JP2003328229A - Biodegradable porous ultrafine hollow fiber and method for producing the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a scaffold using a biodegradable porous hollow fiber which cannot be used for scaffolding for regenerating a smaller tissue. The present invention provides a biodegradable porous ultrafine hollow fiber having both properties. SOLUTION: In a method for producing a hollow fiber by a wet double spinning method, a poly-α-hydroxy acid or a copolymer containing them is dissolved in a solvent, and the temperature of a coagulation bath after discharge is adjusted to the freezing point of the material to be coagulated. Freezing said coagulation bath material,
Thereafter, it is manufactured by slowly removing the solvent.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a biodegradable fiber, particularly a porous ultrafine hollow fiber, which is used as a scaffold for regenerating biological tissue, and a method for producing the same.

[0002]

2. Description of the Related Art In recent years, a technique for regenerating or treating an organ or organ of a human body that has failed to function normally or a defective bone has been developed, and a therapeutic method using such a technique has been put into practical use. For example, a technique is known in which cells are embedded in a scaffold (scaffold) having a three-dimensional structure formed using collagen, and the tissue is regenerated by the growth of the cells and the scaffold that is naturally decomposed.

However, since collagen has problems that it contracts during culture and becomes a source of infection such as BSE (mad cow disease), polylactic acid or polyglycolic acid, which is a synthetic product with few such problems, is known. Scaffolds using poly α-hydroxy acids or copolymers containing them are represented in, for example, US Pat. No. 5,736,372 and Japanese Patent Publication No. 6-6155, and are used for regeneration of cartilage tissue and the like. It has been put to practical use. These scaffolds have a porous three-dimensional structure and are decomposed with the growth of cells, and thus are useful as scaffolds for tissue regeneration.

However, scaffolds formed by poly-α-hydroxy acids such as polylactic acid and polyglycolic acid are
Since it is hydrophobic and has rigidity, it has a problem of poor biocompatibility such as cell adhesion. On the other hand, Japanese Unexamined Patent Publication No. 2002-65247 discloses a cell culture device comprising a porous body of lactic acid-trimethylene carbonate copolymer. This is a material in which the material is made porous and flexibility is given to enhance biocompatibility. In addition, the inventors of the present application have also proposed a technique of chemically modifying the surface of these materials to enhance biocompatibility (Tetsuji Yamaoka et al., Polymer Processing, 47 (8), 338 (1).
998) etc.).

On the other hand, in the cell culture in the scaffold, it is necessary to supply oxygen and nutrients to the cells and circulate such as discharging waste products. When is regenerated, oxygen and nutrients are not supplied to the inside, and waste products are not discharged, so that there is a problem that cells inside are likely to die. On the other hand, Japanese Unexamined Patent Publication No. 2002-20523 discloses a technique for ensuring supply / circulation of nutrients to internal cells by communicating micropores in a scaffold and preventing closure of micropores on the surface. Has been presented. However, this is mainly to expect the circulation of the substance by diffusion in the liquid, and does not actively secure the circulation route.If the cells increase and become dense, the micropores should be connected. If this is done alone, the supply and circulation of substances to the cells inside will be insufficient, and tissue regeneration will often fail.

To address this problem, the inventors of the present application previously developed hollow fiber-shaped polylactic acid and presented a technique for using it in a scaffold (Nakamura et al. Annual Polymer Conference (200).
1.5.23-25), 23rd Society of Biomaterials (2001.10.22-23) P2-18, P1
94). This is poly-alpha such as polylactic acid dissolved in a solvent.
A mixture of hydroxy acid, starch, starch, etc. is produced by melt spinning while feeding mainly nitrogen.
It was produced by slowly removing solvent through a coagulation bath of warm water in wet spinning, and communicating micropores inside and outside, promoting angiogenesis in the lumen area of the fiber, and realizing substance permeability inside and outside the hollow fiber. The cells are attached to the outside of the hollow fibers that make them up, and it is possible to prevent the necrosis of cells inside the tissue by securing a transport route for oxygen and nutrients from the inside.

However, the hollow fiber has a large outer diameter of 1 mm or more and lacks flexibility, and has a problem that it cannot be used for regeneration of a relatively large tissue. Therefore, it was considered to reduce the concentration of polylactic acid or to increase the length of the air gap in order to create a thinner hollow fiber.However, in the conventional method using water for both the coagulation bath and the core, the Since the solvent velocity was high, the hollow fiber was crushed and the fiber could not be recovered while maintaining the hollow structure. This was also the case with methanol, which has a slower solvent removal rate than water.

[0008]

DISCLOSURE OF THE INVENTION The present invention solves the above-mentioned problems and cannot be applied to a conventional scaffold using a porous hollow fiber having biodegradability.
It is an object of the present invention to provide a further ultrafine hollow fiber having an outer diameter of less than 1 mm and having flexibility, which can be used for regeneration of a smaller tissue. In the present invention, hollow fibers having an outer diameter of less than 1 mm are called ultrafine hollow fibers.

[0009]

The biodegradable porous ultrafine hollow fiber of the present invention is mainly composed of poly α-hydroxy acid or a copolymer containing them, and has an inner diameter of 500 μm or less and is biodegradable. A very fine hollow fiber that can be used as a scaffold when regenerating smaller tissues. In the method for producing a hollow fiber by the wet double-spinning method, poly (α-hydroxy acid) or a copolymer containing them is dissolved in a solvent, and the temperature of the coagulation bath after discharge is adjusted to be equal to or lower than the freezing point of the substance to be coagulated. By the production method in which the coagulation bath substance is frozen and then desolvated, the ultrafine hollow fiber as described above can be recovered while maintaining the hollow structure.

Further, by using dioxane as the solvent, the hollow fiber can be made porous to give sufficient permeability, and the effect on the living body can be minimized. By using dry ice-methanol in the coagulation bath, , It is possible to freeze various kinds of coagulation bath substances easily. Further, by setting the air gap to 10 cm or more, it becomes easy to produce an ultrafine hollow fiber, and by drawing in a coagulation bath, a thinner hollow fiber can be obtained. Furthermore, by using polylactic acid or glycolic acid as the poly α-hydroxy acid to be used, it is possible to easily manufacture the ultrafine hollow fiber, and it can be expected to be harmless to the living body and sufficiently biodegradable.

[0011]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention will be described below with reference to the drawings and photographs.

[0012] As described above, in the conventional method for producing a biodegradable porous hollow fiber used for a tissue regeneration scaffold (scaffold), when an outer diameter of less than 1 mm is to be obtained. However, because of the high desolvation rate, it was difficult to recover the hollow fiber while maintaining the hollow structure even when methanol was used in the coagulation bath. Therefore, in FIG.
As shown in Fig. 4, by temporarily freezing the substance to be coagulated using dry ice-methanol in the coagulation bath, the desolvation is temporarily stopped, and then the ice water and water are sequentially immersed in the coagulation bath to remove the solvent over time. It is intended to encourage. As a result, the hollow structure can be maintained without being deformed while reducing the fiber diameter and improving the flexibility.
In the wet spinning, the hollow fiber produced is made porous by removing the solvent of the poly α-hydroxy acid dissolved in the solvent and the copolymer containing them in the coagulating liquid.

More specifically, in the present embodiment, poly L-lactic acid, which is polylactic acid as a poly α-hydroxy acid or a copolymer containing them, is used.
(Hereinafter referred to as "PLLA") is used. This is because the strength and its decomposition rate, which are advantages of synthetic polymers, can be easily adjusted by changing the molecular weight or the composition of the copolymer. Polyglycolic acid (hereinafter referred to as "PGA") is also useful because it is the same as the above. But P
LLA has a slower decomposition rate than PGA and has an advantage of being easily dissolved in an organic solvent.

For wet spinning, a double wet spinning apparatus is used,
In this embodiment, an apparatus equipped with a nozzle having an outer diameter of 1.0 mm and an inner diameter of 0.6 mm and capable of extruding two different kinds of solutions is used. The nozzle is made like this
The limit of the thinness of the nozzle is determined by the viscosity and surface tension of the solution used, but under the conditions of the present embodiment, a thinner one cannot be used. PLLA dissolved in dioxane is extruded on the outer diameter portion (sheath portion) of the nozzle, and methanol is extruded on the inner diameter portion (core portion) to perform spinning.

The concentration of PLLA was set to 18% by weight. At 15%, if the air gap (distance between nozzle and coagulation bath) is extended to 30 cm or more, yarn breakage occurs and stable spinning cannot be performed, and at 18%, even if the air gap is 60 cm or more, stable spinning is not possible. This is because they could be spun. That is, in the present embodiment, the optimum concentration for extending the air gap and stretching by the self weight is set to 18%. As the solvent for PLLA, dioxane was used because the organic solvent was not used in consideration of the use in vivo and the environment.

The thickness of the hollow fiber can be adjusted by adjusting the length of the air gap. However, as shown in Graph 1 of FIG. 2, the concentration of PLLA is set to 15% by weight and the extrusion amount is broken. When it is fixed under the condition that only the air gap is changed, for example, the outer diameter of the hollow fiber is 250 μm or less at a distance of 10 cm, and if it is more than this distance, an ultrafine hollow fiber having a wide range of application in tissue regeneration is produced. It will be easy.

By spinning under the above conditions, micro-order hollow fibers can be recovered while maintaining the hollow state. As shown in the SEM photograph in FIG. 3, the hollow fiber produced by this method was able to be produced without deforming while maintaining the hollow structure even when the diameter of the hollow fiber was in the micro order. FIG. 4 is a SEM photograph of the cross section further enlarged, and it was porous even in this manufacturing method.

Further, finer hollow fibers can be recovered by stretching when they enter the coagulation bath. Stretching can be performed by pinching the extruded hollow fiber with, for example, tweezers and pulling it faster than the extrusion speed.However, in the recovery of the ultrafine hollow fiber, the extrusion speed is fast and the yarn diameter is small, so Since the hollow fibers that have entered are likely to be twisted and accumulated in one place, use a coagulation bath in a beaker and use a coagulation liquid (dry ice-methanol).
It is also possible to collect the ultrafine hollow fibers in a filament shape while stretching them by rotating them with a vertically standing motor.

[0019]

EXAMPLES The present invention will be specifically described below with reference to examples.

(Spinning Device) FIG. 5 shows a double wet spinning device (Oba Inc., Osa) used for wet spinning in this example.
ka, Japan), and different solutions can be extruded into the outer diameter (sheath) and inner diameter (core) of a nozzle with an outer diameter of 1.0 mm and an inner diameter of 0.6 mm. These two types of solutions do not touch each other in the nozzle, but only come into contact with each other when they are pushed out. The other main parts are tanks that store the two types of solutions (each tank can be pressurized and high viscosity solutions can be extruded) and gear pumps that extrude each solution. Two are installed.

(Coagulation Bath / Coagulation Bath Material) Dioxane (1,4-dioxane manufactured by Wako Pure Chemical Industries, Ltd., Lot; LDP35) is used for the sheath.
PLLA dissolved in (0) (in Shimadzu oil bath,
While refluxing at 85 ° C., a mechanical stirrer was used to stir for 8 h), and methanol (made by Wako Pure Chemical Industries, Ltd.) was extruded into the core. Dry ice-methanol was used for the coagulation bath. The coagulation bath in FIG. 5 was the same as that in the comparative example using water, whereas in the present example using dry ice-methanol, a beaker was used and the solution was stirred with a stirrer to collect the yarn. In addition, in order to prevent the threads from clumping, in No.M2, the motor (PSH425-401P, manufactured by Oriental Motor Co., Ltd.) was erected vertically, and the coagulation bath fixing table (self-made) was installed on the rotating shaft to set the coagulation bath. Rotated (not shown). Table 1 shows the preparation conditions for wet spinning using a dry ice-methanol coagulation bath. However, * () indicates the extrusion rate (g / min) as a solution.

[0022]

[Table 1]

Comparative Example In the comparative example, the solvent in the examples was water at room temperature, and the coagulation bath was room temperature water or 40 to 45 ° C.
The tip was pinched with tweezers in warm water of about 1 m in a bath length of about 1 m, and it was collected by pulling it in a straight line in accordance with the speed of extrusion. Table 2 shows the preparation conditions of the comparative example. However, PDLLA is racemic (D + L) polylactic acid.

[0024]

[Table 2]

(Preparation Result) As shown in Table 3, in the wet spinning (M1-1 to M3) using dry ice-methanol in the coagulation bath, the outer diameter is 50 to 500 μm and the film thickness is 5 to 5. It was possible to prepare a 200 μm porous ultrafine hollow fiber (see FIGS. 6 and 7). On the other hand, in the conventional wet spinning (W1 to W5) using water (warm water) in the coagulation bath, the outer diameter is 20
A porous hollow fiber having a thickness of 100 to 200 μm and a thickness of 100 to 200 μm could be prepared (FIG. 8). still,
The extrusion rate of the sheath portion in (Table 3) was expressed as the solution weight / minute, and for M3, stretching was applied in the coagulation bath by increasing the stirrer stirring rate.

[0026]

[Table 3]

(Evaluation of Ultrafine Hollow Fiber) The porous ultrafine hollow fiber according to the present example was found to have improved flexibility as the yarn diameter became smaller. On the other hand, the substance permeability has not been confirmed because the mini-module for the test has not been successfully created. However, the material permeability has been confirmed in the millimeter order hollow fiber produced by the conventional method for producing a hollow fiber, and the similar porous structure has been confirmed in the ultrafine hollow fiber. Guessed.
Regarding the cell adhesiveness, a quantitative evaluation could not be performed in the experiment in which the cells were seeded in the prepared ultrafine hollow fiber (all of the seeded cells did not adhere to the hollow fiber, and by Giemsa staining). (Because it cannot be judged from the color density),
It was confirmed that the cells adhered and proliferated from the results of taking out from the medium after 3, 6 and 9 days and performing Giemsa staining.

[0028]

As described above, according to the present invention, poly α
By dissolving the hydroxy acid or a copolymer containing them in a solvent, making the temperature of the coagulation bath after discharge below the freezing point of the substance to be coagulated and freezing the substance to be coagulated and then removing the solvent, It was possible to produce a biodegradable porous ultrafine hollow fiber having a flexibility of 1 mm or less, and it became possible to use it as a scaffold for regenerating smaller tissues.

By using dioxane as the solvent, the hollow fiber can be made porous to give sufficient permeability, and the effect on the living body can be minimized. By using dry ice-methanol in the coagulation bath, , It is possible to freeze many kinds of coagulation bath substances easily, and it becomes easier to make a further ultrafine hollow fiber by setting the air gap to 10 cm or more, and by drawing in the coagulation bath, a thinner hollow fiber Can be Furthermore, by the above manufacturing method,
Ultrafine hollow fibers having an inner diameter of 500 μm or less can also be produced, but this has made it possible to support more types of tissue regeneration. Furthermore, by using polylactic acid or glycolic acid, it is possible to obtain an ultrafine hollow fiber which can be easily produced, is harmless to the living body, and has sufficient biodegradability.

[Brief description of drawings]

FIG. 1 is a schematic diagram showing a method of a coagulation bath according to an embodiment of the present invention.

FIG. 2 is a graph showing the relationship between the air gap and the yarn diameter according to the embodiment of the present invention.

FIG. 3 is an enlarged photograph (SEM photograph) of a cross section of an ultrafine hollow fiber produced by the method for producing an ultrafine hollow fiber of the present invention.

FIG. 4 is a further enlarged photograph (CEM photograph) of a cross-sectional portion of the ultrafine hollow fiber in FIG.

FIG. 5 is a schematic diagram of a double wet spinning apparatus used in Examples and Comparative Examples of the present invention.

FIG. 6 is an ultrafine hollow fiber (M1-1 to M1) in an example of the present invention.
-3) An enlarged photograph of a cross section (CEM photograph) and a photograph in which the cross section is further enlarged.

FIG. 7 is an enlarged photograph (M2, M3) (CEM photograph) of a cross section of an ultrafine hollow fiber in an example of the present invention, a further enlarged photograph (M3) of the cross section, and an enlarged photograph showing the shape of the hollow fiber. (M2).

FIG. 8 is an enlarged photograph of a cross section of a hollow fiber in a comparative example and a further enlarged photograph of the cross section (CEM photograph, only W3 is photographed by a light microscope).

   ─────────────────────────────────────────────────── ─── Continued front page    F-term (reference) 4B029 AA01 AA21 BB11                 4C081 AB01 AB11 AB31 AB35 BA12                       BA13 BA16 BB02 BB07 BC01                       BC02 CA171 DA03 DA04                       DB01 DB03 DC11 EA02 EA03                       EA11 EA12                 4L035 AA09 BB03 BB04 BB05 BB11                       BB15 BB16 BB73 DD03 DD07                       DD14 EE20 FF01

Claims (7)

[Claims] 1. A biodegradable porous ultrafine hollow fiber comprising a poly α-hydroxy acid or a copolymer containing them as a main component and having an inner diameter of 500 μm or less. 2. A method for producing a hollow fiber by a wet double-spinning method, in which a poly-α-hydroxy acid or a copolymer containing them is dissolved in a solvent and the temperature of the coagulation bath after discharge is adjusted to be equal to or lower than the freezing point of the substance to be coagulated. Freeze the coagulated bath substance,
The solvent is then removed, the method according to claim 1.
A method for producing the biodegradable porous ultrafine hollow fiber according to the description. 3. The method for producing a biodegradable porous ultrafine hollow fiber according to claim 2, wherein the solvent is dioxane. 4. The method for producing a biodegradable porous ultrafine hollow fiber according to claim 2, wherein the coagulation bath is dry ice-methanol. 5. The air gap is 10 cm or more,
The method for producing the biodegradable porous ultrafine hollow fiber according to claim 2, 3 or 4. 6. The method of claim 2, wherein the drawing is performed in a coagulation bath.
The method for producing a biodegradable porous ultrafine hollow fiber according to 3, 4, or 5. 7. The biodegradable porous ultrafine hollow fiber according to claim 1, 2, 3, 4, 5 or 6, wherein the poly α-hydroxy acid is polylactic acid or glycolic acid, or a method for producing the same.