Small Volume In Vitro Sensor and Methods of Making
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Abstract
A sensor utilizing a non-leachable or diffusible redox mediator is described. The sensor includes a sample chamber to hold a sample in electrolytic contact with a working electrode, and in at least some instances, the sensor also contains a non-leachable or a diffusible second electron transfer agent. The sensor and/or the methods used produce a sensor signal in response to the analyte that can be distinguished from a background signal caused by the mediator. The invention can be used to determine the concentration of a biomolecule, such as glucose or lactate, in a biological fluid, such as blood or serum, using techniques such as coulometry, amperometry, and potentiometry. An enzyme capable of catalyzing the electrooxidation or electroreduction of the biomolecule is typically provided as a second electron transfer agent.
16 Citations
82 Claims
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1-11. -11. (canceled)
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12. A sensor for determining the concentration of glucose in a sample fluid, the sensor comprising:
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an electrode pair comprising a working electrode and a counter electrode, wherein at least a portion of the working electrode is within a distance of no more than 200 μ
m of a portion of the counter electrode;a measurement zone positioned adjacent to the working electrode and counter electrode, wherein the measurement zone is sized to contain a volume of no more than about 1 μ
L of sample;a reference electrode disposed in contact with the measurement zone; and an FAD-dependent glucose dehydrogenase and a diffusible redox mediator disposed in the measurement zone; wherein the sensor is configured and arranged so that a half-wave potential of the redox mediator, as measured by cyclic voltammetry in 0.1 M NaCl at pH 7, is no more than about +100 millivolts relative to the potential of the reference electrode. - View Dependent Claims (13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25, 26, 27, 28, 29)
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30. A method for determining a concentration of a glucose in a sample, comprising the steps of:
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contacting a sample with an electrochemical sensor comprising an electrode pair comprising a working electrode and a counter electrode, wherein at least a portion of the working electrode is within a distance of no more than 200 μ
m of a portion of the counter electrode;a measurement zone positioned adjacent to the working electrode and counter electrode, wherein the measurement zone is sized to contain a volume of no more than about 1 μ
L of sample; andan FAD-dependent glucose dehydrogenase and a diffusible redox mediator disposed in the measurement zone; deterring transport of the diffusible redox mediator between the working electrode and the counter electrode; generating a sensor signal at the working electrode, wherein a background signal that is generated by the diffusible redox mediator is no more than five times a signal generated by oxidation or reduction of an average normal physiological amount of glucose, and determining the concentration of the glucose using the sensor signal. - View Dependent Claims (31, 32, 33, 34, 35, 36, 37)
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38. A sensor for determining the concentration of glucose in a sample fluid, the sensor comprising:
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an electrode pair comprising a working electrode and a counter electrode, wherein at least a portion of the working electrode is within a distance of no more than 200 μ
m of a portion of the counter electrode;a measurement zone positioned adjacent to the working electrode and counter electrode, wherein the measurement zone is sized to contain a volume of no more than about 1 μ
L of sample; anda glucose-responsive enzyme and a diffusible redox mediator disposed in the measurement zone; wherein a background signal generated by the diffusible redox mediator at no more than five times a signal generated by oxidation or reduction of 5 mM glucose.
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39. A sensor for determining the concentration of a glucose in a sample fluid, the sensor comprising:
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an electrode pair comprising a working electrode and a counter electrode, wherein at least a portion of the working electrode is within a distance of no more than 200 μ
m of a portion of the counter electrode;a measurement zone positioned adjacent to the working electrode and counter electrode, wherein the measurement zone is sized to contain a volume of no more than about 1 μ
L of sample; andan FAD-dependent glucose dehydrogenase and a diffusible redox mediator disposed in the measurement zone; wherein a background signal generated by the diffusible redox mediator at no more than five times a signal generated by oxidation or reduction of an average normal physiological amount of glucose. - View Dependent Claims (40, 41, 42, 43, 44, 45, 46, 47, 48, 49, 50, 51, 52, 53, 54, 55, 56, 57, 58, 59, 60, 61, 62, 63, 64, 65, 66, 67, 68, 69)
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70. A sensor for determining the concentration of a glucose in a sample fluid, the sensor comprising:
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an electrode pair comprising a working electrode and a counter electrode, wherein at least a portion of the working electrode is within a distance of no more than 200 μ
m of a portion of the counter electrode;a measurement zone positioned adjacent to the working electrode and counter electrode, wherein the measurement zone is sized to contain a volume of no more than about 1 μ
L of sample;a reference electrode disposed in contact with the measurement zone; and an FAD-dependent glucose dehydrogenase and a diffusible redox mediator disposed in the measurement zone; wherein the sensor is configured and arranged so that the redox mediator reduces the glucose and the half-wave potential of the redox mediator, as measured by cyclic voltammetry in 0.1 M NaCl at pH 7, is no less than about −
100 millivolts relative to the potential of the reference electrode. - View Dependent Claims (71, 72, 73, 74, 75, 76, 77, 78, 79, 80, 81, 82)
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Specification