Sensor Calibration

• US 20130083820A1
• Filed: 11/27/2012
• Published: 04/04/2013
• Est. Priority Date: 05/27/2011
• Status: Active Grant

• Current Assignee: Baxter Healthcare SA (Baxter International Inc.), Baxter International Inc.
• Original Assignee: Lightship Medical Limited
• Inventors: Mackenzie, Alasdair Allan, Paterson, William, Crane, Barry Colin, Barwell, Nicholas Paul, Edgley, Peter
• Granted Patent: US 8,607,612 B2
• Time in Patent Office: Days
• US Class Current: 374/1
• CPC Class Codes: G01K 15/005 Calibration
• CPC Class Codes: G01N 33/5438 Electrodes
• CPC Class Codes: G01N 33/582 with fluorescent label
• CPC Class Codes: G01N 33/66 involving blood sugars, e.g. galactose

Abstract

A method of calibrating a reversible-binding sensor for detecting an analyte includes:

• • (i) varying the temperature of a first calibration solution from a first temperature (T₁) to a second temperature (T₂) while the first calibration solution is in contact with a sensing region of the sensor;
  • (ii) determining the sensor output for the first calibration solution as a function of temperature;
  • (iii) varying the temperature of a second calibration solution from a third temperature (T₃) to a fourth temperature (T₄) while the second calibration solution is in contact with the sensing region, the second calibration solution having a concentration of analyte which is different from that of the first calibration solution;
  • (iv) determining the sensor output for the second calibration solution as a function of temperature; and
  • (v) using the determined sensor output from steps (ii) and (iv) to calibrate the sensor.

Claims

1. A method of calibrating a reversible-binding sensor for detecting an analyte, which method comprises:

varying the temperature of a first calibration solution from a first temperature (T₁) to a second temperature (T₂) while the first calibration solution is in contact with a sensing region of the sensor;

(ii) determining the sensor output for the first calibration solution as a function of temperature;

(iii) varying the temperature of a second calibration solution from a third temperature (T₃) to a fourth temperature (T₄) while the second calibration solution is in contact with the sensing region, the second calibration solution having a concentration of analyte which is different from that of the first calibration solution;

(iv) determining the sensor output for the second calibration solution as a function of temperature; and

(v) using the determined sensor output from steps (ii) and (iv) to calibrate the sensor.

2. A method according to claim 1, which further comprises:

(vi) varying the temperature of a third calibration solution from a fifth temperature (T₅) to a sixth temperature (T₆) while the third calibration solution is in contact with the sensing region, the third calibration solution having a concentration of analyte which is different from those of the first and second calibration solutions; and

(vii) determining the sensor output for the third calibration solution as a function of temperature;

wherein step (v) comprises using the determined sensor output from steps (ii), (iv) and (vii) to calibrate the sensor.

3. A method according to claim 1, wherein T₂ is greater than T₁, T₄ is greater than T₃, and, when steps (vi) and (vii) are used, T₆ is greater than T₅.

4. A method according to claim 3, wherein T₃ is less than or equal to T₂, and, when steps (vi) and (vii) are used, and T₅ is less than or equal to T₄.

5. A method according to claim 1, wherein the second calibration solution is formed by mixing the first calibration solution with an amount of analyte, and, when steps (vi) and (vii) are used, the third calibration solution is formed by mixing the second calibration solution with a further amount of analyte.

6. A method according to claim 1, wherein the concentration of analyte in the first calibration solution is zero.

7. A method according to claim 1, wherein the sensor is an optical sensor.

8. A method according to claim 1, wherein the analyte is glucose.

9. A method according to claim 8, wherein a first amount of glucose is mixed with the first calibration solution to form the second calibration solution and, when steps (vi) and (vii) are used, a second amount of glucose is mixed with the second calibration solution to form the third calibration solution, wherein said first and second amounts of glucose are provided in solid form, which solid form comprises alpha and beta glucose.

10. A method according to claim 1, wherein the analyte reversibly binds to a receptor within the sensing region of the sensor at an analyte:

receptor ratio of 1;

1.

11. A method according to claim 10, wherein the analyte is glucose and the receptor comprises a boronic acid species.

12. A method according to claim 1, which further comprises

(viii) contacting the sensing region of the sensor with a sample and

determining the concentration of analyte in the sample;

wherein the time between step (i) being carried out and step (viii) being carried out is 24 hours or less.

13. A method according to claim 1, wherein the sensor to be calibrated is provided as part of a kit, the kit further comprising a calibration chamber and a temperature controller.

14. A method according to claim 13, wherein

the first calibration solution is present in a first compartment of the calibration chamber,

an amount of analyte is present in a second compartment of the calibration chamber,

the second compartment of the calibration chamber is initially separated from the first compartment of the calibration chamber by a water-impermeable first dividing material, and

wherein said method comprises breaking or removing the first dividing material to form the second calibration solution.

15. A method according to claim 14, wherein

the calibration chamber comprises a third compartment containing a further amount of the analyte,

the third compartment is initially separated from the remainder of the calibration chamber by a second water-impermeable dividing material, and

wherein said method comprises breaking or removing the second dividing material to form the third calibration solution.

16. A method according to claim 1, wherein the analyte reversibly binds to the receptor at an analyte:

receptor ratio of 1;

1, and step (ii) comprises;

a. fitting two or more temperatures in a temperature range from T₁ to T₂ to the following equation;

I=I₁+s₁(T−

T_c)

wherein I is the sensor output, T is the temperature, T_c is the nominal calibration temperature, I₁ is the sensor output for the first calibration solution at T_c, and S₁ is a constant; and

b. determining s₁;

step (iv) comprises

a. fitting two or more temperatures in a temperature range from T₃ to T₄ to the following equation;

I=I₂+s₂(T−

T_c)

wherein I, T, and T_c, are as defined above, I₂ is the sensor output for the second calibration solution at T_c, and s₂ is a constant; and

b. determining s₂;

step (v) comprises

a. determining the values of temperature coefficients α and

β

using the following equations;

17. A method according to claim 13, wherein the kit further comprises one or more control modules, said one or more control modules being configured to contact the sensing region of the sensor with consecutive calibration solutions;

monitor and/or adjust the temperature of the calibration solutions;

determine sensor output as a function of temperature; and

calibrate the sensor, wherein steps (i) to (v), and, when used, steps (vi) and (vii), are carried out using the control module.

18. A calibration system comprising one or more control modules, wherein the one or more control modules are configured to contact the sensing region of a reversible binding sensor with consecutive calibration solutions;

monitor or adjust the temperature of the calibration solutions; and

determine sensor output of said sensor as a function of temperature for each of said calibration solutions.

19. A calibration system according to claim 18, wherein said one or more control modules are further configured to calibrate the sensor.

20. A calibration system according to claim 18, wherein the one or more control modules are configured to carry out a method comprising:

(i) varying the temperature of a first calibration solution from a first temperature (T1) to a second temperature (T2) while the first calibration solution is in contact with a sensing region of the sensor;

(ii) determining the sensor output for the first calibration solution as a function of temperature;

(iii) varying the temperature of a second calibration solution from a third temperature (T3) to a fourth temperature (T4) while the second calibration solution is in contact with the sensing region, the second calibration solution having a concentration of analyte which is different from that of the first calibration solution;

(iv) determining the sensor output for the second calibration solution as a function of temperature; and

(v) using the determined sensor output from steps (ii) and (iv) to calibrate the sensor.

21. A calibration system according to claim 18, further comprising at least one calibration chamber.

22. A calibration system according to claim 18, further comprising a reversible binding sensor for detecting an analyte.