WO2013066847A1

WO2013066847A1 - Analyte sensor

Info

Publication number: WO2013066847A1
Application number: PCT/US2012/062539
Authority: WO
Inventors: Kenneth J. Doniger; Martin J. Fennell
Original assignee: Abbott Diabetes Care Inc
Current assignee: Abbott Diabetes Care Inc
Priority date: 2011-10-31
Filing date: 2012-10-30
Publication date: 2013-05-10
Anticipated expiration: 2014-04-30

Abstract

Methods and systems for disabling an analyte sensor after a predetermined time period or after a time period associated with a useful sensor life has elapsed are provided. Embodiments include breaking a conductive trace of the analyte sensor by applying a current signal at or exceeding a predetermined level to break the conductive trace and disable the sensor.

Description

ANALYTE SENSOR

PRIORITY

[0001] The present application claims priority to U.S. provisional application no.

61/553,938 filed October 31, 2011, entitled "Analyte Sensor", the disclosure of which is incorporated herein by reference for all purposes.

BACKGROUND

[0002] The introduction and temporary implantation through the skin, e.g.,

transcutaneously, percutaneously and/or subcutaneously, of sensors, or biosensors, as they are sometimes referred, has become very common in the treatment of patients inflicted with or suffering from any one of many different types of conditions. These implantable sensors include those monitoring a given parameter that indicates a certain bodily condition, e.g., a patient's glucose level, or the actual state of a treatment, e.g., monitoring the concentration of a drug dispensed to the patient or a body substance influenced by the drug.

[0003] In recent years, a variety of temporarily implantable sensors have been developed for a range of medical applications for detecting and/or quantifying specific agents, e.g., analytes, in a patient's body fluid such as blood or interstitial fluid. Such analyte sensors may be fully or partially implanted below the epidermis in a blood vessel or in the subcutaneous tissue of a patient for direct contact with blood or other extra-cellular fluid, such as interstitial fluid, wherein such sensors can be used to obtain periodic and/or continuous analyte readings over a period of time.

[0004] Certain transcutaneous analyte sensors have an electrochemical configuration in which the implantable portion of these sensors includes exposed electrodes and chemistry that react with a target analyte. Exposed conductive contacts are externally located at a proximal end of the sensor for electrical connection with a sensor control unit which is typically mountable on the skin of the patient. One common application of such analyte sensor systems is in the monitoring of glucose levels in diabetic patients. Such readings can be especially useful in monitoring and/or adjusting a treatment regimen which may include the regular and/or emergent administration of insulin to the patient.

[0005] Typically, the on-body control or electronics unit of such transcutaneous sensor systems is reusable with a plurality of sensors, the latter of which are typically designed for a single use for a limited time period. One potential problem that may occur is the continued use of the sensor beyond its intended life. For example, a host may not remove the sensor after its intended life and/or the host may detach and reattach the electronics unit with the sensor which may cause a refresh of the sensor system, allowing use beyond its intended life.

[0006] Accordingly, systems and methods are needed for ensuring that such implantable sensors are used only for the intended duration, and that accidental or intentional efforts to improperly extend or reuse a sensor are avoided.

SUMMARY

[0007] The present disclosure is generally directed to in vivo sensor systems, devices and methods for continuously or semi-continuously monitoring or measuring biological or physiological parameters in bodily fluid. Embodiments of the subject systems include on- skin or on-body control electronics adapted for placement on the skin surface and adapted to receive a portion of a sensor configured to be operatively positioned transcutaneously, subcutaneously or on the skin surface. A feature of the subject systems, devices and methods is the disabling of the sensor by use of the control electronics upon the passage of a predetermined time period, upon expiration of the sensor's useful life, upon a user- initiated action, such as upon removing the control unit from the sensor, or upon determination by the control unit that the sensor is in some way defective.

[0008] One embodiment of the subject systems is for the continuous measurement of an analyte in a host in which the system includes an analyte sensor configured to measure a concentration of an analyte in a host, the sensor having a portion configured for contact with the analyte under a skin surface; an on body unit configured to operatively couple with a portion of the analyte sensor positionable above the skin surface, the on-body unit comprising a processor for processing analyte-related data received from the analyte sensor; and a sensor-disabling circuit coupled to the processor and including a fuse provided on the portion of the analyte sensor positionable above the skin surface. In certain embodiments of this system, the sensor-disabling circuit is configured to destroy the fuse and disable the sensor upon receipt of a sensor disable signal from the processor, which signal may be initiated upon lapse of a predetermined time period, such as upon lapse of the useful life of the sensor or expiration of the sensor, or upon a user initiated action, such as by removing the on-body unit from the sensor. [0009] The sensor-disabling circuit fuse may include a conductive trace electrically coupled between two conductive contacts of the analyte sensor. The sensor-disabling circuit may include a switch configured to electrically couple the two conductive contacts to a source of power to provide an electrical current to the fuse. In certain embodiments, at least one of the conductive contacts of the analyte sensor is one of the sensor electrodes used to electrochemically sense or detect the target analyte. In other embodiments, at least one of the conductive contacts is not a sensor electrode. Still yet, the fuse may be provided on a temperature gauge, such as a thermocouple, of the analyte sensor wherein the

thermocouple forms at least a portion of the fuse.

[0010] In certain embodiments, the sensor-disabling circuit may include an electronic circuit or device with similar functionality to a fuse, such that, the electronic circuit or device may include an electronic switch configured to turn off or open (i.e., a normally closed switch) when activated by a current, voltage, or other electronic signal. In certain embodiments, the sensor-disabling circuit may record the status of the sensor and transmit the active or inactive status to the processor. Upon expiration or deactivation of the sensor, the status may be switched to a state to indicate that the sensor is no longer active. A digital signal may then be sent to the processor to indicate that the sensor is no longer active.

[0011] The present disclosure further includes methods for disabling an in vivo sensor transcutaneously implanted within a host. One such method includes electronically coupling an on-body unit of an analyte monitoring system to a portion of an analyte sensor positioned above a skin surface, and then transmitting an electrical current from the on- body unit to a fuse provided on the portion of the analyte sensor above the skin surface where the electrical current has a magnitude sufficient to destroy the fuse. The on-body unit may include a processor and a sensor-disable switch where the step of transmitting an electrical current, voltage, or other electrical signal involves the processor generating a sensor-disable signal from to the processor to the sensor-disable switch and then coupling the fuse or electronic switch to a power supply.

[0012] In certain embodiments, the electrical current, or voltage, or other electrical signal is transmitted after the lapse of a predetermined time period, such as upon expiration of the sensor. In other embodiments, the electrical current is transmitted upon removal of the on- body unit from the analyte sensor or upon the detection of a defective sensor by the on- body unit. [0013] These and other objects, advantages, and features of the present disclosure will become apparent to those persons skilled in the art upon reading the details of the present disclosure as more fully described below.

BRIEF DESCRIPTION OF THE DRAWINGS

[0014] Embodiments of the present disclosure are best understood from the following detailed description when read in conjunction with the accompanying drawings. It is emphasized that, according to common practice, the various features of the drawings are not to scale. On the contrary, the dimensions of the various features are arbitrarily expanded or reduced for clarity. Included in the drawings are the following figures:

[0015] Fig. 1 illustrates a block diagram of an embodiment of a data monitoring and management system according to the present disclosure;

[0016] Fig. 2 illustrates a block diagram of an embodiment of the data processing unit of the data monitoring and management system of Fig. 1; and

[0017] Fig. 3 illustrates a block diagram of an embodiment of the receiver unit of the data monitoring and management system of Fig. 1.

INCORPORATION BY REFERENCE

[0018] Patents, applications and/or publications described herein, including the following patents, applications and/or publications are incorporated herein by reference for all purposes: U.S. Patent Nos. 4,545,382, 4,711,245, 5,262,035, 5,262,305, 5,264,104, 5,320,715, 5,356,786, 5,509,410, 5,543,326, 5,593,852, 5,601,435, 5,628,890, 5,820,551, 5,822,715, 5,899,855, 5,918,603, 6,071,391, 6,103,033, 6,120,676, 6,121,009, 6,134,461, 6,143,164, 6,144,837, 6,161,095, 6,175,752, 6,270,455, 6,284,478, 6,299,757, 6,338,790, 6,377,894, 6,461,496, 6,503,381, 6,514,460, 6,514,718, 6,540,891, 6,560,471, 6,579,690, 6,591,125, 6,592,745, 6,600,997, 6,605,200, 6,605,201, 6,616,819, 6,618,934, 6,650,471, 6,654,625, 6,676,816, 6,730,200, 6,736,957, 6,746,582, . 6,749,740, 6,764,581, 6,773,671, 6,881,551, 6,893,545, 6,932,892, 6,932,894, 6,942,518, 7,041,468, 7,167,818, 7,299,082, and 7,866,026, U.S. Patent Publication Nos. 2004/0186365, 2005/0182306,

2006/0025662, 2006/0091006, 2007/0056858, 2007/0068807, 2007/0095661,

2007/0108048, 2007/0199818, 2007/0227911, 2007/0233013, 2008/0066305,

2008/0081977, 2008/0102441, 2008/0148873, 2008/0161666, 2008/0267823,

2009/0054748, 2009/0294277, 2010/0213057, 2010/0081909, 2009/0247857, 2011/0106126, 2011/0082484, 2010/0326842, 2010/0198034, 2010/0324392,

2010/0230285, 2010/0313105, 2011/0213225, 2011/0021889, 2011/0193704,

2011/0190603, and 2011/0191044, U.S. Patent Application Nos. 13/071,461, 13/071,487, and 13/071,497, and U.S. Provisional Application No. 61/325,260.

DETAILED DESCRIPTION

[0019] Before the present disclosure is further described, it is to be understood that this disclosure is not limited to particular embodiments described, as such may, of course, vary. It is also to be understood that the terminology used herein is for the purpose of describing particular embodiments only, and is not intended to be limiting, since the scope of the present disclosure will be limited only by the appended claims.

[0020] As will be apparent to those of skill in the art upon reading this disclosure, each of the individual embodiments described and illustrated herein has discrete components and features which may be readily separated from or combined with the features of any of the other several embodiments without departing from the scope or spirit of the present disclosure.

[0021] Where a range of values is provided, it is understood that each intervening value, to the tenth of the unit of the lower limit unless the context clearly dictates otherwise, between the upper and lower limit of that range and any other stated or intervening value in that stated range, is encompassed within the present disclosure. The upper and lower limits of these smaller ranges may independently be included in the smaller ranges, and are also encompassed within the present disclosure, subject to any specifically excluded limit in the stated range. Where the stated range includes one or both of the limits, ranges excluding either or both of those included limits are also included in the present disclosure.

[0022] Unless defined otherwise, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this disclosure belongs. Although any methods and materials similar or equivalent to those described herein can also be used in the practice or testing of the present disclosure, exemplary methods and materials are now described. All publications mentioned herein are incorporated herein by reference to disclose and describe the methods and/or materials in connection with which the publications are cited. [0023] As used herein and in the appended claims, the singular forms "a," "an," and "the" include plural referents unless the context clearly dictates otherwise. It is further noted that the claims may be drafted to exclude any optional element. As such, this statement is intended to serve as antecedent basis for use of such exclusive terminology as "solely," "only" and the like in connection with the recitation of claim elements, or use of a

"negative" limitation.

[0024] The publications discussed herein are provided solely for their disclosure prior to the filing date of the present application. Nothing herein is to be construed as an admission that the present disclosure is not entitled to antedate such publication by virtue of prior disclosure. Further, the dates of publication provided may be different from the actual publication dates which may need to be independently confirmed.

[0025] Generally, the illustrated embodiments of the present disclosure relate to the

continuous, semi-continuous, periodic and/or automatic in vivo monitoring of the level of one or more analytes using a continuous or semi-continuous analyte monitoring system that includes an in vivo analyte sensor at least a portion of which is to be positioned beneath a skin surface of a user for a period of time. The subject systems may further include or be configured for the discrete or in vitro monitoring of one or more analytes using an external device and an in analyte test strip in conjunction with the in vivo components. Embodiments include combined or combinable devices, systems and methods and/or transferring data between an in vivo continuous monitoring system and an in vitro discrete monitoring system.

[0026] Embodiments of the subject in vivo analyte sensors include wholly implantable analyte sensors and analyte sensors in which only a portion of the sensor is positioned under the skin and another portion of the sensor resides above the skin for coupling with an on body device which may house components including but not limited to a transmitter, receiver, transceiver, processor, etc. The sensor may be, for example, transcutaneously or subcutaneously positionable in a patient for contact with a bodily fluid such as interstitial fluid or blood. In other embodiments, the analyte sensors may be insertable into a vein, artery, or other portion of the body containing fluid.

[0027] Embodiments of the analyte sensors of the subject disclosure may be configured for monitoring the level of the analyte over a time period which may range from minutes, hours, days, weeks, or longer. Of interest are analyte sensors, such as glucose sensors, that are capable of in vivo detection of an analyte for about one hour or more, e.g., about a few hours or more, e.g., about a few days of 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 several weeks or at least one month. Future analyte levels may be predicted based on information obtained, e.g., the current analyte level at time tO, the rate of change of the analyte, etc. Predictive alarms may notify the user of a predicted analyte level that may be of concern in advance of the user's analyte level reaching the future level. This provides the user an opportunity to take corrective action.

[0028] Embodiments of the subject disclosure are further described primarily with respect to glucose monitoring devices and systems, and methods of glucose detection, for convenience only and such description is in no way intended to limit the scope of the disclosure. It is to be understood that the analyte monitoring system may be configured to monitor a variety of analytes at the same time or at different times.

[0029] Analytes that may be monitored include, but are not limited to, acetyl choline, amylase, bilirubin, cholesterol, chorionic gonadotropin, creatine kinase (e.g., CK-MB), creatine, creatinine, DNA, fructosamine, glucose, glutamine, growth hormones, hormones, ketone bodies, lactate, peroxide, prostate-specific antigen, prothrombin, RNA, thyroid stimulating hormone, and troponin. The concentration of drugs, such as, for example, antibiotics (e.g., gentamicin, vancomycin, and the like), digitoxin, digoxin, drugs of abuse, theophylline, and warfarin, may also be monitored. In those embodiments that monitor more than one analyte, the analytes may be monitored at the same or different times.

[0030] The subject disclosure also includes sensors used in sensor-based drug delivery systems. The system may provide a drug to counteract the high or low level of the analyte in response to the signals from one or more sensors. Alternatively, the system may monitor the drug concentration to ensure that the drug remains within a desired therapeutic range. The drug delivery system may include one or more (e.g., two or more) sensors, a processing unit such as a transmitter, a receiver/display unit, and a drug administration system. In some cases, some or all components may be integrated in a single unit. A sensor-based drug delivery system may use data from the one or more sensors to provide necessary input for a control algorithm/mechanism to adjust the administration of drugs, e.g., automatically or semi-automatically. As an example, a glucose sensor may be used to control and adjust the administration of insulin from an external or implanted insulin pump. [0031] Referring now to Fig. 1, there is shown a block diagram of a data monitoring and management system such as, for example, an analyte (e.g., glucose) monitoring system 100 in accordance with certain embodiments of the present disclosure. In such

embodiments, analyte monitoring system 100 includes an analyte sensor 101, a data processing unit 102 connectable to sensor 101, and a primary receiver unit 104 which is configured to communicate with data processing unit 102 via a communication link 103. In certain embodiments, at least data processing unit 102 is provided within the housing of an on-body unit.

[0032] In certain embodiments, sensor 101 is physically positioned in or on the body of a user whose analyte level is being monitored. Sensor 101 may be configured to at least periodically sample the analyte level of the user and convert the sampled analyte level into a corresponding signal for transmission by data processing unit 102. Various

embodiments and constructs and functions of sensor 101 are described in greater detail below.

[0033] Sensor 101 is couplable to data processing unit 102 such that both devices are positionable in or on the user's body, with at least a portion of analyte sensor 101 positioned transcutaneously. In certain embodiments, sensor 101 and data processing unit 102 formed as a single integrated unit, whereby upon securement of data processing unit 102 to the user's body, sensor 101 integrated therewith is inserted through the skin of the user for monitoring the subject analyte, such as glucose. Data processing unit 102 may include a fixation element such as adhesive or the like to secure it to the user's body. A mount (not shown) attachable to the user and mateable with data processing unit 102 may be used. For example, a mount may include an adhesive surface. In one embodiment, sensor 101 or data processing unit 102 or a combined sensor/data processing unit may be wholly implantable under the skin layer of the user. Data processing unit 102 performs data processing functions, where such functions may include but are not limited to, filtering and encoding of data signals, each of which corresponds to a sampled analyte level of the user received from sensor 101, for transmission to, for example, primary receiver unit 104 via communication link 103.

[0034] In certain embodiments, primary receiver unit 104 may include an analog interface section including an RF receiver and an antenna configured to communicate with data processing unit 102 via communication link 103, and a data processing section for processing the received data from data processing unit 102. Processing may include data decoding, error detection and correction, data clock generation, data bit recovery, etc., or any combination thereof. In operation, primary receiver unit 104 in certain embodiments is configured to synchronize with data processing unit 102 to uniquely identify data processing unit 102, based on, for example, an identification information of data processing unit 102, and thereafter, to periodically receive signals transmitted from data processing unit 102 associated with the monitored analyte levels detected by sensor 101.

[0035] Referring again to Fig. 1, analyte monitoring system 100 may include a data processing terminal 105 for further processing of the data received from analyte sensor 101. Data processing terminal 105 may include a personal computer, a portable computer such as a laptop or a handheld device (e.g., personal digital assistants (PDAs), telephone such as a cellular phone (e.g., a multimedia and Internet-enabled mobile phone such as an iPhone or similar phone), mp3 player, pager, and the like), drug delivery device, each of which may be configured for data communication with the receiver via a wired or a wireless connection. Additionally, data processing terminal 105 may further be connected to a data network (not shown) for storing, retrieving, updating, and/or analyzing data corresponding to the detected analyte level of the user. In certain embodiments, data processing terminal 105 may be configured to receive the analyte signals directly from data processing unit 102, and thus, incorporate the functions of primary receiver unit 104 including data processing functions.

[0036] Data processing terminal 105 may include an infusion device such as an insulin infusion pump or the like, which may be configured to administer insulin to patients, and which may be configured to communicate with primary receiver unit 104 for receiving, among others, the measured analyte level. Alternatively, primary receiver unit 104 may be configured to integrate an infusion device therein so that primary receiver unit 104 is configured to administer insulin (or other appropriate drug) therapy to patients, for example, for administering and modifying basal profiles, as well as for determining appropriate boluses for administration based on, among others, the detected analyte levels received from data processing unit 102. The infusion device (not shown) may be an external device or an internal device (wholly implantable in a user).

[0037] Also shown in Fig. 1 is an optional secondary receiver unit 106 which is operative ly coupled to the communication link and configured to receive data transmitted from data processing unit 102. Secondary receiver unit 106 may be configured to communicate with primary receiver unit 104, as well as data processing terminal 105. Secondary receiver unit 106 may be configured for bi-directional wireless communication with each of primary receiver unit 104 and data processing terminal 105. As discussed in further detail below, in certain embodiments secondary receiver unit 106 may be a de-featured receiver as compared to the primary receiver, i.e., the secondary receiver may include a limited or minimal number of functions and features as compared with primary receiver unit 104. As such, secondary receiver unit 106 may include a smaller (in one or more, including all, dimensions), compact housing or embodied in a device such as a wrist watch, arm band, etc., for example. Alternatively, secondary receiver unit 106 may be configured with the same or substantially similar functions and features as primary receiver unit 104.

Secondary receiver unit 106 may include a docking portion to be mated with a docking cradle unit for placement by, e.g., the bedside for nighttime monitoring, and/or a bidirectional communication device. A docking cradle may recharge a power supply.

[0038] In certain embodiments, primary receiver unit 104 may be further configured to transmit data to data processing terminal 105 to evaluate or otherwise process or format data received by primary receiver unit 104. Additionally or alternatively, data processing terminal 105 may be configured to receive data directly from data processing unit 102 via a communication link which may optionally be configured for bi-directional

communication. Further, data processing unit 102 may include a transmitter or a transceiver to transmit to and/or receive data from primary receiver unit 104 and/or data processing terminal 105 and/or secondary receiver unit 106.

[0039] In certain embodiments, communication link 103 as well as one or more of the other communication interfaces shown in Fig. 1 or mentioned above, may use one or more of: a radio frequency (RF) communication protocol, an infrared communication protocol, a Bluetooth® enabled communication protocol, an 802.1 lx wireless communication protocol, or an equivalent wireless communication protocol which would allow secure, wireless communication of several units (for example, per HIPAA requirements), while avoiding potential data collision and interference.

[0040] While only one sensor 101, data processing unit 102 and data processing terminal 105 are shown in the embodiment of analyte monitoring system 100, it will be appreciated by one of ordinary skill in the art that the system may include more than one sensor 101 and/or more than one data processing unit 102, and/or more than one data processing terminal 105. Multiple sensors may be positioned in a patient for analyte monitoring at the same or different times. In certain embodiments, analyte information obtained by a first positioned sensor may be employed as a comparison to analyte information obtained by a second sensor. This may be useful to confirm or validate analyte information obtained from one or both of the sensors. Such redundancy may be useful if analyte information is contemplated in critical therapy-related decisions. In certain embodiments, a first sensor may be used to calibrate a second sensor.

[0041] The analyte monitoring system 100 may be a continuous monitoring system, or semi-continuous, or a discrete monitoring system. 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 conflict may be readily resolved between the various components within the analyte monitoring system 100. For example, unique IDs, communication channels, and the like, may be used. Examples of analyte sensors and associated analyte monitoring systems can be found in, for example, but not limited to, U.S. Patent Nos. 6,134,461; 6,175,752; 6,284,478; 6,560,471; 6,579,690;

6,746,582; 6,932,892; 7,299,082; 7,381,184; 7,618,369 and 7,697,967; and U.S. Patent Application Publication Nos. 2008/0161666, 2009/0054748, 2009/0247857 and

2010/0081909, the disclosures of each of which are incorporated by reference herein for all purposes.

[0042] Turning now to Fig. 2, there is shown a block diagram of an embodiment of a data processing unit 102 of analyte monitoring system 100 of Fig. 1 in accordance with certain embodiments of the present disclosure. Data processing unit 102 in one embodiment includes an analog interface 201 configured to communicate with the sensor 101 via various electrical contacts 210, 211, 212, 213. In the embodiment of Fig. 2, sensor 101 includes four contacts, three of which are electrodes - working electrode (W) 210, reference electrode (R) 212, and counter electrode (C) 213, each operatively coupled to analog interface 201 of data processing unit 102. The embodiment of Fig. 2 also shows optional guard contact (G) 211. In other embodiments, fewer or more electrodes may be employed. For example, the counter and reference electrode functions may be served by a single counter/reference electrode, or there may be more than one working electrode and/or reference electrode and/or counter electrode.

[0043] Analog interface 201 is configured to provide interface circuitry to operate sensor 101 and, in turn, receive signals from sensor 101 representative of the analyte detected by sensor 101. The signals between the two may be provided by one or more electrochemical techniques including, for example, amperometric, coulometric, potentiometric, voltammetric and/or other electrochemical techniques. For example, to obtain amperometric measurements, analog interface 201 includes a potentiostat that provides a constant potential to sensor 101. In other embodiments, analog interface 201 includes an amperostat that supplies a constant current to a sensor and can be used to obtain coulometric or potentiometric measurements. Thus, the signals received by analog interface 201 from sensor 101 generally have at least one characteristic, such as, for example, current, voltage, or frequency, or the like, which varies with the concentration of the analyte being detected.

[0044] The information-carrying portion of the signals received from sensor 101 may be converted from one characteristic to another in order to provide a signal that is, for example, more easily transmitted, readable by digital circuits, and/or less susceptible to noise contributions. This conversion may be performed by one or more of the components of data processing unit 102 including, for example, analog interface 201, a processor 204, and/or an RF transmitter/receiver 206. For example, one or more of these components may include a current-to-voltage or current-to-frequency converter.

[0045] Processor 204, such as a central processing unit (CPU), a microprocessor or a microcontroller, for example, in certain embodiments, may include one or more application-specific integrated circuits (ASIC) used to implement one or more functions or routines associated with the operation of data processing unit 102 using, for example, one or more state machines and buffers. In one embodiment, processor 204 also includes a memory (not shown) for storing data such as the identification information for data processor unit 102, as well as the data signals received from sensor 101. The stored information may be retrieved and processed for transmission to receiver unit 104.

[0046] Data processing unit 102 may further include a user input 202, a temperature detection section 203, a clock 208, and a leak detection circuit 214, each of which is operatively coupled to processor 204. Temperature detection section 203 is configured to monitor the temperature of the skin near the sensor insertion site. The temperature reading is used to adjust the analyte readings obtained from analog interface 201. Clock 208 is provided to, among other functions, supply real time information to processor 204. Leak detection circuit 214, coupled between guard contact (G) 211 and processor 204, in accordance with one embodiment of the present disclosure, may be configured to detect leakage current in sensor 101 to determine whether the measured sensor data is corrupt or whether the measured data from sensor 101 is accurate. [0047] Further shown in Fig. 2 are a serial communication section 205 and an RF transmitter/receiver 206, each of which is also operatively coupled to the processor 204. In certain embodiments, a data path is provided from the analog interface 201 to serial communication section 205 via a dedicated link, and thereafter to processor 204, and then to RF transmitter/receiver 206. As such, data processing unit 102 is configured to transmit processed and encoded data signals received from sensor 101 to primary receiver 104 (Fig. 1) via communication link 103 (Fig. 1). Additionally, the communication data path between analog interface 201 and RF transmitter/receiver 206 allows for the configuration of data processing unit 102 for operation upon completion of the manufacturing process as well as for direct communication for diagnostic and testing purposes.

[0048] RF transmitter/receiver 206 may be configured for operation in the frequency band of 315 MHz to 322 MHz, for example, in the United States. Within the scope of the present disclosure, other data communication frequencies and protocols are contemplated including, for example, 13.56MHz frequency. Further, in one embodiment, the RF transmitter/receiver 206 is configured to modulate the carrier frequency by performing Frequency Shift Keying and Manchester encoding. In one embodiment, the data transmission rate is 19,200 symbols per second, with a minimum transmission range for communication with the receiver 104.

[0049] Data processing unit 102 also includes a power supply 207, such as a battery, to operate the unit, in certain embodiments, for a minimum of three months of continuous operation after having been stored for 18 months in a low-power (non-operating) mode. In one embodiment, this may be achieved by processor 204 operating in low power modes in the non-operating state, for example, drawing no more than approximately 1 μΑ of current. The final step during the manufacturing process may be to place data processing unit 102 in the lower power, non-operating state (i.e., the post-manufacture sleep mode). In this manner, the shelf life of data processing unit 102 may be significantly improved.

[0050] In certain embodiments, data processing unit 102 and sensor 101 collectively provide a feature for disabling sensor 101 after a predetermined time period has elapsed or expired, or upon sensor expiration. Sensor expiration can be determined in a variety a ways. For example, in some embodiments, sensor expiration is a predetermined date that can be established by the manufacturer, which can be stored in memory or encoded on the sensor using a resistor or capacitor or inductor, where a particular resistance or

capacitance or inductance corresponds to a particular expiration date. In some embodiments, the sensor can have a sensor identification number or serial number that can be used to determine the sensor expiration date. In other embodiments, sensor expiration can be determined dynamically through the measurement of predetermined sensor criteria, such as sensor resistance, rate of change of sensor resistance, sensor sensitivity and/or rate of change of sensor sensitivity, where a measurement of a predetermined sensor criterion that exceeds or falls below a predetermined threshold value or level can indicate sensor expiration.

[0051] In certain embodiments, the sensor-disabling feature includes a sensor disable circuit

215 within data processing unit 102 and a fuse section 216 within sensor 101. In certain embodiments, sensor disable circuit 215 is coupled to processor 204 and to sensor 101 via guard contact 211 and counter electrode 213, for example. In other embodiments, sensor disable circuit 215 may be coupled to sensor 101 via any combination of one or more sensor electrodes or contacts. In certain embodiments, sensor disable circuit 215 may be indirectly coupled to sensor 101 via one or more components of data processing unit 102, such as, for example, analog interface 201. Sensor fuse section 216, which in certain embodiments is in the form of a conductive trace or element, is provided between guard contact 211 and counter electrode 213 on the proximal portion of sensor 101 which resides above the skin surface when sensor 101 is operatively positioned within a patient. In other embodiments, fuse section 216 in the form of a conductive trace or element, may be provided between other contacts or electrodes of sensor 101, including between any combination of one or more working electrodes, reference electrodes, counter electrodes, reference/counter electrodes, or guard contact, or any other appropriate location in the sensor circuitry. In certain embodiments, the location of the fuse section is located on the proximal portion of the sensor 101 which resides above the skin surface when the sensor 101 is operatively positioned within a patient. In certain embodiments, fuse section 216 may be a portion of a single electrode or contact. In certain embodiments, fuse section

216 may be a separate trace or element from all the electrodes and/or contacts of sensor 101.

[0052] In certain embodiments, lapse of the predetermined time period, such as a useful sensor life time period, or a determination of sensor expiration is achieved by

measurement of a predetermined sensor criterion, or in certain embodiments the sensor expiration date is tracked by processor 204. Sensor life can be monitored by processor 204, for example, by utilizing a counter that reflects the current elapsed sensor life. Examples of methods and systems for monitoring sensor life can be found in, for example, but not limited to, U.S. publication nos. 2008/0281840 and 2010/0014626, the disclosures of each of which are incorporated herein by reference for all purposes.

[0053] In certain embodiments, upon lapse of the predetermined time period or sensor expiration, processor 204 may trigger sensor disable circuit 215. Sensor disable circuit 215, by means of, for example, an electronic, computer logic or physical switch mechanism or the like, then couples, for example, guard contact 211 and counter electrode 213 to power supply 207 to provide a current to fuse section 216 of sensor 101. The resistance of fuse section 216, which can be predetermined, as dictated by, for example, its size (width or depth or thickness) or material composition, and the magnitude of the sensor disable current are selected to generate a sufficient amount of heat energy to rupture fuse section 216, thereby making sensor 101 permanently inoperable. As such, fuse section 216 disintegrates, burns up, or is otherwise destroyed such that the conductive trace of fuse section 216 is broken upon passage of a predetermined or sufficient amount of electrical current through it. The material and dimensions of fuse section 216 are chosen such that the amount of current required to break fuse section 216 is substantially greater than the normal expected current which may pass through fuse section 216 during normal operation of sensor 101. In certain embodiments, fuse section 216 is designed such that the amount of current required to break fuse section 216 is greater than, for example, twice the current associated with a maximum physiological analyte level measureable by sensor 101. In other embodiments, the current required to break fuse section 216 may be greater than two times the maximum current associate with normal sensor operation, such as three times, five times, ten times, 25 times, 50 times, 100 times or more. In certain

embodiments, the current required to break fuse section 216 is less than a current which may result in injury or damage to the user or the user's skin or damage to data processing unit 102 coupled to sensor 101. In certain embodiments, sensor 101 may include an isolation circuit such that when sensor disable circuit 215 is activated, the current to break fuse section 216 is isolated from the portions of sensor 101 positioned within the patient, such that the increased current will not injure the user.

[0054] In certain embodiments, sensor 101 may include a plurality of fuse sections 216 in order to provide redundant sensor disable features, such that the chance of fuse section 216 failing to break or otherwise render the sensor inoperable is decreased. In certain embodiments, analyte monitoring system 100 may check that sensor 101 was properly disabled after a sensor disable command is given. Such a check may include passing a signal across fuse section 216 to determine if fuse section 216 is broken or still connected, by for example, measuring the resistance across the fuse section 216, where a

measurement of a resistance above a predetermined threshold, such as 100 kilo ohm, 200 kilo ohm, 500 kilo ohm, or 1 mega ohm, indicates that the fuse section 216 is broken or blown. In the event the system determines the sensor disable function has failed, an additional sensor disable current may be passed across fuse section 216, wherein the additional current may be the same level of electrical current or may be an increased level of electrical current.

[0055] As mentioned above, while the sensor-disabling fuse section 216 in the illustrated embodiment of Fig. 2 is provided across guard contact 211 and counter electrode 213, other configurations may be used. For example, certain sensor embodiments may employ a temperature gauge thereon, such as in U.S. provisional application no. 61/497,821, entitled "Temperature-Compensated Analyte Monitoring Devices, Systems, and Methods Thereof and assigned to the assignee of the present application, the disclosure of which is incorporated herein by reference for all purposes. In certain embodiments, the

temperature gauge may include a thermocouple, and the thermocouple may be configured to provide the disabling fuse element or mechanism. For example, the thermocouple may consist of two thin conductive traces that meet at a junction, wherein the junction may be easily destroyed by a current pulse. In such embodiments, once the junction is destroyed and the thermocouple accordingly rendered inoperative, the sensor may cease to function without the operational temperature gauge.

[0056] In certain embodiments, the triggering of the sensor-disabling fuse may be

configured to be triggered by a user action either in lieu of, or as a secondary option to, the lapse of a predetermined time period. For example, sensor disable circuit 215 may be configured to disable sensor 101 upon decoupling of the control/electronics unit, including data processing unit 102, from sensor 101. Alternatively, or additionally, a user may be able to access a sensor disable function via a user interface or user input, such as a display and/or input buttons, in order to trigger a sensor disablement. The sensor disable function may be accessible via various components of analyte monitoring system 100, including, user input 202 of data processing unit 102, or via primary or secondary receivers 104, 106. In other embodiments, the sensor electronics may be configured to detect a defective sensor 101 as described herein and then automatically permanently disable the sensor using the sensor disable function. In other embodiments, the sensor-disabling fuse can be replaced by a sensor-disabling circuit breaker, which can be tripped by the sensor disable circuit in a similar manner as described above for the sensor-disabling fuse. For example, upon sensor expiration, the sensor disable circuit can send a trip current to the sensor- disabling circuit breaker that exceeds the current rating of the sensor-disabling circuit breaker, thereby tripping the sensor-disabling circuit breaker and rendering the sensor inoperable until the sensor-disabling circuit breaker is reset. In certain embodiments, the sensor-disabling circuit breaker may be a physical, electrical or logical switch.

[0057] In some embodiments, the sensor 101 is retracted or removed from the patient before the sensor disable circuit 215 is triggered and the fuse section 216 is broken or blown. This feature can reduce the chance of injury to the patient from the process of destroying the fuse section 216. In some embodiments, upon determination or detection of sensor 101 expiration, the sensor 101 can be permanently retracted into the housing, such as the housing for an on-body unit. In this situation, "permanently retracted" means that the sensor 101 cannot be instructed to be reinserted into the patient. In some

embodiments, permanently retracting the sensor 101 into the housing is sufficient to render the sensor 101 inoperable or unusable.

[0058] In certain embodiments, the sensor-disabling circuit may include an electronic circuit or device with similar functionality to a fuse or circuit breaker, such that, the electronic circuit or device may include an electronic switch configured to turn off when activated by a current, voltage, or other electronic signal. For example, the sensor- disabling circuit may include a relay which is "normally closed" (that is, the relay switch is in the closed position to complete an electrical circuit when no external signal is applied). Upon application of an external signal, i.e., a current, voltage, or other electrical signal, the switch changes to the "open" position, thus breaking the electrical circuit and indicating to the processor that the sensor is no longer active. In an alternative exemplary embodiment, the electronic circuit may include a relay that is "normally open", and when a signal is applied to the relay, the switch is changed to the "closed" position and shorts the electrical circuit, thus indicating to the processor that the sensor is no longer active. In certain embodiments, once the relay has been switched from its normal position, the relay cannot be switched back to its normal position.

[0059] In certain embodiments, the sensor-disabling circuit may record the status of the sensor and transmit the active or inactive status to the processor. In such embodiments, the processor is digitally informed of the status of the sensor, without reliance upon a completed electrical circuit. In such embodiments, upon expiration or deactivation of the sensor, the status monitored by the sensor-disabling circuit may be switched to a state to indicate that the sensor is no longer active and a digital signal may then be sent by the sensor-disabling circuit to the processor to indicate that the sensor is no longer active. In certain embodiments, the sensor-disabling circuit and processor may be configured such that until receipt of a digital signal indicating that the sensor is no longer active, the processor assumes the sensor is active, without receiving a continuous active/no longer active command. In alternative embodiments, the sensor-disabling circuit continuously or periodically informs the processor of the status of the sensor.

[0060] Fig. 3 is a block diagram of an embodiment of a receiver/monitor unit such as the primary receiver unit 104 of the data monitoring and management system of Fig. 1.

Primary receiver unit 104 includes one or more of: an analyte test strip interface 301, an RF receiver 302, an input 303, a temperature detection section 304, and a clock 305, each of which is operative ly coupled to a processing and storage section 307. Primary receiver unit 104 also includes a power supply 310 operatively coupled to a power conversion and monitoring section 308 which is also coupled to the receiver processor 307. Also shown are a receiver serial communication section 309 and an output 310, each operatively coupled to the processing and storage unit 307. Receiver unit 104 may also include user input and/or interface components or may be free of user input and/or interface components.

[0061] In embodiments for managing and monitoring a patient's blood glucose, test strip interface 301 includes a glucose level testing portion to receive a blood (or other body fluid sample) glucose test or information related thereto. For example, the interface may include a test strip port to receive a glucose test strip. The device may measure the glucose level of a sample provided on the test strip, and optionally display (or otherwise notify) the measured glucose level on output 310 of primary receiver unit 104. Any suitable test strip may be employed, e.g., test strips that only require a very small amount (e.g., one microliter or less, e.g., 0.5 microliter or less, e.g., 0.1 microliter or less), of applied sample to the strip in order to obtain accurate glucose information, e.g. FreeStyle® blood glucose test strips from Abbott Diabetes Care Inc. Glucose information obtained via the test strip and test strip interface 301 may be used for a variety of purposes, computations, etc. For example, the information may be used to calibrate sensor 101, confirm results of sensor 101 to increase the confidence thereof (e.g., in instances in which information obtained by sensor 101 is employed in therapy related decisions), etc. In certain embodiments, data processing unit 102 and/or primary receiver unit 104 and/or secondary receiver unit 106, and/or data processing terminal/infusion section 105 (Fig. 1) may be configured to receive the blood glucose value wirelessly over a communication link from, for example, an external blood glucose meter. In further embodiments, a user manipulating or using the analyte monitoring system 100 (Fig. 1) may manually input the blood glucose value using, for example, a user interface (for example, a keyboard, keypad, voice commands, and the like) incorporated in the one or more of data processing unit 102, primary receiver unit 104, secondary receiver unit 106, or data processing

terminal/infusion section 105.

[0062] Additional detailed description of the data management and monitoring system described above and its various components are provided in, for example, but not limited to, U.S. Patent 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 and 7,811,231, each of which is incorporated by reference herein for all purposes.

[0063] Sensors may be configured to require no system calibration or no user calibration. For example, a sensor may be factory calibrated and need not require further calibrating. In certain embodiments, calibration may be required, but may be done without user intervention, i.e., may be automatic. In those embodiments in which calibration by the user is required, the calibration may be according to a predetermined schedule or may be dynamic, i.e., the time for which may be determined by the system on a real-time basis according to various factors, such as but not limited to glucose concentration and/or temperature and/or rate of change of glucose, etc.

[0064] Calibration may be accomplished using an in vitro test strip (or other reference), e.g., a small sample test strip such as a test strip that requires less than about 1 microliter of sample (for example FreeStyle® blood glucose monitoring test strips from Abbott Diabetes Care). For example, test strips that require less than about 1 nanoliter of sample may be used. In certain embodiments, a sensor may be calibrated using only one sample of body fluid per calibration event. For example, a user need only lance a body part one time to obtain sample for a calibration event (e.g., for a test strip), or may lance more than one time within a short period of time if an insufficient volume of sample is firstly obtained. Embodiments include obtaining and using multiple samples of body fluid for a given calibration event, where glucose values of each sample are substantially similar. Data obtained from a given calibration event may be used independently to calibrate or combined with data obtained from previous calibration events, e.g., averaged including weighted averaged, etc., to calibrate. In certain embodiments, a system need only be calibrated once by a user, where recalibration of the system is not required.

[0065] Analyte systems may include an optional alarm system that, e.g., based on

information from a processor, warns the patient of a potentially detrimental condition of the analyte. For example, if glucose is the analyte, an alarm system may warn a user of conditions such as hypoglycemia and/or hyperglycemia and/or impending hypoglycemia, and/or impending hyperglycemia. An alarm system may be triggered when analyte levels approach, reach or exceed a threshold value. An alarm system may also, or alternatively, be activated when the rate of change, or acceleration of the rate of change, in analyte level increase or decrease approaches, reaches or exceeds a threshold rate or acceleration. A system may also include system alarms that notify a user of system information such as battery condition, calibration, sensor dislodgment, sensor malfunction, etc. Alarms may be, for example, auditory and/or visual. Other sensory-stimulating alarm systems may be used including alarm systems which heat, cool, vibrate, or produce a mild electrical shock when activated.

[0066] Certain embodiments of the present disclosure include an analyte sensor configured to measure a concentration of an analyte in a host, the sensor having a portion configured for contact with the analyte under a skin surface; an on body unit configured to operatively couple with a portion of the analyte sensor positionable above the skin surface, the on-body unit comprising a processor for processing analyte-related data received from the analyte sensor; and a sensor-disabling circuit coupled to the processor and a fuse provided on the portion of the analyte sensor positionable above the skin surface.

[0067] In certain embodiments, the sensor-disabling circuit may be configured to destroy the fuse and disable the sensor upon receipt of a sensor disable signal from the processor.

[0068] In certain embodiments, the processor may be configured to transmit the sensor disable signal upon lapse of a predetermined time period.

[0069] In certain embodiments, the predetermined time period may comprise the useful life of the sensor.

[0070] In certain embodiments, the processor may be configured to transmit the sensor disable signal upon expiration of the sensor. [0071] In certain embodiments, the processor may be configured to transmit the sensor disable signal upon decoupling of the on-body unit from the analyte sensor.

[0072] In certain embodiments, the fuse may comprise a conductive trace electrically coupled between two conductive contacts of the analyte sensor.

[0073] In certain embodiments, at least one of the conductive contacts of the analyte sensor may be a sensor electrode.

[0074] In certain embodiments, at least one of the conductive contacts of the analyte sensor may not be a sensor electrode.

[0075] In certain embodiments, the analyte sensor may comprise at least one working electrode, a reference electrode and a counter electrode, and wherein the counter electrode is electrically coupled to the fuse.

[0076] In certain embodiments, the on-body unit may comprise a sensor disable switch configured to electrically couple the two conductive contacts to a source of power to provide an electrical current to the fuse.

[0077] In certain embodiments, the fuse may be provided on a temperature gauge of the analyte sensor.

[0078] In certain embodiments, the temperature gauge may comprise a thermocouple, and wherein the thermocouple forms at least a portion of the fuse.

[0079] Certain embodiments of the present disclosure may include electronically coupling an on-body unit to a portion of the analyte sensor positioned above a skin surface; and transmitting an electrical current from the on-body unit to a fuse provided on the portion of the analyte sensor above the skin surface, the electrical current having a magnitude sufficient to destroy the fuse.

[0080] In certain embodiments, the electrical current may be transmitted after the lapse of a predetermined time period.

[0081] In certain embodiments, the predetermined time period may comprise the useful life of the sensor.

[0082] In certain embodiments, the electrical current may be transmitted upon expiration of the sensor.

[0083] In certain embodiments, the electrical current may be transmitted upon removal of the on-body unit from the analyte sensor.

[0084] In certain embodiments, the electrical current may be transmitted upon the on-body unit detecting a defect in the sensor. [0085] In certain embodiments, transmitting the electrical current may comprise transmitting a sensor disable signal from a processor to a sensor-disable switch and coupling the fuse to a power supply.

[0086] In certain embodiments, the fuse may comprise a conductive trace electrically coupled between two conductive contacts of the analyte sensor.

[0087] In certain embodiments, at least one of the conductive contacts of the analyte sensor may be a sensor electrode.

[0088] In certain embodiments, at least one of the conductive contacts of the analyte sensor may not be a sensor electrode.

[0089] In certain embodiments, the analyte sensor may comprise at least one working electrode, a reference electrode and a counter electrode, wherein the counter electrode is electrically coupled to the fuse.

[0090] The preceding merely illustrates the principles of the present disclosure. It will be appreciated that those skilled in the art will be able to devise various arrangements which, although not explicitly described or shown herein, embody the principles of the present disclosure and are included within its spirit and scope. Furthermore, all examples and conditional language recited herein are principally intended to aid the reader in understanding the principles of the present disclosure and the concepts contributed by the inventors to furthering the art, and are to be construed as being without limitation to such specifically recited examples and conditions. Moreover, all statements herein reciting principles, aspects, and embodiments of the present disclosure as well as specific examples thereof, are intended to encompass both structural and functional equivalents thereof. Additionally, it is intended that such equivalents include both currently known equivalents and equivalents developed in the future, i.e., any elements developed that perform the same function, regardless of structure. The scope of the present disclosure, therefore, is not intended to be limited to the exemplary embodiments shown and described herein. Rather, the scope and spirit of present disclosure is embodied by the appended claims.

Claims

What is claimed is:

1. A system for continuous measurement of an analyte in a host, the system comprising: an analyte sensor configured to measure a concentration of an analyte in a host, the sensor having a portion configured for contact with the analyte under a skin surface;

an on body unit configured to operatively couple with a portion of the analyte sensor positionable above the skin surface, the on-body unit comprising a processor for processing analyte-related data received from the analyte sensor; and

a sensor-disabling circuit coupled to the processor and a fuse provided on the portion of the analyte sensor positionable above the skin surface.

2. The system of claim 1, wherein the sensor-disabling circuit is configured to destroy the fuse and disable the sensor upon receipt of a sensor disable signal from the processor.

3. The system of claim 2, wherein the processor is configured to transmit the sensor disable signal upon lapse of a predetermined time period.

4. The system of claim 3, wherein the predetermined time period comprises the useful life of the sensor.

5. The system of claim 2, wherein the processor is configured to transmit the sensor disable signal upon expiration of the sensor.

6. The system of claim 2, wherein the processor is configured to transmit the sensor disable signal upon decoupling of the on-body unit from the analyte sensor.

7. The system of claim 1, wherein the fuse comprises a conductive trace electrically coupled between two conductive contacts of the analyte sensor.

8. The system of claim 7, wherein at least one of the conductive contacts of the analyte sensor is a sensor electrode.

9. The system of claim 8, wherein at least one of the conductive contacts of the analyte sensor is not a sensor electrode.

10. The system of claim 7, wherein the analyte sensor comprises at least one working electrode, a reference electrode and a counter electrode, and wherein the counter electrode is electrically coupled to the fuse.

11. The system of claim 7, wherein the on-body unit comprises a sensor disable switch configured to electrically couple the two conductive contacts to a source of power to provide an electrical current to the fuse.

12. The system of claim 1, wherein the fuse is provided on a temperature gauge of the analyte sensor.

13. The system of claim 12, wherein the temperature gauge comprises a thermocouple, and wherein the thermocouple forms at least a portion of the fuse.

14. A method for disabling an analyte sensor, the method comprising:

electronically coupling an on-body unit to a portion of the analyte sensor positioned above a skin surface; and

transmitting an electrical current from the on-body unit to a fuse provided on the portion of the analyte sensor above the skin surface, the electrical current having a magnitude sufficient to destroy the fuse.

15. The method of claim 14, wherein the electrical current is transmitted after the lapse of a predetermined time period.

16. The method of claim 15, wherein the predetermined time period comprises the useful life of the sensor.

17. The method of claim 14, wherein the electrical current is transmitted upon expiration of the sensor.

18. The method of claim 14, wherein the electrical current is transmitted upon removal of the on-body unit from the analyte sensor.

19. The method of claim 14, wherein the electrical current is transmitted upon the on- body unit detecting a defect in the sensor.

20. The method of claim 14, wherein transmitting the electrical current comprises transmitting a sensor disable signal from a processor to a sensor-disable switch and coupling the fuse to a power supply.

21. The method of claim 14, wherein the fuse comprises a conductive trace electrically coupled between two conductive contacts of the analyte sensor.

22. The method of claim 21, wherein at least one of the conductive contacts of the analyte sensor is a sensor electrode.

23. The method of claim 22, wherein at least one of the conductive contacts of the analyte sensor is not a sensor electrode.

24. The method of claim 21, wherein the analyte sensor comprises at least one working electrode, a reference electrode and a counter electrode, wherein the counter electrode is electrically coupled to the fuse.