JP2001164030A - Porous membrane and production thereof - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a porous membrane that can rapidly be shortened the time required for developing specimens, for example, blood and can be used as a test paper for determination of specific components in the specimens, for example, blood sugar or the like with markedly high measurement accuracy. SOLUTION: This objective anisotropic porous membrane is obtained by wet-extruding a membrane dope including the first water-insoluble polymer as the membrane component and the second water-soluble and extractable components in which the concentration of the first component polymer is in the range of 12-15 wt.%.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a porous membrane for measuring the amount of a target component in a specimen, for example, for measuring a blood glucose level, a method for producing the same, and a test paper using the porous membrane. It is.

[0002]

2. Description of the Related Art A blood glucose measuring device (blood component measuring device) for measuring a blood glucose level is known. This blood glucose measurement device
The blood glucose level is quantified by optically measuring (colorimetrically measuring) the degree of coloration of the test paper that is colored according to the amount of glucose in the blood. In such a conventional blood glucose measuring device, the colorimetry of the test paper is performed by irradiating the test paper with light and measuring the intensity of the reflected light in a photometric unit having a light emitting element and a light receiving element. In this blood glucose measuring device, after performing an operation of supplying and developing blood (specimen) on a test paper, the test paper is inserted into a space where light shielding is ensured, and measurement of a blood glucose level is started. In addition, there is a problem that the time from the supply of blood to the test paper to the color measurement is not constant, resulting in a measurement error. Therefore, development of an automatic blood glucose measuring device capable of continuously and automatically performing a series of operations from supply / deployment to test paper to measurement is desired.

Further, the conventional test paper has a structure in which a reagent is carried on one sheet substrate made of a porous material capable of absorbing a specimen. In this test paper, since the pore diameter of the pores of the sheet substrate is as small as about 0.5 μm, water permeability,
That is, there is a problem that the spreadability is low, and it takes time to develop the specimen. Such a long time required for the development of the sample is particularly disadvantageous for the automatic blood glucose measuring device.

[0004] As means for solving such problems, (1) a porous first layer carrying a reagent which reacts with a specific component in a sample to produce a color, and a filter separated in the sample are separated. Laminated with a porous second layer having a function of filtering,
(2) The test paper according to (1), wherein the specimen is supplied and used from the first layer side, and (2) the first layer and the second layer each have hydrophilicity. (3) The pore size of the pores in the first layer is from 8 to 50.
the test paper according to the above (1) or (2),
(4) The test paper according to any one of (1) to (3), wherein the pore diameter of the pores in the second layer is 5 μm or less, and (5) the specimen is blood, and the separated substance is blood. The test paper according to any one of the above (1) to (4), which is a blood cell mainly containing red blood cells, is disclosed in JP-A-11-183474.

[0005] It is said that the above-mentioned problem is solved by using the test paper divided into the first layer and the second layer as described above. However, the use of such a test paper also has the following problems. The second porous membrane is required to be able to rapidly spread the plasma component reacted with the reagent to the measurement surface while filtering the blood cells. Filter blood cells
The effect is smaller as the pore size is reduced for removal, but if the pore size is too small, the development of the plasma component is slowed down. There is also a method of removing blood cells while maintaining the expansion speed by increasing the hole diameter on the entrance side and reducing the hole diameter on the exit side.However, if blood cell removal was performed immediately before the measurement surface, blood cell components The hemoglobin is seen through the porous structure, which affects the measurement accuracy.

[0006]

SUMMARY OF THE INVENTION An object of the present invention is to provide a test paper for measuring a specific component in a sample, which can drastically reduce the time required for developing the sample and which has extremely high measurement accuracy. An object of the present invention is to provide a porous film to be used and a method for producing the porous film.

[0007]

This and other objects are achieved by the present invention described below. (1) In the present invention, the average pore diameter is 0.1 to 2 μm and the film thickness is 5
A porous membrane having a pore size of 0 to 200 μm and a porosity of 50 to 95%, and a ratio of the average pore diameter on one surface to the average pore diameter on the other surface being 1.5 or more. . (2) The present invention is the anisotropic porous membrane according to the above (1), through which red blood cells do not pass.

(3) The present invention provides a stock solution containing a water-insoluble first component polymer as a membrane component and a water-soluble second component to be extracted, wherein the concentration of the first component polymer is 12 to 15% by weight. Is an anisotropic porous film obtained by wet film-forming. (4) In the present invention, the average pore diameter is 0.1 to 2 μm and the film thickness is 5
The anisotropic described in (3) above, wherein the porous membrane has a pore size of 0 to 200 μm and a porosity of 50 to 95%, and the ratio of the average pore size on one surface to the average pore size on the other surface is 1.5 or more. Porous membrane.

(5) The present invention is the anisotropic porous membrane according to the above (3) or (4), through which red blood cells do not pass. (6) The invention according to (3) to (5), wherein the charge ratio of the first component polymer and the second component of the stock solution is 3: 1 to 1.5: 1. It is an isotropic porous membrane.

(7) The present invention provides the method according to (3) to (6), which is obtained by performing an aqueous coagulation bath containing a solvent for the film forming stock solution at 60 to 80 w / w% to perform wet film formation. It is an isotropic porous membrane. (8) The present invention is the anisotropic porous membrane according to the above (3) to (7), wherein the first component polymer is polyether sulfone.

(9) The present invention is the anisotropic porous membrane according to the above (3) to (7), wherein the second component is polyvinylpyrrolidone. (10) The present invention is a test paper obtained by laminating another porous membrane on the surface having a small average pore diameter of the porous membrane according to the above (1) to (9).

(11) The present invention provides a stock solution containing a water-insoluble first component polymer as a membrane component and a water-soluble second component as a component to be extracted, wherein the concentration of the first component polymer is 12 to 15% by weight. This is a method for producing an anisotropic porous film, characterized in that a wet film is formed by using the method. (12) The method according to the above (11), wherein the stock ratio of the first component polymer to the second component is 3: 1 to 1.5: 1. This is a method for producing an isotropic porous membrane.

(13) The invention according to (11) to (12), wherein the wet film formation is performed by performing an aqueous coagulation bath containing a solvent of the film forming stock solution at 60 to 80 w / w%. This is a method for producing an anisotropic porous membrane. (14) The present invention is the method for producing an anisotropic porous membrane according to any one of (11) to (13), wherein the first component polymer is polyether sulfone. . (13) The present invention is the method for producing an anisotropic porous membrane according to any one of (11) to (13), wherein the second component is polyvinylpyrrolidone.

[0014]

BEST MODE FOR CARRYING OUT THE INVENTION The anisotropic porous membrane of the present invention has an average pore size on one surface smaller than the average pore size on the other surface, and supplies a sample containing a specific component from one surface. Then, a specific component is measured from the other surface by an optical method or the like. Therefore, it is necessary to separate suspended components such as blood cells by filtration and to rapidly spread a specific component such as a plasma component reacted with a reagent from one surface to the other surface. To filter and remove suspended matter such as blood cells,
The problem can be solved by reducing the pore size, but if the pore size is too small, the development of a specific component such as a plasma component is delayed. In addition, there is a method of removing floating substances such as blood cells while maintaining the developing speed by increasing the pore size on the side for supplying a specific component such as a plasma component reacted with the reagent and reducing the other pore size. Since the filtration / removal of the object is performed near the surface to be measured, the blood pigment of the blood cell component is seen through the porous structure, which affects the accuracy of the measurement.

[0015] Therefore, by making the pore size of the surface on the sample supply side containing the specific component smaller and increasing the other pore size, the suspended matter such as blood cells can be accurately filtered and removed. At the same time, it is possible to improve the development speed and measurement accuracy of a specific component such as a plasma component on the surface on the side to be measured.

As a specific structure of the anisotropic porous membrane of the present invention, the average pore size is 0.1 to 2 μm, preferably 0.3 to 2 μm.
1.6 μm, more preferably 0.5 to 1.3 μm,
The ratio of the average pore size of the surface on the side where the specific component in the sample is measured to the average pore size of the other surface is 1.5 or more, preferably 2.0.
As described above, it is more preferably 2.3 or more.

The thickness of the anisotropic porous film of the present invention is not particularly limited, but is 50 to 200 μm, preferably 70 to 18 μm.
0 μm, more preferably 80 to 150 μm. If the film thickness is less than 50 μm, the film strength becomes insufficient, and
If the thickness exceeds 0 μm, it takes time to develop the specimen.

Although the porosity of the anisotropic porous membrane of the present invention is not particularly limited, it is 50 to 95%, preferably 70 to 90%.
%, More preferably 75 to 85%. Porosity of 50
If it is less than 95%, it becomes impossible to absorb and develop a required amount of the sample, and if it exceeds 95%, the membrane strength becomes insufficient.

As the polymer used as the film material of the anisotropic porous membrane of the present invention, nitrocellulose, polyvinyl difluoride, cellulose acetate, polysulfone, polyether sulfone, polyethylene and the like can be used.
In particular, when a reagent used for measuring a blood glucose level is supported, polyether sulfone can be suitably used with the least deterioration of the reagent activity with time.

As a method for producing the anisotropic porous film of the present invention, wet film formation is a preferable method. As a method for producing a porous film, there are also known a melt film formation, a dry film formation, and the like.However, in order to produce an anisotropic film in which the pore size of one surface is different from the pore size of the opposite surface. Wet film formation is the preferred method. The production method of the present invention is carried out by spreading a film-forming stock solution in a film form, performing an aqueous coagulation bath and drying.

The step of spreading the film-forming stock solution into a film is performed by, for example, spreading or spreading the film-forming stock solution on the surface of a substrate such as glass. This method increases the anisotropy of the finally obtained porous membrane and increases the ratio of the pore diameter of one surface (surface in contact with air) to the pore size of the other surface (surface in contact with the base material). It is effective to keep it at 1.5 or more.

The stock solution used in the present invention contains a water-insoluble first component polymer as a membrane component and a water-soluble second component as a component to be extracted, and the concentration of the first component polymer is 12 to 15 watts.
t% is desirable. The average pore diameter of the porous membrane of the present invention is preferably in the range of 0.1 to 2 μm. Therefore, if the concentration of the first component polymer exceeds 15 wt%, the pore diameter becomes small, and if it is less than 12 wt%, the pore diameter becomes too large. Further, when the polymer is produced from a single polymer solution containing only the first component polymer, the polymer has a dense structure due to the cohesive force of the polymer. However, the water-soluble second component, which is the component to be extracted, is added to the stock solution. Thereby, aggregation of the polymer is suppressed, and pores are formed in the space after the components are extracted and removed, so that the porosity can be improved.

As the first component polymer, nitrocellulose, polyvinylidene fluoride, cellulose acetate,
Polysulfone, polyethylene, etc. can be used, but when the finally obtained porous membrane supports a reagent used for measuring blood glucose level, polyether sulfone is preferably used since the reagent has the least deterioration over time. it can.
As the water-soluble second component to be extracted, polyvinylpyrrolidone, polyethylene glycol, polyacrylamide, polyacrylic acid, which does not completely dissolve in the first component polymer but dissolves in the solvent and can be easily extracted and removed after coagulation,
Examples include hydroxypropyl cellulose and methyl cellulose. In particular, polyvinylpyrrolidone does not dissolve in nitrocellulose, polyvinyl difluoride, cellulose acetate, polysulfone, polyethylene, polyethersulfone, etc., but dissolves in a polar solvent that dissolves these polymers, and can be extracted and removed with water after coagulation. It is desirable to have In addition, polyvinylpyrrolidone is present in a small amount even after extraction but remains in the finally obtained porous membrane, and has an effect of securing the hydrophilicity of the porous membrane from its water affinity.

The solvent of the stock solution for the purpose of dissolving the first component polymer and the water-soluble second component is, specifically, N 2
Examples thereof include organic polar solvents such as -methyl-2-pyrrolidone, dimethylformamide, dimethylsulfoxide, and dimethylacetamide, and particularly preferred is N-methyl-2-pyrrolidone.

The charge ratio of the first component polymer of the stock solution to the water-soluble second component to be extracted is 3: 1 to 1.
Preferably, it is 5: 1. If the amount of the first component polymer is too large, the effect of adding the component to be extracted as the second component is not obtained,
This is because large pores are formed inside and a stable porous structure cannot be obtained, and a dense structure is obtained when the amount of the second component to be extracted is too large.

The aqueous coagulation bath is a water-based coagulation bath containing 60 to 80 w / w%, preferably 65 to 75 w / w% of the solvent of the above-mentioned stock solution, at a temperature of 20 to 60 ° C., preferably 25 to 50 w / w.
It is desirable to perform the reaction at a temperature of 0.5 ° C. for 0.5 to 20 minutes, preferably 1 to 10 minutes. If the coagulation bath is performed with 100% non-solvent, the film-forming stock solution spread in the form of a film rapidly solidifies on its surface, so that a layer called a dense skin layer is formed. I can't get it. Therefore, slow coagulation is realized by performing an aqueous coagulation bath containing 60 to 80 w / w% of the solvent of the film forming stock solution.
A porous structure is also formed on the surface. If the concentration of the solvent of the film forming stock solution in the coagulation bath is less than 60 w / w%, the above-mentioned effect of the addition of the solvent of the film forming stock solution cannot be obtained, and if it exceeds 80 w / w%, the coagulation ability becomes insufficient.

When the temperature is lower than 20 ° C., the deposition rate of the first component polymer is too high, resulting in a dense film. If the temperature is higher than 60 ° C., the deposition rate of the first component polymer is too slow to form a film. On the other hand, if the time is shorter than 0.5 minute, the first component polymer is not completely deposited, so that no film is formed. If the time is longer than 20 minutes, the film structure is not changed and the production efficiency is lowered.

The drying step is not particularly limited, for example, by natural drying or an electric oven at a temperature of 25 to 100 ° C., preferably 30 to 80 ° C., for a time of 1 to 24 hours, preferably 4 to 18 hours. And the like.

The anisotropic porous membrane of the present invention may contain a hydrophilic agent, be made of a material having hydrophilicity, or be subjected to a hydrophilizing treatment in order to quickly supply and spread the specimen. desirable. As a hydrophilizing agent, Triton X-
Surfactants such as 100, water-soluble silicone, hydroxypropylcellulose, polyethylene glycol, polypropylene glycol and the like. Examples of the hydrophilization treatment include treatment methods such as plasma treatment, glow discharge, corona discharge, and ultraviolet irradiation.

Although the anisotropic porous membrane of the present invention can be used alone, it can be used as a test paper obtained by laminating another porous membrane on the surface of the present porous membrane having a small average pore diameter. It is desirable to do. The laminating method is not particularly limited, and examples thereof include a method of simply fixing the periphery of the overlap and a method of bonding and fusing.

As another porous membrane, there can be mentioned a porous membrane which carries a reagent which reacts with a specific component in a sample to give a color.
In addition, whether or not the porous film is anisotropic is not particularly limited. Examples of the reagent that reacts with the specific component in the sample described above include enzyme agents such as glucose oxidase (GOD) -like enzyme, peroxidase (POD) -like enzyme, ascorbate oxidase-like enzyme, alcohol oxidase-like enzyme, and cholesterol oxidase-like enzyme; And 4
Coloring agents such as -aminoantipyrine and N-ethyl-N- (2-hydroxy-3-sulfopropyl) -m-toluidine; one or more of these can be used.

The test paper of the present invention is used by inserting it into a chip that can be attached to and detached from a measuring device for a specific component in a sample, or a measuring device itself. Examples of the measuring device include a device for quantitatively or qualitatively measuring blood sugar, cholesterol, neutral fat, and the like, and urine sugar, protein, occult blood, and the like.

[0033]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, specific embodiments of the present invention will be described. The porous membranes of the respective examples and comparative examples were formed under the following conditions. First, a film-forming stock solution shown in Table 1 was linearly supplied onto a substrate (glass plate) with a 50 ml syringe, and this was spread on a glass plate with an applicator having a gap of 125 μm. This was immersed in a coagulation bath composed of an aqueous solution of N-methyl-2-pyrrolidone (NMP) prepared at the solvent concentration shown in Table 1 to precipitate the first component polymer. The temperature of the coagulation bath was 35 ° C. Thereafter, the solvent component and the water-soluble second component were extracted and removed in a water bath, and dried in an oven at 40 ° C. to obtain a test paper. Polyether sulfone (Sumika Excel 7300P, manufactured by Sumitomo Chemical Co., Ltd.) as the first component polymer, polyvinylpyrrolidone (BASF povidone K-90, manufactured by BASF) as the second component, and N-methyl-2-pyrrolidone (solvent) as the solvent. BASF).

Table 2 shows the average pore size of each of the formed films.
The average pore size of the membrane in each case was determined according to ASTM F316-86 by Capillary Flow Porometry.
orometry). The measuring device used was a palm porosimeter (manufactured by PMI). The surface average pore diameter of the film in each example was determined by measuring an image taken with a scanning electron microscope (JSM-840, manufactured by JEOL) using an image analyzer (IP-1000P).
C, manufactured by Asahi Kasei Corporation), the hole diameter of the holes in the visual field was calculated as the equivalent circle diameter in terms of area, and the arithmetic mean was taken as the surface average hole diameter. Therefore, a correlation does not always hold between the average pore diameter of the membrane and the average pore diameter of the surface. The film thickness was measured with a micrometer (made by Mitutoyo Seiki). The porosity was measured by a gravimetric method.

[0035]

[Table 1]

[0036]

[Table 2]

(Test Example 1) The following experiments were performed using the porous membranes of the above Examples and Comparative Examples. The membrane to be evaluated was coated with the coating reagent shown below. A spectrophotometer (UV-2400 (P
C) S The sample was fixed to a sample holder (manufactured by Shimadzu Corporation), and 5 μl of human blood was added to a surface having a small pore size using a micropipette (manufactured by Eppendorf), and the time change of the reflection absorbance on the opposite surface was measured. The time from when the change rate of the reflectance for one second exceeded 1% to when the change rate of the reflectance for one second fell below 1% was defined as Δt. Table 3 shows the results.

Coating reagents: GOD, POD and 4-aminoantipyrine, N-ethyl-N- (2-hydroxy-3-sulfopropyl) -m-toluidine (TOO
S), Triton X-100

Measurement conditions Time change Photometric value: reflectance Wavelength: 610 nm Slit width: 2.0 nm Timing mode: auto Measurement time: 90 seconds Sampling pitch: 0.1 sec Cell number: 1 Data number: 901

(Test Example 2) The following experiments were performed using the porous membranes of the above Examples and Comparative Examples. The membrane to be evaluated was coated with the coating reagent shown above. A spectrophotometer (UV-2400 (P
C) S The sample was fixed to a sample holder (manufactured by Shimadzu Corporation), and 5 μl of human blood was added to the surface on the entrance side with a micropipette (manufactured by Eppendorf), and the reflection absorption spectrum of the reflection absorption of the opposite surface was measured. In addition, blood was added from the side having a small pore diameter. The presence or absence of the effect of hemoglobin was determined by comparing with the spectrum when plasma was added. Table 3 shows the results.

Measurement conditions Reflection absorption spectrum Photometric value: reflectance Wavelength range (nm): start 700 end 500 Scan speed: medium speed Slit width: 2.0 nm Sampling pitch: 1.0 nm

[0042]

[Table 3]

[0043]

According to the porous membrane of the present invention, the developing speed of the specimen is high, the time required for the development can be shortened, and at the time of color measurement, the suspended matter in the specimen is filtered and removed. Accuracy measurements can be made. The porous membrane of the present invention, by laminating with other porous membranes, can dramatically reduce the time required for sample development, and has extremely high measurement accuracy, for measuring specific components in a sample. Test strips can be provided.

In particular, the porous membrane of the present invention can be effectively used for a blood glucose test paper for measuring sugar in blood,
The speed of blood development is high, the time required for blood development can be shortened, and sufficient filtration of filtered substances such as red blood cells
It removes and eliminates the influence of hemoglobin such as red blood cells, and can perform more accurate measurement.

According to the method for producing a porous membrane of the present invention, the development speed of a specimen is high, the time required for development can be shortened, and at the time of color measurement, suspended matter in the specimen is filtered and removed. A method for manufacturing a porous film capable of performing highly accurate measurement can be provided. The porous film obtained by the production method of the present invention is laminated with another porous film,
It is possible to provide a test strip for measuring a specific component in a sample, which can drastically reduce the time required for developing the sample and has extremely high measurement accuracy.

In particular, since the porous membrane obtained by the production method of the present invention is effectively used for a blood glucose test paper for measuring the sugar content in blood, the development speed of blood is high and the time required for development is short. In addition to this, it is possible to sufficiently filter out and remove filtered substances such as red blood cells, to eliminate the influence of hemoglobin such as red blood cells, and to perform more accurate measurement.

 ──────────────────────────────────────────────────続 き Continued on the front page F term (reference) 2G042 AA01 BD06 BD12 BD16 CA10 CB03 DA08 FA11 FB07 FC03 GA04 HA08 2G045 AA01 AA13 BA01 BA11 BB06 CA26 4F074 AA37 AA64 CB31 DA44 4J002 BJ001 CN032 GD05

Claims (13)

[Claims] An average pore size of 0.1 to 2 μm and a film thickness of 50 to 50.
An anisotropic porous membrane having a thickness of 200 μm and a porosity of 50 to 95%, wherein the ratio of the average pore diameter on one surface to the average pore diameter on the other surface is 1.5 or more. 2. A film-forming stock solution containing a water-insoluble first component polymer serving as a membrane component and a water-soluble second component serving as a component to be extracted, wherein the concentration of the first component polymer is 12 to 15% by weight. An anisotropic porous membrane obtained by this. 3. An average pore diameter of 0.1 to 2 μm and a film thickness of 50 to 50 μm.
The anisotropic porous film according to claim 2, wherein the porous film is 200 µm and has a porosity of 50 to 95%, and the ratio of the average pore size on one surface to the average pore size on the other surface is 1.5 or more. Membrane. 4. The anisotropic porous material according to claim 2, wherein the charge ratio of the first component polymer to the second component of the stock solution is from 3: 1 to 1.5: 1. film. 5. The anisotropic porous film according to claim 2, which is obtained by performing a wet film formation by performing an aqueous coagulation bath containing a solvent of the film forming stock solution at 60 to 80 w / w%. 6. The anisotropic porous membrane according to claim 2, wherein said first component polymer is polyether sulfone. 7. The anisotropic porous membrane according to claim 2, wherein said second component is polyvinylpyrrolidone. 8. A test paper obtained by laminating another porous membrane on the surface of the porous membrane according to claim 1 having a small average pore diameter. 9. A wet process comprising a film-forming stock solution containing a water-insoluble first component polymer as a membrane component and a water-soluble second component as a component to be extracted, wherein the concentration of the first component polymer is 12 to 15 wt%. A method for producing an anisotropic porous membrane, which comprises forming a membrane. 10. The anisotropic film according to claim 9, wherein the stock ratio of the first component polymer to the second component is 3: 1 to 1.5: 1. A method for producing a porous membrane. 11. The anisotropic porous membrane according to claim 9, wherein an aqueous coagulation bath containing 60 to 80% w / w of the solvent for the stock solution is used to perform wet membrane formation. Production method. 12. The method for producing an anisotropic porous membrane according to claim 9, wherein said first component polymer is polyether sulfone. 13. The method for producing an anisotropic porous film according to claim 9, wherein said second component is polyvinylpyrrolidone.