IES81115B2 - A device for detecting analytes in biological samples - Google Patents

Abstract

A device for detecting analyte in a biological sample comprising an extraction chamber for extracting analyte from the sample and holding the extracted analyte and a holding means located over the extraction chamber for holding a matrix in communication with the extracted analyte in a perpendicular disposition.

Description

A device for detecting analytes in biological samples This invention relates to a device for detecting analytes in biological samples, to a device for performing chemical and binding assays between an antigen and an antibody on an analyte and in particular to a device for performing immunochromatographic assays on an analyte.

Many devices and methods exist for detecting analytes in biological samples. Examples of such devices include dipsticks, lateral flow devices and flowthrough devices.

In dipstick devices, a plastics strip is generally employed having a reagent-containing matrix layer on the plasti^^^^g. The presence of an analyte is detected by applying a test sample to the device and by visually detecting a signal such as a colour forming reaction on the device. In flow-through devices, a poroUs matrix material is usually employed with a reagent containing matrix thereon. Analyte in a sample is detected by applying a test sample to the porous material and detecting a reaction signal between the reagents and the analyte on the porous material. Flow through and dipstick devices are usually housed in plastics housings or casings and sample is drawn through the device in a substantially perpendicular direction.

A porous matrix is employed in lateral flow assays to detect analytes. However, in lateral flow assays, sample flows laterally from an application zone to a reaction zone on the membrane surface as opposed to in a perpendicular direction.

The aforementioned devices are frequently employed in clinical medicine for the detection of pathogens in biological samples. In particular, it is increasingly desirable that such assays can be carried out by a physician during a consultation with a patient so that an immediate diagnosis can be made instead of dispatching samples to a laboratory for analysis which can give rise to delays in diagnosis. Accordingly, where it is desirable for an analysis to be carried out by a physician, devices suitable for rapid and simple detection of analytes are required. Moreover, such devices should be capable of simple physical manipulation by a physician.

In general, for many assays, pre-treatment of a biological sample is required. When such pre-treatment must be performed by the physician, it is desirable that the pre-treatment step should be as simple as possible without requiring multiple transfers from container to container during pre-treatment and/or analysis.

Finally, where it is necessary to locate a pre-treated 5 sample on a matrix for immunochromatographic detection and the like, it is desirable that the location step should not require a high degree of accuracy nor complex physical manipulation.

U.S. Patent Specification No. 5,712,172 describes a lateral flow immunochromatographic assay device without a plastics housing. However, the immunochromatographic device does not comprise a holder for holding the immunochromatographic device in use. Moreover, a biological sample requiring analysis using the immunochromatographic device of U.S. Patent Specification No. 5,712,172 requires pre-treatment in a separate container.

U.S. Patent Specification No. 5,415,994 describes a device for the one step treatment and detection of analytes in samples requiring pre-treatment. As with U.S. Patent Specification No. 5,712,172, analysis is carried out in a lateral flow diagnostic assay method while a pre-treated sample must travel from a sample bowl to a sample receiving zone on a matrix through an exit port in the device. Such exit ports can become blocked in use, while the device of U.S. Patent Specification No. 5,415,994 can require manipulation to effect movement of low volume sample between the bowl and the matrix.

An object of the invention is to overcome the problems of the prior art.

A further object of the invention is to provide a device for detecting analytes in biological samples.

According to the invention there is provided a device for detecting analyte in a biological sample comprising an extraction chamber for extracting analyte from the sample and holding the extracted analyte and a holding means located over the extraction chamber for holding a matrix in communication with the extracted analyte in a perpendicular disposition.

Preferably, the extraction chamber comprises a chamber defined in a base holder having a flat bottom wall for locating the device on a flat surface.

Suitably, the holding means comprises a mouth upstanding from the base holder and communicable with the extraction chamber.

Preferably, the mouth is communicable with the extraction chamber through an opening disposed between the extraction chamber and the mouth.

Advantageously, the extraction chamber further 5 comprises baffles for extracting analyte from a swab.

Suitably, the holding means further comprises a stop means for stopping the matrix in communication with the extracted analyte in a perpendicular disposition.

Preferably, the stop means comprises a shoulder disposed between the holding means and the extraction chamber.

Advantageously, the base holder comprises a window for viewing the extraction chamber. Suitably, the window is defined by frosting on the base holder.

The invention also extends to a device for detecting analyte in a biological sample comprising an extraction chamber for extracting analyte from the sample and holding the extracted analyte, a holding means located over the extraction chamber and a matrix holdable in the holding means in communication with the extracted analyte in a perpendicular disposition.

Preferably, the matrix is adapted for immunochromatographic analysis.

The advantages of the invention are many. The device of the invention can be used as an aid in the diagnosis of infections where disease specific antigens can be sampled directly from a patient using a swab. The holder of the device of the invention is adapted to facilitate the carrying out of a diagnostic assay in the perpendicular disposition. More particularly, the holder of the invention facilitates the holding of a matrix in a perpendicular disposition to facilitate analyses such as immunochromatographic analyses.

The holder of the device of the invention is also adapted to facilitate extraction of an analyte and analysis of the extracted analyte in a single container without requiring transfer between containers.

Moreover, the holder of the invention is provided with an extraction chamber fitted with baffles to facilitate extraction of analyte from swabs and, the like.

The holder of the invention is in particular adapted to receive a matrix for use in analyses in stick form to secure the matrix in situ in a perpendicular disposition without requiring complex physical manipulation of the matrix.

The holder of the invention is typically formed from a plastics material such as polystyrene which can be frosted to create windows in the holder to facilitate viewing of the extraction chamber. Frosting of the plastics materials, particularly on the flat base of the holder, enhances the grip of the holder with a flat surface.

An embodiment of the invention will now be described by way of example only having regard to the accompanying drawings, in which: Fig. 1 is a perspective view from above and one side of holder device for detecting analytes in biological samples in accordance with the present invention; Fig. 2 is a perspective view from above and one side of an immunoassay stick for insertion into the holder of Fig. 1; Fig. 3 is a front elevation of the immunoassay stick of Fig. 2 inserted in the holder of Fig. 1 shown in cross-section; Fig. 4 is a side elevation of the immunoassay stick and holder of Fig. 3; Fig. 5 is a front elevation of the holder; Fig. 6 is a side elevation of the holder; Fig. 7 is a top elevation of the holder without baffles; Fig. 8 is a top elevation of the holder with baffles; Fig. 9 is a cross-sectional view along the line IX - IX of Fig. 8, and Fig. 10 is a cross-sectional view through the 10 holder along the line X - X of Fig. 9.

As shown in the drawings, a device for detecting analytes in biological samples of the invention is made up of a holder generally indicated by the reference numeral 1 for holding a immunoassay stick 26 in a substantially perpendicular disposition.

The holder 1 is made up generally of an extractor chamber portion 2 in communication with a stick holder portion 3 located over and on the extraction chamber portion 2. The extraction chamber portion 2 is defined 0 by a bottom wall 4 having a front wall 5, a rear wall 6 and first and second side walls 7,8 upstanding therefrom.

The bottom wall 4 is substantially ellipsoidal in shape when viewed in plan while the front wall 5 and rear wall 6 are upstanding from the bottom wall 4 in an outwardly curved manner.

The holder 1 of the invention is typically formed from a plastics material such as polystyrene. As shown in the drawings, the bottom wall 4, the front wall 5, the rear wall 6, the first side wall 7 and the second side wall 8 are frosted to render the material of the holder opaque where the material is an inherently transparent plastics. However, the front wall 5 and the rear wall 6 of the holder 1 are provided with a front window 9 and a rear window 10 respectively so that the interior of the holder 1, and in particular the extraction chamber portion 2, may be clearly viewed from the exterior of the holder 1.

The stick holder portion 3 of the holder 1 extends perpendicularly upwards from the extraction chamber portion 2. The stick holder portion 3 is substantially rectangular in shape when viewed in plan from above and is defined by a stick holder front wall 11, a stick holder rear wall 12, a stick holder first side wall 13 and a stick holder second side wall 14 connecting the stick holder front wall 11 and the stick holder rear wall 12. Accordingly, the extraction chamber portion 2 front wall 5, rear wall 6, first side wall 7 and second side wall 8 extend laterally downwards and outwards from the respective stick holder front wall 11, stick holder rear wall 12, stick holder first side wall 13 and stick holder second side wall 14 respectively.

The stick holder front wall 11, stick holder rear wall 12, stick holder first side wall 13 and the stick holder second side wall 14 together define a mouth 15 for facilitating access to the stick holder portion 3 and the extraction chamber portion 2. The stick holder front wall 11 and the stick holder rear wall 12 are each provided with upwardly curved portions 16,17 at their free end to further enhance support of the immunoassay stick 26 within the stick holder portion 3.

Internally, the extraction chamber portion 2 is provided with a sample chamber 18 located between the front wall 5, rear wall 6 and first and second walls 7,8 respectively of the extraction chamber portion 2.

The sample chamber 18 functions as a pre-treatment chamber for pre-treating biological samples prior to analysis with the immunoassay stick 26 and also as a receptacle for the sample to be analysed with the immunoassay stick 26.

The sample chamber 18 is substantially square when viewed in plan from above and is defined by a bottom wall 19 disposed in a plane substantially parallel to the plane defined by the bottom wall 4 of the extraction chamber portion 2, and a front wall 20, a rear wall 21, a first side wall 22 and a second side wall 23 upstanding from the bottom wall 19 of the sample chamber 18. The sample chamber 18 is provided with an opening 35 for communicating with the stick holder portion 3. A stop shoulder 25 is defined either side of the opening 35 of the sample chamber 18 to abut against the immunoassay stick 26 upon insertion of the immunoassay stick 26 into the stick holder portion 3.

Internally, the sample chamber 18 is provided with baffles 24 for facilitating extraction of analytes from swabs and the like in use as shall be explained more fully below. The baffles 24 are made up of diagonally inwardly disposed plates 36 which extend diagonally inwards from each corner defined between the front wall 20, rear wall 21, first side wall 22 and second side wall 23 of the sample chamber 18. Each plate 36 is substantially triangular in shape with an inclined face of each plate 36 disposed inwards within the sample chamber 18.

As indicated above, the holder 1 of the invention is adapted to receive an immunoassay stick 26 in the stick holder portion 3. A suitable immunoassay stick 26 is shaped and dimensioned to be received within the stick holder portion 3 and is substantially plate-like in construction. More particularly, the immunoassay stick 26 comprises a top member 27 and a bottom member 28 adapted to support a wick-like matrix 29 therebetween. The wick-like matrix is adapted to effect immunochromatographic analysis on a sample for the diagnosis of infections and the like. However,· as will be appreciated by those skilled in the art, the holder 1 of the invention is suitable for use in performing other assay types for detecting analytes in biological samples but nevertheless is particularly adapted for binding assays of the immunochromatographic type.

The wick-like matrix 29 is secured between the top member 27 and the bottom member 28 and is strip-like in shape and further comprises a wick-like matrix extension 30 which protrudes from a slot 34 defined between the top member 27 and the bottom member 28. The wick-like matrix extension 30 is dimensioned and shaped to be receivable in the sample chamber 18 of the extraction chamber portion 2.

The top member 27 is provided with a .control window 31 and a sample window 32 located intermediate the control window 31 and the wick-like matrix 29 so that the wicklike matrix 29 between the top member 27 and the bottom member 28 is visible to effect a diagnosis. As indicated previously, the device for detecting analytes and biological samples of the invention is particularly adapted for immunochromatographic assays to be carried out by physicians during a consultation with a patient. The invention has particular application in the analysis of infections such as beta-haemolytic Group A Streptococcus bacterial infection in humans, Chlamydia Trachomatous infections and the like. However, it will be appreciated by those skilled in the art, that the device for detecting analytes and biological samples of the invention can have multiple applications in the diagnosis and assay of many infections.

For example, in immunochromatographic tests for infections such as the aforementioned beta-haemolytic Group A Streptococcus infection, a swab is taken from a patient's throat and an assay performed on the sample on the throat swab. More particularly, Group A Streptococcus antigen is extracted directly from the swab and identified using Group A Streptococcus antigen specific antibodies. Typically, the method employs a combination of anti-Streptococcus A polyclonal antibody using a colloidal gold dye conjugate and polyclonal solid phase to selectively identify Streptococcus A.

The assay is performed on the wick-like matrix 29 in which extracted sample is allowed to flow through an absorbent pad on the wick 29 during which time labelled antibody-dye is bound to Streptococcus A antigen if present thereby forming an antibody-antigen complex.

In use, the anti gen-antibody complex is moved along the wick-like matrix 29 and a line of immobilised complex is formed at a test line in the sample window 32. The test line is made up of a pink/red colour line to indicate the presence of Streptococcal A. In the absence of Streptococcal A antigen no line becomes visible.

The wick-like matrix 29 is provided with an in-built procedural and positive control at the control window to ensure that the test has been performed correctly and that all reagents employed in the test are functional. The positive control consists also of a pink/red line visible in the control window 31 to indicate that an assay has been performed correctly.

Accordingly, in the analysis of a Streptococcal A infection, a physician is normally provided with a reagent A (containing 0.2M acetic acid) and reagent B (containing 4M sodium nitrite) together with a swab and an immunoassay stick 26 fitted with a suitable wick matrix 29 and a conjugate pad. In practise, the immunoassay stick 26 and the holder 1 will be provided in a sealed and sterile foil-type pouch.

A typical assay procedure employing the holder 1 of the invention together with the immunoassay stick 26 of the device in the form of a device for detecting analytes in biological samples is as follows: 1. The immunoassay stick 26 and the holder 21 are removed from their foil pouch. In general, the immunoassay stick 26 will be inserted in the holder 1 prior to use for ease of packaging. The holder 1 is placed on a flat surface with the stick 26 disposed in a perpendicular disposition. 2. The immunoassay stick 26 is removed from the holder 1. 3. Typically five drops of reagent A and five drops of reagent B are placed in the sample chamber 18 of the extraction chamber portion 2 of the holder 1. 4. The throat swab from which a sample is to be analysed is placed in the extraction chamber portion 2 so that the tip of the swab is located in the sample chamber 18.

. The contents of the extraction chamber 18 are mixed thoroughly with the swab by agitating the swab against the baffles 24 to effect extraction of analyte from the swab. The holder 1 together with the swab inserted in the sample chamber 18 is then incubated at room temperature for approximately three minutes. Accordingly, the holder 1 also serves to support the swab 1 in a self standing manner during incubation. 6. Following incubation, the swab is removed and discarded. 7. The immunoassay stick 26 is then inserted through the mouth 15 to the stick holder portion 3 of the holder 1. 8. As indicated above, if the extracted sample contains Streptococcal A antigen a positive result is indicated on the immunoassay stick 26 by a pick/red line in the sample window 32.

The invention is not limited to the embodiments herein described which may be varied in construction and detail.

Claims (5)

1. A device for detecting analyte in a biological sample comprising an extraction chamber for extracting analyte from the sample and holding the extracted 5 analyte and a holding means located over the extraction chamber for holding a matrix in communication with the extracted analyte in a perpendicular disposition.

2. A device as claimed in Claim 1 characterised in that the extraction chamber comprises a chamber defined 10 in a base holder having a flat bottom wall for locating the device on a flat surface.

3. A device as claimed in Claim 2 characterised in that the holding means comprises a mouth upstanding from the base holder and communicable with the 15 extraction chamber.

4. A device as claimed in Claim 3 characterised in that the mouth is communicable with the extraction chamber through an opening disposed between the extraction chamber and the mouth. 20

5. A device as claimed in any of Claims l to 4 characterised in that the extraction chamber further comprises baffles for extracting analyte from a swab.