Electrochemical device and method for accurate determination of an analyte

Abstract

The present disclosure provides an apparatus, system, and method that can optimize in vivo electrochemical measurements of a target molecule, such as glucose. The disclosed embodiments can include an interference zapping layer to which a potential can be applied to prevent or minimize the arrival of various interfering molecules at the working electrode. Embodiments of the present disclosure can additionally or alternatively include a sensor that includes a plurality of working electrodes. A sensor having a plurality of working electrodes can measure a background current during sensing to determine the background current, current due to electrochemically interfering substances, and current due to the target molecule, specific to each electrode. The sensor can also execute a measurement mode in which a plurality of currents are measured over a range of interference zapping layer potentials and a range of working electrode potentials.

Description

Technical Field

[0001] Incorporation by reference to priority applications In any application in which a foreign or domestic priority claim is identified in the application data sheet filed with this application, all such applications are incorporated herein by reference under 37 CFR § 1.57. For example, this application claims priority to U.S. Provisional Patent Application No. 63 / 368,754, filed Jul. 18, 2022, and U.S. Provisional Patent Application No. 63 / 487,352, filed Feb. 28, 2023, the entire contents of which are hereby incorporated by reference in their entirety for all purposes and form a part of this specification.

[0002] This disclosure relates to continuous glucose monitoring (CGM). More specifically, it relates to CGM sensors.

Background Art

[0003] Continuous glucose monitoring (CGM) sensors based on electrochemical methods may be capable of detecting glucose by indirect measurement of molecules generated during an enzymatic reaction. Enzyme products can be, by way of example, hydrogen peroxide, artificial mediators, and / or the reduced enzyme cofactor itself. A common aspect of all these measurements is the application of an electrochemical potential sufficient to oxidize these molecules to generate a current.

Summary of the Invention

Problems to be Solved by the Invention

[0004] The devices, systems, and methods of this disclosure each have several innovative aspects, and no single one of them alone bears its desirable attributes. Without limiting the scope of this disclosure, its more prominent features are described herein.

Means for Solving the Problems

[0005] Aspects of the present disclosure relate to electrochemical probes. The electrochemical probe can include an electrode, an enzyme layer, and an interference zapping layer.

[0006] In some aspects, the probe can further include a glucose restriction layer. In some aspects, the electrode can measure glucose concentration. In some aspects, the enzyme layer can convert glucose into hydrogen peroxide and gluconic acid. In some aspects, the enzyme layer includes glucose oxidase. In some aspects, the probe includes a blocking layer. In some aspects, the blocking layer can include a size-based filter or an electrostatic repulsion filter. In some aspects, the probe can include a voltage source capable of setting the electrode to an applied potential of +0.1 to +1 V. In some aspects, the probe can include a voltage source capable of setting the electrode to an applied potential of +0.6 to +0.7 V. In some aspects, the probe can include a voltage source capable of setting the interference zapping layer to an applied voltage of +0.3 to +1 V. In some aspects, the probe can include a voltage source capable of setting the interference zapping layer to an applied voltage of +0.7 to +0.8 V. In some aspects, the probe can include a first voltage source capable of setting the electrode to a first applied potential and a second voltage source capable of setting the interference zapping layer to a second applied potential, and the second applied potential can be greater than or equal to the first applied potential. In some aspects, the interference zapping layer can include a hydrogel. In some aspects, the interference zapping layer can include a micro wire. In some aspects, the interference zapping layer can include a micro wire network. In some aspects, the interference zapping layer can include a nano wire. In some aspects, the interference zapping layer can include a nano wire network. In some aspects, the interference layer can include cellulose acetate cross-linked with citric acid. In some aspects, a continuous glucose monitor can include an electrochemical biosensor probe according to the present disclosure.

[0007] Aspects of the present disclosure relate to probes. A probe can include a first electrode in contact with a first enzyme layer, a second electrode, and a first interference zapping layer outside the first electrode and the second electrode. In some aspects, the probe can include an insulating substrate disposed under the first electrode and the second electrode. In some aspects, the probe can include a third electrode in contact with a second enzyme layer. In some aspects, the probe can include a second enzyme layer in contact with the second electrode and a first polymer layer outside the first interference zapping layer. In some aspects, the probe can include a second interference zapping layer outside the first polymer layer and a second polymer layer outside the second interference zapping layer. In some aspects, the probe can include a first enzyme layer containing glucose oxidase and a second enzyme layer containing catalase.

[0008] Aspects of the present disclosure relate to a method of using a probe. The method includes applying a first potential to an interference layer, the first potential being sufficient to oxidize at least one electrochemical interfering substance and a target molecule; measuring a first background current of a first electrode; measuring a second background current of a second electrode; applying a second potential to the interference layer, the second potential being sufficient to oxidize at least one electrochemical interfering substance but not sufficient to oxidize the target molecule; measuring a first current of the first electrode; measuring a second current of the second electrode; and determining an estimated concentration of the target molecule based at least in part on the measured values of the first background current, the second background current, the first current, and the second current. In some aspects, the target molecule includes glucose. In some aspects, the first potential can be within +0.5 to +1.5 V. In some aspects, the first potential can be within +0.6 to +1.1 V. In some aspects, the first potential can be within +0.1 to +0.9 V. In some aspects, the second potential can be within +0.3 to +1.1 V. In some aspects, the second potential can be within +0.4 to 0.7 V. In some aspects, the second potential can be within +0.1 to +0.9 V.

[0009] Aspects of the present disclosure relate to a method of using an electrochemical probe including an interference zapping layer and a working electrode. The method includes applying a first plurality of potentials to the interference zapping layer; applying a second plurality of potentials to the working electrode; measuring a plurality of currents of the working electrode, each of the plurality of currents being measured while the interference zapping layer can be set to one of the first plurality of potentials and while the working electrode can be set to one of the second plurality of potentials; and determining an estimated concentration of an analyte based at least in part on the measured plurality of currents using a hardware processor.

[0010] In some embodiments, the method may include determining an estimated concentration of a plurality of analytes based at least in part on the plurality of measured currents. In some embodiments, the step of applying a first plurality of potentials to the interference layer includes sequentially applying the first plurality of potentials. In some embodiments, the step of applying a second plurality of potentials to the working electrode includes sequentially applying the second plurality of potentials. In some embodiments, each of the plurality of currents may be measured with a different combination of one of the first plurality of potentials and one of the second plurality of potentials. In some embodiments, the first plurality of potentials may be a series of potentials having a step of Δ±0.1 V between each of the first plurality of potentials. In some embodiments, the second plurality of potentials may be a series of potentials having a step of Δ±0.1 V between each of the first plurality of potentials. In some embodiments, while the interference layer may be held at one of the first plurality of potentials, the potential applied to the working electrode changes stepwise between the second plurality of potentials. In some embodiments, while the working electrode may be held at one of the second plurality of potentials, the potential applied to the interference electrode changes stepwise between the first plurality of potentials. In some embodiments, the method does not include a calibration step.

[0011] Aspects of the present disclosure relate to a method of using an electrochemical probe comprising an interference zapping layer and a working electrode, the method comprising applying a first plurality of potentials to the interference zapping layer, applying a second plurality of potentials to the working electrode, measuring a first plurality of currents of the working electrode, each of the first plurality of currents being measured while the interference zapping layer is set to one of the first plurality of potentials and the working electrode is set to one of the second plurality of potentials, determining, using a hardware processor, a third plurality of potentials, the third plurality of potentials including at least a portion of the first plurality of potentials, determining, using a hardware processor, a fourth plurality of potentials, the fourth plurality of potentials including at least a portion of the first plurality of potentials, and measuring a second plurality of currents of the working electrode, each of the second plurality of currents being measured while the interference zapping layer is set to one of the third plurality of potentials and the working electrode is set to one of the fourth plurality of potentials.

[0012] In some aspects, the third plurality of potentials consists of at least one of the first plurality of potentials and the fourth plurality of potentials consists of at least one of the second plurality of potentials. In some aspects, the step of determining the third plurality of potentials may be at least partially based on the first plurality of currents indicative of an analyte. In some aspects, the step of determining the fourth plurality of potentials may be at least partially based on the first plurality of currents indicative of an analyte. In some aspects, the second plurality of currents includes fewer currents than the first plurality of currents. In some aspects, the step of measuring the second plurality of currents may be faster than the step of measuring the first plurality of currents. In some aspects, the step of measuring the second plurality of currents may require less power than the step of measuring the first plurality of currents.

[0013] Aspects of the present disclosure relate to a method of using an electrochemical probe comprising an interference zapping layer and a working electrode, the method comprising applying a first plurality of potentials to the interference zapping layer, applying a second plurality of potentials to the working electrode, measuring a plurality of currents of the working electrode, each of the plurality of currents being measured while the interference zapping layer is set to one of the first plurality of potentials and while the working electrode is set to one of the second plurality of potentials, constructing a data structure using a hardware processor, and determining an estimated analyte concentration at least partially based on the data structure using the hardware processor.

[0014] In some aspects, the method includes displaying the analyte concentration on a display. In some aspects, the data structure is an array. In some aspects, the data structure is a heat map. In some aspects, the data structure is a three-dimensional plot. In some aspects, determining the estimated analyte concentration includes comparing the data structure to a control data structure. In some further aspects, the control data structure includes measured current values of a control object. In some further aspects, the control data structure includes measured current values of a control fluid. In some aspects, the control data structure includes previous measured values of a plurality of previous currents of a patient. In some aspects, the method includes identifying a physiological change using a hardware processor at least partially based on a difference between the data structure and the previous measured values. In some aspects, the method includes placing the interference zapping layer and the working electrode within the interstitial fluid of a patient.

[0015] Here, the above aspects of the embodiments of the present disclosure, as well as other features, aspects, and advantages, are described in connection with various embodiments and / or implementations with reference to the accompanying drawings. The illustrated embodiments are merely examples and are not intended to be limiting. Throughout the drawings, like reference numerals typically identify like components unless the context dictates otherwise.

Brief Description of the Drawings

[0016]

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Mode for Carrying Out the Invention

[0017] Aspects of the present disclosure provide devices, systems, and methods that can optimize in vivo electrochemical measurements of target molecules and / or analytes, such as glucose. Such aspects can include an interference zapping layer to which a potential can be applied to prevent or minimize the arrival of various interfering molecules at the working electrode. Aspects of the present disclosure can additionally or alternatively include a sensor that includes three electrodes. These electrodes can dynamically measure the background current during sensing to determine the current due to electrochemical interferents and the current due to the target molecule.

[0018] Electrochemical Interferents and Background Current In a specific example where an electrochemical sensor can sense an analyte concentration such as, for example, glucose concentration, the enzymatic conversion can produce hydrogen peroxide from glucose at an electrode, for example, a platinum electrode. As a result, the concentration of hydrogen peroxide corresponds to the glucose concentration. Figure 1 shows the conversion from glucose to gluconic acid. The enzymatic conversion from glucose to gluconic acid and hydrogen peroxide can be achieved, for example, by glucose oxidase.

[0019] To enable the detection of hydrogen peroxide, the electrode may require an applied potential of, for example, +0.6 to 0.7 V with respect to the working electrode, for example, Ag / AgCl. In a specific example, the electrochemical potential of the sensor electrode can be in the range of 0.0 to +0.7 V with respect to Ag / AgCl. Under certain conditions, the current generated by the oxidation of hydrogen peroxide that produces H2O and O2 at the applied potential can be directly correlated with the glucose concentration.

[0020] However, in body fluids, there are other molecules that can come into contact with the sensor and undergo an electrochemical reaction at the electrode surface within these potential ranges. When these other molecules undergo an electrochemical reaction, they can generate a background current that can be read by the sensor electrode. The molecules that cause these background currents are referred to herein as "electrochemical interferents" or "interferents". Some electrochemical interferents can naturally exist in body fluids and / or be produced by cells and released into body fluids (e.g., ascorbic acid, uric acid, reactive oxygen species, etc.), while some are introduced by ingestion (e.g., acetaminophen, ibuprofen, ascorbic acid). Fluctuations in the concentration of electrochemical interferents in body fluids can result in fluctuations in the background signal being sensed, due to either normal physiological processes or external factors including ingestion. Without means to eliminate electrochemical interferents, the current resulting as a measurement at the working electrode can be a convolution of all electroactive molecules, including hydrogen peroxide generated by, for example, the glucose oxidase enzyme. Thus, fluctuations in the background signal can lead to an incorrect estimation of the target molecule concentration in the body fluid, e.g., glucose concentration. Thus, in the case of analyte sensing, for example, for glucose sensing, it may be desirable to minimize the oxidation of molecules other than hydrogen peroxide at the electrode.

[0021] One way to overcome this problem could be to modify the surface of the sensor so as to prevent interferents from reacting at the electrode surface. For example, existing strategies for excluding interfering molecules include using the electrostatic repulsion properties of charged molecules, such as ascorbic acid and / or uric acid, and / or size-based filtering of neutrally charged molecules, such as acetaminophen. Such blocking can be passive. However, these strategies can have drawbacks. For example, size-based exclusion strategies may not block endogenous hydrogen peroxide or other reactive oxygen species (ROS) that are products of normal physiological function. Additionally, during continuous operation, the blocking layer can break down and lead to a higher background current.

[0022] Figure 2 shows an exemplary configuration of a sensor 300 that illustrates a technique for eliminating interfering molecules using a blocking layer. The exemplary electrochemical sensor 300 includes one or more working electrodes 202, a blocking layer 204, an enzyme layer 206, and an analyte confinement layer 208. The working electrode 202 may include a metal material, such as platinum. The blocking layer 204 may include a porous material having pores of a size small enough to allow the passage of target molecules but large enough to prevent the passage of molecules larger than the molecule of interest. Additionally or alternatively, the blocking layer 204 can incorporate an electrostatic charge that allows the passage of target molecules but blocks molecules having a charge different from the molecule of interest. The enzyme layer 206 may include an enzyme, such as glucose oxidase, for converting a molecule of interest, such as glucose, into a target molecule, such as hydrogen peroxide.

[0023] During operation, the electrode can be maintained at an appropriate applied potential, such as a potential in the range of +0.6 to 0.7 V. At this potential, hydrogen peroxide can be generated by the enzyme layer 206 as a byproduct of the conversion of glucose to gluconic acid. At the working electrode 202, hydrogen peroxide can be oxidized to generate a current that can be at least partially proportional to the glucose concentration.

[0024] To remove interfering molecules, the blocking layer 204 can act to filter molecules based on size exclusion or by leveraging molecular properties such as electrostatic charges on interfering molecules at physiological pH. The order of the blocking layer 204 and the enzyme layer 206 can be interchanged depending on the application (e.g., the enzyme layer 206 can be close to the working electrode 202, and the blocking layer 204 can be laminated outside the enzyme layer 206). The third layer, i.e., the analyte confinement layer 208, can generate target molecules by proportionally equalizing the molar concentrations of the analyte and the reactants involved in the enzyme reaction. In an embodiment where the analyte confinement layer 208 is a glucose confinement layer (e.g., in the case of a glucose sensor), the analyte confinement layer 208 can proportionally equalize the molar concentrations of glucose and oxygen in the enzyme layer, shifting the enzyme reaction to be glucose-dependent. When the electrode operates under typical physiological conditions, there can be 100 - 1000 times more glucose than oxygen molecules. It may be desirable for the analyte confinement layer 208 to be manufactured to surround the enzyme layer 206 so that it can effectively proportionally equalize the molar concentrations of glucose and oxygen in the enzyme layer 206.

[0025] Another approach can be to use an additional electrode without an enzyme layer to measure the current from background interferents. However, this strategy often cannot accurately estimate the glucose concentration by simply subtracting the interference current (measured by the electrode without the enzyme layer) from the signal current (measured by the electrode with the enzyme layer). This failure results from the assumption that the background currents of both electrodes are the same value, which may not be true. The true background of any two electrodes can vary for several reasons, including slight differences in their surface roughness, history of chemical or biological modification, time-dependent adsorption of species, and changes received during exposure to biological fluids during sensing. These problems can cause relatively large errors when the current signal is small compared to the background current, as is the case with CGM sensors.

[0026] Summary This specification discloses sensors and electrochemical methods for addressing the above problems. The sensors can be inserted into a patient's body. The sensors according to the present disclosure can be inserted into a patient's body so as to contact the patient's body fluid. For example, the sensors according to the present disclosure can be inserted into a patient's body so as to at least partially contact the patient's interstitial fluid. For example, the sensors according to the present disclosure may be inserted into a patient's body so as to contact the patient's blood.

[0027] In one aspect, the present disclosure provides for including a novel interference zapping layer around and / or on the working electrode of a CGM sensor. The interference zapping layer utilizes the electroactivity of an electrochemically interfering substance to filter out and remove interfering molecules before reaching the enzyme layer and / or the working electrode. Thereby, the interference zapping layer can eliminate electrochemically interfering substances.

[0028] In another aspect, the present disclosure provides a sensor including three electrodes for dynamically measuring the background current of each electrode during the sensing duration, for measuring the contribution by electrochemically interfering substances, and for accurately estimating the glucose concentration in the target biological fluid using these measured values.

[0029] In another aspect, the present disclosure provides for optionally including a wetting layer in the sensor according to the present disclosure. Such a wetting layer can promote the hydration of the sensor, thereby shortening the "warm-up" period after the sensor is inserted into the patient.

[0030] In yet another aspect, the present disclosure provides a method, herein referred to as the "measurement mode", for measuring the concentration of one or more analytes using a probe having an interference zapping layer according to the present disclosure.

[0031] This disclosure discusses the enzymatic conversion of glucose that produces hydrogen peroxide that can be subsequently detected by an electrode, but one of ordinary skill in the art will recognize that the concepts disclosed herein can be applied to the sensing of other target molecules. For example, the present disclosure may be generally applicable to any electrochemical sensor that (1) operates at an applied potential, (2) includes a metal at the working electrode, and / or (3) includes one or more chemical layers within the sensor.

[0032] Interference zapping layer In one aspect, the present disclosure provides for the use of an interference zapping layer that utilizes the oxidizability of various electrochemical interferents to prevent them from reaching the working electrode, for example, by diffusion.

[0033] In normal human physiology, there are many interfering molecules that are electrochemically oxidizable at various voltages ranging from 0 to +1 V. For a given electroactive molecule, the electroactive molecule can be oxidized by maintaining a potential slightly higher than its peak potential. The peak potential can be determined by voltammetry as described in Naghian, E. et al., Carbon paste electrodes modified with SnO2 / CuS, SnO2 / SnS and Cu@SnO2 / SnS nanocomposites as voltammetric sensors for paracetamol and hydroquinone, Microchimica Acta 185, 406 (2018). The local peaks of the eight interfering molecules tested by Naghian et al. using the measured voltammetry are in the approximate range of 0 to +1 V.

[0034] The interference zapping layer can enable adjustable control over the access of molecular species to the working electrode. For example, in contrast to a blocking layer that can only passively block interferents based on size and / or charge and cannot be adjusted during use, the potential of the interference zapping layer can be adjustable even during probe use.

[0035] The interference zapping layer according to the present disclosure can utilize the oxidizing properties of electrochemically interfering substances. For example, the interference zapping layer can oxidize all, substantially all, and / or many molecules that are electrochemically active. The efficiency of the interference zapping layer can depend on the applied voltage and the density of the wire network of the interference zapping layer. As described in accordance with the present disclosure, both the wire network density and the voltage can be controlled. When the applied potential at the interference zapping layer is above the operating potential of the analyte sensing electrode and the wire network is sufficiently dense, all, substantially all, and / or many electrochemically interfering substances can be blocked before reaching the sensing electrode. The interference zapping layer can also efficiently block unknown, poorly understood, and / or novel interfering molecules.

[0036] As an exemplary example of blocking by the interference layer, hydrogen peroxide can be endogenously produced as a byproduct of metabolism and / or inflammation. Endogenous hydrogen peroxide is not substantially blocked by either size-based or charge-based blocking layer approaches. However, the interference zapping layer constructed in accordance with the present disclosure can substantially block by oxidizing hydrogen peroxide molecules that leave the underlying enzyme layer outward and / or can oxidize endogenously produced hydrogen peroxide molecules that diffuse inwardly into the interference zapping layer. The rate at which the interference zapping layer blocks hydrogen peroxide can depend on its and other layers' geometries, wire network density, and / or other factors.

[0037] In some examples, the zapping layer can block interfering molecules for a glucose sensing electrode that operates at a lower potential, e.g., +0.1 to +0.4 V versus Ag / AgCl. In these examples, the applied potential of the interference zapping layer can be held at +0.45 V versus Ag / AgCl or some other suitable voltage.

[0038] Sensor including an interference zapping layer In some examples, sensor 300 includes at least three chemical / biochemical layers, each of which may perform a specific function. For example, the three functions may include biochemical conversion (performed by an enzyme), equilibration of reactants (performed by an analyte restriction layer), and filtration (by electrochemical oxidation performed by an interference zapping layer disclosed herein).

[0039] Figures 3A, 3B, and 3C diagram exemplary layering schemes for sensor 300. The exemplary sensor 300 shown in Figure 3A includes a sensing electrode 202 (also referred to as a working electrode), an enzyme layer 206, an analyte restriction layer 208, and an interference zapping layer 302. The exemplary sensor 300 shown in Figure 3B includes the same types of layers, but the order of the analyte restriction layer 208 and the interference zapping layer 302 may be switched. Different from Figure 3A, the analyte restriction layer 208 of Figure 3B may be outside the analyte restriction layer 208. In some embodiments, the interference zapping layer 302 may be the outermost layer of the sensor 300, as shown in Figure 3A. In some embodiments, the interference zapping layer 302 may be between the analyte restriction layer 208 and the enzyme layer 206, as shown in Figure 3B.

[0040] The exemplary sensor 300 shown in Figure 3C includes, from the innermost to the outermost, a sensing electrode 202, a blocking layer 204, an enzyme layer 206, an analyte restriction layer 208, and an interference zapping layer 302. Other exemplary sensors including the layers shown in Figure 3C may have the layers rearranged as described in this disclosure. In some embodiments, the enzyme layer 206 may include polyurethane, polyethylene glycol diglycidyl ether, and / or polyethylene diamine. In some embodiments, the enzyme layer 206 may include an enzyme capable of generating a target molecule from the analyte of interest. In some embodiments, the enzyme of the enzyme layer 206 may be glucose oxidase. In some embodiments, the analyte restriction layer 208 may include polyurethane.

[0041] The interference zapping layer 302 can be at least partially conductive. As described in more detail herein, the interference zapping layer 302 can include a conductive wire network, such as a micro wire network and / or a nano wire network. The micro wire network can include wires having a diameter of approximately 1 μm to 1 mm. The nano wire network can include wires having a diameter of approximately 1 nm to 1 μm. In the above example, by applying a voltage to the interference zapping layer 302 laminated outside the enzyme layer 206, an electrochemically interfering substance can be oxidized, thereby blocking it from the sensing electrode 202. The interference zapping layer 302 can be conductive to facilitate the application of a potential. In some embodiments, the sensing electrode 202 can be held at a potential of approximately 0.0 to +2.0 V, approximately 0.0 to +1.75 V, approximately 0.0 to +1.5 V, approximately 0.0 to +1.25 V, approximately 0.0 to +1.0 V, approximately 0.0 to +0.9 V, approximately 0.0 to +0.8 V, approximately 0.0 to +0.7 V, approximately 0.0 to +0.6 V, approximately 0.0 to +0.5 V, approximately 0.0 to +0.4 V, approximately +0.1 to +1.0 V, approximately +0.1 to +0.4 V, approximately +0.6 to +0.7 V, or any value or range within any of these ranges or values, or any value or range limited by any of these ranges or values, although in some cases values outside of these values or ranges can also be used.

[0042] In certain embodiments, the interference zapping layer 302 can be held at an applied potential similar to that of the sensing electrode 202, such as +0.6 to +0.7 V, or slightly higher than that, such as +0.7 to 0.8 V. The interference zapping layer 302 can be in an electrochemical circuit independent of the sensing electrode 202, as shown in FIGS. 4A, 4B, and 4C. The exemplary sensor of FIG. 4A schematizes the circuit of the sensor of FIG. 3A. The exemplary sensor of FIG. 4B schematizes the circuit of the sensor of FIG. 3B. The exemplary sensor of FIG. 4C schematizes the circuit of the sensor of FIG. 3C. The applied electrode potential 402 and the applied interference zapping layer potential 404 can be independent. In some embodiments, the interference zapping layer 302 can be held at a potential of approximately 0.0 to +2.0 V, approximately 0.0 to +1.75 V, approximately 0.0 to +1.5 V, approximately 0.0 to +1.25 V, approximately 0.0 to +1.0 V, approximately 0.0 to +0.9 V, approximately 0.0 to +0.8 V, approximately 0.0 to +0.7 V, approximately 0.0 to +0.6 V, approximately 0.0 to +0.5 V, approximately 0.0 to +0.4 V, approximately +0.1 to +1.0 V, approximately +0.1 to +0.4 V, approximately +0.2 to +0.5 V, approximately +0.3 to +0.6 V, approximately +0.6 to +0.7 V, approximately +0.7 to +0.8 V, or any value or range within any of these ranges or values, or any value or range limited by any of these ranges or values, although in some cases values outside of these values or ranges can also be used.

[0043] In some embodiments, the analyte confinement layer 208 can be 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, or 15 μm thick, or within a range defined by any of the foregoing values. In some embodiments, the thickness of the analyte confinement layer 208 can be 2 to 10 μm. Increasing the thickness of the analyte confinement layer 208 can block more glucose. Increasing the thickness of the analyte confinement layer 208 can potentially decrease the current measured by the electrode 202.

[0044] In some embodiments, the enzyme layer 206 can have a thickness of 0.5, 1.0, 1.5, 2.0, 2.5, 3.0, 3.5, 4.0, 4.5, 5.0, 5.5, 6.0, 6.5, 7.0, 7.5, 8.0, 8.5, 9.0, 9.5, or 10.0 μm, or can be within a range defined by any of the foregoing values. In some embodiments, the thickness of the enzyme layer 206 can be 1-5 μm.

[0045] In some embodiments, the interference blocking layer 302 can have a thickness of 0.5, 1.0, 1.5, 2.0, 2.5, 3.0, 3.5, 4.0, 4.5, 5.0, 5.5, 6.0, 6.5, 7.0, or 7.5 μm, or can be within a range defined by any of the foregoing values. In some embodiments, the thickness of the interference blocking layer 302 can be 2-5 μm.

[0046] Composition and Manufacture of the Interference Zapping Layer The interference zapping layer 302 can be fabricated by any of a number of suitable methods. The interference zapping layer 302 can include conductive elements, such as wires, for example, micro-wires or nano-wires. The interference zapping layer 302 can be an electrode that allows diffusion of molecules therethrough. In one example, the wire can be assembled outside the sensing electrode 202 either parallel to the length of the sensing electrode 202 or in a coil around the sensing electrode 202. The wire can be arranged such that there is a suitable separation so that diffusion of the analyte to the underlying electrode is not hindered. The wire can be arranged, for example, as a network. As another example, the zapping layer can be constructed by embedding a wire network, such as a platinum nano-wire network, in a polymer matrix. This method may be desirable as it may be suitable for large-scale manufacturing. The wire, wire network and / or interference zapping layer can be synthesized according to the procedures described in Shi, Q. et al., Mesoporous Pt Nanotubes as a Novel Sensing Platform for Sensitive Detection of Intracellular Hydrogen Peroxide, Acs Appl Mater Inter 7, 24288-95 (2015) and Shi, Q. et al., Kinetically controlled synthesis of AuPt bi-metallic aerogels and their enhanced electrocatalytic performances, J Mater Chem A 5, 19626-31 (2017), which are incorporated herein by reference. The wire network can be incorporated into a polymer matrix, such as a hydrogel or any other suitable material, such that the wire network can be deposited as a self-standing interference zapping layer 302. The wire can be arranged within the interference zapping layer 302 such that there is a suitable separation that allows diffusion of the molecule of interest to the underlying sensing electrode 202. In another exemplary manufacturing method, a conductive wire network can be coated with a colloidal suspension and subsequently coated with a polymer matrix to maintain its integrity.

[0047] In the exemplary sensors shown in FIGS. 3A, 3B, and 3C, the conductive nanomaterial network within the interference zapping layer 302 held at a given applied potential can oxidize all, substantially all, most, or some of the electrochemically interfering substances that are electroactive at or below the selected applied potential within and / or near the interference zapping layer 302, thereby preventing and / or suppressing at least some of the electrochemically interfering substances from reaching the working electrode 202 itself. In some examples, the molecule of interest may not be oxidizable at a particular applied potential. For example, glucose is not oxidizable at a particular applied potential, e.g., +0.7 to 0.8 V. At such a potential, at least some glucose may pass through the interference zapping layer even if at least some of the electrochemically interfering substances cannot pass through.

[0048] The density of the wire network within the interference zapping layer 302, such as a nanowire network and / or a micro wire network, can determine the effectiveness of excluding electrochemically interfering substances. Too low a density may not effectively exclude electrochemically interfering substances. However, if the density of the network is too high, the diffusion of all molecules, including the molecule of interest, such as glucose, may be hindered. The wire density can be controlled, for example, by increasing the concentration of the wires during the manufacture of the interference zapping layer 302. Additionally or alternatively, the wire density can be controlled by adding multiple interference zapping layers 302 to a single sensing electrode 202. Additionally or alternatively, the network density can be controlled by the selection of the polymer matrix included in the interference zapping layer 302. There are many off-the-shelf polymer matrix materials that can be biocompatible and potentially suitable for inclusion in the interference zapping layer 302. In some embodiments, the interference zapping layer 302 includes cellulose acetate.

[0049] In some embodiments, the interference zapping layer 302 may optionally include one or more crosslinking agents. As the thickness of the interference zapping layer 302 increases, it may be more effective in blocking electrochemical interfering substances. Increasing the thickness of the interference zapping layer 302 may make the interference zapping layer 302 more prone to cracking, but there is a possibility that the blocking efficiency may decrease. In embodiments where the interference zapping layer 302 contains cellulose acetate, the cellulose acetate may dissolve when exposed to the organic solvents used to form the other layers of the sensor. For this reason, it may become difficult to control the thickness uniformity of the interference zapping layer 302. In some embodiments, the interference zapping layer 302 may include a crosslinking agent between cellulose acetate and citric acid. In some embodiments, a one-step method involving a solid-state reaction can be used to introduce a crosslinking agent between cellulose acetate and citric acid. In some embodiments, the crosslinking reaction may proceed according to Scheme 1.

Chemical formula

[0050] The crosslinking reaction of Scheme 1 can proceed in about 40 minutes at 130 °C. The crosslinking reaction of Scheme 1 can be used for an interference zapping layer with a thickness of 2 - 5 μm. The interference zapping layer subjected to the crosslinking reaction according to Scheme 1 can have higher resistance to cracking and / or dissolution when exposed to organic solvents than the interference zapping layer without crosslinking.

[0051] Multi-electrode sensor In another aspect, the present disclosure provides for the use of a multi-electrode sensor for correcting background current.

[0052] Figure 5A shows an example of an exemplary multi - electrode sensor. The sensor includes electrodes for a proposed method to estimate and eliminate background current caused by interfering substances and to estimate the change in enzyme activity over time. Two electrodes 506a and 506b are located on an insulating substrate 502, and one porous electrode, namely the interference zapping layer 302, may be disposed directly above the two electrodes 506a and 506b. All three electrodes 302, 506a, and 506b can be independently electrochemically controlled. The porosity of the upper interference zapping layer 302 allows a target molecule in the body fluid 504, such as glucose, to diffuse through the interference zapping layer 302 to the sensing layer. One of the electrodes 506a can be associated with the enzyme layer 206. The enzyme layer 206 can convert a target molecule, such as glucose, into a target molecule that can be sensed by the electrode 506a, such as hydrogen peroxide. In an exemplary CGM sensor, the enzyme layer 206 can oxidize glucose in the presence of oxygen to release hydrogen peroxide. The target molecule can be detected at the surface of the underlying electrode 506a to generate a sensing signal. Another electrode 506b may be located adjacent to the electrode 506a. The electrode 506b may not have an associated enzyme layer. Thus, in an exemplary CGM sensor, the electrode 506b can provide a signal proportional to the current due to oxidation of substantially all, or a portion of, all of the electrochemical interfering substances in the body fluid within the sensor, excluding the target molecule. To ensure that the signal sensed by the electrode 506b does not correspond to the oxidation of the target molecule, it may be desirable to set the electrode 506b to a potential at which the target molecule cannot be electrochemically oxidized. For example, in the case where glucose can be the target molecule, it may be desirable to set the electrode 506b to +0.6 to +0.7 V. The third porous electrode disposed on the two electrodes 506a and 506b, namely the interference zapping layer 302, can eliminate electrochemical interfering substances by oxidizing the electrochemical interfering substances as disclosed herein when set to an appropriate potential, such as +0.6 to +0.7 with respect to Ag / AgCl. Additionally or alternatively, the interference zapping layer 302 can oxidize the target molecule and the electrochemical interfering substances when set to a relatively high potential.In embodiments where glucose can be the target molecule, by setting the interference zapping layer 302 higher than +0.8V with respect to Ag / AgCl, both glucose and electrochemical interfering substances can be oxidized.

[0053] Figure 5B shows an exemplary multi - electrode sensor. In addition to the elements described with reference to Figure 5A, the sensor of Figure 5B includes two electrodes 506a and associated enzyme layer 206. By including two electrodes 506a with enzyme layer 206, it becomes possible to read the average signal across the length of the sensor. For example, the two electrodes 506a may be capable of measuring the average signal due to glucose. In certain examples, more electrodes 506a and enzyme layer 206 and / or electrode 506b may be included in the sensor. By including multiple electrodes, the error in estimating the concentration of the target molecule, such as glucose, that may arise from the concentration gradient along the length of the sensor can be reduced or eliminated.

[0054] FIG. 5C shows an exemplary multi - electrode sensor. The exemplary sensor can be used to sense a target molecule, such as glucose. The sensor includes an insulating substrate 502, electrodes 506c and 506d, a catalase layer 510, an enzyme layer 512, a first interference - zapping layer 514a, a first polymer layer 516a, a second interference - zapping layer 514b, and a second polymer layer 516b. In some embodiments where the target molecule is glucose, the enzyme layer 512 can include glucose oxidase. The sensor can estimate and eliminate background current due to electro - chemical interferents and estimate the change in enzyme activity of the enzyme layer 512 over time. The two electrodes 506c and 506d can be located on the insulating substrate 502, and the two porous electrodes, namely the first interference - zapping layer 514a and the second interference - zapping layer 514b, can be located above the electrodes 506c and 506d. The two porous electrodes, namely the first interference - zapping layer 514a and the second interference - zapping layer 514b, can be separated by polymer layers, namely the first polymer layer 516a and the second polymer layer 516b, disposed above the two electrodes 506c and 506d. All four electrodes 506c, 506d, 514a, 514b are independently electrically controllable. The porosity of the interference - zapping electrodes 514a and 514b can allow the target molecule to diffuse through the enzyme layer 512. The composition of the first interference - zapping layer 514a and the second interference - zapping layer 514b can generally follow the composition of the interference - zapping layer as described herein.

[0055] The electrode 506d can be coated with the enzyme layer 512, where a target molecule, such as glucose, can undergo oxidation in the presence of oxygen to release a target molecule, such as hydrogen peroxide. The target molecule can be detected on the surface of the underlying electrode 506d, and hydrogen peroxide can generate a current corresponding to the concentration of the target molecule. The electrode 506c can be disposed adjacent to the electrode 506d, but can be coated with the catalase layer 510. The catalase layer 510 can prevent the target molecule from reaching the electrode 506c from the enzyme layer 512. It may be desirable to set the potential of the electrode 506c to a potential at which the target molecule cannot be electrochemically oxidized so that the signal sensed by the electrode 506c does not include or minimizes the signal of the electrode 506c due to the target molecule. In an embodiment where glucose is the target molecule, the potential of the electrode 506c can be set, for example, to +0.6 to +0.7 V to ensure that the signal sensed by the electrode 506c does not originate from and / or only minimally originates from the glucose concentration. Thus, the electrode 506c can provide a current signal proportional to all electrochemical interferents in the body fluid except the target molecule, such as glucose. The second interference zapping layer 514b located above the two electrodes 506c and 506d can oxidize the interferents when set to an appropriate potential, for example, a potential of approximately +0.6 V with respect to Ag / AgCl. The first interference zapping layer 514a can oxidize the target molecule, such as glucose and glucose-like molecules, when set to an appropriate potential, for example, approximately +0.6 V with respect to Ag / AgCl. Advantageously, the potential applied to the interference zapping layer can be relatively mild and can prevent and / or reduce the degradation of the polymer layer in contact with the interference zapping layer.

[0056] Calibration method for in vivo background interferents using a multi-electrode sensor FIG. 6 shows an exemplary method for calibrating for in vivo background interferents. The method of FIG. 6 can be applied to a sensor, such as the sensor schematized in FIG. 5A. In FIG. 6, the electrode 506a having an enzyme layer is Pt E, the electrode 506b without an enzyme layer is made of Pt B as shown in FIG. 6. Although specific potential values are disclosed, it should be understood that any potential can be used in the various steps disclosed to oxidize and / or eliminate specific target molecules, target molecules, and / or electrochemical interferents. Further, although glucose is an exemplary target molecule, those skilled in the art will recognize that the method shown in FIG. 6 can be widely applied to the measurement of other target molecules.

[0057] In step 602, a relatively high potential is applied to the interference zapping layer 302. At a high potential, the interference zapping layer 302 can oxidize both electrochemical interferents and target molecules, such as glucose. In embodiments where the target molecule is glucose, the high potential can be approximately +1.0 V relative to Ag / AgCl. The oxidation as a result of step 602 can deplete electrochemical interferents and target molecules in the region near electrodes 506a and 506b. In step 602, the potential is applied to electrodes Pt B and Pt F as well. In embodiments where glucose is the target molecule, the potential that can be applied to electrodes Pt B and Pt F can be +0.6 V.

[0058] In step 604, the current at the working electrodes Pt B and Pt F is measured. This step involves measuring the current at electrodes 506a (Pt E ) and 506b (Pt B ). Since interferents and target molecules may have been oxidized (and thereby eliminated) in step 602, at this point, the background current of each of electrodes 506a and 506b (B(Pt E ) and B(Pt B) represented by) can be measured. It may be desirable to perform the step of block 604 immediately after the step of block 602 so that there is not enough time for the electrochemical interferent and the molecule of interest to diffuse from the body fluid 504 outside the sensor to the electrodes 506a and 506b.

[0059] In step 606, the interference zapping layer 302 is set to a low potential. For example, if glucose is the molecule of interest, the interference zapping layer 302 can be set to +0.6 V with respect to Ag / AgCl. At such a potential, the electrochemical interferent can be oxidized, but the molecule of interest, such as glucose, cannot be oxidized. At such a potential, the molecule of interest, such as glucose, can diffuse to the electrodes 506a and 506b.

[0060] In step 608, the current at the electrodes Pt B and Pt E is measured. When the interference zapping layer 302 is set to a relatively low potential, the current I(Pt B ) at the electrode 506b without the enzyme layer is measured over time to estimate the current due to the interferents not blocked by the interference zapping layer 302. If the interference zapping layer 302 blocks a relatively high proportion and / or all of the electrochemical interferents, I(Pt B ) can be similar to the value of B(Pt B ). I(Pt E ), that is, the current at the electrode 506a with the enzyme layer 206 is also monitored over time. The I(Pt B ) signal can be mainly due to the concentration of the molecule of interest, such as glucose. The background shift can be estimated by subtracting B(Pt B ) from I(Pt B ).

[0061] In step 610, the current due to the molecule of interest is calculated. To estimate the signal due to the molecule of interest, such as glucose, the current measurements B(Pt B ), B(Pt E)、I(Pt B )、and I(Pt E ) can be used. The current signal I int by the target molecule is equal to the current at electrode 506a (I(Pt E )610) minus the background current of electrode 506a (B(Pt E )616), minus the current at electrode 506b (I(Pt B )612), plus the background current of electrode 506b (B(Pt B ). Equation 1 shows this mathematical relationship: I(Pt E ) - B(Pt E ) - I(Pt B ) + B(Pt B ) = I int (Equation 1)

[0062] In some embodiments, the measurements of the currents I(Pt E ) and I(Pt B ) at electrodes 506a and 506b may be continuous and / or relatively frequent, but the measurements of B(Pt E ) and B(Pt B ) may not be as frequent. For example, the measurements of B(Pt E ) and B(Pt B ) may be at least once a week, at least once a day, at least twice a day, at least once an hour, at least twice an hour, at least once every 10 minutes, at least once per minute, or any value or range within any of these ranges or values, or any value or range limited by any of these ranges or values, but in some cases values outside of these values or ranges can also be used.

[0063] The method shown in FIG. 6 can be performed with sensors other than the sensor schematized in FIG. 5A. For example, for a sensor such as the sensor shown in FIG. 5B, I(Pt E ) and B(Pt EThe measurement of ( ) can be performed by averaging the currents at the two electrodes 506a. The electrode 506b can be used to generate I(Pt B ) and B(Pt B ). As in the method schematized in FIG. 6, the estimation of the signal I int due to the molecule of interest can be performed according to Equation 1. Advantageously, the sensor of FIG. 5B can eliminate, minimize, and / or reduce errors due to glucose and other species concentration gradients along the length of the sensor.

[0064] The method shown in FIG. 6 can be implemented using the sensor shown in FIG. 5C. For example, according to step 602, two zapping electrodes 514a and 514b can be used respectively to remove the molecule of interest, such as glucose and electrochemically interfering substances. In some embodiments, a first interference zapping layer 514a can be used to oxidize the molecule of interest, such as glucose, and a second interference zapping layer 514b can be used to oxidize electrochemically interfering substances. In other embodiments, a first interference zapping layer 514a can be used to oxidize electrochemically interfering substances, and a second interference zapping layer 514b can be used to oxidize the molecule of interest, such as glucose. Advantageously, the sensor of FIG. 5C can oxidize glucose molecules through the interference zapping layers 514a and 514b at a lower potential than the interference zapping layer 302 in the exemplary sensor shown in FIG. 5A. This can reduce the electrochemical and / or oxidative damage to the polymer material in contact with the zapping layer, especially during a particularly long sensor session.

[0065] Characteristics of the sensor with an interference zapping layer Higher signal-to-noise ratio A blocking layer (e.g., a layer that blocks electrochemically interfering substances based on size or charge) may unintentionally block target molecules, such as hydrogen peroxide. Approximately 20 - 30% of the desired signal from hydrogen peroxide produced from the enzymatic conversion of glucose may be blocked by a size-based blocking layer beneath the enzyme layer. A charge-based blocking layer may also potentially result in a similar reduction in signal due to blocking of the target molecule.

[0066] Advantageously, sensors comprising an interference zapping layer according to the present disclosure can avoid a similar reduction in signal due to blocking of the target molecule. In the case of a sensor comprising an interference zapping layer, hydrogen peroxide generated in the enzyme layer as a byproduct of glucose conversion can be unimpeded, substantially unimpeded, and / or only minimally impeded from accessing the working electrode. Embodiments of such an interference zapping layer can result in an increase of at least 20 - 30% in the glucose-proportional current on the working electrode. For target molecules other than hydrogen peroxide, the increase in signal obtained by embodiments of the interference zapping layer can vary depending on the diffusion characteristics of the target molecule and the distance from the enzyme layer to the working electrode. Such an increase in signal can result in an improvement in the signal-to-noise ratio while the noise remains the same and / or at a similar level.

[0067] Miniaturization of the sensor By increasing the S / N ratio, it may be possible to miniaturize the sensor from a length of 300 μm to a smaller size. It may be desirable to reduce the size of the sensor. For example, a small sensor may be less likely to cause pain to the patient. Reducing pain during use can improve the patient experience and / or expand the population of people for whom the sensor can be used. As an illustrative example, since children may have lower pain tolerance compared to adults, miniaturizing the sensor may enable more children to tolerate the sensor.

[0068] Increase in sensor lifespan Molecules for specific purposes, such as hydrogen peroxide, can be highly reactive. Hydrogen peroxide belongs to a class of molecules called reactive oxygen species (ROS). ROS can react with many different biological molecules, including proteins. Enzymes, such as glucose oxidase enzyme, are proteins. Prolonged exposure to ROS can reduce the activity of the enzyme. For example, long-term exposure to hydrogen peroxide can reduce the ability of glucose oxidase to convert glucose. To extend the operating life of the sensor, it may be desirable to prevent and / or minimize the exposure of the enzyme to ROS.

[0069] In an embodiment of the glucose sensor by the sensor of FIG. 2, hydrogen peroxide generated through the enzymatic conversion of glucose diffuses outwardly and inwardly from the enzyme layer 208. Hydrogen peroxide molecules diffusing inwardly may encounter the working electrode 202, where they can be converted into benign molecules such as oxygen (O2) and water (H2O). However, hydrogen peroxide molecules that do not encounter the working electrode 202 may remain within the sensor, where they can oxidatively degrade the sensor components, including the enzyme within the enzyme layer. This oxidation reaction can contribute to the relatively short operating life of this type of glucose sensor, which can be approximately 10 days in some cases.

[0070] Advantageously, embodiments according to the present disclosure can address the problem of ROS degradation of sensor components. In some examples, such as the examples shown in FIGS. 3A - 3C, the interference zapping layer 302 surrounding the enzyme layer 208 can contact ROS, such as hydrogen peroxide, and then oxidize them, for example, convert hydrogen peroxide into oxygen and water. In this way, the amount of ROS, such as hydrogen peroxide, within the sensor can be reduced, thereby reducing the impact of ROS-mediated degradation of the sensor components.

[0071] In Vivo Sensor Calibration In vitro calibration of an electrochemical sensor, such as a glucose electrochemical sensor, may involve measuring the sensor signal at 0 mg / dL of the target molecule, such as glucose, before exposing the sensor to various other concentrations in order to obtain a calibration plot. In an exemplary CGM, this “true” baseline measurement at 0 mg / dL of glucose can be subtracted from each subsequent signal to more accurately estimate the true concentration of glucose in the test solution.

[0072] Control experiments such as “true” baseline measurements may not be possible in vivo. It is unlikely, essentially non - existent, or only rarely the case that a glucose concentration of 0 mg / dL exists in the biological fluid surrounding the sensor. Thus, in vivo, the sensor may be exposed to a particular level of glucose concentration, making it difficult to estimate the true baseline current value of the sensor.

[0073] Generally, baseline estimation can be performed from in vitro measurements using a sample of sensors from a batch of manufactured sensors. This baseline estimate can then be applied to correct the in vivo glucose estimates of other sensors in that batch. However, the true background current can vary between electrodes of the same batch. This difference can be due to several factors including variations in the roughness of the electrodes and / or the composition of the biological fluid compared to the test solution used during in vitro experiments. Thus, using the average background value from a set of sample electrodes from a particular batch can still lead to incorrect glucose estimates.

[0074] Certain aspects of the present disclosure may overcome these problems. For example, an interference zapping layer may be used to exclude glucose in the vicinity of the working electrode, thereby enabling measurement of the baseline while the sensor is positioned in vivo.

[0075] Sensor drift correction The number and types of interfering molecules can vary depending on the subject. Other factors that can affect the number and types of interfering molecules to which the sensor can be exposed include the depth at which the sensor is implanted, the hydration level, movement, vitamin C intake, acetaminophen intake, local inflammation, and the like. However, these changes can occur on a relatively short time scale of several hours before the probe insertion site equilibrates to a steady state.

[0076] As a result of the inflammatory response to sensor implantation, it may be possible to explain the degradation of the outer layer of the sensor and the occlusion of the sensor. In certain aspects of the present disclosure, determining the effect of degradation and / or occlusion of the outer layer of the sensor can be accomplished by measuring the steady-state interference level and quantifying the current passing through the interference zapping layer over a time scale of several hours to one day. In contrast, degradation and occlusion of the sensor can occur on a time scale of several days. The daily relative decrease or increase in the interference level compared to the first day of sensor implantation can be used to correct the amount of glucose available to the sensor. This measurement can be used by a hardware processor to correct sensor drift and potentially improve the accuracy of glucose measurements over the entire operating life of the sensor.

[0077] Other aspects of the sensors according to the present disclosure enable baseline measurements to be taken at any point during a sensor session that can last for several days. Under these conditions, the sensor baseline can shift in an unpredictable manner, possibly in response to degradation of the operating sensor elements over time and / or changes in the properties of the electrode surface, such as the slow conversion of the metal of the electrode to various oxides of that metal. By measuring the baseline value at various points during the sensor session, baseline drift can be monitored and the glucose estimate corrected accordingly.

[0078] Furthermore, the methods described herein may eliminate the need to develop factory calibrations based on extensive data collection and provide an efficient means for performing device corrections. Advantageously, the elimination of factory calibrations may save time in sensor manufacturing.

[0079] Increased oxygen availability in the enzyme layer As described above, the interference zapping layer may oxidize hydrogen peroxide to produce oxygen and water. The oxygen produced diffuses into the enzyme layer and may increase the availability of oxygen for glucose conversion. Thus, sensors constructed in accordance with the present disclosure may advantageously increase the oxygen in the enzyme layer excessively, such that the glucose conversion reaction shown in FIG. 1 may be glucose-limited rather than oxygen-limited.

[0080] Modulation by voltage In some embodiments, since the interference zapping layer may be physically separated from the electrode, the present disclosure enables independent control of unwanted interference oxidation using voltage. Such control may enable the development of unique measurement strategies and / or protocols for accurate glucose sensing, as described in the following examples.

[0081] Reduction of hysteresis Hysteresis is a phenomenon in which the time-evolving state retains a "memory" of the previous state and biases the measurement of the current state. In the context of electrode-based glucose measurements, hysteresis may be exaggerated when a person's glucose level drops rapidly (e.g., due to insulin bolus and / or exercise). Hydrogen peroxide generated a few minutes prior to a current measurement may remain in the sensor while the glucose is still at a high concentration, potentially artificially increasing the glucose measurement.

[0082] The sensors according to the present disclosure can reduce the influence of hysteresis. For example, by applying a potential to the interference zapping layer for a given amount of time while the working electrode is inactive (e.g., no potential is applied to the working electrode), all, substantially all, or much of the residual target molecules, such as hydrogen peroxide, can be oxidized from their previous state. After a specific length of zapping layer activation time, the working electrode can be activated to determine an unbiased reading, such as a reading of the current due to glucose.

[0083] Reduction of temperature drift Generally, enzyme activity can be sensitive to temperature. For example, the activity of glucose oxidase can increase by several times when transitioning from room temperature to human body temperature, such as when inserting a probe into the tissue of a subject. The increase in the activity of glucose oxidase can lead to a higher current at the glucose-sensing electrode simply due to the increase in the enzyme throughput.

[0084] Exemplary sensors according to the present disclosure can correct for the influence of temperature on the enzyme in the enzyme layer. For example, when the temperature of the sensor and the interference zapping layer current are measured, the throughput of the enzyme in the enzyme layer can be interpolated algorithmically, for example, by a hardware processor. Algorithmic interpolation can include, for example, comparing empirical measurements of the system at various temperatures and interference zapping layer currents.

[0085] Correction of interference based on the user's food, beverage, and / or drug intake As described above, various electrochemical interferents can have different oxidation potentials. When a user ingests a particular food, beverage, or drug, such as orange juice or acetaminophen, the interference zapping layer can be set to a particular potential for oxidizing the electrochemical interferents introduced to the user by that food, beverage, or drug. The interference zapping layer potential can be adjusted in consideration of the user's physiology and / or diet. The determination to adjust the interference zapping layer potential in response to food, beverage, and / or drug ingestion can be made, for example, by a lifestyle management app in combination with a glucose sensor. As an illustrative example, the sensor can be used in conjunction with Nudge, a lifestyle management app by Cercacor.

[0086] Sensor capable of rapid hydration Optionally, including a hydrophilic polymer in the sensor according to the present disclosure may be desirable to ensure rapid wetting and / or hydration of the sensor. For example, the hydrophilic layer of the sensor can include a hydrophilic polymer. Rapid wetting and / or hydration of the sensor can result in faster sensor stabilization and shorten the "warm-up" time after the sensor is inserted. Rapid wetting and / or hydration can also result in lower impedance. Rapid wetting and / or hydration can help the enzyme in the enzyme layer increase its activity. Rapid wetting and / or hydration can help the enzyme in the enzyme layer reach maximum and / or optimal activity.

[0087] Delamination and / or cracking of a particular hydrophilic polymer layer can occur during a long sensor session. For example, delamination and / or cracking of a particular hydrophilic polymer layer can occur during a sensor session that lasts for several hours and / or days. Without being bound by a particular theory, it is thought that delamination and / or cracking of the hydrophilic polymer layer can be caused by swelling of the hydrophilic polymer and a decrease in adhesion between the hydrophilic polymer layer and surrounding sensor layers, such as an interference zapping layer, a blocking layer, an enzyme layer, and / or an analyte restriction layer. Delamination and / or cracking can introduce non-uniformity into the interference blocking layer, thereby allowing electrochemical interferents to reach the electrodes. To improve these problems and shorten the wetting time, the sensor can include a wetting layer that contains a hydrophilic polymer.

[0088] Referring now to FIG. 12A, a sensor 1200 adapted for rapid hydration can include an analyte restriction layer 208, an adhesion promoter layer 1202, an enzyme layer 206, an interference zapping layer 302, a wetting layer 1204, and electrodes 202. The analyte restriction layer 208, the enzyme layer 206, the interference zapping layer 302, and the electrodes 202 can each be implemented in accordance with the present disclosure. In some embodiments, the analyte restriction layer 208 can include polyurethane. In some embodiments, the adhesion promoter layer 1202 can include a hydrophilic material, such as hydrophilic polyurethane. The electrodes 202 can include platinum.

[0089] In some embodiments, the wetting layer 1204 may include a doped polyurethane. In some embodiments, the polyurethane is doped with a copolymer of polyvinylpyrrolidone-co-polyvinyl acetate (PVP-co-PVAc). In some embodiments, the wetting layer 1204 includes polyvinylpyrrolidone (PVP). In some embodiments, the wetting layer 1204 may include a sulfonated tetrafluoroethylene-based fluoropolymer-copolymer (e.g., Nafion™). By including the wetting layer 1204, delamination and / or layer cracking can be suppressed, prevented, and / or minimized. The hydrophilic polyurethane material may be capable of absorbing up to 30 wt% water when exposed to an aqueous solution. The water absorption rate of the non-doped hydrophilic polyurethane material may be slow, which, when included in the sensor, can result in a higher impedance of the sensor and a lower permeability of target molecules (e.g., hydrogen peroxide) to the electrode 202 immediately after insertion of the sensor into the patient's body (e.g., within minutes to hours of insertion). By including a dopant, such as the PVP-co-PVAc copolymer, in the wetting layer 1204, the rate at which the wetting layer 1204 can absorb water can be increased. Advantageously, both the hydrophilic polyurethane and the PVP-co-PVAc copolymer are soluble in organic solvents, and thus, the manufacture of the wetting layer 1204 according to this embodiment can include fewer steps. Other suitable materials that provide sufficient adhesion and water absorption may also be suitable for inclusion in the wetting layer 1204.

[0090] In some embodiments, the enzyme layer 206 may include an aqueous polyurethane, polyethylene glycol diglycidyl ether, and / or polyethylene diamine. In some embodiments, the enzyme layer 206 may include glucose oxidase. The enzyme layer 206 may be formed using an aqueous polyurethane material and a cross-linked polyethylene diamine. Without being bound by a particular theory, it is believed that the presence of amines (e.g., polyethylene diamine) within the enzyme layer 206 provides a positive charge and enables the enzyme layer 206 to rapidly hydrate. In embodiments where the enzyme layer 206 includes a polyurethane matrix, the polyurethane matrix may provide adhesion between the enzyme layer 206 and other polyurethane-based layers, such as the analyte restriction layer 208. Other suitable materials that provide sufficient adhesion and water absorbency may also be suitable for inclusion in the enzyme layer 206.

[0091] Referring now to FIG. 12B, a sensor including a wetting layer may include an analyte restriction layer 208, an adhesion promoter layer 1202, an enzyme layer 206, an interference zapping layer 302, a wetting layer 1204, an electrode 202, and an insulator 1206. The analyte restriction layer 208, the adhesion promoter layer 1202, the enzyme layer 206, the interference zapping layer 302, the wetting layer 1204, and the electrode 202 may all be implemented in accordance with the present disclosure. As shown in FIG. 12B, the insulator 1206 may encompass the adhesion promoter layer 1202, the enzyme layer 206, the interference zapping layer 302, the wetting layer 1204, and the electrode 202. In such embodiments, when the sensor is in contact with a patient's body fluid (e.g., interstitial fluid), the insulating material may ensure that the body fluid can contact the electrode 202 only through the layers 208, 1202, 206, 302, and 1204.

[0092] In some embodiments, the height h between the surface of the analyte restriction layer 208 and the surface of the electrode 202 may be about 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25, 26, 27, 28, 29, or 30 μm, or within a range defined by any of the foregoing values. In some embodiments, the height h is about 10 to about 15 μm.

[0093] In some embodiments, the analyte confinement layer 208 can be about 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, or 15 μm thick, or within a range defined by any of the foregoing values. In some embodiments, the thickness of the analyte confinement layer 208 can be from about 2 to about 10 μm.

[0094] In some embodiments, the adhesion promoting layer 1202 can be about 0.1, 0.2, 0.3, 0.4, 0.5, 0.6, 0.7, 0.8, 0.9, 1.0, 1.1, 1.2, 1.3, 1.4, or 1.5 μm thick, or within a range defined by any of the foregoing values. In some embodiments, the thickness of the adhesion promoting layer 1202 can be from about 0.1 to about 1 μm.

[0095] In some embodiments, the enzyme layer 206 can be about 0.5, 1.0, 1.5, 2.0, 2.5, 3.0, 3.5, 4.0, 4.5, 5.0, 5.5, 6.0, 6.5, 7.0, 7.5, 8.0, 8.5, 9.0, 9.5, or 10.0 μm thick, or within a range defined by any of the foregoing values. In some embodiments, the thickness of the enzyme layer 206 can be from about 1 to about 5 μm.

[0096] In some embodiments, the interference blocking layer 302 can be about 0.5, 1.0, 1.5, 2.0, 2.5, 3.0, 3.5, 4.0, 4.5, 5.0, 5.5, 6.0, 6.5, 7.0, or 7.5 μm thick, or within a range defined by any of the foregoing values. In some embodiments, the thickness of the interference blocking layer 302 can be from about 2 to about 5 μm.

[0097] In some embodiments, the wetting layer 1204 can be about 0.1, 0.2, 0.3, 0.4, 0.5, 0.6, 0.7, 0.8, 0.9, 1.0, 1.1, 1.2, 1.3, 1.4, or 1.5 μm thick, or within a range defined by any of the foregoing values. In some embodiments, the thickness of the wetting layer 1204 can be from about 0.1 to about 1 μm.

[0098] Measurement mode In some embodiments, the sensor according to the present disclosure can execute a measurement mode, and during the measurement, the sensor can proceed with a plurality of combinations of the working electrode potential and the zapping layer potential. Thereby, at each of the plurality of zapping layer potentials, the working electrode potential can be sampled at a plurality of potentials. Such a sensor can thereby generate a rich dataset, which can enable a hardware processor to determine the concentration of one or more physiological analytes, such as glucose. For example, the sensor can perform measurements for each combination of the working electrode potential and the zapping layer potential. Such an approach can obviate the need for calibration steps in the factory because all of the background current, the signal due to electrochemically interfering substances, and the signal due to the analyte of interest can be captured when the sensor proceeds with a combination of the zapping layer potential and the working electrode potential. Such an approach can enable the measurement of more molecular species, such as the concentration estimate of one or more analytes of interest and / or the concentration estimate of electrochemically interfering substances. Such an approach can enable a device having the sensor of the present disclosure to warn the user of measurement inaccuracies due to electrochemically interfering substances. A sensor that executes a measurement mode can potentially estimate the concentration of a specific electrochemically interfering substance. Such an approach can enable measurements focused on a specific combination of the working electrode and the interfering zapping layer potential. For example, in an initial measurement, it may be possible to identify the signal at a specific working electrode potential and a specific interfering electrode potential in particular. Subsequent measurements can measure the working electrode current at a specific working electrode potential and a specific interfering zapping layer potential without measuring the current at all combinations of the working electrode potential and the interfering zapping layer potential.

[0099] Referring to FIG. 7, the sensor according to the present disclosure can set the potential V of its working electrode WE to a plurality of different voltages including, for example, V WE1 , V WE2 , V WE3 , V WE4 among a plurality of potentials V including WEn . Successive working electrode potential values (e.g., V WE1 and VWE2 ) can be separated by only the difference of ΔV WE . In some embodiments, the difference ΔV WE may be equal across the voltage range of V WE1 to V WEn . In other embodiments, the difference ΔV WE may be non-uniform and / or variable across the voltage range of V WE1 to V WEm . The sensor according to the present disclosure can also set the potential V ZE of its interference zapping layer to a plurality of different voltages, for example, including V ZE1 , V ZE2 , V ZE3 , V ZE4 . The successive zapping layer potential values (e.g., V ZEm and V ZE1 ) can be separated by only the difference of ΔV ZE2 . In some embodiments, the difference ΔV ZE may be equal across the voltage range of V ZE to V ZE1 . In other embodiments, the difference ΔV ZEm may be non-uniform and / or variable across the voltage range of V ZE to V ZE1 . The sensor can generate discrete measurements of current I ZEm while the working electrode potential is set to voltage V WEx and the interference zapping layer is set to voltage V ZEy . For example, when the working electrode potential is set to V x,y and the zapping layer potential is set to V WE1 , discrete measurement I ZE1 can be generated. As a further example, when the working electrode potential is set to V 1,1 and the zapping layer potential is set to V WE2 , discrete measurement I ZE1 can be generated. As a further example, when the working electrode potential is set to V 2,1 and the zapping layer potential is set to V WE1 , discrete measurement I ZE2 can be generated. As a further example, when the working electrode potential is set to V 1,2 and the zapping layer potential is set to V WEnis set and the zapping layer potential is V ZEm is set, discrete measurement values I n,m can be generated. The measurement values can be stored and / or represented as a matrix, for example matrix I 1-n,1-m as shown in FIG. 7.

[0100] When the voltage V ZE of the interference zapping layer changes, a particular physiological analyte can be oxidized before encountering the working electrode, for example by diffusion. Thus, as the potential V ZE of the zapping layer changes, the current measured by the working electrode due to the detectable analyte can change accordingly.

[0101] As the voltage of the working electrode V WE changes, the measured current can depend on the voltage profile of the analyte being oxidized by the working electrode at the potential V WE .

[0102] The working electrode potential V WE can be set to various different voltages as part of the measurement mode according to the present disclosure. In some embodiments, the potential V WEis set to a voltage in the range from about 0 V Ag / AgCl, +0.01 V Ag / AgCl, +0.05 V Ag / AgCl, +0.1 V Ag / AgCl, +0.2 V Ag / AgCl, +0.3 V Ag / AgCl, +0.4 V Ag / AgCl, +0.5 V Ag / AgCl, +0.6 V Ag / AgCl, +0.7 V Ag / AgCl, +0.8 V Ag / AgCl, +0.9 V Ag / AgCl, +1.0 V Ag / AgCl, +1.1 V Ag / AgCl, +1.2 V Ag / AgCl, +1.3 V Ag / AgCl, +1.4 V Ag / AgCl, +1.5 V Ag / AgCl, +1.6 V Ag / AgCl, +1.7 V Ag / AgCl, +1.8 V Ag / AgCl, +1.9 V Ag / AgCl, or +2.0 V Ag / AgCl, or one or more voltages within a range defined by any two of the foregoing values. In some embodiments, the range of the working electrode potential can be about 0 V to +1.5 V Ag / AgCl, 0 V to +1.25 V Ag / AgCl, 0 V to +1.1 V Ag / AgCl, 0 V to +1.0 V Ag / AgCl, or 0 V to +0.7 V Ag / AgCl. In some embodiments, the working electrode potential V WE is ΔV WE is 0.001 V, ΔV WE is 0.01 V, ΔV WE is 0.05 V, ΔV WE is 0.1 V, ΔV WE is 0.1 V, ΔV WE is 0.2 V, ΔV WE is 0.25 V, ΔV WE is 0.3 V, ΔV WE is 0.4 V, ΔV WE is 0.5 V, ΔV WE is 0.75 V, or ΔV WE is set to a series of voltages of 1 V.

[0103] The zapping layer potential V ZE can be set to various different voltages as part of the measurement mode according to the present disclosure. In some embodiments, the potential V ZEis set to a voltage in the range from about 0 V Ag / AgCl, +0.01 V Ag / AgCl, +0.05 V Ag / AgCl, +0.1 V Ag / AgCl, +0.2 V Ag / AgCl, +0.3 V Ag / AgCl, +0.4 V Ag / AgCl, +0.5 V Ag / AgCl, +0.6 V Ag / AgCl, +0.7 V Ag / AgCl, +0.8 V Ag / AgCl, +0.9 V Ag / AgCl, +1.0 V Ag / AgCl, +1.1 V Ag / AgCl, +1.2 V Ag / AgCl, +1.3 V Ag / AgCl, +1.4 V Ag / AgCl, +1.5 V Ag / AgCl, +1.6 V Ag / AgCl, +1.7 V Ag / AgCl, +1.8 V Ag / AgCl, +1.9 V Ag / AgCl, or +2.0 V Ag / AgCl, or one or more voltages within a range defined by any two of the foregoing values. In some embodiments, the range of the interference zapping layer potential can be about 0 V to +1.5 V Ag / AgCl, 0 V to +1.25 V Ag / AgCl, 0 V to +1.1 V Ag / AgCl, 0 V to +1.0 V Ag / AgCl, or 0 V to +0.7 V Ag / AgCl. In some embodiments, the interference zapping layer potential V ZE is ΔV ZE of 0.001 V, ΔV ZE of 0.01 V, ΔV ZE of 0.05 V, ΔV ZE of 0.1 V, ΔV ZE of 0.1 V, ΔV ZE of 0.2 V, ΔV ZE of 0.25 V, ΔV ZE of 0.3 V, ΔV ZE of 0.4 V, ΔV ZE of 0.5 V, ΔV ZE of 0.75 V, or ΔV ZE of 1 V and can be set to a series of voltages.

[0104] Matrix I 1-n,1-mThe working electrode potential and the zapping layer potential can be set simultaneously in such an order that all or a subset of the current is measured. The working electrode potential and the zapping layer potential can be set in any suitable order. In some embodiments, the interfering zapping layer can be held at a particular potential, while the potential applied to the working electrode can progress between a series of potentials. For example, referring to FIG. 8A, when the working electrode potential progresses between V WE1 and V WE2 by changing stepwise, such as from V WE2 to V WE3 and so on, the interfering zapping layer can be held at the potential V WEn . Thereafter, as shown, the interfering zapping layer is set to the potential V ZE1 , and the working electrode potential progresses again, such as between V ZE2 and V WE1 to V WEn and so on. The working electrode potential is shown as increasing in FIG. 8A, but the working electrode potential can alternatively progress, for example, by decreasing, such as from V WE4 to V WE3 , from V WE3 to V WE2 and so on. The zapping interference is shown as increasing in FIG. 8A, but it should be understood that the zapping interference layer can alternatively progress, for example, by decreasing, such as from V ZE4 to V ZE3 , from V ZE3 to V ZE2 and so on.

[0105] In some embodiments, the working electrode can be held at a particular potential, while the potential applied to the interfering zapping layer can progress between a first plurality of potentials. For example, referring to FIG. 8B, when the interfering zapping layer progresses between V ZE1 and V ZE2 by changing stepwise, such as from V ZE2 to V ZE3 and so on, the working electrode can be held at the potential V ZE3 . Thereafter, the working electrode is V WE1 and then the working electrode is V WE2is set, and then, as shown, the zapping layer potential proceeds again between V ZE1 and V ZE3 for example. Although the working electrode potential is shown as increasing in FIG. 8B, the working electrode potential may alternatively proceed, for example, by decreasing from V WE4 to V WE3 , from V WE3 to V WE2 and so on. Although the zapping interference is shown as increasing in FIG. 8B, the zapping interference layer may alternatively proceed, for example, by decreasing from V ZE4 to V ZE3 , from V ZE3 to V ZE2 and so on. In some embodiments, each of the potential of the working electrode and the potential of the zapping layer may vary for successive measurements made by the working electrode. For example, referring to FIG. 8C, to measure I 1,1 , the working electrode potential may be set to V WE1 and the interfering zapping layer may be set to V ZE1 . Then, to measure I 2,2 , the working electrode potential may be set to V WE2 and the interfering zapping layer may be set to V ZE2 . Then, to measure I 3,3 , the working electrode potential may be set to V WE3 and the interfering zapping layer may be set to V ZE3 and so on. For example, referring to FIG. 8D, the working electrode potential may be set to V WE1 and the interfering zapping layer may be set to V ZE1 . Then, to measure I 1,2 , the working electrode potential may be set to V WE1 and the interfering zapping layer may be set to V ZE2 . Then, to measure I 2,1 , the working electrode potential may be set to V WE2 and the interfering zapping layer may be set to V ZE1 and so on.

[0106] In some aspects, a hardware processor that communicates with a sensor as disclosed herein can create a data structure composed of measurement values. Instead of a single working electrode measurement at a single interference zapping layer potential, creating a data structure such that an analyte concentration can be determined using a rich dataset can advantageously incorporate some and / or all of the measured current. In some aspects, matrix I 1-n,1-m and / or matrix I 1-n,1-m The measurement values that make up the sub-blocks of can define a heatmap, as shown in FIG. 9. The current I 1-n,1-m can be organized by the respective working electrode potential V WE and the interference zapping layer potential V ZE , and the magnitude of the current can be represented by color. The hardware processor may be capable of outputting the heatmap to a display. The hardware processor may be capable of comparing a heatmap measured from a patient with one or more previous heatmaps. For example, the hardware processor may compare a heatmap measured from a patient with a heatmap measured from a subject whose ISF concentration of one or more molecular species is known. For example, the hardware processor may compare a heatmap measured from a patient with a heatmap measured from a control fluid whose concentration of one or more molecular species is known. For example, the hardware processor may compare a heatmap measured from a patient with a previous heatmap measured from that patient. Thereby, the processor may be able to estimate the concentration of one or more molecular species. The current matrix I 1-n,1-m can be displayed as a three-dimensional plot. For example, the height in the z-dimension can correspond to the measured current, the position along the x-axis can correspond to the working electrode potential V WE , and the position along the y-axis can correspond to the interference zapping layer potential V ZEmay be applicable. However, any combination of axes and variables and / or outputs may be used. For example, a hardware processor may compare a three-dimensional plot measured from a patient to a three-dimensional plot measured from a subject whose ISF concentration of one or more molecular species is known. For example, a hardware processor may compare a three-dimensional plot measured from a patient to a three-dimensional plot measured from a control fluid whose concentration of one or more molecular species is known. For example, a hardware processor may compare a three-dimensional plot measured from a patient to a previous three-dimensional plot measured from that patient. Thereby, the processor may be able to estimate the concentration of one or more molecular species. Current array I 1-n,1-m may be displayed as an array. For example, the values within the array may correspond to measured currents, and the positions within the array may be the working electrode potential V WE and / or the interference zapping layer potential V ZE to which they may correspond. For example, a hardware processor may compare an array measured from a patient to an array measured from a subject whose ISF concentration of one or more molecular species is known. For example, a hardware processor may compare an array measured from a patient to an array measured from a control fluid whose concentration of one or more molecular species is known. For example, a hardware processor may compare an array measured from a patient to a previous array measured from that patient. Thereby, the processor may be able to estimate the concentration of one or more molecular species. The processor may use any suitable data structure and / or representation of the measurements to compare to control measurements (e.g., measurements from other subjects or measurements from fluids with known amounts of analyte) and / or previous patient measurements.

[0107] In some embodiments, during the measurement mode, only a subset of the measurement matrix I shown in FIG. 7 1-n,1-m may be generated. FIG. 10 schematizes an exemplary process in which a subset of the measurement matrix I 1-n,1-m is measured. In step 1002, the sensor executes a measurement mode to measure a first plurality of currents. The first plurality of currents are, for example, the current array I 1-n,1-mIt can be the whole. In step 1004, the processor can determine a range of target potentials, for example, a set and / or range of working electrode potentials V WE and / or a set and / or range of zapping interference layer potentials V ZE . The target potential can correspond to a second plurality of currents. The processor can determine the target potential at least partially based on the first plurality of currents. For example, referring to FIG. 9 here, the processor can identify a subset 902 of the currents within a matrix I 1-n,1-m that can indicate the concentration of an analyte and / or molecular species. As an illustrative example, the subset 902 can have relatively high currents due to the oxidation of a molecular species. The subset 902 is shown as corresponding to a set of adjacent interference zapping layer potentials (i.e., V ZE2 to V ZE4 ) and a set of adjacent working electrode potentials (i.e., V WE2 to V WE4 ), but the target potential identified in step 1004 need not be adjacent. In some aspects, the hardware processor can determine the target potential by omitting potentials that are irrelevant to and / or minimally related to the molecular species being monitored. In step 1006, the sensor can enter a measurement mode to generate a second plurality of currents. The second plurality of currents can correspond to the target potential determined by the processor. The second plurality of currents can include fewer measurement currents than the first plurality of currents. Measuring a subset of the current matrix I 1-n,1-m can be desirable, for example, to shorten the time to measurement by an electrochemical probe according to the present disclosure. Since step 1006 involves selectively measuring currents at specific potentials only, step 1006 can take less time to complete than step 1002. Similarly, the completion of step 1006 can require less energy input than the completion of step 1002 because step 1006 involves fewer measurements.

[0108] Steps 1002, 1004, and 1006 can optionally be repeated periodically. Step 1006 can be performed periodically, for example, to identify changes in the concentration of one or more target molecular species. Although measurements are desired, if the entire current array I 1-n,1-m is not necessary, it may be desirable to repeat step 1006. Step 1006 can be repeated, for example, when detailed measurements are not required, minimization of sensor power output is desired, and / or minimization of the time until measurement completion is desired. If power output and / or the time until measurement completion are not issues, it may be desirable to repeat step 1002. It may be desirable to repeat step 1002 to re-measure the current corresponding to a potential that exceeds the potential identified as the target potential. It may be desirable to repeat step 1004 in response to new measurements made in either step 1002 and / or 1006. In some embodiments, step 1002 can be repeated less frequently than step 1006. In some embodiments, step 1002 can be repeated at the same frequency as step 1006. In some embodiments, step 1002 can be repeated more frequently than step 1006. In some embodiments, the frequency of repeating step 1002 and / or 1006 can depend at least in part on the measured current. In some embodiments, step 1004 is not repeated more frequently than either step 1002 and / or step 1006. In some embodiments, step 1002 can be repeated at least once per week, day, hour, 30 minutes, 10 minutes, 1 minute, 30 seconds, 10 seconds, 1 second, or within a range defined by any two of the progression values. In some embodiments, step 1004 can be repeated at least once per week, day, hour, 30 minutes, 10 minutes, 1 minute, 30 seconds, 10 seconds, 1 second, or within a range defined by any two of the progression values. In some embodiments, step 1006 can be repeated at least once per week, day, hour, 30 minutes, 10 minutes, 1 minute, 30 seconds, 10 seconds, 1 second, or within a range defined by any two of the progression values.

[0109] Advantageously, a sensor capable of performing the measurement mode according to the present disclosure may be able to deconvolve the current signal to identify the contributions by individual molecular species or groups of molecular species. FIG. 11A is a cyclic voltammogram plotting the detected current as a function of the working electrode potential V WE for various concentrations of glucose in vitro. The current I glu can be a function f(V WE , c glu ) of the working electrode potential V WE and the glucose concentration c glu . FIG. 11B is a cyclic voltammogram plotting the detected current as a function of the working electrode potential V WE for various concentrations of acetaminophen. Glucose and acetaminophen are examples of molecular species that may be detectable by the measurement mode, and FIGS. 11A-11B are provided as exemplary examples of voltammetric profiles of such molecular species. The current I ace can be a function f(V WE , c ace ) of the working electrode potential V WE and the acetaminophen concentration c ace . In the case of the electrochemical measurement of a patient's ISF, the resulting voltammogram can be a convolution of a plurality of current signals over the potential range measured by the working electrode, as described herein. The measured current I tot of an ISF having n molecular species capable of generating a current when oxidized can be described by Equation 2:

Equation

[0110] As a simple example, in the case of an ISF measurement where there are only two molecular species X and Y that generate a current due to oxidation at the working electrode, the measured current I tot is (I X + I Ymay be equal to. For example, in the case of ISF measurement where only two molecular species that generate current due to oxidation at the working electrode include glucose and acetaminophen, the measured current I tot may be equal to (I glu + I ace ).

[0111] The measurement modes described herein enable the deconvolution of I i for estimating one or more currents I tot caused by individual molecular species. When the potential V ZE 1-m of the interference zapping layer changes stepwise between, certain molecular species may be oxidized before reaching the working electrode, and they do not contribute current to the measurement performed by the working electrode. Molecular species X may have a higher oxidation potential than molecular species Y. When V ZE is set to 0V and I tot = (I X + I Y ) in a simple example, if it is assumed that I ZE is almost 0 when V is set such that it oxidizes molecular species Y but not molecular species X, I Y can be approximately equal to only I tot : I X = (I tot + 0) = I X = I X . Generally, I tot may depend on fewer molecular species as V ZE increases.

[0112] A hardware processor in electronic communication with the sensor according to the present disclosure can compare I ZE at two or more zapping layer potentials V tot to determine the current contributions of one or more molecular species sensed by the working electrode. For example, referring again to the simple example where I ZE = (I tot + I X + I Y ) when V ZE Amay be insufficiently high to oxidize molecular species Y, but the second zapping layer potential V ZE B is high enough to oxidize molecular species Y, but may be insufficiently high to oxidize molecular species X. V ZE A In, the working electrode is (I X + I Y ) can be equal to I tot A can be sensed. V ZE B In, molecular species Y can be prevented or suppressed from reaching the working electrode due to the potential V ZE B of the interference zapping layer, so the working electrode can sense I X that may be equal to I tot B can be sensed. The hardware processor according to the present disclosure can subtract I tot A from I tot B to calculate I Y . I tot A - I tot B = (I X + I Y ) - (I X ) = I Y (Equation 3) The hardware processor can estimate the concentration of X based at least in part on the magnitude of the current I X . The hardware processor can estimate the concentration of Y based at least in part on the magnitude of the current I Y .

[0113] In the case of an ISF having three or more molecular species, it may be desirable to measure the current I tot at a plurality of interference zapping layer potentials V ZE such that there is a sufficient current I tot for comparison. For example, in the case of an ISF having three species X, Y, and Z, where X has a higher oxidation potential than either Y or Z, and Y has a higher oxidation potential than Z, the current I ZE corresponding to a zapping layer potential V tot C that is insufficient to oxidize any of X, Y, and Z, the zapping layer potential V ZEI corresponding thereto tot D , and a zapping layer potential V that is sufficient to oxidize Z and Y but insufficient to oxidize X ZE I corresponding thereto tot E may desirably be measured. Thus, I tot E -I tot D =(I X +I Y +I Z )-(I X +I Y )=I Z (Equation 4) I tot D -I tot C =(I X +I Y +0)-(I X +0)=I Y (Equation 5) I tot C =I X (Equation 6) The hardware processor can estimate the concentration of X based at least in part on the magnitude of the current I X . The hardware processor can estimate the concentration of Y based at least in part on the magnitude of the current I Y . The hardware processor can estimate the concentration of Z based at least in part on the magnitude of the current I Z .

[0114] The above-described approach can be generalized to an ISF having more than three molecular species, for example, by making more measurements at an additional zapping layer potential V ZE . Additionally or alternatively, this approach can be adapted to determine the current I tot of a group of molecular species having similar oxidation potentials. For example, when stepping from a first zapping layer potential to a second zapping layer potential, I due to molecular species having a lower oxidation potential between the first zapping layer potential and the second zapping layer potential totThe current contribution to it can be eliminated or reduced. For example, if the individual concentrations of those molecular species are not the desired ones, it may not be desirable to set the zapping layer potential to a value between the first zapping layer potential and the second zapping layer potential.

[0115] In some embodiments, the measured current I tot can be continuous (e.g., measured over a continuous working electrode potential V WE ). In some embodiments, the measured current I tot can include discrete measurement values. For example, referring again to FIG. 7, I tot can include a set of currents measured at a single interfering zapping layer potential V ZE . For example, the I ZE 1 measured at V tot 1 can include (I 1,1 , I 2,1 , I 3,1 , I 4,1 , … I n,1 ), and the I ZE 2 measured at V tot 2 can include (I 1,2 , I 2,2 , I 3,2 , I 4,2 , … I n,2 ), and the I ZE 3 measured at V tot 3 can include (I 1,3 , I 2,3 , I 3,3 , I 4,3 , … I n,3 ), and the I ZE 4 measured at V tot 4 can include (I 1,4 , I 2,4 , I 3,4 , I 4,4 , … I n,4 ), and the I ZE m measured at V tot m can include (I 1,m , I 2,m , I 3,m , I 4,m , … I n,m ). The hardware processor, in embodiments where I tot includes discrete measurement values, curves Itot may be capable of being adapted to.

[0116] Term As used herein, "molecular species" refers to one or more types of molecules that can be sensed by the working electrode. A "molecular species" can be an analyte or an electrochemical interferent.

[0117] "Interference zapping layer", "zapping layer", "interference layer", "interfering zapping layer", and "interfering layer" are all used interchangeably herein.

[0118] A "working electrode" is the electrode of an electrochemical sensor at which the reaction of interest can occur. The terms "working electrode" and "sensing electrode" are used interchangeably herein.

[0119] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art. The terms "including" and its other forms such as "include", "includes", and "included" are not limiting. The terms "having" and its other forms such as "have", "has", and "had" are not limiting. The terms "comprising", "including", "having", etc. are synonyms and are used in an inclusive, open-ended manner and do not exclude additional elements, features, acts, operations, etc. That is, the above terms should be construed as synonymous with the phrase "having at least" or "including at least". For example, when used in the context of a process, the term "comprising" means that the process includes at least the recited steps but may also include additional steps. When used in the context of an apparatus, the term "comprising" means that the apparatus includes at least the recited features or components but may also include additional features or components. Also, the term "or" is used in an inclusive sense (not an exclusive sense), and for example, when used to connect a list of elements, the term "or" means one, some, or all of the elements in the list. Further, the term "each" as used herein, in addition to having its ordinary meaning, can mean any subset of the set of elements to which the term "each" applies.

[0120] Conditional language such as "can", "could", "might", or "may" generally, unless otherwise specified or understood in another sense within the context in which it is used, is intended to convey that a particular embodiment includes a particular feature, element, or step, while other embodiments do not. Thus, such conditional language is generally not intended to mean that a feature, element, or step is required in any way in one or more embodiments, or that one or more embodiments necessarily include logic for determining whether these features, elements, or steps are to be included in or performed by any particular embodiment, regardless of the presence or absence of user input or prompts.

[0121] Conjunctive language such as the phrase "at least one of X, Y, and Z" is generally understood in the context in which it is used to convey that an item, term, etc. can be either X, Y, or Z. Thus, such conjunctive language is generally not intended to mean that a particular embodiment requires the presence of at least one of X, at least one of Y, and at least one of Z.

[0122] As used herein, language such as "approximately", "about", "generally", and "substantially" refers to a value, amount, or property that is still close to the recited value, amount, or property that performs the desired function or achieves the desired result. For example, the terms "approximately", "about", "generally", and "substantially" can refer to an amount less than 10%, less than 5%, less than 1%, less than 0.1%, and less than 0.01% of the recited amount. As another example, in certain embodiments, the terms "generally parallel" and "substantially parallel" refer to a value, amount, or property that deviates from exact parallelism by 15 degrees, 10 degrees, 5 degrees, 3 degrees, 1 degree, 0.1 degree or less, or otherwise.

[0123] As used herein, the term "and / or" has its broadest, least restrictive meaning in that the disclosure includes A alone, B alone, both A and B, or A or B alternatively, without requiring both A and B, and without requiring one of A or one of B. When used herein, the phrase "at least one" of A, B, and "and" C should be construed to mean the logical or of A or B or C using non-exclusive disjunction.

[0124] Conditional language used herein, such as "can", "could", "might", or "may", "e.g.", etc., is generally intended to convey that a particular thing, particular feature, element and / or step is optional, unless otherwise specified or understood within the context in which it is used. Thus, such conditional language is not generally intended to mean that a feature, element, and / or step is required in any way, or that one or more embodiments necessarily include logic for determining whether these features, elements, and / or steps are included or should always be performed, regardless of the presence or absence of other inputs or prompts.

[0125] The methods disclosed herein need not be performed in the order recited. The methods disclosed herein include particular operations performed by a practitioner. However, they can also include, explicitly or implicitly, any third-party instructions of those operations.

[0126] The methods and tasks described herein are performed by a computer system and can be fully automated. The computer system may in some cases include a plurality of distinct computers or computing devices (e.g., physical servers, workstations, storage arrays, cloud computing resources, etc.) that communicate and interoperate via a network to perform the described functions. Each such computing device typically includes a processor (or processors) that executes program instructions or modules stored in a memory or other non-transitory computer-readable storage medium or device (e.g., solid state storage device, disk drive, etc.). The various functions disclosed herein may be embodied in such program instructions and / or implemented in application-specific circuitry of the computer system (e.g., ASIC or FPGA). If the computer system includes a plurality of computing devices, these devices may be located in the same place, but they do not have to be. The results of the disclosed methods and tasks can be permanently stored by changing physical storage devices such as solid state memory chips and / or magnetic disks to different states. The computer system can be a cloud-based computing system in which its processing resources are shared by a plurality of different business entities or other users.

[0127] The foregoing detailed description has shown, described, and pointed out novel features, but it can be understood that various omissions, substitutions, and changes in the form and detail of the illustrated devices or algorithms can be made without departing from the spirit of the present disclosure. As can be understood, certain portions of the description herein can be embodied in a form that does not provide all of the features and advantages described herein because some features can be used or practiced separately from other features. The scope of the specific embodiments disclosed herein is indicated by the appended claims rather than the foregoing description. All changes within the meaning and scope of the equivalents of the claims should be embraced within their scope.

Description of the Reference Signs

[0128] 202 Working electrode 204 Blocking layer 206 Enzyme layer 208 Analyte restriction layer 300 Electrochemical sensor 302 Interference zapping layer, electrode 402 Applied electrode potential 404 Applied interference zapping layer potential 502 Insulating substrate 504 Body fluid 506a Electrode 506b Electrode 506c Electrode 506d Electrode 510 Catalase layer 512 Enzyme layer 514a First interference zapping layer, electrode 514b Second interference zapping layer, electrode 516a First polymer layer 516b Second polymer layer 902 Subset 1200 Sensor 1202 Adhesion promoter layer 1204 Wetting layer 1206 Insulator

Claims

1. An electrode, an enzyme layer, and an interference zapping layer comprising an electrochemical probe.

2. The probe according to claim 1, further comprising an analyte restriction layer.

3. The probe according to claim 2, wherein the analyte restriction layer is a glucose restriction layer.

4. The probe according to any one of claims 1 to 3, wherein the electrode is configured to measure glucose concentration.

5. The probe according to any one of claims 1 to 4, wherein the enzyme layer is configured to convert glucose into hydrogen peroxide and gluconic acid.

6. The probe according to claim 5, wherein the enzyme layer contains glucose oxidase.

7. The probe according to any one of claims 1 to 6, further comprising a blocking layer.

8. The probe according to claim 7, wherein the blocking layer comprises a size-based filter or an electrostatic repulsion filter.

9. The probe according to any one of claims 1 to 8, comprising a voltage source configured to set the electrode to an applied potential of +0.1 to +1 V.

10. The probe according to claim 9, wherein the voltage source is configured to set the electrode to an applied potential of +0.6 to +0.7 V.

11. The probe according to claim 9, wherein the voltage source is configured to set the interference zapping layer to an applied voltage of +0.3 to +1 V.

12. The probe according to claim 9, wherein the voltage source is configured to set the interference zapping layer to an applied voltage of +0.7 to +0.8 V.

13. A first voltage source configured to set the electrode to a first applied potential, and a second voltage source configured to set the interference zapping layer to a second applied potential comprising, wherein the second applied potential is equal to or greater than the first applied potential, The probe according to any one of claims 1 to 12.

14. The probe according to any one of claims 1 to 13, wherein the interference zapping layer contains a hydrogel.

15. The probe according to any one of claims 1 to 14, wherein the interference zapping layer contains a micro wire.

16. The probe according to claim 15, wherein the interference zapping layer contains a micro wire network.

17. The probe according to any one of claims 1 to 16, wherein the interference zapping layer contains a nano wire.

18. The probe according to claim 17, wherein the interference zapping layer comprises a nanowire network.

19. The probe according to any one of claims 1 to 18, wherein the interference layer comprises cellulose acetate crosslinked with citric acid.

20. The probe according to any one of claims 1 to 19, further comprising an adhesive layer.

21. The probe according to any one of claims 1 to 20, further comprising a wetting layer.

22. A continuous glucose monitor comprising the electrochemical probe according to any one of claims 1 to 21.

23. A first electrode in contact with a first enzyme layer a second electrode, and a first interference zapping layer outside the first electrode and the second electrode A probe comprising:

24. The probe according to claim 23, further comprising an insulating substrate disposed under the first electrode and the second electrode.

25. The probe according to claim 23 or 24, further comprising a third electrode in contact with a second enzyme layer.

26. A second enzyme layer in contact with the second electrode, and a first polymer layer outside the first interference zapping layer A probe according to any one of claims 23 to 25, comprising:

27. A second interference zapping layer outside the first polymer layer, and a second polymer layer outside the second interference zapping layer The probe according to claim 26, comprising:

28. wherein the first enzyme layer contains glucose oxidase, the second enzyme layer contains catalase, The probe according to claim 26.

29. Applying a first potential to the interference layer, the first potential being sufficient to oxidize at least one electrochemical interference substance and the molecule of interest; Measuring a first background current of the first electrode; Measuring a second background current of the second electrode; Applying a second potential to the interference layer, the second potential being sufficient to oxidize at least one electrochemical interference substance but not sufficient to oxidize the molecule of interest; Measuring a first current of the first electrode; Measuring a second current of the second electrode; Determining an estimated value of the concentration of the target molecule based at least in part on the measured values of the first background current, the second background current, the first current, and the second current A method of using an electrochemical probe, comprising:

30. The method according to claim 29, wherein the target molecule comprises glucose.

31. The method according to claim 29 or 30, wherein the first potential is in the range of +0.5 to +1.5 V.

32. The method according to claim 31, wherein the first potential is in the range of +0.6 to +1.1 V.

33. The method according to claim 29 or 30, wherein the second potential is in the range of +0.3 to +1.1 V.

34. The method according to claim 33, wherein the second potential is in the range of +0.4 to 0.7 V.

35. A method of using an electrochemical probe comprising an interference zapping layer and a working electrode, comprising: Applying a first plurality of potentials to the interference zapping layer; Applying a second plurality of potentials to the working electrode; Measuring a plurality of currents of the working electrode, each of the plurality of currents being measured while the interference zapping layer is set to one of the first plurality of potentials and while the working electrode is set to one of the second plurality of potentials; Determining an estimated value of the concentration of the analyte based at least in part on the measured plurality of currents using a hardware processor A method comprising:

36. The method according to claim 35, comprising determining an estimated value of the concentration of the plurality of analytes based at least in part on the measured plurality of currents.

37. The method according to claim 35 or 36, wherein the step of applying the first plurality of potentials to the interference layer comprises sequentially applying the first plurality of potentials.

38. The method according to any one of claims 35 to 37, wherein the step of applying the second plurality of potentials to the working electrode comprises sequentially applying the second plurality of potentials.

39. The method according to any one of claims 35 to 38, wherein each of the plurality of currents is measured with a different combination of one of the first plurality of potentials and one of the second plurality of potentials.

40. The method according to any one of claims 35 to 39, wherein the first plurality of potentials are a series of potentials having a step of Δ0.1 V between each of the first plurality of potentials.

41. The method according to any one of claims 35 to 40, wherein the second plurality of potentials are a series of potentials having a step of Δ0.1 V between each of the first plurality of potentials.

42. The method according to any one of claims 35 to 41, wherein while the interference layer is held at one of the first plurality of potentials, the potential applied to the working electrode changes stepwise between the second plurality of potentials.

43. The method according to any one of claims 35 to 42, wherein while the working electrode is held at one of the second plurality of potentials, the potential applied to the interference electrode changes stepwise between the first plurality of potentials.

44. The method according to any one of claims 35 to 43, which does not include a calibration step.

45. A method of using an electrochemical probe comprising an interference zapping layer and a working electrode, applying a first plurality of potentials to the interference zapping layer; applying a second plurality of potentials to the working electrode; measuring a first plurality of currents of the working electrode, each of the first plurality of currents being measured while the interference zapping layer is set to one of the first plurality of potentials and while the working electrode is set to one of the second plurality of potentials; determining a third plurality of potentials using a hardware processor, the third plurality of potentials including at least a part of the first plurality of potentials; determining a fourth plurality of potentials using a hardware processor, the fourth plurality of potentials including at least a part of the first plurality of potentials; measuring a second plurality of currents of the working electrode, each of the second plurality of currents being measured while the interference zapping layer is set to one of the third plurality of potentials and while the working electrode is set to one of the fourth plurality of potentials and including.

46. The third plurality of potentials consists of at least one of the first plurality of potentials, The fourth plurality of potentials consists of at least one of the second plurality of potentials. The method according to claim 45.

47. The method according to claim 45 or 46, wherein the step of determining the third plurality of potentials is at least partially based on the first plurality of currents indicative of the analyte.

48. The method according to any one of claims 45 to 47, wherein the step of determining the fourth plurality of potentials is at least partially based on the first plurality of currents indicative of the analyte.

49. The method according to any one of claims 45 to 48, wherein the second plurality of currents includes a current less than the first plurality of currents.

50. The method according to any one of claims 45 to 49, wherein the step of measuring the second plurality of currents is faster than the step of measuring the first plurality of currents.

51. The method according to any one of claims 45 to 50, wherein the step of measuring the second plurality of currents requires less power than the step of measuring the first plurality of currents.

52. A method of using an electrochemical probe comprising an interference zapping layer and a working electrode, applying a first plurality of potentials to the interference zapping layer; applying a second plurality of potentials to the working electrode; measuring a plurality of currents of the working electrode, each of the plurality of currents being measured while the interference zapping layer is set to one of the first plurality of potentials and while the working electrode is set to one of the second plurality of potentials; constructing a data structure using a hardware processor; determining an estimated value of the analyte concentration using the hardware processor based at least in part on the data structure; and including.

53. The method according to claim 52, including the step of displaying the analyte concentration on a display.

54. The method according to claim 52 or 53, wherein the data structure is an array.

55. The method according to any one of claims 52 to 54, wherein the data structure is a heat map.

56. The method according to any one of claims 52 to 55, wherein the data structure is a three-dimensional plot.

57. The method according to any one of claims 52 to 56, wherein the step of determining the estimated value of the analyte concentration includes comparing the data structure with a reference data structure.

58. The method according to claim 57, wherein the control data structure includes a measured current value of the control target.

59. The method according to claim 57, wherein the control data structure includes a measured current value of the control fluid.

60. The method according to claim 59, wherein the control data structure includes previous measured values of a plurality of previous currents of the patient.

61. The method according to claim 60, comprising the step of using the hardware processor to identify a physiological change based at least in part on a difference between the data structure and the previous measured values.

62. The method according to any one of claims 52 to 61, comprising the step of disposing the interference zapping layer and the working electrode in the interstitial fluid of the patient.

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