JP2000300973A - Blood purification hollow fiber membrane - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a blood purification hollow fiber membrane not only superior in properties of removing a dialysis complication inducting substance of approximately 10,000 molecular weight represented by B2-microblobulin but also superior in properties of removing a substance of approximately 20,000 molecular weight, provided with the improving effect of clinical symptoms and also controlling as much as possible the leakage of albumin as a useful protein. SOLUTION: When a bovine blood of 30±3% hematocrit value and 6.5±0.5 g/dl protein concentration is made to flow at the 200 ml/min flow rate and a blood filtration is applied therein at the 15 ml/min filtration flow velocity, the in-liquid protein concentration in a module of 1.5 m2 membrane area of a blood purification hollow fiber membrane is 200 mg/dl-1,000 mg/dl after 15 minutes from the start of the application, and the in-liquid protein concentration after 120 minutes from the start of the application is 50 mg/dl-200 mg/dl.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention
Blood purification membrane. For more information on chronic renal failure
Be stable and efficient when used for treatment_Two-Micro gro
Blin (hereinafter β _TwoUrine of molecular weight represented by M)
Albumin, a useful protein that can remove toxic substances
A hollow fiber membrane for blood purification that can control leakage
You.

[0002]

2. Description of the Related Art In recent years, dialysis complications associated with an increase in long-term dialysis patients have attracted attention, and not only low molecular weight substances such as urea and creatinine, but also medium high molecular weight substances (low molecular weight proteins).
The removal target has expanded to this point. It has also been suggested that the effects of improving clinical symptoms such as pruritus and pain and improving lipid metabolism are due to the removal of substances having a molecular weight of about 20,000. Membrane reported to be effective in reducing itching and irritability (Kidney and Dialysis Supplement 36 High Performance Membrane '94: 70,
1994, Kidney and Dialysis Supplement 36 High Performance Membrane '9
4: 132, 1994).

However, these membranes cause too much albumin leakage per treatment, and when used for a long period of time, may cause hypoproteinemia and conversely worsen the prognosis of patients. It has also been reported that a synthetic polymer membrane represented by polysulfone has an albumin leakage of 1 g or less per treatment and excellent β ₂ M removal performance, but its effect on itching and irritation is β _{Although the} 2M removal performance was low, it was inferior to the above-mentioned membrane having a low albumin leakage amount.
That is, to ensure the safety of patients, a membrane having a small amount of albumin leakage and excellent in removing performance of a substance having a molecular weight of about 20,000 which leads to a reduction in itchiness and irritability has not been obtained.

[0004]

DISCLOSURE OF THE INVENTION The present invention is intended to solve the above-mentioned drawbacks, and an object of the present invention is to excel in removing dialysis complication-inducing substances having a molecular weight of about 10,000 represented by β ₂ M. Another object of the present invention is to provide a hollow fiber membrane for blood purification, which is excellent in removability of a substance having a molecular weight of about 20,000 which has an effect of improving clinical symptoms and which suppresses leakage of albumin which is a useful protein as much as possible.

[0005] In order to efficiently remove substances having a molecular weight of about 20,000, which are substances causing itching and irritability, a pore diameter larger than that of a normal dialysis membrane is required. However, current membrane manufacturing technology cannot completely separate substances with a molecular weight of about 20,000 and albumin, which is a protein required for the human body, and it is quite necessary to improve clinical symptoms such as itching and irritability. Amount of albumin leak occurs at the same time. As a specific number, improvement of clinical symptoms such as itchiness and irritability is particularly well recognized when the protein concentration in the filtrate at the time of blood filtration (almost all albumin) is 200 mg / dl or more. However, when the protein concentration in the filtrate is 200 mg / dl or more, the usual dialysis filters about 3 L per treatment, so the amount of aluminum leaked per treatment is 6 g or more, and as described above, hypoproteinemia may occur. May cause. For this reason, it seemed impossible to achieve both improvement of clinical symptoms of itching and irritability and safety with less albumin leakage.

However, as a result of further study, it was found that the membrane had a protein concentration of 200 mg / dl or more at the initial stage of hemofiltration. Then, it was found that the performance of removing substances having a molecular weight of about 20,000 was kept high over the entire treatment time, and the present invention was reached.

[0007]

That is, the present invention provides the following hollow fiber membrane for blood purification. Membrane area 1.5
Hematocrit 30 ± 3% in m ² of the module, the protein concentration
6.5 ± 0.5 g / dl of bovine blood at a flow rate of 200 ml / min, and a protein concentration in the filtrate of 15 minutes after blood filtration at a filtration flow rate of 15 ml / min is 200 mg / dl or more and 1000 mg / dl or less, 120 minutes A hollow fiber membrane for blood purification, wherein the subsequent filtrate has a protein concentration of 50 mg / dl or more and 200 mg / dl or less.

[0008] In the present invention, the protein concentration in the filtrate after 15 minutes must be 200 mg / dl or more and 1000 mg / dl or less. Preferably it is 300 to 800 mg / dl, more preferably 400 to 600 mg / dl. When the content is 200 mg / dl or more, a molecular weight substance having a molecular weight of about 20,000 can be efficiently removed. Even if it is less than 200 mg / dl, a substance having a molecular weight of about 10,000 can be removed relatively efficiently, but clinical symptoms such as itching and irritability are hardly improved. On the other hand, the protein concentration in the filtrate after 15 minutes was 1000 mg / dl.
The following is preferred. If it exceeds 1000 mg / dl, it will be difficult to keep the total amount of protein removed during treatment within a safe range even if the protein concentration in the filtrate decreases over time.

In the present invention, the measurement of the protein concentration in the filtrate immediately after the start of blood filtration is performed after 15 minutes for the following reason. In the present invention, as is clear from the object of the present invention, it is necessary that the pore diameter of the membrane immediately after blood filtration be a certain value or more, and therefore, the protein concentration in the filtrate is measured accurately as soon as possible after the start of blood filtration. It is desirable to do. However, the membrane has been previously primed with physiological saline before coming into contact with blood, and the filtrate side in the membrane and in the module is filled with physiological saline. For this reason, even if blood is passed and filtration is started, the filtrate obtained first is diluted with physiological saline, and it is difficult to obtain an accurate protein concentration in the filtrate. Filtrate flow rate is 15ml / min
In this case, the minimum time within which the effect of dilution with physiological saline can be neglected is 15 minutes after the start of filtration.

In the present invention, the protein concentration in the filtrate after 120 minutes must be 50 mg / dl or more and 200 mg / dl or less. If the protein concentration in the filtrate after 120 minutes is 50 mg / dl or more, the molecular weight
Removal of about 20,000 molecular weight substances is performed efficiently over the entire treatment time. If it is less than 50 mg / dl, the substance removal performance at the beginning of treatment is high, but the removal effect cannot be maintained over the entire treatment time, which is not preferable. If the protein concentration in the filtrate after 120 minutes exceeds 200 mg / dl, protein leakage will increase over the entire treatment time and hypoproteinemia will easily occur.

[0011] The causative substance of itching and irritability is estimated to have a molecular weight of about 20,000, but has not been identified yet. Further, if the molecular weight is the same but the shape of the molecule is different, the removal characteristics when filtered through a membrane cannot be defined unconditionally. 15 in our study
Molecular weight when the protein concentration in the filtrate after 200 minutes is 200 mg / dl or more
It has been observed that 20,000 fluorescently labeled dextrans have a sieving coefficient of 0.5 or more. We introduced the sieving coefficient of fluorescently labeled dextran with a molecular weight of 20,000 as a criterion for objectively assessing clinical effects in the laboratory.
It was thought that itching and irritation could be eliminated when the ratio was 0.5 or more.

The present invention is to provide a hollow fiber membrane having both high removal efficiency and safety by adjusting the protein concentration in the filtrate to an appropriate range. It belongs to the category called flux dialysis membrane. That is, since the removal efficiency has a correlation with the water permeability of the dialysis membrane, the water permeability of the hollow fiber membrane of the present invention is preferably 10 ml / m ² / hr / mmHg or more, more preferably 20 ml / m ² / hr / mmHg or more. Having such high water permeability and setting the filtrate protein concentration in the above-mentioned range, an excellent therapeutic effect can be expected.

The hollow fiber membrane of the present invention needs to have a sieving coefficient of albumin of 0.15 to 0.6 as measured using a phosphate buffer solution (pH 7.4) containing 5 wt% albumin. When the sieving coefficient of albumin is less than 0.15, β ₂ M and the like are not sufficiently removed when blood purification is actually performed. If the sieving coefficient for albumin exceeds 0.6, the amount of albumin leakage necessary for the human body increases. In other words, the necessity for the sieving coefficient of albumin in the aqueous solution to be in the range of 0.15 to 0.6 can be said to be a size in which the pore diameter reduced by the protein gel layer formed during actual blood purification is added.

Examples of the hollow fiber membrane material in the present invention include regenerated cellulose, modified cellulose, polysulfone, acrylonitrile, etc. Any material may be used as long as it has a small amount of protein adsorbed, and cellulose having excellent water permeability and solute permeability. Acetate is preferred, and cellulose triacetate is particularly preferred from the viewpoint of biocompatibility.

The spinning method of the hollow fiber membrane of the present invention is not particularly limited, and can be obtained by a known spinning method such as melting, dry, wet, and dry-wet methods. The film is preferably formed by a dry-wet spinning method using a forming agent. Any hollow forming agent may be used as long as it is inert to the spinning dope. For example, liquid paraffin or isopropyl myristate can be used as the liquid, and dry air, nitrogen, helium, argon or the like can be used as the gas.

The hollow fiber membrane of the present invention can be produced, for example, as follows, but the present invention is not limited to the following. A spinning solution consisting of 16 to 25 parts by weight of cellulose acetate, 45 to 75.6 parts by weight of a solvent, and 8.4 to 39 parts by weight of a non-solvent is heated and dissolved at 130 to 190 ° C., extruded from the outside of a double-tube spinneret, and from the inside. Extrudes the hollow former. After the extruded spinning solution has passed through the gaseous atmosphere,
Excess solvent in a washing bath, coagulated in a coagulating liquid at 5050 ° C.
Wash non-solvent. In order to obtain the hollow fiber membrane of the present invention,
A spinning solution consisting of a membrane material such as cellulose triacetate, a solvent, and a non-solvent is discharged from a tube-in-orifice type spinneret into a gaseous atmosphere and then guided to a coagulation bath to produce a hollow fiber membrane having an outer diameter of 1000 μm or more. It is preferable to use a base and adjust the gas passage time to 0.5 seconds or more. Here, the gas passage time is calculated from the linear velocity of the spinning solution discharged from the spinneret and the gas atmosphere passage length. Depending on the spinning speed, the AG length is 50 mm or more, and even 100 m
m or more is desirable. Further, it is preferable to adjust the draft ratio represented by the ratio of the roller speed at the outlet of the coagulation bath to the linear speed of the spinning dope discharged from the spinneret to a value between 10 and 30. Further, the temperature of the coagulation bath is preferably adjusted to 30 ° C. or higher. By using these combinations, the obtained hollow fiber membrane has an appropriate balance between the amorphous region and the crystalline region, and obtains a blood purification membrane having good water permeability and solute permeability and satisfying the parameters of the present invention. I found that it became possible.

Thereafter, the membrane fiber is impregnated with glycerin by passing the hollow fiber through a 30 to 70% by weight aqueous glycerin solution by a conventional method, and wound up through a drying step. The solvent is not particularly limited as long as it dissolves cellulose acetate, but N, N-dimethylacetamide, N, N
-It is preferable to use a polar solvent such as dimethylformamide, γ-butyrolactone, N-tylpyrrolidone, dimethylsulfoxide, N, N-dimethylimidazolidinone. These can be used alone or in combination. Examples of the non-solvent include polyhydric alcohols such as ethylene glycol, triethylene glycol, polyethylene glycol, and glycerin, and lower alkyl ether derivatives thereof, and these can be used alone or as a mixture.

The hollow fiber membrane for blood purification produced by such a method has a good balance between the pore diameter and the number of pores, the permeability of low-molecular to medium-molecular solutes (low-molecular protein), and albumin, a useful protein. It is suitable for ultrafiltration, dialysis, and diafiltration because of its excellent cut-off property, and specifically used for hemodialysis, hemofiltration dialysis and the like. Although the theoretical basis of the present invention has not been confirmed, the inventors think as follows. In other words, it is necessary to make the pore size larger than that of a normal dialysis membrane in order to remove the substances that cause itching and irritation.
Therefore, it is apparent that it is necessary to set the sieving coefficient of albumin measured using a phosphate buffer containing 5 wt% albumin and the filtrate protein concentration 15 minutes after the start of filtration within a certain range. Having a pore diameter within the above range, and having an appropriate balance between the amorphous region and the crystalline region, the blood protein has a specific adsorption form on the blood contact surface of the membrane when the blood comes into contact with the membrane. It is considered that it acts as the next separation membrane and exhibits excellent separation efficiency that cannot be achieved by the current membrane-forming technology, that is, high separation of albumin from substances having a molecular weight of about 20,000.

[0019]

EXAMPLES Hereinafter, the present invention will be described in more detail with reference to examples, but the present invention is not limited to the examples.

Example 1 Cellulose triacetate 19
Parts by weight, 56.7 parts by weight of N-methylpyrrolidone, and 24.3 parts by weight of triethylene glycol were dissolved by heating at 170 ° C., and further degassed under vacuum to obtain a spinning solution of cellulose triacetate. This was filtered through a sintered filter having a pore diameter of 20 μm to remove impurities, and then discharged at a discharge linear velocity of 321 cm / min from the outside of a double-tube structure die having an outer diameter of 1400 μm, and simultaneously, liquid paraffin was discharged from the inside of the die. The hollow fiber spinning solution passed through 7.5 cm 2 in a gas atmosphere for 1.4 seconds, and then N-methylpyridone / triethylene glycol / water = 10.5 / 4.5 /
It was led to a coagulation bath consisting of 85 and a coagulation bath at 40 ° C., and withdrawn from the coagulation bath at a coagulation bath outlet roller speed of 73.8 m / min. The draft ratio at this time was calculated from the spinning stock solution discharge linear speed and the coagulation bath outlet roller speed, and was 23.0. Then, after passing through a washing bath, a 60% glycerin water bath, and a drying step, the resultant was wound into a cheese shape by a winder.

The thus obtained 10400 hollow fibers having an inner diameter of 200 μm and a thickness of 15 μm were bundled and packed in a plastic case to prepare a performance evaluation module (effective membrane area 1.5 m ²⁾ having an effective length of 23 cm.

Measurement method 1. Measurement of ultrafiltration coefficient The above-prepared module was sufficiently washed with pure water, pure water adjusted to 37 ° C. was passed through a hollow fiber membrane, and the transmembrane pressure difference (TMP) 50,
Water permeability at 100, 150 and 200 mmHg was measured. The ultrafiltration coefficient in each TMP was calculated from the obtained water permeability using the following equation. UFR (ml / m ² · hr · mmHg) = Permeability × 60 / TM
The ultrafiltration coefficient of the P / membrane area module was determined as the average ultrafiltration coefficient from the slope of the regression line obtained from the TMP and the ultrafiltration coefficient at the above four points.

2. Measurement of sieving coefficient of albumin Albumin is dissolved in a phosphate buffer, and physiological saline is added to adjust the albumin concentration to 5% by weight, pH 7.4, and 37 ° C. This solution was passed through a module having a membrane area of 1.5 m ^{2 at} a flow rate of 200 ml / min and a filtration flow rate of 15 ml / min. After 15 minutes, the albumin concentrations in the inlet and outlet of the module and in the filtrate were measured using a commercially available measurement kit. The sieving coefficient (SC) of albumin was calculated by the following equation. SC = filtrate concentration / ((inlet concentration + outlet concentration) / 2)

3. Fluorescent labeling (FITC)-Determination of sieving coefficient of dextran FITC-dextran (molecular weight 20,000) was added to bovine blood prepared at a hematocrit of 30 ± 3% and a protein concentration of 6.5 ± 0.5 g / dl.
Is dissolved at a concentration of 1.9 mg / dl, and the solution is flowed at a flow rate of 200 ml / min through a module having a membrane area of 1.5 m ² . Five minutes after blood flow, blood filtration was started at a filtration rate of 15 ml / min.
After 0, 60, and 120 minutes, blood and filtrate at the entrance and exit of the module were sampled, and the concentration of FITC-dextran was measured using a fluorescence spectrophotometer. Using the obtained measured values, the sieving coefficient of dextran was calculated from the following equation. SC = filtrate concentration / ((inlet concentration + outlet concentration) / 2)

[0025] 4. Beta ₂ microglobulin (β ₂ M) sieve measured hematocrit 30 ± 3% of the factor, the protein concentration 6.5 ± 0.5 g / dl in the prepared bovine blood 200 ml / min with a membrane area of 1.5 m ² Modules Pour into 5 minutes after the start of blood flow, filtration rate 15
Start blood filtration at ml / min and sample the blood and filtrate at the entrance and exit of the module at 15, 30, 60 and 120 minutes later, and perform enzyme immunoassay (eg, Glazyme β ₂ -Microglobu
The β ₂ M concentration is measured using lin-EIA Test (manufactured by Wako Pure Chemical Industries, Ltd.) or the like. In this measurement, an appropriate amount of human-derived β ₂ M is added to bovine blood flowing through the module, and the sampled blood is centrifuged as necessary to be subjected to β ₂ M measurement. The sieving coefficient was calculated from the measured β ₂ M concentration according to the following equation. SC = filtrate concentration / ((inlet concentration + outlet concentration) / 2)

5. Measurement of Protein Concentration in Filtrate Bovine blood prepared with a hematocrit of 30 ± 3% and a protein concentration of 6.5 ± 0.5 g / dl is passed through the module at 200 ml / min, and after the start of blood filtration at a filtration rate of 15 ml / min. After 30, 60, and 120 minutes, blood and filtrate at the entrance and exit of the module were sampled, and the protein concentration was measured by a colorimetric method (Micro TP Test Wako, etc.). The amount of protein leaked during 3L water removal was calculated from the average value for 15 to 120 minutes.

Comparative Example 1 Cellulose Triacetate 17
Parts by weight, 49.8 parts by weight of N-methylpyrrolidone, and 33.2 parts by weight of triethylene glycol were dissolved by heating at 170 ° C., and further degassed under vacuum to obtain a spinning solution of cellulose triacetate. This was filtered through a sintered filter having a pore size of 20 μm to remove impurities, and then discharged at a discharge linear velocity of 1064 cm / min from the outside of a double pipe die having an outer diameter of 540 μm, and simultaneously, liquid paraffin was discharged from the inside of the die. The hollow fiber spinning solution is in the air
After passing through 25 mm for 0.14 seconds, it was led to a coagulation bath at 55 ° C. consisting of N-methylpyrrolidone / triethylene glycol / water = 18/12/70, and was withdrawn from the coagulation bath at 73.8 m / min as in Example 1. . The draft ratio in this case was 7.0. Then, after passing through a washing bath, a 60% glycerin water bath, and a drying step, the resultant was wound into a cheese shape by a winder.

Example 2 Cellulose triacetate 1
7.5 parts by weight, 66.0 parts by weight of N-methylpyrrolidone and 16.5 parts by weight of triethylene glycol were dissolved by heating at 170 ° C.
The mixture was further degassed under vacuum to obtain a spinning solution of cellulose triacetate. This was filtered through a sintered filter having a pore diameter of 20 μm to remove impurities, and then discharged at a discharge linear velocity of 364 cm / min from the outside of a double pipe die having an outer diameter of 1200 μm, and simultaneously, liquid paraffin was discharged from the inside of the die. The hollow fiber spinning solution passes through 60 mm in the air for 0.99 seconds, and then is N-methylpyrrolidone /
36 ℃ consisting of triethylene glycol / water = 40/10/50
, And withdrawn from the coagulation bath at 73.8 m / min as in Example 1. The draft ratio at this time was 20.6. Then, after passing through a washing bath, a 60% glycerin water bath, and a drying step, the resultant was wound into a cheese shape by a winder.

[Comparative Example 2] Using a commercially available module (manufactured by Fresenius Co., product name: F60, membrane area: 1.25 m ² ), the performance was similarly evaluated and compared.

[Table 1]

[0030]

As is clear from the above description, according to the present invention, excellent elimination of dialysis complication-inducing substances and removal of substances having a molecular weight of about 20,000, which are said to have an effect of improving clinical symptoms, Further, a hollow fiber membrane for blood purification having a sharp cut-off property with less albumin leakage can be obtained.

 ──────────────────────────────────────────────────続 き Continued on the front page F term (reference) 4D006 HA01 HA95 MA01 MB02 MB05 MB06 MC18 MC18X NA04 NA27 NA28 NA29 NA61 NA64 PA05 PB09 PB52 PC44 4F071 AA09 AA34 AA64 AH02 BA02 BB06 BC05 4L035 AA09 BB04 BB11 BB17 BB22 DD01

Claims (1)

[Claims] 1. A method in which bovine blood having a hematocrit of 30 ± 3% and a protein concentration of 6.5 ± 0.5 g / dl is passed through a module having a membrane area of 1.5 m ^{2 at} a flow rate of 200 ml / min, and blood filtration is performed at a filtration flow rate of 15 ml / min. The protein concentration in the filtrate after 15 minutes of 200 mg / dl or more
1000 mg / dl or less, the protein concentration in the filtrate after 120 minutes is 50 mg
A hollow fiber membrane for blood purification characterized by being at least / dl and at most 200 mg / dl.