6,579,690, 6,605,200, 6,605,201, 6,654,625, 6,746,582, 6,932,894, 7,090,756, 5,356,786, 6,560,471, 5,262,035, 6,881, No. 551, No. 6,121,009, No. 6,071,391, No. 6,377,894, No. 6,600,997, No. 6,514,460, No. 5,820,551, No. 6,736,957, No. 6 , 503,381, 6,676,816, 6,514,718, 5,593,852, 6,284,478, 7,299,082, 7,811,231, 7,822,557 Nos. 8,106,780, and 8,435,682, U.S. Patent Application Publication Nos. 2010 / 0198034, 2010 / 0324392, 2010 / 0326842, 2007 / 0095661, 2010 / 0213057, 2011 / 0120865, 2011 / 0124994, 2011 / 0124993, 2010 / 0213057, 2011 / 02132 25, 2011 / 0126188, 2011 / 0256024, 2011 / 0257495, 2012 / 0157801, 2012 / 0245447, 2012 / 0157801, 2012 / 0323098, and 2013 / 0116524, the disclosures of each of which are incorporated herein by reference in their entirety.

[0238] In some embodiments, the in-vivo sensor may include an insertion tip positionable below the surface of the skin, e.g., to penetrate the skin and enter the subcutaneous space, e.g., to contact a user's biological fluids, such as interstitial fluid. Working, reference, and counter electrode contact portions are disposed on a first portion of the sensor located above the skin surface. The working, reference, and counter electrodes are disposed on the inserted portion of the sensor. Traces may be provided from the electrodes at the tip to contacts configured for connection with the sensor electronics.

[0239] In certain embodiments, the working electrode and counter electrode and the dielectric material of the sensor are layered. For example, the sensor may include a non-conductive material layer and a first conductive layer, such as a conductive polymer, carbon, platinum-carbon, or gold, disposed on at least a portion of the non-conductive material layer (as described above). The enzyme composition may be disposed on one or more surfaces of the working electrode or may otherwise be in direct or indirect contact with the working electrode. A first insulating layer, such as a first dielectric layer, may be disposed or laminated on at least a portion of the first conductive layer, and a second conductive layer may be disposed or laminated on top of at least a portion of the first insulating layer (or dielectric layer). The second conductive layer may be a reference electrode. A second insulating layer, such as a second dielectric layer, may be disposed or laminated on at least a portion of the second conductive layer. Additionally, a third conductive layer may be disposed on at least a portion of the second insulating layer and may be a counter electrode. Finally, a third insulating layer may be disposed or laminated on at least a portion of the third conductive layer. In this manner, the sensors may be stacked such that at least a portion of each of the conductive layers is separated by a respective insulating layer (eg, a dielectric layer).

[0240] In other embodiments, some or all of the electrodes may be coplanar, such that two or more electrodes may be disposed on the same plane on the material (e.g., side-by-side (e.g., parallel), or at an angle relative to one another). For example, coplanar electrodes may include appropriate spacing between them and / or may include dielectric or insulating material disposed between the conductive layers / electrodes. Furthermore, in certain embodiments, one or more of the electrodes may be disposed on opposite sides of the non-conductive material. In such embodiments, the electrical contacts may be on the same or different sides of the non-conductive material. For example, the electrodes may be on a first side and their respective contacts may be on a second side, e.g., traces connecting the electrodes and contacts may traverse the material. Vias provide pathways through which electrical traces are routed to opposite sides of the sensor.

[0241] The subject analyte sensors may be configured to monitor levels of an analyte (e.g., glucose, alcohol, ketones, lactate, beta-hydroxybutyrate) over periods that may range from seconds, minutes, hours, days, weeks to months, or longer.

[0242] In certain embodiments, the analyte sensor includes a mass transport limiting layer (or membrane layer), e.g., an analyte flux regulating layer, that acts as a diffusion-limiting barrier to reduce the rate of mass transport of an analyte, e.g., glucose, alcohol, ketone, lactate, β-hydroxybutyrate, when the sensor is in use. The mass transport limiting layer limits the flow of analyte to the electrodes in the electrochemical sensor so that the sensor responds linearly over a wide range of analyte concentrations. The mass transport limiting layer may comprise a polymer and may be biocompatible. The mass transport limiting layer may provide multiple functions, such as biocompatibility and / or interferent rejection, or functions may be provided by various membrane layers.

[0243] In certain embodiments, the mass transport limiting layer is a membrane composed of a crosslinked polymer containing heterocyclic nitrogen groups, such as polymers of polyvinylpyridine and polyvinylimidazole. Embodiments include membranes made of polyurethane, or polyetherurethane, or chemically related materials, or membranes made of silicone, etc.

[0244] Membranes can be formed by in situ crosslinking in an alcoholic buffer solution of polymers modified with zwitterionic moieties, non-pyridine copolymer components, and, optionally, other moieties that are either hydrophilic or hydrophobic and / or have other desirable properties. The modified polymer can be made from a precursor polymer containing heterocyclic nitrogen groups. For example, the precursor polymer can be polyvinylpyridine or polyvinylimidazole. Optionally, hydrophilic or hydrophobic modifiers can be used to "fine-tune" the permeability of the resulting membrane to analytes of interest. Optional hydrophilic modifiers, such as poly(ethylene glycol), hydroxyl, or polyhydroxyl modifiers, can be used to enhance the biocompatibility of the polymer or the resulting membrane.

[0245] Suitable mass transport limiting membranes for the subject analyte sensors include, but are not limited to, those described in U.S. Patent No. 6,932,894, the disclosure of which is incorporated herein by reference. In certain embodiments, the mass transport limiting membrane is a temperature-independent SMART membrane. Suitable temperature-independent membranes include, but are not limited to, those described in U.S. Patent Application Publication No. 2012 / 0296186 and co-pending U.S. Patent Application No. 14 / 737,082, the disclosures of which are incorporated herein by reference.

[0246] Analyte sensors according to certain embodiments may be configured to operate at low oxygen concentrations, meaning oxygen concentrations of 1.5 mg / L or less, including, for example, 1.0 mg / L or less, for example, 0.75 mg / L or less, for example, 0.6 mg / L or less, for example, 0.3 mg / L or less, for example, 0.25 mg / L or less, for example, 0.15 mg / L or less, for example, 0.1 mg / L or less, and 0.05 mg / L or less.

[0247] Embodiments of the present disclosure also include methods for in vivo monitoring of analyte levels over time using an analyte sensor incorporating an enzyme composition containing nicotinamide adenine dinucleotide phosphate (NAD(P)+) or a derivative thereof, an NAD(P)+-dependent dehydrogenase, an NAD(P)H oxidoreductase, and an electron transport agent. Generally, in vivo monitoring of the concentration of an analyte in a subject's bodily fluid involves inserting an in vivo analyte sensor as disclosed herein at least partially beneath the skin surface, contacting the fluid to be monitored (e.g., interstitium, blood, dermis, etc.) with the inserted sensor, and generating a sensor signal at the working electrode. The presence and / or concentration of the analyte detected by the analyte sensor can be displayed, stored, transferred, and / or otherwise processed. Various techniques can be used to determine the concentration of an analyte (e.g., glucose, alcohol, ketone, lactate, β-hydroxybutyrate) using the subject sensors. In certain embodiments, electrochemical analyte concentration monitoring techniques are used. For example, monitoring the concentration of the analyte using the sensor signal may be done by coulometry, amperometry, voltammetry, potentiometry, or any other convenient electrochemical detection technique.

[0248] These methods may be used in conjunction with devices used to detect and / or measure another analyte, including, for example, glucose, oxygen, carbon dioxide, electrolytes, or other moieties of interest, or any combination thereof, found subcutaneously in bodily fluids, including, for example, interstitial fluid, dermal fluid, blood, or other bodily fluids of interest, or any combination thereof.

[0249] In certain embodiments, the method further includes attaching an electronics unit to the patient's skin, coupling conductive contacts of the electronics unit to contacts of the sensor, collecting data regarding the analyte level from a signal generated by the sensor using the electronics unit, and transferring the collected data from the electronics unit to a receiver unit, e.g., by RF. The receiver unit may be a mobile phone. The mobile phone may include an application related to the analyte being monitored. In certain embodiments, the analyte information is transferred via RFID protocol, Bluetooth, or the like.

[0250] The analyte sensor may be positionable within a user for automatic analyte sensing, either continuously or periodically. Embodiments may include monitoring analyte levels over periods that may range from seconds, minutes, hours, days, weeks, months, or longer. Future analyte levels may be predicted based on obtained information, e.g., current lactate levels at time 0, as well as analyte change rates.

[0251] The sensor electronics unit may automatically transfer data from the sensor / electronics unit to one or more receiver units. Sensor data may be communicated automatically and periodically, such as at a specific frequency as data is acquired or after a specific period of time has passed since the sensor data was stored in memory. For example, sensor electronics coupled to a sensor placed within a living body may collect sensor data over a predetermined period of time and periodically (e.g., every 1 minute, every 5 minutes, or another predetermined period) transmit the collected data to a monitoring device placed within range of the sensor electronics.

[0252] In other embodiments, the sensor electronics coupled to the sensor placed in vivo can communicate with the receiving device in a non-automatic manner, without being set on a specific schedule. For example, sensor data may be communicated from the sensor electronics to the receiving device using RFID technology and may be communicated whenever the sensor electronics is brought within communication range of the analyte monitoring device. For example, the sensor placed in vivo may collect sensor data in memory until the monitoring device (e.g., receiver unit) is brought within communication range of the sensor electronics unit, e.g., by the patient or user. Once the sensor placed in vivo is detected by the monitoring device, the device establishes communication with the analyte sensor electronics and, e.g., uploads sensor data collected since the last transfer of sensor data. In this way, the patient does not need to maintain constant proximity to the receiving device, but instead can upload sensor data when desired by bringing the receiving device within range of the analyte sensor. In still other embodiments, a combination of automatic and non-automatic transfer of sensor data may be implemented in certain embodiments. For example, transfer of sensor data may begin when brought within communication range and then continue automatically as the patient remains within communication range.

[0253] Exemplary Embodiments of Calibration Biochemical sensors can be described by one or more sensing properties. A common sensing property is called the sensitivity of a biochemical sensor, which is a measure of the sensor's responsiveness to the concentration of the chemical or composition it is designed to detect. For electrochemical sensors, this response can be in the form of current (amperometric) or charge (coulometric). For other types of sensors, the response can be in a different form, such as photon intensity (e.g., optical light). The sensitivity of a biochemical analyte sensor can vary depending on several factors, including whether the sensor is in vitro or in vivo.

[0254] Figure 15 is a graph showing the in vitro sensitivity of an amperometric 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 sensitivity of the analyte sensor is linear or substantially linear and can be modeled according to the equation y = mx + b, where y is the electrical output current of the sensor, x is the analyte level (or concentration), m is the sensitivity slope, and b is the sensitivity intercept, with the intercept generally corresponding 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 sensitivity slope and intercept. Sensors with nonlinear sensitivity require additional information to determine the analyte level from the sensor's output current, and those skilled in the art are familiar with methods for modeling nonlinear sensitivity. In certain embodiments of an in vivo sensor, the in vitro sensitivity may be the same as the in vivo sensitivity, while in other embodiments, a transfer (or transformation) function is used to convert the in vitro sensitivity to an in vivo sensitivity applicable to the sensor's intended in vivo use.

[0255] Examples of sensing characteristics derived from testing As described, one or more medical devices in a baseline subset can be tested to empirically determine a sensing characteristic for the baseline subset. The testing, in many embodiments, can generate data that verifiably represents the ability of the medical device to sense a biochemical attribute. In many in vivo and in vitro analyte sensor (e.g., test strip) embodiments, the sensing characteristic can be the sensitivity of the analyte sensor to the presence of the analyte. Often, the testing is performed in vitro, and in vitro test data is collected. The sensing characteristic derived or otherwise obtained from the in vitro test data for the baseline subset can be referred to as an in vitro sensing characteristic (e.g., in vitro sensitivity).

[0256] The following examples are put forth to provide those of ordinary skill in the art with a complete disclosure and description of how to make and use embodiments of the present invention, and are not intended to limit the scope of what the inventors regard as their invention, nor are they intended to represent that the following experiments are all or the only experiments performed. Efforts have been made to ensure accuracy with respect to numbers used (e.g., amounts, temperature, etc.), but some experimental error and deviation should be accounted for. Unless otherwise indicated, parts are parts by weight, molecular weight is weight average molecular weight, temperature is in degrees Celsius, and pressure is at or near atmospheric.

[0257] Example 1 Nicotinamide adenine dinucleotide phosphate (NAD(P) + ) or its derivatives, NAD(P) + Experiments were conducted to demonstrate the performance of an analyte sensor having a working electrode containing a nicotinamide adenine dinucleotide phosphate, D-3-hydroxybutyrate dehydrogenase, diaphorase, and an electron transfer agent. The sensor was prepared by depositing on the surface of the electrode an enzyme composition containing nicotinamide adenine dinucleotide phosphate, D-3-hydroxybutyrate dehydrogenase, diaphorase, and a polymer-bound osmium-transition metal catalyst, and a bifunctional crosslinker, as shown by the scheme (also referred to in further examples as a polymeric redox mediator):

[0258] [ka]

[0259] The sensors were tested in phosphate buffer solutions containing various concentrations of D-3-hydroxybutyrate. Table 1 summarizes the beaker calibration and linearity of the data signals from the prepared sensors.

[0260] [Table 1]

[0261] Figure 16 shows the signal output over 2.3 hours at various concentrations of D-3-hydroxybutyrate (80 μM, 160 μM, and 240 μM). Figure 17 shows the linearity of the sensor signal as a function of D-3-hydroxybutyrate concentration. As shown in Figures 1 and 2, the sensor provides a linear and sustained response to D-3-hydroxybutyrate.

[0262] Additional enzymes for detecting ketones are described in PCT Application PCT / US21 / 62968, U.S. Patent No. 11,091,788, and U.S. Patent Application No. 2020 / 0237275, the disclosures of which are incorporated by reference in their entireties.

[0263] Example 2 Experiments were conducted to demonstrate the performance of an analyte sensor with a working electrode containing free NAD. The sensor was prepared by depositing an enzyme composition containing free NAD onto the surface of the electrode. The sensing layer formulation is listed in Table 2. The sensing layer solution was deposited onto a carbon electrode and cured overnight at 25C / 60H before the addition of a membrane. The membrane formulation is listed in Table 3. The sensor was immersed in the above solution at 3 x 5mm / s, and the sensor was cured overnight at 25C / 60H and at 56C for 2 days.

[0264] [Table 2]

[0265] [Table 3]

[0266] Figure 18 shows the signal output over 3.6 hours at various concentrations of D-3-hydroxybutyrate (ketone). Figure 19 shows the linearity of the sensor signal as a function of D-3-hydroxybutyrate concentration. Figure 20 shows the sensor calibration at 10 mM. As shown in Figures 17-19, the sensor gives a linear and sustained response to D-3-hydroxybutyrate (ketone). Table 4 also shows the free NAD ketone sensor beaker calibration and stability summary.

[0267] [Table 4]

[0268] Example 3 Experiments were also conducted to demonstrate the performance of a ketone sensor with a working electrode containing free versus immobilized NAD. Sensors were prepared by depositing an enzyme composition containing free NAD (A) or immobilized NAD (B) onto the electrode surface. The sensing layer formulation is listed in Table 5. The sensing layer solution was deposited onto a carbon electrode and cured overnight at 25°C / 60°C before the addition of a membrane. The membrane formulation is listed in Table 6. The sensor was immersed in the above solution at 3 × 5 mm / s (Table 7), and the sensor was cured overnight at 25°C / 60°C and for 2 days at 56°C. Figure 21 shows that both the free and immobilized NAD versions of the ketone sensor exhibit similar stability and signal.

[0269] [Table 5]

[0270] [Table 6]

[0271] [Table 7]

[0272] Example 4 In vitro and in vivo experiments were conducted using a three-electrode sensor (i.e., working electrode, reference electrode, and counter electrode) to demonstrate the performance of a continuous ketone monitor calibrated using in vitro sensitivity. The sensor contains the chemistry described in Example 1 above. The sensor was fabricated using a method that controlled the area of ​​the sensing layer on the working electrode as well as the thickness of the membrane layer. All sensors used in this experiment were manufactured from the same lot.

[0273] In vitro testing was performed to determine the in vitro sensitivity of a baseline subset of sensors from a manufacturing lot (in this case, 16 sensors), for example, as shown and described in connection with FIG. 19 and Table 4 above. The baseline subset may include quantities other than 16 without departing from the scope of the present subject matter. In vitro testing sensitivity was obtained by applying various ketone solutions to each analyte sensor and monitoring the resulting current, which may be on the order of nanoamps, picoamps, or other currents depending on the sensor design. The in vitro test involves placing and immersing a baseline subset of 16 sensors in a solution of 100 mM phosphate buffer at a controlled temperature of 37°C, sequentially forming a plurality of known ketone concentrations by injecting aliquots of 1 M ketone into the solution to achieve various ketone concentrations (e.g., without limitation, 1, 2, 3, 4, 6, and 8 mmol / L in solution), measuring the current from each sensor at the ketone concentrations (i.e., 1, 2, 3, 4, 6, and 8 mmol / L in solution) with a potentiostat, and independently performing a regression (e.g., linear or nonlinear) on each respective in vitro test data set to determine the current. As embodied herein, the plurality of known ketone concentrations can include any range of ketone concentrations from 1 to 8 mmol / L.

[0274] As can be seen in FIG. 22, from time 0 to 0.2 hours, no solution (or a solution without a ketone concentration) is applied to the sensor. At time 0.2, a first ketone solution having a first, relatively low concentration (e.g., 1 millimol / liter (mmol / L)) is applied to the sensor, and the resulting response is recorded. At time 0.4, a second ketone solution having a relatively higher concentration than the first solution is applied to the sensor, and the resulting response is again recorded. The process can proceed iteratively at times 0.6 and thereafter with continually increasing concentrations of ketone solution to obtain empirical data representing the sensitivity of the ketone sensor over a wide range of ketone concentrations. As can be seen, these embodiments of the ketone sensor respond differently to the presence of ketone solution, and these differences become more pronounced as the concentration of the ketone solution increases. Note that although the in vitro test data may appear slightly nonlinear because the x-axis indicates time and not ketone concentration, the sensitivity obtained from the in vitro test data can still be linear.

[0275] In some embodiments, for example, for nonlinear sensitivity, the in vitro data set can be divided into distinct response zones, and each zone can be modeled with a linear sensitivity to approximate the nonlinear curve, resulting in calibration information that will vary depending on the degree of the measured response (e.g., current). As shown in FIG. 16 and described in Example 1 above, the sensitivity can be linear or substantially linear. The in vitro sensitivity (or other sensing characteristic) of the baseline subset can be determined in any desired manner. In some embodiments, multiple different in vitro data subsets from a manufacturing lot can be used to determine multiple sensitivities, and the baseline in vitro sensitivity can be the central tendency of the multiple determined sensitivities, such as the mean or median of the sensitivities. In some embodiments, the baseline in vitro sensitivity can be the central tendency (e.g., the mean or median) of one aspect or characteristic of sensitivity, such as the central tendency of the sensitivity slope or the central tendency of the sensitivity intercept. Other aspects of sensitivity may be used as the in vitro sensitivity for the baseline subset. In some embodiments, instead of deriving individual sensitivities from each of the in vitro test data sets, a simple regression can be performed on the entirety of the in vitro test data from the baseline subset, and this simple regression, or an aspect of it, can be used as the baseline in vitro sensitivity. In all of these embodiments, the in vitro test data sets or the in vitro sensing characteristics determined therefrom can be filtered to remove one or more values ​​(e.g., values ​​below a minimum threshold, values ​​above a maximum threshold, values ​​within a threshold, anomalous values, etc.) before determining the baseline in vitro sensitivity.

[0276] In the example shown, in vitro sensor sensitivity is quantified by the slope of a least-squares regression of current versus ketone concentration, as performed for Example 1 and shown in Figure 19. Calibrated sensor responses were generated for all in vitro studies using the in vitro sensitivity. Calibrated sensor responses generated by 16 sensors at 37 °C with sequential addition of ketone aliquots are shown in Figure 22 (the solid line is the mean, and the shaded area is one standard deviation of the data from the 16 sensors). The average coefficient of variation of sensor response across ketone levels is 5.0%. As seen in Figure 23, the calibrated sensors exhibit a linear response to ketone concentration with an R2 of 0.9994. Importantly, as seen in Figure 23, the linear response exhibits a slope of 1.0003, indicating that the calibrated sensor current using the determined in vitro sensitivity closely approximates the ketone concentration in solution.

[0277] Additionally, the sensor response time was calculated as the time required for the sensor response to change from 10% above baseline to 90% of the plateau for each aliquot addition. The sensor responded to changes in ketone concentration within 4 minutes of adding the ketone aliquot to the test solution (average response time is 228 seconds).

[0278] The stability of 16 sensors over an exemplary intended wear period (e.g., but not limited to, 14 days) was evaluated under simulated conditions. Specifically, 16 sensors were immersed in phosphate buffer containing 8 mM ketone for 14 days at 37°C. The operational stability of the sensors is shown in Figure 24 (the solid line is the average, and the shaded area is one standard deviation of the data from the 16 sensors). Operational stability is important for ketone sensors, specifically because, unlike glucose, baseline ketone levels are typically very low, so the sensor cannot be calibrated by the user. Achieving operational stability beyond 14 days is even more challenging for NAD+-dependent chemicals because NAD+ is a free molecule and is difficult to retain in the sensing chemistry. Additionally, the stability of the sensor response was measured by measuring the drift of the sensor response over the test period. As can be seen in Figure 24, the sensor signal at 8 mM was stable over 14 days, with an average daily signal loss of 0.15% (total signal loss over 14 days is 2.1%). Thus, a sensor can be used with a single calibration for at least 14 days of use. Additionally, a drift correction factor can be determined for an entire lot of sensors within a manufacturing lot based on the drift measured during in vitro testing of a subset of in vivo sensors that have been tested in vitro.

[0279] Finally, interference from ascorbic acid was evaluated by testing 10 sensors under in vitro conditions in phosphate buffer at 37°C. Sensors were tested with 0.6 mM and 1.5 mM ketone in solution. After the sensor signal stabilized, ascorbic acid was introduced to achieve an ascorbic acid concentration of 2 mg / dL, corresponding to a level higher than the maximum therapeutic concentration. The change in sensor response after the addition of ascorbic acid was measured. The interference suggests that the sensor signal may change by no more than the equivalent of 0.2 mmol / L. This interference is independent of the ketone concentration.

[0280] Additionally, a clinical study was conducted to evaluate the sensor's in vivo performance. Twelve healthy volunteers were enrolled and required to follow a low-carbohydrate diet and to be willing to continue the diet throughout the study. The volunteers included 11 female and 1 male participants with a mean age of 32.3 years (range: 20-51 years). One participant had type 1 disease (T1D). One participant was Hispanic; all other participants identified themselves as white. The mean BMI was 24.3 kg / m² (range: 18.6-30 kg / m²), and 7 of the 12 participants had a BMI <25 kg / m². All participants self-reported following a low-carbohydrate diet.

[0281] Two sensors were placed on the back of each upper arm of each study participant (i.e., a total of four sensors per participant). Three of these sensors were functional ketone sensors, and one of the sensors used did not contain functional chemicals (i.e., a total of 36 ketone sensors and 12 sensors without functional chemicals were used). Of the 36 ketone sensors and 12 background sensors tested in this study, 31 ketone sensors and 11 background sensors had evaluable data. Data from the five failed ketone sensors and one background sensor were excluded from data analysis.

[0282] Participants wore the sensor for up to 14 days. The sensor was activated using a reader device such as that described herein, and the sensor began measuring signals 60 minutes after activation. All sensor results were masked to study participants. Study participants were required to take eight fingerstick measurements daily using Precision Xtra ketone test strips while awake, preferably upon waking, before each meal, one hour after each meal, and at bedtime.

[0283] Data from non-functioning sensors from all study participants was used to establish a single participant-independent background current signal model. According to an embodiment, the background current signal may be obtained by in vitro methods, such as those described herein, including, but not limited to, applying various ketone solutions to each analyte sensor, without departing from the scope of the present subject matter. The signal from the functional sensor was first corrected for this background current signal before calculating the ketone results from the functional sensor. Retrospective calibration of each sensor was derived by correlating the sensor current with a reference value. The sensitivity value for each capillary ketone measurement was determined as the ratio of the sensor current (temperature-corrected) to the capillary ketone value, i.e., sensitivity = current / capillary ketone concentration. To simulate the absence of user calibration, no further adjustments were made to assess accuracy over a 14-day period. The sensitivity assigned to each sensor was the median of that sensor's individual sensitivity measurements. Figure 25 shows the response of three functional sensors to body ketone levels over a 14-day period for one of the study participants. As can be seen in Figure 25, all three sensors accurately track the capillary ketone standard throughout the entire 14 days of wear.

[0284] In total, a total of 3,128 paired data points, including in vivo sensor measurements and reference ketone measurements, were collected from the clinical study. Reference measurements ranged from 0 to 5.1 mM, with a median of 0.6 mM. The current measured by the in vivo ketone sensor was calibrated using a previously determined baseline in vitro sensitivity based on a baseline subset of 16 in vivo sensors to determine sensor ketone measurements. Figure 26A shows the correlation between calibrated sensor ketone measurements and ketone reference values ​​based on retrospective sensor calibration using the method described herein. As can be seen in Figure 26A, the calibrated sensor ketone measurements accurately reflect interstitial ketone levels, as indicated by the slope of 0.908. While Figure 26A only shows a predictive relationship up to a ketone value of 5.1 mM, a predictive relationship exists up to a ketone value of approximately 6 mM. In some embodiments, a predictive relationship exists up to a ketone value of approximately 8 mM, as can be seen in Figures 26B-G. According to embodiments, the in vivo ketone sensor can be calibrated using the determined in vitro sensitivity as well as the determined drift correction factor, as described above.

[0285] Additionally, to assess the accuracy of the calibrated sensor ketone results, the sensor ketone results were compared to capillary ketone reference results obtained with Precision Xtra Ketone Test Strips. For concentrations less than 1.5 mM, accuracy relative to the reference was calculated as mM, and for concentrations ≥ 1.5 mM, it was calculated as a percentage. The accuracy results are summarized in Table 8 below. For reference ketone concentrations < 1.5 mM, the overall MAD was 0.129 mM, with 83.4% of the points within + / - 0.225 mM and 91.7% within + / - 0.3 mM. For reference ketone concentrations >= 1.5 mM, the overall MARD was 14.4%, with 76.0% within 20% and 89.7% within 30%. For the full range of concentrations, the values ​​were 82.4% within 0.225 mM / 20% and 91.4% within 0.3 mM / 30%.

[0286] [Table 8]

[0287] According to embodiments disclosed herein, a system can include an in vivo ketone sensor having a distal portion and a proximal portion configured to be placed in contact with a user's interstitial fluid; and a sensor control unit, the sensor control unit including at least one contact in electrical communication with the proximal portion of the sensor and a transmitter configured to communicate with a remote device, the sensor control unit configured to receive the generated signal and convert the generated signal into ketone concentration data using a sensitivity associated with the in vivo ketone sensor, and the transmitter configured to communicate the ketone concentration data to the remote device. The sensor can include a working electrode, a sensing layer including β-hydroxybutyrate dehydrogenase, and a membrane layer configured to restrict transport of one or more biomolecules, and the in vivo ketone sensor is configured to generate a signal at the working electrode corresponding to the amount of ketones in the interstitial fluid.

[0288] It is intended that all features, elements, components, functions, and steps described with respect to any embodiment provided herein are freely combinable and interchangeable with those from any other embodiment. If a feature, element, component, function, or step is described with respect to only one embodiment, it should be understood that that feature, element, component, function, or step can be used with all other embodiments described herein unless expressly stated otherwise. Therefore, even if the following description does not explicitly state that such combinations or substitutions are possible in a particular example, this paragraph always serves as a prior basis and written support for the introduction of claims that combine features, elements, components, functions, and steps from different embodiments or substitute features, elements, components, functions, and steps from one embodiment with features, elements, components, functions, and steps from another embodiment. It is expressly recognized that explicitly listing every possible combination and permutation would be unduly burdensome, especially considering that the permissibility of all such combinations and permutations would be readily recognized by those skilled in the art.

[0289] In all of the embodiments described herein, an electronic device capable of processing data or information can include a processing circuit communicatively coupled to a non-transitory memory, which can store one or more computer programs or software instructions that, when executed by the processing circuit, cause the processing circuit to perform actions. For any of the method embodiments disclosed herein, systems and devices capable of performing those methods, or portions thereof, using a processing circuit and a non-transitory memory having stored thereon one or more instructions that, when executed by the processing circuit, cause the processing circuit to perform one or more steps of the method (or to perform one or more steps of the method, such as transmitting or displaying information), are within the scope of this disclosure.

[0290] Computer programs or software instructions for performing operations in accordance with the described subject matter may be written in any combination of one or more programming languages, including object-oriented programming languages ​​such as Java, JavaScript, Smalltalk, C++, C#, Transact-SQL, XML, PHP, and conventional procedural programming languages ​​such as the "C" programming language or similar programming languages. The program instructions may be executed entirely on the computing device, partially on the computing device, as a standalone software package, partially on the local computing device and partially on a remote computing device, or entirely on a remote computing device or server. In the latter scenario, the remote computing device may be connected to the local computing device via any type of network, including a local area network (LAN) or a wide area network (WAN), or the connection may be to an external computer (e.g., via the Internet using an Internet Service Provider).

[0291] To the extent that the embodiments disclosed herein include or operate in conjunction with memory, storage, and / or computer-readable medium, that memory, storage, and / or computer-readable medium is non-transitory. Thus, to the extent that memory, storage, and / or computer-readable medium is covered by one or more claims, that memory, storage, and / or computer-readable medium is only non-transitory.

[0292] As used in this specification and the appended claims, the singular forms "a," "an," and "the" include plural referents unless the context clearly dictates otherwise. While the embodiments are susceptible to various modifications and alternative forms, specific examples thereof have been shown in the drawings and are described in detail herein. However, it should be understood that these embodiments are not limited to the particular forms disclosed; on the contrary, these embodiments encompass all modifications, equivalents, and alternatives falling within the spirit of the disclosure. Furthermore, any feature, function, step, or element of the embodiments may be recited or added to the claims, as well as any negative limitations that define the scope of the claims by any feature, function, step, or element not within their scope.

Claims

1. 1. A method for converting a signal generated using an in vivo sensor into ketone concentration data, comprising:

1. A ketone sensor having a distal portion configured to be placed in contact with interstitial fluid of a user and a proximal portion, a working electrode; a sensing layer comprising β-hydroxybutyrate dehydrogenase and free NAD; Membrane and providing a ketone sensor comprising: receiving, at a sensor control unit, a signal corresponding to a ketone concentration in the interstitial fluid of the user; converting, by the sensor control unit, the signal into the ketone concentration data based on a single predetermined calibration and a predetermined drift correction factor; and Displaying the ketone concentration data. Including, The method, wherein the predetermined drift correction factor accounts for an average daily signal loss measured in vitro, and the single predetermined calibration and the predetermined drift correction factor are suitable for use for 14 days.

2. 10. The method of claim 1, wherein the average daily signal loss is determined by placing the in vivo sensor in a solution containing a known ketone concentration for a period of time.

3. The method of claim 2 , wherein the average daily signal loss is determined for a subset of sensors from a manufacturing lot.

4. 10. The method of claim 1, wherein the average daily signal loss is 0.15% when exposed to a phosphate buffer solution having 8 mM ketone at 37°C for 14 days.

5. The sensor control unit at least one contact in electrical communication with the proximal portion of the in vivo ketone sensor; a transmitter configured to communicate the ketone concentration data to a remote device; The method of claim 1 , comprising:

6. 6. The method of claim 5, wherein the remote device includes a display unit configured to display a graph of in vivo ketone concentrations over a period of time.

7. The method of claim 1 , wherein the distal portion of the in-vivo sensor further comprises a counter electrode.

8. The method of claim 7 , wherein the sensing layer further comprises a redox mediator.

9. The method of claim 8 , wherein the sensing layer further comprises diaphorase.

10. 10. The method of claim 9, wherein the membrane is a mass transport limiting membrane for limiting the flux of the ketone.

11. The method of claim 10 , wherein the membrane is disposed on the sensing layer.

12. 12. The method of claim 11, wherein the mass transport limiting membrane comprises a cross-linked polymer containing heterocyclic nitrogen groups.

13. 13. The method of claim 12, wherein the mass transport limiting membrane comprises polyvinylpyridine.

14. 10. The method of claim 1, wherein converting the signal to the ketone concentration data does not require calibration by the user.

15. 15. The method of claim 14, wherein the single predetermined calibration is based on a predetermined in vitro sensitivity.

16. 16. The method of claim 15, wherein the predetermined in vitro sensitivity is determined by measuring currents in response to known ketone concentrations and performing a regression.

17. The method of claim 16 , wherein the regression is linear.

18. 17. The method of claim 16, wherein the predetermined in vitro sensitivity is determined for a subset of sensors from a manufacturing lot.

19. 16. The method of claim 15, wherein the predetermined in vitro sensitivity correlates with in vivo sensitivity over a concentration range of 0 mM to 8 mM.

20. 20. The method of claim 19, wherein the predetermined in vitro sensitivity correlates with in vivo sensitivity over a concentration range of 0 mM to 6 mM.

21. 21. The method of claim 20, wherein the predetermined in vitro sensitivity correlates to in vivo sensitivity over a concentration range of 0 mM to 5.1 mM.

22. 15. The method of claim 14, wherein the single predetermined calibration includes the user-independent predetermined in vivo background for correcting the signal.

23. 23. The method of claim 22, wherein the predetermined in vivo background is determined using a plurality of in vivo ketone sensors that do not include a functional ketone-sensing chemical.

24. 1. A method for converting a signal generated with an in vivo ketone sensor comprising a distal portion configured to contact interstitial fluid of a user and a proximal portion configured to be placed on the skin of the user, the method comprising: contacting the distal portion of the ketone sensor with the user's interstitial fluid to generate a signal corresponding to a ketone concentration in the user's interstitial fluid, wherein the distal portion of the ketone sensor: a working electrode; a sensing layer comprising β-hydroxybutyrate dehydrogenase and free NAD; Membrane and contacting the distal portion of the ketone sensor with the user's interstitial fluid to generate a signal corresponding to a ketone concentration in the user's interstitial fluid; receiving, at a sensor control unit, the signal corresponding to the ketone concentration; converting, by the sensor control unit, the signal into the ketone concentration data based on a single predetermined calibration and a predetermined drift correction factor; and Displaying the ketone concentration data. wherein the predetermined drift correction factor accounts for an average daily signal loss measured in vitro, and wherein the single predetermined calibration and the predetermined drift correction factor are suitable for use for 14 days.

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