Assay device and method

• US 9,618,506 B2
• Filed: 03/29/2007
• Issued: 04/11/2017
• Est. Priority Date: 03/29/2006
• Status: Active Grant

• Current Assignee: Inverness Medical Switzerland GmbH (Abbott Laboratories)
• Original Assignee: Inverness Medical Switzerland GmbH (Abbott Laboratories)
• Inventors: Thomson, Alan Kenneth, Lowe, Phillip, Keatch, Steven Alexander, Howell, Steven, Marquordt, Claus, Polwart, Ruth
• Primary Examiner(s): Crawford, Erik B
• Application Number:
  US12/294,818
• Publication Number:
  US 20110053289A1
• Time in Patent Office: 3,666 Days
• Field of Search: 436518, 436526
• CPC Class Codes: B01L 2200/0621 Control of the sequence of chambers filled or emptied
• CPC Class Codes: B01L 2200/0668 Trapping microscopic beads
• CPC Class Codes: B01L 2300/0636 Integrated biosensor, microarrays
• CPC Class Codes: B01L 2300/0645 Electrodes
• CPC Class Codes: B01L 2300/0672 Integrated piercing tool
• CPC Class Codes: B01L 2300/0816 Cards, e.g. flat sample carriers usually with flow in two horizontal directions
• CPC Class Codes: B01L 2300/0867 Multiple inlets and one sample wells, e.g. mixing, dilution
• CPC Class Codes: B01L 2300/0887 Laminated structure
• CPC Class Codes: B01L 2400/0406 capillary forces
• CPC Class Codes: B01L 2400/0683 mechanically breaking a wall or membrane within a channel or chamber
• CPC Class Codes: B01L 2400/0688 surface tension valves, capillary stop, capillary break
• CPC Class Codes: B01L 2400/086 using baffles or other fixed flow obstructions
• CPC Class Codes: B01L 3/5027 by integrated microfluidic structures, i.e. dimensions of channels and chambers are such that surface tension forces are important, e.g. lab-on-a-chip B01L3/5023 takes precedence; micromixers B01F33/30; microreactors for synthesis B01J19/0093; microcapillary devices in general B81B1/00
• CPC Class Codes: B01L 3/502715 characterised by interfacing components, e.g. fluidic, electrical, optical or mechanical interfaces
• CPC Class Codes: B01L 3/502746 characterised by the means for controlling flow resistance, e.g. flow controllers, baffles B01L3/502738 takes precedence
• 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
• CPC Class Codes: B01L 3/502769 characterised by multiphase flow arrangements
• CPC Class Codes: B01L 9/527 for microfluidic devices, e.g. used for lab-on-a-chip
• CPC Class Codes: G01N 33/54326 Magnetic particles
• CPC Class Codes: G01N 33/54366 Apparatus specially adapted for solid-phase testing
• CPC Class Codes: G01N 33/558 : using diffusion or migration of antigen or antibody immunochromatographic test strips G01N33/54387
• CPC Class Codes: G01N 35/0098 : involving analyte bound to insoluble magnetic carrier, e.g. using magnetic separation magnetic particles used in immunoassays G01N33/54326; magnetic separation in general B03C

Abstract

An assay method and device can perform at least one (e.g., at least two) assays on a single aliquot of a sample liquid. The device can mix a sample liquid with assay reagents including magnetically susceptible particles. The device is configured to create a sample liquid-air interface with the sample liquid. The magnetically susceptible particles can be located (via an applied magnetic field) at the liquid-air interface when a second liquid contacts the interface to form a liquid-liquid interface. The magnetic particles travel across the liquid-liquid interface to the second liquid. The magnetically susceptible particles are configured to transport an analyte across the interface into the second liquid. An assay for the analyte is performed in the second liquid. An assay for another analyte can also be performed in the sample liquid.

Claims

1. A method of performing an assay to detect a presence of the natriuretic peptide in a first liquid sample comprising:

(a) introducing the first liquid sample to a first channel portion of a microfluidic device;

(b) contacting, within the microfluidic device, magnetically susceptible particles with the first liquid sample, the magnetically susceptible particles comprising a binding agent that specifically binds the natriuretic peptide in the first liquid sample;

(c) contacting a second binding agent with the first liquid sample, wherein the second binding agent specifically binds the natriuretic peptide at a different epitope to the binding agent of the magnetically susceptible particle to form complexes comprising the magnetically susceptible particles, the natriuretic peptide and the second binding agent, wherein the second binding agent is conjugated to a detectable label;

(d) forming, proximal to a junction between the first channel portion and a second channel portion of the microfluidic device, a first liquid sample;

gas interface;

(e) forming a first liquid sample;

second liquid interface by displacing gas of the first liquid sample;

gas interface with a second liquid;

(f) magnetically moving the magnetically susceptible particles across the first liquid sample;

second liquid interface into the second liquid in the second channel portion; and

(g) detecting the complexes containing the natriuretic peptide in the second channel portion based on the activity of the detectable label.

2. The method of claim 1 wherein the first and second liquids are different, and wherein the first liquid sample is bodily fluid from a human or mammal.

3. The method of claim 1 wherein the detecting step (g) further comprises determining an amount of the natriuretic peptide based on the activity of the detectable label and displaying the determined amount of the natriuretic peptide.

4. The method of claim 3, further comprising comparing the amount of the natriuretic peptide determined against a reference amount to determine a result of the assay.

5. The method of claim 1 wherein the binding agent is a first antibody configured to bind the natriuretic peptide, and wherein the second binding agent is a second antibody configured to bind the natriuretic peptide at a different epitope to the first antibody.

6. The method of claim 1 wherein the step of magnetically moving the magnetically susceptible particles across the first liquid sample:

second liquid interface into the second liquid comprises applying a magnetic field to a first position in the first channel portion, and moving the applied magnetic field along the channel through the junction to a second position in the second portion of the channel.

7. The method of claim 1 wherein during the forming step (e), the first-liquid sample:

second liquid interface is formed by directing a flow of the second liquid across a face of the first liquid sample at the first liquid sample;

gas interface to decrease an area of the first liquid sample;

gas interface, the first liquid sample is held substantially static, and substantially no bulk movement of the first or second liquid occurs across the interface.

8. The method of claim 1 wherein the magnetically moving step (f) further comprises magnetically positioning the magnetically susceptible particles adjacent one or more electrodes configured in the second channel portion to contact the second liquid and wherein the detecting step (g) further comprises:

a. measuring at time T₁ a first electrochemical signal Q₁ at a working electrode of the one or more electrodes;

b. comparing Q₁ against a T₁ calibration dataset and, where Q₁ is within the T₁ dataset, using the T₁ dataset to determine the amount of the natriuretic peptide in the first liquid sample;

c. where Q₁ does not exist in the T₁ calibration dataset, measuring at time T₂ a second electrochemical signal Q₂ at the working electrode, wherein T₂>

T₁; and

d. comparing Q₂ against a T₂ calibration dataset and where a comparison of Q₂ and T₂ is made, determining the amount of the natriuretic peptide in the first liquid sample.

9. The method of claim 1, wherein the first liquid sample:

gas interface has a cross sectional area of about 1 mm2 or less and wherein the first liquid sample;

gas interface has a first dimension H and a second dimension W and a ratio of W to H is 30 or less and wherein the first liquid sample;

second liquid interface has a cross sectional area of about the same as the first liquid sample;

gas interface or less.

10. The method of claim 9, wherein the first liquid sample:

gas interface has a cross sectional area of about 0.15 mm2 or more.

11. The method of claim 1, wherein, upon forming the first liquid sample:

gas interface, the first liquid sample occupies a total volume V of the channel upstream of the first liquid sample;

gas interface and the method comprises mixing the first liquid sample by magnetically moving the magnetically susceptible particles within the total volume V after forming the first liquid sample;

gas interface and prior to forming the first liquid sample;

second liquid interface, wherein V is about 2 l to about 20 l.

12. The method of claim 11, wherein V is about 5 μ

l.

13. The method of claim 11, wherein V is about 7 μ

l.

14. The method of claim 11, wherein V is about 9 μ

l.

15. The method of claim 11, wherein V is about 15 μ

l.

16. The method of claim 11, wherein V is about 20 μ

l.

17. The method of claim 1 wherein the natriuretic peptide is a prohormone-brain natriuretic peptide (proBNP);

N-terminal truncated prohormone-brain natriuretic peptide (NTproBNP);

or brain natriuretic peptide (BNP).

18. The method of claim 1, wherein the first channel portion has a main channel height h1, and a channel height h′

1 at the junction, wherein h1>

h′

1, and wherein the second channel portion has height h2 at the junction, wherein h2>

h1>

h′

1, and wherein the ratio of h1;

h2 is at least 1;

2.

19. The method of claim 1, wherein a ratio of a number of the magnetically susceptible particles that cross the first liquid sample:

gas interface to a number of the magnetically susceptible particles that cross the first liquid sample;

second liquid interface is less than 10%.

20. The method of claim 1 wherein the first liquid sample is blood.

21. The method of claim 1 wherein the first liquid sample is serum.

22. The method of claim 1 wherein the first liquid sample is plasma.

23. The method of claim 1 further comprising washing non-magnetic material away from the complexes to ensure that only material associated with the magnetically susceptible particles is detected.

24. The method of claim 1 further comprising verifying the activity of the detectable label by measuring activity of a predetermined quantity of immobilized detectable label at a control region in the microfluidic device.

25. A method of performing an assay to detect the presence of a natriuretic peptide in a first liquid sample comprising:

(a) introducing the first liquid sample to a first channel portion of a microfluidic device;

(b) contacting, within the microfluidic device, magnetically susceptible particles with the first liquid sample, the magnetically susceptible particles comprising a binding agent that specifically binds the natriuretic peptide in the first liquid sample, wherein the binding agent is conjugated to a detectable label;

(c) forming complexes comprising the magnetically susceptible particles, the natriuretic peptide and the binding agent conjugated to the detectable label;

(d) forming, proximal to a junction between the first channel portion and a second channel portion of the microfluidic device, a first liquid sample;

gas interface;

(e) forming a first liquid sample;

second liquid interface by displacing gas of the first liquid sample;

gas interface with a second liquid,

(f) magnetically moving the magnetically susceptible particles across the first liquid sample;

second liquid interface into the second liquid;

(g) washing the complexes to remove non-complexed material so that only material associated with the complexes is detected; and

(h) verifying the activity of the detectable label by measuring activity of a predetermined quantity of immobilized detectable label at a control region in the microfluidic device and detecting the complexes containing natriuretic peptide in the second channel portion based on the activity of the detectable label in the complexes.