JPH0199609A - Reformed regenerated cellulose membrane and production thereof - Google Patents

Abstract

PURPOSE:To improve the affinity of a regenerated cellulose membrane for blood without deteriorating the dialyzing performance by bonding ester of aliphat. carboxylic acid anhydride to the surface of the membrane brought into contact with blood. CONSTITUTION:Aliphat. carboxylic acid anhydride such as caproic anhydride and an esterification catalyst such as 4-dimethylaminopyridine are dissolved in a reaction medium such as a solvent mixture of 1,1,2-trichloro-1,2,2- trifluoroethane with acetone to prepare a treating soln. A membrane of hollow regenerated cellulose yarn is immersed in the treating soln. and an esterification reaction is carried out. After the reaction, the treated membrane is washed by immersion in methanol or other method and dried to obtain a polymer membrane of regenerated cellulose having an esterified surface.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a modified regenerated cellulose membrane used for artificial organs, etc., and a method for producing the same. More specifically, the present invention relates to a regenerated cellulose membrane with improved blood compatibility and a method for producing the same.

[Conventional technology]

In recent years, artificial organs using membranes, such as artificial kidneys, artificial lungs, and plasma separation devices, have made great progress. As is well known, especially in artificial dialysis therapy, regenerated cellulose membranes, especially copper ammonium regenerated cellulose membranes, are widely used, and along with advances in dialysis equipment and dialysis technology, they play a major role in prolonging the lives of renal failure patients and reintegrating them into society. is fulfilled. this is,
This is because regenerated cellulose membranes have excellent dialysis performance and mechanical strength, as well as high safety backed by many years of experience.

However, despite advances in dialysis therapy, various problems associated with dialysis still remain unsolved. for example,
There are concerns about the various side effects that may occur due to long-term administration of large doses of anticoagulants, as well as the temporary decrease in white blood cells caused by hemodialysis using regenerated cell giant membranes and some other membranes. Problems with activation of complement components have been pointed out.

Regarding the latter phenomenon, although the relationship with clinical symptoms or clinical significance is not clear, it is desired to alleviate these phenomena without impairing the other excellent performance of the regenerated cellulose membrane.

To solve these problems and phenomena, membranes made of synthetic polymers can
Although it has been proposed that these membranes have relatively minor aspects, the mechanical strength of these membranes is weak and pinholes are likely to occur, the sterilization method is limited due to insufficient heat resistance, and the balance of performance, That is, there is a drawback that the balance between the amount of water permeated and the amount of material permeated is poor, making it difficult to specify how to use it.

On the other hand, various methods have been proposed for modifying the blood affinity of regenerated cellulose membranes. For example, a method of imparting antithrombotic properties by heparinizing the membrane surface has been published in Jikai 51-194.
However, it has not been put into practical use because sufficient effects cannot be obtained and the cost is relatively high. Also,
Methods of coating the surface of regenerated cellulose membranes with various polymers and vitamins have also been proposed, but there are problems such as the stability of the coating and limitations on sterilization methods. Also,
JP-A No. 61-8105 discloses a method of reacting an isocyanate prepolymer with a regenerated cellulose membrane.
0-118203 proposes a method of chemically bonding polymeric acids via a bridging agent, but there are problems such as stability of reactants and complexity of the reaction process.

Furthermore, although a dialysis membrane made using modified cellulose such as diethylaminoethyl cellulose has been proposed in JP-A-61-113459, it cannot be said that the improvement in reducing blood coagulation is sufficient.

[Problem that the invention seeks to solve]

As mentioned above, attempts to improve the blood affinity of regenerated cellulose membranes have advantages and disadvantages. Therefore, an object of the present invention is to provide a modified regenerated cellulose membrane that has improved blood affinity without impairing the excellent dialysis performance of a polymer membrane made of regenerated cellulose, and a method for producing the same. .

Means and Actions for Solving the Problems It is believed that the hydroxyl groups on the membrane surface are involved in the activation of complement components and the temporary decrease in white blood cells that occur when a regenerated cellulose membrane is used. On the other hand, the hydroxyl groups on the surface of this membrane can react with various functional groups to bond molecular chains. The bound molecular chains mask the hydroxyl groups on the membrane, preventing direct contact between the hydroxyl groups and complement proteins and blood cells. This not only suppresses the activation of complement components, but also affects the physicochemical properties of the membrane surface and improves other blood affinities. Although many combinations of molecular chain structures and functional groups are possible, we have completed the present invention after conducting various studies in consideration of biosafety, biocompatibility, economic efficiency, chemical reactivity, etc. It was. That is, the present invention provides a modified regenerated cellulose membrane characterized in that an aliphatic carboxylic anhydride is ester bonded to at least the surface of the regenerated cellulose membrane that comes into contact with blood. A modified regenerated cellulose membrane characterized in that an esterification reaction with an aliphatic carboxylic acid anhydride is carried out by treating the regenerated cellulose membrane with a solution in which a substance and an esterification catalyst are dissolved or dispersed in a reaction medium. A manufacturing method is provided.

The "regenerated cellulose" used in the present invention is natural cellulose that has been chemically or physically changed and then regenerated. However, copper ammonium regenerated cellulose is preferably used due to its dialysis performance and high safety backed by many years of experience.

The regenerated cellulose may be formed into any shape such as a flat membrane or a hollow fiber membrane, but a hollow fiber membrane is preferred. For example, as disclosed in Japanese Patent Publication No. 50-40168 and Japanese Unexamined Patent Publication No. 59-204912, the film thickness is from several μ to 60 μ and the outer diameter is from 10 μ to several hundred μ. A hollow fiber membrane having a surface or the like is used.

In the present invention, an aliphatic carboxylic acid anhydride is ester bonded to the above-mentioned regenerated cellulose membrane to modify the acid membrane. Examples of such aliphatic carboxylic acids include aliphatic carboxylic acids such as saturated or unsaturated fatty acids and aliphatic dicarboxylic acids. From the masking effect of hydroxyl groups on the film, the aliphatic carboxylic acids preferably have 5 or more carbon atoms, such as valeric acid, caproic acid, enanthic acid, caprylic acid, pelargonic acid, capric acid, undecylic acid, lauric acid, and tridecyl. Acids, saturated fatty acids such as myristic acid, pentadecylic acid, palmitic acid, heptadecylic acid, stearic acid, nonadecanoic acid, arachidic acid, behenic acid, lignoceric acid, oleic acid, elaidic acid, cetoleic acid, erucic acid, brassic acid, sorbic acid , unsaturated fatty acids such as linoleic acid, linoleic acid, and arachidonic acid, and aliphatic dicarboxylic acids such as glutaric acid, adipic acid, pimelic acid, superric acid, azelaic acid, and sebacic acid.

Such aliphatic carboxylic acids have low toxicity and are metabolized within the body, so they do not accumulate. Therefore, it is highly safe even if unreacted substances attached to the membrane are eluted or ester bonds are cleaved by some operation and mixed into blood.

The molecular chain referred to in the present invention is an organic compound in which at least i is chemically bonded to the membrane surface, and in the present invention, it corresponds to an aliphatic carboxylic acid residue having an ester bond. In addition, as mentioned above, the number of carboxyl groups and acid derivative groups serving as functional groups is not limited to just one, but in the case of polyfunctional aliphatic carboxylic acids, before reacting with the hydroxyl groups on the membrane surface, In addition, polymerization of carboxylic acids may progress due to reactions between carboxylic acids, resulting in a decrease in esterification reactivity. In addition, in the case of polyfunctional carboxylic acids, there is a possibility of forming a loop-shaped molecular chain bonded to the surface at three or more places, but as will be explained later, it is better for the molecular chain to have one end bonded to the surface. Preferably, monocarboxylic acids are used.

These carboxylic acids are ester bonded to the surface of the regenerated cellulose membrane using carboxylic anhydrides.

Ester bonding to the surface of the regenerated cellulose membrane is performed by an esterification reaction with hydroxyl groups present on the membrane surface, and a known reaction between a low-molecular alcohol and a low-molecular carboxylic acid anhydride can be applied. As for the treatment conditions, it is preferable to keep the treatment temperature low and the treatment time as short as possible so as not to affect the physical properties of the regenerated cellulose membrane. These matters are advantageous from an economic point of view, and it is preferable to use an esterification catalyst to promote esterification.

Examples of the esterification catalyst that promotes the reaction include sulfuric acid, p-toluenesulfonic acid, zinc chloride, sodium acetate, pyridine, 4-dimethylaminopyridine, and 4-pyrrolidinepyridine. In the present invention, these catalysts can be used alone or in appropriate combinations, but from the viewpoint of smooth reaction and removal after the reaction, it is preferable to use as little as possible of a catalyst that is soluble in the reaction medium.

From this point of view, a method of esterifying a carboxylic acid anhydride with 4-dimethylaminopyridine and/or 4-pyrrolidinopyridine is preferably used, and does not generate a precipitate. That is, if there is a precipitate trapped in the membrane pores, it may cause a decrease in dialysis performance or may be mixed into blood when used as an artificial organ, which is not preferable. Further, after treatment, a filtration operation is normally carried out for sterilization, but the precipitate makes this operation difficult.

The reaction medium must not react with the aliphatic carboxylic acid anhydride, do not deactivate the esterification catalyst, and do not cause any major morphological changes in the polymer membrane made of regenerated cellulose membrane.

Therefore, any solvent that satisfies the above requirements and that can disperse or dissolve the aliphatic carboxylic acid anhydride and the esterification catalyst can be used as the reaction medium. A solvent that dissolves the aliphatic carboxylic acid anhydride and the esterification catalyst is preferred from the viewpoint of reaction uniformity, smoothness, and post-reaction removal. Examples of such a reaction medium include n-hexane, n-hebutane, and cyclohexane. , hydrocarbons such as petroleum ether, petroleum benzine, benzene and toluene, ketones such as acetone and methyl ethyl ketone, esters such as methyl acetate, ethyl acetate and propyl acetate, ethers such as ethyl ether, isopropyl ether and dioxane, l , 1.2-
1-dichloro-1,2,2-trifluoroethane, trichlorofluoromethane, ■.

Examples include chlorofluorinated hydrocarbons such as 1.2.2-tetrachloro-1,2-difluoroethane. These reaction media can be used alone or in mixtures. From the viewpoint of biological safety and post-reaction removal, chlorinated fluorinated hydrocarbons, especially 1
, 1.2-trichloro-1,2,2-)trifluoroethane is preferred, and a mixed solvent of 1.1.2-)lichloro-1.2゜2-trifluoroethane and acetone is preferred. It is used in

There are various methods for treating regenerated cellulose membranes. That is, a method in which a regenerated cellulose membrane is added to and stirred in a treatment solution in which an aliphatic carboxylic acid anhydride and an esterification catalyst are dispersed or dissolved in a reaction medium, and a polymer membrane is immersed in an immersion tank filled with the treatment solution. Alternatively, a method may be adopted in which the processing solution is circulated through a processing tank filled with a polymer membrane. Furthermore, after assembling a polymer membrane made of regenerated cellulose into a dialyzer or the like, it is naturally possible to adopt a method in which a treatment liquid is circulated or filled at least on the side through which blood flows and left to stand.

After the esterification reaction is completed, the regenerated cellulose membrane is separated from the processing solution and is omitted if no reaction reagents, esterification catalysts, or side reaction products remain in the membrane, but washing is usually performed to remove these. be exposed. In this washing operation, immersion extraction or Soxhlet extraction is performed using the solvent used in the reaction or a solvent that does not cause a major change in the form of the regenerated cellulose membrane, such as methyl alcohol or ethyl alcohol. Finally, residual solvent is removed by vacuum drying, blow drying, or the like.

A polymer membrane made of regenerated cellulose whose membrane surface has been esterified in this manner has the ability to activate complement components without impairing the excellent dialysis performance of the polymer membrane used, as shown in the examples. suppressed, and the transient decrease in white blood cells becomes slight. This effect is thought to be due to the fact that in the present invention, the esterification reaction occurs only on the surface of the polymer membrane, and the chemical and physical structure inside the membrane is maintained. In addition, the amount of esterification on the surface is sufficient to improve the physicochemical and biochemical properties of the surface, but is so small that it does not adversely affect the permeation of water or substances. Conceivable.

The effects of improving the physicochemical and biochemical properties of the membrane surface can also be noted on other blood affinities. That is, in the case of a hydrophobic molecular chain in which a fatty acid is ester bonded, albumin among plasma proteins is selectively adsorbed. Albumin functions as a carrier of fatty acids in the blood and is said to have a hydrophobic pocket at the center of its molecular axis. It is thought that selective adsorption occurs because hydrophobic molecular chains bind to this pocket. It is thought that blood coagulation is unlikely to occur on blood contact surfaces where albumin is selectively adsorbed in this manner. The rationale for this is that proteins with sugar chains such as fibrinogen and immunoglobulin bind to platelets via these sugar chains, but albumin does not have such sugar chains and has a unique bond with platelets. Since no binding occurs, it is thought that blood coagulation is unlikely to occur on blood contact surfaces that preferentially adsorb albumin from blood.

For the selective adsorption of albumin as described above, the molecular chains are bound to the polymer membrane surface at three or more places, and rather than the state where chain movement is suppressed, one end is bound and the other end can move freely. That's preferable. This is thought to be because free molecular chains shield the real surface of the membrane, suppressing adsorption of other proteins on the real surface. The same effect also prevents the direct contact of complement proteins with the regenerated cellulose membrane, suppressing their activation.

Although sterilization is required before use for treatment, the regenerated cellulose membrane of the present invention can be sterilized using various sterilization methods. That is, the incorporated dialyzer can be sterilized in a dry state, ethylene oxide gas sterilization, high-pressure steam sterilization, gamma ray sterilization, etc., or the incorporated dialyzer can be sterilized with water or physiological saline, etc. Sterilization, high pressure steam sterilization, gamma ray sterilization, etc. can be used.

Such sterilization procedures do not alter the improved hemocompatibility.

Next, the content of the present invention will be described in more detail with reference to Examples.

Note that the measurement items described in the following examples were measured by the following methods.

(1) Water permeability: Make a module by fixing both ends of a bundle of 100 hollow fibers with adhesive, fill the hollow part with water, close one end,
Water is poured through the opening while applying a pressure of 200 mmHg, and the amount of water permeation per unit time is measured. The membrane area of the hollow fiber is calculated by measuring the inner diameter and the effective length of the module.

(2) Make a module similar to Clearance (1), and use 110 ml instead of water.
Using a 00pp urea aqueous solution or a 1100pp vitamin B-1''2 (VBI□) aqueous solution, determine the concentration in the dialysate from the absorbance in the same manner as in (1), and calculate the clearance using the following formula. .

Clearance = (concentration in dialysate) x (volume of dialysate per minute) (3
) Complement consumption rate After adding a regenerated cellulose membrane to a surface area of 80 cIll per serum ITII+ and shaking at 37°C for 1 hour, the remaining complement in the serum was determined by the method of Mayer et al. (εx
peripheral immunochemistry
try+ p 1 3 3.

Thomas, 1961), the hemolytic complement value was determined as 50%, and the decrease from the control was expressed as the complement consumption rate.

(4) EIA (Enzyme Immunoassay) Method Fill the hollow fiber with rabbit plasma and incubate at 37°C for 1 hour. Afterwards, extrude the rabbit blood and add PBS.
Wash several times with buffer. Peroxidase-labeled antibodies (manufactured by Capel) against albumin, immunoglobulin G (IgG), and fibrinogen were filled into the samples with plasma adsorbed on the inner surface of the hollow fibers.
Antigen-antibody reaction occurs with the adsorbed protein. After thorough washing with PBS buffer, the hollow fibers are cut into pieces of 2 mm length and placed in a polyethylene tube. 3-(p-hydroxyphenyl)propionic acid, which is a substrate for peroxidase, and aqueous hydrogen peroxide are added to this polyethylene tube, the enzymatic reaction is allowed to proceed for 1 hour, and the produced oxide is measured by fluorescence spectroscopy.

Example 1 1.1.2-Trichloro-1,2,2-trifluoroethane-acetone mixed solvent (acetone 12.5 wt%) 2
0.047 g of caproic anhydride and 0.01 g of 4-dimethylaminopyridine were added to 50 ml to prepare a treatment liquid. This treatment solution was added to a regenerated cellulose hollow fiber membrane (inner diameter 2
00μm, film thickness 13μm, length approximately 20an) to approximately 600μm
The books were soaked vertically for 2 hours with occasional up and down movements. The treated hollow fiber membrane was immersed in methanol overnight and then dried under reduced pressure at room temperature to obtain a regenerated cellulose hollow fiber membrane. Table 1 shows the results of the complement consumption rate of the hollow fiber membranes obtained.

Example 2 Esterification was carried out in the same manner as in Example 1 except that various aliphatic carboxylic acid anhydrides were used instead of caproic anhydride,
Various regenerated cellulose hollow fiber membranes were obtained. Table 1 shows the aliphatic carboxylic acid anhydrides used, their usage amounts, and the results of the complement consumption rate of the esterified regenerated cellulose hollow fiber membrane.

Table 1 Example 3 EIA for regenerated cellulose hollow fiber membranes of Examples 1 and 2
The method measurements were carried out. The results are shown in Table 2. That is,
Fluorescence intensity 1a when using anti-albumin antibody, fluorescence intensity It when using anti-immunoglobulin G antibody,
Fluorescence intensity If when using anti-fibrinogen antibody,
Then, the value of I a / I i and I a /
The IfO value was divided by the value for the untreated hollow fiber membrane and expressed as (Alb/IgG) and (Alb/Fib), respectively. The value thus obtained is greater than 1.00, indicating that these hollow fiber membranes adsorb albumin more selectively than untreated hollow fiber membranes. (Margins below) Table 2 Example 4 0.44 g of caproic anhydride, 0.02 g of 4-dimethylaminopyridine, and 1.2 g of 1,1.2-trichloro-1°2.
A treatment solution was prepared by adding 700 ml of a 2-trifluoroethane-acetone mixed solvent (acetone 12.5 wt%).

This treatment solution was added to a regenerated cellulose hollow fiber membrane (inner diameter 200 μm).
, film thickness 13 μm, length 30 cm) (approximately 7,00 pieces)
0) was immersed vertically for 30 minutes with occasional up and down movement.

The treated regenerated cellulose hollow fiber membrane bundle was immersed in methyl alcohol for a day and night, and then dried under reduced pressure at room temperature to obtain an esterified hollow fiber membrane bundle.

Table 3 shows the measurement results of the dialysis performance and complement consumption rate of the hollow fiber membranes obtained.

Next, this hollow fiber membrane was installed in a dialyzer, and extracorporeal circulation was performed using a dog. The dog used was a peagle-sized dog weighing approximately 10 kg.
Blood flow at a rate of 100 ml/min was taken from a shunt created in the neck and flowed to the blood side of the dialyzer. Prior to extracorporeal circulation, after washing the inside of the dialyzer with physiological saline, heparin 6.
The inside of the dialyzer and blood circuit were filled with physiological saline containing 0 OOU/L, and then blood was allowed to flow. Blood was collected at the inlet of the dialyzer and the number of white blood cells was measured. White blood cell count just before dialysis to 10
When set to 0, the values 15 minutes and 30 minutes after dialysis were 78 and 82, respectively.

Table 3 Reference Example Table 3 shows the measurement results of dialysis performance and complement consumption rate for untreated regenerated cellulose hollow fiber membranes.

Next, when extracorporeal circulation was performed using a dog in the same manner as in Example 4, it was found that when the white blood cell count immediately before dialysis was 100, the number of white blood cells after dialysis was 15.
The minute and 30 minute values were 13 and 45, respectively.

Example 5 In a 200-mm Erlenmeyer flask with a stopper, 35 ml of caproic anhydride was added.
■, 4-dimethylaminopyridine 4 Akebono, 1.1.2-
100 ml of trichloro-1,2,2-trifluoroethane-acetone mixed solvent (acetone 12.5 wt%) was added to prepare a treatment liquid. After leaving it at room temperature for 2 hours, 2-3
4.5 g of a regenerated cellulose hollow fiber membrane (membrane thickness: 13 μm, inner diameter: 200 μm) cut into pieces of m/m length was added to the treatment solution, the membrane was stoppered, and the membrane was shaken in an aqueous solution at 30° C. for 30 minutes.

Thereafter, the hollow fiber membrane was taken out and immersed in methyl alcohol for a day and night, then filtered off and dried under reduced pressure at room temperature. In the same manner, treatment solutions that had been left at room temperature for 4, 6, and 8.16 hours after preparation were also tested to obtain hollow fiber membranes, respectively.

The results of measuring the complement consumption rate are shown in Table 4, and the reactivity of the treatment solution did not change even after being left for 16 hours, showing the same complement consumption rate as after 2 hours.

Table 4: Leaving time of treatment solution Complement consumption rate 2
14% 4 14% 6 12% 8 13% 16 14% [Effects of the invention] As is clear from the above explanation, the superiority of the regenerated cellulose membrane can be improved by ester bonding the aliphatic carboxylic acid anhydride to the regenerated cellulose membrane. While maintaining the dialysis performance,
The activation of complement components is suppressed and the transient decrease in white blood cells is alleviated. In addition, albumin is selectively adsorbed and compatibility with blood is improved.

Patent applicant: Asahi Kasei Industries, Ltd.

Claims (2)

[Claims] (1) A modified regenerated cellulose membrane characterized in that an aliphatic carboxylic acid anhydride is ester-bonded to at least the surface of the regenerated cellulose membrane that comes into contact with blood. (2) By treating the regenerated cellulose membrane with a solution in which an aliphatic carboxylic acid anhydride and an esterification catalyst are dissolved or dispersed in a reaction medium, the esterification reaction between the aliphatic carboxylic anhydride and the hydroxyl groups on the membrane surface is carried out. A method for producing a modified regenerated cellulose membrane, characterized by carrying out