FIELD OF THE INVENTION
The present invention relates to an assay device with improved result visibility. More
particularly, the invention relates to a low cost, visible coloured indicator based assay
device with improved result visibility. The said assay device provides for detecting the
presence of one or more analytes in a given sample.
BACKGROUND OF THE INVENTION
Diagnostic devices in medical field have witnessed numerous advancements. The
advancements include those in sophistication, usability, reliability, simplification and
many more. One of the methods used in such diagnostic devices is chromatography
based assaying for detecting the presence of an analyte in a biological sample.
Such Chromatographic assay systems employed in rapid assay devices are one of several
means for detecting the presence of a given analyte in a biological sample. Such systems
are advantageous as the execution of these assays does not require any additional
specialized equipment or trained personnel. In addition to that, variety of analytes can
be detected using this type of assay. The use of rapid chromatographic techniques for
detection of the presence of an analyte in a biological sample have found utility beyond
the clinical laboratory, they are used in "point of care" situations such as the doctor's
office or even home settings.
The typical rapid chromatographic tests utilize either a "sandwich" assay or a
"competition" assay to detect the presence of a desired analyte. In the sandwich assay,
an analyte is bound, or "sandwiched," between an unlabeled first binding partner and a
labeled second binding partner. For example, an analyte, such as an antibody to HIV, can
be captured by a first binding partner, in this case, an HIV antigen immobilized on a
membrane. The antibody-antigen complex can then be detected by a second binding
partner having a label, such as another HIV antigen tagged with a coloured particle.
In contrast, during the competition assay, the analyte in the sample competes with a
labeled analyte, or labeled analogue to the analyte, for a binding partner immobilized
on a solid support. A greater concentration of analyte in the sample results in a lower
signal in the assay, as the labeled analytes are competed away from the binding partner
on the solid support (i.e., the signal produced during a competition assay decreases as
the concentration of analyte in the sample increases). Thus, the sandwich assay
provides a qualitative assessment with great sensitivity, while the competition assay
provides a quantitative measure of analyte concentration.
Regardless of the analyte-detecting method used, the rapid assay devices currently
available are often categorized into one of three basic formats: the "dipstick" format,
the "flow through" format, and the "lateral flow" format. The "dipstick" format typically
consists of a strip of porous material having a sample receiving end, a reagent zone and
a reaction zone. The sample is wicked along the assay device starting at the samplereceiving
end and moving into the reagent zone. The analyte to be detected binds to a
reagent incorporated into the reagent zone, preferably a labeled binding partner, to
form a complex. Typically, these binding pairs are antibody:antigen complexes, or a
receptor:ligand complexes having a label such as a colloidal metal incorporated into the
reagent portion of the complex. The labeled binding partner-antigen complex then
migrates into the reaction zone, where the complex is captured by another specific
binding partner firmly immobilized in the reaction zone. Retention of the labeled
complex within the reaction zone thus results in a visible readout.
The "flow through" format also utilizes porous solid phase materials. This assay format
usually has a porous membrane that contains an immobilized binding partner
positioned above an absorptive layer. Once the sample has been added to the
membrane surface, the analyte of interest reacts with the immobilized binding partner
to form an analyte-binding partner complex. The complex is visualized by addition of a
second binding partner having a label, such as an enzyme, dye particles or colloidal
metals. The absorptive layer acts as a sink for excess assay reagents, and can be used to
regulate the flow rate of the reactants to achieve optimal reaction between the analyte
and the binding partner. In this format, the sensitivity of the readout can be improved
by "washing" the membrane with additional solution to reduce any nonspecific binding
of the label, or remove any other materials which can interfere with the assay readout.
The dipstick format, which was originally designed for urine analysis, uses a relatively
large volume of sample for analysis. This is a considerable limitation to use of such a
device for analysis of serum or blood samples. In contrast, assay devices based on the
flow-through format reduce the volume requirement of samples significantly. However,
the flow-through format cannot be employed in a truly self-contained device. In devices
based on the flow-through format, the detecting reagent (i.e. the labeled binding
partner) is not directly incorporated into the porous solid matrix of device and thus
must be provided separately. This leads to additional limitations regarding reagent
stability, if the detecting reagents are provided in liquid form, or issues surrounding the
proper preparation and handling of the detecting reagent, if provided in a dried form.
The lateral flow format overcomes both the sample volume problem of the dipstick
format, as well as the detecting reagent issue of the flow-through format. However, the
lateral-flow format does not allow for a washing step, as inherent in the flow-through
format. Any interfering species, such as particulate or coloured material introduced by
the sample solution, or unbound label, can potentially interfere with the readout of the
assay device. As a result, the lateral flow format often employs filtration (e.g., using
specialized filters) during the assay procedure, e.g., using specially coated filters to
remove potential interfering species prior to detection of the analyte.
The prior art provides assay devices, test kits, and methods for detecting the presence
of one or more analytes in a sample. By controlling the release of the different reagents
used in the assay device, the sensitivity of the assay is improved as compared to
conventional assays, without compromising the specificity of the assay. Improved
sensitivity without loss of specificity is a highly desirable improvement in the field of
rapid chromatographic detection.
Currently available kitslassay devices are expensive and hence out of reach of common
people to substantial extent. The cost of manufacturing such assay devices is high due to
high cost of raw material, which is mainly a chromatographic film. Hence there is a need
for providing an assay device which is low cost and in which the result visibility is high.
OBJECT OF THE INVENTION
Accordingly, the main object of the present invention is to provide a low cost, visible
coloured indicator based assay device.
Yet another object of the invention is to provide an assay device with improved result
visibility.
Yet another object of the invention is to provide an assay device which requires lesser
amount of sample.
Still another object of the invention is to provide an assay device having plan convex
lens for better result clarity.
SUMMARY OF THE INVENTION
Accordingly, the present invention relates to an assay device with improved result
visibility. More particularly, the invention relates to a low cost, visible coloured indicator
based assay device with improved result visibility. The said assay device provides for
detecting the presence of one or more analytes in a given sample.
The present invention provides a novel approach to catching the result with vision
quality by the help of attached lens on result window. The present invention presents
assay devices that are particularly suitable for rapid chromatographic assays using a
controlled series of reactions. The assay devices use a small volume of sample and
achieve a much higher titration-end-point activity than conventional lateral flow assays.
In addition, the assay devices of the present invention provide better assay sensitivity,
without compromising specificity.
5 In addition, the results can be viewed more clear when the plan convex lens is placed on
the result window. The lens clarifies the results without the need for specialized
equipment.
DESCRIPTION OF DRAWINGS
FIG. 1A depicts a schematic of a general view of an assay device of the present
10 invention
FIG. 18 depicts a schematic of a top view of an assay device of the present invention.
FIG. 2A depicts a perspective view of a lens
FIG. 28 depicts a front view of a lens
FIG. 3A depicts a front view of a schematic of an alternative embodiment of the lower
15 casing of the assay device of the present invention.
FIG. 38 depicts a top view showing a schematic arrangement of lower casing.
FIG. 4A depicts a front view of upper casing the present invention.
FIG. 4B depicts a bottom view showing a schematic arrangement of upper casing.
FIG. 4C depicts a top view showing a schematic arrangement of upper casing.
20 FIG. 4D depicts a perspective view showing a schematic arrangement of upper casing.
FIG. 5 is a schematic showing details of assembly of present invention.
DETAILED DESCRIPTION OF THE INVENTION
The proposed invention relates to an assay device with improved result visibility. More
particularly, the invention relates to a low cost, visible coloured indicator based assay
device with improved result visibility. The said assay device provides for detecting the
presence of one or more analytes in a given sample.
The present invention provides a novel approach to catching the result with vision
quality by the help of attached lens on result window. The present invention presents
assay devices that are particularly suitable for rapid chromatographic assays using a
controlled series of reactions. The assay devices use a small volume of sample and
achieve a much higher titration-end-point activity than conventional lateral flow assays.
In addition, the assay devices of the present invention provide better assay sensitivity,
without compromising specificity.
DEFINITIONS
It is to be understood that the present invention is not limited to a particular
composition or biological system, which can, of course, vary. It is also to be understood
that the terminology used herein is for the purpose of describing particular
embodiments only and is not intended to be limiting in any manner. As used in this
specification and the appended claims, the singular forms "a", "an" and "the" include
plural referents unless the content clearly dictates otherwise. Thus, for example,
reference to "a releasable binding partner" includes a combination of two or more such
binding partners, reference to "an analyte" includes mixtures of analytes, and the like.
Unless defined otherwise, all technical and scientific terms used herein have the same
meaning as commonly understood by those having ordinary skill in the art to which the
invention pertains. Although any methods and materials similar or equivalent to those
described herein can be used in the practice for testing of the present invention, the
preferred materials and methods are described herein.
While describing the present invention, the following terminology will be used in
accordance with the definitions set out below.
5 "Assay device" means a multi-component chromatographic apparatus used for the
detection and/or measurement of one or more analytes of interest.
"Chromatographic element" refers to a solid matrix upon which the sample can be
applied and allowed to migrate during the assay procedure.
"Sample receiving end" refers to the portion of the chromatographic element at which
10 the sample is administered during the assay.
"Reagent releasing end" refers to the portion of the chromatographic element distal to
the sample receiving end, and at which one or more releasable assay reagents are
incorporated.
"Reaction zone" refers to the region of the chromatographic element between the
15 sample receiving end and the reagent releasing end, within which one or more binding
partners specific to the analyte (or to a complex containing the analyte) have been
immobilized.
"Absorbent pad" refers to an absorbent or bibulous material usually positioned at the
base of the assay device.
20 "Separator" refers to a barrier structure positioned between the chromatographic
element and the absorbent pad.
"Casing" or "Housing" as used herein refers to an optional component of the assay
device, which surrounds at least a portion of the chromatographic element, absorbent
pad and separator and provides some structural support.
"Sample" refers to any desired material for sampling, usually of biological origin.
"Analyte" refers to a compound or composition to be detected or measured in a
sample.
"Binding partner" is used herein to describe a member of a binding pair which interact
either chemically or physically to form a complex. An "immobilized" binding partner
refers to a binding partner that is adsorbed, embedded or affixed, either permanently or
semi-permanently, to a solid substrate or matrix (for example, the reaction zone of the
chromatographic element.) A "releasable" binding partner refers to a molecule which is
not permanently immobilized or affixed to a solid substrate or matrix, and is capable of
migration or movement for example, by diffusion.
"Label" as used herein refers to any substance that is capable of producing a detectable
signal. Various labels suitable for use in the present invention include, but are not
limited to, chromatogens, fluorescent or chemiluminescent compounds, catalysts,
enzymes, enzymatic substrates, dyes, colloidal metallic and non metallic particles, and
organic polymer latex particles. Particularly preferred for use in the present invention
are the visually-detectable colored particles, such as colloidal metals and non metals,
and dye particles.
"Bibulous" refers to materials that are absorbent.
DETAILED DESCRIPTION OF DRAWINGS
FIG. 1A represents a simple illustrative embodiment of the assay device of the present
invention. Assay device 2 is composed of chromatographic element 4, absorbent pad 6
and separator 8. Chromatographic element 4 includes three generally contiguous
sections: sample receiving end 10, reagent releasing end 12, and reaction zone 14
positioned between sample receiving end 10 and reagent releasing end 12. The device is
constructed such that separator 8 is positioned between chromatographic element 4
and absorbent pad 6, and can be removed to allow contact between sample receiving
end 10 and absorbent pad 6 during operation of the device. Separator 8 can range in
size from extending the entire length of chromatographic element 4, to cover only
sample receiving end 10 of chromatographic element 4. In addition, a portion of
separator 8 may extend beyond chromatographic element 4, at either sample receiving
end 10 (as shown) or alternatively at reagent releasing end 12 of chromatographic
element 4.
Chromatographic element 4 can be a nitrocellulose membrane, a porous matrix, a filter,
or other like material. Assay reagents are incorporated into specific portions of
chromatographic element 4. Sample receiving end 10 and/or reagent releasing end 12
of chromatographic element 4 further comprise a layer of absorbent material, such as
filter paper or a porous matrix, wherein additional assay reagents are incorporated.
Absorbent pad 6 is prepared from any absorbent or bibulous materials (for example,
filter paper) that will sufficiently draw and hold aqueous liquid when the assay device is
in operation.
In an embodiment, separator 8 is formed from an impermeable material, such as a thin
piece of plastic, polyester, polycarbonate, or the like. In an alternative embodiment,
separator 8 can be prepared from a material which will allow passage of an aqueous
solution after a certain period of time, such as a semi-permeable membrane or a
material which will dissolve upon exposure to liquid.
FIG. 1B is a view of the upper face of one embodiment of the assay device according to
the present invention. The assay device is enclosed in casing, formed of plastic,
cardboard, treated paper, or other similar materials. Preferably, casing has several
windows, or openings, 20 and 30, which are situated over the sample receiving end 10,
the reagent releasing end 12, and the reaction zone 14 of the chromatographic element,
respectively.
5 In FIG. 5, visible indicator 22 (for example, a colour line) is marked on the reaction zone
and can be seen through window 20. Alternatively, visible indicator 22 can be a marking
on casing, at the side of window 20. In this embodiment of the device of the present
invention, portion of the separator protrudes from casing to facilitate the removal of the
separator during operation of the assay device. Alternatively, a different portion of
10 separator 8 may protrude from the opposite end of casing, proximal to reagent
releasing end 12, to permit partial removal of separator 8 from assay device 2, thus
allowing absorbent pad 6 and sample receiving end 10 to come into contact.
The casing consists of top portion and bottom portion. Top portion contains openings
15 20,30, whereas bottom portion has support 24 which compensates for the difference in
thickness between the two ends of the assembly. The design of casing generally ensures
that various parts of the assay device are assembled firmly together within the casing.
Enclosed in casing are three major components of the assay device: chromatographic
element, which is positioned above separator 8, which in turn is positioned above
20 absorbent pad 6. Chromatographic element consists of sample receiving end 10, reagent
releasing end 12, and reaction zone 14. Optionally, chromatographic element can be
attached to a backing layer. In this embodiment of the present invention, optional filter
is attached to and constitutes part of sample receiving end 10 of chromatographic
element, while optional reagent-bearing pad impregnated with releasable reagents is
25 attached to and thus constitutes part of reagent releasing end 12. Reaction zone 14
contains colour indicator 22 as well as immobilized binding partner. Optionally, reaction
zone 14 also contains known antibodies or known antigens (for example, Protein A) for
use as control(s).
A sample is applied to opening 30 that is positioned over sample receiving end 10 of
chromatographic element. The sample is allowed to migrate laterally via capillary action
towards reagent-receiving end 10 of chromatographic element. Separator 8 prevents
the sample from flowing through chromatographic element and into underlying
absorbent pad 6. While the sample passes across reaction zone 14, the analyte (if
present in the sample) will be able to bind to its specific binding partner immobilized
within reaction zone 14. Once the sample has covered reaction zone 14 (as indicated by
the wetting front reaching colour indicator 22), an aqueous solution is added to opening
20 situated over reagent releasing end 12 of chromatographic element. Separator 8 is
removed by pulling protruding end, allowing sample receiving end 10 of
chromatographic element and absorbent pad 6 to come into direct contact and reverse
the direction of the liquid flow. The aqueous solution releases the assay reagents
incorporated within reagent releasing end 12. The aqueous solution can be added prior
to the removal of separator 8, concurrently with the removal, or immediately
afterwards.
A reagent such as a second specific binding partner labelled with a detectable label such
as a naturally coloured particle then migrates into reaction zone 14 and reacts with the
analyte-binding partner complex, enabling detection of the analyte. In addition, known
antibodies or known antigens can be included in the chromatographic element as
control(s).
FIG. 2A depicts a perspective view of a Plano convex lens, the lens 16 is placed on
window 20 of the casing, due to pacing of lens the vision clarity is become good, and
easy to identify the result from the assay device. The lens 16 covers fully the window 20.
FIG. 28 depicts front view of a lens.
FIG. 3A depicts front view of a schematic of an alternative embodiment of the lower
casing of the assay device of the present invention.
FIG. 3B depicts top view of a schematic of an alternative embodiment of the lower
casing of the assay device of the present invention. The support 24 makes interference
between upper casing and the lower casing, the indicating paper 28 rests on the resting
bed 34.
FIG. 4A depicts front view of upper casing the present invention, the opening 30 is for
putting the droplet of the sample. For vision clarity the Plano convex lens 16 is placed on
the opening 20 through which the visible indicator can be seen more clearly.
FIG. 4B depicts a bottom view showing a schematic arrangement of upper casing. The
supports 26 makes interference between casings and supports indicating paper 28, the
supporting bar 32 is mounted on the bottom surface of casing it supports the paper 28,
so that it can't move and bulging will not occur, as near to window 20 another support
18 is provided for the same.
FIG. 4C depicts a top view showing a schematic arrangement of upper casing, opening
30 is for putting the sample and opening 20 is for getting the result from the sample.
FIG. 4D depicts a perspective view showing a schematic arrangement of upper
casing. The Plano convex lens 16 is placed on the window 20 for vision clarity of result.
FIG. 5 is a schematic showing details of assembly of present invention. The opening 20
show the result by the help of visible indicator 22 through the lens 16.
As shown in FIGS. 3 and 4, such a construct allows a single device using a generic
detector such as a labelled specific binding partner for detection of different types of
antibodies to the same pathogen.
An additional advantage of the assay device of the present invention is the ease of
manufacture of the assay device. The devices of the present invention employ a generic
construct, which can be modified with minimal alteration from one application to
another. The proposed invention is aimed at altering the width of holding point of the
casings so that the overall production cost is minimized. The present invention therefore
reduces both the time and the cost used for product development. Furthermore, since
the major components of the assay device can be used across a variety of assays,
production parameters can be maintained without changes. A production facility
manufacturing a series of products based on the present invention would use a single
set of manufacturing equipment and a minimal array of inventories of raw materials,
which in turn significantly reduces the costs of operation and production.

15
CLAIMS
I Claim:
1. An improved portable low cost assay device comprising of:
a. at least one chromatographic element (4);
b. at least one absorbent pad (6);
c. at least one separator (8);
d. a lower casing;
e. an upper casing having at least two openings (20) and (30); and
f. a plano convex lens (16) placed on the said opening (20);
wherein:
the said chromatographic element further comprises of at least one sample receiving
end (lo), at least one reagent releasing end (12) and at least one reaction zone (14)
positioned between the said sample receiving end and reagent releasing end;
the said separator (8) is positioned between the said chromatographic element (4) and
the said absorbent pad (6), and is removable to allow contact between said sample
receiving end (10) and said absorbent pad (6) during operation of the device; and
the width of the said device ranges from 1 to 3 millimeter.
2. The improved portable low cost assay device as claimed in claim 1, wherein the said
chromatographic element (4) is selected from the group of but not limiting to a
nitrocellulose membrane, a porous matrix, a filter, or other similar material known in
the art.
3. The improved portable low cost assay device as claimed in claim 1, wherein the said
sample receiving end (10) and/or reagent releasing end (12) of chromatographic
element (4) further comprise a layer of absorbent material, such as filter paper or a
porous matrix, wherein additional assay reagents are incorporated.
4. The improved portable low cost assay device as claimed in claim 1, wherein the said
separator (8) is formed from an impermeable material, like a thin piece of plastic,
polyester, polycarbonate, or any similar material known in the art.
5. The improved portable low cost assay device as claimed in claim 1, wherein the said
separator (8) either extends the entire length of chromatographic element (4), to cover
only sample receiving end (10) of chromatographic element (4) wherein a portion of
separator (8) extends beyond chromatographic element (4), at either sample receiving
end (10) or alternatively at reagent releasing end (12) of chromatographic element (4).
6. The improved portable low cost assay device as claimed in claim 1, wherein a visible
indicator (22) is marked on the on the reaction zone visible through the said opening
(20).
7. The improved portable low cost assay device as claimed in claim 1, wherein the said
reaction zone (14) contains immobilized binding partner.
8. The improved portable low cost assay device as claimed in claim 1, wherein the said
reaction zone (14) also contains known antibodies or known antigens as control.
9. The improved portable low cost assay device as claimed in claim 1, wherein the said lens
(16) completely covers the opening (20).
Dated this 24th day of July 2013
LALIT AM BASTHA
AGENT FOR THE APPLICANT
IN/PA-1319