Methods for improved sensor sensitivity in microneedle-based continuous analyte monitoring systems

Abstract

Variations of analyte monitoring systems, including analyte monitoring devices, are described herein. For example, the analyte monitoring device may include an implantable microneedle array for use in measuring one or more analytes (e.g., glucose), such as in a continuous manner. Each microneedle of the microneedle array may include a microneedle body, an electrode material on the microneedle body, a biorecognition layer on the electrode material, a diffusion-limiting layer on the biorecognition layer, an interferent-blocking agent, and / or an adhesion-enhancing agent between the biorecognition layer and the diffusion-limiting layer, where the interferent-blocking agent and the adhesion-enhancing agent are configured to improve variability in sensor sensitivity.

Description

[Technical Field]

[0001] (CROSS-REFERENCE TO RELATED APPLICATIONS) This application claims the benefit of U.S. Provisional Patent Application Nos. 63 / 443,010, filed February 2, 2023, 63 / 443,024, filed February 2, 2023, and 63 / 613,566, filed December 21, 2023, the contents of each of which are incorporated herein by reference in their entirety.

[0002] FIELD OF THE INVENTION The present invention relates generally to the field of analyte monitoring, such as continuous glucose monitoring. [Background technology]

[0003] Diabetes is a chronic disease in which the body does not produce or properly utilize insulin, the hormone that regulates blood glucose. Although insulin can be administered to diabetic patients to help regulate blood glucose levels, blood glucose levels must still be carefully monitored to help ensure that the timing and dosage are appropriate. If diabetic patients do not properly manage their condition, they can suffer from a variety of complications resulting from hyperglycemia (high blood sugar levels) or hypoglycemia (low blood sugar levels).

[0004] Blood glucose monitors help diabetic patients manage their condition by measuring blood glucose levels from a blood sample. For example, a diabetic patient may collect a blood sample via a finger-prick sampling mechanism, transfer the blood sample to a test strip with suitable reagent(s) that reacts with the blood sample, and use a blood glucose monitor to analyze the test strip and measure the glucose level in the blood sample. However, patients using this process are typically only able to measure their glucose levels at discrete time instances and may not be able to timely capture hyperglycemic or hypoglycemic conditions. A more recent variety of glucose monitor is the continuous glucose monitor (CGM) device, which includes an implantable transcutaneous electrochemical sensor used to continuously detect and quantify blood glucose levels by proxy measuring glucose levels in subcutaneous interstitial fluid. However, conventional CGM devices also have weaknesses, including tissue trauma from insertion and signal delay (e.g., due to the time required for the glucose analyte to diffuse from a capillary source to the sensor). These weaknesses also lead to several drawbacks, such as the pain experienced by the patient when the electrochemical sensor is inserted and limited accuracy of glucose measurements, especially when blood glucose levels are changing rapidly. Therefore, there is a need for new and improved analyte monitoring systems. Summary of the Invention [Means for solving the problem]

[0005] According to an embodiment, the present disclosure relates to a system and method for improving the stability of a microneedle-based continuous analyte monitoring system.

[0006] In a variation, the present disclosure further relates to a device for use in sensing an analyte, the device comprising: a microneedle; an electrode material on the microneedle; a biorecognition layer on the electrode material, the biorecognition layer comprising a polymer, a biorecognition element configured to react with the analyte, and an interferent-blocking agent filling voids in the polymer; and a diffusion-limiting layer on the biorecognition layer, hi a variation, the voids in the polymer run through the thickness of the polymer. In variations, the interferent blocking agent is a non-conductive polymer, at least a portion of which contacts the electrode material, and / or the interferent blocking agent fills at least about 80% of the voids in the polymer to limit access to the electrode material by interferents, and / or the interferent blocking agent comprises one or more of resorcinol, hydroquinone quinol, 2-amino-4,6-dinitrophenol picramic acid, 3,5-dihydroxytoluene orcinol, 2,4,6-trinitroresorcinol styphnic acid, 2-hydroxyphenol catechol, 9-phenanthrol, pyrogallol, α-napthol, anisole, phenetole, picric acid, and phenol. In a variation, the biorecognition element is in a polymer, and / or the biorecognition element is glucose oxidase, glucose dehydrogenase, 3-hydroxybutyrate dehydrogenase, or lactate dehydrogenase, and the polymer comprises one or more of aniline, acetylene, phenylene, phenylene vinylene, phenylenediamine, thiophene, 3,4-ethylenedioxythiophene, and aminophenylboronic acid. In a variation, the diffusion-limiting layer is hydrophobic, and / or the diffusion-limiting layer comprises one or more of polydimethylsiloxane, polyurethane, polyvinyl chloride, polyvinylpyrrolidone, polycarbonate, polyethylene, polyethylene terephthalate, polyester, high-density polyethylene, low-density polyethylene, and polytetrafluoroethylene. In a variation, the analyte comprises one or more of glucose, ketone, and lactate. In a variation, the electrode material comprises platinum, palladium, iridium, rhodium, gold, ruthenium, titanium, nickel, carbon, doped diamond, or a combination thereof.In a variation, the interference current in the electrode material of the device changes by less than 70% over a one-week period, and / or the interference current in the electrode material of the device changes by less than 10% over a one-week period. In a variation, at least a portion of the voids are exposed at the surface of the electrode material. In a variation, the biorecognition element is physically trapped within the polymer. In a variation, the interferent blocker comprises phenol. In a variation, the phenol is present in the biorecognition layer at a concentration of about 0.1 mg / mL or 0.01% w / v to about 10 mg / mL or 1% w / v, and / or the polymerized phenol is trapped within the voids of the polymer.

[0007] In a variation, the present disclosure further relates to a method of manufacturing a device for use in sensing an analyte, the method comprising: depositing a biorecognition element and a polymer on an electrode material disposed on a microneedle; applying an interferent blocking agent to the polymer after deposition, thereby filling voids in the polymer with the interferent blocking agent; and depositing a diffusion-limiting layer on the polymer. In a variation, the biorecognition element is configured to react with the analyte. In a variation, the applying comprises electropolymerizing the interferent blocking agent. In a variation, the interferent blocking agent comprises phenol and is applied as a mixture having a concentration of about 1 mM phenol to about 100 mM phenol.

[0008] In a variation, the present disclosure further relates to a device for use in analyte sensing, the device comprising: a microneedle; an electrode material on the microneedle; a biorecognition layer on the electrode material, the biorecognition layer including a polymer, a biorecognition element configured to react with the analyte, and an interferent-blocking agent filling voids in the polymer; a diffusion-limiting layer; and an adhesion-enhancing agent configured to reduce variability in analyte sensing, the adhesion-enhancing agent being positioned between the biorecognition layer and the diffusion-limiting layer. In a variation, the adhesion-enhancing agent comprises a plurality of molecules, a first end of each of the plurality of molecules being covalently bound to the biorecognition layer. In a variation, the adhesion-enhancing agent comprises a plurality of molecules, a second end of each of the plurality of molecules being partially immobilized within the diffusion-limiting layer. In a variation, the adhesion-enhancing agent is covalently bound to the biorecognition element. In a variation, the biorecognition element is glucose oxidase, and the adhesion-enhancing agent is covalently bound to the glucose oxidase. In a variation, the polymer comprises one or more of aniline, acetylene, phenylene, phenylene vinylene, phenylenediamine, thiophene, 3,4-ethylenedioxythiophene, and aminophenylboronic acid. In a variation, at least a portion of the interferent blocking agent is in contact with the electrode material. In a variation, the interferent current in the electrode material of the device changes by less than 10% over a period of one week. In a variation, the second end comprises at least one hydroxyl group and / or the second end interacts with the diffusion-limiting layer via van der Waals forces. In a variation, each of the plurality of molecules is a cross-linker. In a variation, the at least one hydroxyl group forms a hydrogen bond with the diffusion-limiting layer.In a variation, the crosslinker comprises an epoxide functional group and the crosslinker comprises one selected from the group consisting of 1,4-butanediol diglycidyl ether, 1,6-hexanediol diglycidyl ether, neopentyl glycol diglycidyl ether, poly(propylene glycol) diglycidyl ether, trimethylolethane diglycidyl ether, trimethylolethane triglycidyl ether, diglycidyl resorcinol ether, diglycidyl ether, 1,4-cyclohexanedimethanol diglycidyl ether, castor oil glycidyl ether, and bisphenol A diglycidyl ether; and / or the crosslinker comprises one selected from the group consisting of glutaraldehyde, poly(dimethylsiloxane)-diglycidyl ether, tetracyclooxypropyl-4,4-diaminodiphenylmethane, polyethylene glycol diglycidyl ether, and 4-(2,3-epoxypropoxy)-N,N-bis(2,3-epoxypropyl)aniline. In a variation, the crosslinker comprises N(1, 2, 3, 4) epoxide functional groups connected to a linker, hi a variation, the linker is one selected from the group consisting of aromatic, aliphatic, straight chain, and branched chain.

[0009] In a variation, the present disclosure further relates to a method of manufacturing a device for use in analyte sensing, the method comprising: depositing a biorecognition element and a polymer on an electrode material disposed on a microneedle; applying an interferent blocking agent to the polymer, thereby filling voids in the polymer with the interferent blocking agent; exposing the polymer to an adhesion-enhancing agent; and depositing a diffusion-limiting layer on the biorecognition layer after exposing the polymer to the adhesion-enhancing agent. In a variation, the biorecognition element is configured to react with the analyte. In a variation, the applying comprises electropolymerizing the interferent blocking agent. In a variation, the interferent blocking agent comprises phenol and is applied as a mixture having a concentration of about 1 mM phenol to about 100 mM phenol. In a variation, exposing the polymer to the adhesion-enhancing agent comprises one or more of drop-casting, spray-coating, dipping, spin-coating, and chemical vapor deposition, and / or exposing the polymer to the adhesion-enhancing agent comprises immersing the polymer in a buffer solution containing the adhesion-enhancing agent. In variations, the soaking is carried out for a period of from about 5 minutes to about 3 days, and / or the soaking is carried out for a period of more than about 16 hours.

[0010] In a variant, the present disclosure further relates to a device for use in sensing an analyte, the device comprising: a microneedle; an electrode material on the microneedle; and a biorecognition layer on the electrode material, the biorecognition layer comprising a polymer, a biorecognition element configured to react with the analyte, and an interferent blocker filling voids within the polymer.

[0011] In some variations, the present disclosure further relates to a device for use in sensing an analyte, the device comprising: a microneedle; an electrode material on the microneedle; a biorecognition layer on the electrode material, the biorecognition layer comprising a phenylenediamine, a biorecognition element, and a polyphenol, the polyphenol filling voids in the phenylenediamine, and the biorecognition element configured to react with an analyte; and a polyurethane-based diffusion-limiting layer on the biorecognition layer.

[0012] In some variations, the present disclosure further relates to a method of manufacturing a device for use in sensing an analyte, the method comprising depositing a biorecognition element and a polymer on an electrode material disposed on a microneedle, the biorecognition element being configured to react with an analyte, and applying an interferent blocking agent to the polymer after deposition, thereby filling voids within the polymer with the interferent blocking agent.

[0013] In some variations, the present disclosure further relates to a method of manufacturing a device for use in sensing an analyte, the method comprising depositing a biorecognition element and a phenylenediamine on an electrode material disposed on a microneedle, the biorecognition element being configured to react with an analyte; applying a polyphenol to the phenylenediamine after deposition, thereby filling voids within the phenylenediamine with the polyphenol; and depositing a polyurethane-based diffusion-limiting layer on the phenylenediamine.

[0014] In some variations, the present disclosure further relates to a device for use in sensing an analyte, the device comprising: a microneedle; an electrode material on the microneedle; a biorecognition layer on the electrode material, the biorecognition layer comprising a phenylenediamine, a biorecognition element configured to react with an analyte, and a polyphenol filling voids in the phenylenediamine; a polyurethane-based diffusion-limiting layer; and an adhesion enhancer configured to reduce variability in analyte sensing, the adhesion enhancer comprising 1,4-butanediol diglycidyl ether, positioned between the biorecognition layer and the polyurethane-based diffusion-limiting layer.

[0015] In some variations, the present disclosure further relates to a method of manufacturing a device for use in sensing an analyte, the method comprising: depositing a biorecognition element and a phenylenediamine on an electrode material disposed on a microneedle, the biorecognition element being configured to react with an analyte; applying a polyphenol to the phenylenediamine, thereby filling voids within the phenylenediamine with the polyphenol; exposing the phenylenediamine to an adhesion enhancer comprising 1,4-butanediol diglycidyl ether; and depositing a polyurethane-based diffusion-limiting layer on the biorecognition layer after exposing the phenylenediamine to the 1,4-butanediol diglycidyl ether.

[0016] In some variations, the present disclosure further relates to an analyte monitoring device comprising a plurality of microneedles arranged in an array, the microneedles comprising a plurality of working electrodes, a reference electrode, and a counter electrode, the plurality of working electrodes being disposed between the reference electrode and the counter electrode.

[0017] In some variations, the present disclosure further relates to a microneedle array for use in sensing an analyte, the array comprising a plurality of sensing microneedles, each comprising a working electrode with a biorecognition layer, the biorecognition layer comprising a biorecognition element configured to react with an analyte, a first microneedle comprising a counter electrode, and a second microneedle comprising a reference electrode, the plurality of sensing microneedles connected to the first microneedle such that a current flows between the plurality of sensing microneedles and the first microneedle, the current resulting from a potential applied between the plurality of sensing microneedles and the second microneedle, the plurality of sensing microneedles being positioned between the first microneedle and the second microneedle. [Brief explanation of the drawings]

[0018] [Figure 1]1 shows an exemplary schematic diagram of an analyte monitoring system having a microneedle array.

[0019] [Figure 2A] 1 shows an exemplary schematic diagram of an analyte monitoring device. [Figure 2B] 1 shows an exemplary schematic of microneedle insertion depth in an analyte monitoring device.

[0020] [Figure 3A] 1A-1C show top perspective, side, bottom, and exploded views, respectively, of an analyte monitoring device. [Figure 3B] 1A-1C show top perspective, side, bottom, and exploded views, respectively, of an analyte monitoring device. [Figure 3C] 1A-1C show top perspective, side, bottom, and exploded views, respectively, of an analyte monitoring device. [Figure 3D] 1A-1C show top perspective, side, bottom, and exploded views, respectively, of an analyte monitoring device.

[0021] [Figure 4A] 1A-1C show exploded perspective, exploded side, bottom perspective, side, and top perspective views, respectively, of a sensor assembly in an analyte monitoring device. [Figure 4B] 1A-1C show exploded perspective, exploded side, bottom perspective, side, and top perspective views, respectively, of a sensor assembly in an analyte monitoring device. [Figure 4C] 1A-1C show exploded perspective, exploded side, bottom perspective, side, and top perspective views, respectively, of a sensor assembly in an analyte monitoring device. [Figure 4D] 1A-1C show exploded perspective, exploded side, bottom perspective, side, and top perspective views, respectively, of a sensor assembly in an analyte monitoring device. [Figure 4E] 1A-1C show exploded perspective, exploded side, bottom perspective, side, and top perspective views, respectively, of a sensor assembly in an analyte monitoring device. [Figure 4F]1A-1C show exploded perspective, exploded side, and side views, respectively, of a sensor assembly in an analyte monitoring device. [Figure 4G] 1A-1C show exploded perspective, exploded side, and side views, respectively, of a sensor assembly in an analyte monitoring device. [Figure 4H] 1A-1C show exploded perspective, exploded side, and side views, respectively, of a sensor assembly in an analyte monitoring device.

[0022] [Figure 5A] 1 shows an exemplary schematic diagram of a microneedle array. [Figure 5B] 5B shows an exemplary schematic diagram of a microneedle of the microneedle array shown in FIG. 5A.

[0023] [Figure 6] FIG. 1 shows an exemplary schematic diagram of a microneedle array used for sensing multiple analytes.

[0024] [Figure 7A] FIG. 1 shows a cross-sectional side view of a pillar-shaped microneedle with a tapered distal end. [Figure 7B] 7B and 7C are images showing a perspective view and a detailed view, respectively, of a variation of the microneedle shown in FIG. 7A. [Figure 7C] 7B and 7C are images showing a perspective view and a detailed view, respectively, of a variation of the microneedle shown in FIG. 7A.

[0025] [Figure 8] FIG. 1 shows an exemplary schematic diagram of a pillar-shaped microneedle with a tapered distal end.

[0026] [Figure 9A] 1A and 1B show exemplary schematic diagrams of a microneedle array and a microneedle, respectively. [Figure 9B] 1A and 1B show exemplary schematic diagrams of a microneedle array and a microneedle, respectively. [Figure 9C]1 shows a detailed partial view of an exemplary variation of a microneedle. [Figure 9D] 1 shows a detailed partial view of an exemplary variation of a microneedle. [Figure 9E] 1 shows a detailed partial view of an exemplary variation of a microneedle. [Figure 9F] 1 shows a detailed partial view of an exemplary variation of a microneedle.

[0027] [Figure 10A] 1 illustrates exemplary variations of microneedles. [Figure 10B] 1 illustrates exemplary variations of microneedles.

[0028] [Figure 11A] 1A and 1B show exemplary schematic diagrams of the layered structure of the working electrode, counter electrode, and reference electrode, respectively. [Figure 11B] 1A and 1B show exemplary schematic diagrams of the layered structure of the working electrode, counter electrode, and reference electrode, respectively. [Figure 11C] 1A and 1B show exemplary schematic diagrams of the layered structure of the working electrode, counter electrode, and reference electrode, respectively.

[0029] [Figure 11D] 1 shows an exemplary schematic diagram of the layered structure of a working electrode. [Figure 11E] 1 shows an exemplary schematic diagram of the layered structure of a working electrode. [Figure 11F] 1 shows an exemplary schematic diagram of the layered structure of a working electrode. [Figure 11G] 1 shows an exemplary schematic diagram of the layered structure of a working electrode. [Figure 11H] 1 shows an exemplary schematic diagram of the layered structure of a working electrode. [Figure 11I] 1 shows an exemplary schematic diagram of the layered structure of a working electrode. [Figure 11J] 1 shows an exemplary schematic diagram of the layered structure of a working electrode. [Figure 11K] 1 shows an exemplary schematic diagram of the layered structure of a working electrode. [Figure 11L]1 shows an exemplary schematic diagram of the layered structure of a working electrode. [Figure 11M] 1 shows an exemplary schematic diagram of the layered structure of a working electrode. [Figure 11N] 1 shows an exemplary schematic diagram of the layered structure of a working electrode.

[0030] [Figure 11O] 1 shows an exemplary schematic diagram of the layered structure of a counter electrode. [Figure 11P] 1 shows an exemplary schematic diagram of the layered structure of a counter electrode. [Figure 11Q] 1 shows an exemplary schematic diagram of the layered structure of a counter electrode. [Figure 11R] 1 shows an exemplary schematic diagram of the layered structure of a counter electrode. [Figure 11S] 1 shows an exemplary schematic diagram of the layered structure of a counter electrode. [Figure 11T] 1 shows an exemplary schematic diagram of the layered structure of a counter electrode. [Figure 11U] 1 shows an exemplary schematic diagram of the layered structure of a counter electrode. [Figure 11V] 1 shows an exemplary schematic diagram of the layered structure of a counter electrode.

[0031] [Figure 11W] 1 shows an exemplary schematic diagram of the layered structure of a reference electrode. [Figure 11X] 1 shows an exemplary schematic diagram of the layered structure of a reference electrode. [Figure 11Y] 1 shows an exemplary schematic diagram of the layered structure of a reference electrode. [Figure 11Z] 1 shows an exemplary schematic diagram of the layered structure of a reference electrode.

[0032] [Figure 12A] 1 shows an exemplary schematic diagram of an adhesion enhancer interacting with electrode components and layers. [Figure 12B] 1 shows an exemplary schematic diagram of an adhesion enhancer interacting with electrode components and layers.

[0033] [Figure 13A]1 is an exemplary flow chart of a method for improving adhesion within and / or between layered structures of a working electrode. [Figure 13B] 1 is an exemplary flow chart of a method for improving adhesion within and between layered structures of a counter electrode. [Figure 13C] 1 is an exemplary flow chart of a method for improving adhesion within and between layer structures of a reference electrode. [Figure 13D] 1 is an exemplary flowchart of a method for forming a layered structure of a working electrode. [Figure 13E] 1 is an exemplary flow chart of a method for improving adhesion within and / or between layered structures of a working electrode and reducing interference currents. [Figure 13F] 1 is an exemplary flowchart of a method for reducing interference current at a working electrode.

[0034] [Figure 14] 1 shows an exemplary schematic diagram of the arrangement of electrodes in a microneedle array.

[0035] [Figure 15] 1 shows an exemplary schematic diagram of a microneedle array configuration.

[0036] [Figure 16A] 1A-1D show exemplary schematic diagrams of different variations of microneedle array configurations. [Figure 16B] 1A-1D show exemplary schematic diagrams of different variations of microneedle array configurations. [Figure 16C] 1A-1D show exemplary schematic diagrams of different variations of microneedle array configurations. [Figure 16D] 1A-1D show exemplary schematic diagrams of different variations of microneedle array configurations. [Figure 16E] 1A-1D show exemplary schematic diagrams of different variations of microneedle array configurations. [Figure 16F] 1A-1D show exemplary schematic diagrams of different variations of microneedle array configurations. [Figure 16G] 1A-1D show exemplary schematic diagrams of different variations of microneedle array configurations. [Figure 16H] 1A-1D show exemplary schematic diagrams of different variations of microneedle array configurations. [Figure 16I] 1A-1D show exemplary schematic diagrams of different variations of microneedle array configurations. [Figure 16J] 1A-1D show exemplary schematic diagrams of different variations of microneedle array configurations.

[0037] [Figure 17A] 1 shows an exemplary schematic diagram of a microneedle array configuration. [Figure 17B] 1 shows an exemplary schematic diagram of a microneedle array configuration. [Figure 17C] 1 shows an exemplary schematic diagram of a microneedle array configuration. [Figure 17D] 1 shows an exemplary schematic diagram of a microneedle array configuration. [Figure 17E] 1 shows an exemplary schematic diagram of a microneedle array configuration. [Figure 17F] 1 shows an exemplary schematic diagram of a microneedle array configuration.

[0038] [Figure 18A] 1 shows a schematic diagram of a microneedle array sensor model. [Figure 18B] 1 shows a schematic diagram of a microneedle array sensor model.

[0039] [Figure 19A] FIG. 1 shows a schematic diagram of a microneedle array sensor model with a stabilized working electrode configuration. [Figure 19B] FIG. 1 shows a schematic diagram of a microneedle array sensor model with a stabilized working electrode configuration.

[0040] [Figure 20A] 1A-1D show exemplary schematic diagrams of different variations of microneedle array configurations. [Figure 20B]1A-1D show exemplary schematic diagrams of different variations of microneedle array configurations. [Figure 20C] 1A-1D show exemplary schematic diagrams of different variations of microneedle array configurations. [Figure 20D] 1A-1D show exemplary schematic diagrams of different variations of microneedle array configurations. [Figure 20E] 1A-1D show exemplary schematic diagrams of different variations of microneedle array configurations. [Figure 20F] 1A-1D show exemplary schematic diagrams of different variations of microneedle array configurations.

[0041] [Figure 21A] 10 shows exemplary data demonstrating the effect of adhesion enhancer concentration on sensor sensitivity. [Figure 21B] 10 shows exemplary data demonstrating the effect of adhesion enhancer concentration on sensor sensitivity. [Figure 21C] 10 shows exemplary data demonstrating the effect of adhesion enhancer concentration on sensor sensitivity. [Figure 21D] 10 shows exemplary data demonstrating the effect of adhesion enhancer concentration on sensor sensitivity. [Figure 21E] 10 shows exemplary data demonstrating the effect of adhesion enhancer concentration on sensor sensitivity. [Figure 21F] 10 shows exemplary data demonstrating the effect of adhesion enhancer concentration on sensor sensitivity. [Figure 21G] 10 shows exemplary data demonstrating the effect of adhesion enhancer concentration on sensor sensitivity. [Figure 21H] 10 shows exemplary data demonstrating the effect of adhesion enhancer concentration on sensor sensitivity. [Figure 21I] 10 shows exemplary data demonstrating the effect of adhesion enhancer concentration on sensor sensitivity. [Figure 21J] 10 shows exemplary data demonstrating the effect of adhesion enhancer concentration on sensor sensitivity.

[0042] [Figure 22A]10 shows exemplary data demonstrating the effect of adhesion enhancer concentration on sensor stability under electrical current. [Figure 22B] 10 shows exemplary data demonstrating the effect of adhesion enhancer concentration on sensor stability under electrical current. [Figure 22C] 10 shows exemplary data demonstrating the effect of adhesion enhancer concentration on sensor stability under electrical current. [Figure 22D] 10 shows exemplary data demonstrating the effect of adhesion enhancer concentration on sensor stability under electrical current.

[0043] [Figure 23] 10 shows exemplary data demonstrating the effect of adhesion enhancer concentration on sensor stability after 5 days.

[0044] [Figure 24A] 10 presents exemplary data demonstrating the improved sensor stability achieved by using an adhesion enhancer. [Figure 24B] 10 presents exemplary data demonstrating the improved sensor stability achieved by using an adhesion enhancer.

[0045] [Figure 25] 10 shows exemplary data demonstrating the effect of using an adhesion enhancer on the phase angle and impedance of a sensor.

[0046] [Figure 26A] 10 shows data demonstrating the effect of exemplary interferent blockers on sensor sensitivity. [Figure 26B] 10 shows data demonstrating the effect of exemplary interferent blockers on sensor sensitivity to acetaminophen as an interferent analog.

[0047] [Figure 27] 10 shows data demonstrating the effect of the concentration of an exemplary interferent blocker on sensor sensitivity.

[0048] [Figure 28A]10 shows time series data demonstrating the effect of the concentration of an exemplary interferent blocker on sensor sensitivity to acetaminophen as an interferent analog. [Figure 28B] 10 shows time series data demonstrating the effect of the concentration of an exemplary interferent blocker on sensor sensitivity to acetaminophen as an interferent analog. [Figure 28C] 10 shows time series data demonstrating the effect of the concentration of an exemplary interferent blocker on sensor sensitivity to acetaminophen as an interferent analog.

[0049] [Figure 29] 10 shows time series data demonstrating the effect of the concentration of an exemplary interferent blocker on sensor sensitivity to different concentrations of acetaminophen as an interferent analog. DETAILED DESCRIPTION OF THE INVENTION

[0050] The term "a" or "an" may refer to one or more of that entity, i.e., to a plurality of referents. Similarly, the terms "a," "an," "one or more," and "at least one" are used interchangeably herein. In addition, reference to an "element" by the indefinite article "a" or "an" does not exclude the possibility that more than one of the element is present, unless the context clearly requires that there be only one element.

[0051] Throughout this application, the term "about" is used to indicate that a value includes the inherent variation of error for the device or method employed to determine the value or the variation that exists between samples measured. Unless otherwise stated or apparent from the context, the term "about" means within 10% above or below the reported numerical value (except where such numerical value would exceed 100% or be less than 0% of the possible values). When used in conjunction with a range or series of values, the term "about" applies to the endpoints of the range or to each of the values ​​recited in the series of ranges, unless otherwise indicated. As used herein, the terms "about" and "approximately" are used interchangeably.

[0052] Aptamers are single-stranded oligonucleotides or peptides that fold into a predetermined structure to selectively bind to a specific analyte (sometimes referred to as a target), which can be, for example, a protein, peptide, hormone, nucleic acid, or small molecule. Aptamers with affinity for a desired target can traditionally be selected from large oligonucleotide libraries by a process called SELEX (Systematic Evolution of Ligands by Exponential Enrichment). Through an iterative process, non-binding aptamers are discarded, and aptamers that bind to the proposed target are amplified by polymerase chain reaction (PCR). The iterative process may include counterselection (using interferents and structurally similar molecules) to discard aptamers with insufficient selectivity for the analyte. Furthermore, the structural changes in the aptamer resulting from target binding and dissociation can be used to induce electrical, electrochemical, or chemical changes that can be utilized to visualize target binding / dissociation via an assay or sensor. If necessary, selected aptamers can be further modified (e.g., by truncation and mutation) to improve the structural changes of the aptamer and thereby improve the sensor signal. These properties make aptamers attractive "bio-recognition" elements for use in detecting one or more desired analytes.

[0053] For example, in an aptamer-based sensor, the surface of a working electrode may be functionalized with an aptamer (analyte-binding aptamer) configured to selectively and reversibly bind to a given analyte. The aptamer may be further modified by the addition of a redox-active molecule. The aptamer may be configured such that, upon binding to the analyte, the analyte-binding aptamer undergoes a conformational change that moves the redox-active molecule closer to or further away from the electrode. The movement of the redox-active molecule can be detected as an analyte concentration-dependent electrochemical signal.

[0054] Non-limiting examples of various aspects and variations of the present invention are described herein and illustrated in the accompanying drawings.

[0055] Blood glucose monitors help diabetic patients manage their condition by measuring blood glucose levels from a blood sample. For example, a diabetic patient may collect a blood sample via a finger-prick sampling mechanism, transfer the blood sample to a test strip with suitable reagent(s) that reacts with the blood sample, and use a blood glucose monitor to analyze the test strip and measure the glucose level in the blood sample. However, patients using this process are typically only able to measure their glucose levels at discrete time instances and may not be able to timely capture hyperglycemic or hypoglycemic conditions. A more recent variety of glucose monitor is the continuous glucose monitor (CGM) device, which includes an implantable transcutaneous electrochemical sensor used to continuously detect and quantify blood glucose levels by proxy measuring glucose levels in subcutaneous interstitial fluid. However, conventional CGM devices also have drawbacks, such as tissue trauma upon insertion that can cause pain to the patient, signal delay (e.g., due to the time required for glucose analyte to diffuse from a capillary source to the sensor), signal noise, sensor damage caused by insertion, and sensor fatigue (or degradation) during the implantation period. For example, sensor damage and sensor fatigue can result in increased sensor sensitivity and an increased likelihood of outlier measurements.

[0056] Conventional CGM devices may include an electrode "stack" comprising one or more of a base layer, an electrode layer, a sensing layer, an insulating layer, a selective layer, a glucose and / or oxygen diffusion membrane, and a cover / protective layer; sources of signal noise, sensor damage, and sensor fatigue in such devices include poor interfaces between the sensing layer (e.g., enzyme-containing layer) and other layers or coatings disposed thereon (e.g., selective layer, insulating layer, protective layer, etc.), or between the sensing layer (e.g., enzyme-containing layer) and the electrode layer, and chemical voids within the sensing layer that expose the electrode layer to interferents.

[0057] For example, interface defects may include layer delamination, interfacial imperfections, interfacial irregularities between the outer membrane and the sensing layer, interfacial irregularities between the sensing layer and the electrode material, etc., which can directly contribute to variability in analyte sensor sensitivity and / or inconsistent sensitivity trends over time, generally reducing the accuracy of analyte measurements.

[0058] Chemical voids in the sensing layer undesirably expose the surface of the electrode layer to interfering substances (also referred to herein as "interfering currents") that increase signal noise. Exposure of the electrode surface to such voids and interfering substances can result in nonspecific currents that overwhelm the glucose-catalyzed current, thereby reducing the accuracy, sensitivity, and lifetime of the biosensor.

[0059] To ameliorate the above-mentioned sensor interface defects and interference currents, the devices, systems, and methods described herein may utilize an electrode "stack" that includes one or more of an interferent blocker and an adhesion enhancer (also referred to herein as "promoters"). In some variations, the interferent blocker may be configured to fill at least a portion of the chemical voids in the sensing layer, reducing exposure of the electrode layer surface to interferents. Thus, including an interferent blocker in the sensing layer can reduce background interference, for example, over at least one week, thereby improving sensitivity. Additionally or alternatively, the adhesion enhancer may be configured to bridge and adhere the sensing layer, outer membrane, electrode material, and / or any other layers in the electrode "stack." In this manner, including an adhesion enhancer can reduce sensor sensitivity and variability in sensor sensitivity. It should be understood that the adhesion-enhancing agents and interferent-blocking agents are configured to provide different functionalities to the electrode "stack" and therefore may be used together (i.e., the electrode stack may include both an adhesion-enhancing agent and an interferent-blocking agent), or separately (i.e., the electrode stack may include an adhesion-enhancing agent but not an interferent-blocking agent, or the electrode stack may include an interferent-blocking agent but not an adhesion-enhancing agent), and in combination with any other layer of the electrode "stack" as described herein.

[0060] As generally described herein, an analyte monitoring system may include an analyte monitoring device worn by a user and including one or more sensors for monitoring at least one analyte in the user. The sensor may include, for example, one or more electrodes configured to perform electrochemical detection of at least one analyte. The analyte monitoring device may communicate sensor data to an external computing device for storage, display, and / or analysis of the sensor data. For example, as shown in FIG. 1 , analyte monitoring system 100 may include analyte monitoring device 110 worn by a user, which may be a continuous analyte monitor (e.g., a continuous glucose monitor). Analyte monitoring device 110 may include, for example, a microneedle array including at least one electrochemical sensor for detecting and / or measuring one or more analytes in the user's bodily fluid. In some variations, the analyte monitoring device may be applied to the user using a suitable applicator 160 or may be applied manually. The analyte monitoring device 110 may include one or more processors for performing analysis of the sensor data and / or a communication module (e.g., a wireless communication module) configured to communicate the sensor data to the mobile computing device 102 (e.g., a smartphone) or other suitable computing device. In some variations, the mobile computing device 102 may include one or more processors for executing a mobile application to process the sensor data (e.g., display the data, analyze the data for trends, etc.) and / or provide appropriate alerts or other notifications related to the sensor data and / or its analysis. It should be understood that in some variations, the mobile computing device 102 may perform the sensor data analysis locally, while other computing devices may alternatively or additionally analyze the sensor data and / or communicate information related to such analysis to the mobile computing device 102 (or other suitable user interface) for display to a user.Additionally, in some variations, the mobile computing device 102 may be configured to communicate the sensor data and / or analysis of the sensor data to one or more storage devices 106 (e.g., a server) via the network 104 for archiving data and / or other suitable information related to the user of the analyte monitoring device.

[0061] The analyte monitoring devices described herein have features that improve upon several advantageous properties of continuous analyte monitoring devices, such as continuous glucose monitoring (CGM) devices. For example, the analyte monitoring devices described herein have improved sensitivity (the amount of sensor signal generated per given concentration of target analyte), improved selectivity (rejection of endogenous and exogenous circulating compounds that may interfere with the detection of the target analyte), and improved stability, helping to minimize changes in sensor response over time due to storage and operation of the analyte monitoring device. Furthermore, compared to conventional continuous analyte monitoring devices, the analyte monitoring devices described herein have a shorter warm-up time that allows the sensor to quickly provide a stable sensor signal after implantation, as well as a shorter response time that allows the sensor to quickly provide a stable sensor signal after changes in the user's analyte concentration. Furthermore, as described in more detail below, the analyte monitoring devices described herein can be applied to and function within a variety of application sites, providing the user with painless sensor insertion. Other properties, such as biocompatibility, sterilizability, and mechanical integrity, are also optimized in the analyte monitoring devices described herein.

[0062] While the analyte monitoring systems described herein may be described with reference to monitoring glucose (e.g., in users with type 2 diabetes, type 1 diabetes), it should be understood that such systems may additionally or alternatively be configured to sense and monitor other suitable analytes. As described in further detail below, suitable target analytes for detection may include, for example, glucose, ketones, lactate, and cortisol. A single target analyte may be monitored, or multiple target analytes may be monitored simultaneously (e.g., in the same analyte monitoring device). For example, monitoring other target analytes may enable monitoring of other indications, such as stress (e.g., through detection of elevated cortisol and glucose) and ketoacidosis (e.g., through detection of elevated ketones).

[0063] Various aspects of exemplary variations of the analyte monitoring system and methods of use are described in further detail below. Analyte Monitoring Devices

[0064] As shown in FIG. 2A , in some variations, the analyte monitoring device 110 may generally include a housing 112 and a microneedle array 140 extending outwardly from the housing. The housing 112 may be a wearable housing configured to be attached to a user's skin, such that the microneedle array 140 extends at least partially into the user's skin. For example, the housing 112 may include an adhesive such that the analyte monitoring device 110 is a simple and easy skin-adhesive patch for application to a user. The microneedle array 140 is configured to pierce the user's skin and may include one or more electrochemical sensors (e.g., electrodes) configured to measure one or more target analytes accessible after the microneedle array 140 pierces the user's skin. In some variations, the analyte monitoring device 110 may be integrated or self-contained as a single unit, and the unit may be disposable (e.g., used for a period of time and replaced with another instance of the analyte monitoring device 110).

[0065] The electronics system 120 is disposed at least partially within the housing 112 and can include various electronic components, such as a sensor circuit 124 configured to perform signal processing (e.g., biasing and readout of an electrochemical sensor, converting analog signals from the electrochemical sensor to a digital signal, etc.). The electronics system 120 can also include at least one microcontroller 122 for controlling the analyte monitoring device 110, at least one communications module 126, at least one power source 130, and / or various other suitable passive circuitry 127. The microcontroller 122 can be configured, for example, to interpret digital signals output from the sensor circuit 124 (e.g., by executing routines programmed in firmware), perform various suitable algorithms or mathematical transformations (e.g., calibration, etc.), and / or route processed data to or from the communications module 124. In some variations, the communications module 126 can include a suitable wireless transceiver (e.g., a Bluetooth transceiver, etc.) for communicating data with the external computing device 102 via one or more antennas 128. For example, the communications module 126 may be configured to provide unidirectional and / or bidirectional communication of data with an external computing device 102 paired with the analyte monitoring device 110. The power source 130 may provide power to the analyte monitoring device 110, for the electronics system, and the like. The power source 130 may include a battery or other suitable power source and, in some variations, may be rechargeable and / or replaceable. The passive circuitry 127 may include various unpowered electrical circuits (e.g., resistors, capacitors, inductors, etc.) that provide interconnections between other electronic components, and the like. The passive circuitry 127 may be configured to perform, for example, noise reduction, biasing, and / or other purposes. In some variations, the electronic components within the electronics system 120 may be disposed on one or more printed circuit boards (PCBs), which may be, for example, rigid, semi-rigid, or flexible. Further details of the electronics system 120 are described further below.

[0066] In some variations, the analyte monitoring device 110 may further include one or more additional sensors 150 to provide additional information that may be relevant to user monitoring. For example, the analyte monitoring device 110 may further include at least one temperature sensor (e.g., a thermistor) configured to measure skin temperature, thereby enabling temperature compensation of sensor measurements obtained by the microneedle array electrochemical sensor.

[0067] In some variations, the microneedle array 140 of the analyte monitoring device 110 may be configured to pierce a user's skin. As shown in FIG. 2B, when the device 110 is worn by a user, the microneedle array 140 may extend into the user's skin such that electrodes on distal regions of the microneedles reside in the dermis. Specifically, in some variations, the microneedles may be designed to penetrate the skin and access upper skin regions of the skin (e.g., the papillary dermis and upper reticular dermis) to allow the electrodes to access the interstitial fluid surrounding the cells of these layers. For example, in some variations, the microneedles may generally have a height ranging from at least 350 μm to about 515 μm. In some variations, one or more microneedles may extend from the housing such that the distal ends of the electrodes on the microneedles are positioned less than about 5 mm from the skin-contacting surface of the housing, less than about 4 mm from the housing, less than about 3 mm from the housing, less than about 2 mm from the housing, or less than about 1 mm from the housing.

[0068] In contrast to conventional continuous analyte monitoring devices (e.g., CGM devices), which typically include sensors implanted about 8 mm to about 10 mm below the skin surface in the subcutaneous tissue or fat layer of the skin, the analyte monitoring device 110 has a shallower microneedle insertion depth of about 0.25 mm (such that the electrodes are implanted in the upper dermal region of the skin), which provides many advantages. These advantages include access to skin interstitial fluid, which contains one or more target analytes for detection, since at least some analyte measurements in skin interstitial fluid have been found to closely correlate with analyte measurements in blood. For example, glucose measurements performed using electrochemical sensors that access skin interstitial fluid have been found to advantageously be highly linearly correlated with blood glucose measurements. Thus, glucose measurements based on skin interstitial fluid are highly representative of blood glucose measurements.

[0069] Furthermore, the shallower microneedle insertion depth of the analyte monitoring device 110 results in a reduced time delay in analyte detection compared to conventional continuous analyte monitoring devices. Such shallower insertion depth positions the sensor surface in close proximity (e.g., within a few hundred micrometers or less) to the dense, well-perfused capillary bed of the reticular dermis, resulting in negligible diffusion lag from the capillaries to the sensor surface. The diffusion time is t=x 2The diffusion delay is related to the diffusion distance according to τ / (2D), where t is the diffusion time, x is the diffusion distance, and D is the mass diffusivity of the analyte of interest. Thus, positioning the analyte sensing element twice as far from the analyte source in the capillary increases the diffusion delay time by four times. Thus, conventional analyte sensors (located in the poorly vascularized adipose tissue below the dermis) experience significantly longer diffusion distances from the vasculature in the dermis, resulting in substantial diffusion latencies (e.g., typically 5-20 minutes). In contrast, the shallower microneedle insertion depth of the analyte monitoring device 110 benefits from low diffusion latencies from the capillaries to the sensor, thereby reducing the time delay in analyte detection and providing more accurate results in real time or near real time. For example, in some variations, the diffusion latency may be less than 10 minutes, less than 5 minutes, or less than 3 minutes.

[0070] Furthermore, when the microneedle array is in the upper skin region, the lower dermis below the microneedle array contains very high levels of vascularization and perfusion to support dermal metabolism, which allows for thermoregulation (via vasoconstriction and / or vasodilation) and provides a barrier function that helps stabilize the sensing environment around the microneedles. Yet another advantage of a shallower insertion depth is that the upper dermal layers lack pain receptors, thereby reducing the sensation of pain when the microneedle array pierces the user's skin, providing a more comfortable and less invasive user experience.

[0071] Thus, the analyte monitoring devices and methods described herein enable improved continuous monitoring of one or more target analytes in a user. For example, as described above, the analyte monitoring devices can be simple and easy to apply, thereby improving ease of use and user compliance. Furthermore, analyte measurement in skin interstitial fluid can provide highly accurate analyte detection. Furthermore, compared to conventional continuous analyte monitoring devices, insertion of the microneedle array and its sensors can be less invasive and less painful for the user. Additional advantages of other aspects of the analyte monitoring devices and methods are further described below.

[0072] As described above, the analyte monitoring device may include a housing. The housing may at least partially enclose or surround other components (e.g., electronic components) of the analyte monitoring device, such as for protection of such components. For example, the housing may be configured to help prevent dust and moisture from entering the analyte monitoring device. In some variations, an adhesive layer may attach the housing to a surface (e.g., skin) of a user while allowing the microneedle array to extend outward from the housing into the user's skin. Furthermore, in some variations, the housing may generally include rounded edges or corners and / or may be low-profile so as to be atraumatic and reduce interference with clothing worn by the user, etc.

[0073] Figures 3A-3D illustrate an embodiment of analyte monitoring device 110. Figures 3A-3D show a top perspective view, a side view, a bottom view, and an exploded view of analyte monitoring device 110, respectively.

[0074] The analyte monitoring device 110 may include a housing defining a cavity that at least partially surrounds or encloses other components (e.g., electronic components) of the analyte monitoring device 110, such as to protect such components. For example, the housing may be configured to help prevent dust and moisture from entering the analyte monitoring device 110. In some variations, an adhesive layer may be provided at the distal end of the housing for attaching the housing to a surface (e.g., skin) of a user. In some variations, after the housing is attached to a surface, the microneedle array 140 may be deployed to extend outward from the housing and into the user's skin. Furthermore, in some variations, the housing may generally include rounded edges or corners and / or may have a low profile to reduce interference with clothing worn by the user, etc.

[0075] 3A-3D, an exemplary variation of analyte monitoring device 110 may include a housing cover 320 and a base plate 330 configured to at least partially enclose the internal components of analyte monitoring device 110. For example, housing cover 320 and base plate 330 may provide an enclosure for a sensor assembly 350 including a microneedle array 140 and electronic components. When deployed, microneedle array 140 extends outward from a portion of base plate 330 in a skin-facing direction (e.g., the underside) of analyte monitoring device 110.

[0076] The housing cover 320 and the base plate 330 may include one or more rigid or semi-rigid protective shell components that can be coupled to one another via, for example, suitable fasteners (e.g., mechanical fasteners), mechanical interlocking or mating features, and / or engineered interlocks. The housing cover 320 and the base plate 330 may include rounded edges and corners and / or other atraumatic features. When coupled to one another, the housing cover 320 and the base plate 330 may form a cavity that includes an internal volume that houses internal components, such as the sensor assembly 350. For example, the internal components disposed within the internal volume may be arranged in a compact, low-profile stack as the sensor assembly 350.

[0077] Analyte monitoring device 110 may include one or more adhesive layers provided at the distal end of the housing for attaching analyte monitoring device 110 (e.g., housing cover 320 and base plate 330 coupled together) to a surface (e.g., skin) of a user. As shown in FIG. 3D , the one or more adhesive layers may include inner adhesive layer 342 and outer adhesive layer 344. Inner adhesive layer 342 may adhere to base plate 330, and outer adhesive layer 344 may adhere to inner adhesive layer 342 and provide adhesive on its outward-facing side for (e.g., temporary) adhesion to the user's skin. Inner adhesive layer 342 and outer adhesive layer 344 together function as a double-sided adhesive for adhering analyte monitoring device 110 to the user's skin. Outer adhesive layer 344 may be protected by a release liner that the user removes to expose the adhesive prior to application to the skin. In some variations, a single adhesive layer is provided. In some variations, the outer adhesive layer 344, the inner adhesive layer 342, and / or the single adhesive layer may have an outer periphery that extends farther than the outer periphery or perimeter of the housing cover 320 and the base plate 330. This may increase the surface area for attachment and increase the stability of retention or attachment to the user's skin. The inner adhesive layer 342, the outer adhesive layer 344, and / or the single adhesive layer may each have an opening that allows the outwardly extending microneedle array 140 to pass through when deployed, as described further below. The openings in the inner adhesive layer 342 and the outer adhesive layer 344 may generally be aligned with one another, but in some variations, they may be different sizes, with one opening being smaller than the other. In some variations, the openings are substantially the same size.

[0078] Base plate 330 has a first surface (e.g., an outer exposed surface) opposite a second surface and functions as a support and / or connecting structure as well as a protective cover for sensor assembly 350. Base plate 330 is sized and shaped to attach to housing cover 320. Base plate 330 may be shaped to fit securely within housing cover 320 such that outer edges of base plate 330 align with corresponding edges of the opening in housing cover 320. This alignment may be such that there is no gap between the outer edges of base plate 330 and the corresponding edges of the opening in housing cover 320.

[0079] A connecting member 332 may be formed in a central or near-central region of the first surface of the base plate 330. The connecting member 332 is a protrusion (e.g., a protruding hub) having a sidewall extending from the first surface of the base plate 330 and a first surface substantially parallel to the first surface of the base plate 330. The sidewall extends from an edge of the first surface of the connecting member 332 to the first surface of the base plate 330. The remainder of the first surface of the base plate 330 surrounding the connecting member 332 may be flat or substantially flat. One or more connector features 336 extend outward from the sidewall of the connecting member 332 to releasably engage with a corresponding connector of, for example, a microneedle enclosure that provides a sterile environment for the microneedle array 140. The first surface and sidewall of the connecting member 332 partially define a chamber. The chamber may be further defined by a portion of the base plate 330 adjacent to (e.g., below) the connecting member 332. The chamber is accessible through an opening on the second surface of the base plate 330. An aperture or distal opening 334 is formed through the first surface of the connecting member 332. The distal opening 334 can be sized and shaped such that the microneedle array 140 fits securely within and extends through the distal opening 334 when in the deployed configuration. For example, the sidewalls of the microneedle array 140 can align with the corresponding sidewalls of the distal opening 334. In some variations, the distal opening 334 can be sized and shaped to correspond to the area surrounding the microneedle array 140. The openings in the inner adhesive layer 342 and the outer adhesive layer 344 (or a single adhesive layer) can be sized such that the connecting member 332 extends through the openings without interfering with the adhesive layers. For example, the diameter of the opening in the inner adhesive layer 342 and the diameter of the opening in the outer adhesive layer 344 are larger than those of the connecting member 332. In some variations, the opening in the inner adhesive layer 342 and / or the opening in the outer adhesive layer 344 (or the opening in a single adhesive layer) is adjacent to the side wall of the connecting member 332 with clearance to accommodate one or more connector features 336.In some variations, one or more slits or notches may be formed in the inner adhesive layer 342, the outer adhesive layer 344, and / or the single adhesive layer, extending from the opening to aid in the placement of the respective adhesive layers.

[0080] Although the housing cover 320 and base plate 330 shown in FIGS. 3A-3D are substantially circular, with the housing cover 320 having a dome shape, in other variations, the housing cover 320 and base plate 330 may have any suitable shape. For example, in other variations, the housing cover 320 and base plate 330 may be generally prismatic, elliptical, triangular, rectangular, pentagonal, hexagonal, or other suitable shapes. The outer adhesive layer 344 (or single adhesive layer) may extend outward from the housing cover 320 and base plate 330 and extend beyond the outer periphery of the housing cover 320. The outer adhesive layer 344 (or single adhesive layer) may be circular, as shown in FIGS. 3A-3D, or may have an elliptical, triangular, rectangular, pentagonal, hexagonal, or other suitable shape, and need not be the same shape as the housing cover 320 and / or base plate 330.

[0081] 4A-4E show an embodiment of a sensor assembly 350 of an analyte monitoring device 110 in an exploded perspective view, an exploded side view, a bottom perspective view, a side view, and a top perspective view, respectively.

[0082] The sensor assembly 350 includes microneedle array components and electronics for implementing the analyte detection and processing aspects of the microneedle array-based continuous analyte monitoring device 110 for analyte detection and measurement. In some variations, the sensor assembly 350 is a compact, low-profile laminate at least partially housed within a cavity that includes an interior volume defined by the housing cover 320 and the base plate 330.

[0083] In some variations, the sensor assembly 350 includes a microneedle array assembly 360 and an electronics assembly 370 that connect to each other to implement the microneedle array analyte detection and processing aspects described further herein. In some variations, the electronics assembly 370 includes a main printed circuit board (PCB) 450 to which the electronic components are connected, and the microneedle array assembly 360 includes a secondary printed circuit board (PCB) 420 to which the microneedle array 140 is connected.

[0084] In some variations, the microneedle array assembly 360 includes, in addition to the secondary PCB 420 and the microneedle array 140, an epoxy skirt 410 and a secondary PCB connector 430. The microneedle array 140 is coupled to the top side (e.g., the outward-facing side) of the secondary PCB 420 so that the individual microneedles of the microneedle array 140 are exposed, as described with reference to Figures 3A-3D. The secondary PCB connector 430 is coupled to the back side, opposite the top side, of the secondary PCB 420. The secondary PCB connector 430 may be an electromechanical connector and may be communicatively coupled to the primary PCB 450 via a primary PCB connector 470 on the top side (e.g., the outward-facing side) of the primary PCB 450 to enable signal communication between the secondary PCB 420 and the primary PCB 450. For example, signals from the microneedle array 140 can be communicated to the primary PCB 450 via the secondary PCB 420, the secondary PCB connector 430, and the primary PCB connector 470.

[0085] The secondary PCB 420 may, in part, determine the distance that the microneedle array 140 protrudes from the housing's base plate 330. Thus, the height of the secondary PCB 420 may be selected to help ensure that the microneedle array 140 is properly inserted into the user's skin. During microneedle insertion, the first surface (e.g., the outward-facing surface) of the connecting member 332 of the base plate 330 may act as a stop for microneedle insertion. If the secondary PCB 420 has a low height and its top surface is flush or nearly flush with the first surface of the connecting member 332, the connecting member 332 may prevent the microneedle array 140 from being fully inserted into the skin.

[0086] In some variations, other components (e.g., electronic components such as sensors or other components) may also be connected to secondary PCB 420. For example, secondary PCB 420 may be sized and shaped to accommodate electronic components on the top or back side of secondary PCB 420.

[0087] 3C and 3D , the epoxy skirt 410 may be deposited along the edge (e.g., periphery) of the microneedle array 140 to provide a secure fit of the microneedle array 140 within the distal opening 334 formed in the connecting member 332 of the base plate 330 and / or to soften sharp edges along the microneedle array 140. For example, the epoxy skirt 410 may occupy the portion of the distal opening 334 not filled by the microneedle array 140 and / or the portion of the chamber defined in the base plate 330 not filled by the secondary PCB 420. The epoxy skirt 410 may also provide a transition from the edge of the microneedle array 140 to the edge of the secondary PCB 420. In some variations, the epoxy skirt 410 may be replaced or supplemented by a gasket (e.g., a rubber gasket) or the like.

[0088] Electronics assembly 370 with primary PCB 450 includes battery 460 coupled to the back side of primary PCB 450, opposite the top side to which primary PCB connector 470 is coupled. In some variations, battery 460 may be coupled to the top side of primary PCB 450 and / or in other arrangements.

[0089] Figures 4F-4H show an embodiment of an alternative variation of sensor assembly 350 of analyte monitoring device 110. Perspective exploded, side exploded, and side views of sensor assembly 350 are provided in Figures 4F-4H, respectively.

[0090] As shown, the sensor assembly 350 incorporates an additional PCB component, the intermediate PCB 425. In some variations, the intermediate PCB 425 is part of the microneedle array assembly 360 and is positioned between and connected to the secondary PCB 420 and the microneedle array 140. The intermediate PCB 425 may be added to increase the height of the microneedle array assembly 360, thereby extending the microneedle array 140 a greater distance from the base plate 330, which may aid in insertion of the microneedle array 140 into a user's skin. The microneedle array 140 is coupled to the top side (e.g., the outward-facing side) of the intermediate PCB 425 such that the individual microneedles of the microneedle array 140 are exposed, as described with reference to FIGS. 3A-3D . The secondary PCB 420 is bonded to the back side, opposite the top side, of the intermediate PCB 425, and the secondary PCB connector 430 is bonded to the back side, opposite the top side, of the secondary PCB 420. An epoxy skirt 410 (which may be replaced or supplemented by an equivalent gasket) provides a transition from the edge of the microneedle array 140 to the edge of the intermediate PCB 425.

[0091] The intermediate PCB 425 with the secondary PCB 420 determines, in part, the distance that the microneedle array 140 protrudes through the distal opening 334 of the base plate 330. The incorporation of the intermediate PCB 425 provides additional height that helps ensure that the microneedle array 140 is properly inserted into the user's skin. In some variations, the upper side (e.g., the outward-facing side) of the intermediate PCB 425 extends out through the distal opening 334, such that the first surface (e.g., the exposed top surface) of the connecting member 332 surrounding the distal opening 334 does not prevent the microneedle array from being fully inserted into the skin. In some variations, the upper side (e.g., the outward-facing side) of the intermediate PCB 425 does not extend out of the distal opening 334, but the increased height (by incorporating the intermediate PCB 425) ensures that the microneedle array 140 protrudes a sufficient distance from the base plate 330 of the housing.

[0092] In some variations, a microneedle enclosure may be provided for releasable attachment to the analyte monitoring device 110. The microneedle enclosure may provide a protective environment or enclosure in which the microneedle array 140 may be safely contained, thereby ensuring the integrity of the microneedle array 140 during certain stages of manufacturing and shipping of the analyte monitoring device 110 prior to application of the analyte monitoring device 110. The microneedle enclosure may be releasable or removable from the analyte monitoring device 110 so that the microneedle array 140 is exposed and / or ready for insertion into a user's skin, as described further herein.

[0093] In some variations, the microneedle enclosure provides an enclosed, sealed environment in which the microneedle array 140 can be contained, thereby providing an environment in which the microneedle array 140 can be sterilized. For example, the microneedle enclosure with the microneedle array 140 can be subjected to a sterilization process in which the sterilization penetrates the microneedle enclosure so that the microneedle array 140 is also sterilized. Because the microneedle array 140 is contained within an enclosed environment, the microneedle array 140 remains sterile until removed from the enclosed environment. In some variations, a removable film is provided at the distal end of the housing to cover the distal opening 334 prior to application of the analyte monitoring device 110 to a subject's skin surface. The removable film can maintain a sterile environment and prevent the entry of foreign objects or extraneous substances prior to application of the analyte monitoring device 110. A user can remove or peel off the film immediately prior to applying and / or adhering the analyte monitoring device 110 to a subject's skin surface. Microneedle structure

[0094] As shown in the schematic diagram of FIG. 5A, in some variations, a microneedle array 510 for use in sensing one or more analytes may include one or more microneedles 510 protruding from a substrate surface 502. The substrate surface 502 may be, for example, substantially flat, and the one or more microneedles 510 may protrude orthogonally from the flat surface. Generally, as shown in FIG. 5B, the microneedle 510 may include a body portion 512 (e.g., a shaft) and a tapered distal portion 514 configured to pierce a user's skin. In some variations, the tapered distal portion 514 may terminate in an insulated distal tip 516. The microneedle 510 may further include an electrode 520 on the surface of the tapered distal portion. In some variations, electrode-based measurements may be performed at the interface between an electrode placed inside the body and interstitial fluid (e.g., on the outer surface of the entire microneedle). In some variations, the microneedle 510 may have a solid core (e.g., a solid body portion), while in some variations, the microneedle 510 may include one or more lumens that may be used, for example, for drug delivery or sampling of skin interstitial fluid. Other microneedle variations, as described below, may similarly include either a solid core or one or more lumens.

[0095] The microneedle array 500 may be formed at least in part from a semiconductor (e.g., silicon) substrate and include various layers of material applied and shaped using various suitable microelectromechanical systems (MEMS) fabrication techniques (e.g., deposition and etching techniques), as described further below. The microneedle array may be reflow soldered to a circuit board, similar to a typical integrated circuit. Furthermore, in some variations, the microneedle array 500 may include a three-electrode configuration including a working (sensing) electrode having an electrochemical sensing coating (including a biorecognition element such as an enzyme) that enables detection of a target analyte, a reference electrode, and a counter electrode. In other words, the microneedle array 500 may include at least one microneedle 510 including a working electrode, at least one microneedle 510 including a reference electrode, and at least one microneedle 510 including a counter electrode. Further details of these types of electrodes are described in more detail below.

[0096] In some variations, the microneedle array 500 may include multiple microneedles that are insulated such that the electrodes on each microneedle in the multiple microneedles are individually addressable and electrically isolated from all other electrodes on the microneedle array. The resulting individual addressability of the microneedle array 500 may allow greater control over the function of each electrode, since each electrode can be probed separately. For example, the microneedle array 500 may be used to provide multiple independent measurements of a given target analyte, thereby improving the sensing reliability and accuracy of the device. Furthermore, in some variations, the electrodes of multiple microneedles may be electrically connected to generate enhanced signal levels. As another example, the same microneedle array 500 may additionally or alternatively be interrogated to simultaneously measure multiple analytes to provide a more comprehensive assessment of a physiological condition. For example, as shown in the schematic diagram of FIG. 6, the microneedle array may include a portion of microneedles for detecting a first analyte A, a second portion of microneedles for detecting a second analyte B, and a third portion of microneedles for detecting a third analyte C. It should be understood that the microneedle array can be configured to detect any suitable number of analytes (e.g., 1, 2, 3, 4, 5, or more, etc.). Suitable target analytes for detection may include, for example, glucose, ketones, lactate, and cortisol. For example, in some variations, ketones can be detected in a manner similar to that described in U.S. Patent Application No. 16 / 701,784, which is incorporated herein by reference in its entirety. Thus, the individual electrical addressability of the microneedle array 500 provides greater control and flexibility over the sensing function of the analyte monitoring device.

[0097] In some variations of microneedles (e.g., microneedles having a working electrode), the electrode 520 may be positioned proximal to the insulated distal apex 516 of the microneedle. In other words, in some variations, the electrode 520 does not cover the apex of the microneedle. Rather, the electrode 520 may be offset from the apex or tip of the microneedle. The electrode 520 being proximal to or offset from the insulated distal apex 516 of the microneedle advantageously provides more accurate sensor measurements. For example, this arrangement prevents electric field concentration at the microneedle apex 516 during manufacturing, thereby avoiding uneven deposition of sensing chemistry on the electrode surface 520, which could result in erroneous sensing. In some variations, the electrode 520 may be configured to have an annular shape and may include a distal edge 521 a and a proximal edge 521 b.

[0098] As another example, positioning the electrode 520 offset from the microneedle apex further improves sensing accuracy by reducing undesirable signal artifacts and / or erroneous sensor readings caused by stresses during microneedle insertion. The distal apex of the microneedle is the first area to penetrate the skin and, therefore, experiences the greatest stresses caused by mechanical shear phenomena associated with tearing or cutting the skin. If the electrode 520 were positioned at the apex or tip of the microneedle, this mechanical stress could peel off the electrochemical sensing coating on the electrode surface when the microneedle is inserted and / or cause a small but interfering amount of tissue to be transported onto the active sensing portion of the electrode. Therefore, positioning the electrode 520 sufficiently offset from the microneedle apex can improve sensing accuracy. For example, in some variations, the distal edge 521a of the electrode 520 may be positioned at least about 10 μm (e.g., about 20 μm to about 30 μm) from the distal apex or tip of the microneedle, as measured along the longitudinal axis of the microneedle.

[0099] The body portion 512 of the microneedle 510 may further include a conductive path extending between the electrode 520 and a back electrode or other electrical contact (e.g., disposed on the back surface of the microneedle array substrate). The back electrode may be soldered to a circuit board and may be in electrical communication with the electrode 520 via the conductive path. For example, during use, the in vivo sensed current measured at the working electrode (inside the dermis) is interrogated by the back electrical contact, and the electrical connection between the back electrical contact and the working electrode is facilitated by the conductive path. In some variations, this conductive path may be facilitated by a metal via running through the interior of the microneedle body portion (e.g., shaft) between the proximal and distal ends of the microneedle. Alternatively, in some variations, the conductive path may be provided by the entire body portion formed from a conductive material (e.g., doped silicon). In some of these variations, the entire substrate on which the microneedle array 500 is constructed may be conductive, and each microneedle 510 of the microneedle array 500 may be electrically isolated from adjacent microneedles 510, as described below. For example, in some variations, each microneedle 510 in the microneedle array 500 may be electrically isolated from adjacent microneedles 510 using an insulating barrier comprising an electrically insulating material (e.g., a dielectric material such as silicon dioxide) surrounding the conductive pathway extending between the electrode 520 and the backside electrical contact. For example, the body portion 512 may include an insulating material that forms a sheath around the conductive pathway, thereby preventing electrical communication between the conductive pathway and the substrate. Other exemplary variations in structures that provide electrical isolation between microneedles are described in further detail below.

[0100] Such electrical isolation between microneedles within a microneedle array allows the sensors to be individually addressable. This individual addressability advantageously allows for independent, parallelized measurements between sensors, as well as dynamic reconfiguration of sensor assignments (e.g., for different analytes). In some variations, the electrodes of the microneedle array can be configured to provide redundant analyte measurements, which is an advantage over conventional analyte monitoring devices. For example, redundancy can improve performance by improving accuracy (e.g., averaging multiple analyte measurements for the same analyte to reduce the impact of extremely high or low sensor signals on analyte level determinations) and / or can improve device reliability by reducing the likelihood of overall failure.

[0101] In some variations, as described in further detail below with each different variation of microneedles, the microneedle array may be formed at least in part by suitable semiconductor and / or MEMS fabrication techniques and / or mechanical cutting or dicing. Such processes may be advantageous, for example, to enable large-scale, cost-effective manufacture of microneedle arrays. For example, in some variations, the microneedle array may be formed at least in part using the techniques described in U.S. Patent Application No. 15 / 913,709, which is incorporated herein by reference in its entirety.

[0102] Described herein are several exemplary variations of microneedle structures that incorporate one or more of the microneedle features described above for microneedle arrays in analyte monitoring devices.

[0103] In some variations, the microneedle may have a generally cylindrical body portion and a tapered distal portion having an electrode. For example, Figures 7A-7C show exemplary variations of a microneedle 700 extending from a substrate 702. Figure 7A is a schematic side cross-sectional view of the microneedle 700, Figure 7B is a perspective view of the microneedle 700, and Figure 7C is a detailed perspective view of the distal portion of the microneedle 700. As shown in Figures 7B and 7C, the microneedle 700 may include a cylindrical body portion 712, a tapered distal portion 714 terminating in an insulated distal apex 716, and an annular electrode 720 comprising a conductive material (e.g., Pt, Ir, Au, Ti, Cr, Ni, combinations thereof, etc.) and disposed on the tapered distal portion 714, e.g., on a segment thereof, the annular electrode 720 having a distal edge 721 a and a proximal edge 721 b. 7A, the ring electrode 720 may be proximal to (or offset from or spaced apart from) the distal apex 716. The electrode 720 may be electrically insulated from the distal apex 716 by a distal insulating surface 715a comprising an insulating material (e.g., SiO2). For example, the distal edge 721a of the ring electrode 720 may be adjacent to the proximal edge of the distal insulating surface 715a of the insulated distal apex 716. In some variations, the distal edge 721 a of the ring electrode 720 may be proximal (e.g., immediately proximal, adjacent, abutting) the proximal edge of the distal apices 716 (the proximal edge of the distal insulating surface 715 a), while in other variations, the distal edge 721 a of the ring electrode 720 may be distal (e.g., immediately distal, adjacent) to the proximal edge of the insulated distal apices 716 (the proximal edge of the distal insulating surface 715 a), but remain proximal to the apices themselves. Thus, in some variations, the electrode 720 may overlie a portion of the distal insulating surface 715 a, but remain proximal to (and may be offset from) the insulated distal apices themselves (see, e.g., FIG. 21C ).

[0104] 7A, the proximal edge 721b of the electrode 720 may be distal to the cylindrical body portion 712, or in some variations, may be offset or spaced therefrom. In some variations, the proximal edge 721b of the electrode 720 may be electrically insulated from the cylindrical body portion 712 by the second distal insulating surface 715b. For example, the proximal edge 721b of the ring electrode 720 may be proximate the distal edge of the second distal insulating surface 715b. In some variations, the proximal edge 721 b of the electrode 720 may be proximal (e.g., immediately proximal, adjacent, abutting) the distal edge of the second distal insulating surface 715 b, while in other variations, the proximal edge 721 b of the electrode 720 may be distal (e.g., immediately distal, adjacent) to the distal edge of the second distal insulating surface 715 b but remain proximal to the cylindrical body portion 712. Thus, in some variations, the electrode 720 may overlie a portion of the second distal insulating surface 715 b but remain proximal to (and offset from) the cylindrical body portion 712. As shown in FIG. 7A and in some other variations, the annular electrode 720 may be on only a portion of the surface of the tapered distal portion 714 and may or may not extend all the way to the cylindrical body portion 712.

[0105] The electrode 720 may be in electrical communication with a conductive core 740 (e.g., a conductive pathway) that passes along the body portion 712 to a backside electrical contact 730 (e.g., made from a Ti / Au alloy or a Ni / Au alloy) or other electrical pad in or on the substrate 702. For example, the body portion 712 may include a conductive core material (e.g., heavily doped silicon). As shown in FIG. 7A , in some variations, an insulating moat 713 including an insulating material (e.g., poly-Si / SiO or SiO) may be disposed around (e.g., around the periphery) the body portion 712 and extend at least partially through the substrate 702. The insulating moat 713 may thus help, for example, to prevent electrical contact between the conductive core 740 and the surrounding substrate 702. The insulating moat 713 may also extend further onto the surface of the body portion 712. The top and / or bottom surfaces of the substrate 702 may also include a substrate insulating layer 704 (e.g., SiO). Thus, the insulation provided by the insulating moat 713 and / or substrate insulator 704 may at least partially contribute to the electrical insulation of the microneedles 700, enabling addressability of the microneedles 700 within a microneedle array. Additionally, in some variations, the insulating moat 713 extending over the surface of the body portion 712 may function to increase the mechanical strength of the microneedle 700 structure.

[0106] The microneedle 700 can be formed, at least in part, by suitable MEMS fabrication techniques, such as plasma etching, also known as dry etching. For example, in some variations, the insulating moat 713 around the body portion 712 of the microneedle may be fabricated by first forming a trench in a silicon substrate by deep reactive ion etching (DRIE) from the backside of the substrate, and then filling the trench with a SiO2 / polycrystalline silicon (poly-Si) / SiO2 sandwich by low-pressure chemical vapor deposition (LPCVD) or other suitable process. In other words, the insulating moat 713 passivates the surface of the body portion 712 of the microneedle and can continue as a recessed feature in the substrate 702 near the proximal portion of the microneedle. By comprising a primarily silicon compound, the insulating moat 713 can provide good filling and adhesion to adjacent silicon walls (e.g., conductive core 740, substrate 702, etc.). The sandwich structure of insulating moat 713 can further help provide an excellent coefficient of thermal expansion (CTE) match with the adjacent silicon, thereby advantageously reducing failure, cracking, and / or other thermally induced weaknesses of insulating structure 713.

[0107] The tapered distal portion can be formed by isotropic dry etching from the front side of the substrate, and the body portion 712 of the microneedle 700 can be formed by DRIE. A front metal electrode 720 can be deposited and patterned on the distal portion by specialized lithography (e.g., electron beam evaporation and / or lift-off) that allows metal deposition on the desired annular region of the electrode 720 without coating the distal tip 716. Additionally, a backside electrical contact 730, for example of Ti / Au or Ni / Au, can be deposited by a suitable MEMS fabrication technique (e.g., sputtering).

[0108] The microneedle 700 may have any suitable dimensions. By way of example, in some variations, the microneedle 700 may have a height of about 300 μm to about 500 μm. In some variations, the tapered distal portion 714 may have a tip angle of about 60 degrees to about 80 degrees and a top diameter of about 1 μm to about 15 μm. In some variations, the surface area of ​​the ring electrode 720 may be about 9,000 μm. 2 ~approx. 11,000μm 2 , or approximately 10,000 μm 2 FIG. 8 illustrates various dimensions of an exemplary variation of a cylindrical microneedle having a tapered distal portion and a ring electrode, similar to the microneedle 700 described above. The cylindrical microneedle of FIG. 8, like the microneedle 700 described above, comprises a cylindrical body portion, a tapered distal portion terminating in an insulated distal apex, a contact trench formed in the tapered distal portion, and a ring electrode (labeled "electrode" in FIG. 8) disposed on the tapered distal portion and covering the contact trench. The ring electrode can comprise a conductive material (e.g., Pt, Ir, Au, Ti, Cr, Ni, combinations thereof, etc.). In some variations, the contact trench may have a width of about 1 μm, about 2 μm, about 3 μm, about 4 μm, about 5 μm, about 10 μm, about 15 μm, about 20 μm, about 25 μm, about 30 μm, about 35 μm, about 40 μm, about 45 μm, about 50 μm, or about 20 μm as shown in Figure 8. The ring electrode may include a distal edge and a proximal edge, and in some variations, the distance between the distal and proximal edges of the ring electrode may be about 20 μm, about 30 μm, about 40 μm, about 50 μm, about 60 μm, about 70 μm, about 80 μm, about 90 μm, about 100 μm, or about 60 μm as shown in Figure 8. In some variations, the annular electrode may overlie a portion of the insulating surface of the contact trench, the tapered distal portion (labeled "oxide" in FIG. 8), as shown in FIG. 8 by the line extending from "electrode."

[0109] 9A-9F show another exemplary variation of a microneedle 900 having a generally cylindrical body portion. The microneedle 900 may be similar to the microneedle 700 described above, except as described below. For example, like the microneedle 700, the microneedle 900 of FIG. 9A extends from a substrate 902. The top surface of the substrate 902 may include a substrate insulating layer 904. As shown in FIG. 9B, like the microneedle 700, the microneedle 900 may include a cylindrical body portion 912 and a tapered distal portion 914 that terminates in an insulated distal apex 916. The microneedle 900 may further include a ring-shaped electrode 920 comprising a conductive material and disposed on the tapered distal portion 914 at a location proximal to (or offset or spaced from) the distal apex 916. The electrode 920 may be in electrical communication with a conductive core 940 that passes along the body portion 912 to a backside electrical contact 930. Other elements of the microneedle 900 are numbered similarly to corresponding elements of the microneedle 700.

[0110] However, compared to microneedle 700, microneedle 900 may have a sharper tip at distal apex 916 and a modified insulating moat 913. For example, distal apex 916 may have a sharper tip angle, such as about 25 degrees to about 45 degrees, and an apex radius of less than about 100 nm, which provides a sharper microneedle profile that can penetrate skin more easily, at a lower speed, with less energy, and / or with less trauma. Furthermore, in contrast to insulating moat 713 (which extends through substrate 702 along the height of microneedle body portion 712, as shown in FIG. 7A), in some variations, modified insulating moat 913 may extend only through substrate 902, such that the sandwich structure filling the trench (e.g., created by DRIE as described above) forms only a buried feature within the substrate. Although the sidewalls of the microneedle 900 are shown in FIG. 9 as extending approximately perpendicular to the substrate surface, it should be understood that in variations in which the modified insulating moat does not extend the entire height of the microneedle body portion 912, the sidewalls of the microneedle 900 may be sloped at a non-orthogonal angle to the substrate (e.g., the sidewalls may have a slight positive taper of between about 1 degree and about 10 degrees, or between about 5 degrees and about 10 degrees).

[0111] In some variations, the remainder of the microneedle surface 900 (other than the annular electrode 920) may include insulating material extending from the substrate insulator 904. For example, a layer of insulating material (e.g., SiO) may extend from the front surface of the substrate 902 to provide body portion insulation and may further extend over the proximal edge of the electrode 920, as shown, for example, in FIG. 9C . Another region of insulating material may similarly cover the distal edge of the electrode 920, insulating the distal tip 916. Such region of insulating material and / or modified insulating moat 913 may help prevent electrical contact between the conductive core 940 and the surrounding substrate 902. Thus, similar to the microneedle 700, the microneedle 900 can maintain electrical isolation for addressability within a microneedle array. In some variations, the process of forming the microneedle 900 may result in higher yields and / or offer lower manufacturing costs compared to the process of forming the microneedle 700.

[0112] The microneedle 900 can have any suitable dimensions. By way of example, the microneedle 900 can include a height of about 400 μm to about 600 μm, or about 500 μm, in some variations. In some variations, the tapered distal portion 914 can have a tip angle of about 25 degrees to about 45 degrees, with a tip radius of less than about 100 nm. Additionally, the microneedle can have a shaft diameter of about 160 μm to about 200 μm.

[0113] In some variations, the electrode 920 may be electrically insulated from the distal tip 916 by a distal insulating surface 915a comprising an insulating material (e.g., SiO2). In some variations, the proximal edge of the electrode 920 may be electrically insulated from the post-shaped body portion 912 by a second distal insulating surface 915b. Other elements of the microneedle 900 shown in Figures 9A-9F are numbered similarly to corresponding elements of the microneedle 700.

[0114] 9B, 9C, and 9F, the tapered distal portion 914, and more specifically, the electrode 920 on the tapered distal portion 914 of the microneedle 900, may include a tip contact trench 922. This contact trench may be configured to establish ohmic contact between the electrode 920 and the underlying conductive core 940 of the microneedle. In some variations, the shape of the tip contact trench 922 may include an annular recess formed in the surface of the tapered distal portion 914. In some variations, the shape of the tip contact trench 922 may include an annular recess formed in the surface of the conductive core 940 (e.g., in contact with a conductive path within or otherwise in the body portion of the microneedle). In some variations, the tip contact trench may be formed in an insulating material on the tapered distal portion 914 and may have a depth approximately equal to the thickness of the insulating material. In some examples, the depth of the contact trench may be greater than the thickness of the insulating material such that the contact trench extends beyond the surface of the conductive core 940 (i.e., into the conductive core 940). The electrode 920 may overlie the tip contact trench 922 such that an ohmic contact is established between the electrode 920 and the conductive core 940. In some variations, the electrode 920 may extend beyond the tip contact trench 922 such that when the material of the electrode 920 is deposited on the conductive core 940, the electrode 920 with the tip contact trench 922 can have a stepped profile in side view. The tip contact trench 922 may advantageously help to provide a tolerance for ensuring contact between the electrode 920 and the underlying conductive core 940. Any of the other microneedle variations described herein may have a similar tip contact trench to help ensure contact between the electrode (which may be, for example, a working electrode, a reference electrode, a counter electrode, etc.) and the conductive pathway within the microneedle.

[0115] 10A and 10B show further various dimensions of exemplary variations of a cylindrical microneedle having a tapered distal portion and a ring electrode. For example, the microneedle variations shown in FIGS. 10A and 10B can have a tapered distal portion having a taper angle of generally about 80 degrees (or about 78 degrees to about 82 degrees, or about 75 degrees to about 85 degrees) and a cone diameter of about 140 μm (or about 133 μm to about 147 μm, or about 130 μm to about 150 μm). The cone of the tapered distal portion may be positioned on the cylinder such that the combined height of the cone and cylinder is about 110 μm (or about 99 μm to about 116 μm, or about 95 μm to about 120 μm). The ring electrode on the tapered distal portion can have an outer or base diameter of about 106 μm (or about 95 μm to about 117 μm, or about 90 μm to about 120 μm) and an inner diameter of about 33.2 μm (or about 30 μm to about 36 μm, or about 25 μm to about 40 μm). The length of the ring electrode measured along the slope of the tapered distal portion can be about 57 μm (or between about 55 μm and about 65 μm), and the total surface area of ​​the electrode can be about 12,700 μm. 2 (or approximately 12,500 μm 2 ~Approx. 12,900μm 2 Between or about 12,000 μm 2 ~Approx. 13,000μm 2 As shown in FIG. 10B, the electrode can further have a tip contact trench extending around the conical central region of the tapered distal portion, the contact having a width of about 11 μm (or about 5 μm to about 50 μm, about 10 μm to about 12 μm, or about 8 μm to about 14 μm) as measured along the slope of the tapered distal portion, and a trench depth of about 1.5 μm (or about 0.1 μm to about 5 μm, or about 0.5 μm to about 1.5 μm, or about 1.4 μm to about 1.6 μm, or about 1 μm to about 2 μm). The microneedle has an insulated distal tip with a diameter of about 5.5 μm (or about 5.3 μm to about 5.8 μm, or about 5 μm to about 6 μm).

[0116] Further details of exemplary variations of microneedle array configurations are described in more detail below. electrode

[0117] As described above, each microneedle in a microneedle array may include an electrode. In some variations, multiple different types of electrodes may be included among the microneedles of the microneedle array. For example, in some variations, the microneedle array may function as an electrochemical cell capable of electrolytic operation using three types of electrodes. In other words, the microneedle array may include at least one working electrode, at least one counter electrode, and at least one reference electrode. Thus, the microneedle array may include three different electrode types, but one or more of each electrode type may form a complete system (e.g., the system may include multiple separate working electrodes). Furthermore, multiple separate microneedles may be electrically joined to form an effective electrode type (e.g., a single working electrode may be formed from two or more connected microneedles having working electrode sites). Each of these electrode types may include a metallization layer and one or more coatings or layers or other components on the metallization layer that help facilitate the function of the particular electrode.

[0118] Generally, the working electrode is the electrode where the oxidation and / or reduction reaction of interest occurs for detection of the analyte of interest. The counter electrode functions to source (source) or sink (store) the electrons necessary to sustain the electrochemical reaction at the working electrode via electrical current. The reference electrode functions to provide a reference potential for the system; that is, the potential to which the working electrode is biased is referenced to the reference electrode. A fixed, time-varying, or at least controlled potential relationship is established between the working and reference electrodes, and, within practical limits, current is not sourced from or sunk to the reference electrode. Furthermore, to implement such a three-electrode system, the analyte monitoring device can include a suitable potentiostat or electrochemical analog front end to maintain a fixed potential relationship between the working and reference electrode contingencies in the electrochemical system (via an electronic feedback mechanism), while dynamically varying the counter electrode to the potential required to sustain the redox reaction of interest.

[0119] As described herein, a working electrode is an electrode at which oxidation and / or reduction reactions of interest occur. In some variations, sensing may be performed at the interface between the working electrode placed in the body and interstitial fluid (e.g., on the outer surface of the entire microneedle). In some variations, the working electrode may include an electrode material and a biorecognition layer in which a biorecognition element (e.g., an enzyme) is immobilized on the working electrode to facilitate selective analyte quantification. In some variations, as described in more detail herein, if the biorecognition layer includes an interferent blocker, the biorecognition layer may also function to help prevent, limit, or otherwise inhibit endogenous and / or exogenous species from directly oxidizing (or reducing) at the electrode. In some variations, the working electrode may also include a diffusion-limiting layer, which is a separate and distinct layer and also functions to minimize direct oxidation (or reduction) of endogenous and / or exogenous species at the electrode. The separate and distinct diffusion-limiting layer may be referred to elsewhere herein as a glucose-limiting layer, or more broadly, an analyte-limiting layer. In some variations, an electrode protection layer may be provided in addition to the biorecognition layer and / or the diffusion-limiting layer for additional protection of the electrode. In some variations where the biorecognition layer and the diffusion-limiting layer are separate and distinct layers, an adhesion enhancer may be provided between and / or within the biorecognition layer and the diffusion-limiting layer to promote bonding between the layers and improve sensor stability and sensitivity. In some variations, an interferent-blocking agent may be provided within the biorecognition layer, separately and / or in addition to the diffusion-limiting layer described above, to prevent, limit, or inhibit additional interferents, such as foreign body response factors, from reaching the electrode surface, such that voids within the biorecognition layer that may penetrate the entire thickness of the biorecognition layer and / or otherwise expose the metallization layer are filled with the interferent-blocking agent.

[0120] The redox current detected at the working electrode can be correlated to the detected concentration of the analyte of interest because, assuming a steady-state diffusion-limited system, the redox current detected at the working electrode obeys the Cottrell relationship:

number

[0121] Furthermore, because the detection current is a direct function of the electrode surface area A, increasing the surface area of ​​the electrode can increase the sensitivity of the sensor (e.g., amperes per mole of analyte). For example, multiple single working electrodes can be grouped into an array of two or more elements to increase the total effective sensing surface area. Additionally or alternatively, for redundancy, multiple working electrodes can be operated as a parallelized sensor to obtain multiple independent measurements of the concentration of the analyte of interest. The working electrode can operate as an anode (so that the analyte is oxidized at its surface) or as a cathode (so that the analyte is reduced at its surface).

[0122] Generally, the counter electrode is the electrode that supplies or sinks the electrons (via current) necessary to sustain the electrochemical reaction at the working electrode. To avoid the current-carrying capacity of the counter electrode limiting the redox reaction at the working electrode, the number of counter electrode components can be increased in the form of a counter electrode array to increase surface area. Therefore, to avoid current-carrying capacity limitations, it may be desirable to have excess counter electrode area relative to the working electrode area. When the working electrode operates as an anode, the counter electrode functions as a cathode, and vice versa. Similarly, when an oxidation reaction occurs at the working electrode, a reduction reaction occurs at the counter electrode, and vice versa. Unlike the working or reference electrode, the counter electrode can dynamically swing to the potential required to sustain the redox reaction of interest on the working electrode.

[0123] Generally, the reference electrode functions to provide a reference potential for the system, i.e., the potential to which the working electrode is biased is referenced to the reference electrode. A fixed or at least controlled potential relationship may be established between the working and reference electrodes, and, within practical limits, no current is sourced from or sunk by the reference electrode. electrode layer

[0124] As introduced above, the electrodes described herein can include one or more layers or components that facilitate the function of the electrode in the devices described herein, such as, for example, in forming an electrochemical cell for the detection of an analyte of interest. Thus, the electrodes described herein can include, in any combination, one or more of an electrode material or metallization layer, an electrocatalytic layer, a redox pair layer, a sensing layer, a biocompatible layer, an adhesion enhancer, an electrode protection layer, an interferent blocking agent, and a diffusion-limiting layer. The sensing layer, which can be a biorecognition layer, can include a biorecognition element.

[0125] Unless otherwise noted, the exemplary layers and components detailed above and below may be present in or omitted from an electrode in any combination, exemplary combinations of which are described with reference to Figures 11A-12B. a. Electrode material or metallization layer

[0126] The electrode material or metallization layer may be the initial or base layer of the electrode described herein and may provide electrical communication between any remaining layers of the electrode and the structure (e.g., microneedle) on which the electrode is positioned. When used in conjunction with a biorecognition element, the electrode material functions to facilitate electrocatalytic detection of the analyte or the product of the reaction between the analyte and the biorecognition element. The electrode material also provides ohmic contact and routes the electrical signal from the electrocatalytic reaction to processing circuitry. For example, in variations where the electrode is positioned on a microneedle and the microneedle comprises a conductive core or otherwise conductive pathway, the electrode material may be in direct contact with the conductive core or component. The electrode material or metallization layer may comprise any suitable conductive or semiconductive material. For example, the electrode material or metallization layer may comprise platinum, palladium, iridium, rhodium, gold, ruthenium, titanium, nickel, carbon, doped diamond, or a combination thereof. In some variations, the electrode material may comprise a metal salt or metal oxide that functions as a stable redox coupled to a known electrode potential. For example, the metal salt may include, for example, silver-silver chloride (Ag / AgCl) and the metal oxide may include, for example, iridium oxide (IrOx / Ir2O3 / IrO2). In other variations, the noble metal and inert metal surfaces can function as quasi-reference electrodes and can include platinum, palladium, iridium, rhodium, gold, ruthenium, titanium, nickel, carbon, doped diamond, or combinations thereof, and / or other suitable catalytic and inert materials. b. Redox pair layer

[0127] In some variations, the electrodes described herein may include a redox couple layer, which may include a surface-immobilized solid-state redox couple with a stable thermodynamic potential. The redox couple layer may enable the electrode to operate at a stable standard thermodynamic potential relative to the standard hydrogen electrode (SHE). High electrode potential stability can be achieved by using a redox system in which the concentrations of each participant in the redox reaction are constant (e.g., buffered or saturated). For example, the electrode may include saturated Ag / AgCl (E = +0.197 V vs. SHE) or IrOx (E = +0.177 V vs. SHE, pH = 7.00) in the redox couple layer. Other examples of redox couple layers may include suitable conductive polymers with dopant molecules, such as those described in U.S. Patent Application Publication No. 2019 / 0309433 (incorporated herein by reference in its entirety). In some variations, a reference electrode may include a redox couple layer, and the reference electrode may be used as a half-cell to construct a complete electrochemical cell. c. Electrocatalyst layer

[0128] In some variations, the electrodes described herein may include an electrocatalytic layer, which may effectively increase the surface area of ​​the metallization layer to increase the sensitivity of the electrode. Thus, the inclusion of an electrocatalytic layer can increase the electrode surface area to enhance sensitivity. In some examples, the electrode material of the electrode may be coated with the electrocatalytic layer. In some variations, the electrocatalytic layer may be highly porous. In some variations, the electrocatalytic layer may be a platinum black layer and / or may include carbon nanotubes, carbon fibers, elemental platinum, graphene-based materials, metal nanoparticles, quantum dots, iridium, metal-organic frameworks, and covalent organic frameworks, among others.

[0129] In the case of a working electrode that includes a biorecognition layer, the electrocatalytic layer may additionally or alternatively enable electrocatalytic oxidation or reduction of the product of the biorecognition reaction facilitated by the biorecognition layer. However, in some variations of the working electrode, the electrocatalytic layer may be omitted. In such instances, in the absence of the electrocatalytic layer, the electrode may enable electrocatalytic oxidation or reduction of the product of the biorecognition reaction.

[0130] In some variations, the electrocatalyst layer can increase the surface area of ​​the electrode by up to 10 times the surface area of ​​the electrode material alone, hi some variations, the surface area of ​​the electrode with the electrocatalyst layer is about 2 times, about 3 times, about 4 times, about 5 times, about 6 times, about 7 times, about 8 times, about 9 times, or about 10 times the surface area of ​​the electrode without the electrocatalyst layer. d. Biocompatible layer

[0131] The electrodes described herein may, in some variations, further include a biocompatible layer. The biocompatible layer may be, for example, a hydrophilic layer that provides a biocompatible interface to reduce foreign body response. The hydrophilic layer may be added, for example, by plasma polymerization or grafting techniques. In some variations, the hydrophilic layer may be omitted (e.g., if the diffusion-limiting layer exhibits hydrophilic moieties to serve this purpose). In variations, the biocompatible layer may include one or more materials selected from the group consisting of polyurethane, polyether, and the like. e. Biometric recognition layer

[0132] In some variations, the electrode may include a biorecognition layer to which a biorecognition element is immobilized and stabilized to facilitate analyte quantification. For example, in some variations, the biorecognition layer may include a polymer and the biorecognition element may be immobilized therein. In variations, the biorecognition element may be physically entrapped, crosslinked, or otherwise bound to the polymer. For example, rather than being bound to the polymer, the biorecognition element may be physically entrapped within the polymer during polymerization of the polymer. The biorecognition element facilitates selective analyte quantification over extended periods of time (e.g., >7 days). In some variations, the biorecognition element may include an enzyme such as an oxidase. As an exemplary variation for use in a glucose monitoring system, the biorecognition element may include glucose oxidase, which, in the presence of oxygen, converts glucose to an electroactive product (i.e., hydrogen peroxide) that can be detected at the electrode material surface. Specifically, the redox equations associated with this exemplary transformation are glucose + oxygen → hydrogen peroxide + gluconolactone (mediated by glucose oxidase); hydrogen peroxide → water + oxygen (mediated by applying an oxidizing potential to the working electrode).

[0133] However, in other variations, the biorecognition element may additionally or alternatively comprise another suitable enzyme, including oxidase and oxidoreductase enzymes such as glucose dehydrogenase, 3-hydroxybutyrate dehydrogenase, lactate dehydrogenase, lactate oxidase, alcohol oxidase, β-hydroxybutyrate dehydrogenase, tyrosinase, catalase, ascorbate oxidase, cholesterol oxidase, choline oxidase, pyruvate oxidase, urate oxidase, urease, and / or xanthine oxidase.

[0134] In some variations, the biorecognition elements may be crosslinked with amine-fused carbonyl species, which may help stabilize the biorecognition elements within the biorecognition layer. As further described below, in some variations, crosslinking the biorecognition elements may make the microneedle array compatible with ethylene oxide (EO) sterilization, thereby allowing the entire analyte monitoring device (including the sensing element and electronics) to be exposed to the same sterilization cycle, thereby simplifying the sterilization process and potentially reducing manufacturing costs. In some variations, the microneedle array may be compatible with other types of sterilization methods, such as, but not limited to, radiation sterilization.

[0135] For example, biorecognition elements can be crosslinked with glutaraldehyde, formaldehyde, glyoxal, malonaldehyde, succinaldehyde, and / or other suitable species. In some variations, biorecognition elements can be crosslinked with such amine-fused carbonyl species to form crosslinked biorecognition element assemblies. Crosslinked biorecognition element assemblies having at least a threshold molecular weight can then be embedded in a conductive polymer. By embedding only assemblies having a threshold molecular weight, uncrosslinked enzymes can be screened out and not incorporated into the biorecognition layer. Therefore, only assemblies having a desired molecular weight can be selected for use in the conductive polymer to ensure that only sufficiently stabilized crosslinked enzyme entities are included in the biorecognition layer, thereby contributing to a biorecognition layer that is more amenable to EO sterilization overall without compromising sensing performance. In some variations, only crosslinked assemblies having a molecular weight at least twice that of glucose oxidase can be embedded in the conductive polymer.

[0136] In some variations, the polymer in the biorecognition layer may be a conductive polymer. In these variations, the conductive polymer may be permselective to contribute to the robustness of the biorecognition layer against circulating amphoteric electroactive species (e.g., ascorbic acid, vitamin C, etc.), fluctuations of which can adversely affect sensor sensitivity. Such permselective conductive polymers in the biorecognition layer may be more robust against pharmacological interferences in interstitial fluid (e.g., acetaminophen), which can affect sensor accuracy. The conductive polymer can be made permselective, for example, by removing excess charge carriers through an oxidative electropolymerization process or by neutralizing these charge carriers with a counterion dopant, thereby converting the conductive polymer to a non-conductive form. These oxidatively polymerized conductive polymers exhibit permselectivity and can therefore exclude ions of similar charge polarity (net positive or negative) to the dopant ion or by size exclusion due to the dense, compact morphology of the conductive polymer.

[0137] Furthermore, in some variations, the conductive polymer of the biorecognition layer may exhibit self-sealing and / or self-healing properties. For example, the conductive polymer may undergo oxidative electropolymerization, in which the conductive polymer may lose its conductivity as the thickness of the conductive polymer deposited on the electrode increases until the lack of sufficient conductivity reduces the deposition of additional conductive polymer. If the conductive polymer suffers minor physical damage (e.g., during use), the polymer backbone may reassemble to neutralize free charges, thereby lowering the overall surface energy of the molecular structure, which may manifest as self-sealing and / or self-healing properties.

[0138] In some variations, the polymer may be a conductive polymer and may include one or more of aniline, pyrrole, acetylene, phenylene, phenylene vinylene, phenylenediamine, thiophene, 3,4-ethylenedioxythiophene, and aminophenylboronic acid.

[0139] In some variations, the biorecognition element in the biorecognition layer can be a molecule that selectively binds to a given analyte. In some variations, the biorecognition element in the biorecognition layer can be a molecule that selectively and reversibly binds to a given analyte. In some examples, the biorecognition element can be an oligonucleotide. In some variations, the oligonucleotide can be DNA or RNA. The oligonucleotide can be functionalized at the 3' or 5' end. One end can provide a chemical moiety for surface immobilization ("immobilization moiety"), such as an amine, aldehyde, carboxylic acid, thiol, disulfide, azide, n-hydroxysuccinimide (NHS), maleimide, vinyl, silane, chlorosilane, methoxysilane, ethoxysilane, or acetylene group. The immobilization moiety can be separated from the oligonucleotide sequence by a linker selected for its ability to create distance between the oligonucleotide sequence and the surface to which it is immobilized. The linker may also be selected for compatibility with other chemical layers on the electrode surface, such as hydrocarbon linkers with lengths equal to or similar to those used in the self-assembled monolayer coating the remainder of the electrode surface. The opposite end of the oligonucleotide may be functionalized with one or more redox-active molecules that function as probes, such as methylene blue, ferrocene, pentamethylferrocene, C5-ferrocene, Nile blue, thionine, anthraquinone, hydroquinone, C5-anthraquinone, gallocyanine, indophenol, neutral red, dabcyl, π-extended tetrathiafulvalene (exTTF), or carboxy-X-rhodamine. These redox-active molecules may also be attached to the oligonucleotide via custom linkers. The backbone of the oligonucleotide may be modified to enhance stability under physiological conditions. For example, RNA arrays incorporating L-ribose or DNA arrays incorporating L-deoxyribose, as opposed to the natural dextrorotatory sugar, can be used to protect the oligonucleotide from degradation by enzymes in the body.In some variations, backbone modifications can include replacing ribose in RNA or deoxyribose in DNA with 2'-O-methylribose, which also has the effect of protecting against enzymatic cleavage under physiological conditions.

[0140] In some variations, the oligonucleotide may include a region having a nucleotide sequence complementary to a given nucleic acid analyte, such as a viral or bacterial gene or regulatory region, hi some variations, the oligonucleotide may be an aptamer.

[0141] In some examples, the biorecognition element may be a peptide, which may be an antibody or a portion thereof, such as a nanobody (also known as a VHH antibody) that comprises an antigen-binding fragment of a heavy chain-only antibody that selectively binds to a given analyte.

[0142] In some examples, the molecule may be an aptamer ("analyte-binding aptamer"). Aptamers are peptides or single-stranded oligonucleotides that fold into a predetermined structure to selectively bind to a specific analyte (sometimes referred to as a target), which may be, for example, a protein, peptide, hormone, nucleic acid, or small molecule. The recognition and binding of an aptamer to its target involves three-dimensional shape-dependent interactions as well as hydrophobic interactions, base stacking, and intercalation, and is typically reversible by dissociation. Aptamers with affinity for a desired target are conventionally selected from large oligonucleotide libraries by a process called SELEX (Systematic Evolution of Ligands by Exponential Enrichment). Non-binding aptamers are discarded through an iterative process, and aptamers that bind to the proposed target are amplified by polymerase chain reaction (PCR). The iterative process may include counterselection (using interfering substances and structurally similar molecules) to discard aptamers with insufficient selectivity for the analyte. Multiple rounds of SELEX can be performed with increasing stringency to further enrich the oligonucleotide pool until one or more oligonucleotides with the desired degree of affinity and selectivity for the desired target are selected for use.

[0143] In some variations, the analyte-binding aptamer is an aptamer as described in U.S. Provisional Patent Application No. 63 / 478,482, filed January 4, 2023, which is incorporated by reference in its entirety.

[0144] In some variations, the analyte-binding aptamer is a cortisol-binding aptamer defined by the following DNA sequence: 5'-GGACGACGCCAGAAGTTTACGAGGATATGGTAACATAGTCGT-3' (SEQ ID NO: 1) (G, A, C, and T represent typical DNA nucleotides, including guanine, adenine, cytosine, and thymine, respectively).

[0145] In some variations, analyte-binding aptamers may be selected not for maximum affinity for the analyte, but for an intermediate affinity such that a portion of the population of selected aptamers having bound analyte molecules is sensitive to the physiological concentration range of the analyte in skin interstitial fluid, which may be from about 1 pmol / L to about 10 mmol / L, or from about 0.001 μmol / L to about 1 μmol / L. In some variations, the selection criteria for analyte-binding aptamers may include analyte-binding aptamers having an "on" gain of about 10% to about 75% from the minimum to the maximum analyte concentration and / or an "off" gain of about 10% to about 40% from the minimum to the maximum analyte concentration. An "on-gain" signal may refer to a set of square-wave voltammetry parameters (frequency, peak value, step height) selected to maximize the current signal obtained in the presence of the target analyte. An "off-gain" signal may refer to a set of square-wave voltammetry parameters selected to minimize the current signal obtained in the presence of the target analyte. The sensitivity of aptamers to analytes in skin interstitial fluid advantageously makes it possible to avoid interference or signal degradation over time from biofouling or irreversible changes to aptamer structure due to folding or damage.

[0146] The analyte-sensing aptamer can be functionalized with a redox-active molecule, such as methylene blue, ferrocene, pentamethylferrocene, C5-ferrocene, Nile blue, thionine, anthraquinone, C5-anthraquinone, hydroquinone, gallocyanine, indophenol, neutral red, dabcyl, exTTF, or carboxy-X-rhodamine; if the aptamer is an oligonucleotide, the redox-active molecule can be functionalized at the 3' or 5' end of the aptamer. Specific and reversible binding of the analyte to the analyte-binding aptamer and the resulting conformational change of the analyte-binding aptamer can result in a change in the proximity, and therefore the electron transfer properties, between the redox-active molecule and the working electrode to which the aptamer is bound, which corresponds to the analyte concentration. Due to the analyte-binding properties of the aptamer, changes in the electron transfer properties of the electrode correspond to analyte concentration, and these can be investigated by various electrochemical techniques, such as voltammetry, potentiometry, chronoamperometry, and / or electrochemical impedance spectroscopy. Voltammetric techniques vary the potential as a function of time and plot the resulting current as a function of potential. For example, cyclic voltammetry (CV) sweeps the cell potential linearly over a voltage range, while fast-scan CV (FSCV) techniques do this at a faster rate. Alternating current voltammetry (ACV) uses the application of a sinusoidal oscillating voltage to the electrochemical cell. Square-wave voltammetry (SWV) uses a square wave superimposed on a step function to provide sweep measurements, providing two sampling instances per potential. As a result of this sampling technique, the contribution to the total current arising from non-Faradic currents is minimized in SWV. In potentiometry, the open-circuit potential between the reference electrode and the working electrode is measured. In chronoamperometry, the potential is stepped at the beginning of the measurement and then remains constant throughout the duration of the measurement, and the current resulting from this stimulus can be plotted as a function of time. In electrochemical impedance spectroscopy, the complex impedance of the electrode is determined at one or more frequencies.The contributions to impedance (or admittance) from resistive and reactive circuit elements depend on the location of the redox probe attached to the surface-bound aptamer and can be correlated with analyte concentration. f. Diffusion-limiting layer

[0147] In some variations, the electrodes described herein may include a diffusion-limiting layer that can function to limit the flux of the target analyte to reduce the sensor's sensitivity to endogenous oxygen fluctuations. For example, the diffusion-limiting layer can attenuate the concentration of the target analyte so that it becomes the limiting reactant for an aerobic enzyme. In some variations, the diffusion-limiting layer may be a glucose-limiting layer. In variations, the diffusion-limiting layer may include one or more materials selected from the group consisting of polydimethylsiloxane, polyurethane, polyvinyl chloride, polyvinylpyrrolidone, polycarbonate, polyethylene, polyethylene terephthalate, polyester, high-density polyethylene, low-density polyethylene, and polytetrafluoroethylene. g. Adhesion enhancer

[0148] In some variations, the electrodes described herein may include an adhesion promoter within and between layers of each electrode. In some variations, the adhesion promoter may include multiple molecules, which may be reactive molecules (e.g., crosslinkers). The reactive molecules may interact with and / or bond to moieties within and between layers of each electrode. In some variations, the reactive molecules may be at least monofunctional, bifunctional (i.e., homobifunctional or heterobifunctional), and / or trifunctional. The reactive molecules may be amine-reactive. The reactive molecules may have at least one functional group selected from the group including: alkane, alkene, alkyne, aromatic ring, alcohol, ether (including epoxide), amine, thiol, alkyl halide, aldehyde, ketone, carboxylic acid, ester, amide, acid halide, anhydride, nitrile, thioether, nitro, imine, and azide. In some variations, the reactive molecules may include N(1, 2, 3, 4) epoxide functional groups linked to a linker. Such linkers may be aromatic or aliphatic, straight or branched chain of different lengths, and / or may contain repeating oxygen, nitrogen, carbon, and / or sulfur units in various configurations. In some variations, the reactive molecule may be at least one selected from the group including carboxyls, sulfhydryls, carbonyls, carbodiimides, N-hydroxysuccinimide (NHS) esters, imidoesters, epoxides, maleimides, haloacetyls, pyridyl disulfides, hydrazides, alkoxyamines, diazirines, and aryl azides. In some variations, the reactive molecule may be one or more of 1,6-hexanediol diglycidyl ether, neopentyl glycol diglycidyl ether, poly(propylene glycol) diglycidyl ether, trimethylolethane diglycidyl ether, trimethylolpropane triglycidyl ether, diglycidyl resorcinol ether, diglycidyl ether, diethylene glycol diglycidyl ether, 1,4-cyclohexanedimethanol diglycidyl ether, castor oil glycidyl ether, bisphenol A diglycidyl ether, and 1,4-butanediol diglycidyl ether.

[0149] In some variations where the electrode is a working electrode that includes a biorecognition layer and a diffusion-limiting layer, the adhesion-enhancing agent may be between and / or within the biorecognition layer and the diffusion-limiting layer. The adhesion-enhancing agent can improve the stability of the sensor by interacting with and / or binding to moieties within the biorecognition layer and the diffusion-limiting layer, respectively.

[0150] An adhesion enhancer can improve sensor stability by interacting with and / or binding to moieties within the biorecognition layer, the diffusion-limiting layer, and / or the electrode material. The presence or absence of an adhesion enhancer can be based, independently or together, on the relative affinity, material properties, and / or structural properties of other layers, such as the biorecognition layer and the diffusion-limiting layer. For example, the relative affinity between the diffusion-limiting layer and the biorecognition layer can determine whether an adhesion enhancer is required. If the relative affinity is low, the adhesion enhancer can help ensure adhesion between the layers and prevent delamination during insertion. Similarly, the thickness of the diffusion-limiting layer can determine the usefulness of an adhesion enhancer. If the thickness of the diffusion-limiting layer increases, increasing the risk of sensor damage (e.g., delamination) during insertion, an adhesion enhancer can be included. Conversely, if the thickness of the diffusion-limiting layer decreases, minimizing the risk of sensor damage during insertion, an adhesion enhancer can be omitted.

[0151] The adhesion enhancer can interact with the biorecognition layer and the diffusion-limiting layer in various ways. For example, the first end of the adhesion enhancer can covalently bond to a moiety in the biorecognition layer. Such a moiety can include a biorecognition element (e.g., an enzyme) and / or a functional group of the polymer matrix of the biorecognition layer. The second end of the adhesion enhancer can entangle with a moiety of the diffusion-limiting layer via one or more of hydrophilic-hydrophilic interactions, hydrogen bonding, and van der Waals forces, among others.

[0152] In some variations, the reactive molecule of the adhesion promoter can be a bifunctional molecule containing, for example, an amine-reactive functional group, understanding that enzymes are proteins and therefore have free amines. For example, the adhesion promoter can be an epoxide-containing bifunctional molecule, such as 1,4-butanediol diglycidyl ether (BDDGE). BDDGE is a homobifunctional molecule containing epoxide functional groups linked by a linker (similar to the linkers described above). While described below with reference to the working electrode of Figures 12A and 12B, it can be understood that the adhesion promoter is generally applicable to electrodes having the structures and functional groups described herein. h. Interferent blockers

[0153] The electrodes described herein (i.e., working electrodes) comprising an electrode material and a biorecognition layer may further comprise an interferent-blocking agent. The interferent-blocking agent may be present within at least a portion of the plurality of voids in the biorecognition layer. Electropolymerization of the biorecognition layer may result in the formation of an electropolymerized network having voids. The voids may include defects, openings, etc. within the biorecognition layer. The voids may be independent and of any shape and / or size, may be interconnected or isolated, and / or may be uniformly or non-uniformly distributed throughout the biorecognition layer. The voids may run through the thickness of the biorecognition layer and / or may be exposed at the surface of the electrode material, thereby exposing the electrode surface to potential interferents. As described above, access by interferents to the electrode material through the voids may result in an increase in interference current and a decrease in analyte signal. Therefore, to limit access by interferents to the surface of the electrode material through the voids, one or more voids in the biorecognition layer may be at least partially occupied or filled with an interferent-blocking agent. In this way, the interferent blocker can come into direct contact with the electrode material through the voids in the biorecognition layer.

[0154] In some variations, the interferent blocking agent may occupy at least a portion of the voids of the biorecognition layer. For example, the interferent blocking agent may fill at least about 10%, at least about 20%, at least about 30%, at least about 40%, at least about 50%, at least about 60%, at least about 70%, at least about 80%, at least about 90%, or at least about 95% of the total volume of voids ("total void volume"). In another example, the interferent blocking agent may fill about 10% to about 95%, about 20% to about 90%, about 30% to about 80%, about 40% to about 70%, or about 50% to about 60% of the total void volume. In some variations, the interferent blocking agent may occupy at least a portion of each of the filled voids. For example, of the voids of the biorecognition layer that are filled, the interferent blocking agent may occupy at least a portion of each of the filled voids.

[0155] In some variations, the interferent blocking agent may be present in the biorecognition layer at various concentrations, such as about 1% weight per volume (w / v) to about 90% w / v, about 2% w / v to about 80% w / v, about 3% w / v to about 70% w / v, about 4% w / v to about 60% w / v, about 5% w / v to about 50% w / v, about 10% w / v to about 40% w / v, or about 20% w / v to about 30% w / v of the interferent blocking agent in the biorecognition layer. In another example, the interferent blocker can comprise at least about 1% w / v, at least about 2% w / v, at least 3% w / v, at least about 4% w / v, at least about 5% w / v, at least about 6% w / v, at least about 7% w / v, at least about 8% w / v, at least about 9% w / v, at least about 10% w / v, at least about 12% w / v, at least about 14% w / v, at least about 16% w / v, at least about 18% w / v, at least about 20% w / v, at least about 25%, at least about 30% w / v, at least about 40% w / v, at least about 50% w / v, at least about 70% w / v, and / or at least about 90% w / v of the interferent blocker in the biorecognition layer.

[0156] In some variations, there may be a gradient of interferent blocker within the biorecognition layer. For example, the interferent blocker may be preferentially located toward the electrode surface and decrease in concentration within the biorecognition layer away from the electrode surface. A similar gradient, which may be linear, nonlinear, or a combination thereof, may exist across the surface of the electrode material.

[0157] Exemplary interferent blockers may include monomers that are substantially defect-free upon polymerization. In some variations, the interferent blocker may include one or more of resorcinol, hydroquinone quinol, 2-amino-4,6-dinitrophenol picramic acid, 3,5-dihydroxytoluene orcinol, 2,4,6-trinitroresorcinol styphnic acid, 2-hydroxyphenol catechol, 9-phenanthrol, pyrogallol, α-naphthol, anisole, phenetole, picric acid, and phenol. The polymerized monomer or polymer may be a conductive polymer and / or a non-conductive polymer. Non-conductive polymers may include polymers lacking long chain conjugation or reversible redox sites.

[0158] In some variations, the interferent blocker may be a material configured to be one or more of continuous (e.g., defect-free), insulating, and self-limiting. In variations, the interferent blocker strongly adsorbs onto the electrode surface. The adsorbed interferent blocker can be grown from an aqueous buffer solution at physiological pH under electrochemical control. For example, the interferent blocker can be formed by electropolymerization. In variations, the interferent blocker may be a conductive or non-conductive polymer. Furthermore, the interferent blocker may exhibit good permselectivity to common interferents, including acetaminophen and ascorbate, via size-based exclusion or other mechanisms. By being continuous, the interferent blocker can be used for corrosion protection. As an example, the interferent blocker may include a phenol. Polyphenols include polymerized phenol monomers and are generally continuous, insulating, self-limiting, and strongly adsorb onto platinum surfaces.

[0159] In some variations, the inclusion of an interferent blocker in the biorecognition layer reduces the interference current measured in the electrode material. For example, the inclusion of an interferent blocker can maintain the interference current in the electrode material over a one-week period within about 5%, about 10%, about 20%, about 30%, about 40%, about 50%, about 60%, about 70%, about 80%, and / or about 90% of its day-1 value. In another example, the inclusion of an interferent blocker can maintain the interference current in the electrode material over a one-week period within about 0% to about 60%, about 1% to about 50%, about 2% to about 40%, about 3% to about 30%, about 4% to about 20%, about 5% to about 10%, about 6% to about 9%, or about 7% to about 8% of its day-1 value.

[0160] In some variations, the inclusion of an interferent blocker in the biorecognition layer improves the variability in sensor sensitivity by reducing the median sensitivity to an interferent (e.g., acetaminophen) by at least about 25%, at least about 30%, at least about 35%, at least about 40%, at least about 45%, at least about 50%, at least about 55%, at least about 60%, at least about 65%, at least about 70%, at least about 75%, at least about 80%, at least about 85%, at least about 90%, or at least about 95% when compared to a biorecognition layer that does not include the interferent blocker. i. Electrode protective layer

[0161] The electrodes described herein may further include an electrode protection layer in some variations. The electrode protection layer may be a polymer-based layer that protects the electrode material. For example, the electrode protection layer may be a permselective layer or a blocking layer. The electrode protection layer may prevent fouling and / or interaction between the electrode material and the electroactive species. The electrode protection layer may include a hydrophilic material or a charged material. In variations, the electrode protection layer may include one or more materials selected from the group consisting of polyurethane, polyether, and the like. i. Working Electrode—Exemplary Embodiments

[0162] As described above, the working electrode includes a biorecognition element that interacts with the analyte of interest as a participant in analyte detection and quantification. In some variations, analyte detection may be performed at the interface between the working electrode placed in the body and interstitial fluid (e.g., on the outer surface of the entire microneedle). Generally, the working electrode may include an electrode material and a biorecognition layer on which a biorecognition element (e.g., an aptamer, an enzyme) is immobilized to facilitate selective analyte quantification. The biorecognition layer may also function as an interference-blocking layer, helping to prevent, limit, or otherwise inhibit endogenous and / or exogenous species from directly oxidizing (or reducing) at the electrode. In some variations, the working electrode may also include a diffusion-limiting layer, an electrocatalytic layer, an electrode-protecting layer, a biocompatible layer, an adhesion-enhancing agent, and / or an interferent-blocking agent, in any combination and / or arrangement thereof.

[0163] 11A and 11D-11N, exemplary variations of working electrodes are described in the context of exemplary electrode layering, or electrode "stack" configurations.

[0164] FIG. 11A shows a schematic diagram of an exemplary layer set for a working electrode 1110A including an adhesion-enhancing agent. For example, in some variations, the working electrode 1110A may include an electrode material 1112A, a sensing layer including a biorecognition layer 1114A including a biorecognition element, and an adhesion-enhancing agent 1113A. The biorecognition layer 1114A may be disposed on (or disposed on) the electrode material 1112A (or the electrocatalytic layer, if present). The working electrode 1110A may further include a diffusion-limiting layer 1115A disposed on (or disposed on) the biorecognition layer 1114A. The diffusion-limiting layer 1115A can function to limit the flux of the target analyte to reduce the sensor's sensitivity to endogenous oxygen fluctuations, as described above. The adhesion-enhancing agent 1113A may be disposed between and within the biorecognition layer 1114A and the diffusion-limiting layer 1115A to promote adhesion therebetween.

[0165] 11D shows a schematic diagram of an exemplary layer set for a working electrode 1110D including an interferent blocker. For example, in some variations, the working electrode 1110D may include an electrode material 1112D, a sensing layer comprising a biorecognition layer 1114D including a biorecognition element, and an interferent blocker 1116D. The biorecognition layer 1114D may be disposed on (or disposed on) the electrode material 1112D (or the electrocatalytic layer, if present). The working electrode 1110D may further include a diffusion-limiting layer 1115D disposed on (or disposed on) the biorecognition layer 1114D. The diffusion-limiting layer 1115D can function to limit the flux of the analyte of interest to reduce the sensor's sensitivity to endogenous oxygen fluctuations, as described above. The interferent blocking agent 1116D can fill voids within the biorecognition layer 1114D to prevent, limit, or otherwise inhibit exposure of the surface of the electrode material 1112D to foreign matter and the like.

[0166] 11E shows a schematic diagram of an exemplary layer set for a working electrode 1110E including an adhesion-enhancing agent and an interferent-blocking agent. As shown, the working electrode 1110E includes an electrode material 1112E, a sensing layer including a biorecognition layer 1114E including a biorecognition element, an interferent-blocking agent 1116E, an adhesion-enhancing agent 1113E, and a diffusion-limiting layer 1115E. The adhesion-enhancing agent 1113E can be disposed between and within the biorecognition layer 1114E and the diffusion-limiting layer 1115E to promote adhesion therebetween. The adhesion-enhancing agent 1113E can be disposed between and / or within a portion of the biorecognition layer 1114E and the diffusion-limiting layer 1115E. The interferent blocking agent 1116E can fill voids within the biorecognition layer 1114E to prevent, limit, or otherwise inhibit exposure of the surface of the electrode material 1112E to endogenous oxygen fluctuations and / or other solutes, proteins, molecules, foreign substances, etc.

[0167] 12A includes exemplary variations of a working electrode in which an adhesion-enhancing agent interacts with each of a biorecognition layer and a diffusion-limiting layer. To this end, the working electrode includes at least an electrode material 1212, a biorecognition layer 1214, and a diffusion-limiting layer 1215. Additionally, the working electrode may include an adhesion-enhancing agent that includes a linker 1213 that separates a first reactive group 1223′ at a first end of the adhesion-enhancing agent from a second reactive group 1223″ at a second end of the adhesion-enhancing agent. In some variations, the first reactive group 1223′ interacts with the diffusion-limiting layer 1215, and the second reactive group 1223″ interacts across the layer interface with a biorecognition element (e.g., enzyme 1233) in the biorecognition layer 1233. In some variations, the adhesion-enhancing agent may be a bifunctional ether (e.g., BDDGE), with linker 1213 separating a first epoxide group at a first end as first reactive group 1223′ and a second epoxide group at a second end as second reactive group 1223″. To this end, at least one hydroxyl group of the first epoxide group may interact with diffusion-limiting layer 1215 via one or more of hydrogen bonding and van der Waals forces, thereby partially immobilizing the adhesion-enhancing agent, and the second epoxide group may interact covalently (e.g., via a free amine) with a biorecognition element (e.g., enzyme 1233, which may be glucose oxidase) and / or a functional group of the polymer matrix of the biorecognition layer. In some variations, the adhesion-enhancing agent may also interact exclusively within biorecognition layer 1214 or exclusively within diffusion-limiting layer 1215. For example, if biorecognition layer 1214 includes a polymer matrix such as phenylenediamine, the free amines of the phenylenediamine can interact with both ends of adhesion enhancer 1213 (if the adhesion enhancer is an amine-reactive bifunctional molecule).

[0168] 12B , the working electrode may include at least an electrode material 1212, a biorecognition layer 1214, and a diffusion-limiting layer 1215. Additionally, the working electrode may include an adhesion-enhancing agent including a linker 1213 separating a first reactive group 1223′ from a second reactive group 1223″. Unlike the adhesion-enhancing agent of FIG. 12A , the adhesion-enhancing agent of FIG. 12B may interact with either layer of the working electrode. In one example, the first reactive group 1223′ may interact with the diffusion-limiting layer 1215, and the second reactive group 1223″ may interact with a biorecognition element (e.g., an enzyme 1233) in the biorecognition layer 1233 across the layer interface. To this end, if the first reactive group 1223′ is a first epoxide group, at least one hydroxy group of the first epoxide group may interact with the diffusion-limiting layer 1215 via one or more of hydrogen bonding and van der Waals forces, thereby partially immobilizing the adhesion-enhancing agent. Furthermore, if second reactive group 1223" is a second epoxide group, the second epoxide group can interact through a covalent bond with a biorecognition element (e.g., enzyme 1233, which may be glucose oxidase) and / or a functional group of the polymer matrix of the biorecognition layer. In another example, which may occur simultaneously in the presence of multiple adhesion enhancer molecules, first reactive group 1223' can interact with a portion of electrode material 1212, and second reactive group 1223" can interact across the layer interface with a biorecognition element (e.g., enzyme 1233) and / or a functional group of the polymer matrix in biorecognition layer 1233. For this purpose, if the first reactive group 1223′ is a first epoxide group, at least one hydroxyl group of the first epoxide group can interact with a portion of the electrode material 1212 via adhesion, and if the second reactive group 1223″ is a second epoxide group, the second epoxide group can interact with a functional group of the biorecognition element (e.g., enzyme 1233, which may be glucose oxidase) and / or the polymer matrix of the biorecognition layer via a covalent bond.

[0169] FIG. 11F shows a schematic diagram of a working electrode 1110 that includes an interferent blocker without an adhesion enhancer or a separate diffusion-limiting layer. Instead of a separate diffusion-limiting layer as in FIGS. 11A, 11D, and 11E, the working electrode 1110 of FIG. 11F includes an electrode material 1112, a sensing layer including a biorecognition layer 1114 containing a biorecognition element, and an interferent blocker 1116. The interferent blocker 1116 may be located within the void spaces of the biorecognition layer 1114 and may function to limit the flux of the analyte of interest and / or other interferents in tissue to the surface of the electrode material 1112 to reduce the sensor's sensitivity to endogenous oxygen fluctuations and / or other solutes, proteins, molecules, foreign substances, etc. For example, the interferent blocker 1116 may attenuate the concentration of the analyte of interest such that it becomes the limiting reactant for an aerobic enzyme.

[0170] 11G shows a schematic diagram of an exemplary set of layers for a working electrode 1110G. For example, as described above, in some variations, the working electrode 1110G can include an electrode material 1112G and a biorecognition layer 1114G including a biorecognition element. The biorecognition layer 1114G can be disposed on the electrode material 1112G and can function to immobilize and stabilize the biorecognition element, thereby facilitating selective analyte quantification over time. In some variations, the working electrode 1110G can further include a diffusion-limiting layer 1115G disposed on the biorecognition layer 1114G.

[0171] 11H shows an additional configuration of a working electrode 1110H. In this variation, the working electrode 1110H may further comprise a hydrophilic layer 1116H as the outermost layer on the diffusion-limiting layer 1115H.

[0172] 11I shows an additional configuration of the working electrode 1110I. In this variation, the electrode material 1112I may be coated with an electrocatalytic layer 1117I. The configuration of the working electrode 1110I further comprises a biorecognition layer 1114I and a diffusion-limiting layer 1115I as the outermost layer.

[0173] 11J shows an additional configuration of a working electrode 1110J. In this variation, an electrode material 1112J may be coated with an electrocatalytic layer 1117J. A biorecognition layer 1114J is disposed on the electrocatalytic layer 1117J, a diffusion-limiting layer 1115J is disposed on the biorecognition layer 1114J, and a hydrophilic layer 1116J is the outermost layer of the working electrode 1110J.

[0174] 11K shows an additional configuration of a working electrode 1110K. In this variation, an electrode protection layer 1118K is disposed on the electrode material 1112K. A biorecognition layer 1114K is disposed on the electrode protection layer 1118K. A diffusion-limiting layer 1115K is disposed on the biorecognition layer 1114K and can function to limit the flux of the analyte of interest to reduce the sensor's sensitivity to endogenous oxygen fluctuations.

[0175] 11L shows a further configuration of a working electrode 1110L in which a hydrophilic layer 1116L is disposed as an outermost layer on the diffusion-limiting layer 1115L, the biorecognition layer 1114L, the electrode protection layer 1118L, and the electrode material 1112L. As shown, the hydrophilic layer 1116L is disposed on the diffusion-limiting layer 1115L. The electrode protection layer 1118L is disposed on the electrode material 1112L. The biorecognition layer 1114L is disposed on the electrode protection layer 1118L. The diffusion-limiting layer 1115L is disposed on the biorecognition layer 1114L.

[0176] As shown in Figures 11M and 11N, an electrocatalytic layer 1117M, 1117N and an electrode protection layer 1118M, 1118N may be incorporated into the structure of the working electrode 1110M, 1110N. In each working electrode 1110M, 1110N configuration, the electrocatalytic layer 1117M, 1117N is disposed on the electrode material 1112M, 1112N, and the electrode protection layer 1118M, 1118N is disposed on the electrocatalytic layer 1117M, 1117N. The biorecognition layer 1114M, 1114N is disposed on the electrode protection layer 1118M, 1118N, with the diffusion-limiting layer 1114M, 1114N disposed on the biorecognition layer 1114M, 1114N. As shown in Figure 11N, a hydrophilic layer 1116N may be provided as the outermost layer. ii. Counterpole - Exemplary Embodiments

[0177] As described above, the counter electrode is an electrode that supplies or sinks the electrons (via current) necessary to sustain the electrochemical reaction at the working electrode. FIG. 11B illustrates an exemplary variation of the counter electrode 1120. As shown here, the counter electrode 1120 may include an electrode material 1122 similar to electrode materials 1112A, 1112D, 1112E, and 1112F, each of which may include any of the properties and / or characteristics described for the electrode materials in the electrode layer (a) section above. For example, similar to electrode materials 1112A, 1112D, 1112E, and 1112F, the electrode material 1122 in the counter electrode 1120 may include a precious metal such as gold, platinum, palladium, iridium, carbon, doped diamond, and / or other suitable catalytic and inert materials. In some variations, the electrode material 1122 in the counter electrode 1120 may be platinum. 11B, the counter electrode 1120 may be uncoated (i.e., may not have an additional layer on the electrode material 1122). In other variations, the counter electrode 1120 may include an adhesion-enhancing agent 1123 within and on the electrode material 1122 of the counter electrode 1120. The adhesion-enhancing agent 1123 may be bound, for example, by adhesion to portions within the electrode material 1122. In some variations, the counter electrode may also include a diffusion-limiting layer, an electrocatalytic layer, an electrode-protecting layer, a biocompatible layer, and / or an interferent-blocking agent in any combination and / or sequence thereof.

[0178] As mentioned above, the counter electrode is the electrode that supplies or sinks the electrons (via current) necessary to sustain the electrochemical reaction at the working electrode. To avoid the current-carrying capacity of the counter electrode limiting the redox reaction at the working electrode, the number of counter electrodes can be increased in the form of a counter electrode array to increase surface area. Therefore, to avoid current-carrying capacity limitations, it may be desirable to have excess counter electrode area relative to the working electrode area. When the working electrode operates as an anode, the counter electrode functions as a cathode, and vice versa. Similarly, when an oxidation reaction occurs at the working electrode, a reduction reaction occurs at the counter electrode, and vice versa. Unlike the working or reference electrode, the counter electrode can dynamically swing to the potential required to sustain the redox reaction of interest on the working electrode.

[0179] As shown in FIG. 11O, the counter electrode 1120O can include an electrode material 1122O.

[0180] In some variations, the counter electrode 1120O may not have any additional layers on top of the electrode material 1122O, however, in some variations additional layers may be incorporated.

[0181] 11P shows an additional configuration of a counter electrode 1120P. In this variation, the counter electrode 1120P may include a diffusion-limiting layer 1125P disposed on the electrode material 1122P.

[0182] 11Q shows an additional configuration of a counter electrode 1120Q. In this variation, an electrocatalytic layer 1127Q is disposed on an electrode material 1122Q.

[0183] 11R shows an additional configuration of counter electrode 1120R. In this variation, an electrocatalytic layer 1127R is disposed on electrode material 1122R, and a diffusion-limiting layer 1125R is disposed on electrocatalytic layer 1127R.

[0184] 11S shows an additional configuration of a counter electrode 1120S. In this variation, an electrode protection layer 1128S is disposed on the electrode material 1122S. In another variation of the counter electrode 1120S, an electrode protection layer 1128T is disposed on the electrode material 1122T, and a diffusion-limiting layer 1125T is disposed on the electrode protection layer 1128T, as shown in FIG. 11T.

[0185] 11U shows an additional configuration of a counter electrode 1120U. In this variation, an electrode catalyst layer 1127U is disposed on the electrode material 1122U. An electrode protection layer 1128U is disposed on the electrode catalyst layer 1127U.

[0186] 11V shows a counter electrode 1120V including a diffusion-limiting layer 1125V. In particular, an electrocatalytic layer 1127V is disposed on the electrode material 1122V. An electrode protection layer 1128V is disposed on the electrocatalytic layer 1127V. A diffusion-limiting layer 1125V is disposed on the electrode protection layer 1128V. In some variations, a hydrophilic layer may be disposed on the diffusion-limiting layer 1125V. iii. Reference Electrode—Exemplary Embodiments

[0187] As described above, the reference electrode functions to provide a reference potential for the system. FIG. 11C illustrates an exemplary configuration of a reference electrode described herein. As shown, the reference electrode 1130 may include an electrode material 1132 similar to electrode materials 1112A, 1112D, 1112E, 1112F, and 1122 and may include any of the properties and / or characteristics described for the electrode material in the electrode layer (a) section above. In some variations, the reference electrode 1130 may be textured or otherwise roughened to enhance adhesion with any subsequent layers. Such subsequent layers on the electrode material 1132 may include an electrocatalytic layer, which may be a platinum black layer. However, in some variations, the electrocatalytic layer may be omitted. In some variations, the reference electrode may also include a diffusion-limiting layer, an electrode protection layer, a biocompatible layer, and / or an interferent-blocking agent, in any combination and / or sequence thereof.

[0188] The reference electrode 1130 may, in some variations, further include a redox couple layer 1136, as described in more detail above under electrode layer (b).

[0189] In some variations, the reference electrode 1130 may include an adhesion promoter 1133 similar to the adhesion promoter described in section on electrode layer (g). In some variations, an adhesion promoter 1123 may optionally be applied to the reference electrode 1130 to improve the stability of the sensor by interacting with and / or binding to moieties in the redox couple layer 1136 and / or electrode material 1132, respectively.

[0190] 11C, at least one terminus of the adhesion enhancer 1133 may interact with a moiety within the redox pair layer 1136. Such interaction may be by covalent bonding and / or adhesion.

[0191] As shown in FIG. 11W, the reference electrode 1130W can include electrode material 1132W, similar to electrode material 1112W.

[0192] Additionally or alternatively, in some variations shown in FIG. 11X, the reference electrode 1130X may include a diffusion-limiting layer 1135X (e.g., disposed over the electrode and / or redox pair layer).

[0193] 11Y shows an additional configuration of a reference electrode 1130Y. In this variation, an electrode protection layer 1138Y is disposed on the electrode material 1132Y, and a redox couple layer 1136Y is disposed on the electrode protection layer 1138Y.

[0194] 11Z shows an additional configuration of a reference electrode 1130Z in which an electrode protection layer 1138Z is disposed on the electrode material 1132Z, a redox couple layer 1136Z is disposed on the electrode protection layer 1138Z, and a diffusion-limiting layer 1135Z is disposed on the redox couple layer 1136Z. electrode formation

[0195] The various layers of working, counter, and reference electrodes can be applied and / or functionalized to the microneedle array using appropriate processes as described below.

[0196] First, in a microneedle array pretreatment step, the microneedle array can be plasma cleaned in an inert gas (e.g., an RF-generated inert gas such as argon) plasma environment to make the surfaces of materials, including electrode materials (e.g., electrode materials 1112, 1122, and 1132 as described above), more hydrophilic and chemically reactive. This pretreatment not only physically removes organic debris and contaminants, but also cleans and prepares the electrode surfaces to enhance adhesion of films subsequently deposited thereon. iv. Working electrode-formation

[0197] The various layers of the working electrode may be applied to and / or functionalized on the microneedle array using a suitable process, such as those described below with reference to Figures 13A and 13D-13F.

[0198] As described with reference to method 1300A provided in FIG. 13A, the adhesion promoter can be applied to the working electrode, for example, as a solution, as a vapor, and / or as a gas, and in a variety of ways.

[0199] As described below with reference to method 1300D of FIG. 13D , method 1300E of FIG. 13E , and method 1300F of FIG. 13F , the interferent blocking agent can be applied to the working electrode in a variety of ways, including, for example, as a solution, a vapor, and / or a gas, as well as immersion and electropolymerization, among others. As described above, the interferent blocking agent may be a material configured to be one or more of continuous (e.g., defect-free), insulating, and self-limiting. In variations, the interferent blocking agent strongly adsorbs onto the electrode surface. The interferent blocking agent may exhibit good permselectivity to common interferents, including acetaminophen and ascorbate, via size-based exclusion or other mechanisms. Being continuous allows the interferent blocking agent to be used for corrosion protection. In some variations, including the interferent blocking agent in the biorecognition layer reduces interference current, i.e., the interference current measured at the electrode material.

[0200] Regardless of which exemplary working electrode is described, anodization and activation occurs after pretreatment, as described above.

[0201] Specifically, to construct the working electrode after the pretreatment step, the electrode material may undergo anodization using an amperometric approach, in which the electrode component assigned to the working electrode function is exposed to a fixed high anodic potential (e.g., +1.0 to +1.3 V vs. an Ag / AgCl reference electrode) in a moderate-strength acidic solution (e.g., 0.1 to 3 M H2SO4) for an appropriate time (e.g., about 30 seconds to about 10 minutes). In this process, a thin but stable native oxide layer can be produced on the electrode surface. Due to the low pH that occurs at the electrode surface, trace contaminants can also be removed.

[0202] In an alternative variation using coulometric techniques, anodization can proceed until a specified amount of charge (measured in coulombs) has passed. As described above, an anodic potential may be applied. However, the duration of this can vary until the specified charge amount has elapsed.

[0203] Following the anodization process, the working electrode component may be subjected to a periodically scanned potential waveform in an activation process using cyclic voltammetry. In the activation process, which may occur in a moderately strong acidic solution (e.g., 0.1-3 M H2SO4), the applied potential may be varied over time according to an appropriate function (e.g., a sawtooth function). For example, the voltage may be linearly scanned between cathodic values ​​(e.g., -0.3 to -0.2 V vs. an Ag / AgCl reference electrode) and anodic values ​​(e.g., +1.0 to +1.3 V vs. an Ag / AgCl reference electrode) in an alternating function (e.g., 15 to 50 linear sweep segments). The scan rate for this waveform may range from 1 to 1000 mV / s. It should be noted that current peaks occurring during the anodic sweep (swirl toward the positive electrode) correspond to the oxidation of the chemical species, while current peaks occurring during the subsequent cathodic sweep (swirl toward the negative electrode) correspond to the reduction of the chemical species.

[0204] 13A and 13D-13F, respectively, after completion of electrode material pretreatment, anodization, and activation, which may each be performed as described above, the working electrode component may be functionalized with a biorecognition layer in step 1310 of methods 1300A, 1300D, 1300E, and 1300F. The voltage may be linearly scanned in an alternating function (e.g., 10 linear sweep segments) between cathodic values ​​(e.g., −0.5 V to 0.0 V vs. an Ag / AgCl reference electrode) and anodic values ​​(e.g., 0.5 V to +1.5 V vs. an Ag / AgCl reference electrode). In an exemplary variation, the scan rate of this waveform may range from about 1 mV / sec to about 1,000 mV / sec in an aqueous solution consisting of a monomer precursor of a capture conductive polymer and a crosslinked biorecognition element (e.g., an enzyme such as glucose oxidase). In this process, a thin film (e.g., about 10 nm to about 1000 nm) of biorecognition layer comprising a polymer with dispersed crosslinked biorecognition elements can be produced (e.g., by electrodeposition or electropolymerization) on the surface of the working electrode. In some variations, the polymer can be a conductive polymer.

[0205] In some variations, the working electrode surface can be electrochemically roughened to enhance adhesion of the biorecognition layer to the electrode material surface. The roughening process can involve cathodic deposition (e.g., cathodic deposition, a subset of amperometry), in which the electrode is subjected to a fixed cathodic potential (e.g., −0.4 to +0.2 V vs. an Ag / AgCl reference electrode) for a specific time (e.g., 5 seconds to 10 minutes) in an acidic solution (e.g., 0.01 to 100 mM HPtCl) containing the desired metal cations dissolved therein. Alternatively, the electrode is subjected to a fixed cathodic potential (e.g., about −0.4 to about +0.2 V vs. an Ag / AgCl reference electrode) in an acidic solution (e.g., 0.01 to 100 mM HPtCl) containing the desired metal cations dissolved therein until a certain amount of charge (e.g., 0.1 mC to 100 mC) has passed. In this process, a thin but highly porous layer of metal is produced on the electrode surface, thereby dramatically increasing the electrode surface area.

[0206] 13A and 13E, following deposition of the biorecognition layer in step 1310, an adhesion-promoting agent can be deposited (i.e., applied) onto the biorecognition layer in step 1320 of methods 1300A and 1300E. The adhesion-promoting agent can be deposited according to any suitable method, including, but not limited to, drop casting, spray coating, immersion, spin coating, and chemical vapor deposition. For example, the adhesion-promoting agent can be deposited onto the biorecognition layer by immersing the functionalized and activated electrode material in a solution containing the adhesion-promoting agent. In some variations, the immersion can be carried out for 0 hours to 2 weeks, 1 day to 13 days, 2 days to 12 days, 3 days to 11 days, 4 days to 10 days, 5 days to 9 days, and / or 6 days to 8 days. In some variations, the soaking may be carried out for about 0.1 hours to about 24 hours, about 0.2 hours to about 23 hours, about 0.3 hours to about 22 hours, about 0.4 hours to about 21 hours, about 0.5 hours to about 20 hours, about 0.6 hours to about 19 hours, about 0.7 hours to about 18 hours, about 0.8 hours to about 17 hours, about 0.9 hours to about 16 hours, about 1 hour to about 15 hours, about 2 hours to about 14 hours, about 3 hours to about 13 hours, about 4 hours to about 12 hours, about 5 hours to about 11 hours, about 6 hours to about 10 hours, and / or about 7 hours to about 9 hours. In some variations, the soaking may be carried out for about 1 minute to about 30 minutes, about 2 minutes to about 25 minutes, about 3 minutes to about 20 minutes, about 4 minutes to about 15 minutes, about 5 minutes to about 10 minutes, and / or about 7 minutes to about 8 minutes. In some variations, the solution may have a pH of about 4 to about 14, about 5 to about 13, about 6 to about 12, about 7 to about 11, and / or about 8 to about 10. In some variations, the solution may have a pH of about 7 to about 10, about 7.5 to about 9.5, and about 8 and / or about 9. In some variations, the concentration of the adhesion enhancer in the solution may be about 0.05% to about 30% w / v or w / w. In some variations, the concentration of the adhesion enhancer in the solution may be about 0.1% to about 20%, about 0.5% to about 15%, about 1% to about 10%, about 2% to about 9%, about 3% to about 8%, about 4% to about 7%, and / or about 5% to about 6%.

[0207] With particular reference now to Figures 13D, 13E, and 13F, following deposition of the biorecognition layer in step 1310, an interferent blocking agent can be deposited (i.e., applied) onto the biorecognition layer in step 1315 of methods 1300D, 1300E, and 1300F of Figures 13D, 13E, and 13F. The interferent blocking agent can be deposited according to any suitable method, including, but not limited to, drop casting, spray coating, immersion, spin coating, and chemical vapor deposition. For example, the interferent blocking agent can be applied to the biorecognition layer by immersing the functionalized and activated electrode material in a solution containing the interferent blocking agent. In some variations, the immersion can be performed for 0 hours to 2 weeks, 1 day to 13 days, 2 days to 12 days, 3 days to 11 days, 4 days to 10 days, 5 days to 9 days, and / or 6 days to 8 days. In some variations, the soaking may be carried out for about 0.1 hours to about 24 hours, about 0.2 hours to about 23 hours, about 0.3 hours to about 22 hours, about 0.4 hours to about 21 hours, about 0.5 hours to about 20 hours, about 0.6 hours to about 19 hours, about 0.7 hours to about 18 hours, about 0.8 hours to about 17 hours, about 0.9 hours to about 16 hours, about 1 hour to about 15 hours, about 2 hours to about 14 hours, about 3 hours to about 13 hours, about 4 hours to about 12 hours, about 5 hours to about 11 hours, about 6 hours to about 10 hours, and / or about 7 hours to about 9 hours. In some variations, the soaking may be carried out for about 1 minute to about 30 minutes, about 2 minutes to about 25 minutes, about 3 minutes to about 20 minutes, about 4 minutes to about 15 minutes, about 5 minutes to about 10 minutes, and / or about 7 minutes to about 8 minutes. In some variations, the solution may have a pH of about 4 to about 14, about 5 to about 13, about 6 to about 12, about 7 to about 11, and / or about 8 to about 10. In some variations, the solution may have a pH of about 7 to about 10, about 7.5 to about 9.5, and about 8 and / or about 9. In some variations, the concentration of the interferent blocking agent in the solution may be about 0.05% to about 30% w / v or w / w. In some variations, the concentration of the interferent blocking agent in the solution may be about 0.1% to about 20%, about 0.5% to about 15%, about 1% to about 10%, about 2% to about 9%, about 3% to about 8%, about 4% to about 7%, and / or about 5% to about 6%.In some variations, the concentration of the interferent blocker in solution can be from about 0.1 mM to about 1 M, from about 1 mM to about 100 mM, from about 5 mM to about 20 mM, and / or from about 7.5 mM to about 10 mM.

[0208] In the variation shown in FIG. 13F, after deposition of the interferent blocking agent in step 1315 of method 1300F, the working electrode is ready for use.

[0209] 13A, 13D, and 13E, following deposition of one or more of the adhesion promoters in step 1320 of method 1300A of FIG. 13A and method 1300E of FIG. 13E and the interferent blocking agent in step 1315 of method 1300D of FIG. 13D and method 1300E of FIG. 13E, the working electrode component may be functionalized with a diffusion-limiting layer. The diffusion-limiting layer, which may be a thin film having a thickness of about 100 nm to about 10,000 nm, can be applied using one or more of the following methods:

[0210] In some variations, the diffusion-limiting layer can be applied by a spray coating method, in which an aerosolized polymer formulation (dispersed in water or a solvent) is applied to the microneedle array device in a controlled environmental setting with a specific spray pattern and duration, thereby forming a thin film with the desired thickness and porosity necessary to limit the diffusion of the analyte of interest to the biorecognition layer.

[0211] In some variations, the diffusion-limiting layer may be applied by a plasma-induced polymerization method in which a plasma source provides energy and generates a gas discharge that activates a cross-linking reaction within a gaseous, aerosolized, or liquid monomer precursor (e.g., vinylpyridine), converting the monomer precursor into a polymer coating that can be deposited at a specific thickness onto the microneedle array, thereby creating a thin film with the desired thickness and porosity necessary to limit the diffusion of the analyte of interest into the biorecognition layer.

[0212] Additionally, in some variations, the diffusion-limiting layer may be applied by electrophoretic or dielectrophoretic deposition, such as the exemplary techniques described in U.S. Pat. No. 10,092,207, which is incorporated herein by reference in its entirety. v. Opposite pole - formation

[0213] The various layers of the counter electrode may be applied to the microneedle array and / or functionalized, etc. using suitable processes as described below.

[0214] In some variations, the counter electrode material can be anodized using an amperometric approach, in which the electrode component assigned to the counter electrode function is exposed to a constant high anodic potential or a moderately strong acidic solution for an appropriate time. Exemplary parameters and other details of the counter electrode anodization process can be similar to those described above for the working electrode. Similarly, the counter electrode anodization can alternatively use a coulometric technique as described above.

[0215] In some variations, following the anodization process, the counter electrode component may be subjected to a periodically scanned potential waveform in an activation process using cyclic voltammetry, which may be similar to the process described above for the working electrode.

[0216] Additionally, in some variations, the surface of the counter electrode may be electrochemically roughened to enhance the current sinking or current supplying capabilities of this electrode. The electrochemical roughening process may be similar to that described above for the working electrode.

[0217] In some variations, the adhesion enhancer may be applied to the counter electrode, for example, as a solution, as a vapor, and / or as a gas, and by several means, as described herein with reference to method 1300B of FIG. 13B.

[0218] Referring again to FIG. 13B , after completion of pretreatment, anodization, activation, and / or roughening of the electrode material, each of which may be performed as described above, an adhesion promoter may be deposited (i.e., applied) onto the electrode material in step 1320 of method 1300B of FIG. 13B . The adhesion promoter may be deposited according to any suitable method, including, but not limited to, drop casting, spray coating, immersion, spin coating, and chemical vapor deposition. For example, the adhesion promoter may be deposited onto the electrode material by immersing the functionalized and activated electrode material in a solution containing the adhesion promoter. In some variations, the immersion may be performed for 0 hours to 2 weeks, 1 day to 13 days, 2 days to 12 days, 3 days to 11 days, 4 days to 10 days, 5 days to 9 days, and / or 6 days to 8 days. In some variations, the soaking may be carried out for about 0.1 hours to about 24 hours, about 0.2 hours to about 23 hours, about 0.3 hours to about 22 hours, about 0.4 hours to about 21 hours, about 0.5 hours to about 20 hours, about 0.6 hours to about 19 hours, about 0.7 hours to about 18 hours, about 0.8 hours to about 17 hours, about 0.9 hours to about 16 hours, about 1 hour to about 15 hours, about 2 hours to about 14 hours, about 3 hours to about 13 hours, about 4 hours to about 12 hours, about 5 hours to about 11 hours, about 6 hours to about 10 hours, and / or about 7 hours to about 9 hours. In some variations, the soaking may be carried out for about 1 minute to about 30 minutes, about 2 minutes to about 25 minutes, about 3 minutes to about 20 minutes, about 4 minutes to about 15 minutes, about 5 minutes to about 10 minutes, and / or about 7 minutes to about 8 minutes. In some variations, the solution may have a pH of about 4 to about 14, about 5 to about 13, about 6 to about 12, about 7 to about 11, and / or about 8 to about 10. In some variations, the solution may have a pH of about 7 to about 10, about 7.5 to about 9.5, and about 8 and / or about 9. In some variations, the concentration of the adhesion enhancer 1123 in the solution may be about 0.05% to about 30% w / v or w / w. In some variations, the concentration of the adhesion enhancer 1123 in the solution may be about 0.1% to about 20%, about 0.5% to about 15%, about 1% to about 10%, about 2% to about 9%, about 3% to about 8%, about 4% to about 7%, and / or about 5% to about 6%.

[0219] In some variations, the counter electrode may have few or no additional layers on top of the electrode material. However, in some variations, the counter electrode may benefit from increased surface area to increase the amount of current it can support. For example, the counter electrode material may be textured or otherwise roughened to increase the surface area of ​​the electrode material to enhance its current source or sink capability. In some variations, the counter electrode may include an electrocatalytic layer. The electrocatalytic layer may include a platinum black layer, which may increase the electrode surface, as described above with respect to the electrocatalytic layer described in section (c) of electrode layer. However, in some variations of the counter electrode, the platinum black electrocatalytic layer may be omitted (e.g., as shown in FIG. 11B). vi.Reference electrode-formation

[0220] The various layers of the reference electrode may be applied to the microneedle array and / or functionalized, etc. using appropriate processes as described below.

[0221] Similar to the working and counter electrodes described above, the reference electrode can be anodized using an amperometric approach, in which the electrode component assigned to the counter electrode function is exposed to a constant high anodic potential or a moderate strength acid solution for an appropriate time. Exemplary parameters and other details of the anodization process for the counter electrode can be similar to those described above for the working electrode. Similarly, the anodization of the reference electrode can alternatively use a coulometric technique as described above.

[0222] Following the anodization process, the reference electrode component may be subjected to a periodically scanned potential waveform in an activation process using cyclic voltammetry, which, in some variations, may be similar to the process described above for the working electrode.

[0223] Additionally, in some variations, the reference electrode surface can be electrochemically roughened to enhance adhesion of the surface-immobilized redox couple. The electrochemical roughening process can be similar to that described above for the working electrode.

[0224] In some variations, the adhesion enhancer 1133 may be applied to the reference electrode 1130, for example, as a solution, as a vapor, and / or as a gas, and by several means, as described herein with reference to method 1300C of FIG. 13C.

[0225] Referring again to FIG. 13C, after completion of pretreatment, anodization, and activation of the electrode material 1132, each of which may be performed as described above, in step 1314 of method 1300C, the reference electrode component may be functionalized with a redox couple layer 1136. To this end, a fixed anodic potential (e.g., +0.4 to +1.0 V vs. an Ag / AgCl reference electrode) may be applied in aqueous solution for a certain suitable period of time (e.g., about 10 seconds to about 10 minutes). Alternatively, the reference electrode may be subjected to a fixed anodic potential (e.g., about +0.4 to about +1.0 V vs. an Ag / AgCl reference electrode) until a certain amount of charge passes through the aqueous solution (e.g., 0.01 mC to 10 mC). In some variations, the aqueous solution may include a monomer precursor of a conductive polymer and an oppositely charged dopant counterion or material (e.g., poly(styrene sulfonate)). In this process, a thin film (e.g., about 10 nm to about 10,000 nm) of conductive polymer with dispersed counterions or materials can be produced on the surface of the reference electrode material 1132. This results in a surface-immobilized solid-state redox coupled with a stable thermodynamic potential. In some variations, the conductive polymer can include one or more of aniline, pyrrole, acetylene, phenylene, phenylene vinylene, phenylenediamine, thiophene, 3,4-ethylenedioxythiophene, and aminophenylboronic acid.

[0226] In some alternative variations, a native iridium oxide film (e.g., IrO2 or Ir2O3 or IrO4) can be electrochemically grown on the iridium electrode surface in an oxidation process, which also generates a stable redox couple, as described above.

[0227] Following deposition of the redox couple layer in step 1314, an adhesion promoter can be deposited (i.e., applied) onto the redox couple layer. The adhesion promoter can be deposited according to any suitable method, including, but not limited to, drop casting, spray coating, immersion, spin coating, and chemical vapor deposition. For example, the adhesion promoter can be deposited onto the redox couple by immersing the functionalized and activated electrode material in a solution containing the adhesion promoter. In some variations, the immersion can be carried out for 0 hours to 2 weeks, 1 day to 13 days, 2 days to 12 days, 3 days to 11 days, 4 days to 10 days, 5 days to 9 days, and / or 6 days to 8 days. In some variations, the soaking may be carried out for about 0.1 hours to about 24 hours, about 0.2 hours to about 23 hours, about 0.3 hours to about 22 hours, about 0.4 hours to about 21 hours, about 0.5 hours to about 20 hours, about 0.6 hours to about 19 hours, about 0.7 hours to about 18 hours, about 0.8 hours to about 11 hours, about 0.9 hours to about 16 hours, about 1 hour to about 15 hours, about 2 hours to about 14 hours, about 3 hours to about 13 hours, about 4 hours to about 12 hours, about 5 hours to about 11 hours, about 6 hours to about 10 hours, and / or about 7 hours to about 9 hours. In some variations, the soaking may be carried out for about 1 minute to about 30 minutes, about 2 minutes to about 25 minutes, about 3 minutes to about 20 minutes, about 4 minutes to about 15 minutes, about 5 minutes to about 10 minutes, and / or about 7 minutes to about 8 minutes. In some variations, the solution may have a pH of about 4 to about 14, about 5 to about 13, about 6 to about 12, about 7 to about 11, and / or about 8 to about 10. In some variations, the solution may have a pH of about 7 to about 10, about 7.5 to about 9.5, and about 8 and / or about 9. In some variations, the concentration of the adhesion enhancer in the solution may be about 0.05% to about 30% w / v or w / w. In some variations, the concentration of the adhesion enhancer in the solution may be about 0.1% to about 20%, about 0.5% to about 15%, about 1% to about 10%, about 2% to about 9%, about 3% to about 8%, about 4% to about 7%, and / or about 5% to about 6%.

[0228] Additionally or alternatively, in some variations, the reference electrode may include a diffusion-limiting layer (e.g., disposed or over the electrode and / or redox pair layer). The diffusion-limiting layer may be similar to the diffusion-limiting layer described above under electrode layer (f). In some variations in which a diffusion-limiting layer is included, the reference electrode may further include a hydrophilic layer that provides a biocompatible interface, e.g., to reduce foreign body response. The hydrophilic layer may be disposed or over the diffusion-limiting layer.

[0229] In some variations, the reference electrode may include an electrode protection layer, such as those described with reference to the working electrode and / or counter electrode. The electrode protection layer may be disposed on (or disposed on) the electrode material, or in variations involving an electrocatalytic layer, the electrode protection layer is disposed on the electrocatalytic layer, if provided.

[0230] Other features and techniques for forming the reference electrode may be similar to those described, for example, in U.S. Patent Application Publication No. 2019 / 0309433, incorporated above by reference. Microneedle array configuration

[0231] The microneedle arrays described herein can have a high degree of configurability with respect to where the working, counter, and reference electrodes are located within the microneedle array, and this configurability can be facilitated by the electronics system.

[0232] In some variations, the microneedles may be equidistantly spaced from one another (e.g., the same pitch in all directions) for more consistent penetration. To that end, in some variations, the microneedles in the microneedle array may be arranged in a hexagonal configuration, as shown in Figures 14, 15, 16A-16J, 17A-17F, and 20A. For example, as shown in Figure 14, an exemplary variation of a microneedle array having seven microneedles is shown. The microneedle arrangement includes four microneedles assigned as two independent groups (1 / 2 and 3 / 4) of two working electrodes (WE), a counter electrode (CE) consisting of two microneedles, and a single reference electrode (RE). There is a symmetry in the arrangement of the working and counter electrodes, which are equidistant from the central reference electrode. Furthermore, the working electrode is positioned as far away from the center of the microneedle array (e.g., the periphery of the die or array) as possible to take advantage of locations where the working electrode is expected to have higher sensitivity and overall performance. Alternatively, the microneedles of the microneedle array may be arranged in a rectangular array (e.g., a square array) or another suitable symmetrical manner. Alternatively, the microneedles of the microneedle array may be arranged in a rectangular array (e.g., a square array) or another suitable symmetrical manner.

[0233] In some variations, the microneedle array can include electrodes distributed symmetrically or asymmetrically within the microneedle array into two or more groups, each group featuring the same or different numbers of electrode components depending on signal sensitivity and / or redundancy requirements. For example, electrodes of the same type (e.g., working electrodes) may be distributed bilaterally or radially symmetrically within the microneedle array. For example, FIG. 16A shows a variation of a microneedle array 1600A including two symmetric groups of seven working electrodes (WE), with the two working electrode groups labeled "1" and "2." In this variation, the two working electrode groups are distributed bilaterally symmetrically within the microneedle array. The working electrodes are generally positioned between a central region of three reference electrodes (RE) and an outer peripheral region of 20 counter electrodes (CE). In some variations, each of the two working electrode groups can include seven working electrodes electrically connected therebetween (e.g., to enhance the sensor signal). Alternatively, only a portion of one or both of the working electrode groups may include multiple electrodes electrically connected therebetween. As yet another alternative, the working electrodes may include working electrodes that are freestanding and not electrically connected to other working electrodes. Additionally, in some variations, the working electrodes may be distributed across the microneedle array in an asymmetric or random configuration.

[0234] As another example, FIG. 16B shows a variation of microneedle array 1600B that includes four symmetric groups of three working electrodes (WE), with the four working electrode groups labeled "1," "2," "3," and "4." In this variation, the four working electrode groups are radially symmetrically distributed across the microneedle array. Each working electrode group is adjacent to and symmetrically positioned with one of two reference electrode (RE) components in the microneedle array. The microneedle array also includes counter electrodes (CE) positioned around the periphery of the microneedle array, except for two electrodes at the vertices of a hexagon that may be inactive or used for other features or modes of operation.

[0235] In some variations, only a portion of the microneedle array may include active electrodes. For example, Figure 16C shows a variation of a microneedle array 1600C having 37 microneedles and a reduced number of active electrodes, including four working electrodes (labeled "1," "2," "3," and "4") in a bilateral symmetrical arrangement, 22 counter electrodes, and three reference electrodes. The remaining eight electrodes of the microneedle array are inactive.

[0236] As another example, FIG. 16D shows a variation of microneedle array 1600D having 37 microneedles and a reduced number of active electrodes, including four working electrodes (labeled "1," "2," "3," and "4") arranged symmetrically on both sides, 20 counter electrodes, and three reference electrodes; the remaining 10 electrodes of the microneedle array are inactive.

[0237] As another example, Figure 16E shows a variation of a microneedle array 1600E having 37 microneedles and a reduced number of active electrodes, including four working electrodes (labeled "1," "2," "3," and "4"), 18 counter electrodes, and two reference electrodes. The remaining 13 electrodes of the microneedle array are inactive. The inactive electrodes are along a partial periphery of the overall microneedle array, thereby reducing the effective size and shape of the active microneedle array to a smaller hexagonal array. Within the active microneedle array, the four working electrodes are generally arranged in a radially symmetrical fashion, with each working electrode surrounded by a group of counter electrodes.

[0238] Figure 16F shows another exemplary variation of a microneedle array 1600F having 37 microneedles and a reduced number of active electrodes, including four working electrodes (labeled "1," "2," "3," and "4"), two counter electrodes, and one reference electrode. The remaining 30 electrodes of the microneedle array are inactive. The inactive electrodes are arranged in two layers around the periphery of the overall microneedle array, thereby reducing the effective size and shape of the active microneedle array to a smaller hexagonal array centered on the reference electrode. Within the active microneedle array, the four working electrodes are in a bilateral symmetrical arrangement, and the counter electrodes are equidistant from the central reference electrode.

[0239] Figure 16G shows another exemplary variation of a microneedle array 1600G having 37 microneedles and a reduced number of active electrodes. The active electrodes of the microneedle array 1600G are arranged similarly to the microneedle array 1600F shown in Figure 16F, except that the microneedle array 1600G includes one counter electrode and two reference electrodes, with a smaller, hexagonal array of active microneedles centered around the counter electrode. Within the active microneedle arrangement, the four working electrodes are in a bilateral symmetrical arrangement, and the reference electrodes are equidistant from the central counter electrode.

[0240] Figure 16H shows another exemplary variation of a microneedle array 1600H having seven microneedles. The microneedle arrangement includes two microneedles designated as independent working electrodes (1 and 2), a counter electrode condition consisting of four microneedles, and a single reference electrode. There is a symmetry in the arrangement of the working and counter electrodes, which are equidistant from the central reference electrode. Furthermore, the working electrode is placed as far away from the center of the microneedle array (e.g., at the periphery of the die or array) as possible to take advantage of locations where the working electrode is expected to have higher sensitivity and overall performance.

[0241] Figure 16I shows another exemplary variation of a microneedle array 1600I having seven microneedles. The microneedle arrangement includes four microneedles assigned as two independent groups (1 and 2) of two working electrodes each, a counter electrode consisting of two microneedles, and a single reference electrode. There is a symmetry in the arrangement of the working and counter electrodes, which are equidistant from the central reference electrode. Furthermore, the working electrodes are placed as far away from the center of the microneedle array (e.g., the periphery of the die or array) as possible to take advantage of locations where the working electrodes are expected to have higher sensitivity and overall performance.

[0242] Figure 16J shows another exemplary variation of a microneedle array 1600J having seven microneedles. The microneedle arrangement includes four microneedles designated as independent working electrodes (1, 2, 3, and 4), a counter electrode condition consisting of two microneedles, and a single reference electrode. There is symmetry in the arrangement of the working and counter electrodes, which are equidistant from the central reference electrode. Furthermore, the working electrode is positioned as far away from the center of the microneedle array (e.g., the periphery of the die or array) as possible to take advantage of locations where the working electrode is expected to have higher sensitivity and overall performance.

[0243] While Figures 16A-16J show exemplary variations of microneedle array configurations, it should be understood that these figures are not limiting and other microneedle configurations (including different numbers and / or distributions of working, counter, and reference electrodes, and different numbers and / or distributions of active and inactive electrodes, etc.) may be suitable for other variations of microneedle arrays.

[0244] Considerations for how to configure the microneedles include factors such as the desired insertion force for penetrating the skin with the microneedle array, optimization of electrode signal levels and other performance aspects, and manufacturing cost and complexity.

[0245] A plurality of microneedles (e.g., any of the microneedle variations described herein, each of which may have a working electrode, a counter electrode, or a reference electrode) can be arranged in a microneedle array. For example, a microneedle array can include multiple microneedles spaced apart at a predetermined pitch (the distance between the center of one microneedle and the center of its nearest neighboring microneedle). In some variations, the microneedles can be spaced apart at a pitch sufficient to distribute the force applied to a user's skin to penetrate the microneedle array (e.g., avoiding a "needle-rat" effect). As the pitch increases, the force required to insert the microneedle array tends to decrease and the depth of penetration tends to increase. However, it has been found that the pitch begins to affect insertion force only at low values ​​(e.g., less than about 150 μm). Thus, in some variations, the microneedles of the microneedle array may have a pitch of at least 200 μm, at least 300 μm, at least 400 μm, at least 500 μm, at least 600 μm, at least 700 μm, or at least 750 μm. For example, the pitch may be from about 200 μm to about 800 μm, from about 300 μm to about 700 μm, or from about 400 μm to about 600 μm. In some variations, the microneedles may be arranged in a periodic grid, and the pitch may be uniform across all directions and across the entire area of ​​the microneedle array. Alternatively, the pitch may be different when measured along different axes (e.g., X and Y directions), and / or some areas of the microneedle array may include a smaller pitch and other areas may include a larger pitch.

[0246] Another consideration for determining the configuration of a microneedle array is the overall signal level provided by the microneedles. Generally, the signal level at each microneedle is consistent with the total number of microneedle elements in the array. However, the signal level can be enhanced by electrically interconnecting multiple microneedles within the array. For example, an array with a large number of electrically connected microneedles is expected to generate a greater signal strength (and therefore, improved accuracy) than an array with fewer microneedles. However, a larger number of microneedles on a die increases die cost (for a given pitch) and also requires greater force and / or speed for insertion into the skin. In contrast, a smaller number of microneedles on a die reduces die cost and allows for insertion into the skin with reduced applied force and / or speed. Furthermore, in some variations, a smaller number of microneedles on a die may reduce the overall footprint area of ​​the die, potentially reducing undesirable local edema and / or erythema. Thus, in some variations, a balance of these factors can be achieved with a microneedle array comprising 37 microneedles as shown in Figures 17E-17F, or a microneedle array comprising 7 microneedles as shown in Figures 17A-17D. However, in other variations, the number of microneedles in the array may be fewer (e.g., about 5 to about 35, about 5 to about 30, about 5 to about 25, about 5 to about 20, about 5 to about 15, about 5 to about 100, about 10 to about 30, about 15 to about 25, etc.) or the number of microneedles in the array may be greater (e.g., greater than 37, greater than 40, greater than 45, etc.).

[0247] Additionally, as described in more detail below, in some variations, only a subset of the microneedles in the microneedle array may be active during operation of the analyte monitoring device. For example, some of the microneedles in the microneedle array may be inactive (e.g., no signal is read from the electrodes of the inactive microneedles). In some variations, some of the microneedles in the microneedle array may be activated at a particular time during operation and remain active for the remainder of the operational life of the device. Furthermore, in some variations, some of the microneedles in the microneedle array may additionally or alternatively be deactivated at a particular time during operation and remain inactive for the remainder of the operational life of the device.

[0248] Considering the characteristics of the die for a microneedle array, the die size is a function of the number of microneedles in the microneedle array and the pitch of the microneedles. Manufacturing costs should also be considered, as a smaller die size contributes to lower costs because it increases the number of dies that can be formed from a single wafer of a given area. Furthermore, a smaller die size is also less susceptible to brittle fracture due to the relative fragility of the substrate.

[0249] Furthermore, in some variations, microneedles at the periphery of the microneedle array (e.g., near the edge or border of the die, near the edge or border of the housing, near the edge or border of an adhesive layer on the housing, along the outer edge of the microneedle array, etc.) may be found to have better performance (e.g., sensitivity) due to better penetration compared to microneedles at the center of the microneedle array or die. Thus, in some variations, the working electrode may be located mostly or entirely on microneedles located at the periphery of the microneedle array to obtain more accurate and / or precise analyte measurements.

[0250] 17A and 17B show perspective views of an exemplary schematic of seven microneedles 1710 arranged in an exemplary variation of a microneedle array 1700. The seven microneedles 1710 are arranged in a hexagonal array on a substrate 1702. As shown in FIG. 17A, electrodes 1720 are disposed on distal portions of the microneedles 1710 extending from a first surface of the substrate 1702. As shown in FIG. 17B, proximal portions of the microneedles 1710 are conductively connected to respective backside electrical contacts 1730 on a second surface of the substrate 1702 opposite the first surface of the substrate 1702. FIGS. 17C and 17D show plan and side views of an exemplary schematic of a microneedle array similar to the microneedle array 1700. As shown in Figures 17C and 17D, the seven microneedles are arranged in a hexagonal array with a center-to-center pitch of about 750 μm between the center of each microneedle and the center of its immediately adjacent microneedle in any direction. In other variations, the center-to-center pitch may be, for example, about 700 μm to about 800 μm, or about 725 μm to about 775 μm. The microneedles may have an approximate outer axial diameter of about 170 μm (or about 150 μm to about 190 μm, or about 125 μm to about 200 μm) and a height of about 500 μm (or about 475 μm to about 525 μm, or about 450 μm to about 550 μm).

[0251] 17E and 17F show exemplary schematic diagrams of 37 microneedles arranged in an exemplary variation of a microneedle array. The 37 microneedles may be arranged in a hexagonal array, for example, with a needle-to-needle center-to-center pitch of about 750 μm (or about 700 μm to about 800 μm, or about 725 μm to about 775 μm) between the center of each microneedle and the center of its immediately adjacent microneedle in any direction. FIG. 17E shows an exemplary schematic diagram of an exemplary variation of a die 1750 including the microneedle arrangement. Exemplary dimensions of the die 1200 (e.g., about 4.4 mm by about 5.0 mm) and the microneedle array 1750 are shown in FIG. 17F.

[0252] Due to the construction of microneedle arrays having separate, spaced apart microneedles, each configured to function as a particular electrode type, additional consideration of how the electrode types are configured (e.g., arranged) within the microneedle array may be beneficial. For example, user tissue located between the microneedles due to the spaced apart configuration of the electrodes may affect the operation of the electrochemical cell.

[0253] In an electrochemical cell containing a working electrode, a counter electrode, and a reference electrode, the working electrode requires a constant bias (also referred to as a reference potential and / or reference bias). The reference electrode is used as a bias setpoint for the negative terminal of the working electrode. The counter electrode attempts to maintain a constant bias by adjusting the voltage of the counter electrode through feedback received from the reference electrode. However, due to the microneedle array configuration with spaced electrodes (e.g., the tissue between the electrodes has an associated resistance), tissue resistance is inserted into the system and affects the operation of the electrochemical cell. Tissue resistance, in conjunction with the current flowing between the working and counter electrodes, can induce a voltage drop between the working and reference electrodes, leading to bias degradation at the working electrode. Furthermore, bias degradation varies with normal working electrode operation (e.g., the concentration of the analyte being measured is represented by a range of current values) and tissue resistance, which is not a controlled variable and may vary across the insertion site.

[0254] The problem can be compounded in microneedle array configurations with multiple working electrodes. Because variations exist not only within tissue resistance but also between working electrode resistances, bias degradation of the working electrodes is inconsistent between working electrodes. This inconsistency can result in different levels of tracking performance between working electrodes in multiple working electrode configurations.

[0255] In an ideal environment, a constant voltage drop is required across each of the working electrodes. In an electrochemical cell having a working electrode, a counter electrode, and a reference electrode, an attempt is made to maintain a constant voltage drop across the counter electrode based on feedback from the reference electrode and through adjustment of the counter electrode voltage. The ability of the counter electrode to maintain a constant voltage drop depends on the structure and deployment characteristics of the electrode (e.g., the insertion characteristics of the microneedle). The adjustment made by the counter electrode takes into account changes in the impedance and current of the working electrode, as well as process-induced impedance variations between the working electrodes. However, the voltage adjustment capability of the counter electrode is limited in practical implementation, and the electrochemical cell is only effective over a specific current range of the working electrode.

[0256] Therefore, there is a need for improved working electrode bias stabilization as well as improved bias matching in systems with multiple working electrodes.

[0257] Aspects of the present disclosure aim to configure a microneedle array by taking tissue (e.g., body) resistance into consideration. To remedy the above-mentioned deficiencies, the present disclosure provides a microneedle array having a zero-current environment within a voltage guard where only residual reference electrode current flows. When current flows between the working electrode and the current electrode in a microneedle array configuration, the zero-current environment ensures that the working electrode bias is not affected by tissue resistance and reference electrode resistance.

[0258] 18A is a simplified microneedle array sensor model 1800 that reflects aspects related to the spacing between electrodes. The natural and inherent resistance from each electrode (e.g., R WE , R of the reference electrode 1810 RE , and R of the counter electrode 1820 CE ), tissue resistance exists between each electrode 1802, 1810, 1820 and the body interface 1830. For example, R body1 is the tissue resistance between the reference electrode 1810 and the body interface 1830, and R body2is the tissue resistance between the working electrode 1802 and the body interface 1830, and R body3 is the tissue resistance between the counter electrode 1820 and the body interface 1830. The tissue resistance between the working electrode 1802 and the reference electrode 1810 induces a voltage drop proportional to the current between them, resulting in degradation of the working electrode bias that is dependent on the tissue resistance. Because tissue resistance is an uncontrolled variable, the degradation of the working electrode bias will vary across the application site and can lead to a loss of analyte tracking ability. Furthermore, high tissue resistance values, R body3 This can cause the counter electrode 1820 to appear to exceed its current carrying capacity, causing the voltage on the counter electrode 1820 to stick to the rail.

[0259] FIG. 18B is a simplified microneedle array sensor model 1850 that reflects aspects related to inter-electrode spacing, having two working electrodes, working electrode 1802 and working electrode 1804. In multi-channel configurations incorporating more than one working electrode, such as that shown in FIG. 18B, degradation of working electrode bias may be inconsistent, leading to channel-to-channel performance differences on the same microneedle array. The working electrode resistance (R WE1 and R WE2 ) and tissue resistance values ​​can lead to variations in analyte tracking performance between working electrodes 1802 and 1804. Furthermore, the variations also depend on the deployment of the microneedle array (e.g., insertion of the microneedles) and therefore vary from use to use.

[0260] 19A is a microneedle array sensor model 1900 illustrating aspects related to stabilization of the working electrode bias for use in a tissue resistance environment. As shown, the reference electrode 1910 is body2 The error induced by is moved to a position outside the voltage guard of the reference electrode 1910.

[0261] To stabilize the working electrode bias in a microneedle array configuration, the present disclosure provides a zero current environment within a voltage guard where only the reference electrode resistance flows. When current flows between the working electrode and the current electrode in a microneedle array configuration, the zero current environment ensures that the working electrode bias is not affected by the tissue resistance and the reference electrode resistance.

[0262] To implement an embodiment of the sensor model 1910 of FIG. 19A in a microneedle array configuration, the effects of the geometric distribution of tissue resistance can be offset by considering non-uniform current flow across the microneedle array.

[0263] 19B provides a depiction of a microneedle array configuration 1950 in which the reference electrode 1810 is positioned within a zero current (e.g., constant potential) zone 1960. When current flows between the working and counter electrodes, working electrode bias effects due to voltage drops from tissue resistance are minimized. The zero current and constant potential zone 1960, in which the reference electrode is included, provides a reference electrode voltage that is evenly spread across the working electrodes, thereby providing improved stabilization of the working electrode bias and matching the bias of each working electrode provided in the microneedle array configuration.

[0264] In some variations, the number of working electrodes required is at least the minimum number necessary to isolate the reference electrode from the current flowing between the working electrode and the counter electrode. Because the number of microneedles may be fixed due to substrate and / or manufacturing constraints or requirements, the electrodes may be configured to form zero current zones accordingly. In particular, for a fixed number of microneedles (and associated electrodes), the electrodes may be allocated among the microneedle array to meet the requirement to isolate the reference electrode from the current flowing between the working electrode and the counter electrode.

[0265] In some variations in which multiple counter electrodes are included in a microneedle array configuration, the counter electrodes may be electrically connected in parallel. In this arrangement, the current from a first working electrode flows primarily to the counter electrode closest to the first working electrode. For example, the majority of the current from a first working electrode flows to the first counter electrode, where the first counter electrode is positioned closest to the first working electrode relative to the other counter electrodes.

[0266] 20A-20F show exemplary schematic diagrams of different variations of microneedle array configurations. As described further herein, each electrode may be disposed on the surface of a tapered distal portion of each microneedle of the plurality of microneedles forming the microneedle array.

[0267] 20A shows a microneedle array 2000 having seven microneedles arranged in a hexagonal configuration. The microneedle array 2000 includes three working electrodes (WE1, WE2, and WE3), three counter electrodes (CE1, CE2, and CE3), and one reference electrode (RE). The three working electrodes form a barrier around the reference electrode to provide stabilization of the working electrode bias according to embodiments described herein. The barrier between the reference electrode and the counter electrode formed by the working electrode prevents current flowing from the working electrode to the counter electrode from flowing through the reference electrode.

[0268] In the configuration of the microneedle array 2000, one working electrode (WE2) on each microneedle is disposed (e.g., located) in a central region of the semiconductor substrate above the central microneedle. The microneedle on which the counter electrode is formed is at the edge of the microneedle array 2000 and is close to (e.g., adjacent to) a first edge of the semiconductor substrate. The microneedle on which the reference electrode is formed is also at the edge of the microneedle array and is close to (e.g., adjacent to) a second edge of the semiconductor substrate opposite the first edge. In the variation shown in FIG. 20A, the microneedles are equidistantly spaced from each other (e.g., the same pitch in all directions), and the working electrodes are uniformly spaced from the reference electrode. Because the distances between the microneedles WE1 and CE1, WE2 and CE2, and WE3 and CE3 are equal, most of the current from WE1 flows to CE1, and most of the current from WE3 flows to CE3. In the configuration of microneedle array 2000 in Figure 20A, each microneedle is the same distance from the central microneedle where WE2 is located.

[0269] In some variations, only a portion of the microneedle array may include active electrodes. For example, one or more of the microneedles of the microneedle array may include no electrodes or may include electrodes that are inactive. In such an arrangement, electrodes may be allocated among the microneedle array without consideration of the inactive electrodes. For example, FIG. 20B shows a microneedle array 2010 having nine microneedles arranged in a rectangular configuration. The microneedle array 2010 includes two working electrodes (WE1 and WE2), two counter electrodes (CE1 and CE2), and one reference electrode (RE). The remaining four microneedles do not include active electrodes (e.g., no electrode material and / or layers thereon are provided). The two working electrodes form a barrier around the one reference electrode to provide stabilization of the working electrode bias according to embodiments described herein. Since the distance between the microneedles of WE1 and CE1 and the distance between the microneedles of WE2 and CE2 are equal, most of the current from WE1 flows to CE1, and most of the current from WE3 flows to CE3.

[0270] Figure 20C shows a microneedle array 2020 having 19 microneedles arranged in a hexagonal configuration. The configuration shown in Figure 20C includes two reference electrodes (RE1 and RE2) on each outer edge of the microneedle array 2020, each surrounded by multiple working electrodes (WE1, WE2, WE3, and WE4 surrounding RE1, and WE5, WE6, WE7, and WE8 surrounding RE2) that form a barrier between the corresponding reference electrode (RE1 and RE2) and the corresponding counter electrode (CE1, CE2, CE3, and CE4, and CE5, CE6, CE7, and CE8). In some variations, as shown in Figure 20C, the centrally located microneedle does not include an active electrode. In the variation shown in Figure 20C, the microneedles are equidistantly spaced from each other (e.g., the same pitch in all directions).

[0271] In some variations utilizing a microneedle array having 19 microneedles in a hexagonal configuration, a centrally located microneedle may be configured as an additional counter electrode, and in some variations, one or more of the other counter electrodes may be configured as working electrodes (e.g., the number of counter electrodes need not equal the number of working electrodes).

[0272] FIG. 20D shows a microneedle array 2030 having a centrally positioned reference electrode (RE) surrounded by six working electrodes (WE1, WE2, WE3, WE4, WE5, and WE6). Counter electrodes (CE1, CE2, CE3, CE4, CE5, and CE6) are positioned outside the barrier formed by the working electrodes. In some variations, two groups of counter electrodes (CE1, CE2, and CE3 as one group and CE4, CE5, and CE6 as a second group) may be provided, as shown in the example configuration of FIG. 20D. In some variations, the number of working electrodes and / or the number of counter electrodes may vary. For example, a group of counter electrodes may include one or more counter electrodes. In variations in which the number of counter electrodes is reduced, additional working electrodes may be provided, or some of the microneedles may not include an active electrode.

[0273] Figure 20E shows a microneedle array 2040 having two centrally positioned reference electrodes (RE1 and RE2) surrounded by multiple (e.g., six) working electrodes. Counter electrodes (CE1, CE2, CE3, and CE4) are positioned outside the barrier formed by the working electrodes. In some variations, fewer counter electrodes may be provided. In some variations, additional working electrodes may be provided. Thus, the number of working electrodes and / or the number of counter electrodes may differ from the example shown in Figure 20E. Alternatively, one of the reference electrodes may be replaced with a working electrode.

[0274] Figure 20F shows a microneedle array 2050 having two hexagonal arrangements of microneedles. Each hexagonal arrangement includes the configuration 2000 shown in Figure 20A. The two hexagonal arrangements are arranged side by side in the variation shown in Figure 20F, but may be arranged in different configurations relative to each other. Additional arrangements of microneedles (hexagonal or otherwise) may also be incorporated.

[0275] 20A-20F show particular microneedle and electrode configurations, the present disclosure is not limited to the particular arrangements shown. For example, the number of working, counter, and reference electrodes may differ from the examples shown. Additionally or alternatively, the electrode arrangement may vary. For example, microneedles may be fabricated in a variety of ways, such that the present disclosure is not limited to hexagonal and rectangular configurations.

[0276] As seen in Figures 20A-20F, one or more reference electrodes (which may be only one reference electrode) are removed from the current path between one or more working electrodes and one or more counter electrodes. Generally, the one or more working electrodes form a barrier between one or more reference electrodes and one or more counter electrodes. The reference electrode (or electrodes) are surrounded by a working electrode, which is surrounded by a counter electrode, and the working electrode forms a barrier around the reference electrode. This contrasts with conventional and earlier implementations, where the focus of microneedle array configuration was to arrange working electrodes around the periphery of the microneedle array. Positioning the working electrode at the periphery was thought to increase the accuracy of analyte measurements. However, this configuration failed to take into account the tissue resistance of the working electrode and the associated bias stabilization issues, which are the focus of the present subject matter.

[0277] In some variations, microneedle arrays consistent with implementations of the present subject matter may be configured to sense multiple analytes. For example, with reference to FIG. 18B, separate working electrode potentials, V WE1 and V WE2 can generate the different working electrode biases needed to sense different analytes relative to a common reference electrode. In some variations, two separate electrochemical cells may be provided on a single substrate, such as in the configurations of Figures 20C, 20E, and 20F. Use of the Analyte Monitoring System

[0278] The following provides an overview of various aspects of methods of use and operation of the analyte monitoring system, including the analyte monitoring device and peripherals.

[0279] As described above, the analyte monitoring device is applied to a user's skin such that the microneedle array within the device penetrates the skin and the electrodes of the microneedle array are positioned in the upper dermis for access to cutaneous interstitial fluid. For example, in some variations, the microneedle array may be geometrically configured to penetrate the outer layer of skin, the stratum corneum, penetrate the epidermis, and rest within the papillary or upper reticular dermis. The sensing area limited to the electrodes in the distal extent of each microneedle element of the array (as described above) may be configured to remain resting and seated in the papillary or upper reticular dermis after application to ensure adequate exposure to circulating cutaneous interstitial fluid (ISF) without risk of bleeding or undue influence from nerve endings.

[0280] In some variations, the analyte monitoring device may include a wearable housing or patch having an adhesive layer configured to adhere to the skin and secure the microneedle array in place. While the analyte monitoring device may be applied manually (e.g., by removing a protective film on the adhesive layer and manually pressing the patch onto the skin at the desired wear site), in some variations, the analyte monitoring device may be applied to the skin using a suitable applicator.

[0281] The analyte monitoring device may be applied to any suitable location, although in some variations it may be desirable to avoid anatomical regions of thick or raw skin (e.g., palmar and plantar regions), or regions that undergo significant flexion (e.g., olecranon or patella). Suitable application sites may include, for example, the arms (e.g., upper arms, lower arms), shoulders (e.g., over the deltoid muscles), backs of the hands, neck, face, scalp, torso (e.g., on the back, such as the pectoral region, lumbar region, sacral region, or on the chest or abdomen), buttocks, legs (e.g., upper legs, lower legs, etc.), and / or tops of the feet, etc.

[0282] As mentioned above, in some variations, the analyte monitoring device may be configured to automatically activate upon insertion and / or confirm proper insertion into the skin. Details of these features are described in more detail above. In some variations, methods for such activation and / or confirmation may be similar to those described in U.S. Patent Application No. 16 / 051,398, incorporated by reference above.

[0283] Once the analyte monitoring device is inserted and warm-up and any calibration are complete, the analyte monitoring device may be ready to provide a sensor measurement of a target analyte. The target analyte (and any necessary cofactors) diffuse from the biological environment through a biocompatible and diffusion-limiting layer on the working electrode to a biorecognition layer containing a biorecognition element. In the presence of the cofactor (if present), the biorecognition element may convert the target analyte into an electroactive product.

[0284] A bias potential can be applied between the working and reference electrodes of the analyte monitoring device, and a current can be applied from the counter electrode to maintain a fixed potential relationship between the working and reference electrodes. This causes the electroactive product to be oxidized or reduced, resulting in a current flow between the working and counter electrodes. The current value is proportional to the rate of the redox reaction at the working electrode, and specifically, proportional to the concentration of the analyte of interest according to the Cottrell relationship, as described in more detail above.

[0285] The current may be converted to a voltage signal by a transimpedance amplifier and quantized into a digital bitstream by an analog-to-digital converter (ADC). Alternatively, the current may be quantized directly into a digital bitstream by a current-mode ADC. The digital representation of the current may be processed within an embedded microcontroller within the analyte monitoring device and relayed to a wireless communication module for broadcast or transmission (e.g., to one or more peripheral devices). In some variations, the microcontroller may perform additional algorithmic processing on the data to improve signal fidelity, accuracy, and / or calibration, etc.

[0286] In some variations, the digital representation of the current or sensor signal can be correlated with an analyte measurement (e.g., a glucose measurement) by the analyte monitoring device. For example, a microcontroller can execute programmed routines in firmware to interpret the digital signal and perform any associated algorithms and / or other analyses. Keeping the analysis on-board the analyte monitoring device can, for example, allow the analyte monitoring device to broadcast analyte measurements to multiple devices in parallel, ensuring that each connected device has the same information. Thus, in general, a user's target analyte (e.g., glucose) value can be estimated, stored in the analyte monitoring device, and communicated to one or more peripheral devices.

[0287] Data exchange can be initiated by either the mobile application or the analyte monitoring device. For example, the analyte monitoring device can notify the mobile application of new analyte data as it becomes available. The frequency of updates can vary, for example, from about 5 seconds to about 5 minutes and can depend on the type of data. Additionally or alternatively, the mobile application can request data from the analyte monitoring device (e.g., if the mobile application identifies a gap in collected data due to a disconnection, etc.).

[0288] When the mobile application is not connected to the analyte monitoring device, the mobile application may not receive data from the sensor electronics. However, the electronics in the analyte monitoring device may store each actual and / or estimated analyte data point. When the mobile application reconnects to the analyte monitoring device, the mobile application can request the data that was missed during the disconnection period, and the electronics on the analyte monitoring device can transmit that data set as well (e.g., backfill).

[0289] Generally, the mobile application may be configured to provide a real-time or near-real-time display of analyte measurement data, such as on a display of a mobile computing device executing the mobile application. In some variations, the mobile application may communicate via a user interface regarding analysis of the analyte measurements, such as alerts, alarms, trend insights, etc., to notify the user of analyte measurements requiring attention or follow-up action (e.g., high analyte measurements, low analyte measurements, high rates of change, analyte measurements outside of preset ranges, etc.). In some variations, the mobile application may additionally or alternatively facilitate communication of the measurement data to a cloud for storage and / or archiving for later retrieval. [Example]

[0290] Example 1. Adhesion Enhancer Layer As described in detail herein, including an adhesion enhancer in an electrode can improve sensing at the working electrode, for example. Exemplary data obtained for a working electrode formed according to method 1300A of FIG. 13A will now be described with reference to FIGS. 21A-25.

[0291] FIG. 21A graphically illustrates the effect of increasing the concentration of adhesion enhancer on sensor sensitivity for sterilized (S) or non-sterilized (NS) working electrodes. Sensor sensitivity is on the y-axis. 48 samples were evaluated for each group. Sterilization can be performed as described elsewhere herein. Notably, a decrease in sensor sensitivity and a decrease in sensor sensitivity variability are observed as the adhesion enhancer concentration increases from 0% to 0.5%, 1%, and 4%. In other words, these data suggest that sensor sensitivity can be tuned by adjusting the adhesion enhancer concentration. Furthermore, FIG. 21A shows that sterilization does not significantly affect the sensitivity of the working electrode at any concentration of adhesion enhancer.

[0292] Figure 21B graphically illustrates the reproducibility of adhesion enhancer treatment for working electrodes treated by immersion in a 4% concentration of BDDGE in solution. Sensor sensitivity is on the y-axis. As shown in Figure 21A, the three replicates in Figure 21B (Replicate 1, Replicate 2, Replicate 3) demonstrate the significant reduction in sensor sensitivity and reduced variability in sensor sensitivity achieved with modification with an adhesion enhancer (e.g., BDDGE).

[0293] Similarly, Figures 21C-21F graphically illustrate the durability of adhesion-enhancing agent treatment. In each of Figures 21C-21F, sensor sensitivity is on the y-axis, and the number of days after treatment is shown on the x-axis. In Figure 21C, 43 samples were evaluated. In Figure 21D, 44 samples were evaluated. In Figure 21E, 47 samples were evaluated. In Figure 21F, 44 samples were evaluated. For each group, glucose standard calibration was performed each day using 0 mM, 2 mM, 10 mM, and 22 mM glucose. At night, each sensor was soaked in 2 mM glucose. Consistent with the results in Figure 21A, it can be seen from Figures 21C-21F that the average sensor sensitivity decreased with increasing adhesion-enhancing agent concentration, as shown on the y-axis, while the vertical height of each box (in the boxplots) decreased with increasing adhesion-enhancing agent concentration. This confirms that increasing the concentration of adhesion enhancer reduces the sensor sensitivity and reduces the variability in sensor sensitivity.

[0294] Figures 21G-21J convey similar information, graphically illustrating sensor drift over time. For each of Figures 21G-21J, sensor sensitivity is on the y-axis, and the number of days after treatment is shown on the x-axis. Each trace in Figures 21G-21J represents measurements for a specific sample. In Figure 21G, 43 samples were evaluated. In Figure 21H, 44 samples were evaluated. In Figure 21I, 47 samples were evaluated. In Figure 21J, 44 samples were evaluated. For each group, calibration with glucose standards was performed each day using 0 mM, 2 mM, 10 mM, and 22 mM glucose. At night, each sensor was soaked in 2 mM glucose. As can be seen, sensor variability improved with increasing concentrations of adhesion enhancer, and this improvement was maintained over the 6-day test period.

[0295] Figures 22A-22D graphically illustrate the persistence of sensor response (in nanoamperes) to cyclically increasing glucose exposure. In Figures 22A and 22C, the sensor was treated with a 4% concentration of BDDGE. In Figures 22B and 22D, the sensor was not treated with an adhesion-enhancing agent. For each of Figures 22A-22D, the current generated by the sensor is on the y-axis, and the time of glucose infusion, at which a spike reflects increasing glucose infusion, is shown on the x-axis. Each trace in Figures 22A-22D represents a sensor measurement for a particular sample. As can be observed, sensor sensitivity decreased with increasing concentrations of the adhesion-enhancing agent, and this improvement was maintained over the 6-day test period. Furthermore, sensor variability was also improved for sensors treated with the adhesion-enhancing agent, as indicated by the lack of divergent traces in Figures 22A and 22C with increasing glucose concentrations.

[0296] FIG. 23 graphically illustrates the sensor drift on day 5 normalized to day 1. The y-axis represents the percentage difference between the sensor sensitivity on day 5 and day 1, while the x-axis represents the concentration of adhesion enhancer applied to the sensor. Specifically, the y-axis reflects the numerical value of the drift rate calculated as the difference between the sensitivity on day 1 and the sensitivity on day 5 normalized by the sensitivity on day 1. As can be observed, sensor drift was significantly improved with the application of any concentration of adhesion enhancer.

[0297] Figures 24A and 24B graphically show sensor performance before and after insertion, and with and without the application of an adhesion enhancer. With sensitivity before insertion on the x-axis and sensitivity after insertion on the y-axis, it can be seen that the application of an adhesion enhancer improves sensor stability. The scatter in Figure 24A shows that insertion damaged the untreated sensor, resulting in unpredictable sensitivity. However, the treated sensor in Figure 24B appears to be minimally affected by insertion.

[0298] Figure 25 graphically illustrates the effect of an adhesion enhancer on the impedance and phase angle of the sensor under applied frequency. Impedance and phase angle are on the left and right y-axes, respectively, and frequency is on the x-axis. It can be observed that the phase angle of the treated sample (w / AE) decreases significantly with increasing frequency compared to the control (w / oAE). Specifically, Figure 25 is a Bode plot. Specific frequencies or frequency bands translate into characteristics of the biorecognition layer. As evidenced by the difference in impedance between these two groups, the impedance is greater when the adhesion enhancer is included, indicating that the biorecognition layer contains a greater degree of crosslinking density, resulting in improved stability.

[0299] Example 2. Interferent Blockers As noted earlier, the inclusion of an interferent blocker in the electrodes described herein improves sensing at the working electrode by reducing interference currents caused by interferent exposure to the electrode surface. Exemplary data obtained for a working electrode formed according to method 1300E of FIG. 13E will now be described with reference to FIGS. 26A-29. However, it should be understood that similar results would be expected for a working electrode formed according to method 1300D of FIG. 13D, which also features an interferent blocker but does not include an adhesion-enhancing agent.

[0300] Figures 26A and 26B graphically illustrate the effect of including an interferent blocker on the sensitivity of the working electrode according to Figure 11E. The working electrodes in Figures 26A and 26B include a biorecognition layer containing phenylenediamine (PPD) and, optionally, an interferent blocker containing polyphenols (PPh). Thirty-two working electrodes were functionalized and randomly assigned to two groups: (a) a control group (1x sample size) and (b) an experimental group (3x sample size). Interference sensitivity was measured with 0.1 mM, 0.2 mM, and 0.5 mM acetaminophen in PBS without glucose. As shown in Figure 26A, the results indicated that the inclusion of an interferent blocker improved the variability of sensor sensitivity, reducing the median sensitivity to acetaminophen by approximately 75% when compared to PPH without the interferent blocker (shown in Figure 26B).

[0301] Figure 27 graphically illustrates the effect of increasing the concentration of interferent blocker on sensor sensitivity for the working electrode according to Figure 11E. The working electrode in Figure 27 includes a biorecognition layer containing PPD and, optionally, an interferent blocker containing phenol. Three experimental groups (0 mM, 50 mM, and 100 mM phenol monomer solutions in PBS at pH 7.5) were evaluated over a 5-day period to determine the effect of phenol on long-term sensor sensitivity. As shown, a decrease in sensor sensitivity and a decrease in sensor sensitivity variability were observed as the interferent blocker concentration increased from 0 mM to 50 mM to 100 mM.

[0302] 28A-28C graphically illustrate the effect of increasing acetaminophen concentration and increasing interferent blocker concentration on sensor sensitivity over time (e.g., days 2 and 4 are shown on the x-axis) for the working electrode according to FIG. 11E. The working electrodes in FIGS. 28A-28C include a biorecognition layer comprising PPD and, optionally, an interferent blocker comprising PPh. That is, without the interferent blocker, sensor sensitivity and variability increased with increasing acetaminophen concentration. However, with increasing concentrations of the interferent blocker, sensor sensitivity and variability relatively decreased with increasing acetaminophen concentration.

[0303] Figure 29 graphically illustrates the effect of increasing concentrations of acetaminophen on sensor sensitivity for the working electrode according to Figure 11D. The working electrode of Figure 11D includes a biorecognition layer comprising PPD and, optionally, an interferent blocker comprising PPh. As shown, the interferent blocker significantly reduces sensor sensitivity at any concentration of acetaminophen.

[0304] The results of FIG. 29 are supported in Table 1, which provides in tabular form the effect of the presence and increasing concentration of phenol in the working electrode described herein on reducing the presence of acetaminophen (Ac) in the working electrode over time. [Table 1]

[0305] The foregoing description, for purposes of explanation, used specific nomenclature to provide a thorough understanding of the invention. However, it will be apparent to those skilled in the art that specific details are not required to practice the present invention. Thus, the foregoing descriptions of specific variations of the present invention have been presented for purposes of illustration and description. They are not intended to be exhaustive or to limit the invention to the precise forms disclosed. Obviously, many modifications and variations are possible in light of the above teachings. The variations were chosen and described in order to explain the principles of the invention and its practical application, thereby enabling those skilled in the art to utilize the present invention and its various variations with various modifications as appropriate to the particular use contemplated. It is intended that the following claims and their equivalents define the scope of the invention. Numbered Embodiments for Carrying Out the Invention

[0306] Without limiting the scope of the appended claims, the present disclosure describes the following numbered embodiments.

[0307] (1) A device for use in sensing an analyte, comprising: a microneedle; an electrode material on the microneedle; a biorecognition layer on the electrode material, the biorecognition layer comprising a polymer, a biorecognition element configured to react with the analyte, and an interferent blocking agent filling voids within the polymer; and a diffusion-limiting layer on the biorecognition layer.

[0308] (2) The device described in (1), wherein the voids in the polymer extend through the thickness of the polymer.

[0309] (3) The device according to (1) or (2), wherein at least a portion of the void is exposed on the surface of the electrode material.

[0310] (4) The device according to any one of (1) to (3), wherein at least a portion of the interferent blocking agent is in contact with the electrode material.

[0311] (5) The device of any one of (1) to (4), wherein the interferent blocking agent fills at least about 80% of the voids within the polymer to limit access of interferents to the electrode material.

[0312] (6) The device according to any one of (1) to (5), wherein the biorecognition element is within a polymer.

[0313] (7) The device according to (6), wherein the biorecognition element is physically entrapped within the polymer.

[0314] (8) The device according to any one of (1) to (7), wherein the biorecognition element is glucose oxidase, glucose dehydrogenase, 3-hydroxybutyrate dehydrogenase, or lactate dehydrogenase.

[0315] (9) The device according to any one of (1) to (8), wherein the polymer comprises one or more of aniline, acetylene, phenylene, phenylene vinylene, phenylenediamine, thiophene, 3,4-ethylenedioxythiophene, and aminophenylboronic acid.

[0316] (10) The device according to any one of (1) to (9), wherein the diffusion-limiting layer is hydrophobic.

[0317] (11) The device according to any one of (1) to (10), wherein the diffusion-limiting layer comprises one or more of polydimethylsiloxane, polyurethane, polyvinyl chloride, polyvinylpyrrolidone, polycarbonate, polyethylene, polyethylene terephthalate, polyester, high-density polyethylene, low-density polyethylene, and polytetrafluoroethylene.

[0318] (12) The device according to any one of (1) to (11), wherein the analyte includes one or more of glucose, ketone, and lactate.

[0319] (13) The device according to any one of (1) to (12), wherein the interferent blocking agent is a non-conductive polymer.

[0320] (14) The device according to any one of (1) to (13), wherein the interferent blocking agent comprises one or more of resorcinol, hydroquinone quinol, 2-amino-4,6-dinitrophenol picramic acid, 3,5-dihydroxytoluene orcinol, 2,4,6-trinitroresorcinol styphnic acid, 2-hydroxyphenol catechol, 9-phenanthrol, pyrogallol, α-naphthol, anisole, phenetole, picric acid, and phenol.

[0321] (15) The device of (14), wherein the interferent blocking agent comprises phenol.

[0322] (16) The device according to (15), wherein phenol is present in the biorecognition layer at a concentration of about 0.1 mg / mL or 0.01% w / v to about 10 mg / mL or 1% w / v.

[0323] (17) The device according to (15) or (16), wherein the polymerized phenol is trapped within the voids of the polymer.

[0324] (18) The device according to any one of (1) to (17), wherein the electrode material comprises platinum, palladium, iridium, rhodium, gold, ruthenium, titanium, nickel, carbon, doped diamond, or a combination thereof.

[0325] (19) The device according to any one of (1) to (18), wherein the interference current in the electrode material of the device changes by less than 70% over a period of one week.

[0326] (20) The device according to any one of (1) to (19), wherein the interference current in the electrode material of the device changes by less than 10% over a period of one week.

[0327] (21) A method of manufacturing a device for use in sensing an analyte, the method comprising: depositing a biorecognition element and a polymer on an electrode material disposed on a microneedle, the biorecognition element being configured to react with an analyte; applying an interferent blocking agent to the polymer after deposition, thereby filling voids within the polymer with the interferent blocking agent; and depositing a diffusion-limiting layer on the polymer.

[0328] (22) The method according to (21), wherein the voids in the polymer extend in the thickness direction of the polymer.

[0329] (23) The method according to (22), wherein at least a portion of the voids is exposed on the surface of the electrode material.

[0330] (24) The method according to any one of (21) to (23), wherein the interferent blocking agent fills at least about 80% of the voids in the polymer to limit access of interferents to the electrode material.

[0331] (25) The method according to any one of (21) to (24), wherein the biorecognition element is glucose oxidase, glucose dehydrogenase, 3-hydroxybutyrate dehydrogenase, or lactate dehydrogenase.

[0332] (26) The method according to any one of (21) to (25), wherein the polymer comprises one or more of aniline, acetylene, phenylene, phenylene vinylene, phenylenediamine, thiophene, 3,4-ethylenedioxythiophene, and aminophenylboronic acid.

[0333] (27) The method according to any one of (21) to (26), wherein the diffusion-limiting layer comprises one or more of polydimethylsiloxane, polyurethane, polyvinyl chloride, polyvinylpyrrolidone, polycarbonate, polyethylene, polyethylene terephthalate, polyester, high-density polyethylene, low-density polyethylene, and polytetrafluoroethylene.

[0334] (28) The method according to any one of (21) to (27), wherein applying comprises electropolymerizing the interferent blocking agent.

[0335] (29) The method according to any one of (21) to (28), wherein the interferent blocker comprises one or more of resorcinol, hydroquinone quinol, 2-amino-4,6-dinitrophenol picramic acid, 3,5-dihydroxytoluene orcinol, 2,4,6-trinitroresorcinol styphnic acid, 2-hydroxyphenol catechol, 9-phenanthrol, pyrogallol, α-naphthol, anisole, phenetole, picric acid, and phenol.

[0336] (30) The method according to any one of (21) to (29), wherein the interferent blocking agent comprises phenol.

[0337] (31) The method according to (30), wherein the phenol is applied as a mixture having a concentration of about 0.01 mM phenol to about 100 mM phenol.

[0338] (32) The method according to any one of (21) to (31), wherein at least a portion of the interferent blocking agent is in contact with the electrode material.

[0339] (33) The method according to any one of (21) to (32), wherein the interference current in the electrode material of the device changes by less than 10% over a period of one week.

[0340] (34) A device for use in sensing an analyte, the device comprising: a microneedle; an electrode material on the microneedle; a biorecognition layer on the electrode material, the biorecognition layer including a polymer, a biorecognition element configured to react with the analyte, and an interferent blocking agent filling voids in the polymer; a diffusion-limiting layer; and an adhesion enhancer configured to reduce variability in analyte sensing, the adhesion enhancer being positioned between the biorecognition layer and the diffusion-limiting layer.

[0341] (35) The device according to (34), wherein the voids in the polymer run through the thickness of the polymer.

[0342] (36) The device according to (35), wherein at least a portion of the void is exposed to the surface of the electrode material.

[0343] (37) The device according to any one of (34) to (36), wherein the interferent blocking agent fills at least about 80% of the voids in the polymer to limit access of interferents to the electrode material.

[0344] (38) The device according to any one of (34) to (37), wherein the biorecognition element is within a polymer.

[0345] (39) The device according to (38), wherein the biorecognition element is physically entrapped within the polymer.

[0346] (40) The device according to any one of (34) to (39), wherein the biorecognition element is glucose oxidase, glucose dehydrogenase, 3-hydroxybutyrate dehydrogenase, or lactate dehydrogenase.

[0347] (41) The device according to any one of (34) to (40), wherein the polymer comprises one or more of aniline, acetylene, phenylene, phenylene vinylene, phenylenediamine, thiophene, 3,4-ethylenedioxythiophene, and aminophenylboronic acid.

[0348] (42) The device according to any one of (34) to (41), wherein the diffusion-limiting layer is hydrophobic.

[0349] (43) The device described in any one of (34) to (42), wherein the diffusion-limiting layer comprises one or more of polydimethylsiloxane, polyurethane, polyvinyl chloride, polyvinylpyrrolidone, polycarbonate, polyethylene, polyethylene terephthalate, polyester, high-density polyethylene, low-density polyethylene, and polytetrafluoroethylene.

[0350] (44) The device according to any one of (34) to (43), wherein the analyte includes one or more of glucose, ketone, and lactate.

[0351] (45) The device according to any one of (34) to (44), wherein the interferent blocking agent is a non-conductive polymer.

[0352] (46) The device according to any one of (34) to (45), wherein the interferent blocking agent comprises at least one agent selected from the group consisting of resorcinol, hydroquinone quinol, 2-amino-4,6-dinitrophenol picramic acid, 3,5-dihydroxytoluene orcinol, 2,4,6-trinitroresorcinol styphnic acid, 2-hydroxyphenol catechol, 9-phenanthrol, pyrogallol, α-naphthol, anisole, phenetole, picric acid, and phenol.

[0353] (47) The device according to any one of (34) to (46), wherein the interferent blocking agent comprises phenol.

[0354] (48) The device according to (47), wherein phenol is present in the biorecognition layer at a concentration of about 0.1 mg / mL or 0.01% w / v to about 10 mg / mL or 1% w / v.

[0355] (49) The device according to (47), wherein the polymerized phenol is trapped within the voids of the polymer.

[0356] (50) The device according to any one of (34) to (49), wherein the electrode material comprises platinum, palladium, iridium, rhodium, gold, ruthenium, titanium, nickel, carbon, doped diamond, or a combination thereof.

[0357] (51) The device according to any one of (34) to (50), wherein the adhesion enhancer comprises a plurality of molecules, and a first end of each of the plurality of molecules is covalently bonded to the biorecognition layer.

[0358] (52) The device described in any one of (34) to (51), wherein the adhesion enhancer comprises a plurality of molecules, and the second end of each of the plurality of molecules is partially immobilized within the diffusion-limiting layer.

[0359] (53) The device according to (52), wherein the second end comprises at least one hydroxyl group.

[0360] (54) The device according to (53), wherein at least one hydroxyl group forms a hydrogen bond with the diffusion-limiting layer.

[0361] (55) The device according to (52), wherein the second end interacts with the diffusion-limiting layer via van der Waals forces.

[0362] (56) The device according to (51) or (52), wherein each of the plurality of molecules is a cross-linking agent.

[0363] (57) The device according to (56), wherein the cross-linking agent comprises an epoxide functional group.

[0364] (58) The device according to (57), wherein the cross-linking agent comprises N(1, 2, 3, 4) epoxide functional groups connected to a linker.

[0365] (59) The device according to (58), wherein the linker is selected from the group consisting of aromatic, aliphatic, straight-chain, and branched-chain.

[0366] (60) The device of (56), wherein the cross-linking agent comprises one selected from the group consisting of 1,4-butanediol diglycidyl ether, 1,6-hexanediol diglycidyl ether, neopentyl glycol diglycidyl ether, poly(propylene glycol) diglycidyl ether, trimethylolethane diglycidyl ether, trimethylolethane triglycidyl ether, diglycidyl resorcinol ether, diglycidyl ether, 1,4-cyclohexanedimethanol diglycidyl ether, castor oil glycidyl ether, and bisphenol A diglycidyl ether.

[0367] (61) The microneedle according to (56), wherein the crosslinking agent is selected from the group consisting of glutaraldehyde, poly(dimethylsiloxane)-diglycidyl ether, tetracyclooxypropyl-4,4-diaminodiphenylmethane, polyethylene glycol diglycidyl ether, and 4-(2,3-epoxypropoxy)-N,N-bis(2,3-epoxypropyl)aniline.

[0368] (62) The device according to any one of (34) to (61), wherein the adhesion enhancer is covalently bound to the biorecognition element.

[0369] (63) The device according to any one of (34) to (62), wherein the biorecognition element is glucose oxidase and the adhesion enhancer is covalently bound to the glucose oxidase.

[0370] (64) The device according to any one of (34) to (63), wherein the polymer comprises one or more of aniline, acetylene, phenylene, phenylene vinylene, phenylenediamine, thiophene, 3,4-ethylenedioxythiophene, and aminophenylboronic acid.

[0371] (65) The device according to any one of (34) to (64), wherein at least a portion of the interferent blocking agent is in contact with the electrode material.

[0372] (66) A device according to any one of (34) to (65), wherein the interference current in the electrode material of the device changes by less than 10% over a period of one week.

[0373] (67) A method of manufacturing a device for use in sensing an analyte, the method comprising: depositing a biorecognition element and a polymer on an electrode material disposed on a microneedle, the biorecognition element being configured to react with an analyte; applying an interferent blocking agent to the polymer, thereby filling voids within the polymer with the interferent blocking agent; exposing the polymer to an adhesion enhancing agent; and depositing a diffusion-limiting layer on the biorecognition layer after exposing the polymer to the adhesion enhancing agent.

[0374] (68) The method according to (67), wherein the voids in the polymer extend in the thickness direction of the polymer.

[0375] (69) The method according to (68), wherein at least a portion of the voids is exposed at the surface of the electrode material.

[0376] (70) The method according to any one of (67) to (69), wherein the interferent blocking agent occupies at least about 80% of the void space within the polymer to limit access of interferents to the electrode material.

[0377] (71) The method according to any one of (67) to (70), wherein the biorecognition element is glucose oxidase, glucose dehydrogenase, 3-hydroxybutyrate dehydrogenase, or lactate dehydrogenase.

[0378] (72) The method according to any one of (67) to (71), wherein the polymer comprises one or more of aniline, acetylene, phenylene, phenylene vinylene, phenylenediamine, thiophene, 3,4-ethylenedioxythiophene, and aminophenylboronic acid.

[0379] (73) The method according to any one of (67) to (72), wherein the diffusion-limiting layer is hydrophobic.

[0380] (74) The method according to any one of (67) to (73), wherein the diffusion-limiting layer is one or more of polydimethylsiloxane, polyurethane, polyvinyl chloride, polyvinylpyrrolidone, polycarbonate, polyethylene, polyethylene terephthalate, polyester, high-density polyethylene, low-density polyethylene, and polytetrafluoroethylene.

[0381] (75) The method according to any one of (67) to (74), wherein applying comprises electropolymerizing the interferent blocking agent.

[0382] (76) The method according to any one of (67) to (75), wherein the interferent blocker comprises one or more of resorcinol, hydroquinone quinol, 2-amino-4,6-dinitrophenol picramic acid, 3,5-dihydroxytoluene orcinol, 2,4,6-trinitroresorcinol styphnic acid, 2-hydroxyphenol catechol, 9-phenanthrol, pyrogallol, α-naphthol, anisole, phenetole, picric acid, and phenol.

[0383] (77) The method according to any one of (67) to (76), wherein the interferent blocking agent comprises phenol.

[0384] (78) The method according to (77), wherein the phenol is applied as a mixture having a concentration of about 0.01 mM phenol to about 100 mM phenol.

[0385] (79) The method according to any one of (67) to (78), wherein the electrode material comprises platinum, palladium, iridium, rhodium, gold, ruthenium, titanium, nickel, carbon, doped diamond, or a combination thereof.

[0386] (80) The method according to any one of (67) to (79), wherein the adhesion enhancer comprises a plurality of molecules, and during exposure, a first end of each of the plurality of molecules covalently binds to the biorecognition layer.

[0387] (81) The method according to any one of (67) to (80), wherein the adhesion enhancer comprises a plurality of molecules, and during exposure, the second end of each of the plurality of molecules is partially immobilized within the diffusion-limiting layer.

[0388] (82) The method according to (81), wherein the second end comprises at least one hydroxyl group.

[0389] (83) The method according to (82), wherein at least one hydroxyl group forms a hydrogen bond with the diffusion-limiting layer.

[0390] (84) The method according to (81), wherein the second end interacts with the diffusion-limiting layer via van der Waals forces.

[0391] (85) The method according to (80) or (81), wherein each of the plurality of molecules is a cross-linking agent.

[0392] (86) The method according to (85), wherein the crosslinking agent contains an epoxide functional group.

[0393] (87) The method according to (85) or (86), wherein the crosslinker comprises N(1, 2, 3, 4) epoxide functional groups connected to a linker.

[0394] (88) The method according to any one of (85) to (87), wherein the linker is selected from the group consisting of aromatic, aliphatic, straight-chain, and branched-chain.

[0395] (89) The method according to any one of (85) to (88), wherein the crosslinking agent comprises one selected from the group consisting of 1,4-butanediol diglycidyl ether, 1,6-hexanediol diglycidyl ether, neopentyl glycol diglycidyl ether, poly(propylene glycol) diglycidyl ether, trimethylolethane diglycidyl ether, trimethylolethane triglycidyl ether, diglycidyl resorcinol ether, diglycidyl ether, 1,4-cyclohexanedimethanol diglycidyl ether, castor oil glycidyl ether, and bisphenol A diglycidyl ether.

[0396] (90) The method according to any one of (85) to (89), wherein the crosslinking agent comprises one selected from the group consisting of glutaraldehyde, poly(dimethylsiloxane)-diglycidyl ether, tetracyclooxypropyl-4,4-diaminodiphenylmethane, polyethylene glycol diglycidyl ether, and 4-(2,3-epoxypropoxy)-N,N-bis(2,3-epoxypropyl)aniline.

[0397] (91) The method according to any one of (67) to (90), wherein the adhesion enhancer is covalently bound to the biorecognition element.

[0398] (92) The method according to any one of (67) to (91), wherein the biorecognition element is glucose oxidase and the adhesion enhancer is covalently bound to the glucose oxidase.

[0399] (93) The method according to any one of (67) to (92), wherein exposing the polymer to the adhesion promoter comprises one or more of drop casting, spray coating, dipping, spin coating, and chemical vapor deposition.

[0400] (94) The method according to any one of (67) to (93), wherein exposing the polymer to the adhesion promoter comprises immersing the polymer in a buffer solution containing the adhesion promoter.

[0401] (95) The method according to (94), wherein the buffer solution has a pH of about 7 to about 10.

[0402] (96) The method according to (94) or (95), wherein the immersion is carried out for a period of about 5 minutes to about 3 days.

[0403] (97) The method according to any one of (94) to (96), wherein the immersion is carried out for a period of more than about 16 hours.

[0404] (98) The method according to any one of (94) to (97), wherein the adhesion enhancer comprises a crosslinking agent, and the concentration of the crosslinking agent in the buffer solution is about 0.1% to about 20% w / w or w / v.

[0405] (99) A device for use in sensing an analyte, comprising: a microneedle; an electrode material on the microneedle; and a biorecognition layer on the electrode material, the biorecognition layer comprising a polymer, a biorecognition element configured to react with the analyte, and an interferent blocker filling voids within the polymer.

[0406] (100) A device for use in sensing an analyte, the device comprising: a microneedle; an electrode material on the microneedle; a biorecognition layer on the electrode material, the biorecognition layer comprising a phenylenediamine, a biorecognition element, and a polyphenol, the polyphenol filling voids in the phenylenediamine, and the biorecognition element configured to react with an analyte; and a polyurethane-based diffusion-limiting layer on the biorecognition layer.

[0407] (101) A method for manufacturing a device for use in sensing an analyte, the method comprising: depositing a biorecognition element and a polymer on an electrode material disposed on a microneedle, the biorecognition element being configured to react with an analyte; and applying an interferent blocking agent to the polymer after deposition, thereby filling voids within the polymer with the interferent blocking agent.

[0408] (102) A method for manufacturing a device for use in sensing an analyte, the method comprising: depositing a biorecognition element and a phenylenediamine on an electrode material disposed on a microneedle, the biorecognition element being configured to react with an analyte; applying a polyphenol to the phenylenediamine after deposition, thereby filling voids within the phenylenediamine with the polyphenol; and depositing a polyurethane-based diffusion-limiting layer on the phenylenediamine.

[0409] (103) A device for use in sensing an analyte, comprising: a microneedle; an electrode material on the microneedle; a biorecognition layer on the electrode material, the biorecognition layer comprising a phenylenediamine, a biorecognition element configured to react with an analyte, and a polyphenol filling voids in the phenylenediamine; a polyurethane-based diffusion-limiting layer; and an adhesion enhancer configured to reduce variability in analyte sensing, the adhesion enhancer comprising 1,4-butanediol diglycidyl ether, positioned between the biorecognition layer and the polyurethane-based diffusion-limiting layer.

[0410] (104) A method for manufacturing a device for use in sensing an analyte, the method comprising: depositing a biorecognition element and a phenylenediamine on an electrode material disposed on a microneedle, the biorecognition element being configured to react with an analyte; applying a polyphenol to the phenylenediamine, thereby filling voids within the phenylenediamine with the polyphenol; exposing the phenylenediamine to an adhesion enhancer comprising 1,4-butanediol diglycidyl ether; and depositing a polyurethane-based diffusion-limiting layer on the biorecognition layer after exposing the phenylenediamine to the 1,4-butanediol diglycidyl ether.

[0411] (105) An analyte monitoring device comprising a plurality of microneedles arranged in an array, the microneedles comprising a plurality of working electrodes, a reference electrode, and a counter electrode, the plurality of working electrodes being disposed between the reference electrode and the counter electrode.

[0412] (106) The analyte monitoring device of (105), wherein the plurality of working electrodes are uniformly spaced from the reference electrode.

[0413] (107) The analyte monitoring device of either (105) or (106), wherein the plurality of working electrodes are connected to a counter electrode such that a current flows from each of the plurality of working electrodes to the counter electrode.

[0414] (108) The analyte monitoring device of (107), wherein the current results from a potential applied between a plurality of working electrodes and a reference electrode.

[0415] (109) An analyte monitoring device according to any one of (105) to (108), wherein the plurality of microneedles includes a plurality of counter electrodes, and the plurality of working electrodes is disposed between a reference electrode and the plurality of counter electrodes.

[0416] (110) The analyte monitoring device of (109), wherein the plurality of counter electrodes are electrically connected in parallel, and each of the plurality of working electrodes is connected to a plurality of counter electrodes.

[0417] (111) The analyte monitoring device of (110), wherein the plurality of counter electrodes are connected in parallel with each other.

[0418] (112) The analyte monitoring device of (110), wherein a majority of the current from a first working electrode of the plurality of working electrodes flows to a first counter electrode of the plurality of counter electrodes, the first counter electrode being positioned closest to the first working electrode relative to the other counter electrodes.

[0419] (113) The analyte monitoring device of (112), wherein the current results from a potential applied between the first working electrode and the reference electrode.

[0420] (114) The analyte monitoring device of (109), wherein the number of the plurality of working electrodes is equal to the number of the plurality of counter electrodes.

[0421] (115) The analyte monitoring device of (109), wherein the plurality of working electrodes includes three working electrodes and the plurality of counter electrodes includes three counter electrodes.

[0422] (116) The analyte monitoring device of (115), wherein the three working electrodes form a barrier around the reference electrode.

[0423] (117) The analyte monitoring device of (116), wherein the barrier prevents current flowing from the multiple working electrodes to the multiple counter electrodes from flowing through the reference electrode.

[0424] (118) An analyte monitoring device according to any one of (105) to (118), wherein the number of the plurality of working electrodes includes at least a minimum number required to isolate the reference electrode from the current flowing between the plurality of working electrodes and the counter electrode.

[0425] (119) An analyte monitoring device according to any one of (105) to (119), wherein each of the plurality of working electrodes is disposed on the surface of a tapered distal portion of each of the plurality of microneedles.

[0426] (120) The analyte monitoring device of (119), wherein each of the plurality of working electrodes includes a biorecognition layer, the biorecognition layer including a biorecognition element configured to react with an analyte.

[0427] (121) The analyte monitoring device of any one of (105) to (120), further comprising a semiconductor substrate, wherein the plurality of microneedles extend from the semiconductor substrate.

[0428] (122) An analyte monitoring device as described in (121), wherein each working electrode of the plurality of working electrodes is disposed on a respective microneedle of the plurality of microneedles, and the first microneedle including the first working electrode is disposed in a central region of the semiconductor substrate.

[0429] (123) The analyte monitoring device of (122), wherein a counter electrode is disposed on a second microneedle of the plurality of microneedles, the second microneedle being proximate to a first edge of the semiconductor substrate.

[0430] (124) The analyte monitoring device of (123), wherein the reference electrode is disposed on a third microneedle of the plurality of microneedles, the third microneedle being proximate to a second edge of the semiconductor substrate, the second edge being opposite the first edge.

[0431] (125) The analyte monitoring device of (124), wherein the plurality of microneedles includes a plurality of counter electrodes, each counter electrode being disposed on a respective microneedle of the plurality of microneedles, each proximate a first edge of the semiconductor substrate.

[0432] (126) The analyte monitoring device of (121), wherein the reference electrode is disposed on a central microneedle of the plurality of microneedles, the central microneedle being positioned in a central region of the semiconductor substrate, and the plurality of working electrodes surround the reference electrode.

[0433] (127) The analyte monitoring device of (126), wherein a counter electrode is disposed on each microneedle of the plurality of microneedles, each microneedle being proximate to a first edge of the semiconductor substrate.

[0434] (128) The analyte monitoring device of (127), wherein the plurality of microneedles includes a plurality of counter electrodes proximate the outer edge of the semiconductor substrate.

[0435] (129) A microneedle array for use in sensing an analyte, comprising: a plurality of sensing microneedles, each comprising a working electrode with a biorecognition layer, the biorecognition layer comprising a biorecognition element configured to react with an analyte; a first microneedle comprising a counter electrode; and a second microneedle comprising a reference electrode, wherein the plurality of sensing microneedles are connected to the first microneedle such that a current flows between the plurality of sensing microneedles and the first microneedle, the current resulting from a potential applied between the plurality of sensing microneedles and the second microneedle, and the plurality of sensing microneedles are positioned between the first microneedle and the second microneedle.

[0436] (130) A device for use in sensing an analyte, comprising: a microneedle; an electrode material on the microneedle; a biorecognition layer on the electrode material, the biorecognition layer comprising a polymer, a biorecognition element configured to react with the analyte, and an interferent blocking agent filling voids in the polymer, at least a portion of the interferent blocking agent being in contact with the electrode material; and a diffusion-limiting layer on the biorecognition layer.

[0437] (131) The device according to (130), wherein the interferent blocking agent is a non-conductive polymer.

[0438] (132) The method of either (130) or (131), wherein the interferent blocker comprises one or more of resorcinol, hydroquinone quinol, 2-amino-4,6-dinitrophenol picramic acid, 3,5-dihydroxytoluene orcinol, 2,4,6-trinitroresorcinol styphnic acid, 2-hydroxyphenol catechol, 9-phenanthrol, pyrogallol, α-naphthol, anisole, phenetole, picric acid, and phenol.

[0439] (133) The device according to (132), wherein the interferent blocking agent comprises phenol.

[0440] (134) The device according to (133), wherein phenol is present in the biorecognition layer at a concentration of about 0.1 mg / mL or 0.01% w / v to about 10 mg / mL or 1% w / v.

[0441] (135) The device according to either (133) or (134), wherein the polymerized phenol is trapped within the voids of the polymer.

[0442] (136) Any one of the devices (130) to (135), wherein the interference current in the electrode material of the device changes by less than 70% over a period of one week.

[0443] (137) The device according to any one of (130) to (136), wherein the biorecognition element is physically entrapped within the polymer.

[0444] (138) The device according to any one of (130) to (137), wherein the polymer comprises one or more of aniline, acetylene, phenylene, phenylene vinylene, phenylenediamine, thiophene, 3,4-ethylenedioxythiophene, and aminophenylboronic acid.

[0445] (139) A device for use in sensing an analyte, comprising: a microneedle; an electrode material on the microneedle; a biorecognition layer on the electrode material, the biorecognition layer comprising a polymer, a biorecognition element configured to react with the analyte, and an interferent blocking agent filling voids within the polymer, the voids within the polymer running through a thickness of the polymer; and a diffusion-limiting layer on the biorecognition layer.

[0446] (140) The device of (139), wherein the interferent blocker comprises one or more of resorcinol, hydroquinone quinol, 2-amino-4,6-dinitrophenol picramic acid, 3,5-dihydroxytoluene orcinol, 2,4,6-trinitroresorcinol styphnic acid, 2-hydroxyphenol catechol, 9-phenanthrol, pyrogallol, α-naphthol, anisole, phenetole, picric acid, and phenol.

[0447] (141) The device according to (140), wherein the interferent blocking agent comprises phenol.

[0448] (142) The device according to (141), wherein phenol is present in the biorecognition layer at a concentration of about 0.1 mg / mL or 0.01% w / v to about 10 mg / mL or 1% w / v.

[0449] (143) The device according to either (141) or (142), wherein the polymerized phenol is trapped within the voids of the polymer.

[0450] (144) Any one of (139) to (143) devices, wherein the interference current in the electrode material of the device changes by less than 10% over a period of one week.

[0451] (145) The device according to any one of (139) to (144), wherein at least a portion of the void is exposed to the surface of the electrode material.

[0452] (146) A device described in any one of (139) to (145), wherein the interferent blocking agent fills at least about 80% of the voids in the polymer to restrict access of interferents to the electrode material.

[0453] (147) The device according to any one of (139) to (146), wherein the polymer comprises one or more of aniline, acetylene, phenylene, phenylene vinylene, phenylenediamine, thiophene, 3,4-ethylenedioxythiophene, and aminophenylboronic acid.

[0454] (148) A device described in any one of (139) to (147), wherein the diffusion-limiting layer comprises one or more of polydimethylsiloxane, polyurethane, polyvinyl chloride, polyvinylpyrrolidone, polycarbonate, polyethylene, polyethylene terephthalate, polyester, high-density polyethylene, low-density polyethylene, and polytetrafluoroethylene.

[0455] (149) A device for use in sensing an analyte, comprising: a microneedle; a working electrode on the microneedle, the working electrode comprising an electrode material on the microneedle; and a biorecognition layer on the electrode material, the biorecognition layer comprising a polymer, a biorecognition element configured to react with the analyte, and an interferent blocker filling voids within the polymer.

[0456] (150) The device according to (149), wherein the interferent blocking agent limits access of interferents to the electrode material.

[0457] (151) The device of either (149) or (150), wherein the interferent blocker comprises one or more of resorcinol, hydroquinone quinol, 2-amino-4,6-dinitrophenol picramic acid, 3,5-dihydroxytoluene orcinol, 2,4,6-trinitroresorcinol styphnic acid, 2-hydroxyphenol catechol, 9-phenanthrol, pyrogallol, α-naphthol, anisole, phenetole, picric acid, and phenol.

[0458] (152) The device according to (151), wherein the interferent blocking agent comprises phenol.

[0459] (153) The device according to (152), wherein the polymerized phenol is trapped within the voids of the polymer.

[0460] (154) Any one of (149) to (153) devices, wherein the interference current in the electrode material of the device changes by less than 70% over a period of one week.

[0461] (155) The device described in any one of (149) to (154), wherein the device further comprises a microneedle array including a first plurality of microneedles each comprising a working electrode, the first plurality of microneedles comprising a microneedle, the microneedle array further comprising a second microneedle comprising a reference electrode and a third microneedle comprising a counter electrode, the microneedle array further comprising a second plurality of microneedles each comprising a counter electrode, the second plurality of microneedles comprising the third microneedle, and the first plurality of microneedles are disposed between the second microneedles and the second plurality of microneedles.

[0462] (156) The device described in any one of (149) to (155), wherein the device further comprises a microneedle array including a first plurality of microneedles each comprising a working electrode, the first plurality of microneedles comprising a microneedle, the microneedle array further comprising a second microneedle comprising a reference electrode and a third microneedle comprising a counter electrode, each of the working electrodes being electrically connected to the counter electrode such that current flows from each of the working electrodes to the counter electrode.

[0463] (157) The device of any one of (149) to (156), further comprising a microneedle array including a first plurality of microneedles each comprising a working electrode, the first plurality of microneedles comprising a microneedle, the microneedle array further comprising a second microneedle comprising a reference electrode, a third microneedle comprising a counter electrode, and a second plurality of microneedles each comprising a counter electrode, the second plurality of microneedles comprising the third microneedle, each of the counter electrodes being electrically connected to the working electrode, a majority of the current from a first of the working electrodes flowing to a first of the counter electrodes, the first counter electrode being positioned closest to the first working electrode relative to any other counter electrodes.

[0464] (158) The device according to (157), wherein the working electrode includes three working electrodes and the counter electrode includes three counter electrodes, and the three working electrodes form a barrier separating the reference electrode from the three counter electrodes.

[0465] (159) A method for manufacturing a device for use in sensing an analyte, the method comprising: depositing a biorecognition element and a polymer on an electrode material disposed on a microneedle, the biorecognition element being configured to react with an analyte; applying an interferent blocking agent to the polymer after deposition, thereby filling voids within the polymer with the interferent blocking agent; and depositing a diffusion-limiting layer on the polymer.

Claims

1. 1. A device for use in sensing an analyte, comprising: Microneedles and an electrode material on the microneedle; a biorecognition layer on the electrode material, the biorecognition layer comprising a polymer, a biorecognition element configured to react with the analyte, and an interferent blocker filling voids within the polymer; a diffusion-limiting layer; an adhesion enhancer configured to reduce variability in analyte sensing, the adhesion enhancer being positioned between the biorecognition layer and the diffusion-limiting layer.

2. The device of claim 1 , wherein the voids in the polymer run through the thickness of the polymer.

3. The device of claim 2 , wherein at least a portion of the void is exposed at a surface of the electrode material.

4. 10. The device of claim 1, wherein the interferent blocking agent fills at least about 80% of the voids in the polymer to prevent interferents from accessing the electrode material.

5. The device of claim 1 , wherein the biorecognition element is within the polymer.

6. The device of claim 5 , wherein the biorecognition element is physically entrapped within the polymer.

7. 10. The device of claim 1, wherein the biorecognition element is glucose oxidase, glucose dehydrogenase, 3-hydroxybutyrate dehydrogenase, or lactate dehydrogenase.

8. 10. The device of claim 1, wherein the polymer comprises one or more of aniline, acetylene, phenylene, phenylene vinylene, phenylenediamine, thiophene, 3,4-ethylenedioxythiophene, and aminophenylboronic acid.

9. The device of claim 1 , wherein the diffusion-limiting layer is hydrophobic.

10. 10. The device of claim 1, wherein the diffusion-limiting layer comprises one or more of polydimethylsiloxane, polyurethane, polyvinyl chloride, polyvinylpyrrolidone, polycarbonate, polyethylene, polyethylene terephthalate, polyester, high density polyethylene, low density polyethylene, and polytetrafluoroethylene.

11. The device of claim 1 , wherein the analytes include one or more of glucose, ketones, and lactate.

12. The device of claim 1 , wherein the interferent blocking agent is a non-conductive polymer.

13. 10. The device of claim 1, wherein the interferent blocker comprises at least one agent selected from the group consisting of resorcinol, hydroquinone quinol, 2-amino-4,6-dinitrophenol picramic acid, 3,5-dihydroxytoluene orcinol, 2,4,6-trinitroresorcinol styphnic acid, 2-hydroxyphenol catechol, 9-phenanthrol, pyrogallol, α-naphthol, anisole, phenetole, picric acid, and phenol.

14. 10. The device of claim 1, wherein the interferent blocker comprises phenol.

15. 15. The device of claim 14, wherein the phenol is present in the biorecognition layer at a concentration of about 0.1 mg / mL or 0.01% w / v to about 10 mg / mL or 1% w / v.

16. 15. The device of claim 14, wherein polymerized phenol is trapped within the voids of the polymer.

17. 10. The device of claim 1, wherein the electrode material comprises platinum, palladium, iridium, rhodium, gold, ruthenium, titanium, nickel, carbon, doped diamond, or a combination thereof.

18. The device of claim 1 , wherein the adhesion enhancer comprises a plurality of molecules, a first end of each of the plurality of molecules being covalently attached to the biorecognition layer.

19. The device of claim 1 , wherein the adhesion enhancing agent comprises a plurality of molecules, the second end of each of the plurality of molecules being partially immobilized within the diffusion-limiting layer.

20. 20. The device of claim 19, wherein the second end comprises at least one hydroxyl group.

21. 21. The device of claim 20, wherein the at least one hydroxyl group forms a hydrogen bond with the diffusion-limiting layer.

22. 20. The device of claim 19, wherein the second end interacts with the diffusion-limiting layer via van der Waals forces.

23. 20. The device of claim 18 or 19, wherein each of the plurality of molecules is a cross-linking agent.

24. 24. The device of claim 23, wherein the cross-linking agent comprises an epoxide functional group.

25. 25. The device of claim 24, wherein the cross-linking agent comprises N(1, 2, 3, 4) epoxide functional groups connected to a linker.

26. 26. The device of claim 25, wherein the linker is selected from the group consisting of aromatic, aliphatic, straight chain, and branched chain.

27. 24. The device of claim 23, wherein the cross-linking agent comprises one selected from the group consisting of 1,4-butanediol diglycidyl ether, 1,6-hexanediol diglycidyl ether, neopentyl glycol diglycidyl ether, poly(propylene glycol) diglycidyl ether, trimethylolethane diglycidyl ether, trimethylolethane triglycidyl ether, diglycidyl resorcinol ether, diglycidyl ether, 1,4-cyclohexanedimethanol diglycidyl ether, castor oil glycidyl ether, and bisphenol A diglycidyl ether.

28. 24. The device of claim 23, wherein the cross-linking agent comprises a member selected from the group consisting of glutaraldehyde, poly(dimethylsiloxane)-diglycidyl ether, tetracyclooxypropyl-4,4-diaminodiphenylmethane, polyethylene glycol diglycidyl ether, and 4-(2,3-epoxypropoxy)-N,N-bis(2,3-epoxypropyl)aniline.

29. The device of claim 1 , wherein the adhesion enhancer is covalently bound to the biorecognition element.

30. 10. The device of claim 1, wherein the biorecognition element is glucose oxidase and the adhesion enhancer is covalently bound to the glucose oxidase.

31. 10. The device of claim 1, wherein the polymer comprises one or more of aniline, acetylene, phenylene, phenylene vinylene, phenylenediamine, thiophene, 3,4-ethylenedioxythiophene, and aminophenylboronic acid.

32. The device of claim 1 , wherein at least a portion of the interferent blocking agent is in contact with the electrode material.

33. 10. The device of claim 1, wherein the interference current in the electrode material of the device changes by less than 10% over a period of one week.

34. 1. A method of manufacturing a device for use in sensing an analyte, comprising: depositing a biorecognition element and a polymer on an electrode material disposed on the microneedle, the biorecognition element configured to react with the analyte; applying an interferent blocking agent to the polymer, thereby filling voids within the polymer with the interferent blocking agent; exposing the polymer to an adhesion enhancer; depositing a diffusion-limiting layer over the biorecognition layer after exposing the polymer to the adhesion-enhancing agent.

35. 35. The method of claim 34, wherein the voids in the polymer run through the thickness of the polymer.

36. 36. The method of claim 35, wherein at least a portion of the voids are exposed at a surface of the electrode material.

37. 35. The method of claim 34, wherein the interferent blocking agent occupies at least about 80% of the voids within the polymer to prevent interferents from accessing the electrode material.

38. 35. The method of claim 34, wherein the biorecognition element is glucose oxidase, glucose dehydrogenase, 3-hydroxybutyrate dehydrogenase, or lactate dehydrogenase.

39. 35. The method of claim 34, wherein the polymer comprises one or more of aniline, acetylene, phenylene, phenylene vinylene, phenylenediamine, thiophene, 3,4-ethylenedioxythiophene, and aminophenylboronic acid.

40. 35. The method of claim 34, wherein the diffusion-limiting layer is hydrophobic.

41. 35. The method of claim 34, wherein the diffusion-limiting layer is one or more of polydimethylsiloxane, polyurethane, polyvinyl chloride, polyvinylpyrrolidone, polycarbonate, polyethylene, polyethylene terephthalate, polyester, high density polyethylene, low density polyethylene, and polytetrafluoroethylene.

42. 35. The method of claim 34, wherein said applying comprises electropolymerizing said interferent blocking agent.

43. 35. The method of claim 34, wherein the interferent blocker comprises one or more of resorcinol, hydroquinone quinol, 2-amino-4,6-dinitrophenol picramic acid, 3,5-dihydroxytoluene orcinol, 2,4,6-trinitroresorcinol styphnic acid, 2-hydroxyphenol catechol, 9-phenanthrol, pyrogallol, α-naphthol, anisole, phenetole, picric acid, and phenol.

44. 35. The method of claim 34, wherein the interferent blocker comprises phenol.

45. 45. The method of claim 44, wherein the phenol is applied as a mixture having a concentration of about 0.01 mM phenol to about 100 mM phenol.

46. 35. The method of claim 34, wherein the electrode material comprises platinum, palladium, iridium, rhodium, gold, ruthenium, titanium, nickel, carbon, doped diamond, or a combination thereof.

47. 35. The method of claim 34, wherein the adhesion enhancer comprises a plurality of molecules, and during the exposing, a first end of each of the plurality of molecules covalently binds to the biorecognition layer.

48. 35. The method of claim 34, wherein the adhesion enhancing agent comprises a plurality of molecules, and during the exposing, the second end of each of the plurality of molecules becomes partially immobilized within the diffusion-limiting layer.

49. 49. The method of claim 48, wherein the second end comprises at least one hydroxyl group.

50. 50. The method of claim 49, wherein the at least one hydroxyl group forms a hydrogen bond with the diffusion-limiting layer.

51. 49. The method of claim 48, wherein the second end interacts with the diffusion-limiting layer via van der Waals forces.

52. 49. The method of claim 47 or 48, wherein each of the plurality of molecules is a cross-linking agent.

53. 53. The method of claim 52, wherein the crosslinker comprises an epoxide functional group.

54. 53. The method of claim 52, wherein the cross-linking agent comprises N(1, 2, 3, 4) epoxide functional groups connected to a linker.

55. 53. The method of claim 52, wherein the linker is selected from the group consisting of aromatic, aliphatic, straight chain, and branched chain.

56. 53. The method of claim 52, wherein the crosslinking agent comprises one selected from the group consisting of 1,4-butanediol diglycidyl ether, 1,6-hexanediol diglycidyl ether, neopentyl glycol diglycidyl ether, poly(propylene glycol) diglycidyl ether, trimethylolethane diglycidyl ether, trimethylolethane triglycidyl ether, diglycidyl resorcinol ether, diglycidyl ether, 1,4-cyclohexanedimethanol diglycidyl ether, castor oil glycidyl ether, and bisphenol A diglycidyl ether.

57. 53. The method of claim 52, wherein the cross-linking agent comprises a member selected from the group consisting of glutaraldehyde, poly(dimethylsiloxane)-diglycidyl ether, tetracyclooxypropyl-4,4-diaminodiphenylmethane, polyethylene glycol diglycidyl ether, and 4-(2,3-epoxypropoxy)-N,N-bis(2,3-epoxypropyl)aniline.

58. 35. The method of claim 34, wherein the adhesion enhancer is covalently attached to the biorecognition element.

59. 35. The method of claim 34, wherein the biorecognition element is glucose oxidase and the adhesion enhancer is covalently bound to the glucose oxidase.

60. 35. The method of claim 34, wherein exposing the polymer to the adhesion promoter comprises one or more of drop casting, spray coating, dipping, spin coating, and chemical vapor deposition.

61. 35. The method of claim 34, wherein exposing the polymer to the adhesion-enhancing agent comprises soaking the polymer in a buffer solution containing the adhesion-enhancing agent.

62. 62. The method of claim 61, wherein the buffer solution has a pH of about 7 to about 10.

63. 62. The method of claim 61, wherein the soaking is carried out for a time period of from about 5 minutes to about 3 days.

64. 62. The method of claim 61, wherein the soaking is for a period of greater than about 16 hours.

65. 62. The method of claim 61, wherein the adhesion enhancing agent comprises a cross-linking agent, and the concentration of the cross-linking agent in the buffered solution is from about 0.1% to about 20% w / w or w / v.

66. 1. A device for use in sensing an analyte, comprising: Microneedles and an electrode material on the microneedle; a biorecognition layer on the electrode material, the biorecognition layer comprising a polymer, a biorecognition element configured to react with the analyte, and an interferent blocker filling voids within the polymer; a diffusion-limiting layer on the biorecognition layer.

67. 67. The device of claim 66, wherein the voids in the polymer run through the thickness of the polymer.

68. 68. The device of claim 67, wherein at least a portion of the void is exposed at a surface of the electrode material.

69. 67. The device of claim 66, wherein at least a portion of the interferent blocking agent is in contact with the electrode material.

70. 67. The device of claim 66, wherein the interferent blocking agent fills at least about 80% of the voids in the polymer to prevent interferents from accessing the electrode material.

71. 67. The device of claim 66, wherein the biorecognition element is within the polymer.

72. 72. The device of claim 71, wherein the biorecognition element is physically entrapped within the polymer.

73. 67. The device of claim 66, wherein the biorecognition element is glucose oxidase, glucose dehydrogenase, 3-hydroxybutyrate dehydrogenase, or lactate dehydrogenase.

74. 67. The device of claim 66, wherein the polymer comprises one or more of aniline, acetylene, phenylene, phenylene vinylene, phenylenediamine, thiophene, 3,4-ethylenedioxythiophene, and aminophenylboronic acid.

75. 67. The device of claim 66, wherein the diffusion-limiting layer is hydrophobic.

76. 67. The device of claim 66, wherein the diffusion-limiting layer comprises one or more of polydimethylsiloxane, polyurethane, polyvinyl chloride, polyvinylpyrrolidone, polycarbonate, polyethylene, polyethylene terephthalate, polyester, high density polyethylene, low density polyethylene, and polytetrafluoroethylene.

77. 67. The apparatus of claim 66, wherein the analytes include one or more of glucose, ketones, and lactate.

78. 67. The device of claim 66, wherein the interferent blocking agent is a non-conductive polymer.

79. 67. The device of claim 66, wherein the interferent blocker comprises one or more of resorcinol, hydroquinone quinol, 2-amino-4,6-dinitrophenol picramic acid, 3,5-dihydroxytoluene orcinol, 2,4,6-trinitroresorcinol styphnic acid, 2-hydroxyphenol catechol, 9-phenanthrol, pyrogallol, α-naphthol, anisole, phenetole, picric acid, and phenol.

80. 80. The device of claim 79, wherein the interferent blocker comprises phenol.

81. 81. The device of claim 80, wherein the phenol is present in the biorecognition layer at a concentration of from about 0.1 mg / mL or 0.01% w / v to about 10 mg / mL or 1% w / v.

82. 81. The device of claim 80, wherein polymerized phenol is trapped within the voids of the polymer.

83. 67. The apparatus of claim 66, wherein the electrode material comprises platinum, palladium, iridium, rhodium, gold, ruthenium, titanium, nickel, carbon, doped diamond, or a combination thereof.

84. 67. The device of claim 66, wherein the interference current in the electrode material of the device changes by less than 70% over a period of one week.

85. 67. The device of claim 66, wherein the interference current in the electrode material of the device changes by less than 10% over a period of one week.

86. 1. A method of manufacturing a device for use in sensing an analyte, comprising: depositing a biorecognition element and a polymer on an electrode material disposed on the microneedle, the biorecognition element configured to react with the analyte; applying an interferent blocking agent to the polymer after deposition, thereby filling voids within the polymer with the interferent blocking agent; and depositing a diffusion-limiting layer on said polymer.

87. 87. The method of claim 86, wherein the voids in the polymer run through the thickness of the polymer.

88. 88. The method of claim 87, wherein at least a portion of the voids are exposed at a surface of the electrode material.

89. 87. The method of claim 86, wherein the interferent blocking agent fills at least about 80% of the voids in the polymer to prevent interferents from accessing the electrode material.

90. 87. The method of claim 86, wherein the biorecognition element is glucose oxidase, glucose dehydrogenase, 3-hydroxybutyrate dehydrogenase, or lactate dehydrogenase.

91. 87. The method of claim 86, wherein the polymer comprises one or more of aniline, acetylene, phenylene, phenylene vinylene, phenylenediamine, thiophene, 3,4-ethylenedioxythiophene, and aminophenylboronic acid.

92. 87. The method of claim 86, wherein the diffusion-limiting layer comprises one or more of polydimethylsiloxane, polyurethane, polyvinyl chloride, polyvinylpyrrolidone, polycarbonate, polyethylene, polyethylene terephthalate, polyester, high density polyethylene, low density polyethylene, and polytetrafluoroethylene.

93. 87. The method of claim 86, wherein said applying comprises electropolymerizing said interferent blocking agent.

94. 87. The method of claim 86, wherein the interferent blocker comprises one or more of resorcinol, hydroquinone quinol, 2-amino-4,6-dinitrophenol picramic acid, 3,5-dihydroxytoluene orcinol, 2,4,6-trinitroresorcinol styphnic acid, 2-hydroxyphenol catechol, 9-phenanthrol, pyrogallol, α-naphthol, anisole, phenetole, picric acid, and phenol.

95. 87. The method of claim 86, wherein the interferent blocker comprises phenol.

96. 96. The method of claim 95, wherein the phenol is applied as a mixture having a concentration of about 0.01 mM phenol to about 100 mM phenol.

97. 87. The method of claim 86, wherein at least a portion of the interferent blocking agent is in contact with the electrode material.

98. 87. The method of claim 86, wherein the interference current in the electrode material of the device changes by less than 10% over a period of one week.

99. 1. A device for use in sensing an analyte, comprising: Microneedles and an electrode material on the microneedle; a biorecognition layer on the electrode material, the biorecognition layer comprising a polymer, a biorecognition element configured to react with the analyte, and an interferent blocker filling voids within the polymer.

100. 1. A device for use in sensing an analyte, comprising: Microneedles and an electrode material on the microneedle; a biorecognition layer on the electrode material, the biorecognition layer comprising a phenylenediamine, a biorecognition element, and a polyphenol, the polyphenol filling voids in the phenylenediamine, and the biorecognition element configured to react with the analyte; a polyurethane-based diffusion-limiting layer on the biorecognition layer.

101. 1. A method of manufacturing a device for use in sensing an analyte, comprising: depositing a biorecognition element and a polymer on an electrode material disposed on the microneedle, the biorecognition element configured to react with the analyte; applying an interferent-blocking agent to the polymer after deposition, thereby filling voids within the polymer with the interferent-blocking agent.

102. 1. A method of manufacturing a device for use in sensing an analyte, comprising: depositing a biorecognition element and a phenylenediamine on an electrode material disposed on the microneedle, the biorecognition element being configured to react with the analyte; applying a polyphenol to the phenylenediamine after deposition, thereby filling voids within the phenylenediamine with the polyphenol; depositing a polyurethane-based diffusion-limiting layer on said phenylenediamine.

103. 1. A device for use in sensing an analyte, comprising: Microneedles and an electrode material on the microneedle; a biorecognition layer on the electrode material, the biorecognition layer comprising a phenylenediamine, a biorecognition element configured to react with the analyte, and a polyphenol filling voids within the phenylenediamine; a polyurethane-based diffusion-limiting layer; an adhesion enhancer configured to reduce variability in analyte sensing, the adhesion enhancer comprising 1,4-butanediol diglycidyl ether, positioned between the biorecognition layer and the polyurethane-based diffusion-limiting layer.

104. 1. A method of manufacturing a device for use in sensing an analyte, comprising: depositing a biorecognition element and a phenylenediamine on an electrode material disposed on the microneedle, the biorecognition element being configured to react with the analyte; applying a polyphenol to the phenylenediamine, thereby filling voids within the phenylenediamine with the polyphenol; exposing the phenylenediamine to an adhesion promoter comprising 1,4-butanediol diglycidyl ether; and depositing a polyurethane-based diffusion-limiting layer onto the biorecognition layer after exposing the phenylenediamine to the 1,4-butanediol diglycidyl ether.

105. 1. An analyte monitoring device comprising: a plurality of microneedles arranged in an array, the plurality of microneedles comprising a plurality of working electrodes, a reference electrode, and a counter electrode; The analyte monitoring device, wherein the plurality of working electrodes are disposed between the reference electrode and the counter electrode.

106. 106. The analyte monitoring device of claim 105, wherein the plurality of working electrodes are uniformly spaced from the reference electrode.

107. 106. The analyte monitoring device of claim 105, wherein the plurality of working electrodes are connected to the counter electrode such that current flows from each of the plurality of working electrodes to the counter electrode.

108. 108. The analyte monitoring device of claim 107, wherein the current results from a potential applied between the plurality of working electrodes and the reference electrode.

109. 106. The analyte monitoring device of claim 105, wherein the plurality of microneedles includes a plurality of counter electrodes, and the plurality of working electrodes are disposed between the reference electrode and the plurality of counter electrodes.

110. 110. The analyte monitoring device of claim 109, wherein the plurality of counter electrodes are electrically connected in parallel, and each of the plurality of working electrodes is connected to a plurality of counter electrodes.

111. 111. The analyte monitoring device of claim 110, wherein the multiple counter electrodes are connected in parallel with each other.

112. 111. The analyte monitoring device of claim 110, wherein a majority of the current from a first working electrode of the plurality of working electrodes flows to a first counter electrode of the plurality of counter electrodes, the first counter electrode being positioned closest to the first working electrode relative to the other counter electrodes.

113. 113. The analyte monitoring device of claim 112, wherein the current results from a potential applied between the first working electrode and the reference electrode.

114. 110. The analyte monitoring device of claim 109, wherein the number of working electrodes is equal to the number of counter electrodes.

115. 110. The analyte monitoring device of claim 109, wherein the plurality of working electrodes includes three working electrodes and the plurality of counter electrodes includes three counter electrodes.

116. 116. The analyte monitoring device of claim 115, wherein the three working electrodes form a barrier around the reference electrode.

117. 117. The analyte monitoring device of claim 116, wherein the barrier prevents current flowing from the plurality of working electrodes to the plurality of counter electrodes from flowing through the reference electrode.

118. 106. The analyte monitoring device of claim 105, wherein the number of working electrodes comprises at least a minimum number to isolate the reference electrode from current flowing between the working electrodes and the counter electrode.

119. 106. The analyte monitoring device of claim 105, wherein each of the plurality of working electrodes is disposed on a surface of a tapered distal portion of each of the plurality of microneedles.

120. 120. The analyte monitoring device of claim 119, wherein each of the plurality of working electrodes includes a biorecognition layer, the biorecognition layer including a biorecognition element configured to react with an analyte.

121. 106. The analyte monitoring device of claim 105, further comprising a semiconductor substrate, the plurality of microneedles extending from the semiconductor substrate.

122. 122. The analyte monitoring device of claim 121, wherein each working electrode of the plurality of working electrodes is disposed on a respective microneedle of the plurality of microneedles, and a first microneedle including a first working electrode is disposed in a central region of the semiconductor substrate.

123. 123. The analyte monitoring device of claim 122, wherein the counter electrode is disposed on a second microneedle of the plurality of microneedles, the second microneedle being proximate a first edge of the semiconductor substrate.

124. 124. The analyte monitoring device of claim 123, wherein the reference electrode is disposed on a third microneedle of the plurality of microneedles, the third microneedle being proximate a second edge of the semiconductor substrate, the second edge being opposite the first edge.

125. 125. The analyte monitoring device of claim 124, wherein the plurality of microneedles includes a plurality of counter electrodes, each counter electrode being disposed on a respective microneedle of the plurality of microneedles, each proximate the first edge of the semiconductor substrate.

126. 122. The analyte monitoring device of claim 121, wherein the reference electrode is disposed on a central microneedle of the plurality of microneedles, the central microneedle being positioned in a central region of the semiconductor substrate, and the plurality of working electrodes surrounding the reference electrode.

127. 127. The analyte monitoring device of claim 126, wherein the counter electrode is disposed on each microneedle of the plurality of microneedles, each microneedle being proximate a first edge of the semiconductor substrate.

128. 128. The analyte monitoring device of claim 127, wherein the plurality of microneedles includes a plurality of counter electrodes proximate an outer edge of the semiconductor substrate.

129. 1. A microneedle array for use in analyte sensing, comprising: a plurality of sensing microneedles, each comprising a working electrode including a biorecognition layer, the biorecognition layer including a biorecognition element configured to react with the analyte; a first microneedle having a counter electrode; a second microneedle comprising a reference electrode; the plurality of sensing microneedles are connected to the first microneedles such that an electric current flows between the plurality of sensing microneedles and the first microneedles, the electric current resulting from an electric potential applied between the plurality of sensing microneedles and the second microneedles; A microneedle array, wherein the plurality of sensing microneedles are positioned between the first microneedle and the second microneedle.

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