Electrochemical sensor and method for continuous analyte monitoring

• US 20050211572A1
• Filed: 01/19/2005
• Published: 09/29/2005
• Est. Priority Date: 09/20/1999
• Status: Active Grant

• Current Assignee: Roche Diabetes Care Inc. (Roche Holding AG)
• Original Assignee: Roche Diagnostics Operations Incorporated (Roche Holding AG)
• Inventors: Essenpreis, Matthias, Buck, Harvey B.
• Granted Patent: US 7,731,835 B2
• Time in Patent Office: Days
• US Class Current: 205/778
• CPC Class Codes: A61B 5/14532 for measuring glucose, e.g. by tissue impedance measurement
• CPC Class Codes: A61B 5/1486 using enzyme electrodes, e.g. with immobilised oxidase
• CPC Class Codes: C12Q 1/001 Enzyme electrodes
• CPC Class Codes: C12Q 1/004 mediator-assisted
• CPC Class Codes: C12Q 1/006 for glucose

Abstract

Sensors and a method for detecting an analyte are described. Sensors each have a volume of a hydrophilic medium that retains an amount of analyte proportionate to the concentration of analyte in a biological fluid, electrodes and a redox enzyme in contact with medium, and an electron transfer mediator. The fluid contacts sensors and at initially predetermined intervals intermittently applies a potential to electrode sufficient to oxidize the mediator and sensing current through electrode as a function of the duration of the applied potential. The applied mediator oxidizing applied potential is maintained for a period of time sufficient to determine the rate of change of current with time through electrode. The current flow is correlated with the current flow for known concentrations of the analyte in medium.

Claims

1. A method for monitoring analyte concentration in a biological fluid by use of a sensor, the method comprising the steps of:

providing a sensor comprising a volume of a hydrophilic medium for retaining an amount of analyte proportionate to the concentration of analyte in a biological fluid in contact with the sensor, an enclosure for said analyte retention volume, an electrode in contact with the hydrophilic medium, a redox enzyme in contact with the medium, and an electron transfer mediator for facilitating transfer of electrons between the enzyme and the electrode, the enzyme substantially not capable of transferring electrons to or from components of the biological fluid other than said analyte,

contacting the biological fluid with the sensor and at initially predetermined intervals intermittently applying a potential to the electrode sufficient to oxidize the electron mediator and sensing current through said electrode as a function of the duration of the applied potential,

maintaining the applied mediator oxidizing applied potential at least for a period of time sufficient to determine the rate of change of current with time through the electrode, and

correlating the current flow with the current flow for known concentrations of said analyte in the retention medium.

2. The method of claim 1 wherein the intervals between the intermittent applied potentials are less than the time necessary for the concentration of the analyte in the retention volume to equilibrate with that in the biological fluids in contact with the enclosure.

3. The method of claim 1 further comprising the step of applying a potential to the electrode sufficient to reduce the oxidized form of the electron mediator.

4. The method of claim 1, wherein the sensor additionally comprises at least a reference electrode and an auxiliary electrode and further comprising the steps of intermittently establishing predetermined level of current to flow between said working electrode and said auxiliary electrode at initially predetermined intervals, and measuring the potential difference between said working electrode and the reference electrode to establish said level of current flow;

maintaining said level of current flow at least for a period of time sufficient to determine the rate of change of potential necessary to maintain said current through said electrode with time, and correlating said potential with the potential for known concentrations of said analyte in the biological fluid.

5. The method of claim 4 wherein the intervals between the intermittent potential measurements are less than the time necessary for the concentration of the analyte in the retention volume to equilibrate with that in the biological fluids in contact with the enclosure.

6. The method of claim 4 wherein the intervals are increased incrementally and the concentration of the analyte in the biological fluid is determined as a function of the rate of increase in analyte concentration in the retention volume.