Aptamer sensor interference-correction algorithms

Abstract

Examples are directed to analyte sensor systems and methods of use thereof. An analyte sensor system may include an electrochemical aptamer-based biosensor configured for use in sensing a target analyte. The biosensor may include a substrate, a reversible redox probe, and an aptamer. The system may include sensor electronics configured to perform operations. The operations may include interrogating the biosensor to determine a current response, determining an adjusted current value to correct for at least one of pH or temperature, and determining an estimated analyte value for the target analyte based on the adjusted current value.

Description

Atty. Dkt. No. 4855.147WO1 Client Reference No. 0975PCT01APTAMER SENSOR INTERFERENCE-CORRECTION ALGORITHMSCLAIM OF PRIORITY

[0001] This application claims the benefit of U.S. Provisional Application No. 63 / 738,202, filed on December 23, 2024, which is hereby incorporated by reference in its entirety.BACKGROUND

[0002] Biosensors may be used to sense analytes. An analyte may be a substance or chemical constituent in a biological fluid that can be analyzed. For example, analytes may be analyzed in blood, interstitial fluid, cerebral spinal fluid, lymph fluid, urine, sweat, saliva, and the like. Analytes may include naturally occurring substances, artificial substances, drugs, toxins, metabolites, and / or reaction products.

[0003] Aptamer biosensors are a class of affinity biosensors in which an aptamer (single stranded DNA / RNA) functions as a recognition element. The aptamer has a specific affinity to the analyte. Aptamers may be developed and used to recognize target molecules such as, but not limited to, viruses, bacteria, cancer, proteins and nucleic acids. For example, aptamers may be developed to recognize analytes such as troponin, BNP, insulin, GLP-1, dopamine, serotonin, L-DOPA, vancomycin, aminoglycosides, doxorubicin, cortisol, and Luteinizing Hormone. An aptamer may be an oligonucleotide or a peptide that binds to a biological analyte. Oligonucleotide aptamers include nucleic acid species that have been engineered through repeated rounds of in vitro selection or equivalently, SELEX (systematic evolution of ligands by exponential enrichment) to bind to biological analytes such as small molecules, proteins, nucleic acids, cells, tissues and organisms. Peptide aptamers include polypeptides selected or engineered to bind an analyte.

[0004] Regardless of the specific aptamer used as a recognition element in the biosensor, the interaction between the analyte and the aptamerAtty. Dkt. No. 4855.147WO1 Client Reference No. 0975PCT01induces a measurable transduced signal that may be used to detect the analyte and may be used to determine an estimated analyte value. The biosensor may be designed to induce an optical (e.g., fluorescence or colorimetric) or an electrical signal. For example, an electrochemical aptamer-based sensor system may include a substrate, a reversible redox probe, and an aptamer, where the aptamer conformally changes (e.g., changes form to different shapes) upon binding with a target analyte to change an electron transfer rate between the redox probe and the substrate. This change in the electron transfer rate induces a measurable signal that may be used to determine an estimated analy te value.

[0005] It is desirable to accurately detect analyte concentrations from the transduced signal.SUMMARY

[0006] This present application discloses, among other things, systems, devices, and methods related to analyte biosensors, including, for example, providing corrections accounting for dynamically-changing environmental conditions.

[0007] Example 1 is an analyte sensor system including an electrochemical aptamer-based biosensor configured for use in sensing a target analyte. The biosensor may include a substrate, a reversible redox probe, and an aptamer. The sy stem may include sensor electronics configured to perform operations. The operations may include interrogating the biosensor to determine a current response, determining an adjusted current value to correct for at least one of pH or temperature, and determining an estimated analyte value for the target analyte based on the adjusted current value.

[0008] In Example 2, the subject matter of Example 1 optionally includes the aptamer is configured to change upon binding with a target analyte to change an electron transfer rate between the redox probe and the substrate.

[0009] In Example 3, the subject matter of any one or more of Examples 1-2 optionally includes the determining the adjusted current value includes receiving a temperature signal indicative of a temperature measurementAtty. Dkt. No. 4855.147WO1 Client Reference No. 0975PCT01and determining a temperature-corrected current value based on the temperature signal.

[0010] In Example 4, the subject matter of any one or more of Examples 1-3 optionally includes the determining the adjusted current value includes receiving a pH signal indicative of a pH measurement and determining a pH-corrected current value based on the pH signal.

[0011] In Example 5, the subject matter of any one or more of Examples 1-4 optionally includes the interrogating the biosensor further includes applying an electrical stimulus the biosensor and measuring an electrical response to the electrical stimulus, and the determining the adjusted current value includes inferring a pH measurement from the electrical response.

[0012] In Example 6, the subject matter of Example 5 optionally includes the biosensor includes a working electrode, the applying the electrical stimulus to the biosensor includes applying a voltage profile to the working electrode as a function of time, and the electrical response includes an electrical response to the applied voltage profile.

[0013] In Example 7. the subject matter of Example 6 optionally includes the biosensor is interrogated by applying the voltage profile using a voltammetry technique, the electrical response to the voltage profile includes a peak voltage measure, and the pH measurement is inferred using at least the peak voltage measure.

[0014] In Example 8, the subject matter of Example 7 optionally includes the electrical response to the voltage profile further includes a peak current measure, the sensor electronics are configured to determine the adjusted current value based on the peak voltage measure and the current response, and an estimated analyte value for the target analyte is determined based on the adjusted current value.

[0015] In Example 9. the subject matter of any one or more of Examples 5-8 optionally includes the biosensor includes a working electrode and a reference electrode, the electrical stimulus applied to the biosensor includes applying an open-circuit potential between working and reference electrodes of the biosensor, and the electrical response includes anAtty. Dkt. No. 4855.147WO1 Client Reference No. 0975PCT01electrical response to the open-circuit potential, and the pH measurement is inferred using the open-circuit potential.

[0016] In Example 10, the subject matter of any one or more of Examples 1-9 optionally includes the adjusted current value is determined to correct for both pH and temperature.

[0017] In Example 11, the subject matter of any one or more of Examples I-10 optionally includes the interrogating the biosensor includes applying a voltammetry technique, determining both a raw peak current and a raw peak voltage for the applied voltammetry technique, and the determining the adjusted current value includes determining a current correction factor based on the raw peak voltage, and determining the adjusted current value based on the raw peak current and the current correction factor.

[0018] In Example 12, the subject matter of Example 11 optionally includes the current correction factor is determined using the raw peak voltage.

[0019] In Example 13, the subject matter of any one or more of Examples II-12 optionally includes regression analysis is applied to at least one of bench data or in vivo data to determine the current correction factor for the raw peak voltage.

[0020] In Example 14, the subject matter of any one or more of Examples 11-13 optionally includes the current correction factor is determined using a linear function.

[0021] In Example 15, the subject matter of any one or more of Examples 11-13 optionally includes the current correction factor is determined using a nonlinear function.

[0022] In Example 16, the subject matter of any one or more of Examples 11-13 optionally includes the current correction factor is determined using a piecewise function.

[0023] In Example 17, the subject matter of any one or more of Examples 11-13 optionally includes the adjusted current value is determined using a lookup table to look up the current correction factor based on the raw peak voltage.Atty. Dkt. No. 4855.147WO1 Client Reference No. 0975PCT01

[0024] In Example 18, the subject matter of Example 17 optionally includes the adjusted current value is determined using a lookup table to look up the current correction factor based on the raw peak current, the raw peak voltage and a temperature.

[0025] In Example 19, the subject matter of any one or more of Examples 1-18 optionally includes the interrogating the biosensor includes applying a voltammetry technique, determining both a raw peak current and a raw peak voltage for the applied voltammetry technique. The determining the adjusted current value may include receiving a temperature signal from a temperature sensor, determining a temperature-corrected peak current using the temperature signal and the raw peak current, determining a temperature-corrected peak voltage using the temperature signal and the raw peak voltage, determining a current correction factor based on the temperature-corrected peak voltage, and determining the adjusted current value using the temperature-corrected peak current and the current correction factor.

[0026] In Example 20, the subject matter of Example 19 optionally includes the current correction factor is determined using a peak currentvoltage correlation.

[0027] In Example 21, the subject matter of any one or more of Examples 19-20 optionally includes normalizing the temperature-corrected peak current to provide a normalized peak current. The adjusted current value may be determined using the normalized peak current and the current correction factor.

[0028] Example 22 is a method of determining an in vivo concentration of an analyte. The method may include contacting, in vivo, a biological fluid comprising an analyte with an aptamer from an electrochemical aptamerbased biosensor and interrogating the biosensor using voltammetry to determine biosensor responses. The biosensor responses may include both a current response and a voltage response. The method may include determining an adjusted current value based on the current response and the voltage response, and determining an estimated analyte value for the analyte based on the adjusted current value.Atty. Dkt. No. 4855.147WO1 Client Reference No. 0975PCT01

[0029] In Example 23, the subject matter of Example 22 optionally includes the aptamer changes upon binding with a target analyte to change an electron transfer rate between a redox probe and a substrate.

[0030] In Example 24, the subject matter of any one or more of Examples 22-23 optionally includes the determining the adjusted current value includes receiving a temperature signal indicative of a temperature measurement and determining a temperature-corrected current value based on the temperature signal.

[0031] In Example 25, the subject matter of any one or more of Examples 22-24 optionally includes the determining the adjusted current value includes receiving a pH signal indicative of a pH measurement and determining a pH-corrected current value based on the pH signal.

[0032] In Example 26, the subject matter of any one or more of Examples 22-25 optionally includes the interrogating the biosensor further includes applying an electrical stimulus the biosensor and measuring an electrical response to the electrical stimulus, and the determining the adjusted current value includes inferring a pH measurement from the electrical response.

[0033] In Example 27, the subject matter of Example 26 optionally includes the applying the electrical stimulus to the biosensor includes applying a voltage profile to a working electrode of the biosensor as a function of time, and the electrical response includes an electrical response to the applied voltage profile.

[0034] In Example 28, the subject matter of Example 27 optionally includes the interrogating the biosensor includes applying the voltage profile using a voltammetry technique, the electrical response to the voltage profile includes a peak voltage measure, and the pH measurement is inferred using at least the peak voltage measure.

[0035] In Example 29, the subject matter of any one or more of Examples 27-28 optionally includes the measuring the electrical response includes measuring a peak current, and the determining the adjusted current value includes using a peak voltage measure and the current response. AnAtty. Dkt. No. 4855.147WO1 Client Reference No. 0975PCT01estimated analyte value for the analyte may be determined based on the adjusted current value.

[0036] In Example 30, the subject matter of any one or more of Examples 26-29 optionally includes the applying the electrical stimulus applied to the biosensor includes applying an open-circuit potential between a working electrode and a reference electrode of the biosensor, and the electrical response includes an electrical response to the open-circuit potential, and the pH measurement is inferred using the open-circuit potential.

[0037] In Example 31, the subject matter of any one or more of Examples 22-30 optionally includes the adjusted current value is determined to correct for both pH and temperature.

[0038] In Example 32, the subject matter of any one or more of Examples 22-31 optionally includes the interrogating the biosensor includes applying a voltammetry7technique, determining both a raw peak current and a raw peak voltage for the applied voltammetry technique. The determining the adjusted current value may include determining a current correction factor based on the raw peak voltage, and determining the adjusted current value based on the raw peak current and the current correction factor.

[0039] In Example 33, the subject matter of Example 32 optionally includes the determining the adjusted current value includes using the raw peak voltage to determine a function, and determining the adjusted current value using the raw peak current and the function.

[0040] In Example 34, the subject matter of Example 33 optionally includes applying regression analysis to at least one of bench data or in vivo data to determine the function.

[0041] In Example 35, the subject matter of Example 33 optionally includes the function includes a linear function.

[0042] In Example 36, the subject matter of Example 33 optionally includes the function includes a nonlinear function.

[0043] In Example 37, the subject matter of Example 33 the function includes a piecewise function.

[0044] In Example 38, the subject matter of Example 32 optionally includes the determining the adjusted current value includes using at leastAtty. Dkt. No. 4855.147WO1 Client Reference No. 0975PCT01one lookup table to determine the adjusted current values based on both the raw peak current and the raw peak voltage.

[0045] In Example 39, the subject matter of Example 38 optionally includes the determining the adjusted current value includes using at least one lookup table to determine the adjusted current values based on the raw peak current, the raw peak voltage and a temperature.

[0046] In Example 40, the subject matter of any one or more of Examples 22-39 optionally includes the interrogating the biosensor includes applying a voltammetry technique, the current response includes a raw peak current for the applied voltammetry technique and the voltage response includes a raw peak voltage for the applied voltammetry7technique. The determining the adjusted current value may include receiving a temperature signal from a temperature sensor, determining a temperature-corrected peak current using the temperature signal and the raw peak current, determining a temperature-corrected peak voltage using the temperature signal and the raw peak voltage, determining a current correction factor based on the temperature-corrected peak voltage, and determining the adjusted current value using the temperature-corrected peak current and the current correction factor.

[0047] In Example 41, the subject matter of Example 40 optionally includes the current correction factor is determined using a peak currentvoltage correlation.

[0048] In Example 42, the subject matter of any one or more of Examples 40-41 optionally includes normalizing the temperature-corrected peak current to provide a normalized peak current. The adjusted current value may be determined using the normalized peak current and the current correction factor.

[0049] Example 43 is a non-transitory computer readable medium storing instructions, which when executed by at least one data processor, result in operations. The operations may include interrogating an electrochemical aptamer-based biosensor using voltammetry to determine biosensor responses. An aptamer of the biosensor may contact, in vivo, a biological fluid comprising an analyte, and the biosensor responses may include bothAtty. Dkt. No. 4855.147WO1 Client Reference No. 0975PCT01a current response and a voltage response. The method may further include determining an adjusted current value based on the current response and the voltage response, and determining an estimated analyte value for the analyte based on the adjusted current value.

[0050] In Example 44, the subject matter of Example 43 further may include operations that perform methods recited in any of claims 23 to 42.

[0051] This summary is intended to provide an overview of subject matter of the present patent application. It is not intended to provide an exclusive or exhaustive explanation of the disclosure. The detailed description is included to provide further information about the present patent application. Other aspects of the disclosure will be apparent to persons skilled in the art upon reading and understanding the following detailed description and viewing the drawings that form a part thereof, each of which are not to be taken in a limiting sense.BRIEF DESCRIPTION OF THE DRAWINGS

[0052] In the drawings, which are not necessarily drawn to scale, like numerals may describe similar components in different views. Like numerals having different letter suffixes may represent different instances of similar components. The drawings illustrate generally, by way of example, but not by way of limitation, various embodiments described in the present document.

[0053] FIG. 1 illustrates, by way of example and not limitation, an environment including an analyte sensor system.

[0054] FIG. 2 illustrates, by way of example and not limitation, an analyte sensor system, which may for example, be the system shown in FIG. 1.

[0055] FIG. 3 illustrates, by way of example and not limitation, a medical device system including the analyte sensor system of FIG. 1.

[0056] FIGS. 4A-4B illustrate, by way of example and not limitation, some analyte sensor embodiments.

[0057] FIG. 5 illustrates, by way of example and not limitation, an aptamer biosensor for monitoring at least one analyte.Atty. Dkt. No. 4855.147WO1 Client Reference No. 0975PCT01

[0058] FIG. 6 illustrates, by way of example and not limitation, an aptamer biosensor for continuous in vivo use in a subject.

[0059] FIGS. 7A-7B illustrate by way of example and not limitation, detections of analytes using an enzy matic amperometric sensor and an aptamer sensor, respectively.

[0060] FIG. 8 illustrates, by way of example and not limitation, an interrogation output for an aptamer biosensor, and more particularly illustrates current and voltage outputs from square wave voltammetry.

[0061] FIGS. 9A-9B illustrate, by way of example and not limitation, some methods for determining an analyte value using an aptamer biosensor.

[0062] FIG. 10 illustrates another example of a method for determining an analyte value to correct for both temperature and pH.

[0063] FIG. 11 illustrates, by way of example and not limitation, an interrogation output for another aptamer biosensor, and more particularly illustrates current and voltage outputs from square wave voltammetry.

[0064] FIGS. 12A and 12B illustrate, by way of example and not limitation, peak voltage and normalized peak current from square wave voltammetry, over a period of 150 minutes with changing pH.

[0065] FIG. 13A and FIG. 13B illustrate, by way of example and not limitation, plots of peak voltage and peak current, respectively over about 120 minutes for four sensors (SI, S2, S3. S4), where the pH changes from 7.4 to 6.5 with a finer resolution than shown in FIGS. 12A-12B.

[0066] FIGS. 14A and 14B illustrate for one sensor and four sensors, by way of example and not limitation, respectively, plots of a peak current (nA) over peak voltage (V).

[0067] FIG. 15 is a similar plot to FIG. 14B, illustrating a plot of normalized peak current over peak voltage (V), which also suggest that a quadratic equation may correspond to the peak current and peak voltage variations over the range of pH values.

[0068] FIGS. 16A and 16B illustrate plots of peak voltage (V) and peak current (nA), respectively, for four sensors (SI, S2, S3, S4), by way ofAtty. Dkt. No. 4855.147WO1 Client Reference No. 0975PCT01example and not limitation, where the temperature ranges between 35 °C to 25°C over 250 minutes.

[0069] FIG. 17A illustrates a plot of peak current over peak voltage for one sensor for the test where the temperature ranges between 35°C to 25°C. FIG. 17B illustrates a plot of peak current over peak voltage for four sensors for the test, and FIG. 17C illustrates a plot of a normalized peak current over peak voltage for four sensors for the test, by way of examples and not limitation.

[0070] FIG. 18A illustrates the raw peak current and raw peak voltage and FIG. 18B illustrates the corrected peak current along with an indicator of when an analyte is infused (vancomycin), by way of example and not limitation.

[0071] FIG. 19 illustrates, by way of example and not limitation, a computing device hardware architecture, within which a set or sequence of instructions can be executed to cause a machine to perform examples of any one of the methodologies discussed herein.DETAILED DESCRIPTION

[0072] Various examples described herein are directed to sensor systems and methods that use aptamer biosensors to detect analytes. A sensor system may include an aptamer biosensor that is placed in contact with a bodily fluid of a host to detect or measure a concentration of at least one analyte in the bodily fluid. In some examples, the aptamer biosensor is inserted into the host to contact the bodily fluid in vivo. In some examples, the aptamer biosensor is inserted subcutaneously to contact interstitial fluid below the host's skin.

[0073] The sensor system may measure an analyte binding event by interrogating the aptamer biosensor. For example, the system may interrogate the aptamer biosensor by applying an electrical stimulus to the biosensor and measuring an electrical response to the electrical stimulus. By way of example and not limitation, voltammetry may be used to track an electron transfer rate of a redox probe. Voltammetry is a technique that may be used to analyze electrochemical systems by applying a voltage toAtty. Dkt. No. 4855.147WO1 Client Reference No. 0975PCT01the system, changing a voltage as a function of time, and measuring the resulting current. Voltametric techniques may include square wave voltammetry, differential pulse voltammetry or alternating current voltammetery. Square wave voltammetry is used herein as a specific example. Other voltammetry' examples include, but are not limited to, pulse voltammetry, linear sweep voltammetery’, and cyclic voltammetry.

[0074] As previously7mentioned, the biosensor may be designed with an aptamer that conformally changes upon binding with target analyte, which causes a change in an electron transfer rate between a redox problem and a substrate. However, if an aptamer biosensor is designed to transduce a signal based on a changed electron transfer rate, then the aptamer biosensor may be very7sensitive to environmental changes that are capable of altering the electron transfer in a way that is not related to analytespecific binding to the aptamer.

[0075] For example, the analyte sensor system may be configured to be deployed to monitor analyte(s) in interstitial fluid, and the wound in which the sensor is deployed may experience significant changes in temperature and / or pH. A pH number provides a measure of acidity or alkalinity of a solution. A recent pre-clinical study in the context of subdermal interstitial fluid monitoring indicated that some signal variation may be caused by changes in temperature and / or pH. Such dynamic changes in temperature and / or pH may affect the electron transfer rate. It is also noted that environmental factors other than temperature and pH may affect the electron transfer rate and thus adversely affect a readout (e.g., voltammetry7readout) from the aptamer sensor system. For example, ionic strength, divalent cation concentration, sample viscosities, and the like may affect the readout.

[0076] Possible techniques to address the effects of environmental changes include sensor calibration or sensor design modifications. For example, sensors may be calibrated in a matrix, but such calibration is not able to handle dynamically vary ing conditions. Further, there are challenges to modify an aptamer biosensor to have a pH-insensitive redox probe.Atty. Dkt. No. 4855.147WO1 Client Reference No. 0975PCT01

[0077] Monitoring and accounting for such conditions and environmental factors can be complex, and result in increased computing requirements associated with processing such conditions. Further, processing a large quantity of data associated with monitoring and accounting for such conditions and environmental factors can also be slow and inefficient while requiring significant computing resources. Thus, because existing systems do not account for those conditions and environmental factors, and may be inefficient in processing and monitoring such a large quantity of data associated with accounting for those conditions and environmental factors, estimated analyte concentration values produced using certain existing aptamer biosensor systems may not achieve the desired level of accuracy and / or performance.

[0078] Various embodiments of the present subject matter improve aptamer sensor performance by compensating for environmental changes. In particular, various embodiments use algorithmic approaches to compensate for changes to temperature, compensate for changes to pH, or compensate for changes to both temperature and pH. Thus, the overall accuracy of the aptamer biosensors may be improved without in an efficient manner. The algorithmic approaches may additionally and / or alternatively reduce the required computing resources and / or increase the processing speed associated with monitoring and / or processing a data to effectively correct for environmental factors. The algorithmic approaches to apply a correction to raw aptamer sensor signals may be based on temperature measurements, on direct pH measurements; on an inferred pH from peak voltage determined from the interrogation of the biosensor (e.g., SWV) where the peak voltage is a function of pH; and / or on an inferred pH determined from open-circuit potential (OCP) measurements between the aptamer working electrode and reference electrode. The raw aptamer sensor signal from the interrogated biosensor may be a raw peak current from square voltammetry7.

[0079] For example, algorithmic approach(es) may be used to correct for temperature changes, as the electron transfer rate of the redox probe, and potentially the aptamer-analyte binding kinetics, is a strong function of temperature. Both the baseline for the outputted signal and the sensor'sAtty. Dkt. No. 4855.147WO1 Client Reference No. 0975PCT01response to analyte-specific binding to the aptamer are functions of temperature. Various embodiments of the present subject matter may sense temperature and apply an algorithmic correction based on the sensed temperature.

[0080] Additionally, or alternatively, algorithmic approach(s) may be used to correct for pH changes. Various embodiments of the present subject matter may directly measure pH in the wound, and apply an algorithmic correction based on the measured pH. For example, a pH sensor such as a potentiometric-based pH sensor may be used to measure pH in the wound pocket. The measured pH value can be used to correct aptamer sensor readout. However, the inclusion of a pH sensor may cause the design and development of the system to be more complex, which can make the system more expensive or more difficult to operate or maintain. Thus, various embodiments of the present subject matter may infer pH from the interrogation of the aptamer sensor, i.e. from the measured electrical response to the electrical stimulus. Various examples may infer pH from an open-circuit potential between the reference and working electrode and / or infer pH from the peak voltage from square wave voltammetry. Based on benchtop data, both SWV peak height and peak voltage have been determined to be functions of surrounding pH. By leveraging the readily available peak voltage information, corrections may be performed for pH-induced variation. For example, the pH correction may be based on the raw peak current and the raw peak voltage from the square wave voltammetry interrogation and based on the reference voltage. For example, the peak voltage corresponds to pH, and therefore may be used to determine a correction that accounts for the pH change for the peak current. The corrected peak current from the square wave voltammetry¬ may be used to determine the estimated analyte value.

[0081] FIG. 1 illustrates, by way of example and not limitation, an example of an environment 100 including an analyte sensor system 102. The analyte sensor system 102 is coupled to a host 101, which may be a human patient. In some examples, the host is subject to a temporary or permanent health condition that makes analyte monitoring useful.Atty. Dkt. No. 4855.147WO1 Client Reference No. 0975PCT01

[0082] The analyte sensor system 102 includes an aptamer biosensor 104 configured to sense one or more analytes. The aptamer biosensor 104 can be exposed to analyte at the host 101 in any suitable way. In some examples, the aptamer biosensor 104 is fully implantable under the skin of the host 101. In other examples, the aptamer biosensor 104 is wearable on the body of the host 101 (e.g.. on the body but not under the skin). Also, in some examples, the analyte sensor 104 is a transcutaneous device (e.g., with a sensor residing at least partially under or in the skin of a host). The devices and methods described herein can be applied to any device capable of detecting a concentration of an analyte and providing an output signal that represents the concentration of the analyte.

[0083] In the example of FIG. 1, the analyte sensor system 102 also includes sensor electronics 106. In some examples, the sensor electronics 106 and aptamer biosensor 104 are provided in a single integrated enclosure. In other examples, the aptamer biosensor 104 and sensor electronics 106 are provided as separate components or modules. For example, the analyte sensor system 102 may include a disposable (e.g., single-use) sensor mounting unit that may include the aptamer biosensor 104, a component for attaching the sensor 104 to a host (e.g., an adhesive pad), and / or a mounting structure configured to receive a sensor electronics unit including some or all of the sensor electronics 106 shown in FIGS. 2 and 3. The sensor electronics 106 may be reusable.

[0084] The sensor electronics 106 may be configured to process sensor information and generate transformed sensor information. The sensor electronics 106 may include circuitry used to measure and process data from the aptamer biosensor 104, including implement algorithms associated with processing and calibration of continuous sensor data. The aptamer biosensor may include hardware, firmware, and / or software that enables analyte level measurement. For example, the sensor electronics 106 may include a potentiostat, a power source, other components useful for signal processing and data storage, and a telemetry module for transmitting data from itself to one or more display devices. At least part of the sensor electronics 106 may be affixed to a printed circuit board (PCB), or the like, and may include an integrated circuit (IC) such as anAtty. Dkt. No. 4855.147WO1 Client Reference No. 0975PCT01Application-Specific Integrated Circuit (ASIC), an electrochemical analog front end. a microcontroller, and / or a processor. The electrochemical analog front end may be configured with a sequencer or waveform synthesizer to create the appropriate waveforms for interrogating the aptamer biosensor to transduce the signal from the aptamer biosensor. Examples of such waveforms, which may be used to analyze electrochemical systems, include square wave voltammetry, linear sweep voltammetry, cyclic voltammetry, differential pulse voltammetry, AC voltammetry, pulse voltammetry, staircase voltammetry', normal pulse voltammetry, chronoamperometry, and chronocoulometry.

[0085] The aptamer biosensor 104 may use any known method, including invasive, minimally-invasive, or non-invasive sensing techniques that use an aptamer to provide a raw sensor output indicative of the concentration of the analyte in the host 101. For example, amperometric, impedimetric or square-wave voltammetry may be used to detect and measure the targeted analyte. The raw sensor output may be converted or transformed into calibrated and / or filtered analyte concentration data used to provide a useful value of the analyte concentration to a user, such as the host or a caretaker (e.g., a parent, a relative, a guardian, a teacher, a doctor, a nurse, or any other individual that has an interest in the wellbeing of the host 101). The sensor electronics 106 may be used to convert or transform the raw sensor output, which may include applying algorithmic approaches to correct for temperature changes and / or pH changes.

[0086] The environment 100 may include one or more other devices. For example, the environment 100 may include external device(s) such as, for example, a medical device 108. The medical device 108 may be or include a display device and / or a drug delivery device such as an insulin pump or an insulin pen. The display device(s) may be configured for, among other things, displaying the concentration of the analyte. For example, the analyte sensor may wirelessly communicate with the display device(s). The display device(s) may include a display such as a touch screen and / or may include other user interfaces such as but not limited to voice interfaces. By way of example and not limitation, the display device(s) may include a handheld device such as a mobile phone, tablet, smart watch, medicamentAtty. Dkt. No. 4855.147WO1 Client Reference No. 0975PCT01delivery' device, monitor such as a blood glucose meter, and / or a desktop or laptop computer. The medical device 108 may be wearable, e.g., on a watch, glasses, contact lens, patch, wristband, ankle band, or another wearable item, or may be incorporated into a handheld device (e.g., a smartphone). In some examples, the medical device 108 includes a multisensor patch that may, for example, detect one or more of analyte levels, heart rate, blood pressure, respiration (e.g., using impedance), activity (e g., using an accelerometer), posture (e.g., using an accelerometer), galvanic skin response, tissue fluid levels (e.g., using impedance or pressure).

[0087] In some examples, the medical device 108 includes one or more sensors, such as another analyte sensor, a blood pressure sensor, a heart rate sensor, a respiration sensor, a motion sensor (e.g., accelerometer), posture sensor (e.g., 3-axis accelerometer), acoustic sensor (e.g.. to capture ambient sound or sounds inside the body), or a core temperature sensor.

[0088] In some examples, the analyte sensor system 102 and the medical device 108 communicate with one another. Communication between the analyte sensor system 102 and medical device 108 may occur over any suitable wired connection and / or via a wireless communication signal 110. For example, the analyte sensor system 102 (e g., the sensor electronics 106 thereof) may be configured to establish a communication connection with the medical device 108 using a suitable short-range communications medium such as, for example, a radio frequency medium (e.g., Bluetooth, Medical Implant Communication System (MICS), Wi-Fi, near field communication (NFC), radio frequency identification (RFID), Zigbee, Z- Wave or other communication protocols), an optical medium (e.g.. infrared), a sonic medium (e.g., ultrasonic), a cellular protocol -based medium (e.g., Code Division Multiple Access (CDMA) or Global System for Mobiles (GSM)), and / or the like.

[0089] In some examples, the environment 100 may include a wearable sensor 130. The wearable sensor 130 may include a sensor circuit (e.g., a sensor circuit configured to detect an analyte concentration) and a communication circuit, which may. for example, be an NFC circuit. InAtty. Dkt. No. 4855.147WO1 Client Reference No. 0975PCT01some examples, information from the wearable sensor 130 may be retrieved from the wearable sensor 130 using a user computing device 132, such as a smart phone, that is configured to communicate with the wearable sensor 130 via the wearable sensor’s communication circuit, for example, when the user device 132 is placed near the wearable sensor 130. For example, swiping the user device 132 over the sensor 130 may retrieve sensor data from the wearable sensor 130 using NFC or other suitable wireless communication. The use of NFC communication may reduce power consumption by the wearable sensor 130, which may reduce the size of a power source (e.g., battery or capacitor) in the wearable sensor 130 or extend the usable life of the power source. In some examples, the wearable sensor 130 may be wearable on an upper arm as shown. In some examples, a wearable sensor 130 may additionally or alternatively be on the upper torso of the patient (e.g., over the heart or over a lung), which may, for example, facilitate detecting heart rate, respiration, or posture. A wearable sensor 136 may also be on the lower body (e.g., on a leg) or other part of the body (e.g., on the abdomen).

[0090] In some examples, an array or network of sensors may be associated with the patient. For example, at least one analyte sensor system 102, and / or external devices, such as the medical device 108, wearable device 120 such as a watch, an additional wearable sensor 130 and / or the like, may communicate with one another via a short-range communication medium (e.g., Bluetooth, MICS, NFC, or any of the other options described above). The additional wearable sensor 130 may be any of the examples described above with respect to medical device 108. The analyte sensor system 102, medical device 108, and additional sensor 130 on the host 101 are provided for illustration and description and are not necessarily drawn to scale.

[0091] The environment 100 may include a hand-held smart device (e.g.. smart phone) 112, tablet 114, smart pen 116 (e.g., insulin delivery pen with processing and communication capability), computer 118, a wearable device 120 such as a watch, or peripheral medical device 122, any of which may communicate with the analyte sensor system 102 via a short- range communication medium, such as indicated by wirelessAtty. Dkt. No. 4855.147WO1 Client Reference No. 0975PCT01communication signal 110, and may also communicate over a network 124 with a server system (e.g.. remote data center) or with a remote terminal 128 to facilitate communication with a remote user (not shown) such as a technical support staff member or a clinician. The wearable device 120 may include, but is not limited to, one or more activity7sensors, a heart rate monitor (e.g., light-based sensor or electrode-based sensor), blood pressure sensor, a respiration sensor (e.g., acoustic- or electrode-based), a location sensor (e.g., GPS), or other sensors.

[0092] In some examples, the environment 100 includes a server system 126. The server system 126 can include one or more computing devices, such as one or more server computing devices. In some examples, the server system 126 is used to collect analyte data from the analyte sensor system 102 and / or analyte or other data from the plurality of other devices, and to perform analytics on collected data, generate, or apply universal or individualized models for analyte levels, and communicate such analytics, models, or information based thereon back to one or more of the devices in the environment 100. In some examples, the server system 126 gathers inter-host and / or intra-host break-in data to generate one or more break-in characteristics, as described herein.

[0093] The environment 100 may also include a wireless access point (WAP) 138 used to communicatively couple one or more of analyte sensor system 102, network 124, server system 126, medical device 108 or any of the peripheral devices described above. For example, WAP 138 may provide Wi-Fi and / or cellular connectivity7within environment 100. Other communication protocols, such as NFC or Bluetooth, may also be used among devices of the environment 100.

[0094] FIG. 2 illustrates, by way of example and not limitation, an analyte sensor system 200, which may for example, be the system 102 shown in FIG. 1. The analyte sensor system may include an aptamer biosensor 202 configured to measure one or more analytes. The analyte sensor system 200 may also include one or more temperature sensors 204, a processor 210, and a memory 206. The processor 210 may be configured to receive a signal indicative of an analyte concentration level from theAtty. Dkt. No. 4855.147WO1 Client Reference No. 0975PCT01aptamer biosensor 202 and receive a temperature signal indicative of a temperature parameter (e.g. absolute or relative temperature, or a temperature gradient) from the temperature sensor 204. The signal indicative of the analyte concentration may be a raw sensor signal or a processed sensor signal. The sensor system 200 may also include one or more additional sensors 208, which may include, by way of example and not limitation, a heart rate sensor, activity sensor (e.g. accelerometer), or a pressure gauge (e g. to measure compression of the sensor against a host). In some embodiments, the additional sensors 208 of the sensor system 200 may include a pH sensor to directly measure pH in an environment of the aptamer biosensor 202.

[0095] The processor 210 may determine a temperature-compensated analyte concentration level based on the temperature sensor signal and optionally also based on one or more signals from additional sensor(s) 208. The signal from the temperature sensor 204 may be used as an approximation of a temperature at an analyte sensor, or the signal from the temperature sensor 204 may be processed to determine an estimated analyte temperature sensor based on the signal from the temperature sensor 204.

[0096] The processor 210 may determine a pH-compensated analyte concentration level based on the pH sensor signal and optionally also based on one or more signals from additional sensor(s) 208. As discussed in more detail below, the processor 210 may infer a pH from the interrogation of the aptamer biosensor determine a pH-compensated analyte concentration level from the inferred pH. In some embodiments, the processor 210 may determine both a temperature-compensated and pH-compensated analyte concentration level.

[0097] The processor 210 may retrieve instructions or information from a memory 206 to determine the compensated analyte concentration level. For example, the processor may access a look-up table, or apply an algorithm or a model (e.g., use a state model or neural network).

[0098] In some examples, the processor may retrieve executable instructions from the memory 206 (or a separate memory that may beAtty. Dkt. No. 4855.147WO1 Client Reference No. 0975PCT01operatively coupled to or integrated into the processor.) In some examples, the processor may include, or be part of, an application-specific integrated circuit (ASIC) that may be configured to determine a temperature- compensated analyte concentration level, determine a pH-compensated analyte concentration level, or determine both a temperature-compensated and pH-compensated analyte concentration level. In various examples, any¬ one or more of the methods described herein may be executed by the processor 210, either alone or in combination with other processors or devices.

[0099] FIG. 3 illustrates, by way of example and not limitation, a medical device system 300 including the analyte sensor system 102 of FIG. 1. In the example of FIG. 3, the analyte sensor system 102 includes sensor electronics 106 and an example sensor mounting unit 390, although in some examples, it will be appreciated that the aptamer biosensor 104 and sensor electronics 106 may be included in a common enclosure. While a specific example of division of components between the sensor mounting unit 390 and sensor electronics 106 is shown, it is understood that some examples may include additional components in the sensor mounting unit 390 or in the sensor electronics 106, and that some of the components (e.g., a battery or supercapacitor) that are shown in the sensor electronics 106 may be alternatively or additionally (e.g., redundantly) provided in the sensor mounting unit 390.

[0100] In the example shown in FIG. 3, the sensor mounting unit 390 includes the aptamer biosensor 104 and a battery 392. In some examples, the sensor mounting unit 390 may be replaceable, and the sensor electronics 106 may include a debouncing circuit (e.g., gate with hysteresis or delay) to avoid, for example, recurrent execution of a power-up or power down process when a battery- is repeatedly connected and disconnected or avoid processing of noise signal associated with removal or replacement of a battery.

[0101] The sensor electronics 106 may include electronics components that are configured to process sensor information, such as raw sensor signals, and generate corresponding analyte concentration values. TheAtty. Dkt. No. 4855.147WO1 Client Reference No. 0975PCT01sensor electronics 106 may, for example, include electronic circuitry associated with measuring, processing, storing, or communicating continuous analyte sensor data, including prospective algorithms associated with processing and calibration of the raw sensor signal. The sensor electronics 106 may include hardware, firmware, and / or software that enables measurement of levels of the analyte via an analyte sensor. Electronic components may be affixed to a printed circuit board (PCB), or the like, and can take a variety of forms. For example, the electronic components may take the form of an integrated circuit (IC), such as an Application-Specific Integrated Circuit (ASIC), a microcontroller, and / or a processor.

[0102] In the example of FIG. 3, the sensor electronics 106 include a measurement circuit 302 (e.g., potentiostat) coupled to the aptamer biosensor 104 and configured to recurrently obtain analyte sensor readings using the aptamer biosensor 104. For example, the measurement circuit 302 may continuously or recurrently sample a raw sensor signal indicating a current flow at the aptamer biosensor 104 between a working electrode and a reference electrode. The sensor electronics 106 may include a gate circuit 394, which may be used to gate the connection between the measurement circuit 302 and the aptamer biosensor 104.

[0103] The sensor electronics 106 may also include a processor 304 configured to retrieve instructions 306 from memory 308 and execute the instructions 306 to control various operations in the analyte sensor system 102. For example, the processor 304 may be programmed to control the interrogation of the aptamer biosensor 104 by applying potentials via a potentiostat at the measurement circuit 302, interpreting raw sensor signals from the aptamer biosensor 104, and / or compensating for environmental factors.

[0104] The processor 304 may also save information in data storage memory 310 or retrieve information from data storage memory 310. In various examples, data storage memory 310 may be integrated with memory 308, or may be a separate memory circuit, such as anon-volatile memory circuit (e.g., flash RAM).Atty. Dkt. No. 4855.147WO1 Client Reference No. 0975PCT01

[0105] The sensor electronics 106 may also include one or more sensors, such as the sensor 312, which may be coupled to the processor 304. The sensor 312 may be a temperature sensor, pH sensor, accelerometer, and / or another suitable sensor. The sensor electronics 106 may also include a power source such as a capacitor or battery' 314, which may be integrated into the sensor electronics 106, or may be removable, or part of a separate electronics unit. The battery 314 (or other power storage component, e.g., capacitor) may optionally be rechargeable via a wired or wireless (e.g., inductive or ultrasound) recharging system 316. The recharging system 316 may harvest energy or may receive energy from an external source or on-board source. In various examples, the recharge circuit may include a triboelectric charging circuit, a piezoelectric charging circuit, an RF charging circuit, a light charging circuit, an ultrasonic charging circuit, a heat charging circuit, a heat harvesting circuit, or a circuit that harvests energy from the communication circuit. In some examples, the recharging circuit may recharge the rechargeable battery using power supplied from a replaceable battery' (e.g., a battery' supplied with a base component).

[0106] The sensor electronics 106 may also include one or more supercapacitors in the sensor electronics unit (as shown), or in the sensor mounting unit 390. For example, the supercapacitor may allow energy to be drawn from the battery' 314 in a highly consistent manner to extend the life of the battery 314. The battery 314 may recharge the supercapacitor after the supercapacitor delivers energy to the communication circuit or to the processor 304, so that the supercapacitor is prepared for delivery of energy' during a subsequent high-load period. In some examples, the supercapacitor may be configured in parallel with the battery 314. A device may be configured to preferentially draw energy from the supercapacitor, as opposed to the battery 314. In some examples, a supercapacitor may be configured to receive energy' from a rechargeable battery' for short-term storage and transfer energy to the rechargeable battery for long-term storage.

[0107] The sensor electronics 106 may also include a wireless communication circuit 318, which may for example include a wireless transceiver operatively coupled to an antenna. The wireless communicationAtty. Dkt. No. 4855.147WO1 Client Reference No. 0975PCT01circuit 318 may be operatively coupled to the processor 304 and may be configured to wirelessly communicate with one or more peripheral devices or other medical devices, such as an insulin pump or smart insulin pen.

[0108] In the example of FIG. 3, the medical device system 300 also includes optional external devices including, for example, a peripheral device 350. The peripheral device 350 may be any suitable user computing device such as, for example, a wearable device (e.g., activity monitor), such as a wearable device 120. In other examples, the peripheral device 350 may be a hand-held smart device (e.g., smartphone or other device), a tablet 114, a smart pen 116, or special-purpose computer 118 shown in FIG. 1.

[0109] The peripheral device 350 may include a user interface 352. a memory circuit 354, a processor 356, a wireless communication circuit 358, a sensor 360, or any combination thereof. The peripheral device 350 may not necessarily include all the components shown in FIG. 3. The peripheral device 350 may also include a power source, such as a battery'.

[0110] The user interface 352 may, for example, be provided using any suitable input / output device or devices of the peripheral device 350 such as, for example, a touch-screen interface, a microphone (e.g., to receive voice commands), or a speaker, a vibration circuit, or any combination thereof. The user interface 352 may receive information from the host or another user (e.g., instructions, analyte values). The user interface 352 may also deliver information to the host or other user, for example, by displaying user interface elements at the user interface 352. For example, user interface elements can indicate analyte concentration values, analyte trends, or analyte alerts, etc. Trends can be indicated by user interface elements such as arrows, graphs, charts, etc.

[0111] The processor 356 may be configured to present information to a user, or receive input from a user, via the user interface 352. The processor 356 may also be configured to store and retrieve information, such as communication information (e.g.. pairing information or data center access information), user information, sensor data or trends, or other information in the memory circuit 354. The wireless communication circuit 358 may7Atty. Dkt. No. 4855.147WO1 Client Reference No. 0975PCT01include a transceiver and antenna configured to communicate via a wireless protocol, such as any of the wireless protocols described herein. The sensor 360 may, for example, include an accelerometer, a temperature sensor, a location sensor, biometric sensor, a blood pressure sensor, heart rate sensor, respiration sensor, or another physiologic sensor.

[0112] The peripheral device 350 may be configured to receive and display sensor information that may be transmitted by sensor electronics 106 (e.g., in a customized data package that is transmitted to the display¬ devices based on their respective preferences). Sensor information (e.g., analyte concentration level) or an alert or notification (e.g., “high analyte level”, "low analyte level” or “an alert regarding a rate of change of the analyte” may be communicated via the user interface 352 (e.g., via visual display, sound, or vibration). In some examples, the peripheral device 350 may be configured to display or otherwise communicate the sensor information as it is communicated from the sensor electronics 106 (e.g., in a data package that is transmitted to respective display devices). For example, the peripheral device 350 may transmit data that has been processed (e.g., an estimated analyte concentration level that may be determined by processing raw sensor data), so that a device that receives the data may not be required to further process the data to determine usable information (such as the estimated analyte concentration level). In other examples, the peripheral device 350 may process or interpret the received information (e.g., to declare an alert based on analyte values or an analyte trend). In various examples, the peripheral device 350 may receive information directly from sensor electronics 106, or over a network (e.g., via a cellular or Wi-Fi network that receives information from the sensor electronics 106 or from a device that is communicatively coupled to the sensor electronics 106).

[0113] In the example of FIG. 3, the medical device system 300 includes an optional medical device 370. For example, the medical device 370 may be an external device used in addition to or instead of the peripheral device 350. The medical device 370 may be or include any suitable type of medical or other computing device including, for example, the medical device 108. peripheral medical device 122. wearable device 120, wearableAtty. Dkt. No. 4855.147WO1 Client Reference No. 0975PCT01sensor 130, or wearable sensor 136 shown in FIG. 1. The medical device 370 may include a user interface 372, a memory circuit 374, a processor 376, a wireless communication circuit 378, a sensor 380, a therapy circuit 382, or any combination thereof.

[0114] Similar to the user interface 352, the user interface 372 may be provided using any suitable input / output device or devices of the medical device 370 such as, for example, a touch-screen interface, a microphone, or a speaker, a vibration circuit, or any combination thereof. The user interface 372 may receive information from the host or another user (e.g., analyte values, alert preferences, calibration coding). The user interface 372 may also deliver information to the host or other user, for example, by displaying user interface elements at the user interface 352. For example, user interface elements can indicate analyte concentration values, analyte trends, or analyte alerts, etc. Trends can be indicated by user interface elements such as arrows, graphs, charts, etc.

[0115] The processor 376 may be configured to present information to a user, or receive input from a user, via the user interface 372. The processor 376 may also be configured to store and retrieve information, such as communication information (e.g., pairing information or data center access information), user information, sensor data or trends, or other information in the memory circuit 374. The wireless communication circuit 378 may include a transceiver and antenna configured communicate via a wireless protocol, such as any of the wireless protocols described herein.

[0116] The sensor 380 may, for example, include an accelerometer, a temperature sensor, a location sensor, biometric sensor, blood pressure sensor, heart rate sensor, respiration sensor, or another physiologic sensor. The medical device 370 may include two or more sensors (or memories or other components), even though only one sensor 380 is shown in the example in FIG. 3. In various examples, the medical device 370 may be a smart handheld analyte sensor, drug pump, or other physiologic sensor device, therapy device, or combination thereof.

[0117] In examples where medical device 370 is or includes an insulin pump, the pump and analyte sensor system 102 may be in two-wayAtty. Dkt. No. 4855.147WO1 Client Reference No. 0975PCT01communication (e.g., so the pump can request a change to an analyte transmission protocol, e.g., request a data point or request data on a more frequent schedule), or the pump and analyte sensor system 102 may communicate using one-way communication (e.g., the pump may receive analyte concentration level information from the analyte sensor system). In one-way communication, an analyte value may be incorporated in an advertisement message, which may be encrypted with a previously shared key. In a two-way communication, a pump may request a value, which the analyte sensor system 102 may share, or obtain and share, in response to the request from the pump, and any or all of these communications may be encrypted using one or more previously shared keys. A pump may receive and track analyte values transmitted from analyte sensor system 102 using one-way communication to the pump for one or more of a variety of reasons. For example, a pump may suspend or activate administration a drug or other substance based on an analyte value being below or above a threshold value.

[0118] In some examples, the medical device system 300 includes two or more peripheral devices and / or medical devices that each receive information directly or indirectly from the analyte sensor system 102. Because different display devices provide many different user interfaces, the content of the data packages (e.g., amount, format, and / or type of data to be displayed, alarms, and the like) may be customized (e.g., programmed differently by the manufacturer and / or by an end user) for each device. For example, referring now to the example of FIG. 1, a plurality of different peripheral devices may be in direct wireless communication with sensor electronics 106 (e.g., such as an sensor electronics 106 that are on-skin and physically connected to the aptamer biosensor 104) during a sensor session to enable a plurality of different types and / or levels of display and / or functionality associated with the displayable sensor information, or, to save battery power in the sensor system 102, one or more specified devices may communicate with the analyte sensor system 102 and relay (i.e., share) information to other devices directly or through a server system (e.g., a network-connected data center) 126.Atty. Dkt. No. 4855.147WO1 Client Reference No. 0975PCT01

[0119] FIG. 4A is a side view of an example analyte sensor 434A that may be implanted into a host. An enclosure 402A may be adhered to the host's skin using an adhesive pad 408A. The adhesive pad 408A may be formed from an extensible material, which may be removably attached to the skin using an adhesive. Sensor electronics may be positioned within the enclosure 402A. The sensor 434A may extend from the enclosure 402A and under the skin of a host, as shown.

[0120] FIG. 4B is a side view of another example analyte sensor 434B in an arrangement including a mounting unit 414 and an electronics unit 418. The mounting unit 414 may be adhered to the host's skin using an adhesive pad 408B. The electronics unit 418 comprises an enclosure 402B that may have sensor electronics positioned thereon. For example, the sensor 434 may extend from the enclosure 402 via the mounting unit 414.

[0121] FIG. 5 illustrates, by way of example and not limitation, an aptamer biosensor for monitoring at least one analyte. The illustrated aptamer biosensor 536 may be an example of the aptamer biosensor 104 in FIG. 1 or FIG. 3. aptamer biosensor 202 in FIG. 2, aptamer biosensor 434A in FIG. 4A or aptamer biosensor 434B in FIG. 4B. The aptamer biosensor 536 may be used to perform in vivo measurement of at least one analyte, and may include an aptamer protective material 537. The aptamer biosensor 536 may include an aptamer with a signal transducing element which may be a redox probe 538. An optional monolayer 539 adjacent to a substrate 540 is also illustrated. The monolayer 536 may be covalently or non-covalently coupled to the substrate 540. The aptamer 541 may undergo a reversible conformational change upon interaction with analyte 542, e.g., an analyte, metabolite, drug, etc., which may cause the redox probe 538 to present in closer proximity to substrate 540 to provide a signal corresponding to the analyte concentration or presence. For example, the substrate 540 may be electrically conductive and the reversible binding of the aptamer (and its subsequent reversible conformational change) upon interaction with analyte 542 causes a change in proximity of all or part of the reversible redox probe 538 with respect to the conductive substrate 540 such that the reversible redox probe is capable of undergoing detectable reversible reduction-oxidation reaction(s) via electron transfer with theAtty. Dkt. No. 4855.147WO1 Client Reference No. 0975PCT01conductive substrate upon reversible binding of the analyte 542 with the aptamer 541. Analyte concentration is correlated to the detectable reversible reduction-oxidation reaction(s) via electron transfer with the conductive substrate. The reversible binding of the aptamer (and its subsequent reversible conformational change) upon interaction with the analyte can cause all or part of the redox probe 538 to present in or to a different local environment. Thus, the electron transfer rate kefi when the aptamer is not binding to the aptamer may change to another larger electron transfer rate kef2 when the aptamer binds with the analyte to cause the aptamer to conformally change to bring the redox probe closer to the substrate.

[0122] The redox probe 538 may be covalently or non-covalently coupled to the aptamer 541, where the covalently or non-covalently coupling may be sufficient for continuous signal transduction of signal over a time period commensurate with a transdermal, intradermal, subcutaneous, ocular, or skin based continuous analyte sensing devices. The redox probe 538 and the aptamer 541 may be conjugated or form a conjugate. For example, the redox probe 538 and the aptamer 541 conjugate may be associated with the monolayer 539. For example, the redox probe 538 and the aptamer 541 conjugate may be covalently or non-covalently coupled to the monolayer 539. The redox probe 538 and the aptamer 541 conjugate may be covalently or non-covalently coupled to the substrate 540.

[0123] FIG. 6 illustrates, by way of example and not limitation, an aptamer biosensor 636 for continuous in vivo use in a subject. The illustrated aptamer biosensor 636 may be an example of the aptamer biosensor 104 in FIG. 1 or FIG. 3, aptamer biosensor 202 in FIG. 2, aptamer biosensor 434A in FIG. 4A or aptamer biosensor 434B in FIG. 4B, or aptamer biosensor 536 in FIG. 5. The illustrated aptamer biosensor 636 may be an elongated member having a sensing region 647, for example, created from a window in an electrically insulated coating 648 about a conductive wire. Additional electrodes 649 (reference electrode and / or counter electrode) may be used or provided separately, for example, as an adjacent co-axial elongated member. Alternative structures 650, 651, and 652 of sensing region 647 are shown with the substrate 640. The structureAtty. Dkt. No. 4855.147WO1 Client Reference No. 0975PCT01650 has the substrate 640 surface with an adjacent aptamer 641 and an aptamer protective material 637. The structure 651 has the substrate 640 with an adjacent co-adsorbate 653, an aptamer 641 and an aptamer protective material 637. The structure 652 has the substrate 640 surface with an adjacent co-adsorbate 653, an aptamer 641, an aptamer protective material 637 and a drug-releasing membrane 654 most distal from the substrate 640. Other configurations may be employed. For example, a planar sensor form factor may be implemented.

[0124] The substrate 640 may include a conductive material. The substrate 640 may be an electrode, where the electrode may be a wire, a planar structure or a substantially planar structure. The substrate 640 may be configured to provide, independently, one or more of a working electrode, a reference electrode and optionally a counter electrode. By way of example, the electrodes may be arranged in a linear or substantially linear configuration. For example, the reference electrode may comprise silver (Ag) and / or silver chloride (AgCl) or may comprise silver (Ag) and / or silver chloride (AgCl) encapsulated or otherwise covered with a protective layer. The reference electrode with a protective layer may be configured to reduce or eliminate diffusion of AgCl+, Ag, AgCl'2, ions or particles from the reference electrode and / or reduce or eliminate interaction of the reference electrode or AgCl+ ion with the aptamer and / or a thiol-containing co- adsorbate or a thiol-containing aptamer protective layer. The protective layer of the silver reference electrode may be configured to inhibit or reduce transport of AgCl+ ion while allowing transport of chloride ion. Examples of protective layers suitable for the silver reference electrode may include, but are not limited to amphiphilic polyurethane or polyurethane urea, Teflon, microporous Teflon, ion selective membranes, semi-permeable membranes, PVC, and plasticized PVC.

[0125] During general operation, a biological sample, such as blood, interstitial fluid, or a component thereof, contacts an aptamer having one or more analyte binding regions, each region capable of specifically and reversibly binding to at least one analyte. The biological sample may either directly contact the aptamer or may pass through one or more membranesAtty. Dkt. No. 4855.147WO1 Client Reference No. 0975PCT01before contacting the aptamer. The interaction of the biological sample or component thereof with the aptamer induces a measurable transduced signal. The analyte level in the biological sample may be determined using the transduced signal. The sensing region 647 or sensing portion may include at least a portion of a conductive substrate or at least a portion of a conductive surface such as but not limited to a wire or a conductive trace. The sensing region 647 or sensing portion may include a nonconductive body, a working electrode, a reference electrode, and an optional counter electrode forming an electrochemically reactive surface at one location on the body and an electronic connection at another location on the body, and a sensing membrane affixed to the body and covering the electrochemically reactive surface.

[0126] Multiple working electrodes may be included. For example, a second working electrode comprising a plurality of different analyte (e.g.. analyte 1, analyte 2, etc.) aptamer conjugates on the second working electrode to correct for sensor drift and / or interference. Likewise, a second working electrode comprising a non-selective aptamer conjugate to a plurality of different analytes (e.g., analyte 1, analyte 2, etc.) on the second working electrode can be used to correct for sensor drift and / or interference.

[0127] An aptamer biosensor has significant differences from an enzymatic amperometric sensor. For example, existing continuous glucose monitors may rely on an enzymatic amperometric sensor which depends on an enzymatic reaction of an analyte. A brief description of the enzymatic reaction is provided below. FIG. 7A illustrates the reaction-based detection of an analyte 742. The sensor signal is determined by mass transport through a resistive layer 755. In a continuous glucose monitor, the analyte 742 (e.g., “glucose”), may penetrate a resistive layer 755 to react, as illustrated at 756, with the enzyme generating peroxide. For example, an enzyme-based electrochemical sensor may include a working electrode that that creates a measurable electronic current to measure the product of the enzyme catalyzed reaction of the glucose that is being detected. In addition to the working electrode, the sensor may include a reference electrode and may further include a counter electrode to balance theAtty. Dkt. No. 4855.147WO1 Client Reference No. 0975PCT01current generated by the species being measured at the working electrode. In the case of a glucose oxidase based glucose sensor, the species measured at the working electrode is hydrogen peroxide (H2O2) 757.Glucose oxidase, GOX, catalyzes the conversion of O2758 and glucose 742 to H2O2757 and gluconate 759 according to the following reaction:GOX+Glucose+O2^Gluconate+H2O2+reduced GOX[1]

[0128] In a reaction-based, enzymatic amperometric sensor, the change in H2O2 may be monitored to determine glucose concentration because for each glucose molecule metabolized, there is a proportional change in H2O2. Oxidation of H2O2by the working electrode may be balanced by reduction of ambient oxygen, enzyme generated H2O2, or other reducible species at the counter electrode. The H2O2 produced from the glucose oxidase reaction further reacts at the surface of working electrode and produces two protons (2H+), two electrons (2e~), and one oxygen molecule (O2), such that the reaction produces the electronic current that is detected.Potentiostat(s) may monitor the electrochemical reaction at the electroactive surface of the working electrode(s) by applying a constant potential to the working electrode and its associated reference electrode to determine the current produced at the working electrode. The current that is produced at the working electrode (and flows through the circuitry to the counter electrode) is substantially proportional to the amount of H2O2 that diffuses to the working electrode. The steady state faradaic current, which is the current generated by the reduction or oxidation of the analyte at an electrode, is proportional to the analyte (e.g., glucose). The output signal is typically a raw data stream that is used to provide a useful value of the measured analyte concentration in a host to the host or doctor, for example.

[0129] Unlike the reaction-based, enzymatic amperometric sensor discussed with respect to FIG. 7 A, the aptamer sensor technology does not rely on the reaction of an enzyme. Rather, as is illustrated in FIG. 7B, the target molecules 742 are binding to the aptamer in an affinity-based fashion, and inducing the conformational change of the aptamer 741. For example, the aptamer (e g., single strand RNA or DNA) may conformallyAtty. Dkt. No. 4855.147WO1 Client Reference No. 0975PCT01change (e.g., change from one form or shape to another form or shape) when the target molecules bind to the aptamer. The changed shape of the aptamer causes a signal to be generated. For example, the changed shape may move a redox probe 738 closer or further away from the substrate 740, which may change an electron transfer rate between the reversible redox probe 738 and the conductive substrate 740. The change in the electron transfer rate is proportional to the analyte concentration. The signal on the conductive substrate may be determined by electron transfer rate from a reversible redox probe to the conductive substrate. The substrate 740 may include gold, with a self-assembled monolayer 779 on the substrate. For example, the monolayer may include thiol-Au chemistry. The aptamerredox probe 738 may be coupled to the aptamer 741 and may move when the aptamer 741 changes shape. The architecture of the aptamer biosensor may include a co-adsorbate and an aptamer protection layer 737.

[0130] Aptamer biosensors have some inherent difficulties because of sensitivity to environmental conditions. For example, it has been observed that environmental conditions such as pH and / or temperature can adversely affect the accuracy of the aptamer biosensor. The term pH stands for “potential of hydrogen” and corresponds to the concentration of hydrogen ions and where a pH number provides a measure of acidity or alkalinity of a solution. It has been observed that signals from electrochemical aptamer sensors (EAB) are prone to pH interference. While not to be held to any particular theory, it is believed that the pH interference is due to one or more of the following:i. reaction rate of the redox probe (used to transduce the aptameranalyte binding event) is pH-sensitive. For example, with methylene blue (MB) redox moiety, the redox reaction of one MB molecule involves one proton, making it sensitive to hydrogen ion concentration (environmental pH variation) during use;ii. DNA / RNA backbone of the aptamer can be pH sensitive. For example, protonation / deprotonation of DNA / RNA bases results in different favored base pairing and thus may alter the secondary structure of aptamer.Atty. Dkt. No. 4855.147WO1 Client Reference No. 0975PCT01Variation in secondary structure will likely result in EAB signal variation during use; andiii. subcutaneous interstitial fluid has varying pH (sensor insertion creates wound, and thus will cause variation of local pH about the aptameric sensor during use).Thus, the sensor function not only depends on the analyte concentration but also depends on pH in the environment.

[0131] The aptamers (e.g., single strain DNAs or RNAs) for the biosensor are relatively easy to engineer to have an affinity7to different analytes. Aptameric technology may be used for drug sensing. Pharmacologic agents may be precisely benefited by monitoring drug molecules. By way of example and not limitation, a widely-used antibiotic includes vancomycin. Monitoring of vancomycin may be particularly beneficial for managing sepsis treatment. Future aptamers may be developed for diabetic care (e.g., C-peptide, insulin), for kidney biomarkers (e.g., NGAL, Cystatin C), for cardiovascular biomarkers (BNP, troponin), for hormones (e.g., cortisol, norepinephrine), for care of females (e.g., luteinizing hormone, estrogens).

[0132] It may be possible, albeit difficult, to make the sensor insensitive to pH by changing the probe to another molecule and change the DNA sequence to be immune to pH changes. Thus, the difficulties to make the sensor insensitive to pH diminishes the advantages that aptamers have in being easily engineered to detect different analytes. It is desirable to use such engineered aptamers without also having to make the aptamers immune to pH changes.

[0133] The aptamer biosensor may be interrogated to determine responses of the biosensor, and these responses may be used to determine an estimated analyte value for the target analyte that is detected by the aptamer biosensor. By way of example, and not limitation, the biosensor may be interrogated every 5 minutes. The interrogation may be performed at other intervals. The interrogation may be performed at equal intervals. The interrogation may be performed at variable intervals. For example, the interrogation may be performed more often near times of particular interest (e.g., maximums in the current or voltage measurements).Atty. Dkt. No. 4855.147WO1 Client Reference No. 0975PCT01

[0134] For example, the biosensor may be interrogated by applying an electrical stimulus the biosensor and measuring an electrical response to the electrical stimulus. An adjusted current value may be determined by inferring a pH measurement from the electrical response. Applying the electrical stimulus to the biosensor includes applying a voltage profile to a working electrode of the biosensor as a function of time, and the measured electrical response may include measuring an electrical response to the applied voltage profile. The voltage profile may be applied using a square wave voltammetry7technique. The electrical response to the voltage profile may a peak voltage measure, and the pH measurement may be inferred using at least the peak voltage measure. The measured electrical response may include a peak current. The adjusted current value may be determined using the peak voltage measure and the current response, and an estimated analyte value for the target analyte is determined based on the adjusted current value. Thus, by way of example and not limitation, voltammetry may be used to track an electron transfer rate of a redox probe.Voltammetry is a technique that may be used to analyze electrochemical systems by applying a voltage to the system, changing a voltage as a function of time, and measuring the resulting current. Square wave voltammetry is used herein as a specific example of voltammetry. Other voltammetry examples include, but are not limited to, pulse voltammetry, linear sweep voltammeter, and cyclic voltammetry'. In some embodiments, applying the electrical stimulus to the biosensor may include applying an open-circuit potential between a working electrode and a reference electrode of the biosensor, and the electrical response may include an electrical response to the open-circuit potential, and the pH measurement is inferred using the open-circuit potential.

[0135] FIG. 8 illustrates, by way of example and not limitation, an interrogation output for an aptamer biosensor, and more particularly illustrates current and voltage outputs from square wave voltammetry7. A chart is illustrated with an x-axis representing different applied voltages in volts (V) and the y axis representing different observed current in microamps (pA). The different waveforms in the chart correspond to different values for an analyte concentration illustrated as ranging from a 0Atty. Dkt. No. 4855.147WO1 Client Reference No. 0975PCT01micromolar (pM) solution to 100 pM solution. The different waveforms generally have the same shape but, as is illustrated in the chart, the increasing concentrations correspond to increasing peak current amplitudes. Additionally, it is noted that the peak current for the concentrations also shift right with the increasing concentrations, indicating that the peak current is occurring at larger voltages for the higher analyte concentrations. In the illustrated chart, the peak current 860 for the 0 pM corresponds to about -0.30 V, and the peak current 861 for the 100 pM solution corresponds to about -0.28 V. Various embodiments use the peak current output from the applied voltammetry (e.g., applied square wave voltammetry) as a signal. Various embodiments also use the corresponding voltage for the peak current as an output from the applied voltammetry as it depends on the pH in the environment of the aptamer biosensor. FIG. 8 is provided to generally illustrate some information that may be contained in an interrogation output for an aptamer biosensor. It is noted that the interrogation was performed on a different electrode form factor than other waveforms provided herein. Thus, for example, the interrogation output illustrated in FIG. 11 should not be confused with the interrogation output illustrated in FIG. 8.

[0136] FIG. 9A illustrates an example of a method for determining an analyte value using an aptamer biosensor. At 962A, the electrochemical aptamer-based biosensor is interrogated to obtain a current response 963A. At 964A. a correction is determined and applied to provide an adjusted current value 965 A, which is used to determine the estimated analyte value 966A. Determining the correction 964A may include receiving a temperature signal 967 and correcting for the temperature. The temperature may be sensed by the biosensor. Determining the correction may include receiving a pH signal 968. The pH may be sensed by a pH sensor.However, a pH sensor may not need to be incorporated into the design. Rather, determining the correction may include receiving an inferred pH signal 968. The pH may be inferred from an electrical response. The correction may be based on one or more than one of the received temperatures 967, received pH measure 968A, or inferred pH 968B.Atty. Dkt. No. 4855.147WO1 Client Reference No. 0975PCT01

[0137] FIG. 9B illustrates another example of a method for determining an analyte value using an aptamer biosensor which does not sense pH. At 962B, the electrochemical aptamer-based biosensor may be interrogated to obtain both a current response 963B and a voltage response 969 of the system to the applied voltage. At 964B, a correction is determined and applied to the provide an adjusted current value. The correction may be determined using both the current response 963B and the voltage response 969. For example, the biosensor may be interrogated using square wave voltammetry, and the correction may be made using the peak current and the peak voltage which is the corresponding voltage when the peak current is delivered.

[0138] The sensitivity7of a batch of sensors may be tested in a factory7to provide a sensitivity calibration information. Such sensitivity calibration information may also be used to determine the analyte value from the adjusted current value 965A or 965B.

[0139] FIG. 10 illustrates another example of a method for determining an analyte value to correct for both temperature and pH. At 1070, square wave voltammetry (SWV) readouts. From the SWV readouts 1070, both a raw peak current 1071 and a raw peak voltage 1072 may be determined. A signal from a temperature readout 1073 may be received, and the temperature readout to transform the raw peak current 1071 into a temperature-corrected peak current 1074 and may use the temperature readout 1073 to transfer the raw peak voltage 1072 into a temperature- corrected peak voltage 1075. Correlation data 1076 between the peak current and voltage may be determined via bench or in-vivo testing. The correlation data may be stored in memory within the aptamer biosensor system. The correlation data 1076 may be used to determine a current correction factor 1077 from the temperature-corrected peak voltage, where the current correction factor 1077 may be applied to either the temperature corrected peak current 1074 or to an optional normalized peak current 1078 to provide a corrected current readout 1079. Thus, the corrected current readout 1079 accounts for both the temperature and pH in the environment of the sensor. The illustrated steps are an example of a method for compensating for both pH and temperature. It is expresslyAtty. Dkt. No. 4855.147WO1 Client Reference No. 0975PCT01noted that the steps in the illustrated method may be performed in a different order. For example, the peak current-voltage correlation may be performed to create a corrected readout and the temperature readout may be used to provide a temperature-corrected adjustment to the corrected readout. The normalization 1078 may or may not be included based sensor variation. Also, the temperature-corrected peak voltage correction may also depend on temperature sensitivity. Benchtop data shows both SWV peak potential and peak current are function of pH. This is related to the pH sensitivity' of the redox probe (i.e., methylene blue).

[0140] Thus, the adjusted current value may be determined to correct for both pH and / or temperature. Interrogating the biosensor may include applying a square wave voltammetry' technique, determining both a raw peak current and a raw peak voltage for the applied square wave voltammetry technique. The adjusted current value may be determined by determining a current correction factor based on the raw peak voltage, and determining the adjusted current value based on the raw peak current and the current correction factor. The current correction factor may be determined using the raw peak voltage. A regression analysis may be applied to at least one of bench data or in vivo data to determine the current correction factor for the raw peak voltage. The current correction factor is determined using a linear function, a nonlinear function or a piecewise function. The adjusted current value may be determined using a lookup table to look up the current correction factor based on the raw peak voltage. The adjusted current value may be determined using a lookup table to look up the current correction factor based on the raw peak current, the raw peak voltage and a temperature.

[0141] The biosensor may be interrogated by applying a square wave voltammetry' technique, determining both a raw peak current and a raw peak voltage for the applied square wave voltammetry' technique. The adjusted current value may be determined by receiving a temperature signal from a temperature sensor, determining a temperature-corrected peak current using the temperature signal and the raw peak current, determining a temperature-corrected peak voltage using the temperature signal and the raw peak voltage, determining a current correction factorAtty. Dkt. No. 4855.147WO1 Client Reference No. 0975PCT01based on the temperature-corrected peak voltage, and determining the adjusted current value using the temperature-corrected peak current and the current correction factor. The current correction factor may be determined using a peak current-voltage correlation. The temperature-corrected peak current may be normalized to provide a normalized peak current, and the adjusted current value may be determined using the normalized peak current and the current correction factor.

[0142] FIG. 11 illustrates, by way of example and not limitation, an interrogation output for another aptamer biosensor, and more particularly illustrates current and voltage outputs from square wave voltammetry. A chart is illustrated with an x-axis representing different applied voltages in volts (V) and the y axis representing different observed current in nanoamps (nA). However, unlike FIG. 8 where the voltage shifted right as the peak current increased, FIG. 11 shows that the voltage shifts to the right as the peak current decreased. In the illustrated chart, the peak current for the largest wave 1180 is about 24.5 nA and the corresponding voltage is about -0.33 V, and that peak current for the smallest wave 1181 is about 23 nA and the corresponding voltage is about -0.315. The SWV readouts will depend on the analyte(s) that are targeted for detection. Various embodiments use the peak current output from the applied voltammetry (e.g., applied square wave voltammetry ) as a signal. Various embodiments also use the corresponding voltage for the peak current as an output from the applied voltammetry as it depends on the pH in the environment of the aptamer biosensor.

[0143] FIGS. 12A and 12B illustrate, by way of example and not limitation, peak voltage and normalized peak current from square wave voltammetry, over a period of 150 minutes with changing pH. It is noted that trauma from sensor insertion creates a wound in which pH changes. A test was performed using a methylene blue solution where the pH was 7.2 for a first period of time 1282 (e.g.. about the first 55 minutes after insertion), the pH was 6.7 for a second period of time 1283 (e.g., from about 55 minutes to about 105 minutes after insertion), and the pH was 6.2 for a third period of time 1284 (e.g., from about 105 minutes to about 150Atty. Dkt. No. 4855.147WO1 Client Reference No. 0975PCT01minutes after insertion). The changing pH in the solution is intended to test pH changes such as may be found in a wound after trauma.

[0144] Although it may be possible to directly measure the pH in the wound, it may not be practical or otherwise desirable to include a pH sensor with the aptamer biosensor. Peak current is a function of the analyte concentration, but peak voltage is not expected to be a function of the analyte concentration. Thus, because the peak voltage changes as the pH changes, the peak voltage from the voltammetry readouts may be used to infer the pH measurement. In an example, rather than inferring the pH measurement, a correlation between the peak current and voltage may be determined based on bench or in-vivo testing. Thus, a correction factor may be determined from the peak voltage for application to the peak current to provide a pH-compensated peak current.

[0145] FIG. 13A and FIG. 13B illustrate, by way of example and not limitation, plots of peak voltage and peak current, respectively over about 120 minutes for four sensors (SI, S2, S3. S4), where the pH changes from 7.4 to 6.5 with a finer resolution than shown in FIGS. 12A-12B. As illustrated in FIG. 13 A, the peak voltages for these four sensors follow a similar curve where the increases in the peak voltages are at least partially attributable to changes in pH over time. Similarly, FIG. 13B illustrates the peak current for these four sensors also follow a similar curve where decreases in the peak current are also at least partially attributable to changes in the pH over time.

[0146] FIGS. 14A and 14B illustrate for one sensor and four sensors, by way of example and not limitation, respectively, plots of a peak current (nA) over peak voltage (V). In a benchtop test, the pH was changed from 7.4 to 6.5 as illustrated in FIGS. 13A-13B. These plots suggest that the relationship between peak current and peak voltage seems to follow a quadratic equation as the peak current and peak voltage vary over the range of pH values. FIG. 15 is a similar plot to FIG. 14B, illustrating a plot of normalized peak current over peak voltage (V), which also suggest that a quadratic equation may correspond to the peak current and peak voltage variations over the range of pH values.Atty. Dkt. No. 4855.147WO1 Client Reference No. 0975PCT01

[0147] FIGS. 16A and 16B illustrate plots of peak voltage (V) and peak current (nA), respectively, for four sensors (SI, S2, S3, S4), by way of example and not limitation, where the temperature ranges between 35°C to 25°C over 250 minutes. The test starts with using a heater to raise a temperature of the solution to 35°C and, after turning the heater off around 30 minutes, allowing the solution to cool to 25°C at around 240 minutes, and then turning the heater on again to raise the temperature of the solution to 35°C again. Peak voltage is a relatively weak function of temperature (see FIG. 16A), where there is about 10 mV change per 10°C on an Ag / AgCl electrode. The peak current is a stronger function of temperature (see FIG. 16B), as there is about a 35% signal loss in the peak current when the temperature changes from 35°C to 25°C.

[0148] FIG. 17A illustrates a plot of peak current over peak voltage for one sensor for the test where the temperature ranges between 35 °C to 25°C, FIG. 17B illustrates a plot of peak current over peak voltage for four sensors for the test, and FIG. 17C illustrates a plot of a normalized peak current over peak voltage for four sensors for the test. These plots suggest that the relationship between peak current and peak voltage seems to follow a quadratic equation as the peak current and peak voltage vary over the temperature range.

[0149] After break-in, there is a pH change in wound pocket, which reduce the peak current height. However, pH alters both peak position (peak voltage) as well as the peak height (peak current). The peak position may be used to correct the peak current readout and may be used to improve accuracy during the first day when there are significant pH changes in the wound pocket. There is a strong correlation observed in line with benchtop observation after break in (e.g., 7 to 17 hours after insertion).

[0150] An algorithm may use a retrospective linear model to correct for current readout. It is noted that the algorithm does not reflect hypothetical physics but it may significantly increase the signal to noise ratio. In vivo correction may be performed using a regression analysis. For example, aAtty. Dkt. No. 4855.147WO1 Client Reference No. 0975PCT01simple regression equation and leveraging peak voltage readout and correct for the sensor signal.I corrected^ I _original+k*(V_ref-V_r ecorded)[2] Other algorithms, such as nonlinear functions or piecewise functions, may be used to better fit the curve and further increase the signal to noise ratio. Some embodiments may use a lookup table to look up a current correction factor based on the raw peak voltage.

[0151] FIG. 18A illustrates the raw peak current 1890 and raw peak voltage 1891 and FIG. 18B illustrates the corrected peak current 1892 along with an indicator of when an analyte is infused (vancomycin) 1893. Notably, there is no analyte in the system before vancomycin is infused. The same simple regression equation may be used to flatten the current at 1894 when there is no analyte to cause before the vancomycin in infused (e g., 4 to 17 hours after insertion).

[0152] FIG. 19 illustrates, by way of example and not limitation, a computing device hardware architecture 1900. within which a set or sequence of instructions can be executed to cause a machine to perform examples of any one of the methodologies discussed herein. The hardware architecture 1900 can describe various computing devices including, for example, the sensor electronics 106, the peripheral medical device 122, the smart device 112, the tablet 114, etc.

[0153] The architecture 1900 may operate as a standalone device or may be connected (e.g.. networked) to other machines. In a networked deployment, the architecture 1900 may operate in the capacity of either a server or a client machine in server-client network environments, or it may act as a peer machine in peer-to-peer (or distributed) network environments. The architecture 1900 can be implemented in a personal computer (PC), a tablet PC. a hybrid tablet, a set-top box (STB), a personal digital assistant (PDA), a mobile telephone, a web appliance, a network router, a network switch, a network bridge, or any machine capable of executing instructions (sequential or otherwise) that specify operations to be taken by that machine.Atty. Dkt. No. 4855.147WO1 Client Reference No. 0975PCT01

[0154] The example architecture 1900 includes a processor unit 1902 comprising at least one processor (e.g.. a central processing unit (CPU), a graphics processing unit (GPU), or both, processor cores, compute nodes). The architecture 1900 may further comprise a main memory 1904 and a static memory 1906, which communicate with each other via a link 1908 (e g., bus). The architecture 1900 can further include a video display unit 1910, an input device 1912 (e.g., a keyboard), and a UI navigation device 1914 (e g., a mouse). In some examples, the video display unit 1910, input device 1912, and UI navigation device 1914 are incorporated into a touchscreen display. The architecture 1900 may additionally include a storage device 1916 (e.g., a drive unit), a signal generation device 1918 (e.g., a speaker), a network interface device 1920, and one or more sensors (not shown), such as a Global Positioning System (GPS) sensor, compass, accelerometer, or another sensor.

[0155] In some examples, the processor unit 1902 or another suitable hardware component may support a hardware interrupt. In response to a hardware interrupt, the processor unit 1902 may pause its processing and execute an ISR, for example, as described herein.

[0156] The storage device 1916 includes a machine-readable medium 1922 on which is stored one or more sets of data structures and instructions 1924 (e g., software) embodying or used by any one or more of the methodologies or functions described herein. The instructions 1924 can also reside, completely or at least partially, within the main memory 1904, within the static memory 1906, and / or within the processor unit 1902 during execution thereof by the architecture 1900, w ith the main memory 1904. the static memory 1906, and the processor unit 1902 also constituting machine-readable media.Atty. Dkt. No. 4855.147WO1 Client Reference No. 0975PCT01EXECUTABLE INSTRUCTIONS AND MACHINE-STORAGE MEDIUM

[0157] The various memories (i.e., 1904, 1906, and / or memoiy of the processor unit(s) 1902) and / or storage device 1916 may store one or more sets of instructions and data structures (e.g., instructions 1924) embodying or used by any one or more of the methodologies or functions described herein. These instructions, when executed by processor unit(s) 1902 cause various operations to implement the disclosed examples.

[0158] As used herein, the terms "machine-storage medium,” '‘devicestorage medium,” “computer-storage medium” (referred to collectively as “machine-storage medium 1922”) mean the same thing and may be used interchangeably in this disclosure. The terms refer to a single or multiple storage devices and / or media (e.g., a centralized or distributed database, and / or associated caches and servers) that store executable instructions and / or data, as well as cloud-based storage systems or storage networks that include multiple storage apparatus or devices. The terms shall accordingly be taken to include, but not be limited to. solid-state memories, and optical and magnetic media, including memory internal or external to processors. Specific examples of machine-storage media, computer-storage media, and / or device-storage media 1922 include nonvolatile memory, including by way of example semiconductor memory devices, e.g., erasable programmable read-only memory (EPROM), electrically erasable programmable read-only memory (EEPROM), FPGA, and flash memory7devices; magnetic disks such as internal hard disks and removable disks; magneto-optical disks; and CD-ROM and DVD-ROM disks. The terms machine-storage media, computer-storage media, and device-storage media 1922 specifically exclude carrier waves, modulated data signals, and other such media, at least some of which are covered under the term “signal medium"’ discussed below.SIGNAL MEDIUM

[0159] The term “signal medium” or “transmission medium” shall be taken to include any form of modulated data signal, carrier wave, and soAtty. Dkt. No. 4855.147WO1 Client Reference No. 0975PCT01forth. The term “modulated data signal” means a signal that has one or more of its characteristics set or changed in such a matter as to encode information in the signal.COMPUTER-READABLE MEDIUM

[0160] The terms “machine-readable medium,” “computer-readable medium” and “device-readable medium” mean the same thing and may be used interchangeably in this disclosure. The terms are defined to include both machine-storage media and signal media. Thus, the terms include both storage devices / media and carrier waves / modulated data signals.

[0161] The instructions 2024 can further be transmitted or received over a communications network 2026 using a transmission medium via the network interface device 2020 using any one of a number of well-known transfer protocols (e.g., HTTP). Examples of communication networks include a LAN, a WAN, the Internet, mobile telephone networks, plain old telephone service (POTS) networks, and wireless data networks (e.g., WiFi, 3G, 4G LTE / LTE-A, 5G or WiMAX networks). The term “transmission medium” shall be taken to include any intangible medium that is capable of storing, encoding, or carrying instructions for execution by the machine, and includes digital or analog communications signals or other intangible media to facilitate communication of such software.

[0162] Throughout this specification, plural instances may implement components, operations, or structures described as a single instance.Although individual operations of one or more methods are illustrated and described as separate operations, one or more of the individual operations may be performed concurrently, and nothing requires that the operations be performed in the order illustrated. Structures and functionality presented as separate components in example configurations may be implemented as a combined structure or component. Similarly, structures and functionality presented as a single component may be implemented as separate components. These and other variations, modifications, additions, and improvements fall within the scope of the subject matter herein.Atty. Dkt. No. 4855.147WO1 Client Reference No. 0975PCT01

[0163] Various components are described in the present disclosure as being configured in a particular way. A component may be configured in any suitable manner. For example, a component that is or that includes a computing device may be configured with suitable software instructions that program the computing device. A component may also be configured by virtue of its hardware arrangement or in any other suitable manner.

[0164] The examples in any portion of the above description may stand on its own or may be combined in various permutations or combinations with one or more of the other examples. In this document, the terms “a” or ”an“ are used, as is common in patent documents, to include one or more than one, independent of any other instances or usages of “at least one” or “one or more.” In this document, the term “or” is used to refer to a nonexclusive or, such that “A or B” includes “A but not B,” “B but not A,” and “A and B,” unless otherwise indicated. In this document, the terms “including” and “in which” are used as the plain-English equivalents of the respective terms “comprising” and “wherein.” Also, in the following claims, the terms “including” and “comprising” are open-ended, that is, a system, device, article, composition, formulation, or process that includes elements in addition to those listed after such a term in a claim are still deemed to fall within the scope of that claim. Moreover, terms such as “first,” “second,” “third,” and the like may be used merely as labels without an intent to impose numerical requirements on their objects.

[0165] Method examples described herein can be machine or computer- implemented at least in part. Some examples can include a computer- readable medium or machine-readable medium encoded with instructions operable to configure an electronic device to perform methods as described in the above examples. An implementation of such methods can include code, such as microcode, assembly language code, a higher-level language code, or the like. Such code can include computer readable instructions for performing various methods. The code may form portions of computer program products. Further, in an example, the code can be tangibly stored on one or more volatile, non-transitory, or non-volatile tangible computer- readable media, such as during execution or at other times. Examples of these tangible computer-readable media can include, but are not limited to,Atty. Dkt. No. 4855.147WO1 Client Reference No. 0975PCT01hard disks, removable magnetic disks, removable optical disks (e.g., compact disks and digital video disks), magnetic cassettes, memory cards or sticks, random access memories (RAMs), read only memories (ROMs), and the like.

[0166] The above detailed description includes references to the accompanying drawings, which form a part of the detailed description. The drawings show, by way of illustration, specific embodiments in which the subject matter can be practiced. These embodiments are also referred to herein as “examples.” Such examples can include elements in addition to those shown or described. However, the present inventors also contemplate examples in which only those elements shown or described are provided. Moreover, the present inventors also contemplate examples using any combination or permutation of those elements shown or described (or one or more aspects thereof), either with respect to a particular example (or one or more aspects thereof), or with respect to other examples (or one or more aspects thereof) shown or described herein.

[0167] The above description is intended to be illustrative, and not restrictive. For example, the above-described examples (or one or more aspects thereof) can be used in combination with others. Other examples can be used, such as by one of ordinary skill in the art upon reviewing the above description. The Abstract is to allow the reader to quickly ascertain the nature of the technical disclosure, for example, to comply with 37 C.F.R. §1.72(b) in the United States of America. It is submitted with the understanding that it will not be used to interpret or limit the scope or meaning of the claims.

[0168] Also, in the above Detailed Description, various features can be grouped together to streamline the disclosure. However, the claims cannot set forth every feature disclosed herein, as examples can feature a subset of said features. Further, examples can include fewer features than those disclosed in a particular example. Thus, the following claims are hereby incorporated into the Detailed Description, with each claim standing on its own as a separate example. The scope of the examples disclosed herein isAtty. Dkt. No. 4855.147WO1 Client Reference No. 0975PCT01to be determined with reference to the appended claims, along with the full scope of equivalents to which such claims are entitled.

Claims

Atty. Dkt. No. 4855.147WO1 Client Reference No. 0975PCT01CLAIMSWhat is claimed is:

1. An analyte sensor system, comprising:an electrochemical aptamer-based biosensor configured for use in sensing a target analyte, the biosensor including a substrate, a reversible redox probe, and an aptamer; andsensor electronics configured to perform operations comprising:interrogating the biosensor to determine a current response; determining an adjusted current value to correct for at least one of pH or temperature; anddetermining an estimated analyte value for the target analyte based on the adjusted current value.

2. The analyte sensor system according to claim 1, wherein the aptamer is configured to change upon binding with a target analyte to change an electron transfer rate between the redox probe and the substrate.

3. The analyte sensor system according to any of claims 1-2, wherein the determining the adjusted current value includes receiving a temperature signal indicative of a temperature measurement and determining a temperature-corrected current value based on the temperature signal.

4. The analyte sensor system according to any of claimsl-3, wherein the determining the adjusted current value includes receiving a pH signal indicative of a pH measurement and determining a pH-corrected current value based on the pH signal.

5. The analyte sensor system according to any of claims 1-4, wherein the interrogating the biosensor further includes applying an electrical stimulus the biosensor and measuring an electrical response to the electrical stimulus, and the determining the adjusted current value includes inferring a pH measurement from the electrical response.Atty. Dkt. No. 4855.147WO1 Client Reference No. 0975PCT016. The analyte sensor system according to claim 5, wherein the biosensor includes a working electrode, the applying the electrical stimulus to the biosensor includes applying a voltage profile to the working electrode as a function of time, and the electrical response includes an electrical response to the applied voltage profile.

7. The analyte sensor system according to claim 6, wherein the biosensor is interrogated by applying the voltage profile using a voltammetry technique, the electrical response to the voltage profile includes a peak voltage measure, and the pH measurement is inferred using at least the peak voltage measure.

8. The analyte sensor system according to claim 7, wherein the electrical response to the voltage profile further includes a peak current measure, the sensor electronics are configured to determine the adjusted current value based on the peak voltage measure and the current response, and an estimated analyte value for the target analyte is determined based on the adjusted current value.

9. The analyte sensor system according to any of claims 5-8, wherein the biosensor includes a working electrode and a reference electrode, the electrical stimulus applied to the biosensor includes applying an open-circuit potential between working and reference electrodes of the biosensor, and the electrical response includes an electrical response to the open-circuit potential, and the pH measurement is inferred using the open-circuit potential.

10. The analyte sensor according to any of claims 1,-9 wherein the adjusted current value is determined to correct for both pH and temperature.

11. The analyte sensor according to any of claims 1-10, wherein:the interrogating the biosensor includes applying a voltammetry’ technique, determining both a raw peak current and a raw peak voltage for the applied voltammetry’ technique; andthe determining the adjusted current value includes determining a current correction factor based on the raw peak voltage, and determining the adjusted current value based on the raw peak current and the current correction factor.Atty. Dkt. No. 4855.147WO1 Client Reference No. 0975PCT0112. The analyte sensor of claim 11, wherein the current correction factor is determined using the raw peak voltage.

13. The analyte sensor according to any of claims 11-12, wherein regression analysis is applied to at least one of bench data or in vivo data to determine the current correction factor for the raw peak voltage.

14. The analyte sensor according to any of claims 11-13, wherein the current correction factor is determined using a linear function.

15. The analyte sensor according to any of claims 11-13, wherein the current correction factor is determined using a nonlinear function.

16. The analyte sensor according to any of claims 11-13, wherein the current correction factor is determined using a piecewise function.

17. The analyte sensor according to any of claims 11-13, wherein the adjusted current value is determined using a lookup table to look up the current correction factor based on the raw peak voltage.

18. The analyte sensor according to claim 17, wherein the adjusted current value is determined using a lookup table to look up the current correction factor based on the raw peak current, the raw peak voltage and a temperature.

19. The analyte sensor according to any of claims 1-18, wherein:the interrogating the biosensor includes applying a voltammetry' technique, determining both a raw peak current and a raw peak voltage for the applied voltammetry technique; andthe determining the adjusted current value includes receiving a temperature signal from a temperature sensor, determining a temperature-corrected peak current using the temperature signal and the raw peak current, determining a temperature-corrected peak voltage using the temperature signal and the raw peak voltage, determining a current correction factor based on theAtty. Dkt. No. 4855.147WO1 Client Reference No. 0975PCT01temperature-corrected peak voltage, and determining the adjusted current value using the temperature-corrected peak current and the current correction factor.

20. The analyte sensor according to claim 19, wherein the current correction factor is determined using a peak current-voltage correlation.

21. The analyte sensor according to any of claims 19-20, further comprising normalizing the temperature-corrected peak current to provide a normalized peak current, wherein the adjusted current value is determined using the normalized peak current and the current correction factor.

22. A method of determining an in vivo concentration of an analyte, the method comprising:contacting, in vivo, a biological fluid comprising an analyte with an aptamer from an electrochemical aptamer-based biosensor;interrogating the biosensor using voltammetry to determine biosensor responses, wherein the biosensor responses include both a current response and a voltage response;determining an adjusted current value based on the current response and the voltage response; anddetermining an estimated analyte value for the analyte based on the adjusted current value.

23. The method according to claim 22, wherein the aptamer changes upon binding with a target analyte to change an electron transfer rate between a redox probe and a substrate.

24. The method according to any of claims 22-23, wherein the determining the adjusted current value includes receiving a temperature signal indicative of a temperature measurement and determining a temperature-corrected current value based on the temperature signal.

25. The method according to any of claims 22-24, wherein the determining the adjusted current value includes receiving a pH signal indicative of a pHAtty. Dkt. No. 4855.147WO1 Client Reference No. 0975PCT01measurement and determining a pH-corrected current value based on the pH signal.

26. The method according to any of claims 22-25, wherein the interrogating the biosensor further includes applying an electrical stimulus the biosensor and measuring an electrical response to the electrical stimulus, and the determining the adjusted current value includes inferring a pH measurement from the electrical response.

27. The method according to claim 26, wherein the applying the electrical stimulus to the biosensor includes applying a voltage profile to a working electrode of the biosensor as a function of time, and the electrical response includes an electrical response to the applied voltage profile.

28. The method according to claim 27, wherein the interrogating the biosensor includes applying the voltage profile using a voltammetry technique, the electrical response to the voltage profile includes a peak voltage measure, and the pH measurement is inferred using at least the peak voltage measure.

29. The method according to any of claims 27-28, wherein the measuring the electrical response includes measuring a peak current, and the determining the adjusted current value includes using a peak voltage measure and the current response, and an estimated analyte value for the analyte is determined based on the adjusted current value.

30. The method according to any of claims 26-29, wherein the applying the electrical stimulus applied to the biosensor includes applying an open-circuit potential between a working electrode and a reference electrode of the biosensor, and the electrical response includes an electrical response to the open-circuit potential, and the pH measurement is inferred using the open-circuit potential.

31. The method according to any of claims 22-30, wherein the adj usted current value is determined to correct for both pH and temperature.Atty. Dkt. No. 4855.147WO1 Client Reference No. 0975PCT0132. The method according to any of claims 22-31, wherein:the interrogating the biosensor includes applying a voltammetry’ technique, determining both a raw peak current and a raw peak voltage for the applied voltammetry technique; andthe determining the adjusted current value includes determining a current correction factor based on the raw peak voltage, and determining the adjusted current value based on the raw peak current and the current correction factor.

33. The method according to claim 32, wherein the determining the adjusted current value includes using the raw peak voltage to determine a function, and determining the adjusted current value using the raw peak current and the function.

34. The method according to claim 33, further comprising applying regression analysis to at least one of bench data or in vivo data to determine the function.

35. The method according to claim 33, wherein the function includes a linear function.

36. The method according to claim 33, wherein the function includes a nonlinear function.

37. The method according to claim 33, wherein the function includes a piecewise function.

38. The method according to claim 32, wherein the determining the adjusted current value includes using at least one lookup table to determine the adjusted current values based on both the raw peak current and the raw peak voltage.

39. The method according to claim 38. wherein the determining the adjusted current value includes using at least one lookup table to determine the adjusted current values based on the raw peak current, the raw peak voltage and a temperature.Atty. Dkt. No. 4855.147WO1 Client Reference No. 0975PCT0140. The method according to any of claims 22-39, wherein:the interrogating the biosensor includes applying a voltammetry’ technique, the cunent response includes a raw peak current for the applied voltammetry technique and the voltage response includes a raw peak voltage for the applied voltammetry’ technique; andthe determining the adjusted current value includes receiving a temperature signal from a temperature sensor, determining a temperature-corrected peak current using the temperature signal and the raw peak current, determining a temperature-corrected peak voltage using the temperature signal and the raw peak voltage, determining a current correction factor based on the temperature-corrected peak voltage, and determining the adjusted current value using the temperature-corrected peak current and the current correction factor.

41. The method according to claim 40, wherein the current correction factor is determined using a peak current-voltage correlation.

42. The method according to any of claims 40-41, further comprising normalizing the temperature-corrected peak current to provide a normalized peak current, wherein the adjusted current value is determined using the normalized peak current and the current correction factor.

43. A non-transitory computer readable medium storing instructions, which when executed by at least one data processor, result in operations comprising: interrogating an electrochemical aptamer-based biosensor using voltammetry to determine biosensor responses, wherein an aptamer of the biosensor contacts, in vivo, a biological fluid comprising an analyte, and the biosensor responses include both a current response and a voltage response; determining an adjusted current value based on the current response and the voltage response; anddetermining an estimated analyte value for the analyte based on the adjusted current value.

44. The non-transitory computer readable medium storing instructions, wherein the operations include a method recited in any one of claims 23 to 42.

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