JP2020141855A - Artificial blood vessel and manufacturing method of artificial blood vessel - Google Patents

Abstract

To provide an artificial blood vessel having both cellular infiltration properties, and strength and flexibility to withstand the hemodynamics even when it is used in a cardiovascular system, and a manufacturing method of the artificial blood vessel.SOLUTION: A tube-like porous artificial blood vessel includes: a tube-like porous body formed of a bioabsorbable material; and a fiber nonwoven fabric layer with a fiber diameter of 1-10 μm and a pore diameter of 3-100 μm formed of a bioabsorbable material on the porous body.SELECTED DRAWING: Figure 1

Description

The present invention relates to an artificial blood vessel and a method for producing an artificial blood vessel having both cell infiltration property and strength and flexibility to withstand hemodynamics even when used in a cardiovascular system.

Recent advances in cell engineering technology have made it possible to culture a large number of animal cells, including human cells, and research on so-called regenerative medicine, which attempts to reconstruct human tissues and organs using these cells, is rapidly progressing. Proceed to.
For example, the most used artificial blood vessels in clinical practice are those using non-absorbable polymers such as Gore-Tex, but artificial blood vessels using non-absorbable polymers have foreign substances in the body for a long time after transplantation. Since it remains in the blood vessel, there is a problem that an anticoagulant or the like must be continuously administered, and when it is used for children, there is also a problem that it is necessary to perform a new operation as the patient grows up. On the other hand, regenerative medicine has been attempted to regenerate vascular tissue.

In regenerative medicine, the point is whether cells can proliferate and differentiate to construct a three-dimensional biological tissue-like structure. For example, a base material is transplanted into the patient's body, and cells are removed from surrounding tissues or organs. A method of invading a base material and proliferating and differentiating it to regenerate a tissue or an organ is performed.
As a base material for regenerative medicine, a porous base material made of a bioabsorbable material has been proposed. By using a porous base material made of a bioabsorbable material as a base material for regenerative medicine, cells invade and proliferate in the void portion, and the tissue is regenerated at an early stage. After a certain period of time, it decomposes and is absorbed by the living body, so it is not necessary to remove it by reoperation.

As a production of a porous base material made of a bioabsorbable material, for example, Patent Document 1 discloses nanofiber and microfiber implants using an electrospinning technique. In Patent Document 1, in order to achieve both high cell infiltration and high strength and flexibility that can withstand the hemodynamics of the human cardiovascular system, the diameter of the fiber is increased (3 to 20 μm) and polycaprolactone is used. A material in which Upy (ureido-pyrimidinone) and / or bisurea is introduced as a supramolecular compound is used.
Normally, as the fiber diameter increases, the three-dimensional fiber overlap becomes coarser, so that the space between the fibers, that is, the pore diameter also increases. However, if the fiber diameter is increased, the rigidity per fiber increases and the flexibility is lost. Therefore, in Patent Document 1, special materials such as supramolecular compounds Upy and Bisurea have to be used.

Patent Document 2 discloses an artificial blood vessel which is two layers of ultrafine fiber aggregate layers having a fiber diameter of 10 to 5000 nm on a porous body layer made of a bioabsorbable material, that is, a so-called sponge layer. With such a sponge structure, the bulk density and the pore diameter can be easily adjusted without using a special material, and flexibility can be imparted. Although Patent Document 2 has high performance as an artificial blood vessel, it cannot be said that it is sufficient for use in the cardiovascular system, which is a harsher environment, and an artificial blood vessel having cell infiltration, strength and flexibility at a higher level. Blood vessels are required.

Japanese Unexamined Patent Publication No. 2017-221727 International Publication No. 2017/022750

In view of the above situation, the present invention provides an artificial blood vessel and a method for producing an artificial blood vessel having both cell infiltration property and strength and flexibility to withstand hemodynamics even when used in a cardiovascular system. With the goal.

The present invention is a porous tubular artificial blood vessel having a tubular porous body made of a bioabsorbable material and a fiber diameter of 1.0 to 10 μm and a pore diameter made of a bioabsorbable material on the porous body. It is an artificial blood vessel having a fiber non-woven fabric layer of 3 to 100 μm.
The present invention will be described in detail below.

The present inventor has made the cell infiltrative and cardiovascular system by further providing a fibrous non-woven fabric layer having a specific fiber diameter and pore diameter on the outer diameter side of a porous tubular artificial blood vessel made of a bioabsorbable material. We have found that an artificial blood vessel having a high level of strength and flexibility that can withstand hemodynamics can be obtained even when it is used, and have completed the present invention.

The artificial blood vessel of the present invention has a tubular porous body made of a bioabsorbable material.
By forming the artificial blood vessel with a tubular porous body, the artificial blood vessel serves as a scaffold for the invading cells, so that the blood vessel can be regenerated at an early stage. Further, by using a bioabsorbable material, it plays a role as a blood vessel until the blood vessel is regenerated, and is gradually absorbed into the living body as the blood vessel is regenerated, so that it does not need to be taken out by reoperation.

Examples of the bioabsorbable material include polyglycolide, polylactide, poly-ε-caprolactone, lactide-glycolic acid copolymer, glycolide-ε-caprolactone copolymer, lactide-ε-caprolactone copolymer, polycitrate, and the like. Polyapple acid, poly-α-cyanoacrylate, poly-β-hydroxy acid, polytrimethylene oxalate, polytetramethylene oxalate, polyorthoester, polyorthocarbonate, polyethylene carbonate, poly-γ-benzyl-L-glutamate, Synthetic polymers such as poly-γ-methyl-L-glutamate, poly-L-alanine, and polyglycol sebastic acid, polysaccharides such as starch, alginic acid, hyaluronic acid, chitin, pectinic acid and derivatives thereof, gelatin, Examples thereof include natural polymers such as proteins such as collagen, albumin and fibrin. These bioabsorbable materials may be used alone or in combination of two or more.

It is preferable that the porous body has a skin layer having a relatively small pore diameter in the innermost layer, and a porous layer having a relatively large pore diameter around the skin layer.
Since the pore diameter on the inner diameter side (the side in contact with blood flow) of the tubular porous body is smaller than the pore diameter on the outer diameter side, it is possible to regenerate an extremely normal blood vessel that is less likely to thicken or calcify. The skin layer and the porous layer can be formed by a production method described later.

The reason why blood vessels can be regenerated extremely normally by having a skin layer and a porous layer is unknown, but it is considered that the reason is as follows. In order for blood vessels to be regenerated, it is necessary for the artificial blood vessel as a whole to have holes with a sufficient pore size for cells to enter, while the inner diameter side part that is in direct contact with blood flow causes thickening and calcification. It is important to prevent the adhesion of platelets. By forming a skin layer on the inner diameter side of the tubular porous body whose pore diameter is relatively smaller than that on the outer diameter side, it is possible to prevent the adhesion of platelets on the inner diameter side portion in contact with the blood flow, and other Since cells can easily invade in this part, it is considered that normal blood vessels may be regenerated.
In vitro, it has been found that the amount of platelets attached, which causes thrombus, tends to be suppressed by forming an artificial blood vessel with nanofibers and improving the smoothness of the surface thereof (Acta Biomaterialia 8). (2012) 4349-4356). In vitro, it has been found that the surface contact angle of the polymer surface having a surface with a small pore size is improved by the leaf effect of the lotus and the amount of platelets attached, which causes thrombus, is suppressed (Colloids Surf B). Biointerfaces 2014 Feb1; 114: 28-35). Taking these into consideration, having the above-mentioned skin layer in the innermost layer of the artificial blood vessel improves the smoothness of the inner diameter side surface, and the lotus leaf effect suppresses the overformation of thrombus, resulting in this. It is thought that the intima is more likely to be formed in the skin, and thickening and calcification are less likely to occur.

The preferable lower limit of the pore diameter of the holes constituting the pore structure of the skin layer is 0.5 μm, and the preferable upper limit is 20 μm. When the pore diameter of the pores constituting the pore structure of the skin layer is within this range, the effect of preventing thickening and calcification is particularly exhibited. A more preferable lower limit of the pore diameter of the holes constituting the pore structure of the skin layer is 1 μm, a more preferable upper limit is 18 μm, a further preferable lower limit is 3 μm, and a further preferable upper limit is 15 μm.

The thickness of the skin layer is not necessarily clear at the boundary with the porous layer, but the preferable lower limit is 0.1 μm and the preferable upper limit is 30 μm. When the thickness of the skin layer is within this range, extremely normal blood vessels that are less likely to thicken or calcify can be regenerated. When the thickness of the skin layer is 0.1 μm or more, the porous layer can be formed more uniformly around the skin layer, and when it is 30 μm or less, the cell infiltration property is further improved and the blood vessels The playback speed can be further improved. The more preferable lower limit of the thickness of the skin layer is 0.5 μm, and the more preferable upper limit is 20 μm.

The preferable lower limit of the pore diameter of the pores constituting the pore structure of the porous layer is 1 μm, and the preferable upper limit is 500 μm. When the pore diameter of the pores constituting the pore structure of the porous layer is 1 μm or more, the cell infiltration property is further improved, and when it is 500 μm or less, the number of cells discharged through the artificial blood vessel can be reduced. Therefore, the regeneration speed of blood vessels can be further improved. A more preferable lower limit of the pore diameter of the pores constituting the pore structure of the porous layer is 5 μm, a preferable upper limit is 400 μm, a further preferable lower limit is 10 μm, and a further preferable upper limit is 300 μm.

The maximum diameter of at least one or more holes or holes in the pore wall of the porous layer itself is preferably the same as or smaller than the pore diameter constituting the pore structure of the porous layer. The preferable upper limit of the maximum diameter of at least one or more holes or holes of the pore wall itself of the porous layer is 500 μm, the more preferable upper limit is 400 μm, and the further preferable upper limit is 300 μm.

The artificial blood vessel of the present invention has a fibrous nonwoven fabric layer made of a bioabsorbable material on the porous body.
By forming the fibrous non-woven fabric layer on the porous body, it is possible to prevent blood from leaking due to the pressure of blood flow. Furthermore, after transplantation, it exerts sufficient strength against external pressure and can prevent blood vessels from being occluded by kinking (breaking phenomenon). As the bioabsorbable material constituting the non-woven fabric layer, the same material as the porous body can be used. Further, the same bioabsorbable material may be used for the porous body and the fibrous nonwoven fabric layer, or different bioabsorbable materials may be used.

The fibrous non-woven fabric layer has a fiber diameter of 1 to 10 μm and a pore diameter of 3 to 100 μm.
Although a non-woven fabric layer has been formed on a porous body even in a conventional artificial blood vessel having a porous structure, it is a non-woven fabric layer having a small fiber diameter. As shown in FIG. 2, the non-woven fabric layer having a small fiber diameter has a high fiber density and many points of contact between the fibers, so that the strength improving effect is high, but the flexibility is lowered. In particular, when the non-woven fabric layer was thickened in order to increase the strength, the problem of reduced flexibility became more prominent. In addition, since the fiber density is high, the pore size is also small, and the cell infiltration property from outside the blood vessel is also reduced.
In the artificial blood vessel of the present invention, by increasing the fiber diameter of the fibrous nonwoven fabric layer to 1 to 10 μm as shown in FIG. 3, the rigidity of each fiber unit can be increased and the strength of the artificial blood vessel can be improved. On the other hand, when the fiber diameter is increased, the density of the fibers is reduced and the number of contact points between the fibers is reduced. Therefore, even when the fiber non-woven fabric layer is thickened, flexibility can be ensured, and the artificial blood vessel can be maintained. It is possible to achieve both strength and flexibility. Further, when the fiber diameter is increased, the pore diameter is increased, so that the cell infiltration property from the outside of the blood vessel can be enhanced. The fiber diameter and pore diameter of the fibrous nonwoven fabric layer can be adjusted by a solvent for dissolving the bioabsorbable material described later and a forming method. The fiber diameter and pore diameter of the fibrous nonwoven fabric layer can be obtained by taking an electron micrograph of the surface of the fibrous nonwoven fabric layer and averaging the values measured at any 10 points.

Since the strength and flexibility of the obtained artificial blood vessel can be enhanced, the preferable lower limit of the fiber diameter of the fibrous nonwoven fabric layer is 1.5 μm, the more preferable lower limit is 2.0 μm, the preferable upper limit is 8.0 μm, and the more preferable upper limit is It is 5.0 μm.

Since the cell infiltration property, strength and flexibility of the obtained artificial blood vessel can be enhanced, the preferable lower limit of the pore size of the fibrous nonwoven fabric layer is 4.0 μm, the more preferable lower limit is 5.0 μm, the preferable upper limit is 80 μm, and the more preferable upper limit. Is 50 μm.

The preferable lower limit of the thickness of the fibrous nonwoven fabric layer is 10 μm, and the preferable upper limit is 600 μm. When the thickness of the fibrous nonwoven fabric layer is within this range, an artificial blood vessel having both cell infiltration and strength and flexibility that can withstand hemodynamics even when used in the cardiovascular system can be obtained.

The inner diameter of the artificial blood vessel of the present invention is not particularly limited, but from the inner diameter of a general blood vessel, a preferable lower limit is 0.5 mm and a preferable upper limit is about 8.0 mm. The outer diameter of the artificial blood vessel is not particularly limited, but from the outer diameter of a general blood vessel, a preferable lower limit is 1.0 mm and a preferable upper limit is about 10.0 mm.
In particular, according to the method for producing an artificial blood vessel described later, an artificial blood vessel having a large inner diameter used for a cardiovascular system and an artificial blood vessel having an inner diameter of about 2.0 to 5.0 mm used for regeneration of a peripheral blood vessel can be easily produced. Can be manufactured.

The artificial blood vessel of the present invention preferably has a compliance value of 0.2 to 8.0.
The compliance value refers to the degree of diametrical deformation of the artificial blood vessel when a pressure equal to blood pressure is applied. Generally, it refers to the extensibility or extensibility of an artificial blood vessel. When the compliance value of the artificial blood vessel of the present invention is within the above range, it is possible to exhibit flexibility to withstand hemodynamics even when used in the cardiovascular system. The compliance value can be adjusted by the fiber diameter and the pore diameter of the fibrous nonwoven fabric layer. The more preferable lower limit of the compliance value is 0.3, the more preferable lower limit is 0.4, the more preferable upper limit is 7.0, and the further preferable upper limit is 5.0.
The compliance value can be measured by the method shown in Examples described later.

The artificial blood vessel of the present invention may further contain an agent that prevents the formation of a thrombus such as heparin, a growth factor that promotes the regeneration of blood vessels such as bFGF, and the like. Furthermore, cells such as mesenchymal stem cells may be seeded prior to transplantation.

Here, an enlarged electron micrograph of a cross section of the artificial blood vessel obtained in Example 1 described later is shown in FIG. In FIG. 1, the downward direction is the inner diameter side and the upper direction is the outer diameter side. As shown in FIG. 1, the artificial blood vessel of the present invention has a porous layer on the inner diameter side, and has a structure in which a fibrous nonwoven fabric layer is laminated on the outer diameter side of the porous body. The layer near the inner diameter side surface of the porous body, that is, the skin layer, has an average pore diameter (for example, about 25 μm) that is relatively smaller than the average pore diameter (for example, about 25 μm) of the porous body near the outer diameter side surface of the porous body. For example, it can be seen that it is about 1 μm).

A method for producing a porous tubular artificial blood vessel, wherein the bioabsorbable material, the solvent 1 having a relatively low solubility in the bioabsorbable material, and the bioabsorbable material are relative to each other. A uniform solution in which the bioabsorbable material is dissolved is prepared by using a solvent 2 having a high solubility in the solvent 1 and incompatible with the solvent 1 and a co-solvent 3 compatible with the solvent 1 and the solvent 2. A step, a coating step of applying the uniform solution to the surface of the rod, and a tubular porous material made of a bioabsorbable material around the rod by cooling the uniform solution on the surface of the rod. Bioabsorbability with a fiber diameter of 1 to 10 μm and a pore size of 3.0 to 100 μm by a precipitation step of precipitating a body, a freeze-drying step of freeze-drying the tubular porous body, and an electrospinning method on the porous body. A method for producing an artificial blood vessel having a step of forming a fibrous solvent layer made of a material is also one of the present inventions.

In the method for producing an artificial blood vessel of the present invention, first, a dissolution step of preparing a uniform solution in which a bioabsorbable material is dissolved is performed using a bioabsorbable material, a solvent 1, a solvent 2, and a co-solvent 3.
As the bioabsorbable material, the same bioabsorbable material as the bioabsorbable material in the artificial blood vessel of the present invention can be used.

The solvent 1 is a so-called poor solvent having a relatively low solubility in the bioabsorbable material. Here, the relatively low solubility means that the bioabsorbable material has a property of being more difficult to dissolve than the solvent 2. As the solvent 1, when the bioabsorbable material is a synthetic polymer, for example, water, methanol, n-propanol, isopropanol, n-butanol and the like can be used. Of these, water is preferable because it is easy to handle.

The solvent 2 is a so-called good solvent having a relatively high solubility in the bioabsorbable material.
The solvent 2 is incompatible with the solvent 1. Here, "incompatible" means that the phase is separated even when mixed and stirred at room temperature of 25 ° C.
As the solvent 2, when the bioabsorbable material is a synthetic polymer and water is selected as the solvent 1, for example, methyl ethyl ketone, diethyl ketone, methyl propyl ketone, methyl isobutyl ketone, methyl amino ketone, etc. Organic solvents such as cyclohesanone, chloroform, ethyl acetate and toluene can be used. Of these, methyl ethyl ketone, chloroform, etc. are preferable because they have relatively low toxicity.

The co-solvent 3 is compatible with both the solvent 1 and the solvent 2. By combining such a co-solvent 3, it is possible to produce an artificial blood vessel by the phase separation method even if the solvent 1 and the solvent 2 are incompatible, and there are options for the combination of the solvent 1 and the solvent 2. Spreads dramatically. Here, "compatible" means that phase separation does not occur even when mixed and stirred at room temperature of 25 ° C.

As the co-solvent 3, when the bioabsorbable material is a synthetic polymer and water is selected as the solvent 1 and an organic solvent is selected as the solvent 2, for example, acetone, methanol, ethanol, propanol, etc. Isopropanol, n-butanol, 2-butanol, isobutanol, tetrahydrofuran and the like can be used.

The compounding ratio of the solvent 1 and the solvent 2 is not particularly limited, but it is preferable that the solvent 1 and the solvent 2 are in the range of 1: 1 to 1: 100 by weight. Within this range, a uniform artificial blood vessel can be produced. More preferably, it is in the range of 1: 10 to 1:50. The blending ratio of the total of the solvent 1 and the solvent 2 and the co-solvent 3 is not particularly limited, but the total of the solvent 1 and the solvent 2 and the co-solvent 3 are in a weight ratio of 1: 0.01 to 1:0.5. It is preferably within the range of. Within this range, a uniform artificial blood vessel can be produced. More preferably, it is in the range of 1: 0.02 to 1: 0.3.

The pore size of the obtained artificial blood vessel can be controlled by adjusting the blending ratio of the solvent 1 and the solvent 2. Specifically, increasing the ratio of the solvent 1 increases the pore size of the obtained artificial blood vessel, and increasing the ratio of the solvent 2 reduces the pore size of the obtained artificial blood vessel. However, in the method of adjusting the compounding ratio of the solvent 1 and the solvent 2, the bulk density also fluctuates at the same time, and it is difficult to produce an artificial blood vessel having an arbitrary pore size and bulk density.
Therefore, in the method for producing an artificial blood vessel of the present invention, it is preferable to use two or more of the above co-solvents 3 in combination (hereinafter, the plurality of co-solvents 3 to be used are referred to as "co-solvent 3-1" and "co-solvent 3", respectively. -2 ", ..., and the whole of these is also referred to as co-solvent 3). The pore size of the obtained artificial blood vessel can be controlled by combining two or more of the co-solvents 3 and adjusting the blending ratio of the co-solvent 3-1 and the co-solvent 3-2, for example. That is, the porosity obtained by adjusting the blending ratio of the co-solvent 3-1 and the co-solvent 3-2 contained in the co-solvent 3 while keeping the blending ratio of the solvent 1 and the solvent 2 and the co-solvent 3 constant. The pore size of the solvent can be controlled. This means that only the pore size can be adjusted while keeping the bulk density of the obtained artificial blood vessel almost constant. According to such a method for producing an artificial blood vessel of the present invention, it becomes easy to produce an artificial blood vessel having an arbitrary pore size and bulk density.

The combination of the bioabsorbable material and each solvent is not particularly limited. For example, the bioabsorbable material is a lactide-ε-caprolactone copolymer, the solvent 1 is water, the solvent 2 is methyl ethyl ketone, and a co-solvent. A combination in which 3-1 is acetone and co-solvent 3-2 is ethanol, or the bioabsorbable material is polylactide, the solvent 1 is water, the solvent 2 is chloroform, the co-solvent 3-1 is tetrahydrofuran, and the co-solvent. A combination in which 3-2 is ethanol, or a combination in which the bioabsorbable material is polylactide, the solvent 1 is water, the solvent 2 is chloroform, the co-solvent 3-1 is acetone, and the co-solvent 3-2 is ethanol. And so on.

In the above dissolution step, a uniform solution in which the bioabsorbable material is dissolved is prepared by using the bioabsorbable material, the solvent 1, the solvent 2, and the co-solvent 3.
More specifically, as a method for preparing the uniform solution, for example, a bioabsorbable material and a mixed solvent containing the solvent 1, the solvent 2 and the co-solvent 3 (hereinafter, also simply referred to as “mixed solvent”) are mixed. After that, a method of heating can be mentioned. Further, as a method for more easily preparing a uniform solution, for example, a method in which the mixed solvent is preheated and a bioabsorbable material is added to the heated mixed solvent, or a method in which the bioabsorbable material is once dissolved in the solvent 2 is used. , A method of adding the solvent 1 and the co-solvent 3 while heating and the like can also be mentioned.
The above mixing method is not particularly limited, and for example, a known mixing method using a Starla tip, a stirring rod, or the like can be used.

The heating temperature in the melting step is not particularly limited as long as the bioabsorbable material is uniformly melted, but the temperature is lower than the boiling point of any of the solvent 1, the solvent 2 and the co-solvent 3. Is preferable. When heated to a temperature above the boiling point, the compounding ratio of each solvent fluctuates, and the pore size and bulk density of the obtained artificial blood vessel may not be controlled.

In the method for producing an artificial blood vessel of the present invention, a coating step of applying the uniform solution to the surface of a rod-shaped body is then performed.
The rod-shaped body is a member for forming a porous body into a tube shape, and substantially corresponds to the inner diameter of a tube-shaped artificial blood vessel. In the coating process, by using a rod-shaped body made of a metal such as stainless steel or resin-coated stainless steel as the rod-shaped body, a porous body having the skin layer and the porous layer can be formed. Further, by adjusting the type of rod-shaped body and the cooling method, an artificial blood vessel having a skin layer on the inner diameter side and having a pore diameter of a porous layer around the skin layer increasing toward the outer diameter side. Can also be manufactured. On the contrary, it is also possible to manufacture an artificial blood vessel having a skin layer on the outer diameter side and increasing the pore diameter of the porous layer on the inner diameter side of the skin layer toward the inner diameter side.

The method of applying the uniform solution to the surface of the rod-shaped body is not particularly limited, for example, a method of dipping the rod-shaped body into the uniform solution once or a plurality of times, or a cylinder having an inner diameter larger than the diameter of the rod-shaped body. Examples thereof include a method in which the rod-shaped body is arranged in the shaped body and the uniform solution is poured into the gap between the rod-shaped body and the tubular body.
Since the obtained tubular porous body shrinks slightly in the precipitation step, it is easy to extract the rod-shaped body or the tubular body, but the surface of the rod-shaped body or the tubular body is previously slipped by coating or the like. May be given.

In the method for producing an artificial blood vessel of the present invention, a precipitation step is then performed in which a uniform solution on the surface of the rod-shaped body is cooled to precipitate a porous body made of a bioabsorbable material.
By cooling, an insoluble skin layer and a porous layer made of the bioabsorbable material are precipitated. This is because, before the bioabsorbable material is crystallized and precipitated, the bioabsorbable material in a liquid state and each solvent are first phased due to thermodynamic instability at a temperature higher than the temperature at which the bioabsorbable material crystallizes. This is thought to be due to separation (liquid-liquid phase separation).

The cooling temperature in the precipitation step is not particularly limited as long as it can precipitate a porous body made of a bioabsorbable material, but is preferably 4 ° C. or lower, more preferably -24 ° C. or lower. ..
The pore size of the obtained artificial blood vessel is also affected by the cooling rate. Specifically, when the cooling rate is high, the pore diameter tends to be small, and when the cooling rate is slow, the pore diameter tends to be large. Therefore, especially when an artificial blood vessel having a small pore size is obtained, it is conceivable to set the cooling temperature low and cool the blood vessel rapidly.

In the method for producing an artificial blood vessel of the present invention, a freeze-drying step of freeze-drying a porous body made of the obtained bioabsorbable material is then performed.
The conditions for freeze-drying are not particularly limited, and conventionally known conditions can be used. The freeze-drying step may be carried out as it is after the cooling step, but for the purpose of removing various organic solvents used as the solvent, the porous body is previously immersed in ethanol, water or the like to replace it, and then freeze-dried. May be done.

In the method for producing an artificial blood vessel of the present invention, a fibrous nonwoven fabric layer made of a bioabsorbable material having a fiber diameter of 1 to 10 μm and a pore diameter of 3.0 to 100 μm is then formed on the porous body by an electrospinning method. Perform the forming process.
The electric field spinning method is a method in which a solution in which a bioabsorbable material is dissolved is discharged from a nozzle toward a target while a high voltage is applied between the nozzle and the collector electrode. The solution ejected from the nozzle becomes fibrous along the lines of electric force and adheres to the target.

In the method for producing an artificial blood vessel of the present invention, by using a conductive rod-shaped body made of metal as the rod-shaped body, the rod-shaped body can be used as a collector electrode. At this time, the fibrous nonwoven fabric layer can be formed by rotating a rod-shaped body on which a tube-shaped artificial blood vessel is formed and discharging the nozzle while reciprocating the nozzle a plurality of times. As the fibrous nonwoven fabric layer, the same fibrous nonwoven fabric layer as in the artificial blood vessel of the present invention can be used.

The fibrous nonwoven fabric layer is preferably formed by an electrospinning method using a solution in which a bioabsorbable material is dissolved in a solvent (hereinafter referred to as solvent 4) that is slightly insoluble in the bioabsorbable material.
The non-woven fabric layer of the conventional artificial blood vessel is formed by using a solvent that dissolves the bioabsorbable material as a material well. However, when a solvent that dissolves well is used, a non-woven fabric layer having a small fiber diameter and a small pore diameter is easily formed, and the flexibility of the artificial blood vessel is impaired. In the method for producing an artificial blood vessel of the present invention, by using a solvent having a slightly low solubility as a solvent for dissolving a bioabsorbable material, it is possible to easily form a fibrous nonwoven fabric layer having the above fiber diameter and pore diameter, and it is flexible. It can be a tall artificial blood vessel.

The solvent 4 is appropriately selected depending on the bioabsorbable material used. For example, when the bioabsorbable material is poly-ε-caprolactone, hexafluoro-2-propanol, dichloromethane, chloroform, chloroform / methanol mixed solvent and the like can be mentioned. Of these, since the fiber diameter and pore diameter of the fibrous nonwoven fabric layer can be easily adjusted within the above ranges, when the bioabsorbable material is poly-ε-caprolactone, a chloroform / methanol mixed solvent is preferable.

The chloroform / methanol mixed solvent preferably has a mixing ratio (chloroform: methanol) of 1: 9 to 9: 1 in volume ratio.
By setting the mixing ratio of chloroform and methanol in the above range, the fiber diameter and pore diameter of the fibrous nonwoven fabric layer can be easily adjusted in the above range. The mixing ratio of chloroform and methanol is more preferably 7: 3 to 9: 1, and even more preferably 5: 5 to 6: 4.

The solution in which the bioabsorbable material is dissolved in the chloroform / methanol mixed solvent preferably has a concentration of the bioabsorbable material in the solution of 3 to 25% by weight.
By setting the concentration of the bioabsorbable material in the above range, the fibers are less likely to loosen when the fibrous nonwoven fabric layer is formed on the porous layer, and a normal fibrous nonwoven fabric layer can be formed. Further, the fiber diameter and the pore diameter of the fibrous nonwoven fabric layer can be easily adjusted within the above ranges. A more preferable lower limit of the concentration of the bioabsorbable material is 3% by weight, a further preferable lower limit is 4% by weight, a more preferable upper limit is 25% by weight, and a further preferable upper limit is 20% by weight.

INDUSTRIAL APPLICABILITY According to the present invention, it is possible to provide an artificial blood vessel and a method for producing an artificial blood vessel having both high cell infiltration property and strength and flexibility to withstand hemodynamics even when used in a cardiovascular system. ..

This is an enlarged electron micrograph of a cross section of the artificial blood vessel (Example 1) of the present invention. It is an electron micrograph of the non-woven fabric layer of the conventional artificial blood vessel (Comparative Example 1). It is an electron micrograph of the fibrous nonwoven fabric layer of the artificial blood vessel (Example 1) of this invention.

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

(Example 1)
(Manufacturing of artificial blood vessels)
At room temperature of 25 ° C., 0.25 g of L-lactide-ε-caprolactone copolymer (molar ratio 50:50) was used as solvent 1, 0.2 mL of water, 2.5 mL of methyl ethyl ketone as solvent 2, and 3 as co-solvent. By mixing with a mixed solution containing 0.8 mL of acetone and 0.2 mL of ethanol, a heterogeneous solution in which the L-lactide-ε-caprolactone copolymer was not dissolved was obtained.
Then, when the obtained heterogeneous solution was heated to 60 ° C., a homogeneous solution in which the L-lactide-ε-caprolactone copolymer was dissolved was obtained.
A rod-shaped body made of stainless steel coated with fluorine having a diameter of 0.6 mm was placed in a glass tube having an inner diameter of 1.1 mm, and the obtained uniform solution was poured into the gap between the rod-shaped body and the glass tube. In that state, when the mixture was cooled to −30 ° C. by placing it in a freezer, a porous body composed of an L-lactide-ε-caprolactone copolymer was precipitated around the rod-shaped body. After removing the glass tube, the obtained porous body was immersed in a 50 mL ethanol tank at −30 ° C. for 12 hours, and then immersed in a 50 mL water tank at 25 ° C. for 12 hours for washing.
Then, freeze-drying was carried out under the condition of −40 ° C. to obtain a tubular porous body.

On the other hand, a poly-ε-caprolactone polymer (44074-250G manufactured by Aldrich, number average molecular weight: 80000) was dissolved in a mixed solvent of chloroform / methanol (chloroform: methanol = 7: 1 (volume ratio)), and the polymer concentration was 10. A wt% chloroform / methanol solution was prepared. Then, the rod-shaped body in which the tubular porous body was formed on the rotating mandrel was used as a collector electrode, and the obtained chloroform / methanol solution was discharged onto the surface of the porous body using an electric field spinning device. At this time, the chloroform / methanol solution was filled in the two nozzles, and the non-woven fabric layer was formed by reciprocating and discharging the rod-shaped body a plurality of times while rotating the rod-shaped body. The conditions for electric field spinning were a voltage of −30 kV and a nozzle diameter of 22 G.
Finally, the rod-shaped body was pulled out to obtain a tubular artificial blood vessel. When the inner diameter of the obtained artificial blood vessel was measured with a taper gauge (manufactured by Niigata Seiki Co., Ltd., 710A) and the outer diameter was measured with a digital caliper (CD-20CP), the inner diameter was 5.1 mm and the outer diameter was 6.9 mm. there were. Further, an enlarged electron micrograph of a cross section of the obtained artificial blood vessel is shown in FIG.

(Comparative Example 1)
A solution prepared by dissolving a poly-ε-caprolactone polymer (manufactured by Aldrich, (product number) 440744-250G, number average molecular weight: 80000) in hexafluoroisopropanol to adjust the polymer concentration to 10% by weight when forming the fibrous non-woven fabric layer. An artificial blood vessel was obtained in the same manner as in Example 1 except that the conditions for electrospinning were a voltage of −28 kV and a nozzle diameter of 24 G.

(Measurement of fiber diameter and pore diameter of fiber non-woven fabric layer)
Electron micrographs of the fibrous non-woven fabric layer of the artificial blood vessel obtained in Examples and Comparative Examples were taken at a magnification of 2000 (FIGS. 2 and 3). Arbitrary 10 points were selected from the obtained electron micrographs, the fiber diameters were measured, and the average value of these was taken as the fiber diameter of the fibrous nonwoven fabric layer. Next, the pore diameter of the fibrous nonwoven fabric layer was measured in the same manner as the fiber diameter of the fibrous nonwoven fabric layer.

(Measurement of compliance value of artificial blood vessel)
As a pressure imitating the blood vessel pressure, when a repeated beat pressure of 80 mmHg (P ₁ ) -155 mmHg (P ₂ ) is applied to the artificial blood vessel 60 times per minute, the diameter (D ₈₀ ) at 80 mmHg (P ₁ ). ) and 155mmHg _{(P 2)} when the diameter _{(D 155)} the laser (manufactured by Keyence Corporation, measured by LS-9000), was calculated Compliance ans value by the following equation.
Compliance value = (D _155- D ₈₀ ) / D ₈₀ x 1 / (P _2- P ₁ )

According to the present invention, it is possible to provide an artificial blood vessel and a method for producing an artificial blood vessel having both cell infiltration property and strength and flexibility to withstand hemodynamics even when used in a cardiovascular system.

Claims (4)

A porous tubular artificial blood vessel, which is a tubular porous body made of a bioabsorbable material and a fibrous nonwoven fabric having a fiber diameter of 1 to 10 μm and a pore diameter of 3 to 100 μm made of a bioabsorbable material on the porous body. An artificial blood vessel characterized by having a layer. A method for producing a porous tubular artificial blood vessel.
A bioabsorbable material, a solvent 1 having a relatively low solubility in the bioabsorbable material, and a solvent 2 having a relatively high solubility in the bioabsorbable material and incompatible with the solvent 1. And a dissolution step of preparing a uniform solution in which the bioabsorbable material is dissolved by using the solvent 1 and the co-solvent 3 compatible with the solvent 2.
The coating process of applying the uniform solution to the surface of the rod-shaped body, and
A precipitation step of cooling the uniform solution on the surface of the rod-shaped body to precipitate a tubular porous body made of a bioabsorbable material around the rod-shaped body.
A freeze-drying step of freeze-drying the tubular porous body, and
A method for producing an artificial blood vessel, which comprises a fibrous nonwoven fabric layer forming step of forming a fibrous nonwoven fabric layer made of a bioabsorbable material having a fiber diameter of 1 to 10 μm and a pore diameter of 3 to 100 μm on the porous body by an electric field spinning method. .. The method for producing an artificial blood vessel according to claim 2, wherein a fiber non-woven fabric layer forming step is performed using a solution of a bioabsorbable material dissolved in a mixed solvent of chloroform / methanol. The claim is characterized in that the mixing ratio of the chloroform / methanol mixed solvent (chloroform: methanol) is 1: 9 to 9: 1 by volume, and the concentration of the bioabsorbable material in the solution is 3 to 25% by weight. Item 3. The method for producing an artificial blood vessel according to Item 3.