Method and apparatus using electric field for improved biological assays

• US 8,277,628 B2
• Filed: 07/10/2008
• Issued: 10/02/2012
• Est. Priority Date: 07/13/2007
• Status: Active Grant

• Current Assignee: Board of Trustees of the Leland Stanford Junior University (Stanford University)
• Original Assignee: Board of Trustees of the Leland Stanford Junior University (Stanford University)
• Inventors: Ronaghi, Mostafa, Khurana, Tarun, Santiago, Juan G.
• Primary Examiner(s): Ball, J. Christopher
• Assistant Examiner(s): DIETERLE, JENNIFER M
• Application Number:
  US12/170,941
• Publication Number:
  US 20090032401A1
• Time in Patent Office: 1,545 Days
• Field of Search: 204/400, 204/457, 204/450, 204600-650, 204/547, 435 4- 4052, 435/288.7, 435/283.1, 435/288.5, 435/287.2, 422/68.1, 422/82.01, 422/82.02, 977/958
• US Class Current: 204/643
• CPC Class Codes: B01J 2219/00317 Microwell devices, i.e. having large numbers of wells
• CPC Class Codes: B01J 2219/00459 Beads
• CPC Class Codes: B01J 2219/00466 in a slurry
• CPC Class Codes: B01J 2219/00596 Solid-phase processes
• CPC Class Codes: B01J 2219/00648 by the use of solid beads
• CPC Class Codes: B01J 2219/00653 the compounds being bound to electrodes embedded in or on the solid supports
• CPC Class Codes: B01J 2219/00702 Processes involving means for analysing and characterising the products
• CPC Class Codes: B01L 2200/0668 Trapping microscopic beads
• CPC Class Codes: B01L 2300/0819 Microarrays; Biochips
• CPC Class Codes: B01L 2400/0415 electrical forces, e.g. electrokinetic
• CPC Class Codes: B01L 3/502761 specially adapted for handling suspended solids or molecules independently from the bulk fluid flow, e.g. for trapping or sorting beads, for physically stretching molecules investigating characteristics of particles G01N15/00

Abstract

Disclosed are a method and apparatus that use an electric field for improved biological assays. The electric field is applied across a device having wells, which receive reactants, which carry a charge. The device thus uses a controllable voltage source between the first and second electrodes, which is controllable to provide a positive charge and a negative charge to a given electrode. By controlled use of the electric field charged species in a fluid in a fluid channel are directed into or out of the well by an electric field between the electrodes. The present method involves the transport of fluids, as in a microfluidic device, and the electric field-induced movement of reactive species according to various assay procedures, such as DNA sequencing, synthesis or the like.

Claims

1. A device for carrying out biological assays, having at least one fluid channel, a reaction area with an opening exposed to the fluid channel, and a bottom of the reaction area offset from the fluid channel, the device being constructed for fluid flow in a direction transverse to a reaction area opening, comprising:

(a) a first electrode adjacent to the bottom of the reaction area;

(b) a second electrode adjacent to the reaction area opening; and

(c) a controllable voltage source connected to the first and second electrodes which is controllable to provide an alternating voltage with a superimposed DC bias voltage between the first electrode and the second electrode to create an electric field between the first electrode and the second electrode,

the first electrode and the second electrode being capacitively coupled so that charged species in a fluid in the fluid channel are directed into or out of the reaction area by the electric field between the electrodes produced by the controllable voltage source.

2. The device of claim 1 wherein the electrode adjacent to the bottom is a thin layer of ITO, less than about 150 nm thick.

3. The device of claim 1 wherein reaction areas are defined in an inert, solid polymer selected from the group consisting of photoresist and PDMS.

4. The device of claim 1 wherein the electrodes are formed by a wire grid.

5. The device of claim 1 wherein the controllable voltage source provides a reversible DC bias voltage.

6. The device of claim 1 further comprising a reaction sensor coupled to the reaction area for detecting reactions in the reaction area.

7. The device of claim 6 wherein the reaction sensor comprises a fiberoptic faceplate coupled to the first electrode, and the first electrode is transparent.

8. The device of claim 6 wherein the reaction sensor comprises a CMOS photosensitive element.

9. The device of claim 1 further wherein the reaction area is a well that is sized to contain only one bead.

10. The device of claim 9 further comprising beads that are negatively charged.

11. The device of claim 10 wherein the negatively charged beads are polystyrene.

12. The device of claim 10 wherein the beads are magnetic and the device further comprises a magnet.

13. The device of claim 1 wherein the electrodes comprise a dielectric coating on surfaces of said first and second electrodes, whereby said dielectric coating is exposed to liquid in the fluid channel.

14. The device of claim 13 wherein the dielectric coating is one or more of poly-p-xylylene or silicon oxide or silicon nitride.

15. The device of claim 1 having a plurality of reaction areas defined in the fluid channel and whereby charged species are directed from the fluid channel into and out of the plurality of reaction areas.

16. The device of claim 15 wherein the first electrode and the second electrode form essentially parallel sheets, with a plurality of reaction areas and the fluid channel there between.

17. The device of claim 1 wherein the first electrode and the second electrode form essentially parallel sheets, with a plurality of reaction areas and the fluid channel there between.

18. The device of claim 17 wherein the first electrode and the second electrode comprise a dielectric coating on a surface exposed to fluid in the fluid channel.