WO2005088291A1 - Small volume electrochemical analysis system - Google Patents

Small volume electrochemical analysis system Download PDF

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Publication number
WO2005088291A1
WO2005088291A1 PCT/CA2005/000390 CA2005000390W WO2005088291A1 WO 2005088291 A1 WO2005088291 A1 WO 2005088291A1 CA 2005000390 W CA2005000390 W CA 2005000390W WO 2005088291 A1 WO2005088291 A1 WO 2005088291A1
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WO
WIPO (PCT)
Prior art keywords
working electrode
electrode
coating
analysis system
sample
Prior art date
Application number
PCT/CA2005/000390
Other languages
French (fr)
Inventor
Andrzej Baranski
Todd Sutherland
Yi-Tao Long
Jeremy Lee
Original Assignee
University Of Saskatchewan
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by University Of Saskatchewan filed Critical University Of Saskatchewan
Publication of WO2005088291A1 publication Critical patent/WO2005088291A1/en

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Classifications

    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
    • G01N27/00—Investigating or analysing materials by the use of electric, electrochemical, or magnetic means
    • G01N27/26—Investigating or analysing materials by the use of electric, electrochemical, or magnetic means by investigating electrochemical variables; by using electrolysis or electrophoresis
    • G01N27/28—Electrolytic cell components
    • G01N27/30—Electrodes, e.g. test electrodes; Half-cells
    • G01N27/327—Biochemical electrodes, e.g. electrical or mechanical details for in vitro measurements
    • G01N27/3275—Sensing specific biomolecules, e.g. nucleic acid strands, based on an electrode surface reaction
    • G01N27/3277—Sensing specific biomolecules, e.g. nucleic acid strands, based on an electrode surface reaction being a redox reaction, e.g. detection by cyclic voltammetry

Definitions

  • the invention is in the field of electrochemical cells, including cells that may be used to assay an electrochemical characteristic of a polymeric coating, such as DNA, on a working electrode.
  • the invention provides an electrochemical analysis system comprising a fluid-dispensing counter electrode positionable to dispense an electrolyte onto a coated working electrode, wherein electrical energy applied to the system induces a detectable signal that is indicative of a property of the coating on the working electrode.
  • the counter electrode may for example be tubular, adapted to dispense an electrolyte from the lumin of the tube.
  • the working electrode may for example be coated with a molecular substrate, such as an organic compound or a polymer.
  • the coating on the working electrode may be a biological molecule or polymer, such as a nucleic acid.
  • the systems of the invention may be used to measure an electrical property of the coating on the working electrode, such as systems for carrying out impedance measurements or chronoamperometry.
  • systems of the invention may be used to detect the interaction of the coating on the working electrode with a ligand, such as a ligand introduced into a sample chamber for binding to the coating on the working electrode or a ligand dispensed onto to the working electrode by the fluid-dispensing counter electrode.
  • FIG. 1 Impedance spectrum of Pt-tube electrode (Counter electrode) positioned above a flat gold electrode (Working electrode) covered in a monolayer of duplex DNA (20-mer) attached via Au-S linkage.
  • the Pt-tube has an outer diameter of 400 ⁇ m and an inner diameter of 100 ⁇ m.
  • Supporting electrolyte 20 mM Tris-CI0 4 + 20 mM NaCI0 4 + 4 mM Fe(CN) 6 4_/3" .
  • Frequency range 100 kHz - 0.1 Hz (5 points per decade) with a 5 mV sinusoidal excitation signal applied on top of a 0 mV applied DC potential. Reference lead was connected directly to the Counter (Pt-tube) electrode.
  • FIG. 1 Cyclic voltammagram of a clean, flat Au electrode (Working) positioned below the Pt-tube electrode (Counter electrode) with a Teflon coated (9 ⁇ m)-Pt wire (50 ⁇ m diameter) inserted through the Pt-tube to contact the measurement solution as a quasi-reference electrode.
  • the Pt-tube has an outer diameter of 400 ⁇ m and an inner diameter of 100 ⁇ m.
  • Supporting electrode 20 mM Tris-CI04 + 20 mM NaCI04 + 4 mM Fe(CN)64-/3-.
  • Electrochemical parameters A triangular wave form was applied from -0.5 to +0.5 (vs. Pt quasi reference) with a gradient of 20 mV-s-1.
  • FIG. 3A is a schematic illustration showing a platinum tube counter electrode of the invention making electrical contact with a gold electrode coated with DNA, the electrical contact being made through an electrolyte solution extruded from the tip of the tube electrode onto the surface of the coated gold working electrode.
  • FIG. 3B is a schematic illustration of a sample chamber of the invention having eight gold working electrode disks therein.
  • the working electrode disks may be coated, for example with a layer of one or more nucleic acids.
  • a sample may be introduced into the sample chamber, such as a nucleic acid capable of hybridizing to one or more of the nucleic acid coatings on the working electrodes.
  • the sample may be introduced into the sample chamber by way of an input port, and drained by way of an output port, and washing steps may similarly be performed, for example to vary the stringency of hybridization to a nucleic acid layer on the working electrodes.
  • the working electrodes may then be interrogated by tubular counter electrodes of the invention to measure an electrical property of the coating on the working electrode. The portion of the working electrode that is addressed by the counter electrode will be determined by the area of contact between the working electrode surface and the electrolyte extruded from the tubular counter electrode of the invention.
  • the invention provides an electrochemical analysis system comprising a fluid-dispensing counter electrode, such as a Pt tube electrode.
  • the counter electrode of the invention may be adapted to be positionable to dispense an electrolyte, such as an aqueous electrolyte.
  • the electrolyte may be dispensed onto a coated working electrode, such as an electrode coated with a polymer or organic compound, such as DNA.
  • the system may be adapted so that the electrical contact between the electrolyte dispensed from the counter electrode and the working electrode forms an electrochemical cell. Electrical components may be provided so that electrical energy may be applied to the cell in the system so as to induce a detectable signal that is indicative of a property of the coating on the working electrode.
  • a plurality of working electrode binding domains may for example be provided, able to specifically bind one or more analytes of interest in a sample.
  • the binding domains may for example be prepared as patterned, multi-array multi-specific working electrode surfaces on a support.
  • the invention provides an electrochemical system for measuring a detectable signal, such as electrochemiluminescence or impedance, in a sample, for example in a sample on a working electrode in an electrochemical cell of the invention.
  • a potential may be applied between a coated working electrode and an electrolyte-dispensing counter electode, for example by voltage control means, to induce the detectable signal, such as electrochemiluminescence or impedance, which is indicative of a property of the coating on the working electrode.
  • a detector such as impedance measurement means or a photon detector means for detecting electrochemiluminescence, may be employed to measure the detectable characteristic of the coating.
  • An embodiment of the electrochemical system of the invention may for example be constructed as follows:
  • a Platinum tube may be attached to a teflon tube at one end.
  • a teflon coated reference electrode (such as a Palladium electrode) may be threaded through the Pt tube and the teflon tube.
  • the teflon tube may be attached to a syringe or other microfluidics device, for example leaving the reference electrode on the outside (other geometries are possible, e.g. attaching a teflon tube with a T-junction to the Pt tube; one end of the T may be attached to the syringe while the other provides an outlet for the reference electrode).
  • the above assembly may be fixed in a micropositioner.
  • the working electrode and the Pt tube which acts as the counter electrode may be attached to a potentiostat, for example with electrical clamps. If applicable, the reference electrode may also be attached to the potentiostat.
  • the Pt tube may be precisely positioned at a fixed height above the working electrode.
  • the working electrode may be pretreated with a probe, such as a protein or nucleic acid, to provide a coated working electrode.
  • the Pt tube may be positioned over an area of relatively uniformly-coated working electrode, in some embodiments avoiding positions over any uncoated portions working electrode, such as electrical leads to the working electrode.
  • the geometry of the working electrode may vary, and may for example be flat.
  • a small volume of electrolyte may be dispensed from the Pt tube to contact the working electrode.
  • the volume required to form a desired region of contact may be determined by the height of the Pt tube above the working electrode, and by the internal diameter of the Pt tube.
  • Electrochemical measurements may then be performed to determine an electrochemical characteristic of the coating on the working electrode.
  • the Pt tube may also be used to deliver a sample containing a ligand for binding or interaction with the coating on the working electrode.
  • the fluid-dispensing counter electrode may also be used to dispense other fluids, such as washing buffers to clean the working electrode before performing the electrochemical measurements.
  • the surface area of the working electrode addressed by the electrochemical detection system of the invention may be determined by the diameter of the tubular fluid-dispensing counter electrode, such as the illustrated a Pt-tube electrode.
  • the effect of variations in the coating of the working electrode may be minimized by localizing the area of analysis to a uniformly coated area.
  • a reference electrode (such as a teflon-coated Pd reference electrode) may be inserted into a tubular fluid-dispensing counter electrode, so that the system of the invention may be used for alternative forms of electrochemical analysis, such as chronoamperometric measurements, cyclic voltammetry or direct current measurements.

Abstract

In various aspects, the invention provides an electrochemical analysis system comprising a fluid-dispensing counter electrode positionable to dispense an electrolyte onto a coated working electrode, wherein electrical energy applied to the system induces a detectable signal that is indicative of a property of the coating on the working electrode.

Description

SMALL VOLUME ELECTROCHEMICAL ANALYSIS SYSTEM FIELD OF THE INVENTION
[0001] The invention is in the field of electrochemical cells, including cells that may be used to assay an electrochemical characteristic of a polymeric coating, such as DNA, on a working electrode.
BACKGROUND OF THE INVENTION
[0002] A wide variety of systems have been proposed for carrying out electrochemical analysis of molecular substrates. Alternative systems are for example disclosed in the following US patents, which are hereby incorporated herein by reference: 673,533; 6,618,934; 6,592,745; 6,591 ,125; 6,461 ,496; 6,458,600; 6,338,790; 6,306,584; 6,299,757; 6,207,369; 6,140,045; 6,090,545; 6,078,490; 6,066,448; 6,010,613; 5,622,872; 5,571 ,568; 5,491 ,097.
SUMMARY OF THE INVENTION
[0003] In various aspects, the invention provides an electrochemical analysis system comprising a fluid-dispensing counter electrode positionable to dispense an electrolyte onto a coated working electrode, wherein electrical energy applied to the system induces a detectable signal that is indicative of a property of the coating on the working electrode. The counter electrode may for example be tubular, adapted to dispense an electrolyte from the lumin of the tube. The working electrode may for example be coated with a molecular substrate, such as an organic compound or a polymer. In some embodiments the coating on the working electrode may be a biological molecule or polymer, such as a nucleic acid. In some embodiments, the systems of the invention may be used to measure an electrical property of the coating on the working electrode, such as systems for carrying out impedance measurements or chronoamperometry. In alternative embodiments, systems of the invention may be used to detect the interaction of the coating on the working electrode with a ligand, such as a ligand introduced into a sample chamber for binding to the coating on the working electrode or a ligand dispensed onto to the working electrode by the fluid-dispensing counter electrode. BRIEF DESCRIPTION OF THE DRAWINGS
[0004] Figure 1. Impedance spectrum of Pt-tube electrode (Counter electrode) positioned above a flat gold electrode (Working electrode) covered in a monolayer of duplex DNA (20-mer) attached via Au-S linkage. The Pt-tube has an outer diameter of 400 μm and an inner diameter of 100 μm. Supporting electrolyte: 20 mM Tris-CI04 + 20 mM NaCI04 + 4 mM Fe(CN)6 4_/3". Frequency range: 100 kHz - 0.1 Hz (5 points per decade) with a 5 mV sinusoidal excitation signal applied on top of a 0 mV applied DC potential. Reference lead was connected directly to the Counter (Pt-tube) electrode.
[0005] Figure 2. Cyclic voltammagram of a clean, flat Au electrode (Working) positioned below the Pt-tube electrode (Counter electrode) with a Teflon coated (9 μm)-Pt wire (50 μm diameter) inserted through the Pt-tube to contact the measurement solution as a quasi-reference electrode. The Pt-tube has an outer diameter of 400 μm and an inner diameter of 100 μm. Supporting electrode: 20 mM Tris-CI04 + 20 mM NaCI04 + 4 mM Fe(CN)64-/3-. Electrochemical parameters: A triangular wave form was applied from -0.5 to +0.5 (vs. Pt quasi reference) with a gradient of 20 mV-s-1.
[0006] Figure 3A is a schematic illustration showing a platinum tube counter electrode of the invention making electrical contact with a gold electrode coated with DNA, the electrical contact being made through an electrolyte solution extruded from the tip of the tube electrode onto the surface of the coated gold working electrode.
[0007] Figure 3B is a schematic illustration of a sample chamber of the invention having eight gold working electrode disks therein. The working electrode disks may be coated, for example with a layer of one or more nucleic acids. A sample may be introduced into the sample chamber, such as a nucleic acid capable of hybridizing to one or more of the nucleic acid coatings on the working electrodes. The sample may be introduced into the sample chamber by way of an input port, and drained by way of an output port, and washing steps may similarly be performed, for example to vary the stringency of hybridization to a nucleic acid layer on the working electrodes. The working electrodes may then be interrogated by tubular counter electrodes of the invention to measure an electrical property of the coating on the working electrode. The portion of the working electrode that is addressed by the counter electrode will be determined by the area of contact between the working electrode surface and the electrolyte extruded from the tubular counter electrode of the invention.
DETAILED DESCRIPTION OF THE INVENTION
[0008] In various aspects, the invention provides an electrochemical analysis system comprising a fluid-dispensing counter electrode, such as a Pt tube electrode. The counter electrode of the invention may be adapted to be positionable to dispense an electrolyte, such as an aqueous electrolyte. The electrolyte may be dispensed onto a coated working electrode, such as an electrode coated with a polymer or organic compound, such as DNA. The system may be adapted so that the electrical contact between the electrolyte dispensed from the counter electrode and the working electrode forms an electrochemical cell. Electrical components may be provided so that electrical energy may be applied to the cell in the system so as to induce a detectable signal that is indicative of a property of the coating on the working electrode.
[0009] In some embodiments, a plurality of working electrode binding domains may for example be provided, able to specifically bind one or more analytes of interest in a sample. The binding domains may for example be prepared as patterned, multi-array multi-specific working electrode surfaces on a support.
[0010] In one aspect, the invention provides an electrochemical system for measuring a detectable signal, such as electrochemiluminescence or impedance, in a sample, for example in a sample on a working electrode in an electrochemical cell of the invention. In such systems, a potential may be applied between a coated working electrode and an electrolyte-dispensing counter electode, for example by voltage control means, to induce the detectable signal, such as electrochemiluminescence or impedance, which is indicative of a property of the coating on the working electrode. A detector, such as impedance measurement means or a photon detector means for detecting electrochemiluminescence, may be employed to measure the detectable characteristic of the coating.
[0011] An embodiment of the electrochemical system of the invention may for example be constructed as follows:
[0012] 1. A Platinum tube may be attached to a teflon tube at one end.
[0013] 2. If required, a teflon coated reference electrode (such as a Palladium electrode) may be threaded through the Pt tube and the teflon tube.
[0014] 3. The teflon tube may be attached to a syringe or other microfluidics device, for example leaving the reference electrode on the outside (other geometries are possible, e.g. attaching a teflon tube with a T-junction to the Pt tube; one end of the T may be attached to the syringe while the other provides an outlet for the reference electrode).
[0015] 4. The above assembly may be fixed in a micropositioner.
[0016] 5. The working electrode and the Pt tube which acts as the counter electrode may be attached to a potentiostat, for example with electrical clamps. If applicable, the reference electrode may also be attached to the potentiostat.
[0017] 6. The Pt tube may be precisely positioned at a fixed height above the working electrode. The working electrode may be pretreated with a probe, such as a protein or nucleic acid, to provide a coated working electrode. The Pt tube may be positioned over an area of relatively uniformly-coated working electrode, in some embodiments avoiding positions over any uncoated portions working electrode, such as electrical leads to the working electrode. The geometry of the working electrode may vary, and may for example be flat.
[0018] 7. A small volume of electrolyte may be dispensed from the Pt tube to contact the working electrode. The volume required to form a desired region of contact may be determined by the height of the Pt tube above the working electrode, and by the internal diameter of the Pt tube.
[0019] 8. Electrochemical measurements may then be performed to determine an electrochemical characteristic of the coating on the working electrode.
[0020] 9. In some embodiments the Pt tube may also be used to deliver a sample containing a ligand for binding or interaction with the coating on the working electrode. The fluid-dispensing counter electrode may also be used to dispense other fluids, such as washing buffers to clean the working electrode before performing the electrochemical measurements.
[0021] In some embodiments, the surface area of the working electrode addressed by the electrochemical detection system of the invention may be determined by the diameter of the tubular fluid-dispensing counter electrode, such as the illustrated a Pt-tube electrode. In such embodiments, the effect of variations in the coating of the working electrode may be minimized by localizing the area of analysis to a uniformly coated area.
[0022] A reference electrode (such as a teflon-coated Pd reference electrode) may be inserted into a tubular fluid-dispensing counter electrode, so that the system of the invention may be used for alternative forms of electrochemical analysis, such as chronoamperometric measurements, cyclic voltammetry or direct current measurements.
[0023] The Figures show data from embodiments of the invention in which a 0.1 mm internal diameter Pt tube counter electrode was used to give reproducible impedance measurements of a DNA-coated gold surface. Alternative configurations of counter electrode, such as tubes of alternative cross sectional configurations or sizes, may be used to facilitate analysis in alternative embodiments, for example with alternative volumes of electrolyte. [0024] Although various embodiments of the invention are disclosed herein, many adaptations and modifications may be made within the scope of the invention in accordance with the common general knowledge of those skilled in this art. Such modifications include the substitution of known equivalents for any aspect of the invention in order to achieve the same result in substantially the same way. Numeric ranges are inclusive of the numbers defining the range. The word "comprising" is used herein as an open-ended term, substantially equivalent to the phrase "including, but not limited to", and the word "comprises" has a corresponding meaning. As used herein, the singular forms "a", "an" and "the" include plural referents unless the context clearly dictates otherwise. Thus, for example, reference to "a thing" includes more than one such thing. Citation of references herein is not an admission that such references are prior art to the present invention. Any priority document(s) and all publications, including but not limited to patents and patent applications, cited in this specification are incorporated herein by reference as if each individual publication were specifically and individually indicated to be incorporated by reference herein and as though fully set forth herein. The invention includes all embodiments and variations substantially as hereinbefore described and with reference to the examples and drawings.

Claims

1. An electrochemical analysis system comprising a fluid-dispensing counter electrode positionable to dispense an electrolyte onto a coated working electrode to form an electrochemical cell, wherein electrical energy applied to the cell induces a detectable signal that is indicative of a property of the coating on the working electrode.
2. An electrochemical analysis system comprising: a counter electrode having means for dispensing fluid, the counter electrode being positionable to dispense an electrolyte onto a coated working electrode to form an electrochemical cell; and means for applying electrical energy to the cell to induce a detectable signal that is indicative of a property of the coating on the working electrode.
3. The electrochemical analysis system of claim 1 or 2, wherein a plurality of coated working electrodes are arranged in an array, and the counter electrode is positionable to successively interrogate the array of working electrodes.
4. The electrochemical analysis system of claim 1 , 2 or 3, wherein the working electrode is housed in a sample chamber, and the sample chamber is adapted to permit the working electrode to be exposed to a sample solution for binding of a sample to the working electrode, so that the detectable signal is indicative of binding of the sample to the working electrode.
5. The electrochemical analysis system of claim 4 , wherein the sample chamber has a port for introducing the sample solution.
6. The electrochemical analysis system of any one of claims 1 through 5, wherein the coating is a nucleic acid.
7. The electrochemical analysis system of any one of claims 1 through 5, wherein the coating is a protein.
8. A method of determining a property of a coating on a coated working electrode, comprising positioning a fluid-dispensing counter electrode adjacent to the coated working electrode; dispensing an electrolyte onto the coated working electrode from the counter electrode, to form an electrochemical cell; and, applying electrical energy to the cell to induce a detectable signal that is indicative of a property of the coating on the working electrode.
9. The method of claim 8, wherein a plurality of coated working electrodes are arranged in an array, and the counter electrode is positionable to successively interrogate the array of working electrodes.
10. The method of claim 8 or 9, wherein the working electrode is housed in a sample chamber, and the sample chamber is adapted to permit the working electrode to be exposed to a sample solution for binding of a sample to the working electrode, so that the detectable signal is indicative of binding of the sample to the working electrode.
11. The method of claim 10, wherein the sample chamber has a port for introducing the sample solution.
12. The method of any one of claims 8 through 11 , wherein the coating is a nucleic acid.
13. The method of any one of claims 8 through 11 , wherein the coating is a protein.
PCT/CA2005/000390 2004-03-15 2005-03-15 Small volume electrochemical analysis system WO2005088291A1 (en)

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
US55271004P 2004-03-15 2004-03-15
US60/552,710 2004-03-15

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Citations (8)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US5403463A (en) * 1993-04-14 1995-04-04 Mannesmann Aktiengesellschaft Electrochemical sensor
EP0504730B1 (en) * 1991-03-22 1997-08-27 Seiko Instruments Inc. Electrochemical measurement system
US5779976A (en) * 1988-11-03 1998-07-14 Igen International, Inc. Apparatus for improved luminescence assays
US6461496B1 (en) * 1998-10-08 2002-10-08 Therasense, Inc. Small volume in vitro analyte sensor with diffusible or non-leachable redox mediator
EP0873514B1 (en) * 1995-06-19 2003-04-09 Lifescan, Inc. Method of determining an analyte using an electrochemical cell
US6576101B1 (en) * 1997-02-06 2003-06-10 Therasense, Inc. Small volume in vitro analyte sensor
US6599473B1 (en) * 1998-01-30 2003-07-29 Roche Diagnostics Gmbh Electrochemilumiscence method for detecting analytes
WO2004010104A2 (en) * 2002-07-18 2004-01-29 The Johns Hopkins University Embeddable corrosion rate meters for remotely monitoring structures

Patent Citations (8)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US5779976A (en) * 1988-11-03 1998-07-14 Igen International, Inc. Apparatus for improved luminescence assays
EP0504730B1 (en) * 1991-03-22 1997-08-27 Seiko Instruments Inc. Electrochemical measurement system
US5403463A (en) * 1993-04-14 1995-04-04 Mannesmann Aktiengesellschaft Electrochemical sensor
EP0873514B1 (en) * 1995-06-19 2003-04-09 Lifescan, Inc. Method of determining an analyte using an electrochemical cell
US6576101B1 (en) * 1997-02-06 2003-06-10 Therasense, Inc. Small volume in vitro analyte sensor
US6599473B1 (en) * 1998-01-30 2003-07-29 Roche Diagnostics Gmbh Electrochemilumiscence method for detecting analytes
US6461496B1 (en) * 1998-10-08 2002-10-08 Therasense, Inc. Small volume in vitro analyte sensor with diffusible or non-leachable redox mediator
WO2004010104A2 (en) * 2002-07-18 2004-01-29 The Johns Hopkins University Embeddable corrosion rate meters for remotely monitoring structures

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