WO2001002854A1

WO2001002854A1 - Analyte detection

Info

Publication number: WO2001002854A1
Application number: PCT/AU2000/000782
Authority: WO
Inventors: Leslie Robert Watson; Peter Leonard Devine; Denise Phuong Phi Rowland
Original assignee: Panbio Pty Ltd
Priority date: 1999-07-06
Filing date: 2000-06-30
Publication date: 2001-01-11
Also published as: AUPQ145599A0

Abstract

An analyte detection apparatus and body thereof is provided, the body having releasably engageable body portions, the body capable of encapsulating a detections means, preferably in the form of a test strip. The releasably engageable body portions allow containment of the detection means before and after addition of a sample foranalyte detection, thereby minimizing exposure of the environment and user to the analyte and sample, the contents of which may be harmful. The detection means may be immobilized such as by constrictions or clamping in the body. Also provided is a method of analyte detection and a detection means having more than one visible readout.

Description

TITLE "ANALYTE DETECTION" FIELD OF THE INVENTION THIS INVENTION relates to an analyte detection apparatus, a test strip and body suitable for use therewith and a method of detecting an analyte. In particular, this invention relates to diagnostic detection of an analyte in a fluid sample, such as a clinical sample or specimen, without being limited thereto.

BACKGROUND OF THE INVENTION Rapid and efficient detection of analytes in samples is crucial to forensic, medical diagnostic and other analytical applications.

Such analytes may include viruses, bacteria, antibodies, proteins, carbohydrates, iipids, nucleic acids, pesticides, herbicides and other organic molecules, inorganic molecules, heavy metals and the like. Analytes may be contained within samples comprising body fluids such as blood, plasma, serum, saliva, cerebrospinal fluid, amniotic fluid, urine, semen, or in samples comprising water, effluent, soil extracts and the like.

A particularly well-known analyte detection means is a test strip such as described in United States Patent No. 4,855,240. The test strip is usually an elongate strip of nitrocellulose which comprises ^' a sample addition region adjacent to a tracer region, and a readout region distal thereto. Typically, a sample is placed at the sample addition region, binds tracer to form a complex, and travels along the test strip by capillary action until captured by a binder impregnated in, or otherwise associated with, the test strip matrix in the readout region. Formation of the complex is typically visualized by formation of color at the readout region.

Examples of tracers include colloidal gold, latex, dyes, pigments or colorable proteins such as phycoerythrin or ferritin. The binder may be an antibody or other molecule which can specifically bind the tracer or analyte to enable formation of the color readout.

A modification of this test strip is provided in United States Patent No. 5,075,078, wherein the visual readout is in a simplified (+) or (-) form to prevent "subjective" misjudgement by the operator.

A feature of the aforementioned test strips is that they may react with oxygen or water in the air, and it is generally required that the strip be housed inside a protective film impermeable to air oxygen and humidity.

An example of a housed test strip may be found in International Publication No. WO99/05526, in which the test strip is fixed to a backing material with an oxygen and humidity-resistant coating, and is covered by a film such as aluminium foil with an oxygen and humidity- resistant coating. The film is sealed to the backing material around the perimeter of the test strip. In use, the film is detached from the backing material to reveal the test strip so that analyte detection can be performed. However, a problem with this analyte detection apparatus is that analyte detection is performed in an open environment, thereby potentially subjecting the operator to harmful substances within the sample. Furthermore, after use the test strip must be disposed of as hazardous waste to prevent inadvertent release of harmful substances from the test strip to the environment. It should also be appreciated that manufacturing an analyte detection apparatus such as provided in International Publication No. WO99/05526 is relatively complicated and therefore expensive.

OBJECT OF THE INVENTION The present inventors have unexpectedly devised an analyte detection apparatus which provides more protection from potentially harmful substances to an operator or to the environment in use and upon disposal. Furthermore, the apparatus is simple to use and relatively cost-effective to manufacture. It is therefore an object of the invention to provide an analyte detection apparatus and body thereof. It is another object of the invention to provide a method of detecting an analyte.

SUMMARY OF THE INVENTION In one aspect, the present invention provides a body of an analyte detection apparatus comprising at least first and second body portions which are releasably engageable, wherein said body is capable of encapsulating a detection means.

In another aspect, the present invention provides an analyte detection apparatus comprising a body and a detection means, said body comprising at least first and second body portions which are releasably engageable, wherein said body is capable of encapsulating said detection means

In yet another aspect there is provided a method of detecting an analyte including the steps of:- (i) contacting a sample suspected of containing said analyte with a detection means; (ii) encapsulating said detection means; and (iii) detecting said analyte before or after step (ii). In still yet another aspect, the invention provides a detection means having more than one readout region.

Preferably, the body is formed of a transparent material to assist visual inspection of said detection means.

Preferably, the transparent material is a synthetic polymer such as plastic, PVC, polyethylene, polycarbonate or the like. In an embodiment, the body is substantially impermeable to oxygen and humidity to prevent deterioration of said detection means prior to use.

In another embodiment, the body is not impermeable and is provided in an oxygen and humidity-resistant package such as described in International Publication No. WO99/05526, which is herein incorporated by reference. Preferably, the body comprises body portions which are teiescopically engageable. A particular advantage of telescopic engagement is that the detection means, when encapsulated by the body portions so engaged, is effectively sealed to the environment before and after analyte detection, while readily allowing disengagement of the body portions.

In yet another embodiment said body comprises a first body portion and a second body portion.

Preferably, the first and second body portions are releasably engageable by virtue of respective complementary ends.

Preferably, the respective complementary ends facilitate telescopic engagement of the first and second body portions. In such a case, the respective complementary ends may be substantially cylindrical, cuboid, triangular, pentagonal, hexagonal or octagonal in cross-section or any other complementary shape or configuration which permits telescopic engagement.

Preferably, the respective complementary ends are substantially cylindrical.

In still yet another embodiment, the body has first, second and third body portions.

Preferably, said second body portion is located intermediate said first and third body portions when releasably engaged therewith.

Preferably, one end of said second body portion is releasably engageable with a complementary end of the first body portion and another end of said second body portion is releasably engageable with a complementary end of the third body portion.

Preferably, the respective complementary ends facilitate telescopic engagement of the second body portion with the first and third body portions. In such a case, the respective complementary ends may be substantially cylindrical, cuboid, triangular, pentagonal, hexagonal or octagonal in cross-section or any other complementary shape or configuration which permits telescopic engagement.

Preferably, the respective complementary ends are substantially cylindrical.

It will be appreciated that the body is capable of encapsulating the detection means, such as when said body portions are releasably engaged.

Preferably, the detection means is immoblilized within said body or within said first body portion and/or said second body portion. Immobilization restricts movement of the detection means in the body and thereby maintains the detection means in the correct orientation. Furthermore, immobilization prevents the detection means from inadvertently being removed or otherwise detached from the body and causing a waste disposal problem. This is particularly important if the detection means has been used to detect a potentially harmful analyte. In one embodiment, the detection means is immobilized by being clamped at a tapered end of said body.

In another embodiment the detection means is immobilized by one or more constrictions in said body.

Preferably, the detection means is a test strip having a sample loading region, a tracer region, and a readout region.

The detection means may be formed of glass fiber, cellulose, nitrocellulose, nylon, cross-linked dextran, or chromatographic papers.

Suitably, the detection means allows capillary flow of said sample when applied to the sample loading region. Preferably, an absorbent pad is included at an end of said detection means distal to said sample loading region. The absorbent pad is particularly required when a relatively large volume of sample is to be added to the sample loading region. Alternatively, absorbent material is located in said third body portion distal to said sample loading region.

It will be appreciated from the foregoing that a well known example of a detection means according to the present invention is a "test strip".

Examples of detection means in the form of test strips are provided in United States Patent Nos. 4,855,240 and 5,075,078, and International Publication No. WO99/05526 which are herein incorporated by reference.

Preferably, the detection means includes at least a tracer region and a binder.

It will be appreciated by the skilled person that a variety of tracers and binders may be used in the detection means of the invention. The particular tracer and binder used will depend on the analyte to be detected.

Tracers include colloidal gold or other metals or alloys thereof, latex, dyes, pigments, chlorophylls, colorable proteins such as ferritin, phycoerythrin and other phycobiloproteins. A discussion of suitable tracers can be found, for example, in United States Patent No. 4,373,932, which is herein incorporated by reference, as well as the aforementioned references.

Suitable binders include antigens, antibodies, hormone- binding proteins, enzymes, nucleic acid binding proteins and any other molecule capable of specifically binding a tracer or analyte to be detected.

Suitably, the detection means is visually inspected for a readout. Typically, test strips have a readout region on one face of the strip, and hence are only visible when that particular face of the strip is facing an observer.

Therefore, according to said yet another aspect, the detection means has more than one readout region.

In one embodiment, the detection means has a visible readout region on opposed faces, thereby in use facilitating easier visual inspection of the readout region. In a particular embodiment, the detection means includes a pair of test strips attachable to a backing plate to facilitate detection of a readout on opposed faces thereof.

In another embodiment, the detection means is in the form of a test strip having a sample loading region intermediate respective readout regions.

There are several preferred ways contemplated whereby said sample suspected of containing said analyte is contacted with said detection means: -

(i) the sample is added to the first body portion, following which the first and second body portions are releasably engaged to thereby contact the sample with the sample loading region of the detection means;

(ii) sample is added to a well formed by a constriction in the second body portion, the sample loading region of the detection means being located inside the well; (iii) sample loading is achieved by immersing the sample loading region of the detection means into a sample located in a well of a microtitre plate; and (iv) where the body has first, second and third portions, the detection means is located substantially within the second body portion and has the sample loading region distal to the tracer region, sample being applied directly to the sample loading region. With regard to (iv), after sample loading, the second body portion is inverted and buffer applied to the tracer region to permit flow of the tracer to the readout region, thereby forming a color readout if the tracer encounters an analyte-binder complex formed at the readout region. The method and apparatus of the invention is applicable to detecting analytes such as viruses, bacteria, antibodies, proteins, carbohydrates, lipids, nucleic acids, pesticides, herbicides and other organic molecules, inorganic molecules, heavy metals and the like. Suitably, analytes may be contained within fluid samples comprising body fluids such as blood, plasma, serum, saliva, cerebrospinal fluid, amniotic fluid, urine, semen, or in samples comprising water, effluent, soil extracts and the like.

It will therefore be appreciated that the present invention provides an apparatus which not only provides a simple means of detecting an analyte, but also an environmentally safe means. In this regard, the detection means may be enclosed within the body before and after use. The preferred means of releasable engagement, namely telescopic engagement, is particularly effective in this regard. Generally, analyte detection may be performed in what is effectively a sealed body, so that there is minimal exposure to any harmful substances in said sample. Furthermore, this facilitates safe disposal of said apparatus because such potentially harmful substances are contained within the apparatus during use and when disposed of.

Throughout this specification and claims which follow, unless otherwise indicated, "comprise", "comprises" and "comprising" are used inclusively rather than exclusively, so that a stated integer or group of integers may include one or more other non-stated integers or groups of integers.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a side elevation view of one embodiment of an analyte detection apparatus;

FIG. 2 is a side elevation view of another embodiment of an analyte detection apparatus together with a plan view through section A- A;

FIG 3 is a plan view of an analyte detection apparatus comprising first, second and third body portions;

FIG. 4 is a plan view (A) and a side elevation view (B) of a packaged analyte detection apparatus;

FIG. 5 is a perspective view of a detection means in the form of a single test strip;

FIG 6 is an exploded view of a detection means in the form of a two test strips attached to a backing plate; and

FIG. 7 is (A) a plan view of a detection means in the form of a test strip having respective readout regions; (B) a perspective view of the detection means in (A) with an exposed sample loading region; and (C) a packaged detection means. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

Referring to FIG. 1 , analyte detection apparatuslO comprises body 11 having second body portion 12 with wall 13 and interior 14; first body portion 15 having wall 16 and interior 17. Second body portion 12 has tapered end 18 and substantially cylindrical end 1 ; first body portion 15 has tapered end 20 and substantially cylindrical end 21. In FIG. 1A, first body portion 15 and second body portion 12 are teiescopically engaged via complementary ends 21 and 19, which in this case are respectively substantially cylindrical, end 21 being received by end 19. Encapsulated by body 11 is detection means 22, in the form of test strip 23. Test strip 23 is immobilized by clamping at tapered end 18 of second body portion 12 and extends therefrom substantially beyond rim 24 of wall 13 of second body portion 12 and into first body portion 15.

In FIG. 1 B, second body portion 12 and first body portion 15 are disengaged, wherein fluid sample 25 has been added to first body portion 15.

To facilitate analyte detection, first portion 15 and second portion 12 are teiescopically engaged as n FIG. 1A so that sample 25 contacts sample loading region 26 of test strip 23. This also effectively seals apparatus 10, thereby protecting the operator from harmful substances in sample 25 and preventing leakage of sample 25 from apparatus 10 when disposed of. Referring to FIG. 2, analyte detection apparatus 10 comprises body 11 having second body portion 12 and first body portion 15 as in FIG. 1. In FIG. 2A, second body portion 12 and first body portion 15 are teiescopically engaged via respective complementary ends 21 and 19. Second body portion 12 includes constriction 27 which creates well 28 into which sample 25 is loaded, as shown in FIG. 2B. Immobilized inside body 11 is test strip 23 clamped by tapered end 18 of second body portion 12 and extending therefrom into well 28.

Sample loading region 26 of test strip 23 is located inside well 28 so that when fluid sample 25 is loaded into well 28, sample 25 moves by capillary flow from sample loading region 26 along strip 23. Referring to cross-sectional view through A-A at constriction 27, test strip 23 extends into well 28 while spaces 29A and 29B allow air to exit first portion 12 and thereby assist capillary flow of sample 25 along test strip 23.

During analyte detection and for the purpose of disposal, first portion 15 and second portion 12 are teiescopically engaged to thereby effectively seal apparatus 10 as already described.

Referring to FIG 3, there is shown an embodiment where apparatus 10 has body 1 1 comprising first 15, second 12 and third 38 body portions, second body portion 12 being located intermediate first body portion 15 and third body portion 38 and telescopically-engageable therewith. Test strip 23 is located inside second body portion 12, and has sample loading region 26 located inside well 28A formed by constriction 27A and tracer region 30 located inside well 28B formed by constriction

27B. Third body portion 38 has absorbent material 39 located therein. In use, according to FIG 3B first body portion 15 is disengaged from second body portion 12, and sample (not shown) is added to sample loading region 26 in well 28A. Sample flows by capillary action along test strip 23 toward absorbent material 39 until reaching readout region 32. Binder is located at readout region 32, and if analyte is present, a complex forms between analyte and binder. As shown in FIG 3C, second body portion 12 is then disengaged from third body portion 38, inverted, and buffer (not shown) added to tracer region 30 in well 28B, resulting in flow of tracer toward absorbent material 39 until the tracer reaches the analyte-binder complex, if present, resulting in formation of a visible readout at readout region 32.

This embodiment is particularly suited to analyte detection where flow of tracer and analyte would be slow or incomplete when occurring together in the same direction along the test strip. An example would be in immunoassays which detect large molecular complexes which contain IgM.

Referring now to FIG. 4, there is shown an embodiment where apparatus 10 is sealed from atmospheric oxygen and humidity by being packaged between cover 40 and substrate 41 , which each include an oxygen and/or humidity impermeable coatings 42 and 43 respectively. This embodiment is applicable when body 11 is constructed of a material not impermeable or resistant to oxygen and/or humidity.

Figures 5-7 illustrate various embodiments of detection means 22. In FIG. 5, there is shown test strip 23 which includes sample loading region 26 adjacent tracer region 30 and absorbent pad 31 distal to sample loading region 26.

Referring now to FIG. 6, detection means 23 comprises test strips 23A and 23B attached to backing plate 33. Test strips 23A and 23B comprise respective sample loading regions 26A, 26B, tracer regions 30A, 30B, absorbent pads 31 A, 31 B. Respective readout regions 32A, 32B are located intermediate tracer regions 30A, 30B and absorbent pads 31 A, 31 B. Each test strip 23A and 23B includes respective opposed faces 34A, 34B, and 35A, 35B, faces 34A and 34B having said respective readout regions 32A and 32B. In FIG. 7, there is shown an embodiment of detection means

22 in the form of test strip 23 having sample loading region 26 intermediate respective readout regions 32A and 32B and respective tracer regions 30A, 30B. Referring particularly to FIG. 7B, test strip 23 is housed within cover 44, preferably a laminate cover, which is frangible by way of perforation or score 45 located adjacent sample loading region 26. In FIG 7C, upper portion 46 and lower portion 47 of cover 44 encapsulate test strip 23 such as by heat sealing at perimeter 48. Preferably, cover 44 is oxygen- and humidity-resistant or impermeable. In use, by breaking cover 44 along perforation or score 45, sample may be added to sample loading region 26, exposed through broken perforation 45, for the purpose of analyte detection.

With regard to FIGS. 5-7, when fluid sample 25 contacts test strips 23A and 23B, or single test strip 23 at sample loading region 26, it moves by capillary action from sample loading region 26, through tracer region 30 and eventually to readout region 32. Absorbent pad 30 assists capillary flow in this regard. Readout region 32 in FIG. 5, or readout regions 32A, 32B in FIGS. 6 or 7, whichever is applicable, is/are where color development occurs, or where a +/- signal or other readout occurs which indicates to the operator that an analyte is or is not detected. With particular regard to FIG. 6 and FIG. 7, by having respective readout regions 32A, 32B in detection means 22, different analytes can be detected in the same sample 25, or the same analyte can be detected in sample 25. Referring particularly to FIG. 6 and FIG. 1 , enhanced visual detection from either side of body 11 of analyte detection apparatus 10 is also provided. Enhanced detection reduces the possibility of false positive or false negative results and improves the efficiency of analyte detection, particularly when a large number of samples are being handled.

It will be appreciated from the foregoing that the method and apparatus of the invention are applicable to detecting analytes such as viruses, bacteria, antibodies, proteins, carbohydrates, lipids, nucleic acids, pesticides, herbicides and other organic molecules, inorganic molecules, heavy metals and the like. In particular, the present invention is applicable to analytes contained within clinical or pathology samples samples and specimens comprising body fluids such as blood, plasma, serum, saliva, cerebrospinal fluid, amniotic fluid, urine, semen, or in samples comprising water, effluent, soil extracts and the like.

It will also be appreciated that the invention is not limited to the particular embodiments described in detail herein, and that a variety of different embodiments are contemplated which nevertheless fall within the scope and spirit of the invention.

Claims

I . A body of an analyte detection apparatus comprising at least first and second releasably engageable body portions, wherein said body is capable of encapsulating a detection means. 2. The body of Claim 1 comprising first, second and third body portions.

3. The body of Claim 1 , wherein said first body portion is teiescopically engageable with said second body portion.

4. The body of Claim 3, wherein said second body portion is teiescopically engageable with said first body portion and with said third body portion.

5. The body of Claim 1 , formed of a transparent material.

6. The body of Claim 1 , which is substantially impermeable to oxygen and humidity. 7. The body of Claim 1 , provided in an oxygen and humidity-resistant package.

8. The body of Claim 1 , having one or more constrictions therein.

9. The body of Claim 8, wherein the or each constriction forms a respective well in the body. 10. An analyte detection apparatus comprising a body and a detection means, said body comprising at least first and second releasably engageable body portions, wherein said body is capable of encapsulating said detection means.

I I . The analyte detection apparatus of Claim 10, said body comprising first, second and third body portions.

12. The analyte detection apparatus of Claim 10, wherein said first body portion is teiescopically engageable with said second body portion.

13. The analyte detection apparatus of Claim 11 , wherein said second body portion is teiescopically engageable with said first body portion and with said third body portion.

14. The analyte detection apparatus of Claim 10, wherein said detection means is immobilized within said body or within said first body portion and/or said second body portion.

15. The analyte detection apparatus of Claim 14, wherein the detection means is immobilized by being clamped by a tapered end of said body. 16. The analyte detection apparatus of Claim 14, wherein the detection means is immobilized by one or more constrictions in said body.

17. The analyte detection apparatus of Claim 16, wherein the detection means is immobilized by two constrictions in said body.

18. The analyte detection apparatus of any one of Claims 10-17, wherein the detection means has more than one readout region.

19. The analyte detection apparatus of Claim 18, wherein the detection means has respective said readout regions on opposed faces thereof.

20. The analyte detection apparatus of Claim 19, wherein the detection means comprises two test strips attached to a backing plate.. 21. The analyte detection apparatus of Claim 18, the detection means in the form of a test strip having a sample loading region intermediate respective readout regions.

22. A method of detecting an analyte including the steps of

(i) contacting a sample suspected of containing said analyte with a detection means;

(ii) encapsulating the detection means; and

(iii) detecting said analyte before or after step (ii).

23. The method of Claim 22, wherein at step (i), sample is added to a well, a sample loading region of the detection means being located inside the well.

24. The method of Claim 22 wherein at step (i) a sample loading region of the detection means is immersed into a sample located in a well of a microtitre plate.

25. The method of Claim 22, wherein a sample loading region of the detection means is located distal to a tracer region, so that at step (i) sample is applied directly to the sample loading region.

26. The method of Claim 25, wherein intermediate steps (ii) and (iii), the detection means is inverted and a buffer applied to the tracer region to permit flow of the tracer to the readout region.

27. A detection means having more than one readout region. 28. The detection means of Claim 27 having respective readout regions on opposed faces thereof.

29. The detection means of Claim 28 in the form of two test strips attached to a backing plate.

30. The detection means of Claim 27, in the form of a test strip having a sample loading region intermediate respective readout regions.