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.
103 Citations
52 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 the working electrode and counter electrode are separated by an effective distance in a range of 25 to 1000 μ
m;a sample chamber for holding the sample fluid, the sample chamber comprising a measurement zone positioned adjacent to the working electrode and the counter electrode, wherein the measurement zone and the sample chamber are sized to contain a volume of no more than about 1 μ
L of the sample; andglucose dehydrogenase and a diffusible redox mediator disposed in the measurement zone;
the sensor having been configured and arranged so that a background signal generated by the diffusible redox mediator is no more than the signal generated by oxidation or reduction of the average normal physiological amount of glucose. - View Dependent Claims (13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25, 26, 27, 28, 29, 31, 32, 33, 34, 35, 36, 37)
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31-1. The sensor of claim 12, wherein the sensor comprises a molar amount of the redox mediator that is, on a stoichiometric basis, no more than an average normal physiological amount of the glucose and, preferably, the sensor comprises a molar amount of the redox mediator that is, on a stoichiometric basis, no more than 20% of an average normal physiological amount of the glucose.
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38. A method for determining a concentration of glucose in a sample, comprising the steps of:
contacting a sample with a sensor, wherein the sensor comprises; an electrode pair comprising a working electrode, and a counter electrode, wherein the working electrode and counter electrode are separated by an effective distance in a range of 25 to 1000 μ
m;a sample chamber for holding the sample fluid, the sample chamber comprising a measurement zone positioned adjacent to the working electrode and the counter electrode, wherein the measurement zone and the sample chamber are sized to contain a volume of no more than about 1 μ
L of the sample; andglucose dehydrogenase and a diffusible redox mediator disposed in the measurement zone;
the sensor having been configured and arranged so that a background signal generated by the diffusible redox mediator is no more than the signal generated by oxidation or reduction of the average normal physiological amount of glucose;
generating a sensor signal at the working electrode, and determining the concentration of the glucose using the sensor signal.- View Dependent Claims (39, 40, 41, 42, 43, 44, 45, 46)
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47. A method for determining a concentration of glucose in a sample, the method comprising the steps of:
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contacting a sample with a sensor, wherein the sensor comprises; an electrode pair comprising a working electrode, and a counter electrode, wherein the working electrode and counter electrode are separated by an effective distance in a range of 25 to 1000 μ
m;a sample chamber for holding the sample fluid, the sample chamber comprising a measurement zone positioned adjacent to the working electrode and the counter electrode, wherein the measurement zone and the sample chamber are sized to contain a volume of no more than about 1 μ
L of the sample; andglucose dehydrogenase and a diffusible redox mediator disposed in the measurement zone;
the sensor having been configured and arranged so that a background signal generated by the diffusible redox mediator is no more than the signal generated by oxidation or reduction of the average normal physiological amount of glucose;observing a signal from an indicator electrode to signify that the measurement zone contains sample; applying a potential between the working electrode and the counter electrode to electrolyze the glucose in the sample; generating an glucose-responsive signal from the sensor in response to electrolysis of the glucose in the sample; and determining the concentration of the glucose using the glucose-responsive signal.
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48. A method of manufacturing a sensor, the method comprising:
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(a) forming a plurality of working electrodes on a first substrate; (b) forming a plurality of counter electrodes on a second substrate; (c) disposing a spacer layer on one of the first and second substrates; (d) removing a portion of the spacer layer to define sample chamber regions; (e) laminating the first and second substrates together; and (f) separating a plurality of electrochemical sensors from the laminated substrates, wherein each sensor, comprises; an electrode pair comprising a working electrode, and a counter electrode, wherein the working electrode and counter electrode are separated by an effective distance in a range of 25 to 1000 μ
m;a sample chamber for holding the sample fluid, the sample chamber comprising a measurement zone positioned adjacent to the working electrode and the counter electrode, wherein the measurement zone and the sample chamber are sized to contain a volume of no more than about 1 μ
L of the sample; andglucose dehydrogenase and a diffusible redox mediator disposed in the measurement zone;
the sensor having been configured and arranged so that a background signal generated by the diffusible redox mediator is no more than the signal generated by oxidation or reduction of the average normal physiological amount of glucose. - View Dependent Claims (49, 50, 51, 52)
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Specification