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.
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Citations
54 Claims
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1-11. -11. (canceled)
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12. A sensor for determining the concentration of an analyte 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, wherein the working electrode is formed from a molded carbon fiber composite or comprises an inert non-conducting base material upon which a conducting layer is deposited selected from gold, carbon, platinum, ruthenium dioxide, palladium, and conductive epoxies, and wherein the counter electrode is Ag/AgCl or Ag/AgBr printed on a non-conducting base material or silver chloride on a silver metal base;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; andan analyte-responsive enzyme 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 analyte. - View Dependent Claims (13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25, 26, 27, 28, 29, 30, 31, 32, 33, 34, 35, 36, 37, 38, 39)
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40. A method for determining a concentration of an analyte in a sample, 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, wherein the working electrode is formed from a molded carbon fiber composite or comprises an inert non-conducting base material upon which a conducting layer is deposited selected from gold, carbon, platinum, ruthenium dioxide, palladium, and conductive epoxies, and wherein the counter electrode is Ag/AgCl or Ag/AgBr printed on a non-conducting base material or silver chloride on a silver metal base;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; andan analyte-responsive enzyme 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 analyte;generating a sensor signal at the working electrode, and determining the concentration of the analyte using the sensor signal. - View Dependent Claims (41, 42, 43, 44, 45, 46, 47, 48)
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49. A method for determining a concentration of an analyte 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, wherein the working electrode is formed from a molded carbon fiber composite or comprises an inert non-conducting base material upon which a conducting layer is deposited selected from gold, carbon, platinum, ruthenium dioxide, palladium, and conductive epoxies, and wherein the counter electrode is Ag/AgCl or Ag/AgBr printed on a non-conducting base material or silver chloride on a silver metal base;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; andan analyte-responsive enzyme 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 analyte;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 analyte in the sample; generating an analyte -responsive signal from the sensor in response to electrolysis of the analyte in the sample; and determining the concentration of the analyte using the analyte-responsive signal.
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50. A method of manufacturing a sensor, the method comprising:
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(a) forming a plurality of working electrodes on a first substrate, wherein the working electrode is formed from a molded carbon fiber composite or comprises an inert non-conducting base material upon which a conducting layer is deposited selected from gold, carbon, platinum, ruthenium dioxide, palladium, and conductive epoxies; (b) forming a plurality of counter electrodes on a second substrate, wherein the counter electrode is Ag/AgCl or Ag/AgBr printed on a non-conducting base material or silver chloride on a silver metal base; (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; andan analyte-responsive enzyme 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 analyte. - View Dependent Claims (51, 52, 53, 54)
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Specification