JPS61176359A - Serum separation membrane - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Field of Application] The present invention relates to a novel plasma separation membrane with excellent plasma compatibility.

[Conventional technology]

゛Plasma separation is the separation of plasma, a liquid component, from blood, and is now mainly used as plasma exchange therapy for several intractable diseases, including autoimmune diseases. .

It is also expected to be used as a method for collecting plasma from healthy people, which is the raw material for plasma fraction preparations for which demand for the treatment of various diseases is rapidly increasing.

Conventionally, this plasma separation has been performed using a centrifugal separation method that utilizes the difference in specific gravity.
A continuous centrifuge using extracorporeal circulation has also been developed for the purpose of continuous separation of platelets and the like. On the other hand, compared to centrifugation, plasma separation using a porous membrane with an average pore diameter of about 0.1 to 1 μm does not require expensive equipment, is easy to operate, can separate a large amount of plasma in a short time, and does not contain platelets. It is rapidly becoming popular due to its characteristics.

In the case of a plasma separation membrane, it is desired that plasma proteins such as albumin and globulin permeate at a high permeability, but that red blood cells, white blood cells, and platelets do not pass through at all, and that the plasma separation rate is high without causing hemolysis.

Plasma separation rate is determined by blood hematocrit value, protein concentration,
It is affected by blood flow rate, filtration pressure, etc., but considering clinical use, when blood flow is 100a + β / + stn, 30
~60ml/+*in is required.

For this purpose, an albumin permeation rate of 90% or more, preferably substantially complete permeation, and a water permeation rate measured with water of 2 to 60j! /hm·mmHg, preferably 4 to 30 /! /hm・mmHg performance is required.

Incidentally, in blood purification using such extracorporeal circulation, it is generally necessary to use an anticoagulant such as heparin or sodium citrate to prevent thrombus formation within the circuit or module.

Since artificial dialysis has a relatively long history and many chronic diseases are treated, its usage is almost established. However, since plasma exchange therapy using separation membranes has a short history and targets a wide variety of diseases, the selection of anticoagulants and the amount to be used have not yet been fully established. This has become a major clinical problem. Particularly in the case of liver disease in which hematopoietic function is reduced, the amount and activity of endogenous coagulation factors are low, so incorrect use of anticoagulants may lead to major bleeding. Therefore, reducing the amount of anticoagulants used is said to be a major issue in applying plasma exchange therapy to this disease. Furthermore, in the case of plasma collection from healthy individuals, it is desirable to use as little anticoagulant as possible in order not to affect the normal blood coagulation function.

In order to further develop plasma separation using membranes, it is necessary to be able to perform extracorporeal circulation safely even when the amount of anticoagulant used is reduced.

These characteristics are problems not only with the membrane material but also with the entire separation system including circuits and modules, but plasma separation membranes in particular are porous and have a large contact area with blood, so they have a considerable impact. .

[Problem that the invention seeks to solve]

Currently, there are many types of known materials used as plasma separation membranes, but none of them have yet reached the stage where they fully satisfy the above characteristics. The present invention aims to solve these problems and provide a plasma separation membrane with excellent blood compatibility.

c.Means for solving problems] The above objects are achieved by the invention described below.

That is, the present invention provides a monomer (
This is a plasma separation membrane made of a copolymer of I) and acrylonitrile (n).

The plasma separation membrane of the present invention can be produced by forming a membrane using a solution prepared by dissolving the above-mentioned copolymer in a solvent containing preferably dimethyl sulfoxide as a main component.

The copolymer of components (1) and (II) of the present invention can take any desired copolymerization form.

Examples include random copolymers of (I) and (II), and those obtained by grafting or block copolymerizing (1) onto a polymer of component (n).

Component (I) includes, for example, acrylic acid or methacrylic acid esters represented by the general formula (1)% (1), or vinyl monomers represented by the general formula (2).

The manufacturing method of these addition-polymerizable compounds is known. For example, in (1), the compound with R, -R2=CH2 is an ester of one-terminated methoxypolyethylene glycol and methyl methacrylate obtained by adding ethylene oxide to methanol. It can be obtained by exchange reaction.

In addition, by anionically polymerizing ethylene oxide using diphenylmethylpotassium as an initiator and stopping the reaction with methacrylic acid chloride, R+ = CH3, Rz =
A compound of CHΦ2 is obtained. The degree of polymerization n of the polyethylene oxide in (I) can be determined by measuring the molecular weight of the compound by gel permeation chromatography or the like, and preferably n≧5 in order to obtain a membrane with excellent blood compatibility.

Due to their polymerizable carbon-carbon double bonds, these monomers can be used with common radical initiators, such as azobisisobutyronitrile, azobisdimethylvaleronitrile, benzoyl peroxide, etc., without using special equipment or methods. can be easily copolymerized with acrylonitrile (n). It is also possible to graft or block copolymerize polyacrylonitrile by known methods such as those described in US Pat. No. 2,940,952.

The preferred content of polyethylene oxide chain moieties in the copolymer of the present invention is 10 to 40% by weight. The polyethylene oxide content in the copolymer can be confirmed by conventional techniques such as elemental analysis, infrared absorption spectrum, and nuclear magnetic resonance spectrum. Moreover, the molecular weight of the copolymer is preferably 100,000 to 1,000,000 in weight average molecular weight considering the mechanical properties of the obtained film.

Next, the solvent used in the present invention is not particularly limited, but dimethyl sulfoxide (DMSO) is preferred. DMSO
has a suitable affinity with the polymer system, and therefore has good membrane-forming properties, and a plasma separation membrane having a uniform pore size can be easily obtained by adjusting membrane-forming conditions or additives to the solvent. Solvents that have a high affinity for the polymer system make it difficult to obtain membranes with the pore size necessary for plasma separation, and solvents that have low solubility for the polymer system have problems with membrane formation. It is not preferable because it is inferior and the strength of the obtained film is also low.

DMSO is infinitely soluble in water and can be easily removed by washing with water after film formation and silk spinning.It is also extremely low in toxicity compared to other solvents, making it suitable for use in products intended for work environments or medical purposes. It has extremely excellent properties from the standpoint of safety.

Furthermore, when preparing the membrane-forming stock solution, water, formamide,
Alcohols (butanol, propatool, ethylene glycol, glycerin, polyvinyl alcohol, etc.),
It is also a preferable method to add a non-solvent such as urea or calcium chloride, or to add a surfactant such as polyoxyethylene ether lauryl alcohol or isooctyl phenoxy polyethoxy ethanol. Among these, polyvinyl alcohol has a large addition effect and is a preferable additive when forming an ultrafiltration membrane or a plasma separation membrane with uniform pore size (including thread forming). In particular, the degree of polymerization is 1000~
5000 polyvinyl alcohol has moderate compatibility with copolymer (I) and is preferable for obtaining a porous membrane such as a plasma separation membrane.

The additive fraction in this solvent system is 5-25% DMS.
This is preferable in order to obtain a membrane having separation characteristics as a plasma separation membrane without losing the good membrane-forming (thread-spinning) properties of O.

The membrane-forming stock solution obtained in this way can be used to form membranes by various known methods. For example, on a glass plate having a spacer of an appropriate thickness, a heated and melted film-forming stock solution is uniformly cast using a doctor blade, and then cooled and solidified.

Thereafter, the membrane is immersed in a coagulation bath having an appropriate composition and temperature to remove the solvent, thereby fixing the gel structure and obtaining a porous membrane suitable for plasma separation.

The coagulation bath is generally preferably water, aliphatic lower alcohols, a mixture thereof, or a mixture thereof with DMSO added thereto, particularly a mixture of water and DMSO with a DMSO addition rate of 2 to 40%. Preferably used.

The coagulation bath temperature is usually 0 to 98°C, preferably 20 to 50°C.
It is carried out at around ℃.

By forming and storing the membrane of the present invention in a water-containing or wet state without drying it from a coagulation bath, the permeation performance and mechanical properties do not change significantly over a long period of time. It is sufficient to keep it moist by applying a suitable wetting agent such as hydrated glycerin.

In addition to the above, examples of surfactants include ethylene glycol, polyethylene glycol, and various surfactants.

Furthermore, it is also possible to change the permeation performance and mechanical properties (dimensional stability, etc.) of the membrane by heat treatment after film formation.

Heat treatment is performed under tension or no tension, and the temperature is usually 5.
0 to 1) 0°C, preferably 70 to 90°C.

〔Effect of the invention〕

Regarding the blood compatibility of the plasma separation membrane of the present invention, Lee-
Various in vitro methods such as the White method, extracorporeal bypass circulation method, and intravascular injection.

6) (Can be evaluated by ViVO or in vivo tests.

As a result of evaluation using this method, it was found that the plasma separation membrane of the present invention exhibits excellent blood compatibility by significantly suppressing the adhesion of blood components, especially platelets, which cause thrombus formation, to the membrane surface. Ta.

Examples are shown below, but the present invention is not limited to these Examples.

Example 1 105 g of methoxypolyethylene glycol monomethacrylate ("M-900G", polymerization degree of ethylene oxide moiety: 90) manufactured by Shin Nakamura Chemical Industry ■ and 595 g of acrylonitrile were dissolved in 3 kg of DMSO, and 2,2' was used as a radical polymerization initiator. Add 750 mg of -azobis-(2,4-dimethylvaleronitrile). After polymerization was carried out at 50°C for 16 hours under an argon stream, the polymerization stock solution was dropped into methanol to form a polymer precipitate, which was further washed several times and dried under vacuum to form an acrylonitrile copolymer with polyethylene oxide chains ( A) was obtained.

The polyethylene oxide content in this copolymer was examined by infrared absorption spectrum and was found to be 18% by weight.

Moreover, the weight average molecular weight of this copolymer measured by GPC was 820,000 in terms of polystyrene.

6.0 g of this copolymer (A) is dispersed in a mixed solvent consisting of 4.4 g of polyvinyl alcohol with a degree of polymerization of 2000 and 3039.6 g of DM. Stir gently at 70°C for 16 hours to create a homogeneous solution.

The viscosity of this solution was 980 poise at 70°C.

After defoaming this solution, it was heated to 0°C with a 125 micron polyester film baser.
It is cast onto a 0 cm x 30 cm glass plate using a doctor playdough and immediately immersed in a room temperature (approximately 20° C.) coagulation bath consisting of 70% water and 30% DMS.

The immersion immediately causes the solvent and coagulation bath to interdiffuse, fixing the polymer structure and replacing the internal solvent with water. This membrane becomes a porous membrane in which water is completely replaced by repeated washing with water.

A scanning electron micrograph of the surface of this film is shown in FIG.

As seen in the photograph, uniform pore diameters of 0.5 to 1.0 microns were observed on the membrane surface.

The water permeation rate of pure water through this membrane is 22. Oj! /h-m-m
mHg, the filtration rate of the 0.2x albumin aqueous solution was 15.61/h-rd·mmHg, and the albumin permeability was 98% or more.

Furthermore, this membrane was used in Amicon's thin layer filtration device (TCF).
Z-type) and a fresh rabbit mortar (heparin 7 U/m)
1) under a pressure of 50 mmHg, 1 ml/...i
The plasma filtration rate when flowing at n is 60 m1/h-rd-
nBnHg, and the total protein transmittance was 98%. Note that no leakage of platelets or red blood cells into the filtered plasma was observed.

Moreover, the breaking strength of this membrane was 52 Kg/cffl, and the breaking elongation was 120%.

From the above results, it was found that this membrane has the permeability and mechanical properties necessary for a plasma separation membrane.

Example 2 The plasma separation membrane produced in Example 1 was separated from rabbit platelet-rich plasma (P
PP) for 3 hours at 37°C, and the amount of platelets attached to the membrane surface was determined as the amount of protein measured by amino acid analysis.

As a comparative sample, a plasma separation membrane prepared by the method of Example 1 from polyacrylonitrile obtained by radical polymerization was used.

The water permeation rate of this membrane is 28.51/h = rd-mmH
g, and the plasma filtration rate from fresh rabbit blood is 52 m6/
h・rd-mmHg and total protein transmittance is 96%
Met.

Here, for PRP, blood was collected from the carotid artery of a rabbit using a syringe, and immediately transferred to a silicone-treated test tube containing 1/10 volume of 3.8% sodium citrate solution.
The sample obtained by centrifugation at 00Xg for 10 minutes was used.

The platelet count was approximately 200,000/μl.

To quantify the amount of adhered platelets, the adhered sample is first washed with a phosphate buffer and fixed with a 3% glutaraldehyde solution.

Then, the amount of amino acids obtained by hydrolyzing the deposits with 6N hydrochloric acid was determined by converting the amount of amino acids into the amount of protein.

The results are shown in Table 1, and it was clearly found that the amount of platelets adhering to the surface of the plasma separation membrane of the present invention was extremely small, indicating excellent blood compatibility.

Table 1 Adhesion of platelets to the plasma separation membrane surface (number of experiments n/5)

[Brief explanation of drawings]

FIG. 1 is a scanning electron micrograph of the surface of the plasma separation membrane prepared in Example 1.

Claims (1)

[Claims] (1) A plasma separation membrane made of a copolymer of acrylonitrile and a monomer having a polyethylene oxide chain in its side chain and a polymerizable carbon-carbon double bond.