Chemistry: electrical and wave energy – Apparatus – Electrophoretic or electro-osmotic apparatus
Reexamination Certificate
2000-11-06
2004-11-30
Bell, Mark L. (Department: 1755)
Chemistry: electrical and wave energy
Apparatus
Electrophoretic or electro-osmotic apparatus
Reexamination Certificate
active
06824664
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates generally to microfluidic chips and methods for performing electrodeless purification, concentration, trapping and launching of polarizable particles or molecules in fractionating devices or chemical/amplification/detection devices by dielectrophoresis. The novel devices utilize dielectrophoresis technology achieved by using insulating constrictions without the use of metal electrodes and exploiting low frequency polarizability of particles or molecules. In particular, the polarizable particles and molecules include but are not limited to, cells, viruses, polymer particles, colloids and molecules such as proteins, peptides, carbohydrates, and polynucleotides, in particular, single-stranded or double-stranded DNA or RNA. The invention also relates to a device for thermocycling polarizable particles, in particular for amplification of nucleic acids. Specifically, the invention involves trapping minute amounts of nucleic acids in a microfabricated, dielectrically focused device, thermocycling them, and releasing them for fractionation or analysis.
2. Description of the Related Art
One of the great challenges in biotechnology is how to move and concentrate molecules in a micro-fabricated environment. One possible technique is dielectrophoresis (DEP) in which the translation of neutral matter is caused by polarization effects in a nonuniform electric field, see Polh, H. A., Dielectrophoresis: The Behavior of Neutral Matter in Nonuniform Electric Fields, Cambridge University Press, Cambridge, UK, (1978) and Pethig, R., Dielectrophoresis: Using Inhomogeneous AC Electrical Fields to Separate and Manipulate Cells, Crit. Rev. Biotechnol. Vol. 16, Iss. 4, pp. 331-348, (1996).
DEP has been used for sample manipulation at the molecular level. Applications of DEP include: separation of colloidal particles, as described in Rousselet, J. et al., Directional Motion of Brownian Particles Induced by a Periodic Asymmetric Potential, Nature (London), 370, pp. 446-448, (1994) and Green, N. G. et al., Dielectrophoresis of Submicrometer Latex Spheres Experimental Results, J. Phys. Chem. B, Vol. 103, Iss. 1, pp. 41-50, (1999); DEP ratchet, as described in Gorre-Talini, L. et al., Dielectrophoretic Pratchets, Chaos 8: (3) pp. 650-656 (September 1998); DEP coating, as described in Choi, W. B. et al., Field Emission from Silicon and Molybdenum Tips Coated with Diamond Powder by Dielectrophoresis, Appl. Phys. Lett., Vol. 68, Iss. 6, pp. 720-722, (1996); separation of yeast, as described in Markx, G. H. et al., Separation of Viable and Non-Viable Yeast Using Dielectrophoresis, J. Biotechnol. 23:29-37; separation of virus, as described in Morgan, H. et al., Separation of Submicron Bioparticles by Dielectrophoresis, Biophys. J. 77: pp. 516-525, (1999); separation of cancer cells, as described in Becker, F. F. et al., Separation of Human Breast-Cancer Cells from Blood by Differential Dielectric Affinity, Proc. Nat. Acad. Sci. (USA), Vol. 92, Iss. 3, pp. 860-864, (1995) and Yang, J. et al., Cell Separation on Microfabricated Electrodes Using Dielectrophoretic/Gravitational Field Flow Fractionation, Anal. Chem., Vol. 71, Iss. 5, pp. 911-918, (1999); and trapping and manipulation of DNA, as described in Washizu, M. et al., Electrostatic Manipulation of DNA in Microfabricated Structures, IEEE Trans. Ind. Appl., 26: pp. 1165-1172, (1990), Washizu, M. et al., Molecular Dielectrophoresis of Biopolymers, IEEE Trans. Ind. Appl. 30:835-843, (1994), Washizu, M. et al., Applications of Electrostatic Stretch-and-Positioning of DNA, Vol. 31, pp. 447-456 (1995), and Asbury, C. L. et al., Trapping of DNA in Nonuniform Oscillating Electric Fields, Biophysical Journal, 74:1024-1030 (1998).
The essence of dielectrophoretic trapping is that a dielectric object will be trapped in the regions of high field gradient provided there is sufficient dielectric response to overcome thermal energy and the electrophoretic force. A conventional method to make a DEP trap is to create an electric field gradient by an arrangement of fine planar electrodes either: directly connected to a voltage source; as described in Rousselet, J., et al., Directional Motion of Brownian Particles Induced by a Periodic Asymmetric Potential, Nature (London), 370, 446-448, (1994) and Green, N. G. et al., Dielectrophoresis of Submicrometer Latex Spheres Experimental Results, J. Phys. Chem. B, Vol. 103, Iss. 1, pp. 41-50, (1999); or free floating, as described in Washizu, M. et al., Molecular Dielectrophoresis of Biopolymers, IEEE Trans. Ind. Appl. 30:835-843, (1994); Washizu, M. et al., Applications of Electrostatic Stretch-and-Positioning of DNA, Vol. 31, pp. 447-456 (1995); and Asbury, C. L. et al., Trapping of DNA in Nonuniform Oscillating Electric Fields, Biophysical Journal, 74:1024-1030 (1998).
U.S. Pat. No. 6,117,660 describes a method of treating material with electrical fields and with an added treated substance. A plurality of electrodes are arrayed around the material to be treated and are connected to outputs of an electrode selection apparatus. Inputs of the electrode selection apparatus are connected to outputs of an agile pulse sequence generator. A treating substance is added to the membrane-containing material. Electrical pulses are applied to the electrode selection apparatus and are routed through the electrode selection apparatus in a predetermined, computer-controlled sequence to selected electrodes in the array of electrodes, whereby the membrane containing material is treated with the added treating substance and with electrical fields of sequentially varying directions.
U.S. Pat. No. 6,071,394 describes a method for performing channel-less separation of cells by dielectrophoresis, lysis and diagnostic analyses. A cartridge including a microfabricated silicon chip on a printed circuit board and a flow cell mounted to the chip forms a flow chamber. The cartridge also includes output pins for electronically connection the cartridge to an electronic controller. The chip includes a plurality of circular microelectrodes which are preferably coated with a protective permeation layer which prevents direct contact between an electrode and a sample introduced into the flow chamber and enables immobilization of specific antibodies for specific cell capture. The amplification of nucleic acids is central to the current field of molecular biology. Library screening, cloning, forensic analysis, genetic disease screening and other increasingly powerful techniques rely on the amplification of extremely small amounts of nucleic acids. As these techniques are reduced to a smaller scale for individual samples, the number of different samples that can be processed automatically in one assay expands dramatically. For further improvements, new integrated approaches for the handling and assaying of a large number of small samples are needed.
With the polymerase chain reaction (PCR) for nucleic acid amplification, a purified DNA polymerase enzyme is used to replicate the sample DNA in vitro. This system uses a set of at least two primers complementary to each strand of the sample nucleic acid template. Initially, the sample nucleic acid is heated to cause denaturation to single strands, followed by annealing of the primers to the single strands, at a lower temperature. The temperature is then adjusted to allow for extension of the primers by the polymerase along the template, thus replicating the strands. Subsequent thermal cycles repeat the denaturing, annealing and extending steps, which results in an exponential accumulation of replicated nucleic acid products.
PCR represents a considerable time savings over the replication of plasmid DNA in bacteria, but it still requires several hours. PCR also has limitations in the subsequent handling of the product. Most reactions occur isolated in a test tube or plate containing the require reagents. Further analysis of these products entails removing them from the tube and aliquoting to a new environment. Significant delay and loss and d
Austin Robert H.
Bakajin Olgica
Chou Chia Fu
Cox Edward C.
Tegenfeldt Jonas O.
Bell Mark L.
Brown Jennine
Mathews, Collins Shepherd & McKay, P.A.
Princeton University
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