Differentiating analytes detected using fast scan cyclic voltammetry

• US 9,841,403 B2
• Filed: 07/23/2012
• Issued: 12/12/2017
• Est. Priority Date: 07/21/2011
• Status: Active Grant

• Current Assignee: Mayo Foundation For Medical Education And Research (Mayo Clinic)
• Original Assignee: Mayo Foundation For Medical Education And Research (Mayo Clinic)
• Inventors: Lee, Kendall H., Jang, Dong-Pyo, Kim, Inyong
• Primary Examiner(s): Weston, Tiffany
• Application Number:
  US13/555,965
• Publication Number:
  US 20130023745A1
• Time in Patent Office: 1,968 Days
• Field of Search: 600345, 600347, 600365
• CPC Class Codes: A61B 5/1473 invasive, e.g. introduced into the body by a catheter A61B5/1482 takes precedence
• CPC Class Codes: A61B 5/6868 Brain
• CPC Class Codes: G01N 27/48 using polarography, i.e. measuring changes in current under a slowly-varying voltage

Abstract

This document provides methods and materials involved in differentiating analytes detected using a FSCV method. For example, methods and materials for using paired pulse voltammetry to discriminate analytes based on their adsorption characteristics to an electrode (e.g., a carbon fiber electrode) are provided.

Claims

1. A system for assessing a characteristic of an analyte in an environment, the system comprising:

a set of electrodes, including a working electrode and a reference electrode;

a controller configured to vary an electrical potential applied between the working electrode and the reference electrode according to a binary waveform while the set of electrodes are located in the environment, wherein the binary waveform includes;

(i) a primary pulse that spans a first time interval, and

(ii) a secondary pulse that spans a second time interval following the first time interval;

a data acquisition apparatus configured to record;

(i) a primary data set that includes a first plurality of samples acquired over the first time interval, each sample indicating a respective level of electrical current measured at the working electrode at a corresponding time at which the sample was acquired, and

(ii) a secondary data set that includes a second plurality of samples acquired over the second time interval, each sample indicating a respective level of electrical current measured at the working electrode at a corresponding time at which the sample was acquired;

a computing system, including one or more processors, configured to perform operations comprising;

generating, using the primary data set, a first voltammogram that characterizes a response to the primary pulse at the working electrode over the first time interval;

generating, using the secondary data set, a second voltammogram that characterizes a response to the secondary pulse at the working electrode over the second time interval;

generating a difference voltammogram by determining a respective difference between the first voltammogram and the second voltammogram at corresponding times between the first time interval and the second time interval; and

determining the characteristic of the analyte in the environment using the difference voltammogram.

2. The system of claim 1, wherein the controller is further configured to repeatedly vary the electrical potential applied between the working electrode and the reference electrode according to the binary waveform while the set of electrodes are located in the environment at a frequency defined by a repetition time interval.

3. The system of claim 2, wherein the controller holds the electrical potential applied between the working electrode and the reference electrode at a base level from the end of the secondary pulse of a first binary waveform to the start of the primary pulse of a second binary waveform that immediately follows the first binary waveform.

4. The system of claim 2, wherein the repetition time interval is selected from a range of about 30 milliseconds to about 1000 milliseconds.

5. The system of claim 2, wherein the primary pulses of each of a series of successive binary waveforms that the controller applies as electrical potentials between the working electrode and the reference electrode are identical, wherein the secondary pulses of each of the series of successive binary waveforms are identical.

6. The system of claim 1, wherein the binary waveform further includes a gap time interval between the first time interval and the second time interval during which the electrical potential applied between the working electrode and the reference electrode is held at a baseline level to separate the primary pulse from the secondary pulse.

7. The system of claim 6, wherein:

a primary pulse effective repetition time interval identifies a time lapse between the start of the secondary pulse of a first binary waveform and the start of the primary pulse of a second binary waveform that immediately follows the first binary waveform; and

the primary pulse effective repetition time interval is greater than the gap time interval.

8. The system of claim 6, wherein the gap time interval is selected from a range of about 1 millisecond to about 100 milliseconds.

9. The system of claim 1, wherein the primary pulse is shaped such that the electrical potential applied between the working electrode and the reference electrode during the primary pulse ascends from a baseline level to a peak level and then descends from the peak level to the baseline level.

10. The system of claim 9, wherein the baseline level of the electrical potential applied between the working electrode and the reference electrode is −

0.4 Volts, wherein the peak level of the electrical potential applied between the working electrode and the reference electrode is 1.5 Volts.

11. The system of claim 9, wherein the primary pulse is a triangle waveform that (i) ramps up at a constant rate from the baseline level of electrical potential to the peak level of electrical potential and (ii) ramps down at a constant rate from the peak level of electrical potential to the baseline level of electrical potential.

12. The system of claim 1, wherein the primary pulse of the binary waveform is identical to the secondary pulse of the binary waveform.

13. The system of claim 1, wherein the environment is a brain of a mammal, wherein the analyte is dopamine or adenosine.

14. The system of claim 1, wherein determining the characteristic of the analyte in the environment comprises determining a concentration of the analyte in the environment.

15. A method, comprising:

applying an electrical potential between a working electrode and a reference electrode that are located in a solution that contains an analyte;

varying the electrical potential between the working electrode and the reference electrode according to a binary waveform that includes;

(i) a primary pulse that spans a first time interval, and

(ii) a secondary pulse that spans a second time interval following the first time interval;

obtaining a primary data set and a secondary data set, wherein;

(i) the primary data set includes a first plurality of samples acquired over the first time interval, each sample indicating a respective level of electrical current measured at the working electrode at a corresponding time at which the sample was acquired, and

(ii) the secondary data set includes a second plurality of samples acquired over the second time interval, each sample indicating a respective level of electrical current measured at the working electrode at a corresponding time at which the sample was acquired;

generating, by a computing system and using the primary data set, a first voltammogram that characterizes a response to the primary pulse at the working electrode over the first time interval;

generating, by the computing system and using the secondary data set, a second voltammogram that characterizes a response to the secondary pulse at the working electrode over the second time interval;

generating a difference voltammogram by determining a respective difference between the first voltammogram and the second voltammogram at corresponding times between the first time interval and the second time interval; and

determining the characteristic of the analyte in the environment using the difference voltammogram.

16. The method of claim 15, wherein the binary waveform further includes a gap time interval between the first time interval and the second time interval during which the electrical potential applied between the working electrode and the reference electrode is held at a baseline level to separate the primary pulse from the secondary pulse.

17. The method of claim 16, wherein the gap time interval is selected from a range of about 1 millisecond to about 100 milliseconds.

18. The method of claim 15, wherein the primary pulse is shaped such that the electrical potential applied between the working electrode and the reference electrode during the primary pulse ascends from a baseline level to a peak level and then descends from the peak level to the baseline level.

19. The method of claim 18, wherein the baseline level of the electrical potential applied between the working electrode and the reference electrode is −

0.4 Volts, wherein the peak level of the electrical potential applied between the working electrode and the reference electrode is 1.5 Volts.

20. The method of claim 18, wherein the primary pulse is a triangle waveform that (i) ramps up at a constant rate from the baseline level of electrical potential to the peak level of electrical potential and (ii) ramps down at a constant rate from the peak level of electrical potential to the baseline level of electrical potential.

21. The method of claim 15, wherein the primary pulse of the binary waveform is identical to the secondary pulse of the binary waveform.