U.S. patent application number 10/297888 was filed with the patent office on 2003-09-18 for biosensor.
Invention is credited to Miyazaki, Shoji, Tokunaga, Hiroyuki, Yamanishi, Eriko.
Application Number | 20030175946 10/297888 |
Document ID | / |
Family ID | 18967297 |
Filed Date | 2003-09-18 |
United States Patent
Application |
20030175946 |
Kind Code |
A1 |
Tokunaga, Hiroyuki ; et
al. |
September 18, 2003 |
Biosensor
Abstract
In a biosensor that detects introduction of a sample liquid into
an analyte feed passage using a detecting electrode, a means of
improving accuracy of detection is provided. The biosensor has: an
electrode system including measuring electrode (2), counter
electrode (3), and detecting electrode (4) on first electrically
insulated board (1); analyte feed passage (7) for introducing the
sample liquid; and reagent layer (5) used for quantifying a
substrate contained in the sample liquid. The means is
characterized in that detecting electrode (4) is spaced from
measuring electrode (2) by a distance sufficient for the sample
liquid to sufficiently cover measuring electrode (2) before the
sample liquid reaches detecting electrode (4).
Inventors: |
Tokunaga, Hiroyuki; (Ehime,
JP) ; Miyazaki, Shoji; (Ehime, JP) ;
Yamanishi, Eriko; (Ehime, JP) |
Correspondence
Address: |
Lawrence E Ashery
RatnerPrestia
One Westlakes Berwyn Suite 301
PO Box 980
Valley Forge
PA
19482-0980
US
|
Family ID: |
18967297 |
Appl. No.: |
10/297888 |
Filed: |
May 6, 2003 |
PCT Filed: |
April 11, 2002 |
PCT NO: |
PCT/JP02/03600 |
Current U.S.
Class: |
435/287.2 ;
205/777.5 |
Current CPC
Class: |
C12Q 1/001 20130101;
G01N 27/3272 20130101 |
Class at
Publication: |
435/287.2 ;
205/777.5 |
International
Class: |
C12M 001/34; G01F
001/64 |
Foreign Application Data
Date |
Code |
Application Number |
Apr 16, 2001 |
JP |
2001-116580 |
Claims
1. A biosensor for quantifying a substrate contained in a sample
liquid comprising: a first electrically insulated board and a
second electrically insulated board; an electrode system having at
least a measuring electrode, a counter electrode, and a detecting
electrode; an analyte feed passage for introducing the sample
liquid over said electrode system; and a reagent used for
quantifying the substrate contained in the sample liquid; wherein
said electrode system, said analyte feed passage, and said reagent
exist between said first electrically insulated board and said
second electrically insulated board; wherein said electrode system
is formed on one of all and part of an inner surface of at least
one of said first electrically insulated board and said second
electrically insulated board; and wherein said detecting electrode
is spaced from said measuring electrode by a distance sufficient
for the sample liquid to sufficiently cover said measuring
electrode before the sample liquid reaches said detecting
electrode.
2. The biosensor as set forth in claim 1, wherein said detecting
electrode is shaped to project so that a central portion thereof is
positioned nearest to said measuring electrode in said analyte feed
passage.
3. The biosensor as set forth in claim 1, wherein said detecting
electrode is shaped so that a central portion thereof is positioned
nearest to said measuring electrode and both edges thereof are
positioned farther to said measuring electrode than the central
portion in said analyte feed passage.
4. The biosensor as set forth in claim 1, wherein said detecting
electrode is shaped to project in a direction of an inlet of said
analyte feed passage in a central position within said analyte feed
passage.
5. The biosensor as set forth in any one of claims 2 through 4,
wherein said detecting electrode positioned within said analyte
feed passage has one of a V-shape, a U-shape, and a convex
shape.
6. The biosensor as set forth in any one of claims 1 through 5,
wherein said analyte feed passage has a width ranging from 0.5 to
2.0 mm.
7. The biosensor as set forth in any one of claims 1 through 6,
wherein said analyte feed passage has a height ranging from 0.05 to
0.3 mm.
8. The biosensor as set forth in any one of claims 1 through 7,
wherein said electrode system is divided by providing a slit in an
electrically conductive layer formed on one of all and part of an
inner surface of at least one of said first electrically insulated
board and said second electrically insulated board.
9. The biosensor as set forth in claim 8, wherein said slit is
formed by machining the electrically conductive layer using
laser.
10. The biosensor as set forth in any one of claims 1 through 9,
wherein an air vent in communication with said analyte feed passage
is formed.
Description
TECHNICAL FIELD
[0001] The present invention relates to a biosensor that quantifies
a substrate contained in a sample liquid.
BACKGROUND ART
[0002] A biosensor is a sensor that utilizes the
molecule-identifying function of a biological material, e.g. a
microorganism, enzyme, antibody, DNA, and RNA, and applies such a
biological material as a molecule-identifying element. In other
words, the biosensor utilizes the reaction occurring when an
immobilized biological material identifies a target substrate,
oxygen consumed by breathing of living organisms, enzyme reaction,
luminescence, and the like. Among biosensors, practical use of
enzyme sensors is developing. For example, enzyme sensors for
glucose, lactic acid, uric acid, and amino acid find applications
in medical instrumentation and food processing industry.
[0003] In an enzyme sensor, for example, electrons generated by the
reaction of a substrate contained in a sample liquid, i.e. an
analyte, with an enzyme or the like reduce an electron acceptor and
a measuring device electrochemically measures the amount of the
reduced electron acceptor. Thus, quantitative analysis of the
analyte is performed. An example of such a biosensor is a sensor
proposed in Patent Application No. PCT/JP00/08012.
[0004] In this biosensor, as shown in FIG. 4, electrically
insulated board 1 made of polyethylene terephthalate or other
materials has measuring electrode 2 (also referred to as a "working
electrode"), counter electrode 3, and detecting electrode 4 that
are made of electrically conductive materials and formed in
proximity to one another on the electrically insulated board.
Formed on these electrodes is regent layer 5 that contains an
enzyme specifically reacting with a particular component in the
sample liquid, an electron carrier, a water-soluble polymer, and
the like.
[0005] Laminated thereon and bonded thereto are spacer 6 having a
notch for forming analyte feed passage 7, and cover 8 (second
electrically insulated board) having air vent 9. One end of the
notch in spacer 6 is in communication with air vent 9 provided
through cover 8.
[0006] Described hereinafter is a system of checking for suction of
an analyte when the content of a substrate in a sample liquid, i.e.
the analyte, is determined using a conventional biosensor of such a
structure.
[0007] First, a sample liquid is supplied to the inlet of analyte
feed passage 7 while a constant voltage is applied between counter
electrode 3 or measuring electrode 2 and detecting electrode 4 by a
measuring device (not shown) coupled to the biosensor. The sample
liquid is sucked into analyte feed passage 7 by capillarity, passes
over counter electrode 3 and measuring electrode 2, and reaches
detecting electrode 4. Then, dissolution of reagent layer 5 starts.
At this time, the measuring device detects electrical changes
occurring between counter electrode 3 or measuring electrode 2 and
detecting electrode 4 and starts measuring operation.
[0008] However, such a biosensor has a problem. Counter electrode
3, measuring electrode 2, and detecting electrode 4 are disposed in
proximity to one another. Thus, when an amount of sample liquid
insufficient to fill analyte feed passage 7 is supplied as shown in
FIGS. 5 and 6, for example, the sample liquid reaches detecting
electrode 4 without completely covering measuring electrode 2 and
then the measuring operation starts. This makes the response value
lower than that given when the analyte feed passage is sufficiently
filled with the sample liquid as shown in FIG. 7, thus
deteriorating the performance of the biosensor. In the top views of
FIGS. 5 through 7, reagent layer 5 is not shown for simplicity.
[0009] The present invention aims to address the above-mentioned
problem. Therefore, it is an object of the present invention to
improve accuracy of detecting the analyte by adding new ideas on
the position and shape of the detecting electrode and to provide a
high-performance biosensor having excellent accuracy of
measurement.
DISCLOSURE OF INVENTION
[0010] In order to address the above-mentioned problem, according
to one aspect of the present invention, there is provided a
biosensor including:
[0011] a first electrically insulated board and a second
electrically insulated board;
[0012] an electrode system having at least a measuring electrode, a
counter electrode, and a detecting electrode;
[0013] an analyte feed passage for introducing the sample liquid
over the electrode system; and
[0014] a reagent used for quantifying a substrate contained in the
sample liquid. The biosensor is characterized in that the electrode
system, the analyte feed passage, and the reagent exist between the
first electrically insulated board and the second electrically
insulated board. The electrode system is formed on all or part of
the inner surface of at least one of the first electrically
insulated board and the second electrically insulated board. The
detecting electrode is spaced from the measuring electrode by a
distance sufficient for the sample liquid to sufficiently cover the
measuring electrode before the sample liquid reaches the detecting
electrode.
[0015] The detecting electrode of this biosensor can be shaped to
project so that the central portion of the detecting electrode is
positioned nearest to the measuring electrode within the analyte
feed passage. Moreover, the detecting electrode can be shaped so
that the both edges thereof are positioned farther from the
measuring electrode than the central portion.
[0016] The detecting electrode can also be shaped to project in the
direction of the inlet of the analyte feed passage in the central
position of the analyte feed passage.
[0017] These shapes of the detecting electrode positioned within
the analyte feed passage can be of V-shape, U-shape, or convex
shape.
BRIEF DESCRIPTION OF DRAWINGS
[0018] FIG. 1 is an exploded perspective view and a top view of a
biosensor in accordance with an exemplary embodiment of the present
invention.
[0019] FIG. 2 is an exploded perspective view and a top view
showing an example of another biosensor in accordance with an
exemplary embodiment of the present invention.
[0020] FIG. 3 is an exploded perspective view and a top view
showing an example in accordance with an exemplary embodiment of
the present invention that has an air vent disposed within an
analyte feed passage.
[0021] FIG. 4 is an exploded perspective view and a top view of a
conventional biosensor.
[0022] FIG. 5 is a drawing showing how a sample liquid is
introduced into an analyte feed passage.
[0023] FIG. 6 is a drawing showing how a sample liquid is
introduced into an analyte feed passage.
[0024] FIG. 7 is a drawing showing how a sample liquid is
sufficiently introduced into an analyte feed passage.
BEST MODE FOR CARRYING OUT OF THE INVENTION
[0025] A biosensor in accordance with an exemplary embodiment of
the present invention is demonstrated hereinafter with reference to
FIG. 1. Specifically described herein is an enzyme sensor using an
enzyme as a molecule-identifying element that specifically reacts
with a particular component in a sample liquid.
[0026] FIG. 1 is an exploded perspective view and a top view of a
biosensor in accordance with this embodiment. In FIG. 1, reference
numeral 1 shows a first electrically insulated board. Formed on
this first electrically insulated board 1 are measuring electrode
2, counter electrode 3, and detecting electrode 4 that are made of
electrically conductive materials.
[0027] In this embodiment, what largely differs from a conventional
biosensor is that detecting electrode 4 having a predetermined
shape is spaced from counter electrode 3 and measuring electrode 2
by a predetermined distance in analyte feed passage 7.
[0028] This predetermined distance means a distance sufficient for
the sample liquid to completely cover measuring electrode 2 after
the sample liquid is fed into analyte feed passage 7 before
reaching detecting electrode 4. This distance can be set
arbitrarily according to the width of the analyte feed passage.
[0029] As for the predetermined shape, it is desirable that
detecting electrode 4 is shaped to lie nearest to the measuring
electrode 2 in the central portion of analyte feed passage 7 and
farther to the measuring electrode along the both edges of analyte
feed passage 7 than in the central portion thereof. These shapes
include a V-shape, U-shape, and convex shape, and combinations
thereof. Among these shapes, a V-shape is most preferable.
[0030] Because the detecting electrode has such a distance and
shape, measurement of a sample liquid starts after the liquid has
completely covered the measuring electrode. When an amount of
sample liquid insufficient to completely cover measuring electrode
2 is supplied as shown in FIGS. 4 and 5, erroneous start of
measurement can be prevented. Moreover, for the above-mentioned
shape of detecting electrode 4, the detecting electrode can be
disposed nearer to the measuring electrode. Therefore, the amount
of sample liquid necessary for the biosensor to measure can be
reduced.
[0031] In the biosensor of FIG. 1, the space between measuring
electrode 2 and detecting electrode 4 does not work as an
electrode. However, as shown in FIG. 2, the space can be utilized
as a part of counter electrode 3.
[0032] Moreover, detecting electrode 4 described herein can be used
as a part of the counter electrode, as well as working as an
electrode for detecting an insufficient amount of analyte.
[0033] In the biosensor of FIG. 1, each of the electrodes is
disposed on the first electrically insulated board. However, these
electrodes can be divided and disposed not only on first
electrically insulated board 1 but also on second electrically
insulated board 8 opposed thereto.
[0034] Preferable materials of above-mentioned first electrically
insulated board 1 and second electrically insulated board 8 include
polyethylene terephthalate, polycarbonate, and polyimide.
[0035] Electrically conductive materials constituting each
electrode include single materials, such as noble metals (e.g.
gold, platinum, and palladium) and carbon, and composite materials,
such as carbon pastes and noble metal pastes.
[0036] The electrically conductive layer can be formed on first
electrically insulated board 1 or second electrically insulated
board 8 easily by such a method as sputtering vapor deposition for
the single materials, and by such a method as screen-printing for
the composite materials.
[0037] Each of the electrodes can be formed separately by forming
the electrically conductive layer on all or part of the surface of
first electrically insulated board 1 or second electrically
insulated board 8 by the above-mentioned sputtering vapor
deposition and screen-printing and other methods, and subsequently
providing slits therein using laser and other means. Similarly, the
electrodes can be formed by screen-printing using a printing plate
or mask having electrode patterns formed thereon in advance,
sputtering vapor deposition, and other methods.
[0038] Formed on the electrodes formed in this manner is reagent
layer 5 containing an enzyme, electron carrier, hydrophilic
polymer, and the like.
[0039] Examples of the usable enzyme include glucose oxidase,
lactate oxidase, cholesterol oxidase, cholesterol esterase,
uricase, ascorbate oxidase, bilirubin oxidase, glucose
dehydrogenase, and lactate dehydrogenase. Examples of the usable
electron carrier include p-benzoquinone and derivatives thereof,
phenazine methosulfate, methylene blue, and ferrocene and
derivatives thereof as well as potassium ferricyanide.
[0040] Examples of the usable hydrophilic polymer include
carboxymethyl cellulose, hydroxyethyl cellulose, hydroxypropyl
cellulose, methyl cellulose, ethyl cellulose, ethyl hydroxyethyl
cellulose, carboxymethyl ethyl cellulose, polyvinyl alcohol,
polyvinyl pyrrolidone, polyamino acids (e.g. polylysine),
polystyrene sulfonate, gelatin and derivatives thereof, acrylic
acids and salts thereof, methacrylic acids and salts thereof,
starch and derivatives thereof, maleic anhydrides and salts
thereof, and agarose gel and derivatives thereof.
[0041] Next, the first electrically insulated board 1 and second
electrically insulated board 8 are bonded to spacer 6 having a
notch to form analyte feed passage 7 for receiving a sample
liquid.
[0042] In order to reduce the amount of the sample liquid necessary
for the biosensor to measure, it is desirable that analyte feed
passage 7 has a width ranging from 0.5 to 2.0 mm and spacer 6 has a
thickness (height) ranging from 0.05 to 0.3 mm.
[0043] Examples of the preferable material of spacer 6 include
polyethylene terephthalate, polycarbonate, polyimide, polybutylene
terephthalate, polyamide, polyvinyl chloride, polyvinyliden
chloride, polyimide, and nylon.
[0044] Alternatively, integrated second electrically insulated
board 8 and spacer 6 can be bonded to first electrically insulated
board 1 to form analyte feed passage 7.
[0045] The reagent layer 5 can be placed in any position within
analyte: feed passage 7 for receiving the sample liquid as well as
on all or part of the surface of the electrodes, on condition that
the reagent layer will not deteriorate the performance of the
biosensor.
[0046] However, in order to realize quick detection of the sample
liquid after the supply thereof, it is desirable that reagent layer
5 exists on detecting electrode 4 or in the vicinity thereof.
[0047] The supply of a sample liquid to a biosensor structured of
such analyte feed passage 7 is realized by capillarity. In order to
realize smooth supply of the sample liquid, air vent 9 for letting
the air escape outside of the biosensor must be provided within
analyte feed passage 7.
[0048] Air vent 9 can be disposed in any position within analyte
feed passage 7 on condition that the air vent will not hinder the
supply of the sample liquid. Air vent 9 can be of any size that can
let the air escape smoothly. When a small air vent is disposed
within an analyte feed passage, the sample liquid is easily be lead
along the edges of the analyte feed passage. Thus, the shape of the
detecting electrode shown in FIG. 3 is most preferable.
[0049] In the biosensor of FIG. 3, arc slits are formed around the
reagent dropping position. Specifically, by providing a wave-like
arc slit 14 on the tip side of the sensor and slit 15 on the back
side of the feed passage, propagation of the reagent is easily
controlled in formation of reagent layer 5. These arc slits are
more effective in controlling the reagent than the arc slit
disclosed in the above-mentioned PCT patent application.
[0050] In addition, rendering hydrophilic nature to the inner
surface of the analyte feed passage 7 allows quicker and more
accurate introduction of the sample liquid into analyte feed
passage 7.
[0051] The methods of rendering hydrophilic nature include applying
surface-active agent to first electrically insulated board 1 or
second electrically insulated board 8 itself, or the surface
thereof, and roughening the surface of the board material by
sandblasting, electric-discharge machining, non-glare treatment,
matting, chemical plating, or the like.
[0052] Described hereinafter is a system of checking for suction of
an analyte when the content of a substrate in a sample liquid, i.e.
the analyte, is determined using a biosensor of such a
structure.
[0053] First, a sample liquid is fed to the inlet of the analyte
feed passage while a constant voltage is applied between the
counter electrode or the measuring electrode and the detecting
electrode by a measuring device (not shown) coupled to the
biosensor. The sample liquid is sucked into the analyte feed
passage by capillarity, passes over the counter electrode and the
measuring electrode, and reaches the detecting electrode. Then,
dissolution of the reagent layer starts. At this time, the
measuring device detects electrical changes occurring between the
counter electrode or the measuring electrode and the detecting
electrode and starts measuring operation.
[0054] In this embodiment, an enzyme sensor is described as an
example of a biosensor. However, the present invention can
similarly be applied to a biosensor that uses an antibody,
microorganism, DNA, RNA, or the like as well as the enzyme as a
molecule-identifying element specifically reacting with a
particular component in the sample liquid.
INDUSTRIAL APPLICABILITY
[0055] As mentioned above, the present invention can drastically
improve the accuracy of detecting the introduction of a sample
liquid into an analyte feed passage using a detecting electrode.
The present invention can also provide a high-performance biosensor
causing less error of measurement. Furthermore, the sample liquid
necessary for the biosensor to measure can be reduced. These
advantages can provide a biosensor that has high user operability
and can deal with a small amount of analyte.
List of reference numerals
[0056] 1 First electrically insulated board
[0057] 2 Measuring electrode
[0058] 3 Counter electrode
[0059] 4 Detecting electrode
[0060] 5 Reagent layer
[0061] 6 Spacer
[0062] 7 Analyte feed passage
[0063] 8 Second electrically insulated board (cover)
[0064] 9 Air vent
[0065] 10,11,12 Lead
[0066] 13 Sample liquid
[0067] 14,15 Arc slit
* * * * *