JPH0556175B2 - - Google Patents

Description

[Detailed description of the invention]

[Industrial Field of Application] The present invention relates to an improved regenerated cellulose-based dialysis membrane used in artificial dialysis therapy and the like. More specifically, the present invention relates to a regenerated cellulose-based dialysis membrane with improved compatibility with blood. [Prior art] In artificial dialysis therapy, regenerated cellulose-based dialysis membranes, especially copper ammonium method regenerated cellulose-based dialysis membranes, are widely used, and with advances in dialysis equipment and dialysis technology, they have been used to prolong the lives of renal failure patients and help them return to work. plays a major role in However, despite advances in dialysis therapy, various problems associated with dialysis still remain unsolved. For example, anticoagulants are administered in large doses over a long period of time,
As a result, there are various side effects that are thought to occur, as well as issues such as transient leukopenia and activation of complement components when performing hemodialysis with regenerated cellulose dialysis membranes and some other membranes. has been pointed out. Regarding the latter phenomenon, the relationship with clinical symptoms,
Alternatively, although the clinical significance is not clear, it is desired to alleviate these phenomena without impairing the other excellent performance of the regenerated cellulose-based dialysis membrane. In response to such problems and phenomena, various methods have been proposed to improve the blood compatibility of regenerated cellulose-based dialysis membranes. For example, a method for imparting antithrombotic properties by heparinizing the membrane surface was disclosed in Japanese Patent Application Laid-open No. 51-194.
However, it has not been put into practical use because it is not sufficiently effective and the cost is relatively high.
Additionally, methods have been proposed in which various polymers and vitamins are coated on the surface of regenerated cellulose-based dialysis membranes, but these methods have problems such as the stability of the coating and limited sterilization methods. Also, JP-A-61-8105
A method of reacting an isocyanate prepolymer with a regenerated cellulose-based dialysis membrane was disclosed in Japanese Patent Application Laid-Open No. 118203/1983.
A method of chemically bonding a polymeric acid via a bridging agent has been proposed, but there are problems such as stability of reactants and complexity of the reaction process. Further, although a dialysis membrane formed using modified cellulose such as diethylaminoethyl cellulose has been proposed in Japanese Patent Application Laid-open No. 113459/1989, the improvement in reducing blood coagulation is not sufficient. [Problems to be Solved by the Invention] As described above, attempts to improve blood compatibility of regenerated cellulose membranes have advantages and disadvantages. Therefore, an object of the present invention is to provide an improved regenerated cellulose-based dialysis membrane with improved blood compatibility. [Means for Solving the Problems] Hydroxyl groups on the membrane surface are thought to be involved in the activation of complement components and the transient decrease in white blood cells that occur when a regenerated cellulose dialysis 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. It is believed that the bound molecular chains mask the hydroxyl groups on the membrane surface, preventing direct contact between the hydroxyl groups and complement proteins and blood cells, and improving compatibility with blood. Based on this idea, improved regenerated cellulose-based dialysis membranes have been proposed. The present inventors have completed the present invention as a result of intensive research on the amount of grafting that produces an improvement effect. That is, in the present invention, in the regenerated cellulose-based dialysis membrane, at least _the surface of the membrane in contact with blood contains 0.1 mg or more of the formula HO ₂ CCH ² −(OCH ₂ CH ₂ ) _o −OR (n = 1 to 150; R = saturated or unsaturated hydrocarbon having 1 to 20 carbon atoms. A dialysis membrane is provided. In this specification, a "graft chain" is a molecular chain with at least one end chemically bonded to the membrane surface,
In the present invention, the ester-bonded acyl residue of polyethylene glycol monocarboxylic acid corresponds to this, and the "grafting amount" refers to the amount of ester-bonded polyethylene glycol monocarboxylic acid. 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 preferable. For example,
-40168 and JP-A No. 59-204912, the film thickness is several μm to 60 μm and the outer diameter is
A hollow fiber membrane or the like having a perfectly circular cross section of 10 μm to several hundred μm is used. The grafting of the polyethylene glycol monocarboxylic acid (hereinafter referred to as polymeric carboxylic acid in some cases) used in the present invention onto the surface of the regenerated cellulose-based dialysis membrane is carried out by an esterification reaction with the hydroxyl groups present on the membrane surface. Therefore, a known reaction between a low-molecular alcohol and a low-molecular carboxylic acid or an acid derivative thereof can be applied. For example, a mixed catalyst of dicyclohexylcarbodiimide and 4-dimethylaminopyridine and/or 4-pyrrolidinopyridine is used as an esterification catalyst to accelerate the reaction, and these and a polymeric carboxylic acid or its acid derivative are dispersed or By treating the regenerated cellulose-based dialysis membrane with the dissolved treatment solution, the esterification reaction progresses and grafting of the polymeric carboxylic acid takes place. Therefore, the amount of grafting varies depending on the treatment conditions, such as the carboxylic acid concentration and catalyst concentration in the treatment liquid, reaction time, and reaction temperature. When the modified regenerated cellulose-based dialysis membrane is extracted with an aqueous alkaline solution, the ester bonds are hydrolyzed and the polymeric carboxylic acid grafted onto the membrane is extracted. By analyzing this, the amount of grafting on the membrane surface can be determined. In addition, since the polymeric carboxylic acid that is simply attached is extracted with water, the presence or absence of the polymeric carboxylic acid that is attached to the surface of the modified regenerated cellulose dialysis membrane can be determined by analyzing the water extract. Easy to identify. As mentioned above, the hydroxyl groups on the membrane surface are involved in the activation of complement components and the temporary decrease in white blood cells in the regenerated cellulose membrane. As shown in Reference Example 1, changes in the physicochemical properties of the membrane surface, such as zeta potential and hydrophilicity, are observed from a very small amount of grafting, but the activation effect of complement components is not sufficiently inhibited. . On the contrary, in the hollow fiber membrane of Example 5, which has a large amount of grafting, its hydrophilicity is at the same level as that of the untreated hollow fiber, but the activation effect of complement components is sufficiently suppressed. Therefore, in order to achieve the purpose of the present invention, it is necessary that the hydroxyl groups on the membrane surface involved in biological reactions be shielded by the grafted polymeric carboxylic acid, rather than changing the physicochemical properties of the membrane surface. It is. In addition, changes in the physicochemical properties of the membrane surface may have an effect on the regenerated cellulose membrane and other properties, such as the membrane's water leakage and substance permeability, as shown in Examples 1 to 5. As shown, the changes in the physicochemical properties of the membrane surface due to grafting are not large enough to affect other properties of the membrane. It is clear from the Examples described below that in order to achieve the object of the present invention, the amount of grafted polymeric carboxylic acid should be adjusted to a membrane area of 1 m ²
Must be 0.1mg or more per 0.2mg
It is more preferable that it is above. Sterilization is required before use for treatment, but
The regenerated cellulose-based dialysis 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 after being filled with water or physiological saline. ,
High-pressure steam sterilization or gamma ray sterilization can be used. Such sterilization procedures do not alter the improved hemocompatibility. [Example] 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) Complement consumption rate A sample hollow fiber cut into pieces of approximately 2 mm length was placed in a polyethylene tube, and 200 μ of guinea pig complement (Cordis Rapo) diluted 4 times with gelatin veronal buffer was added thereto. The mixture was incubated at 37°C for 1 hour with stirring, and the complement value of the supernatant was measured. Complement values are determined by Mayer's modified method: Experimental Immunochemistry, 2nd edition,
Page 133, C.C. Thomas (CC
Thomas) Publishers, 1961, Reference). That is, determine the 50% hemolytic value (CH50 value) of complement, and calculate the complement consumption rate (%) relative to the control.
was calculated. (2) Capillary rise value A sample hollow fiber was immersed in water at 25°C in an almost vertical position, and the rise in the liquid level inside the hollow fiber due to capillary action was measured based on the external water level.
In principle, the more hydrophilic the membrane surface is, the higher the liquid level will be due to capillary rise, and the larger the value will be. (3) Zeta potential A potassium chloride solution of 1 mmol/liter is passed through one side of the sample hollow fiber under pressure (P), and the potential difference (E) generated at both ends of the hollow fiber is measured using a platinum electrode. The potential difference change (ΔE) corresponding to the pressure change (ΔP) was determined, and the zeta potential was calculated from the following formula. Zeta potential = 4πηk/D/(ΔE)/(ΔP) where η, k, and D represent the viscosity, specific electrical conductivity, and dielectric constant of the potassium chloride solution, respectively. (4) Amount of grafting Cut the sample hollow fiber into small pieces, put it in an Erlenmeyer flask,
Water was added to this, and the mixture was shaken at 37°C for 1 hour to extract the attached polymeric carboxylic acid with water. After separating only half of this aqueous extract, an aqueous sodium hydroxide solution was added to the sample hollow fiber Erlenmeyer flask, and the mixture was heated to 50°C.
The mixture was shaken for 2 hours. The alkaline extract thus obtained was separated and neutralized with hydrochloric acid. After freeze-drying the aqueous extract and alkaline extract, respectively, the residue was redissolved in 1,4-dioxane, and 9
-Anthryl diazomethane (Funakoshi Pharmaceuticals)
was added to the reaction, and analyzed by high performance liquid chromatography equipped with a fluorescence detector. The amount of grafted polymeric carboxylic acid was calculated by subtracting the analytical value of the aqueous extract from the analytical value of the alkaline extract. Example 1 A bundle (approximately 9000 membranes) of regenerated cellulose hollow fiber membranes (inner diameter 180 μm, membrane thickness μm, length 24 cm) was packed into a stainless steel tube equipped with nozzles on the top and bottom.
Also, in a 1000 ml glass bottle, 0.28 alkoxypolyethylene glycol monocarboxylic acid (HO ₂ CCH ₂ −(OCH ₂ CH ₂ ) ₇ −O−C ₁₃ H ₂₇ )
g, 4-dimethylaminopyridine (hereinafter,
0.01 g of dicyclohexylcarbodiimide (hereinafter referred to as "DCC"), and 700 ml of 1,1,2-trichloro-1,2,2-trifluoroethane-dichloromethane mixed solvent (dichloromethane 5wt%) were added. , a treatment solution was prepared. This treated solution was introduced into the stainless steel tube from the lower nozzle using a tube pump, and the effluent from the upper nozzle was returned to the flask for 20 minutes of circulation. At this time, the stainless steel tube and flask were placed in a water bath to maintain the temperature of the treatment solution at 35°C. The treated 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 improved hollow fiber membrane. Regarding hollow fiber membranes subjected to esterification treatment,
Measurements of capillary rise, zeta potential, graft volume, and complement consumption rate were performed. The results are shown in Table 1. Examples 2 to 5 Using the same alkoxypolyethylene glycol monocarboxylic acid used in Example 1 as the polymeric carboxylic acid, a treatment liquid was prepared under the following conditions.
Esterification treatment was carried out in the same manner as in Example 1,
An improved hollow fiber membrane was obtained.

[Table] For each of the obtained hollow fiber membranes, the capillary rise value, zeta potential, graft amount, and complement consumption rate were measured. The results are shown in Table 1. Reference Example 1 A treatment solution was prepared with the concentrations of polymeric carboxylic acid, DMAP, and DCC being reduced to 1/3 of that of Example 1,
Esterification treatment was carried out in the same manner as in Example 1. Capillary rise value, zeta potential, graft amount, and complement consumption rate were measured for the obtained hollow fiber membranes and untreated hollow fibers. The results are shown in Table 1. Although changes were observed in the capillary increase value, the suppression of complement activation was insufficient.

[Table] Example 6 Examples 1, 2, 5 and untreated regenerated cellulose hollow fiber membranes were incorporated into a dialyzer, and extracorporeal circulation was performed using a dog. The dog used was a beagle dog weighing approximately 10 kg, and 100 ml/ml was used from a shunt created in the neck.
The blood flow of min was collected and sent to the blood side of the dialyzer. Prior to extracorporeal circulation, the inside of the dialyzer was washed with physiological saline, and then the inside of the dialyzer and blood circuit were filled with physiological saline containing 6000 U/L of heparin, 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. When the white blood cell count just before dialysis is 100,
Table 2 shows the values 15 minutes and 30 minutes after dialysis.

〔Effect of the invention〕

The regenerated cellulose membrane of the present invention, in which 0.1 mg or more of polymeric carboxylic acid is grafted per 1 m ² of membrane area, exhibits the following remarkable effects. B. As shown in Table 1, the activation of complement components is suppressed. (b) As shown in Table 2, the transient decrease in white blood cells is significantly reduced. C. It is an economical and highly safe dialysis membrane because it is easy to manufacture and the reagents used are easy to remove.

Claims (1)

[Claims] 1. In a regenerated cellulose-based dialysis membrane, at least on the membrane surface that comes into contact with blood, per 1 m ² of membrane area,
0.1 mg or more of polyethylene glycol mono represented by the formula HO ₂ CCH ₂ -(OCH ₂ CH ₂ ) _o -OR (n = 1 to 150; R = saturated or unsaturated hydrocarbon having 1 to 20 carbon atoms) A regenerated cellulose-based dialysis membrane characterized by grafting acyl residues of carboxylic acids through ester bonds.