Method and apparatus for sensing a time varying current passing through an ion channel

• US 7,622,934 B2
• Filed: 07/22/2005
• Issued: 11/24/2009
• Est. Priority Date: 07/23/2004
• Status: Active Grant

• Current Assignee: Electronic BioSciences Inc.
• Original Assignee: Electronic Bio Sciences, LLC
• Inventors: Dugan, Regina E., Hibbs, Andrew D.
• Primary Examiner(s): Nguyen; Vincent Q
• Application Number:
  US11/658,094
• Publication Number:
  US 20080094076A1
• Time in Patent Office: 1,586 Days
• Field of Search: 324/686, 324/459, 324/439, 324/445, 324/446, 324/658, 435/6, 204/400
• US Class Current: 324/686
• CPC Class Codes: G01N 27/22 by investigating capacitance
• CPC Class Codes: G01N 33/48728 Investigating individual cells, e.g. by patch clamp, voltage clamp investigating individual particles in general G01N15/10

Abstract

A capacitive sensing system is used to measure a time-varying ion current through a channel, such as an ion channel or protein pore. Such a capacitive system does not suffer problems of electrode corrosion and, when used with methods to control a build up of ion concentration, allows the use of measurement volumes around the channel with dimensions on a scale of nanometers.

Claims

1. An apparatus for sensing a time varying current passing through a channel provided in a membrane comprising:

a membrane including a channel located therein;

a voltage source for establishing a potential difference across the channel and driving an ionic current through the channel; and

a capacitive sensing electrode positioned to measure an electrical property of the membrane.

2. The apparatus according to claim 1, further comprising:

a bath; and

a sensing volume separated from the bath by the membrane.

3. The apparatus according to claim 2, wherein the voltage source further comprises a first electrode located in the bath and a second electrode located in the sensing volume.

4. The apparatus according to claim 3, further comprising:

a first electrolyte in the bath and a second electrolyte in the sensing volume, wherein the second electrode is capacitively coupled to the second electrolyte, with negligible contribution from resistive current.

5. The apparatus according to claim 2, wherein the voltage source comprises a first electrode located in the bath and the capacitive sensing electrode located in the sensing volume.

6. The apparatus according to claim 2, further comprising:

means for adjusting an amplitude of a voltage of the voltage source to offset a build up of voltage in the sensing volume.

7. The apparatus according to claim 1, further comprising:

circuitry, coupled to the capacitive sensing electrode, for determining the ionic current.

8. The apparatus according to claim 1, wherein the channel is selected from the group consisting of:

an ion channel, a protein pore, a nanochannel and an engineered aperture.

9. The apparatus according to claim 1, wherein the channel has two defined conductive states.

10. The apparatus according to claim 1, wherein the membrane is formed from a bilipid or a liquid film.

11. The apparatus according to claim 1, wherein the membrane constitutes a solid.

12. The apparatus according to claim 11, wherein the membrane is formed from polycarbonate.

13. The apparatus according to claim 11, wherein the membrane is formed from polyimide.

14. The apparatus according to claim 1, wherein the sensing volume has a thickness less than approximately 1 mm.

15. The apparatus according to claim 1, wherein the sensing volume has a thickness less than approximately 1 μ

m.

16. The apparatus according to claim 1, wherein the sensing volume has a thickness less than approximately 10 nm.

17. The apparatus according to claim 1, further comprising:

a substrate wherein the membrane is supported on the substrate.

18. The apparatus according to claim 17, wherein the substrate is selected from the group consisting of:

ultra thin viscous films, hydrophilic polymers, soft polymer cushions, aerogels, xerogels and tethers.

19. The apparatus according to claim 17, wherein the substrate constitutes a solid surface provided with a through hole.

20. The apparatus according to claim 17, wherein the voltage source further includes a first electrode located directly adjacent the channel opposite to the capacitive sensing electrode.

21. The apparatus according to claim 1, further comprising:

means for maintaining a driving voltage at a low level to minimize the ionic current passing through the channel.

22. The apparatus according to claim 1, further comprising:

means for producing a DC or quasi DC voltage across the channel by applying a driving current waveform with a net increasing signal over a desired time period.

23. A method of sensing a time varying current passing through a channel in a membrane located between a bath and a sensing volume comprising:

placing an analyte in the bath;

applying a driving voltage across the channel; and

measuring an electrical property of the membrane with a capacitive sensing electrode.

24. The method of claim 23, in which the channel switches between defined conductivity states in a stochastic manner.

25. The method of claim 23, further comprising:

adjusting an amplitude of the voltage to offset a build up of voltage in the sensing volume.

26. The method of claim 23, further comprising:

maintaining the driving voltage at a low level to minimize an ionic current passing through the channel.

27. The method of claim 23, further comprising:

producing a DC or quasi DC voltage across the channel by applying a driving current waveform with a net increasing signal over a desired time period.