Small volume in vitro analyte sensor
First Claim
1. A method for determining a concentration of glucose in a sample, comprising the steps of:
- (a) transporting a body fluid sample of no more than about 500 nl into an electrochemical sensor comprising;
(i) an electrode pair comprising a working electrode and a reference electrode or a counter electrode, wherein the working electrode and reference electrode or counter electrode are separated by a closest distance in a range of 25 to 1000 μ
m;
(ii) a sample chamber comprising the working electrode and the reference electrode or counter electrode, wherein the sample chamber is sized to contain a volume of no more than about 500 nl of the sample; and
(iii) an analyte-responsive enzyme and a redox mediator disposed in the sample chamber;
(b) holding the sample in the sample chamber in a non-flow through manner;
(c) generating a sensor signal at the working electrode within a measurement period of no greater than about 1 minute, wherein the background signal that is generated by electrolysis of a buffer solution comprising no glucose is no more than about 26% of the signal generated by electrolysis of a buffer solution comprising 6 mM glucose; and
(d) determining by coulometry the concentration of the glucose using the sensor signal.
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Accused Products
Abstract
A sensor designed to determine the amount and concentration of analyte in a sample having a volume of less than about 1 μL. The sensor has a working electrode coated with a non-leachable redox mediator. The redox mediator acts as an electron transfer agent between the analyte and the electrode. In addition, a second electron transfer agent, such as an enzyme, can be added to facilitate the electrooxidation or electroreduction of the analyte. The redox mediator is typically a redox compound bound to a polymer. The preferred redox mediators are air-oxidizable.
The amount of analyte can be determined by coulometry. One particular coulometric technique includes the measurement of the current between the working electrode and a counter or reference electrode at two or more times. The charge passed by this current to or from the analyte is correlated with the amount of analyte in the sample. Other electrochemical detection methods, such as amperometric, voltammetric, and potentiometric techniques, can also be used.
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. An enzyme capable of catalyzing the electrooxidation or electroreduction of the biomolecule is provided as a second electron transfer agent.
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Citations
13 Claims
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1. A method for determining a concentration of glucose in a sample, comprising the steps of:
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(a) transporting a body fluid sample of no more than about 500 nl into an electrochemical sensor comprising; (i) an electrode pair comprising a working electrode and a reference electrode or a counter electrode, wherein the working electrode and reference electrode or counter electrode are separated by a closest distance in a range of 25 to 1000 μ
m;(ii) a sample chamber comprising the working electrode and the reference electrode or counter electrode, wherein the sample chamber is sized to contain a volume of no more than about 500 nl of the sample; and (iii) an analyte-responsive enzyme and a redox mediator disposed in the sample chamber; (b) holding the sample in the sample chamber in a non-flow through manner; (c) generating a sensor signal at the working electrode within a measurement period of no greater than about 1 minute, wherein the background signal that is generated by electrolysis of a buffer solution comprising no glucose is no more than about 26% of the signal generated by electrolysis of a buffer solution comprising 6 mM glucose; and (d) determining by coulometry the concentration of the glucose using the sensor signal. - View Dependent Claims (2, 3, 4, 5, 6, 7)
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8. A method for determining a concentration of an analyte in a sample, comprising the steps of:
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(a) transporting a biological fluid sample of no more than 500 nl into an electrochemical sensor comprising; (i) an electrode pair comprising a working electrode and a reference electrode or a counter electrode, wherein the working electrode and reference electrode or counter electrode are separated by a closest distance in a range of 25 to 1000 μ
m;(ii) a sample chamber comprising the working electrode and the counter electrode, wherein sample chamber is sized to contain a volume of no more than about 500 nl of the sample; and (iii) an analyte-responsive enzyme and a redox mediator disposed in the sample chamber; (b) holding the sample in the sample chamber in a non-flow through manner; (c) generating a sensor signal at the working electrode within a measurement period of no greater than about 1 minute, wherein a background signal that is generated by electrolysis of a buffer solution comprising no analyte is no more than about 26% of the signal generated by electrolysis of a buffer solution comprising 6 mM analyte; and (d) determining by coulometry the concentration of the analyte using the sensor signal. - View Dependent Claims (9, 10, 11, 12, 13)
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Specification