Closed-loop control of electrokinetic processes in microfluidic devices based on optical readings

• US 6,905,583 B2
• Filed: 12/10/2003
• Issued: 06/14/2005
• Est. Priority Date: 12/13/2002
• Status: Active Grant

• Current Assignee: Monogram Biosciences, Inc. (Laboratory Corporation Of America Holdings)
• Original Assignee: Aclara Biosciences, Inc (Laboratory Corporation Of America Holdings)
• Inventors: Wainright, Ann, Bjornson, Torleif
• Primary Examiner(s): Noguerola, Alex
• Application Number:
  US10/731,977
• Publication Number:
  US 20040118684A1
• Time in Patent Office: 552 Days
• Field of Search: 204/451, 204/454, 204/453, 204/452, 204601-604
• US Class Current: 204/453
• CPC Class Codes: G01N 27/44721 by optical means
• CPC Class Codes: G01N 27/44773 Multi-stage electrophoresis, e.g. two-dimensional electrophoresis

Abstract

A method for performing an electrophoretic separation on a microfluidic device includes applying an electric field to electrokinetically move a sample along a channel towards a location. The sample may be concentrated by application of the electric field. The method further comprises optically monitoring the location for at least a portion of the sample. Once the sample is detected, the electric field is automatically changed to further manipulate the sample. The sample may be spatially separated along a separation channel or channel portion. The closed-loop control of electric fields may be performed using a control unit adapted to apply a voltage potential between electrodes and an optical detector such as an LIF detector.

Claims

1. A method for performing an electrophoretic process on a microfluidic device comprising a first, second, third, fourth and fifth reservoir and a first channel extending from the first reservoir to the fifth reservoir, said device further comprising a second channel, third channel, and fourth channel and said second channel, third channel and fourth channel being in fluid communication with said first channel at respectively second-channel, third-channel, and fourth-channel intersections and each of said intersections being spaced along said first channel such that, relative to said first reservoir, said second-channel intersection is proximal to the third-channel intersection and the third-channel intersection is proximal to the fourth-channel intersection and the fourth-channel intersection is proximal to the fifth reservoir, and each of said second, third and fourth channels being in fluid communication with the second, third and fourth reservoirs respectively such that materials may be added and removed to the channels via the reservoirs, said method comprising:

applying a first voltage difference between the second reservoir and the third reservoir to move a sample from the second reservoir, into a sample region along the first channel and between the second-channel intersection and the third-channel intersection;

applying a second voltage difference between the first reservoir and the second reservoir to drive a terminating electrolyte from the first reservoir towards the sample in said sample region;

applying a third voltage difference between the first reservoir and the fifth reservoir to stack components of the sample between the terminating electrolyte and a leading electrolyte;

automatically applying a fourth voltage difference between the fourth reservoir and the fifth reservoir when the last component of the stacked sample reaches the fourth-channel intersection such that the components of the sample spatially separate while migrating along the first channel towards the fifth reservoir.

2. The method of claim 1 wherein an electrode is positioned in each of the reservoirs.

3. The method of claim 2 wherein at least one electrode is floated.

4. The method of claim 2 wherein all electrodes are simultaneously activated.

5. A system comprising the device as recited in claim 1 and a controller configured to apply voltage differentials as recited therein.

6. The system of claim 5 further comprising a detector adapted to sense when said sample reaches a location on said device.

7. The system of claim 6 wherein said location is said fourth-channel intersection.

8. The system of claim 6 wherein said detector is an optical detector.

9.The system of claim 6 wherein said detector senses at least one of fluorescence, absorbance, refractive index and light scattering from said sample.

9. A method for separating a plurality of components of a sample in a microfluidic device having a stacking channel and a separation channel downstream of said stacking channel, said method comprising:

applying a first electric field to concentrate the components between a trailing electrolyte and a first leading electrolyte along the stacking channel;

replacing at least a portion of the trailing electrolyte having the same composition as the first electrolyte; and

applying a second electric field across the first leading electrolyte, the components and the second leading electrolyte when at least a portion of said sample enters said separation channel whereby the components are separated by electrophoretic mobilities along the separation channel.

10. The method of claim 10 wherein the stacking channel and the separation channel are portions of a main channel.

13. The method of claim 10 wherein an optical detector is positioned to monitor the separation channel for the sample and the first electric field is modified when the detector senses the sample.

11. The method of claim 11 wherein said electric fields are applied by positioning and activating electrodes in reservoirs that are in fluid communication with said main channel.

12. The method of claim 12 wherein the electrodes are removable.

14. The method of claim 14 said optical detector comprises a single point detector.

15. The method of claim 14 wherein said optical detector comprises an imaging detector.

17. The method of claim 14 wherein said detector senses at least one of fluorescence, absorbance, refractive index and light scattering from said sample.

18. The method of claim 14 wherein said detector provides input to a control unit operated in closed loop mode.

16. The method of claim 16 wherein the imaging detector is a charge coupled device camera.