WO2015178912A1 - Détecteurs d'analytes et leurs procédés d'utilisation - Google Patents

Détecteurs d'analytes et leurs procédés d'utilisation Download PDF

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Publication number
WO2015178912A1
WO2015178912A1 PCT/US2014/039175 US2014039175W WO2015178912A1 WO 2015178912 A1 WO2015178912 A1 WO 2015178912A1 US 2014039175 W US2014039175 W US 2014039175W WO 2015178912 A1 WO2015178912 A1 WO 2015178912A1
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WIPO (PCT)
Prior art keywords
sensor
working electrode
disposed
semiconducting particles
substrate
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Application number
PCT/US2014/039175
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English (en)
Inventor
Tianmei Ouyang
Benjamin J. Feldman
Lam N. Tran
Yi Wang
Original Assignee
Abbott Diabetes Care Inc.
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
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Publication date
Application filed by Abbott Diabetes Care Inc. filed Critical Abbott Diabetes Care Inc.
Priority to PCT/US2014/039175 priority Critical patent/WO2015178912A1/fr
Publication of WO2015178912A1 publication Critical patent/WO2015178912A1/fr

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Classifications

    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
    • G01N27/00—Investigating or analysing materials by the use of electric, electrochemical, or magnetic means
    • G01N27/26—Investigating or analysing materials by the use of electric, electrochemical, or magnetic means by investigating electrochemical variables; by using electrolysis or electrophoresis
    • G01N27/28—Electrolytic cell components
    • G01N27/30—Electrodes, e.g. test electrodes; Half-cells
    • G01N27/327—Biochemical electrodes, e.g. electrical or mechanical details for in vitro measurements
    • G01N27/3271—Amperometric enzyme electrodes for analytes in body fluids, e.g. glucose in blood
    • G01N27/3272—Test elements therefor, i.e. disposable laminated substrates with electrodes, reagent and channels

Definitions

  • a number of systems are available that analyze the constituents of bodily fluids such as blood, urine and saliva. Examples of such systems conveniently monitor the level of particular medically significant fluid constituents, such as, for example, cholesterol, ketones, vitamins, proteins, and various metabolites or blood sugars, such as glucose. Diagnosis and management of patients suffering from diabetes, a disorder where either the pancreas produces insufficient insulin which prevents normal regulation of blood sugar levels or cells do not respond to the insulin that is produced, requires carefully monitoring of blood glucose levels on a daily basis. A number of systems that allow individuals to easily monitor their blood glucose are currently available. Such systems include electrochemical biosensors, including those that comprise a glucose sensor that is adapted to determine the concentration of an analyte in a bodily fluid (e.g., blood) sample.
  • a bodily fluid e.g., blood
  • a person may obtain a blood sample by withdrawing blood from a blood source in his or her body, such as a vein, using a needle and syringe, for example, or by lancing a portion of his or her skin, using a lancing device, for example, to make blood available external to the skin, to obtain the necessary sample volume for in vitro testing.
  • the person may then apply the fresh blood sample to a test strip, whereupon suitable detection methods, such as colorimetric, electrochemical, or photometric detection methods, for example, may be used to determine the person's actual blood glucose level.
  • Analyte sensors with improved performance are desirable.
  • the present disclosure provides sensors, and methods of using and manufacturing such sensors, meeting these and a variety of other needs.
  • the sensors include semiconducting particles and exhibit improved uniformity of distribution of one or more sensing chemistry components, increased effective working electrode surface area and improved reliability without short circuiting the electrodes.
  • the improved reliability is obtained while reducing the reagent chemistry used per sensor, thereby reducing costs.
  • semiconducting particles on a surface of the sample chamber improve sample fill time consistency. Methods of using and manufacturing the sensors are also provided.
  • FIG. 1 is a microphotograph of deposition of a conventional sensing layer formulation on an electrode surface, wherein the sensing layer does not include semiconducting particles.
  • FIG. 2 is a microphotograph of deposition of a sensing layer formulation on an electrode surface, wherein the sensing layer includes semiconducting particles.
  • FIGS. 3A-3C show a schematic view of non-uniform reagent distribution upon drying of a detection reagent solution in the sample chamber of a sensor.
  • FIG. 4 is a microphotograph of deposition of a conventional sensing layer formulation on an electrode surface, wherein the sensing layer does not include semiconducting particles with the electrode surface sectioned.
  • FIG. 5 is a schematic view of a first embodiment of a sensor strip in accordance with the present disclosure.
  • FIG. 6 is an exploded perspective view of the sensor strip shown in FIG. 5 with the layers illustrated individually with the electrodes in a first configuration.
  • FIG. 7 is an exploded perspective view of a second embodiment of a sensor strip in accordance with the present disclosure with the layers illustrated individually with the electrodes in a second configuration.
  • FIG. 8 is a comparison graph of the active electrode area of a control strip, a strip having a conventional sensing layer formulation, and a strip having a sensing layer formulation including semiconducting particles of the present disclosure.
  • FIG. 9 is a comparison graph of fill times for strips having a conventional sensing layer formulation, and strips having a sensing layer formulation including semiconducting particles of the present disclosure at different temperatures.
  • FIG. 10 is a comparison graph of the coefficient of variation for strips having a conventional sensing layer formulation, and strips having a sensing layer formulation including semiconducting particles of the present disclosure at different temperatures.
  • FIG. 11A is a graph of bias from control across various glucose levels for a conventional sensing layer versus a sensing layer formulation including semiconducting particles of the present disclosure.
  • FIG. 1 IB is a graph of fill time across various glucose levels for the conventional sensing layer of FIG. 11 A versus a sensing layer formulation including semiconducting particles of the present disclosure.
  • FIG. 12A is a graph of charge for strips having different loadings of a
  • FIG. 12B is a graph of charge for strips having different loadings of a sensing layer formulation including semiconducting particles of the present disclosure across various glucose levels.
  • FIG. 13A is a graph illustrating the precision of a conventional sensing layer.
  • FIG. 13B is a graph illustrating the precision of a sensing layer formulation including semiconducting particles of the present disclosure.
  • the sensors include semiconducting particles and exhibit improved uniformity of distribution of one or more sensing chemistry components and increased effective working electrode surface area without short circuiting the electrodes.
  • the improved uniformity of distribution and increased effective working electrode surface area result in improved linearity, improved reproducibility, improved yield, improved reaction time, improved glucose recovery and reduced cost.
  • Methods of using and manufacturing the sensors are also provided.
  • the components are disposed proximate to a working electrode of the sensor, such as in vivo and/or in vitro analyte sensors, including, continuous and/or automatic in vivo analyte sensors.
  • embodiments herein provide for inclusion of semiconducting particles in a solution, such as a sensing layer formulation.
  • systems and methods of using the analyte sensors in analyte monitoring are also provided.
  • embodiments disclosed herein are based on the discovery that the addition of semiconducting particles to solution formulations used in the manufacture of in vivo and/or in vitro biosensors greatly improves uniformity and/or distribution of one or more reagent components of the sensor (e.g., an enzyme-containing sensing layer of such devices) as compared to a sensor lacking the semiconducting particles.
  • the result is a reduction, and in some cases the complete elimination, of the buildup of the reagent solution along the edges of the strip, known as the "coffee ring" effect (see homogenous and uniform distribution of the sample in FIG. 2 as compared to the example in FIG. 1).
  • the uniform distribution improves reagent efficiency, thereby reducing the amount of reagent used.
  • Embodiments disclosed herein are also based on the discovery that disposition of semiconducting particles on a surface of the working electrode of the sensor, such as in vitro or in vivo analyte sensors, results in a working electrode with increased effective surface area while reducing or eliminating short circuits in the electrode.
  • the addition of semiconducting particles to solution formulations of such sensors also results in an improved linearity of the sensor over a range of reagent loading as compared to a conventional sensor lacking the semiconducting particles.
  • the semiconducting particles provide for improved fill times as well as improved accuracy over time and over a range of temperatures.
  • the semiconducting particles may be included in any component of a sensor that can benefit from improvement of uniformity of distribution and/or increased electrode surface area.
  • Exemplary components include, but are not limited to, formulations that provide reagents in a sensing layer having an analyte responsive enzyme.
  • Embodiments of the present disclosure relate to sensors having improved uniformity of distribution of one or more analyte detection reagents by inclusion of
  • semiconducting particles in the sensor solution where the detection reagent and semiconducting particles are disposed on a surface of a working electrode of the sensor, such as in vitro or in vivo analyte sensors.
  • a solution such as a detection reagent solution
  • embodiments of the present disclosure provide for inclusion of semiconducting particles in a solution, such as a detection reagent solution, resulting in more uniform distribution of the detecting reagent after the detection reagent solution is dried on the surface of the working electrode.
  • methods of manufacturing the analyte sensors and methods of using the analyte sensors in analyte monitoring are also provided.
  • a detection reagent solution is contacted with a surface of a substrate (e.g., a surface of a working electrode), forming a deposition of the solution on the surface of the substrate.
  • the solution is allowed to dry and cure.
  • the reagent will not be uniformly distributed across the channel (e.g., along the axis perpendicular to the flow of a sample into the sample chamber), and the center of the channel may be partially denuded of reagent, resulting in the analyte not reacting completely in the center of the channel, particularly at high analyte concentrations (e.g., high blood glucose concentrations).
  • This non- uniformity may adversely affect performance characteristics of the sensor, such as decreasing accuracy and increasing fill time as compared to a sensor having substantially uniform distribution of the detection reagent on the working electrode surface.
  • FIG. 1 The result of non-uniform reagent distribution as a reagent solution dries in a sample chamber of a sensor is illustrated in FIG. 1 and is schematically shown in FIGS. 3A-3C.
  • a portion of a partially assembled sensor includes sample chamber 102 defined by substrate 104 and spacer layer 106.
  • the reagent shown as dots
  • FIG. 3C shows a top view of the portion of the sensor shown in FIG. 3B.
  • FIG. 4 illustrates the actual mal-distribution of the reagent on the surface of a sensor.
  • a rectangular working electrode with, e.g., a deposited enzyme
  • Each sub-area is then washed with buffer to extract the deposited enzyme into a known volume of liquid, e.g., about 1 mL.
  • Enzyme activity assays are used to quantify the amount of enzyme in each sub-area.
  • the working electrode in the sample chamber of FIG. 4 is scribed into sub-area A, sub-area B and sub-area C.
  • Sub-area A measured 1.45 units of enzyme
  • sub-area B measured 0.34 units of enzyme
  • sub-area C measured 1.31 units of enzyme.
  • Embodiments of the present disclosure are based on the discovery that the addition of semiconducting particles to a reagent solution used in the manufacture of in vitro or in vivo analyte sensors improves uniformity and/or distribution of one or more detection reagents (e.g., an analyte-responsive enzyme and/or redox mediator) on a surface of the sensor.
  • detection reagents e.g., an analyte-responsive enzyme and/or redox mediator
  • FIG. 2 The results of adding semiconducting particles to a reagent solution for improved reagent uniformity and distribution is schematically illustrated in FIG. 2.
  • the reagent solution is disposed in the sample chamber and includes detection reagent(s) and semiconducting particles.
  • the semiconducting particles inhibit the preferential deposition of reagent components at the sides of the sample chamber.
  • the result is a dry reagent semiconducting particles composition disposed on the substrate (e.g., a working electrode surface) in the sample chamber region, the composition having substantially uniform distribution of the detection reagent(s) attributable to the semiconducting particles being present in the reagent solution during the drying.
  • the particle density of the reagent solution/suspension may be adjusted to achieve a desired amount/configuration of particles in the sample chamber upon drying of the solution/suspension.
  • the particle density may be chosen to achieve uniform distribution of the analyte detection reagent, and also to provide less than a single layer of particles on the surface of the substrate.
  • the particle density may be chosen to achieve uniform distribution of the analyte detection reagent, and also to provide a monolayer, bilayer, or more layers of the particles on the surface of the substrate.
  • the present disclosure provides sensors for determining the concentration of an analyte (e.g., glucose, a ketone, etc.) in a sample fluid.
  • the sensors include a first substrate having a proximal end and a distal end, the first substrate defining a first side edge and a second side edge of the sensor extending from the proximal end to the distal end of the first substrate, the distal end being configured and arranged for insertion into a sensor reader.
  • the sensors also include a second substrate disposed over the first substrate, a working electrode disposed on one of the first and second substrates, a counter electrode disposed on one of the first and second substrates, and a spacer disposed between the first and second substrates and defining a sample chamber that comprises the working electrode and the counter electrode.
  • the sensors include a dry composition disposed on an area of the working electrode, the composition comprising an analyte detection reagent and semiconducting particles configured and arranged to provide for substantially uniform distribution of the detection reagent on the area of the working electrode.
  • substantially uniform distribution of the detection reagent is meant that if the area of the working electrode upon which the dry composition is disposed was subdivided into equal sized smaller areas (or “sub-areas"), these sub-areas would each have the same or substantially the same quantity of disposed analyte detection reagent, within the uncertainty of the measurement method used to quantify the disposed reagent.
  • the quantity of analyte detection reagent disposed on the sub-areas does not differ between sub-areas by more than about 25%.
  • the quantity of detection reagent disposed on the sub- areas does not differ between sub-areas by more than about 20%, 15%, 10%, 5%, 2%, or more than about 1%.
  • the area of the working electrode on which the composition is disposed may comprise any desired amount of semiconducting particles.
  • the area of the working electrode on which the dry composition is disposed includes between about 0.001 and
  • the area of the working electrode may include between about 0.01 and 5 mg of particles per cm semiconducting particles/mm2, between about 0.02 and
  • the particle density may depend, e.g., on the diameter of the particles, the concentration of the particles in the "wet" composition applied to the working electrode surface prior to drying, and/or the like.
  • Embodiments of the present disclosure relate to sensors having a working electrode with increased effective surface area by disposition of semiconducting particles on a surface of the working electrode of the sensor, such as in vitro or in vivo analyte sensors. Also provided are methods of manufacturing the analyte sensors and methods of using the analyte sensors in analyte monitoring.
  • the inventors of the present disclosure have found that disposing one or more layers of semiconducting particles on a surface of a working electrode increases the effective surface area of the working electrode. As a result of the increased effective surface area of the working electrode, higher peak currents, shorter test times, and/or more linear results may be obtained during operation of the sensor. Strips with semiconducting particles included with the reagent solution show a significant increase in double layer charging compared with both a blank strip and a strip having the reagent solution only.
  • the semiconducting particles have a conductivity that is sufficiently high to extend the electrode surface rather than reduce or eliminate the electrode surface area, while also having a conductivity that is too low to cause short circuits, even when the semiconducting particles bridge the short space between facing working and counter electrodes. Sensor strips containing semiconducting particles were deliberately miss-coated outside of the channel of the sample chamber and tested. Even with semiconducting particles outside of the channel, short circuiting was not observed.
  • the working electrode surface can have a monolayer of semiconducting particles disposed thereon.
  • the semiconducting particles are in contact with the working electrode surface, as well as with each other, such that each particle acts as an extension of the electrode surface.
  • sensors having a working electrode surface with more than one layer of semiconducting particles disposed thereon.
  • semiconducting particles of a first layer makes contact with the working electrode surface, with each other, and also with semiconducting particles of a second layer.
  • the semiconducting particles of the second layer make contact with the semiconducting particles of the first layer, as well as each other. Whether one, two or more layers of semiconducting particles are provided on the surface of the working electrode, the result is that all or a majority of the particles act as an extension of the working electrode surface, thereby increasing the effective surface area of the working electrode.
  • one or more layers of semiconducting particles are disposed on a surface of the working electrode (e.g., by depositing a semiconducting particle-containing suspension on the working electrode surface, followed by drying), and an analyte detection solution that includes one or more analyte detection reagents (e.g., an analyte- responsive enzyme and/or a redox mediator) is deposited over the semiconducting particles.
  • an analyte detection reagents e.g., an analyte- responsive enzyme and/or a redox mediator
  • one or more layers of semiconducting particles are disposed on the surface of the working electrode by applying a semiconducting particle suspension that also includes one or more analyte detection reagents (e.g., an analyte-responsive enzyme and/or a redox mediator).
  • analyte detection reagents e.g., an analyte-responsive enzyme and/or a redox mediator.
  • the desired number of layers of semiconducting particles on the working electrode surface may be achieved using any suitable approach.
  • the particle density of the suspension may be controlled to achieve a monolayer, bilayer, tri-layer, or more layers of semiconducting particles on the surface. Whether or not a particular particle density achieves the desired number of layers may be determined, e.g., via microscopic imaging of the particles disposed on the electrode surface.
  • semiconducting particles is achieved by first determining the particle density of a particle suspension required to achieve a monolayer of particles on the electrode surface (for particles having a particular diameter), and then increasing the particle density by a factor of two, three or more to achieve a bilayer, tri-layer, or more layers, respectively, of semiconducting particles on the surface.
  • the inclusion of semiconducting particles on a working electrode surface result in sensors with an increased signal, i.e., peak current.
  • a higher signal is indicative of both well distributed reagents and increased
  • Sensors having higher signals from the inclusion of semiconducting particles on a working electrode surface may result in shortened sensor response times.
  • the analyte sensor comprising semiconducting particles on a working electrode surface provides a signal from electrolysis of an analyte in a sample that is at least 5%, or 10%, or 15%, or 20%, or 30%, or 40%, or 50%, or 60%, or 70%, or 80%, or 90%, or 100%, or 120%, or 130% higher than the signal generated from electrolysis of the analyte in the sample using a similar analyte sensor but not comprising semiconducting particles on a working electrode surface.
  • the higher signal is generated within 0.01 second, or 0.03 second, or 0.01 second, or 0.3 second, or 0.6 second, or 1 second, or 1.3 seconds, or 1.6 seconds, or 2 seconds, or 3 seconds, or 4 seconds, or 5 seconds, or more of applying the sample to the analyte sensor.
  • signal refers to current, charge, resistance, voltage, impedance, or log or integrated values thereof that is related to the concentration of the analyte being analyzed by the sensor.
  • fill time of the sample chamber shows greater stability over time and over different temperature ranges.
  • the analyte sensor comprising semiconducting particles provides a fill time after eight weeks that is at least 5%, or 10%, or 15%, or 20%, or 30%, or 40%, or 50%, or 60%, or 70%, or 80%, or 90%, or 100%, or 110%, or 120%, or 130%, or 140%, or 150%, or 160%, or 170%, or 180%, or 190%, or 200% or more lower than the fill time generated in the sample using a similar analyte sensor but not comprising semiconducting particles.
  • the use of semiconducting particles improves the fill time and thus the shelf life of the strips over a wide range of temperatures.
  • one or more layers of semiconducting particles are disposed on a surface of the sample chamber (e.g., by depositing a semiconducting particle-containing suspension on the desired surface of the sample chamber, followed by drying).
  • the semiconducting particles may be disposed on a portion or all of the sample chamber surface area to improve the fill time and thus the shelf life of the strips.
  • the semiconducting particles can be disposed on all surfaces of the sample chamber.
  • the semiconducting particles can be disposed on surfaces of the sample chamber excluding one or both of the working electrode and the counter electrode.
  • one or more layers of semiconducting particles are disposed on the surface of the working electrode by applying a semiconducting particle suspension that also includes one or more analyte detection reagents (e.g., an analyte-responsive enzyme and/or a redox mediator).
  • analyte detection reagents e.g., an analyte-responsive enzyme and/or a redox mediator.
  • the desired number of layers of semiconducting particles on the surface of the sample chamber may be achieved using any suitable approach.
  • the particle density of the suspension may be controlled to achieve a monolayer, bilayer, tri-layer, or more layers of semiconducting particles on the surface. Whether or not a particular particle density achieves the desired number of layers may be determined, e.g., via microscopic imaging of the particles disposed on the surface.
  • the desired number of layers of semiconducting particles is achieved by first determining the particle density of a particle suspension required to achieve a monolayer of particles on the electrode surface (for particles having a particular diameter), and then increasing the particle density by a factor of two, three or more to achieve a bilayer, tri-layer, or more layers, respectively, of semiconducting particles on the surface.
  • the sensors exhibit increased reproducibility (accuracy) over time and over different temperature ranges.
  • the analyte sensor comprising semiconducting particles exhibits reproducibility at a rate at least 5%, or 10%, or 15%, or 20%, or 30%, or 40%, or 50%, or 60%, or 70%, or 80%, or 90%, or 100%, or 110%, or 120%, or 130%, or 140%, or 150%, or 160%, or 170%, or 180%, or 190%, or 200% or more greater than the reproducibility exhibited by a sample using a similar analyte sensor but not comprising semiconducting particles. As reproducibility increases, yield increases. Accuracy of the strips overtime is also improved.
  • the sensors exhibit increased linearity over a range of loading.
  • the analyte sensor comprising semiconducting particles exhibits linearity at least across reagent loadings from 40% to 100% and across analyte levels from 50 to 350 mg/dL.
  • the charge for the analyte sensor comprising semiconducting particles remained nearly identical at a particular glucose level at least 40%, at least 60%, at least 80% and 100%.
  • the analyst sensor without semiconducting particles exhibit non-linearity at all reagent loading levels.
  • the non-linearity is a product of the uneven reagent deposition on the working electrode when no semiconducting particles are used. As reagent loading is decreased to 40%, this non-linearity increases substantially.
  • the charge for the analyte sensor without semiconducting particles dropped significantly at a particular glucose level from 100% to 40%.
  • the analyte sensors comprising the semiconducting particles exhibit superior recovery at the various loadings as compared with the strip without semiconducting particles at 100% loading, indicating that reagent loading can be reduced with the use of semiconducting particles without sacrificing charge.
  • Additional suitable sensor and meter configurations are known in the art which may be suitable for use in the disclosed embodiments. Additional suitable sensor and meter configurations include, but are not limited to, those described in U.S. Patent Publication No. 2011/0287528 and U.S. Patent No. 6,616,819.
  • a first embodiment of a sensor 10 is schematically illustrated, herein shown in the shape of a strip. It is to be understood that the sensor may be any suitable shape.
  • Sensor strip 10 has a first substrate 12, a second substrate 14, and a spacer 15 positioned there between.
  • Sensor strip 10 includes at least one working electrode 24 and at least one counter electrode 22.
  • Sensor strip 10 also includes an optional insertion monitor 30.
  • Sensor strip 10 has a first, proximal end 10A and an opposite, distal end 10B. At proximal end 10A, the sample to be analyzed is applied to sensor 10.
  • Proximal end 10A could be referred as 'the fill end', 'sample receiving end', or similar.
  • Distal end 10B of sensor 10 is configured for operable, and usually releasable, connecting to a device such as a meter.
  • Sensor strip 10 is a layered construction, in certain embodiments having a generally rectangular shape, i.e., its length is longer than its width, although other shapes are possible as well, as noted above.
  • the length of sensor strip 10 is from end 10A to end 10B.
  • the overall length of sensor strip 10 may be no less than about 10 mm and no greater than about 50 mm.
  • the length may be between about 30 and 45 mm; e.g., about 30 to 40 mm. It is understood, however that shorter and longer sensor strips 10 could be made.
  • the overall width of sensor strip 10 may be no less than about 3 mm and no greater than about 15 mm.
  • the width may be between about 4 and 10 mm, about 5 to 8 mm, or about 5 to 6 mm.
  • sensor strip 10 has a length of about 32 mm and a width of about 6 mm.
  • sensor strip 10 has a length of about 40 mm and a width of about 5 mm.
  • sensor strip 10 has a length of about 34 mm and a width of about 5 mm.
  • sensor strip 10 has first and second substrates 12, 14, nonconducting, inert substrates which form the overall shape and size of sensor strip 10.
  • Substrates 12, 14 may be substantially rigid or substantially flexible.
  • substrates 12, 14 are flexible or deformable.
  • suitable materials for substrates 12, 14 include, but are not limited, to polyester, polyethylene, polycarbonate, polypropylene, nylon, and other "plastics" or polymers.
  • the substrate material is "Melinex" polyester. Other non-conducting materials may also be used.
  • Substrate 12 includes first or proximal end 12A and second or distal end 12B, and substrate 14 includes first or proximal end 14A and second or distal end 14B. As indicated above, positioned between substrate 12 and substrate 14 may be spacer 15 to separate first substrate 12 from second substrate 14. In some embodiments, spacer 15 extends from end 10A to and 10B of sensor strip 10, or extends short of one or both ends. Spacer 15 is an inert nonconducting substrate, typically at least as flexible and deformable (or as rigid) as substrates 12, 14. In certain embodiments, spacer 15 is an adhesive layer or double-sided adhesive tape or film that is continuous and contiguous.
  • any adhesive selected for spacer 15 should be selected to not diffuse or release material which may interfere with accurate analyte measurement.
  • the thickness of spacer 15 may be constant throughout, and may be at least about 0.01 mm (10 ⁇ ) and no greater than about 1 mm or about 0.5 mm.
  • the thickness may be between about 0.02 mm (20 ⁇ ) and about 0.2 mm (200 ⁇ ). In one certain
  • the thickness is about 0.05 mm (50 ⁇ ), and about 0.1 mm (100 ⁇ ) in another embodiment.
  • the sensor includes a sample chamber for receiving a volume of sample to be analyzed; in the embodiment illustrated, particularly in FIG. 5, sensor strip 10 includes sample chamber 20 having an inlet 21 for access to sample chamber 20.
  • sensor strip 10 is a side-fill sensor strip, having inlet 21 present on a side edge of strip 10.
  • Tip-fill sensors, having an inlet at, for example, end 10A, are also within the scope of this disclosure and are described with reference to Fig. 7, as well as corner and top filling sensors.
  • Sample chamber 20 is configured so that when a sample is provided in chamber 20, the sample is in electrolytic contact with both a working electrode and a counter electrode, which allows electrical current to flow between the electrodes to affect the electrolysis (electro-oxidation or electro-reduction) of the analyte.
  • Sample chamber 20 is defined by substrate 12, substrate 14 and spacer 15; in many embodiments, sample chamber 20 exists between substrate 12 and substrate 14 where spacer 15 is not present.
  • spacer 15 is removed to provide a volume between substrates 12, 14 without spacer 15; this volume of removed spacer is sample chamber 20.
  • the thickness of sample chamber 20 is generally the thickness of spacer 15.
  • Sample chamber 20 has a volume sufficient to receive a sample of biological fluid therein.
  • sample chamber 20 has a volume that is typically no more than about 1 ⁇ , for example no more than about 0.5 ⁇ , and also for example, no more than about 0.25 ⁇ L ⁇ .
  • a volume of no more than about 0.1 ⁇ ⁇ is also suitable for sample chamber 20, as are volumes of no more than about 0.05 ⁇ ⁇ and about 0.03 ⁇ L ⁇ .
  • the thickness of sample chamber 20 corresponds typically to the thickness of spacer 15. Particularly for facing electrode configurations, as in the sensor illustrated in FIG.
  • this thickness is small to promote rapid electrolysis of the analyte, as more of the sample will be in contact with the electrode surface for a given sample volume.
  • a thin sample chamber 20 helps to reduce errors from diffusion of analyte into the sample chamber during the analyte assay, because diffusion time is long relative to the measurement time, which may be about 5 seconds or less.
  • the sensor includes a working electrode and at least one counter electrode.
  • the counter electrode may be a counter/reference electrode. If multiple counter electrodes are present, one of the counter electrodes will be a counter electrode and one or more may be reference electrodes.
  • the sensor includes at least one working electrode positioned within the sample chamber. In FIG. 6, working electrode 24 is illustrated on substrate 14. In alternate embodiments, a working electrode is present on a different surface or substrate, such as substrate 12.
  • Working electrode 24 extends from the sample chamber 20, proximate first end 10A, to the other end of the sensor 10, end 10B, as an electrode extension called a "trace". The trace provides a contact pad 25 for providing electrical connection to a meter or other device to allow for data and measurement collection, as will be described later.
  • Contact pad 25 may be positioned on a tab 27 that extends from the substrate on which working electrode 24 is positioned, such as substrate 12 or 14.
  • a tab has more than one contact pad positioned thereon.
  • a single contact pad is used to provide a connection to one or more electrodes; that is, multiple electrodes are coupled together and are connected via one contact pad.
  • working electrode 24 is provided in sample chamber 20 for the analysis of analyte, in conjunction with the counter electrode.
  • a dry composition including at least one analyte detection reagent e.g., an analyte-responsive enzyme and/or a redox mediator
  • semiconducting particles may be disposed on a surface of an area of working electrode 24, e.g., all or a portion of the surface of working electrode region 32.
  • the dry composition may be disposed on working electrode 24 prior to disposing spacer 15 on substrate 14.
  • spacer 15 is first disposed on substrate 14 (creating a channel having working electrode 24 as its base, similar to the channel shown in FIG.
  • an aqueous composition that includes at least one detection reagent and semiconducting particles to all or a portion of the surface of working electrode region 32.
  • the detection reagent(s) remain distributed substantially uniformly over the working electrode surface due to the presence of the semiconducting particles in the composition (see, e.g., FIG. 2).
  • At least one analyte detection reagent may be disposed on a surface of the working electrode 24, e.g., all or a portion of the surface of working electrode region 32.
  • Semiconducting particles may be disposed on a surface of the sample chamber 20, e.g., all or a portion of one or more than one surface of the sample chamber 20.
  • the sample chamber 20 is defined by substrate 12, substrate 14 and spacer 15; so the semiconducting particles may be disposed on one or more of the surfaces of substrate 12, substrate 14, spacer 15 that form the sample chamber 20.
  • the working electrode 24 is positioned on substrate 12 or substrate 14 and the counter electrode 22 is positioned on substrate 12 or substrate 14, the semiconducting particles can be disposed on at least a portion of one or both of the working electrode 24 and the counter electrode 22.
  • At least one counter electrode is positioned on one of first substrate
  • counter electrode 22 is illustrated on substrate 12.
  • Counter electrode 22 extends from the sample chamber 20, proximate end 10A, to the other end of the sensor 10, end 10B, as an electrode extension called a "trace".
  • the trace provides a contact pad 23 for providing electrical connection to a meter or other device to allow for data and measurement collection, as will be described later.
  • Contact pad 23 may be positioned on a tab 26 that extends from the substrate on which counter electrode 22 is positioned, such as substrate 12.
  • a tab has more than one contact pad positioned thereon.
  • a single contact pad is used to provide a connection to one or more electrodes; that is, multiple electrodes are coupled together and are connected via one contact pad.
  • Working electrode 24 and counter electrode 22 may be disposed opposite to and facing each other to form facing electrodes. See for example, FIG. 6, which has working electrode 24 on substrate 14 and counter electrode 22 on substrate 12, forming facing electrodes. In this configuration, the sample chamber is typically present between the two electrodes 22, 24.
  • Working electrode 24 and counter electrode 22 may alternately be positioned generally planar to one another, such as on the same substrate, to form co-planar or planar electrodes.
  • Sensor strip 10 may be indicated as filled, or substantially filled, by observing a signal between an optional indicator electrode and one or both of working electrode 24 or counter electrode 22 as sample chamber 20 fills with fluid. When fluid reaches the indicator electrode, the signal from that electrode will change. Suitable signals for observing include, for example, voltage, current, resistance, impedance, or capacitance between the indicator electrode and, for example, working electrode 24.
  • the senor may be observed after filling to determine if a value of the signal (e.g., voltage, current, resistance, impedance, or capacitance) has been reached indicating that the sample chamber is filled.
  • the optional indicator electrode may also be used to improve the precision of the analyte measurements.
  • the indicator electrode may operate as a working electrode or as a counter electrode or counter/reference electrode. Measurements from the indicator electrode/working electrode may be combined (e.g., added or averaged) with those from the first counter/reference electrode/working electrode to obtain more accurate
  • the sensor or equipment that the sensor is connected with may include a signal (e.g., a visual sign or auditory tone) that is activated in response to activation of the indicator electrode to alert the user that the sample chamber is beginning to fill with sample and/or that the sample chamber is sufficiently filled with sample to measure the analyte concentration.
  • the sensor or equipment may be configured to initiate a reading when the indicator electrode indicates that the sample chamber has been filled with or without alerting the user. The reading may be initiated, for example, by applying a potential between the working electrode and the counter electrode and beginning to monitor the signals generated at the working electrode.
  • analyte sensor is illustrated as analyte sensor 210.
  • the analyte sensor strip 210 has a first substrate 212, a second substrate 214, and a spacer 215 positioned there between.
  • Analyte sensor strip 210 includes at least one working electrode 222 and at least one counter electrode 224.
  • Analyte sensor strip 210 has a first, proximal end and an opposite, distal end. At proximal end, sample to be analyzed is applied to sensor 210. Proximal end could be referred as "the fill end" or “sample receiving end”.
  • Distal end of sensor 210 is configured for operable connection to a device such as a meter.
  • Sensor strip 210 is a layered construction, in certain embodiments having a generally rectangular shape, which is formed by first and second substrates 212, 214.
  • Substrate 212 includes first or proximal end 212A and second or distal end 212B
  • substrate 214 includes first or proximal end 214A and second or distal end 214B.
  • Sensor strip 210 includes sample chamber 220 having an inlet 221 for access to sample chamber 220.
  • Sensor strip 210 is a tip-fill sensor, having inlet 221 at the proximal end.
  • Sample chamber 220 is defined by substrate 212, substrate 214 and spacer 215. Generally opposite to inlet 221, through substrate 212 is a vent 230 from sample chamber 220.
  • At least one working electrode 222 is illustrated on substrate 214.
  • Working electrode 222 extends from end 214A into sample chamber 220 to end 214B.
  • Sensor 210 also includes at least one counter electrode 224, in this embodiment on substrate 214.
  • Counter electrode 224 extends from sample chamber 220, proximate first proximal end to distal end.
  • Working electrode 222 and counter electrode 224 are present on the same substrate, e.g., as planar or co-planar electrodes.
  • a dry composition including at least one analyte detection reagent e.g., an analyte- responsive enzyme and/or a redox mediator
  • semiconducting particles may be disposed on a surface of an area of working electrode 222, e.g., all or a portion of the surface of working electrode area 236.
  • the dry composition may be disposed on working electrode 222 prior to disposing spacer 215 on substrate 214.
  • spacer 215 is first disposed on substrate 214 (creating a channel having working electrode 222 as a portion of its base, similar to the channel shown in FIG. 3A), followed by application of an aqueous composition that includes at least one detection reagent and semiconducting particles to an exposed portion of the surface of working electrode area 232.
  • the at least one detection reagent remains distributed substantially uniformly over the working electrode surface to which the composition is applied, due to the presence of the semiconducting particles in the composition (see, e.g., the sensor in FIG. 2).
  • At least one analyte detection reagent may be disposed on a surface of the working electrode 224, e.g., all or a portion of the surface of working electrode region 232.
  • Semiconducting particles may be disposed on a surface of the sample chamber 220, e.g., all or a portion of one or more than one surface of the sample chamber 220.
  • the sample chamber 220 is defined by substrate 212, substrate 214 and spacer 215; so the semiconducting particles may be disposed on one or more of the surfaces of substrate 212, substrate 214, spacer 215 that form the sample chamber 220.
  • the semiconducting particles can be disposed on at least a portion of one or both of the working electrode 224 and the counter electrode 222.
  • an analyte sensor includes a working electrode and a reference/counter electrode, comprising a first portion located in the sample chamber and a second portion for connection to a meter.
  • the working electrode may be formed from a suitable conducting material.
  • the conducting material may have relatively low electrical resistance and may be electrochemically inert over the potential range of the sensor during operation and substantially transparent.
  • the working electrode includes a material selected from the group consisting of gold, carbon, platinum, ruthenium, palladium, silver, silver chloride, silver bromide, and combinations thereof.
  • the working electrode may be a thin layer of gold, tin oxide, platinum, ruthenium dioxide or palladium, indium tin oxide, zinc oxide, fluorine doped tin oxide, as well as other non-corroding materials known to those skilled in the art.
  • the working electrode can be a combination of two or more conductive materials.
  • the working electrode may be constructed from thin layer of gold in the sample chamber and of carbon outside the sample chamber.
  • the working electrode can be applied on a substrate by any of a variety of methods, including by being deposited, such as by vapor deposition or vacuum deposition or otherwise sputtered, printed on a flat surface or in an embossed or otherwise recessed surface, transferred from a separate carrier or liner, etched, or molded. Suitable methods of printing include screen-printing, piezoelectric printing, ink jet printing, laser printing, photolithography, painting, gravure roll printing, transfer printing, and other known printing methods.
  • Semiconducting particles for improving the distribution of analyte detection reagents and increasing the effective surface area of a working electrode while avoiding short circuiting may be used in the sensors of the present disclosure.
  • the semiconducting particles can comprise, as non- limiting examples, tin oxide and antimony doped tin oxide.
  • the semiconducting particles can be in solution, such as antimony doped tin oxide sol.
  • the semiconducting particles can be dispersed, for example, in water or any other liquid suitable for water-based applications.
  • semiconducting particles include Ge, CuCl, CuBr, Cul, AgCl, AgBr, Agl, Ag 2 S, ZnS, HgS, ZnSe, CdS, CdSe, CdTe, HgTe, PbS, BN, A1N, GaN, Al x Ga xN, GaP GaAs, GaSb, InP, InAs, In x Ga xAs, Si xGe x , Si 3 N 4 , ZrN, CaF 2 , YF 3 , A1 2 0 3 , Si0 2 , Ti0 2 , Zr 2 0 3 , Zr0 2 , Sn0 2 , YSi 2 , GaInP 2 , Cd 3 P 2 , Fe 2 S, CuIn 2 S 2 , MoS 2 , In 2 S 3 , Bi 2 S 3 , CuIn 2 Se 2 , In 2 Se 3 , Hgl 2 and P
  • the semiconducting particles can be a nanomaterial, such as a nanopowder or a nanoparticle.
  • the nanopowder or nanoparticle will have semiconducting particles having a diameter of from about 1 nm to about 300 nm, including about 10 nm to about 290 nm, about 15 nm to about 275 nm, about 20 nm to about 250 nm, about 30 nm to about 225 nm, about 35 nm to about 200 nm, about 40 nm to about 175 nm, about 45 nm to about 150 nm, about 50 nm to about 125 nm, about 55 nm to about 100 nm, and about 60 nm to about 75 nm.
  • the semiconducting particles are nanospheres or microspheres.
  • the semiconducting particles suitable for use in the embodiments disclosed will have conductivity within a range that provides the advantages discussed, including extending the electrode surface, while having conductivity too low to short circuit the electrodes.
  • antimony doped tin oxide semiconducting particles have a conductivity of approximately 12,000 ohm/sqr/mil.
  • the counter electrode may be constructed in a manner similar to the working electrode.
  • the term "counter electrode” refers to an electrode that functions as a counter electrode, or both a reference electrode and a counter electrode.
  • the counter electrode can be formed, for example, by depositing electrode material onto a substrate.
  • the material of the counter electrode may be deposited by a variety of methods such as those described above for the working electrode.
  • the counter electrode includes a material selected from the group consisting of gold, carbon, platinum, ruthenium, palladium, silver, silver chloride, silver bromide, and combinations thereof.
  • suitable materials for the counter electrode include Ag/AgCl or Ag/AgBr printed on a non-conducting substrate.
  • the counter electrode comprises a thin conductive layer such as gold, tin oxide, indium tin oxide, layered with AgCl or AgBr, for example.
  • analyte sensor electrode configurations are known in the art which may be suitable for use in the disclosed analyte sensors.
  • suitable configurations can include configurations having a working electrode positioned in opposition to a
  • Additional suitable electrode configurations include, but are not limited to, those described in U.S. Patent Application Publication No. 2007/0095661; U.S. Patent Application Publication No. 2006/0091006; U.S. Patent Application Publication No. 2006/0025662; U.S. Patent Application Publication No. 2008/0267823; U.S. Patent Application Publication No. 2007/0108048; U.S. Patent Application Publication No. 2008/0102441; U.S. Patent Application Publication No. 2008/0066305; U.S. Patent Application Publication No. 2007/0199818; U.S. Patent Application Publication No.
  • analytes can be detected and quantified using the analyte sensors disclosed herein including, but not limited to, glucose, blood ⁇ -ketone, ketone bodies, lactate, acetyl choline, amylase, bilirubin, cholesterol, chorionic gonadotropin, creatine kinase (e.g., CK- MB), creatine, DNA, fructosamine, glutamine, growth hormones, hormones, ketones, lactate, peroxide, prostate-specific antigen, prothrombin, RNA, thyroid stimulating hormone, and troponin, in sample of body fluid.
  • creatine kinase e.g., CK- MB
  • Analyte sensors may also be configured to detect and/or quantify drugs, such as, for example, antibiotics (e.g., gentamicin, vancomycin, and the like), digitoxin, digoxin, drugs of abuse, theophylline, and warfarin.
  • antibiotics e.g., gentamicin, vancomycin, and the like
  • digitoxin digoxin
  • digoxin digoxin
  • drugs of abuse drugs of abuse
  • theophylline and warfarin.
  • Assays suitable for determining the concentration of DNA and/or RNA are disclosed in U.S. Patent No. 6,281,006 and U.S. Patent No. 6,638,716, the disclosures of each of which are incorporated by reference herein.
  • the disclosed analyte sensors may include in the sample chamber an analyte responsive enzyme which is capable of transferring electrons to or from a redox mediator and the analyte.
  • an analyte responsive enzyme which is capable of transferring electrons to or from a redox mediator and the analyte.
  • a glucose oxidase (GOD) or glucose dehydrogenase (GDH) can be used when the analyte is glucose.
  • GDH glucose dehydrogenase
  • a lactate oxidase can be used when the analyte is lactate.
  • the analyte-responsive enzyme is disposed on the working electrode.
  • the analyte-responsive enzyme is immobilized on the working electrode. This is accomplished, for example, by cross linking the analyte-responsive enzyme with a redox mediator on the working electrode, thereby providing a sensing layer on the working electrode.
  • the analyte-responsive enzyme is disposed adjacent to the electrode.
  • the analyte-responsive enzyme and redox mediator are positioned in close proximity to the working electrode in order to provide for electrochemical communication between the analyte-responsive enzyme and redox mediator and the working electrode.
  • the analyte-responsive enzyme and redox mediator are positioned relative to the reference/counter electrode such that electrochemical communication between the analyte- responsive enzyme and the redox mediator and the reference/counter electrode is minimized.
  • analyte-responsive enzymes and cofactors which may be used in connection with the disclosed analyte sensors are described in U.S. Patent No. 6,736,957 and U.S. Patent Publication No. 2011/0318810, the disclosures of which are incorporated by reference herein.
  • a flavin-binding glucose dehydrogenase with a high substrate specificity for D-glucose can be used.
  • the flavin-binding glucose dehydrogenase is derived from a microorganism belonging to the genus Mucor.
  • the flavin-binding glucose dehydrogenase has a low reactivity for maltose, D-galactose and D-xylose compared to its reactivity for D-glucose, and therefore is relatively unaffected by these saccharide compounds.
  • the flavin-binding glucose dehydrogenase is also relatively unaffected by dissolved oxygen, and allows accurate measurement of glucose amounts even in the presence of saccharide compounds other than glucose in samples.
  • Examples of preferred enzymes as flavin-binding glucose dehydrogenase enzymes are those having the following enzymo-chemical properties:
  • Glucose dehydrogenase having such enzymo-chemical properties allows accurate measurement of D-glucose levels without being affected by saccharide compounds such as maltose, D-galactose and D-xylose present in measuring samples. Furthermore, because it has satisfactory activity in a pH range and temperature range that are suitable for clinical diagnosis such as measurement of blood glucose levels, it can be suitably used as a diagnostic
  • the sample chamber in order to facilitate the electrochemical reaction of the analyte sensor the sample chamber also includes an enzyme co-factor.
  • an enzyme co-factor for example, where the analyte-responsive enzyme is glucose dehydrogenase (GDH), suitable cofactors include pyrroloquinoline quinone (PQQ), nicotinamide adenine dinucleotide NAD+ and flavin adenine dinucleotide (FAD).
  • PQQ pyrroloquinoline quinone
  • FAD flavin adenine dinucleotide
  • the analyte detected and/or measured by the sensor described herein may be ketone and the enzyme included in the sensor is hydroxybutyrate dehydrogenase.
  • the sample chamber may include a redox mediator.
  • the redox mediator is immobilized on the working electrode. Materials and methods for immobilizing a redox mediator on an electrode are provided in U.S. Patent No. 6,592,745, the disclosure of which is incorporated by reference herein.
  • the redox mediator is disposed adjacent to the working electrode.
  • the redox mediator mediates a current between the working electrode and the analyte when present.
  • the mediator functions as an electron transfer agent between the electrode and the analyte.
  • Almost any organic or organometallic redox species can be used as a redox mediator.
  • suitable redox mediators are rapidly reducible and oxidizable molecules having redox potentials a few hundred millivolts above or below that of the standard calomel electrode (SCE), and typically not more reducing than about -200 mV and not more oxidizing than about +400mV versus SCE.
  • organic redox species are quinones and quinhydrones and species that in their oxidized state have quinoid structures, such as Nile blue and indophenol.
  • quinones and partially oxidized quinhydrones react with functional groups of proteins such as the thiol groups of cysteine, the amine groups of lysine and arginine, and the phenolic groups of tyrosine which may render those redox species unsuitable for some of the sensors of the present invention, e.g., sensors that will be used to measure analyte in biological fluids such as blood.
  • mediators suitable for use in the analyte sensors have structures which prevent or substantially reduce the diffusional loss of redox species during the period of time that the sample is being analyzed.
  • Suitable redox mediators include a redox species bound to a polymer which can in turn be immobilized on the working electrode.
  • Useful redox mediators and methods for producing them are described in U.S. Patent Nos. 5,262,035; 5,264,104;
  • any organic or organometallic redox species can be bound to a polymer and used as a redox mediator.
  • the redox species is a transition metal compound or complex.
  • the transition metal compounds or complexes may be osmium, ruthenium, iron, and cobalt compounds or complexes.
  • the redox mediator may be an osmium compounds and complex.
  • One type of non-releasable polymeric redox mediator contains a redox species covalently bound in a polymeric composition.
  • An example of this type of mediator is poly(vinylferrocene) .
  • a suitable non-releasable redox mediator contains an
  • these mediators include a charged polymer coupled to an oppositely charged redox species.
  • these type of mediator include a negatively charged polymer such as Nafion® (Dupont) coupled to a positively charged redox species such as an osmium or ruthenium polypyridyl cation.
  • a positively charged polymer such as quaternized poly(4-vinyl pyridine) or poly(l -vinyl imidazole) coupled to a negatively charged redox species such as ferricyanide or ferrocyanide.
  • the suitable non-releasable redox mediators include a redox species coordinatively bound to the polymer.
  • the mediator may be formed by coordination of an osmium or cobalt 2, 2'-bipyridyl complex to poly(l -vinyl imidazole) or poly(4-vinyl pyridine).
  • the redox mediator may be a osmium transition metal complex with one or more ligands having a nitrogen-containing heterocycle such as 2,2' -bipyridine, 1,10-phenanthroline or derivatives thereof. Furthermore, the redox mediator may also have one or more polymeric ligands having at least one nitrogen-containing heterocycle, such as pyridine, imidazole, or derivatives thereof. These mediators exchange electrons rapidly between each other and the electrodes so that the complex may be rapidly oxidized and reduced.
  • Derivatives of 2,2' -bipyridine for complexation with the osmium cation may be 4,4'- dimethyl-2,2' -bipyridine and mono-, di-, and polyalkoxy-2,2'-bipyridines, such as 4,4'- dimethoxy-2,2' -bipyridine, where the carbon to oxygen ratio of the alkoxy groups is sufficient to retain solubility of the transition metal complex in water.
  • Preferred derivatives of 1,10-phenanthroline for complexation with the osmium cation are 4,7-dimethyl- 1,10-phenanthroline and mono-,di-, and polyalkoxy-1,10- phenanthrolines, such as 4,7-dimethoxy- 1,10-phenanthroline, where the carbon to oxygen ratio of the alkoxy groups is sufficient to retain solubility of the transition metal complex in water.
  • Exemplary polymers for complexation with the osmium cation include poly(l-vinyl imidazole), e.g., PVI, and poly(4- vinyl pyridine), e.g., PVP, either alone or with a copolymer. Most preferred are redox mediators with osmium complexed with poly(l -vinyl imidazole) alone or with a copolymer.
  • Suitable redox mediators have a redox potential between about -150 mV to about
  • the potential of the redox mediator can be between about -100 mV and +100 mV, e.g., between about -50 mV and +50 mV.
  • suitable redox mediators have osmium redox centers and a redox potential more negative than +100 mV versus SCE, e.g., the redox potential is more negative than +50 mV versus SCE, e.g., is near -50 mV versus SCE.
  • the redox mediators of the disclosed analyte sensors are airoxidizable. This means that the redox mediator is oxidized by air, e.g., so that at least
  • Airoxidizable redox mediators include osmium cations complexed with two mono-, di-, or polyalkoxy-2,2'-bipyridine or mono-, di-, or polyalkoxy-l,10-phenanthroline ligands, the two ligands not necessarily being the same, and further complexed with polymers having pyridine and imidazole functional groups.
  • Os[4,4'-dimethoxy-2,2'-bipyridine]2Cl+/+2 complexed with poly(4- vinyl pyridine) or poly(l-vinyl imidazole) attains approximately 90% or more oxidation in air.
  • the redox mediator is 1,10 Phenanthrolene- 5,6-dione (PQ).
  • a dielectric may be deposited on the electrode surrounding the region with the bound redox mediator. Suitable dielectric materials include waxes and nonconducting organic polymers such as polyethylene. Dielectric may also cover a portion of the redox mediator on the electrode. The covered portion of the mediator will not contact the sample, and, therefore, will not be a part of the electrode's working surface.
  • the range for the acceptable amount of redox mediator typically has a lower limit.
  • the minimum amount of redox mediator that may be used is the concentration of redox mediator that is necessary to accomplish the assay within a desirable measurement time period, for example, no more than about 5 minutes, or no more than about 1 minute, or no more than about 30 seconds, or no more than about 10 seconds, or no more than about 5 seconds, or no more than about 3 seconds, or no more than about 1 second or less.
  • the analyte sensor can be configured (e.g., by selection of redox mediator, positioning of electrodes, etc.) such that the sensor signal is generated at the working electrode with a measurement period of no greater than about 5 minutes and such that a background signal that is generated by the redox mediator is no more than five times a signal generated by oxidation or reduction of 5mM analyte.
  • the analyte sensor is configured such that the background signal that is generated by the redox mediator is less than the signal generated by oxidation or reduction of 5mM glucose.
  • the background that is generated by the redox mediator is no more than 25% of the signal generated by oxidation or reduction of 5mM analyte, e.g., no more than 20%, no more than 15% or no more than 5%.
  • the analyte is glucose and the background that is generated by the redox mediator is no more than 25% of the signal generated by oxidation or reduction of 5mM glucose, e.g., no more than 20%, no more than 15% or no more than 5% of the signal generated by electrolysis of glucose.
  • the sample chamber may be empty prior to entry of the sample.
  • the sample chamber can include a sorbent material to sorb and hold a fluid sample during detection and/or analysis.
  • Suitable sorbent materials include polyester, nylon, cellulose, and cellulose derivatives such as nitrocellulose.
  • the sorbent material facilitates the uptake of small volume samples by a wicking action which may complement or replace any capillary action of the sample chamber.
  • a portion or the entirety of the wall of the sample chamber may be covered by a surfactant, such as, for example, Zonyl FSO.
  • the sorbent material is deposited using a liquid or slurry in which the sorbent material is dissolved or dispersed.
  • the solvent or dispersant in the liquid or slurry may then be driven off by heating or evaporation processes.
  • Suitable sorbent materials include, for example, cellulose or nylon powders dissolved or dispersed in a suitable solvent or dispersant, such as water.
  • the particular solvent or dispersant should also be compatible with the material of the electrodes (e.g., the solvent or dispersant should not dissolve the electrodes).
  • One of the functions of the sorbent material is to reduce the volume of fluid needed to fill the sample chamber of the analyte sensor.
  • the actual volume of sample within the sample chamber is partially determined by the amount of void space within the sorbent material.
  • suitable sorbents consist of about 5% to about 50% void space.
  • the sorbent material consists of about 10% to about 25% void space.
  • the analyte sensors can be configured for top-filling, tip-filling, corner-filling, and/or side-filling.
  • the analyte sensors include one or more optional fill assist structures, e.g., one or more notches, cut-outs, indentations, and/or protrusions, which facilitate the collection of the fluid sample.
  • the analyte sensor can be configured such that the proximal end of the analyte sensor is narrower than the distal end of the analyte sensor.
  • the analyte sensor includes a tapered tip at the proximal end of the analyte sensor, e.g., the end of the analyte sensor that is opposite from the end that engages with a meter.
  • concentration of an analyte in a fluid sample from a subject include contacting a fluid sample with the sensor, generating a sensor signal at the working electrode, and determining the concentration of the analyte using the sensor signal.
  • the subject methods may employ any of the sensors described herein, e.g., sensors having improved uniformity of distribution of one or more analyte detection reagents and/or increased effective working electrode surface area.
  • a variety of approaches may be employed to determine the concentration of the analyte.
  • an electrochemical analyte concentration determining approach is used.
  • determining the concentration of the analyte using the sensor signal may be performed by coulometric, amperometric, potentiometric, or any other convenient
  • the subject methods include obtaining the sample from a subject.
  • the sample may be obtained, e.g., using a lancet to create an opening in a skin surface at which blood subsequently presents.
  • the blood sample may be obtained from the finger of a subject.
  • the blood sample may be obtained from a region of the subject having a lower nerve end density as compared to a finger.
  • Obtaining a blood sample from a region having a lower nerve end density as compared to a finger is generally a less painful approach for obtaining a blood sample and may improve patient compliance, e.g., in the case of a diabetes patient where regular monitoring of blood glucose levels is critical for disease management.
  • methods of manufacturing analyte sensors include forming a working electrode on a first substrate, forming a spacer layer on the first substrate, the spacer layer defining a sample chamber region on the first substrate, and applying a reagent composition on a surface of the working electrode in the sample chamber region.
  • the reagent composition may include one or more analyte detection reagents (e.g., an analyte-responsive enzyme and/or a redox mediator) and semiconducting particles, where the semiconducting particles provide for even distribution of the detection reagent(s) as the reagent composition dries on the working electrode.
  • the sample chamber region on the first substrate includes at least a portion of a working electrode surface.
  • the reagent composition is applied to all or a portion of the working electrode surface in the sample chamber region, thereby generating a modified working electrode surface in the sample chamber region on which one or more analyte detection reagents are substantially uniformly distributed.
  • the methods further comprise disposing a counter electrode on the first substrate (e.g., on region of the first substrate distinct from the region on which the working electrode is disposed), or alternatively, disposing a counter electrode on a second substrate to be overlayed on the first substrate (thereby generating a facing electrode pair).
  • Manufacturing the sensor is generally completed by overlaying a second substrate on the spacer layer and singulating individual sensors (e.g., by dye cutting, etc.) from the starting substrate material.
  • General approaches for manufacturing analyte sensors are known in the art and are described, e.g., in U.S. Patent No. 7,866,026 and U.S. Patent No. 6,592,745, the full disclosures of which are incorporated herein by reference in their entirety for all purposes.
  • the present disclosure also provides methods of manufacturing analyte sensors, which methods include forming a working electrode on a first substrate, and disposing one or more layers of conductive material (e.g., conductive microspheres) on the working electrode, where the one or more layers make up an ordered array of semiconducting particles.
  • the semiconducting particles are capable of being stacked into ordered arrays, with easily tailored surface area and void volume.
  • the number of layers of semiconducting particles may be selected to provide a desired effective surface area of the working electrode (e.g., where the effective surface area can be increased or decreased by increasing or decreasing the number of layers of semiconducting particles, respectively).
  • the size distribution of the semiconducting particles may be selected to provide a desired void volume within the array of conductive microspheres.
  • Also provided are methods of manufacturing analyte sensors which methods include forming a working electrode on a first substrate, and disposing one or more layers of semiconducting particles on the working electrode, where a number of layers of the one or more layers of semiconducting particles is selected to provide a desired effective surface area of the working electrode.
  • the one or more layers make up an ordered array of
  • the size distribution of the semiconducting particles may be selected to provide a desired void volume within the one or more layers of semiconducting particles.
  • the present disclosure provides of manufacturing analyte sensors, which methods include forming a working electrode on a first substrate, and disposing one or more layers of semiconducting particles on the working electrode, where a size distribution of the semiconducting particles is selected to provide a desired void volume within the one or more layers of semiconducting particles.
  • the number of layers of the one or more layers of semiconducting particles may be selected to provide a desired effective surface area of the working electrode.
  • the one or more layers optionally make up an ordered array of
  • the subject sensors and methods find use in a variety of different applications where, e.g., the accurate determination of an analyte concentration by an analyte sensor is desired.
  • the methods are useful for obtaining and accurately determining the concentration of one or more analytes in a bodily sample, e.g., a blood sample.
  • ATO semiconducting particles were obtained as a ca. 20%
  • FIG. 8 is a graph illustrating the effect that the inclusion of semiconducting particles in the sensor has on the active working electrode area.
  • Glucose test strips were fabricated from FreeStyle test strip halves consisting of carbon working electrodes and Ag/AgCl electrodes in a facing configuration.
  • the working electrode included surfactant, buffer, MSG and ATO nanoparticles, where present.
  • Counter reference electrodes included first and second surfactants, NaCl and a buffer.
  • the above strip halves were assembled to construct a thin-layer electrochemical cell, the strip was filled with 0.1M phosphate buffer saline (PBS), pH 7, and cyclic voltammetry was performed over the range -0.8V to +0.8V, at a scan rate of 50 mV/second (the potential of the carbon-containing strip half was scanned relative to that of the Ag/AgCl containing half).
  • the double layer charging current was evaluated from the resulting curve, using the current difference between anodic and cathodic scans at 0V.
  • the two strips with the ATO semiconducting particles (labeled "ATO strip” and "Sensor strip") showed a significant increase in double layer charging (ca.
  • the strips with ATO semiconducting particles exhibited a peak current of 99.3 ⁇ , intermediate between that of the control (84.8 ⁇ ), and the conducting particles (109.7 ⁇ ). Importantly, this value is substantially increased as compared to a strip with inert particles (virtually unchanged from control). High peak current is indicative of both well distributed chemistry and an increased electroactive area. This provides evidence that semiconducting particles increase electrode area and performance relative to both control and inert particles, while avoiding the short circuits possible with conducting particles.
  • FIG. 9 and FIG. 10 compare the fill times and reproducibility of strips incorporating ATO semiconducting particles with sensors that do not include the semiconducting particles.
  • Three strip formulations were studied that had different reagent material without semiconducting particles (A, B and C) and two strip formulations were studied that included ATO semiconducting particles in the reagent solution (D and E).
  • the designations A, B, C refer to three versions of enzyme.
  • the D and E strips contained equal amounts of ATO
  • FIG. 10 illustrates the increased reproducibility of the strips incorporating ATO semiconducting particles compared to strips that did not incorporate the semiconducting particles. The reproducibility is measured as a coefficient of variation (CV) for the glucose test result, after eight weeks at 25°C, 56°C and 65°C. After eight weeks at each of the temperatures, the CV of the strips D and E with ATO semiconducting particles remained low and nearly constant, while the sensors A, B, C without the semiconducting particles had higher CVs, particularly at 56°C and 65°C.
  • CV coefficient of variation
  • FIG. 11A illustrates the improved bias control when ATO semiconducting particles are incorporated into the strip reagent.
  • a sample was prepared using a particular enzyme and carbon, with a second sample using the same enzyme and carbon prepared with ATO particles. The samples were tested at low, middle and high glucose levels. As shown in FIG. 11 A, bias control was improved at higher glucose levels when ATO semiconducting particles were incorporated.
  • FIGs. 12A and 12B illustrate the charge results for strips with and without semiconducting particles at various levels of reagent (enzyme and mediator) loading tested at various glucose levels. Reagent loadings were varied from 40% to 100%. The counter-reference electrode formulations are unchanged from FIG. 8.
  • the non-linearity is a product of the uneven reagent deposition on the working electrode when no semiconducting particles are used. As reagent loading is decreased to 40%, this non-linearity increases substantially. The maximum charge decreased from 700 microcoulombs at 100% reagent loading to 340 microcoulombs at 40% reagent loading, both measurements taken at 350 mg/dL glucose.
  • FIG. 12B illustrates the charge results for strips with the ATO semiconducting particles at various levels of reagent loading tested at various glucose levels.
  • the ATO level was not changed.
  • Reagent loadings were varied from 40% to 100% at varying levels of glucose as in FIG. 12A.
  • linearity is nearly identical for all strips, irrelevant of the reagent loading.
  • the maximum charge only varies between 750 microcoulombs at 60% reagent loading and 800 microcoulombs at 40% reagent loading, both measurements taken at 350 mg/dL glucose.
  • the results in FIG. 1 IB indicate superior recovery at the various loadings for the strips with ATO semiconducting particles as compared with the strip without
  • FIGs. 13A and 13B illustrate the results of the tests, with FIG. 13A illustrating the precision of the sensor formulation without ATO and FIG. 13B illustrating the precision of the sensor formulation with ATO. As illustrated, the sensors using the ATO nanoparticle formulation demonstrated better precision than the sensors having the non-ATO nanoparticles formulation.
  • formulation have advantages in minimizing the performance impact from unknown carbon ink variation, printing variation and chemistry coating variation, resulting in better strip precision, better sample filling performance and potentially better yield.

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Abstract

L'invention concerne des détecteurs destinés à déterminer la concentration d'un analyte dans un échantillon fluide. Dans certains modes de réalisation, les détecteurs comprennent des particules semi-conductrices et présentent une meilleure uniformité de distribution d'un ou de plusieurs composants chimiques de détection, une plus grande zone de surface d'électrode de travail efficace et une meilleure cohérence du temps de remplissage. L'invention concerne également des procédés d'utilisation et de fabrication des détecteurs.
PCT/US2014/039175 2014-05-22 2014-05-22 Détecteurs d'analytes et leurs procédés d'utilisation WO2015178912A1 (fr)

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Cited By (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
RU2713587C1 (ru) * 2017-10-23 2020-02-05 Б-Био Ко., Лтд. Биодатчик, устойчивый к эффекту кофейного пятна

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JP2000081407A (ja) * 1998-06-25 2000-03-21 Omron Corp バイオセンサ，その製造方法及びバイオセンサを用いた測定方法
US20020189941A1 (en) * 1999-11-15 2002-12-19 Arkray, Inc. Biosensor
US20040040839A1 (en) * 2000-10-27 2004-03-04 Yuji Yagi Biosensor
US20050150763A1 (en) * 2004-01-09 2005-07-14 Butters Colin W. Biosensor and method of manufacture
US20060042361A1 (en) * 2002-11-01 2006-03-02 Arkray, Inc. Measuring instrument provided with solid composnent concentrating means

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Publication number Priority date Publication date Assignee Title
JP2000081407A (ja) * 1998-06-25 2000-03-21 Omron Corp バイオセンサ，その製造方法及びバイオセンサを用いた測定方法
US20020189941A1 (en) * 1999-11-15 2002-12-19 Arkray, Inc. Biosensor
US20040040839A1 (en) * 2000-10-27 2004-03-04 Yuji Yagi Biosensor
US20060042361A1 (en) * 2002-11-01 2006-03-02 Arkray, Inc. Measuring instrument provided with solid composnent concentrating means
US20050150763A1 (en) * 2004-01-09 2005-07-14 Butters Colin W. Biosensor and method of manufacture

Cited By (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
RU2713587C1 (ru) * 2017-10-23 2020-02-05 Б-Био Ко., Лтд. Биодатчик, устойчивый к эффекту кофейного пятна

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