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.
17 Citations
37 Claims
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1-11. -11. (canceled)
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12. A method for determining a concentration of a ketone in a sample, comprising the steps of:
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(a) contacting a sample with an electrochemical sensor comprising; (i) an electrode pair comprising a working electrode and a counter electrode, wherein the working electrode and counter electrode are separated by a closest distance in a range of 200 to 1000 μ
m;(ii) a measurement zone positioned adjacent to the working electrode and the counter electrode, wherein the measurement zone is sized to contain a volume of no more than about 1 μ
L of the sample; and(iii) a ketone-responsive enzyme and a diffusible redox mediator disposed in the measurement zone; (b) generating a sensor signal at the working electrode within a measurement period of no greater than about 5 minutes, wherein a background signal that is generated by the redox mediator is no more than five times a signal generated by oxidation or reduction of 5 mM of ketone; and (c) determining the concentration of the ketone using the sensor signal. - View Dependent Claims (13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24)
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25. A method for determining a concentration of ketone in a sample, comprising the steps of:
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(a) contacting a sample with an electrochemical sensor comprising; (i) a working electrode and a counter electrode, wherein the working electrode and counter electrode are separated by a closest distance no greater than 1000 μ
m;(ii) a measurement zone positioned adjacent to the working electrode and the counter electrode, wherein the measurement zone is sized to contain a volume of no more than about 1 μ
L of the sample; and(iii) a ketone-responsive enzyme and a diffusible redox mediator disposed in the measurement zone; (b) generating a sensor signal at the working electrode within a measurement period, wherein a background signal that is generated by the redox mediator is no more than five times a signal generated by oxidation or reduction of an average normal physiological amount of ketone; and (c) determining the concentration of the ketone by amperometry using the sensor signal. - View Dependent Claims (26, 27, 28)
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29. A method for determining a concentration of a ketone in a sample, comprising the steps of:
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(a) contacting a sample with an electrochemical sensor comprising; (i) an electrode pair comprising a working electrode and a counter electrode, wherein the working electrode and counter electrode are separated by a closest distance in a range of 200 to 1000 μ
m;(ii) a measurement zone positioned adjacent to the working electrode and the counter electrode, wherein the measurement zone is sized to contain a volume of no more than about 1 μ
L of the sample; and(iii) a ketone-responsive enzyme and a diffusible redox mediator disposed in the measurement zone; (b) generating a sensor signal at the working electrode within a measurement period, wherein a background signal that is generated by the redox mediator is no more than five times a signal generated by oxidation or reduction of an average normal physiological amount of ketone; and (c) determining the concentration of the ketone using the sensor signal. - View Dependent Claims (30, 31, 32, 33, 34, 35, 36, 37)
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Specification