Radio-frequency ion channel probe

• US 8,217,665 B2
• Filed: 11/25/2008
• Issued: 07/10/2012
• Est. Priority Date: 11/25/2008
• Status: Active Grant

• Current Assignee: Wisconsin Alumni Research Foundation (University of Wisconsin System)
• Original Assignee: Wisconsin Alumni Research Foundation (University of Wisconsin System)
• Inventors: Blick, Robert H., Qin, Hua
• Primary Examiner(s): NATALINI, JEFF WILLIAM
• Application Number:
  US12/277,837
• Publication Number:
  US 20100127716A1
• Time in Patent Office: 1,323 Days
• Field of Search: 324/675
• US Class Current: 324/675
• CPC Class Codes: G01N 33/48728 Investigating individual cells, e.g. by patch clamp, voltage clamp investigating individual particles in general G01N15/10
• CPC Class Codes: G01N 33/6872 Intracellular protein regulatory factors and their receptors, e.g. including ion channels

Abstract

A patch-clamp system employs a high-frequency characterization of cell wall membranes. Changes in the frequency response of a tank circuit incorporating the cell wall membrane impedance provides highly sensitive and highly time-resolved measurements of ion channel activity.

Claims

1. A high frequency cell membrane analyzer for cellular membranes of lipid bilayer with ion channels, the analyzer comprising:

an electrically insulating support adapted to provide a support region for holding the cellular membrane fixed with respect to the electrically insulating support;

a first and second electrode on opposite sides of the support regions separated by the cellular membrane; and

circuitry providing a high-frequency signal across the first and second electrodes and determining changes of impedance across the cellular membrane from measurement of a change in electrical resonance and providing a measureable output indicating the determined change in impedance.

2. The high frequency cell membrane analyzer of claim 1 wherein the support region is an aperture through the electrically insulating support forming a lip on a first side of the aperture sized to accept a cellular membrane spanning the lip to form a giga-ohm seal with the electrically insulating support.

3. The high frequency cell membrane analyzer of claim 1 wherein at least one of the first and second electrodes is a waveguide attached to the electrically insulating support.

4. The high frequency cell membrane analyzer of claim 3 wherein the waveguide is a strip-line.

5. The high frequency cell membrane analyzer of claim 1 wherein the circuitry is a tank circuit incorporating a capacitance across the cellular membrane as a capacitance of the tank circuit.

6. The high frequency cell membrane analyzer of claim 1 wherein the circuit includes at least one inductor in series with a capacitance.

7. The high frequency cell membrane analyzer of claim 1 wherein the electrically insulating support is a planar support and includes multiple apertures and lips each associated with a least one different second electrode for parallel measurements of cellular membranes at each of the multiple apertures.

8. The high-frequency cell membrane analyzer of claim 1 wherein the high-frequency signal is in excess of one MHz.

9. The high frequency cell membrane analyzer of claim 1 wherein impedance measured is capacitance of the cellular membrane.

10. The high frequency cell membrane analyzer of claim 1 wherein the impedance measured is resistance of the cellular membrane.

11. The high-frequency cell membrane analyzer of claim 1 wherein the first electrode includes two separated portions and wherein the high-frequency signal is applied to one portion and monitored at the second portion.

12. A method of measuring ion transport through a cellular membrane of lipid bilayer with ion channels, the method comprising the steps of:

(a) placing the cellular membrane to span a lip formed on an insulating substrate so that the lip and membrane separate a first and second electrode on opposite sides of the lip;

(b) applying a high-frequency electrical signal across the electrodes to determine an impedance therebetween; and

(c) monitoring changes in the impedance to detect ionic transport through the cellular membrane for events having a time resolution of substantially less than 20 μ

s.

13. The method of claim 12 wherein the impedance is determined by monitoring the electrical resonance of a tank circuit formed of inductors in the electrodes.

14. The method of claim 13 wherein the impedance is determined by a reflection from the tank circuit at the first and second electrode.

15. The method of claim 13 wherein the first electrode has a first and second portion and impedance is determined by a transmission of the tank circuit from a first portion of the first electrode to a second portion of the first electrode.

16. The method of claim 13 wherein the impedance is determined by a shifting of a natural resonance of the tank circuit in frequency.

17. The method of claim 13 wherein the impedance is determined by a broadening of a natural resonance of the tank circuit in frequency.

18. The method of claim 12 wherein the high-frequency signal is in excess of 1 MHz.

19. The method of claim 12 wherein impedance measured is capacitance of the cellular membrane.

20. The method of claim 12 wherein the impedance measured is resistance of the cellular membrane.