U.S. patent application number 15/868225 was filed with the patent office on 2019-01-17 for disposable test sensor.
The applicant listed for this patent is Changsha Sinocare Inc.. Invention is credited to Xiaohua Cai, Hongli Che, Shaobo Li.
Application Number | 20190017956 15/868225 |
Document ID | / |
Family ID | 53521155 |
Filed Date | 2019-01-17 |
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United States Patent
Application |
20190017956 |
Kind Code |
A1 |
Cai; Xiaohua ; et
al. |
January 17, 2019 |
DISPOSABLE TEST SENSOR
Abstract
The present invention relates to disposable test sensors having
improved sample application and measuring properties and their uses
for detection, preferably, quantitative measurement, of analyte in
a liquid sample like blood. In particular, the invention provides
for an electrochemical biosensor which has a thin-layer fluid
chamber having funnel-like shape with a novel extra wide opening as
sampling entrance and a vent opening at the tip of the chamber for
air escape. The thin-layer fluid chamber provides a reservoir from
which a sample fluid can be drawn into it through capillary action.
The extra wide sampling entrance provided by the present invention
can draw blood into the chamber through any part of the opening,
thus it allows easy targeting the samples with small volume,
picking up smeared samples and it is more tolerant to users who jam
the tip of the sensor into users' finger.
Inventors: |
Cai; Xiaohua; (Changsha,
CN) ; Che; Hongli; (Changsha, CN) ; Li;
Shaobo; (Changsha, CN) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
Changsha Sinocare Inc. |
Changsha |
|
CN |
|
|
Family ID: |
53521155 |
Appl. No.: |
15/868225 |
Filed: |
January 11, 2018 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
14153654 |
Jan 13, 2014 |
9897566 |
|
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15868225 |
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Current U.S.
Class: |
1/1 |
Current CPC
Class: |
G01N 27/3272
20130101 |
International
Class: |
G01N 27/327 20060101
G01N027/327 |
Claims
1. An electrochemical test sensor comprising: a base layer having a
sampling end and an electric contact end; a middle layer formed of
an electrically insulating material having a width approximately
equal to a width of the base layer, and having a sampling end and
an electric contact end, the middle layer forming a cutout region;
an upper layer having a sampling end and an electric contact end;
and a fluid chamber formed by the middle layer defining the cutout
region, wherein the cutout region extends from the sampling end
towards the electric contact end away from the sampling end;
wherein the sampling end of the middle layer is slightly recessed
from a front edge of the upper layer sampling end and a front edge
of the base layer sampling end, wherein the upper layer, middle
layer, and base layer define two side openings in communication
with the fluid chamber, a first side opening being on a first side
of the sensor at the sampling end, a second side opening being on a
second opposite side of the sensor at the sampling end, the two
side openings being defined by the middle layer sampling end being
slightly recessed from the front edge of the upper layer and base
layer sampling ends; the fluid chamber having a continuous sampling
entrance defined by an open front opposite to the recessed edge of
the middle layer and the two side openings; wherein a combined
length of the open front and the two side openings of the fluid
chamber is less than a perimeter length of the middle layer cutout
region.
2. The electrochemical test sensor of claim 1 wherein the cutout
region is formed with a curving inward shape, forming a concave
face.
3. The electrochemical test sensor of claim 2 wherein the curving
inward shape is an arc.
4. The electrochemical test sensor of claim 1 wherein the upper
layer defines a vent opening through its thickness, the vent
positioned over a portion of the fluid chamber, the vent allowing
gas to escape from the fluid chamber.
5. The electrochemical test sensor of claim 1 wherein the middle
layer is formed of a two-sided adhesive tape.
6. The electrochemical test sensor of claim 1 wherein the upper
layer further comprises a hydrophilic material on a surface facing
the fluid chamber.
7. The electrochemical test sensor of claim 1 wherein the base
layer further comprises electrodes, and a chemistry within the
electrodes configured to cause an electrochemical signal once
exposed to the fluid within the fluid chamber.
8. The electrochemical test sensor of claim 1 wherein the two side
openings are configured to allow a fluid to enter the fluid chamber
through one of the two side openings when the first or second side
is parallel to a surface that the fluid is on.
9. The electrochemical test sensor of claim 1 wherein the cutout
region is funnel shaped, having inwardly tapering sides.
10. The electrochemical test sensor of claim 1 wherein the middle
layer is attached to the base layer.
11. The electrochemical test sensor of claim 1 wherein the upper
layer is attached to the middle layer.
12. The electrochemical test sensor of claim 1 comprising the three
layers, having the base layer directly attached to the middle
layer, and the middle layer directly attached to the upper
layer.
13. The electrochemical test sensor of claim 1 wherein the cutout
region is defined by at least a portion of a front edge of the
middle layer being recessed from the middle layer sampling end
along the width of the middle layer.
14. The electrochemical test sensor of claim 1 wherein the fluid
chamber is defined on a top by the upper layer, and on a bottom by
the base layer.
15. An electrochemical test sensor comprising: an electric contact
end having electric contacts; a sampling end opposite to the
electric contact end comprising electrodes and a fluid chamber in
communication with the electrodes; a continuous sampling entrance
to the fluid chamber comprising an open front at the sampling end,
and two side openings at opposite front sides of the
electrochemical test sensor at the sampling end, wherein a combined
length of the open front and the two side openings is less than a
perimeter length of the middle layer cutout region.
16. The electrochemical test sensor of claim 15 wherein the fluid
chamber extends away from the sampling end toward the electric
contact end.
17. The electrochemical test sensor of claim 1 wherein the fluid
chamber is funnel shaped, having inwardly tapering sides.
18. The electrochemical test sensor of claim 15 further comprising
a vent opening, the vent positioned over a portion of the fluid
chamber, the vent allowing gas to escape from the fluid
chamber.
19. The electrochemical test sensor of claim 15 wherein the test
sensor is formed of a base layer, a middle layer, and a top
layer.
20. The electrochemical test sensor of claim 19 wherein the fluid
chamber is formed by a cutout region of the middle layer, and
wherein the two side openings are formed by a front end of the
middle layer being recessed from a front end of the base layer and
a front end of the top layer.
Description
FIELD OF THE INVENTION
[0001] The present invention generally relates to a test sensor or
strip. More specifically, the present invention generally relates
to a disposable biosensor with a thin-layer fluid chamber that is
adapted to receive a fluid sample around with small volume. Still
more specifically, the present invention generally relates an
electrochemical biosensor with an extra wide sampling entrance.
Still more specifically, the present invention relates methods of
making and using the biosensors.
BACKGROUND OF THE INVENTION
[0002] The use of disposable test sensors such as strips in the
medical field for testing various analytes in body fluid is well
known. The accurate determination of analytes in body fluids is of
great importance in the diagnoses of certain physiological
abnormalities. In particular, it is important that diabetic
individuals frequently check their glucose level in their body
fluids to regulate the glucose intake in their daily diets. The
results of such tests can be used to determine the insulin dosage
or other medication needs to be administered. In one type of
blood-glucose testing system, test sensors, or called glucose
strips, are used by diabetic individuals to test a sample of blood
in connection with a hand-held meter. The glucose strips are used
by millions of diabetics throughout the world on a daily base.
[0003] There are hundreds of brand names of glucose strips in the
market. They are very similar in terms of sensor construction:
i.e., a channel is formed between a generally U-shaped spacer and
is adapted to receive blood from the opening end of the sensor
through capillary action and escape air from the other end through
an air escape vent. In order to reduce blood volume, thus reduce
pain from piercing finger or other sampling points, the blood
receiving chamber is usually small and, as a result, the sampling
entrance is also relatively small. As the volume of fluid chambers
in the sensors decreases, it becomes increasingly more difficult to
fill the fluid chamber with the sample to be analyzed. It has been
observed that users may abuse the test sensor by jamming the tip of
the test sensor into the individual's finger, which very probably
results in incomplete blood filling, non-continuous filling or
wiggling of blood flow. Additionally, in some existing test
sensors, it is difficult to position the fluid sample within the
channel entrance opening especially for those diabetics who have
poor vision and/or trembling hand. Besides, blood samples turn to
smear around the tip of fingers or other sampling points. It
becomes very difficult to draw such smeared blood into the sensor
chamber. All of these phenomena may eventually lead to biased
readings, and as a result, wrong dosage of insulin administration
and even life threatening errors may occur.
[0004] Therefore, in order to reduce or eliminate such biased
readings caused by such user action and/or reduce the difficulty in
connection with sampling, it would be highly desirable to have a
more user friendly test sensor that could easily target sample,
easily draw sample into the sensor chamber, and alleviate
incomplete filling, non-continuous filling and other issues that
may result in inaccurate test results. The present disclosure is
directed to a novel design and method to overcome one or more of
the limitations in the prior arts.
SUMMARY OF THE INVENTION
[0005] According to the first embodiment, a disposable
electrochemical test sensor has a funnel-like chamber having a
novel extra wide sampling entrance and a vent opening at the tip of
the chamber for air escape. Such a design is adapted to improve
sampling of fluid samples. The fluid chamber provides a thin-layer
reservoir from which sample fluid can be drawn into the funnel-like
chamber through capillary action. The extra wide sampling entrance
provided by the present invention can draw blood into the chamber
through any part of the opening end. Thus it allows easily
targeting the samples with small volume, picking up smeared samples
and alleviating jamming the opening end. In preferred embodiments,
the sensor consists of multiple layers which include a base layer
having conductive coatings serving as working and reference
electrodes; a middle layer having funnel-like shape serving as
spacer; and an upper layer with a hydrophilic surface facing to the
chamber. The upper, middle and base layers are laminated through
adhesives or other ways to bond each other, such that the
thin-layer fluid chamber is formed between a portion of the lower
layer surface and the upper layer surface at one end of the sensor,
while the other end of the sensor having conductive layer exposed
serve as electric contacts in connection with a monitor or
meter.
[0006] According to the second embodiment, a disposable
electrochemical test sensor has a funnel-like chamber having a
novel extra wide sampling entrance and a vent opening at the tip of
the chamber for air escape. Such a design is adapted to improve
sampling of fluid samples. The fluid chamber provides a thin-layer
reservoir from which sample fluid can be drawn into the sample
receiving chamber through capillary action. The extra wide sampling
entrance provided by the present invention can not only draw blood
into the fluid chamber through any part of the front opening end,
but can also draw blood into the fluid chamber through part of left
side and part of right side near the opening end. The front opening
and both side openings form a large opening, serving as blood
sample entrance. Thus such unique design allows easily targeting
the samples with small volume, picking up smeared samples and
alleviating jamming of the opening by users' finger. In preferred
embodiments, the test sensor consists of multiple layers which
include a base layer having conductive coatings serving as working
and reference electrodes; a middle layer having funnel-like shape
serving as spacer; and an upper layer with a hydrophilic surface
facing to the chamber. The upper, middle and base layers are
laminated through adhesives or other ways to bond each other, such
that the thin-layer fluid chamber is formed between a portion of
the lower layer surface and the upper layer surface at one end of
the sensor, while the other end of the sensor having conductive
layers exposed serve as electric contacts in connection with a
monitor or meter.
[0007] According to one method, an analyte concentration is
measured. A disposable electrochemical test sensor is provided
having a funnel-like chamber having a novel extra wide sampling
entrance and a vent opening at the tip of the chamber for air
escape. The chamber provides a thin-layer reservoir from which
sample fluid can be drawn into the thin-layer chamber through
capillary action. In preferred embodiments, the sensor consists of
multiple layers which include a base layer having conductive
coatings serving as working and reference electrodes; a middle
layer serves as spacer which may have different shapes, such as
circular arc, inverted triangle, inverted trapezoid, funnel-like
tapering shape etc.; and an upper layer with a hydrophilic surface
facing to the chamber. In preferred embodiments, the middle layer
is in funnel-like shape, such that an extra wide sampling entrance
is formed. The middle layer also defines the electrode areas once
laminated onto the base layer with conductive coating at the
surface. The upper, middle and base layers are attached through
adhesives or other ways to bond each other, such that the
thin-layer fluid chamber is formed between a portion of the lower
layer surface and the upper layer surface at one end of the sensor,
while the other end of the sensor having conductive layers exposed
serve as electric contacts in connection with a monitor or
meter.
BRIEF DESCRIPTION OF THE DRAWINGS
[0008] FIGS. 1A and 1B are perspective views of the test sensor of
the present invention according to the first (1A) and second (1B)
embodiment.
[0009] FIG. 2 is an exploded view of the test sensor of the present
invention showing the three component layers.
[0010] FIGS. 3A and 3B are top views of the test sensor of the
present invention consisting of three laminated layers according to
the first (3A) and second (3B) embodiment.
[0011] FIG. 4 is a top view of the base layer to be used in forming
a test sensor according to one embodiment.
[0012] FIGS. 5A and 5B are top views of the middle layer to be used
in forming a test sensor according to the first (5A) and second
(5B) embodiment.
[0013] FIGS. 6A and 6B are top views of the upper layer to be used
in forming a test sensor according to the first (6A) and second
(6B) embodiment.
[0014] FIG. 7 is a side view of the test sensor according to the
first embodiment of the present invention.
[0015] FIG. 8 is a side view of the test sensor according to the
second embodiment of the present invention.
DETAILED DESCRIPTION OF ILLUSTRATED EMBODIMENTS
[0016] The test sensor of the present invention is directed to
improve sampling entrance of the strip for the determination of an
analyte concentration of in a fluid sample, such as blood. In one
embodiment, a test sensor is adapted to receive a fluid sample from
one end of the sensor, while the other end is connected with an
instrument or meter. Analytes that may be measured include, but not
limited to glucose, lactate, uric acid, creatinine, creatine,
cholesterol, triglycerides, hemoglobin, bilirubin, alcohol, etc.
The fluid sample may be any body fluid, thus, the analytes may be
in, for example, a whole blood sample, a blood serum sample, a
blood plasma sample, other body fluids like tears, interstitial
fluid and urine. In one preferred method, the testing equipment is
a hand-held meter.
[0017] In one embodiment, the test sensor is an electrochemical
test sensor. FIGS. 1A and 1B show perspective views of the test
sensor of the present invention. The sensor has a sensor body 100,
an electric contact end 10 and sampling end 20. The electric
contact end may have at least two contacts used for one working
electrode and one reference electrode, respectively. The sensor has
a thin-layer fluid chamber 30a and a thin-layer fluid chamber 30b,
according to the first embodiment and second embodiment,
respectively. The thin-layer fluid chambers have funnel-like shape
with wide opening as the entrance for fluid sample. Once the fluid
sample enters the chamber, the analyte will react with the chemical
reagents loaded on the surface of the electrodes, thus resulting in
electrochemical signals, which correlate to the concentration of
the analytes. Note that the sensor has a vent opening 50a and 50b
at the tip of the funnel-like chamber, according to the first
embodiment and second embodiment, respectively. The vent openings
allow air to escape when the fluid sample enters the chamber.
[0018] FIG. 2 is an exploded view of the test sensor of the present
invention showing the three component layers. In one preferred
embodiment, the electric contact end 10 has three electric contacts
at the electric contact end, serving as contacts for a first
working electrode 11; a second working electrode 13 and a reference
electrode 12, respectively. The electric contacts 11, 12, 13 are
related to corresponding electrodes at the sampling end 20. In one
embodiment, the test sensor consists of multiple layers which
include a base layer 200; a middle layer 300; and an upper layer
400, as shown in FIG. 2.
[0019] FIGS. 3A and 3B are top views of the test sensor of the
present invention consisting of three laminated layers according to
the first (3A) and second (3B) embodiment. At the sampling end 20,
there are three electrodes, corresponding to the first working
electrode 31, second working electrode 33 and reference electrode
32. At electric contact end 10, there are three electric contacts
11, 12 and 13, connecting to the first working electrode 31;
reference electrode 32; second working electrode 33; respectively.
Note that the arrangement or order of the electrodes is not crucial
for the essence of test sensor of the present invention. 91 in FIG.
3B denotes the side opening of the sampling entrance of the
biosensor according to the second embodiment in the present
invention, which will be discussed in the following sections. As
can be seen in FIG. 3B, in this embodiment, the opening has a
combined length equal to the open front length L2 (which is the
same as the width of the test sensor) and the two side opening
lengths L1, L3. A perimeter length L4 (which is the bold broken
line) of the middle layer cutout region 41b, which in turn defines
a perimeter of the fluid chamber, is defined as a length of the
perimeter edge defined by the cutout from one widthwise end of the
middle layer to the other widthwise end. In the embodiment shown,
the perimeter length L4 is the length of the funnel shaped cutout
41b. The combined length of the opening (L1+L2+L3) is less than the
perimeter length L4 of the middle layer cutout region 41b.
[0020] FIG. 4 shows a top view of a first base layer 200 to be used
in forming a test sensor according to one embodiment. The base
layer 200 may be made from a variety of materials such as polymeric
materials, coated with conductive materials such as carbon, various
metals or metal oxides. The base layer 200 with conductive coating
serves as substrate of the test sensor and chamber forming layer.
It also serves as electrodes at one end 20 and electric contacts at
the other end 10. Non-limiting examples of polymeric materials,
that may be used to form the base layer include, but not limited to
polyethylene, polypropylene, polystyrene, polyvinyl chloride, and
polytetrafluoroethylene, polycarbonate, polyethylene terephthalate,
polyethylene naphthalate, polyimide and combinations thereof. The
conductive coating may be formed by a variety of methods which are
well known in the field including, but not limited to printing
(e.g., screen-printing), coating (e.g., reverse roll), vapor
deposition, sputtering, chemical deposition, and electrochemical
deposition. The conductive coating may be on a whole piece of
insulating material. If so, a desired number of electric conduits
must be made. This can be achieved by etching/scribing the required
number of conductive conduits. The etching process may be
accomplished chemically, by mechanically scribing lines in the
conductive layer, or by using a laser to scribe the conductive
layer into separate conductive conduits. The conductive materials
may be, but not limited to various carbon materials; various noble
metals like gold, platinum, palladium, iridium, rhodium, ruthenium;
various metal oxides like indium oxide, tin oxide; and combinations
thereof.
[0021] FIG. 5A shows a top view of the middle layer 300a to be used
in forming a test sensor according to the first embodiment. The
middle layer 300a virtually has same width as the base layer 200,
but shorter in length to leave part of the base layer 300a exposed
for electric contacts. The middle layer 300a serves as a spacer in
between the base layer 200 and the upper layer 400. The middle
layer 300a, or spacer, is also made of a plastic insulating
material with glue or adhesive on both sides and creates the
thin-layer fluid chamber 30a of the laminated body (FIG. 1A). It
contains a funnel-like cutout 41a at the end 20 which overlays the
base layer 200 with the open end corresponding to the open end of
the laminated body described earlier. The funnel-like cutout 41a
has a wide opening with a width of at least 1 mm. The width can be
equal or slightly smaller than the width of the base layer 200.
More preferably, it is around 2 mm to 20 mm in the present
invention. Assuming the test sensor or the component layers (200,
300a and 400) in the present invention have a width of around 6 mm,
preferably, the width may be around 5.2 mm. Thus, a blood sample
can enter the thin-layer fluid chamber 30a from any part of the
entire opening end. A double coated, pressure-sensitive adhesive
tape may be used as the middle layer 300a. The cutout 41a creating
the thin-layer fluid chamber may have different shapes, including,
but not limited to semi-circular, inverted triangle, inverted
trapezoid, funnel-like shape and etc. In one preferred embodiment,
the cutout is in funnel-like shape. The funnel-like cutout 41a
forms a large opening as sampling entrance and also defines
electrode areas once laminated onto the base layer 200 with
conductive coating at the surface. The thickness and size of the
cutout 41a determine the volume of the thin-layer fluid chamber
30a. Preferably, the middle layer 300a has a thickness ranging from
0.01 mm to 0.5 mm. More preferably, the middle layer 300a has a
thickness around 0.08 mm in the present invention.
[0022] FIG. 5B shows a top view of the middle layer 300b to be used
in forming a test sensor according to the second embodiment. The
middle layer 300b is alternative to the middle layer 300a according
to the first embodiment. The middle layer 300b also serves as a
spacer in between the base layer 200 and the upper layer 400. The
middle layer 300b virtually has same width as the middle layer
300a, but it is slightly shorter in length at the end 20, as a
result, leaving openings at both corners after all three component
layers 200, 300b and 400 are laminated. Such a unique design of the
present invention forms an over 180.degree. sampling entrance, even
wider opening compared to the first embodiment described above.
Therefore, a blood sample not only enters the thin-layer fluid
chamber 30b from any part of the front opening, but also from both
side opening 91 of the test sensor at the end 20, as shown in FIG.
3B. The middle layer 300b, or spacer, is also made of a plastic
insulating material with glue or adhesive on both sides and creates
the sample fluid chamber of the laminated body. It contains a
funnel-like tapering cutout 41b on the end 20 which overlays the
base layer 200 with the open end corresponding to the open end of
the laminated body described earlier. The funnel-like cutout 41b
has a wide opening with a width of at least 1 mm. The width can be
equal to or slightly smaller than the width of the base layer 200.
More preferably, it is around 2 mm to 20 mm in the present
invention. Assuming the test sensor or the component layers (200,
300a and 400) in the present invention have a width of around 6 mm,
preferably, the width of funnel-like cutout 41b may be around 5.2
mm. A double coated, pressure-sensitive adhesive tape may be used
as the middle layer 300b. The cutout 41b creating the fluid chamber
may have different shapes, including, but not limited to
semi-circular, inverted triangle, inverted trapezoid, funnel-like
shape and etc. In one preferred embodiment, the cutout is in
funnel-like shape. The funnel-like cutout 41a forms a large opening
as sampling entrance and also defines electrode areas once
laminated onto the base layer 200 with conductive coating at the
surface. The thickness and size of the cutout 41b determine the
volume of the thin-layer fluid chamber 30b. Preferably, the middle
layer 300b has a thickness ranging from 0.01 mm to 0.5 mm. More
preferably, the middle layer 300b has a thickness around 0.08 mm in
the present invention.
[0023] The laminated body may also have an upper layer 400 with a
vent opening 50a and 50b, as shown in FIGS. 6a and 6b, bonded to
the middle layer 300a and 300b, according to the first and second
embodiment, respectively. It virtually has the same width as the
base layer 200 and middle layers 300a or 300b, and it has the same
length as the middle layer 300a. The upper layer 400 is made of a
plastic or polymer materials. Non-limiting examples of polymeric
materials, that may be used to form the upper layer 400, include,
but not limited to polyethylene, polyethylene terephthalate,
polyethylene naphthalate, polyimide and combinations thereof. In
one embodiment, the upper layer 400 has a hydrophilic surface
facing to the chamber to facilitate the capillary action. It should
be understood that the entire side of the upper layer 400 may be
coated with a hydrophilic substance and then bonded to the middle
layer 300a or 300b. In the present invention, the shape of the vent
opening 50a and 50b is not critical at the upper layer 400. In one
preferred embodiment, the shape of the vent opening is in round
shape.
[0024] FIG. 7 shows side view of the test sensor of the first
embodiment consisting of three laminated layers including a base
layer 200, middle layer 300a and upper layer 400.
[0025] FIG. 8 shows side view of the test sensor of the second
embodiment consisting of three laminated layers including a base
layer 200, middle layer 300b and upper layer 400. Note 91 denotes
the side opening described earlier. Its thickness is the same as
the middle layer 300b. The length of the side opening 91 is
preferably from 0.01 mm to 2.5 mm. More preferably, it is from 0.1
to 0.3 mm. Still more preferably, it is around 0.25 mm. It should
be emphasized that the side opening 91 in the unique design of the
present invention is just a part of the extra wide sampling
opening. The side and front opening combine to form an over
180.degree. sampling angle.
[0026] In operation, the fluid sample like blood can enter the
thin-layer fluid chamber through any point of the wide opening at
the front side of the test sensor according to the first embodiment
of the present invention. Thus such unique design allows easily
targeting the samples with small volume, picking up smeared samples
and alleviating jamming of the opening by users' finger.
[0027] The second embodiment in the present invention not only
possesses the advantage that the first embodiment does, but it has
additional advantage. In the second embodiment, the sampling
entrance includes front opening and two side opening 91. The front
opening and side opening combine forming a large extra wide
sampling entrance, which is over 180.degree.. Thus, blood sample
can enter the fluid chamber from any point of the over 180.degree.
opening. That is the blood sample can enter from the front opening
and can also enter from the side opening 91. Thus such unique
design allows even more easily targeting the samples with small
volume, picking up smeared samples and alleviating jamming of the
opening by users' finger.
[0028] By having a test sensor with the extra wide openings in the
first embodiment or second embodiment, being adapted to receive a
fluid sample, the test sensor of the present invention more easily
receives the fluid sample from a user and is more tolerant to users
who jam the tip of the sensor into his/her finger, is more tolerant
to fluid samples with very small volume (less than 1 microliter)
and even smeared samples on the finger tip.
[0029] Referring back to FIGS. 2 and 3, the electrode 31, 32, 33
may be loaded with chemistries that react with an analyte to
produce detectable electrochemical signals. The chemistries may
contain an enzyme, an antibody, an antigen, a complexing reagent, a
substrate or combination thereof. The reagents are selected to
react with the desired analyte or analytes to be tested so as to
assist in determining an analyte concentration of a fluid sample.
In one embodiment, the reagents typically contain an enzyme such
as, for example, glucose oxidase, glucose dehydrogenase,
cholesterol oxidase, creatinine amidinohydrolase, lactate oxidase,
peroxidase, uricase, xanthine oxidase and etc. which reacts with
the analyte and with an electron acceptor such as a ferricyanide
salt to produce an electrochemically measurable species that can be
detected by the electrodes. For example, if the analyte of the test
sensor is glucose, then glucose oxidase or glucose dehydrogenase
may be included as the enzyme; if the analyte of the test sensor is
uric acid, then uricase may be included as the enzyme. It should be
noted that in some cases more than one enzyme may be included to
construct the test sensor in order to generate detectable
electrochemical signal. For example, in order to make a test sensor
for cholesterol, cholesterol esterase, cholesterol oxidase and
peroxidase may be included in the sensor.
[0030] In order for the test sensor to work effectively, the
electrode 31, 32, 33 may comprise a mixture of a polymer, an
enzyme, a surfactant, an electron acceptor, an electron donor, a
buffer, a stabilizer and a binder. The electrode 31, 32, 33 may
further include a mediator that is an electron acceptor and assists
in generating a current that corresponds to the analyte
concentration. The preferable mediators could be redox chemicals
either in oxidized or reduced form. The mediator used in the
present invention may include, but not limited to various metal or
noble metal complexes such as potassium ferricyanide, potassium
ferrocyanide, cobalt phthalocyanine, various ferrocenes, and
various organic redox mediators such as methylene blue, methylene
green, 7,7,8,8-tetracyanoquinodimethane, tetrathiafulvalene,
toluidine blue, meldola blue, N-methylphenazine methosulfate,
phenyldiamines, 3,3',5,5'-tetramethylbenzidine, pyrogallol, and
benzoquinone, phenanthroline-5,6-dione and etc. For example, if the
enzyme used to construct the test sensor is glucose oxidase or
glucose dehydrogenase, then potassium ferricyanide may be included
as redox mediator; if the enzyme used to construct the test sensor
includes peroxidase, then potassium ferrocyanide may be included as
redox mediator.
[0031] The electrode 31, 32, 33 include a first working electrode
31, a second working electrode 33 and a reference electrode 32. In
one embodiment, the second working electrode 33 serves as a blank
electrode without loading a chemistry that reacts with the analyte,
such that background signal can be measured and be subtracted from
the analyte signal resulted from the first working electrode 31. In
this embodiment, effect of interference substances on the analyte
signal could be minimized. The background signal may be generated
from the matrix of the fluid sample. For example, if the test
sensor is used to measure glucose in a blood sample, the background
signals may be generated from ascorbic acid, acetaminophen, uric
acid, bilirubin and etc. in the blood sample. Still in, this
embodiment, the electric signals such as current, impedance at the
working electrodes 31 and 33, and time to obtain these signals
could be used to estimate filling status of the thin-layer fluid
chamber (filled or not). Thus, this embodiment could alert
under-fill of fluid samples.
[0032] In another embodiment of the present invention, the
laminated body of the test sensor has four layers (not shown).
Beside the three layers mentioned above, there is an additional
middle layer in between the base layer 200 and middle layer 300.
This additional middle layer, having at least two cutouts at the
sampling end 20, is laminated in between the base layer 200 and
middle layer 300. The cutouts at this additional layer not only
define the electrode areas and also hold chemical reagents. The
cutouts at this additional layer can be accomplished through many
methods skilled in the prior arts, such as mechanically drilling,
die-cut, laser firing, chemically etching and etc. The shape, size
as well as positioning is not critical, but they are within the
funnel-like thin-layer fluid chamber. The cutouts can have
different shapes, dimensions and/or arrangement orders, without
deviating from the scope and spirit of the present invention. The
placement of all of the cutouts is such that they will be all
positioned within the funnel-like thin-layer fluid chamber
described above. The cutouts may be made by die cutting the
insulating material mechanically, or cutting with a laser, and then
fastening the material to the base layer 200. An adhesive, such as
a pressure-sensitive adhesive, may be used to secure this
additional middle insulating layer to the base layer 200. Adhesion
may also be accomplished by ultrasonically bonding this additional
middle insulating layer to the first base layer 200. This
additional middle insulating layer may also be made by screen
printing an insulating material, by binding a photopolymer or by
heat-sealing an insulating material over the base layer 200.
[0033] Although the description of test sensor construction above
describes construction for a single sensor, the design and
materials used can also be used for making multiple sensors from
one large piece of each layer material. This would be accomplished
by starting with relative large pieces of the base layer material,
middle layer material and upper layer material. After a series of
preparations described above, a plurality of multiple test sensors
thus can be constructed to achieve mass production in a
cost-effective way.
[0034] It should be noted that although the particular embodiments
of the present invention have been described herein, the above
description is merely for illustration purpose. To the extent any
amendments, characterizations, or other assertions previously made
(in this or in any related patent applications or patents,
including any parent, sibling, or child) with respect to any art,
prior or otherwise, could be construed as a disclaimer of any
subject matter supported by present disclosure of this application,
Applicant hereby rescinds and retracts such disclaimer. Applicant
also respectfully submits that any prior art previously considered
in any related patent applications or patents, including any
parent, sibling, or child, may need to be re-visited. Further
modification and variations of the invention herein disclosed will
occur to those skilled in the respective arts and all such
modifications and variations are deemed to be within the scope of
the invention as defined by the appended claims.
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