Small volume in vitro analyte sensor

• US 8,123,929 B2
• Filed: 09/29/2009
• Issued: 02/28/2012
• Est. Priority Date: 02/06/1997
• Status: Expired due to Fees

• Current Assignee: Abbott Diabetes Care Incorporated (Abbott Laboratories Incorporated)
• Original Assignee: Abbott Diabetes Care Incorporated (Abbott Laboratories Incorporated)
• Inventors: Heller, Adam, Feldman, Benjamin J., Say, James, Vreeke, Mark S.
• Primary Examiner(s): Noguerola, Alex
• Application Number:
  US12/568,842
• Publication Number:
  US 20100012511A1
• Time in Patent Office: 882 Days
• Field of Search: 20440301-40315, 205/777.5, 205/778, 205/792
• US Class Current: 205/792
• CPC Class Codes: A61B 2560/0223 of calibration, e.g. protocols for calibrating sensors
• CPC Class Codes: A61B 2562/0295 Strip shaped analyte sensors for apparatus classified in A61B5/145 or A61B5/157 disposable multilayered or laminated electrodes G01N27/307; details of handling chemical test elements G01N33/4875
• CPC Class Codes: A61B 5/1411 by percutaneous method, e.g. by lancet
• CPC Class Codes: A61B 5/14532 for measuring glucose, e.g. by tissue impedance measurement
• CPC Class Codes: A61B 5/14546 for measuring analytes not otherwise provided for, e.g. ions, cytochromes
• CPC Class Codes: A61B 5/1486 using enzyme electrodes, e.g. with immobilised oxidase
• CPC Class Codes: A61B 5/14865 invasive, e.g. introduced into the body by a catheter or needle or using implanted sensors
• CPC Class Codes: A61B 5/1495 Calibrating or testing of in-vivo probes
• CPC Class Codes: A61B 5/150022 for capillary blood or interstitial fluid
• CPC Class Codes: A61B 5/150358 Strips for collecting blood, e.g. absorbent optical reagent test strips G01N21/8483; chemical reagent test strips G01N33/4875, G01N33/52
• CPC Class Codes: A61B 5/150412 Pointed piercing elements, e.g. needles, lancets for piercing the skin blade-like piercing elements A61B5/150442
• CPC Class Codes: A61B 5/150503 Single-ended needles hollow piercing element tip design A61B5/150396, needle sets for catheters A61M25/06, needles for bringing media into the body A61M5/32
• CPC Class Codes: A61B 5/15105 Purely manual piercing, i.e. the user pierces the skin without the assistance of any driving means or driving devices
• CPC Class Codes: A61B 5/15113 Manually triggered, i.e. the triggering requires a deliberate action by the user such as pressing a drive button
• CPC Class Codes: A61B 5/15144 comprising driving means, e.g. a spring, for retracting the piercing unit into the housing
• CPC Class Codes: A61B 5/157 Devices characterised by integrated means for measuring characteristics of blood
• CPC Class Codes: C12Q 1/001 Enzyme electrodes
• CPC Class Codes: C12Q 1/004 mediator-assisted
• CPC Class Codes: C12Q 1/006 for glucose
• CPC Class Codes: G01N 2333/904 acting on CHOH groups as donors, e.g. glucose oxidase, lactate dehydrogenase (1.1)
• CPC Class Codes: G01N 27/3272 : Test elements therefor, i.e. disposable laminated substrates with electrodes, reagent and channels optical biosensors G01N33/52
• CPC Class Codes: G01N 27/3273 : Devices therefor, e.g. test element readers, circuitry details not specific to biochemical electrodes G01N33/4875
• CPC Class Codes: G01N 33/5438 : Electrodes

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.

Claims

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.

2. The method of claim 1, wherein the step of transporting comprises contacting the sample with the electrochemical sensor, wherein the working electrode and counter electrode are separated by a closest distance of about 40 μ

m.

3. The method of claim 1, wherein the step of transporting comprises contacting the sample with the electrochemical sensor, wherein the electrode pair has the working electrode disposed on a first substrate and the counter electrode disposed on the first substrate.

4. The method of claim 1, wherein the step of generating a sensor signal at the working electrode within the measurement period comprises:

generating a sensor signal at the working electrode within the measurement period, wherein the background signal that is generated by electrolysis of a buffer solution comprising no glucose is no more than about 14% of the signal generated by electrolysis of a buffer solution comprising 10 mM glucose.

5. The method of claim 1, wherein the analyte-responsive enzyme comprises glucose oxidase or glucose dehydrogenase.

6. The method of claim 1, wherein the redox mediator comprises osmium complex, a ferrocyanide, or a ferricyanide.

7. The method of claim 1, wherein the working electrode is constructed of a material selected from gold, carbon, platinum, ruthenium dioxide and palladium.

8. A method for determining a concentration of an analyte in a sample, comprising the steps of:

(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.

9. The method of claim 8, wherein the analyte-responsive enzyme comprises glucose oxidase or glucose dehydrogenase.

10. The method of claim 8, wherein the sample chamber is sized to contain a volume of no more than about 0.2 μ

L of the sample.

11. The method of claim 8, wherein the sample chamber is sized to contain a volume of no more than about 0.1 μ

L of the sample.

12. The method of claim 8, wherein the redox mediator comprises osmium complex, a ferrocyanide, or a ferricyanide.

13. The method of claim 8, wherein the analyte-responsive enzyme comprises glucose oxidase or glucose dehydrogenase.