Methods for measuring sample resistance in electroporation

• US 7,576,549 B2
• Filed: 12/06/2006
• Issued: 08/18/2009
• Est. Priority Date: 09/21/2006
• Status: Active Grant

• Current Assignee: Bio-Rad Laboratories Incorporated
• Original Assignee: Bio-Rad Laboratories Incorporated
• Inventors: Ragsdale, Charles W.
• Primary Examiner(s): Nguyen; Vincent Q
• Assistant Examiner(s): NATALINI, JEFF WILLIAM
• Application Number:
  US11/567,438
• Publication Number:
  US 20080076144A1
• Time in Patent Office: 986 Days
• Field of Search: 324/711, 435/285.2, 606/34
• US Class Current: 324/711
• CPC Class Codes: C12N 13/00 Treatment of microorganisms or enzymes with electrical or wave energy, e.g. magnetism, sonic waves

Abstract

Systems and methods of measuring resistances of samples to be electroporated and utilizing the measured resistances in the electroporation are provided. During an electrical pulse sent to the sample, a time and a corresponding voltage drop on a known capacitance is measured to determine the sample resistance. A constant voltage may be assumed, and the voltage drop across a known resistance in series with the sample resistance is used to determine the sample resistance. Based on the value of the sample resistance, an electrical pulse may be altered by changing a value of a parallel resistance.

Claims

1. A method of determining an estimate of a resistance R_S of a sample load in an electroporation system, the method comprising:

determining a capacitance C of one or more capacitors;

transmitting an electrical pulse from the capacitors to the sample load in the electroporation system;

measuring an initial voltage V_I on the capacitors;

measuring a second voltage V₂ on the capacitors, wherein measuring V₂ occurs at a time T₁ after measuring V_I; and

calculating a first estimate of R_S based on C, V_I, V₂, and T₁.

2. The method of claim 1, further comprising:

determining a set R_O of resistances of one or more resistive elements other than the sample load, wherein calculating a first estimate is also based on resistances R_O.

3. The method of claim 2 wherein calculating the first estimate of R_S comprises using a formula

$T_1=R·$

C ·

ln ⁡

[ V I V 2 ] ,

wherein a resistance R includes contributions from R_S and resistances R_O.

4. The method of claim 3 wherein the resistances R_O include a variable resistance connected in parallel with the sample load.

5. The method of claim 3 wherein calculating the first estimate of R_S comprises reading an approximate value for

$\ln$

[ V I V 2 ]

from a table.

6. The method of claim 1 further comprising:

measuring one or more additional voltages on the capacitors at one or more additional times after measuring V_I; and

calculating an average estimate of R_S based on the first estimate and the additional voltages and additional times.

7. The method of claim 6 wherein calculating an average estimate of R_S comprises:

calculating additional estimates of R_S based on the additional voltages and additional times; and

averaging the additional estimates and the first estimate to obtain the average estimate.

8. The method of claim 1 wherein the electrical pulse approximates a square wave.

9. The method of claim 1 wherein determining a capacitance C of one or more capacitors comprises reading an individual capacitance of each of the capacitors from a memory.

10. The method of claim 9, further comprising selecting the capacitors based on the individual capacitances read from memory.

11. A method of determining an estimate of a resistance R_S of a sample load in an electroporation system, the method comprising:

determining a capacitance C of one or more capacitors;

determining a resistance R₁ of one or more resistive elements connected in series with the sample load in the electroporation system;

transmitting an electrical pulse from the capacitors to the sample load and to the resistive elements;

measuring a voltage V_C on the capacitors;

measuring a second voltage V₂ that results from a voltage drop after at least one of the sample load and the resistive elements; and

calculating a first estimate of R_S based on C, R₁, V_C, and V₂.

12. The method of claim 11 wherein calculating the first estimate of R_S comprises using a formula for a voltage divider.

13. The method of claim 12 further comprising:

determining a resistance R_O of the electroporation system other than the sample load and R₁, wherein the formula includes R_O.

14. The method of claim 13 wherein the resistance R_O is connected in parallel with the sample load.

15. The method of claim 11 wherein the resistance R₁ is connected in series between the capacitors and the sample load, and wherein the second voltage V₂ is measured between the resistance R₁ and the sample load.

16. The method of claim 15 further comprising

closing a switch to transmit the electrical pulse, wherein the resistance R₁ includes the switch.

17. The method of claim 11 wherein the resistance R₁ is connected in series between the sample load and a common return path, and wherein the second voltage V₂ is measured after the sample load.

18. The method of claim 11 wherein the electrical pulse has a width of less than 1 millisecond.

19. An electroporation system that determines an estimate of a resistance R_S of a sample load in the electroporation system, the system comprising:

a plurality of capacitors;

a computer system that determines a capacitance C of one or more of the capacitors; and

a switch that is coupled with the computer system and that when open allows transmitting an electrical pulse from the one or more capacitors to the sample load in the electroporation system,

wherein the computer system is configured to;

measure an initial voltage V_I on the one or more capacitors;

measure a second voltage V₂ on the one or more capacitors, wherein measuring V₂ occurs at a time T₁ after measuring V_I; and

calculate a first estimate of R_S based on C, V_I, V₂, and T₁.

20. The electroporation system of claim 19, wherein the computer system is further configured to determine a set R_O of resistances of one or more resistive elements other than the sample load, wherein calculating a first estimate is also based on resistances R_O.

21. The electroporation system of claim 20, wherein calculating the first estimate of R_S comprises using a formula

$T_1=R·$

C ·

ln ⁡

[ V I V 2 ] ,

wherein a resistance R includes contributions from R_S and resistances R_O.

22. An electroporation system that determines an estimate of a resistance R_S of a sample load in the electroporation system, the system comprising:

a plurality of capacitors;

a computer system that determines a capacitance C of one or more of the capacitors and that determines a resistance R₁ of one or more resistive elements connected in series with the sample load in the electroporation system; and

a switch that is coupled with the computer system and that when open allows transmitting an electrical pulse from the one or more capacitors to the sample load in the electroporation system and to the resistive elements;

wherein the computer system is configured to;

measure a voltage V_C on the capacitors;

measure a second voltage V₂ that results from a voltage drop after at least one of the sample load and the resistive elements; and

calculate a first estimate of R_S based on C, R₁, V_C, and V₂.

23. The system of claim 22 wherein calculating the first estimate of R_S comprises using a formula for a voltage divider.

24. The system of claim 23 wherein the computer system is further configured to determine a resistance R_O of the electroporation system other than the sample load and R₁, wherein the formula includes R_O, and wherein the resistance R_O is connected in parallel with the sample load.