JPH04292169A - Hybrid type artificial pancreas - Google Patents

Abstract

PURPOSE:To obtain the hybrid type artificial pancreas which hardly forms a thrombus, can maintain the functions of pancrea Langerhan's islands over a long period of time and can be implanted into a living body. CONSTITUTION:An immobilized material layer is formed by including and immobilizing the pancrea Langerhan's islands so as to coat at least the inside surface of an artificial blood vessel. This immobilized material layer is constituted of an immobilized material having antithrombic and insulin transmitting properties, by which the hybrid type artificial pancreas is constituted.

Description

[Detailed description of the invention]

0001

[Field of Industrial Application] The present invention relates to a hybrid artificial pancreas for replacing the function of the pancreas for diabetic patients whose pancreatic function is impaired or decreased, and in particular, This invention relates to a hybrid artificial pancreas that is superior and can be implanted into the body.

0002

BACKGROUND OF THE INVENTION Currently, insulin preparations are used for the treatment of diabetes. That is, a method is used in which the required amount of insulin preparation is administered according to the patient's blood glucose concentration, which has been measured in advance. However, since insulin cannot be administered in response to continuous changes in the patient's blood glucose concentration, it is not possible to physiologically control the patient's glucose metabolism. Therefore, it is difficult to prevent complications such as vascular disorders and kidney disorders.

[0003] Therefore, a hybrid artificial pancreas is attracting attention as a new treatment method. The hybrid artificial pancreas is constructed by combining a tissue that secretes insulin, that is, pancreatic islets of Langerhans (hereinafter abbreviated as pancreatic LA islets), and a material that envelops and immobilizes pancreatic LA islets. Various structures are being considered as a hybrid artificial pancreas. For example, Tze et al. reported that Amicon XM-50 (polyacrylonitrile-vinyl chloride copolymer, molecular weight cutoff 50,000
) A hybrid artificial pancreas has been fabricated using a hollow fiber (inner diameter 450 μm) made by the company. This artificial pancreas is used by connecting it to a blood vessel, and insulin secreted from the pancreatic Ra islets is injected into the blood through the hollow fiber wall (W.J.
Tze, F. C. Wong, L. M. Chen an
dS. O'Young, Nature, 264, 4
66 (1976)).

[0004] Also, in JP-A-59-139273,
An insulin-permeable porous membrane is placed in a chamber having a U-shaped blood flow path so as to close the blood flow path,
A hybrid artificial pancreas has been proposed that has a structure in which the pancreatic Ra islets are placed outside a porous membrane so that the pancreatic Ra islets are brought into contact with a blood flow path through the porous membrane.

[0005]

[Problem to be solved by the invention] When the hybrid artificial pancreas created by Tze et al. is connected to a blood vessel and blood is allowed to flow through the hollow fibers, a thrombus is actually formed within the hollow fibers and the blood flow is interrupted. It was easy to be inhibited. As a result, the supply of oxygen and nutrients to the pancreatic Ra islets becomes insufficient, causing the pancreatic Ra islets to die, and the normal secretion of insulin according to blood sugar levels to occur, resulting in the function of the artificial pancreas being impaired. I only got it for a few days.

[0006] Also, in the hybrid artificial pancreas disclosed in JP-A No. 59-139273, thrombi are still formed, and the average patency time of the blood flow path is as short as 21 hours at the longest.
There was a problem that it lacked practicality. Furthermore, since all of the above-mentioned hybrid artificial pancreases were constructed using a container or chamber with a relatively large volume, there was a problem that the overall shape was too large to be implanted in a living body.

An object of the present invention is to provide a hybrid artificial pancreas that is unlikely to cause thrombus formation in the blood flow path, can function as an artificial pancreas for a long period of time, and is suitable for implantation in a living body. There is a particular thing.

[0008]

[Means for Solving the Problems] The hybrid artificial pancreas of the present invention includes an artificial blood vessel and an immobilization material that is provided to cover at least the inner surface of the artificial blood vessel and that comprehensively fixes pancreatic islets. and the immobilization material layer is composed of an insulin-permeable immobilization material having antithrombotic properties. The immobilization material used in the present invention needs to have antithrombotic properties so that thrombi will not form on the surface when immobilized on an artificial blood vessel. Furthermore, the immobilization material must have the property of permeating nutrients such as glucose and insulin secreted from pancreatic islets. Examples of immobilization materials that meet these requirements include:
Photocrosslinked polyvinyl alcohol gel, isopropyl acrylamide copolymer gel, agarose gel, agarose decomposition product gel, etc. are used.

Photo-crosslinked polyvinyl alcohol gel is obtained by gelling photo-crosslinkable polyvinyl alcohol in which a photosensitive functional group, such as a styrylpyridinium group or a styrylquinolium group, is bonded to polyvinyl alcohol. Crosslinkable polyvinyl alcohol is already commercially available, and can be obtained from Toyo Gosei Co., Ltd., for example. Since this gel is highly flexible, it can sufficiently follow the movement of the artificial blood vessel. The degree of polymerization of the photocrosslinkable polyvinyl alcohol is preferably 100 or more and 5000 or less. Photo-crosslinkable polyvinyl alcohol with a polymerization degree of less than 100 is difficult to obtain sufficient gel mechanical strength, and it is somewhat difficult to synthesize polyvinyl alcohol with a polymerization degree of more than 5000, and its aqueous solution has too high a viscosity, making it difficult to operate. This is because they tend to be lacking.

Isopropylacrylamide copolymer gel is a gel obtained by copolymerizing isopropylacrylamide with a copolymerizable monomer. As the copolymerizable monomer, butyl methacrylate and 2-hydroxyethyl methacrylate are preferred. The isopropylacrylamide copolymer has a low-temperature critical solution temperature (LCST) near room temperature, and is in a solution state at a temperature lower than LCST and a gel state at a higher temperature.
It is a polymer whose state can be reversibly changed by temperature changes. Therefore, pancreatic La islets can be dispersed at a temperature lower than that of LCST (in a solution state) and gelatinized by raising the temperature to entrap and immobilize pancreatic La islets. In this case, when the copolymer is used by implanting it in the body, LCST
must be below 37°C. For example, the LCST of a polymer obtained by copolymerizing 30 mol% of 2-hydroxyethyl methacrylate is 17°C. This copolymer is preferred for entrapping immobilization of pancreatic islets.

An example of a method for polymerizing the above copolymer having an LCST of 17°C will be explained. Isopropylacrylamide 70 mol%, 2-hydroxyethyl methacrylate 3
0 mol% and a polymerization initiator (e.g., 2,2-azobisisobutyramide) were dissolved in dioxane, and after degassing and sealing the tube,
Radical polymerization is carried out at 70°C for about 1.5 hours. After that,
A copolymer can be recovered by dropping the polymerization solution into hot water, and a polymer can be obtained by freeze-drying the copolymer. Agarose gel and agarose decomposition product gel are
These are gels of agarose and agarose decomposition products, respectively. Agarose is usually contained in agar, and an agarose decomposition product can be obtained by decomposing the agarose with an acid or the like.

[0012] If the antithrombotic properties of the above-mentioned immobilization material are insufficient, it is necessary to add an anticoagulant. The anticoagulant is chemically or physically applied to the immobilization material in a way that does not lose its own activity. As the anticoagulant, for example, heparin, urokinase, etc. are used. Artificial blood vessels are cylindrical in shape, with an inner diameter of about 3 to 15 mm, and a thickness of several μm to several mm. You may use any one, such as a completely cylindrical one.

[0013] In mesh-shaped or porous artificial blood vessels, the meshes and pores of the mesh are completely filled with the immobilizing material, and at the same time, the inner surface of the artificial blood vessel is immobilized so that the artificial blood vessel itself does not come into contact with blood. Must be completely covered with material. Pancreatic Ra islets are comprehensively immobilized on the covered immobilization material. In this case, the pancreatic islets may be fixed to the fixing material located on either the outer surface or the inner surface of the artificial blood vessel, or to the fixing material located on both. This is because even if the pancreatic islets are immobilized on the outer surface of the artificial blood vessel with an immobilizing material, the produced insulin will permeate through the immobilizing material layer and be injected into the blood vessel.

[0014] In addition, in a completely cylindrical artificial blood vessel without holes, the inner surface of the artificial blood vessel is completely covered with the fixing material so that the artificial blood vessel itself does not come into contact with blood, and the pancreatic islets are covered with this coating. It is comprehensively immobilized in the above-mentioned immobilization material. When pancreatic islets are immobilized on the outer surface of a completely cylindrical artificial blood vessel with no holes, it becomes impossible to quickly control the release of insulin in response to changes in blood sugar levels, and in some cases, the supply of nutrients to pancreatic islets becomes difficult. This is undesirable because it causes insufficient islets in the pancreas and death.

[0015] The artificial blood vessel may be made of any material as long as it is capable of immobilizing the immobilization material on its surface. For example, commonly used polyester, polytetrafluoroethylene, or the like may be used. In the present invention, pancreatic islets isolated from humans, cows, pigs, dogs, hamsters, mice, etc. can be used as appropriate. As an isolation method, for example, a method is used in which the excised pancreas is digested with collagenase for a certain period of time, and then fractionated by specific gravity centrifugation to recover pancreatic islets.

A typical example of the manufacturing method of the present invention is shown below. For photocrosslinked polyvinyl alcohol gels, the photocrosslinkable polyvinyl alcohol was
It is preferably dispersed in an aqueous solution containing medium components such as a MEM solution at a concentration of 1 to 50% by weight, more preferably 2 to 30% by weight. After heating and melting this dispersion liquid, it is cooled to 40° C. or lower, and then the collected pancreatic islets are dispersed. The obtained dispersion is applied to the artificial blood vessel with something like a spatula to completely cover the artificial blood vessel, and then it is gelled by irradiating it with light to coat the surface of the artificial blood vessel several tens of μm to several mm. It is possible to obtain a hybrid artificial pancreas with a gel coating of a certain thickness.

In the case of isopropylacrylamide copolymer gel, the isopropylacrylamide copolymer is
It is preferably dispersed in an aqueous solution containing medium components such as agle's MEM solution at a concentration of 1 to 50% by weight, more preferably 2 to 30% by weight. This dispersion liquid is stirred for about one week in a constant temperature bath at a temperature below LCST to dissolve it. The recovered pancreatic islets are dispersed in this. The resulting dispersion is applied to the artificial blood vessel with, for example, a spatula to completely cover the artificial blood vessel, and then LC
A hybrid artificial pancreas having a gel coating with a thickness of several tens of μm to several mm on the surface of the artificial blood vessel can be obtained by gelling the artificial blood vessel by heating it to a temperature higher than ST.

In the case of agarose gel or agarose decomposition product gel, the agarose or agarose decomposition product is Ea
It is preferably dispersed in an aqueous solution containing medium components such as GL's MEM solution at a concentration of 1 to 30% by weight, more preferably 2 to 20% by weight. After heating and melting this dispersion liquid, it is cooled to a temperature of around 40° C., and the collected pancreatic islets are dispersed therein. The obtained dispersion is applied to the artificial blood vessel with a spatula to completely cover the artificial blood vessel, and then it is cooled to gel, so that it is coated on the surface of the artificial blood vessel to a thickness of several tens of μm. It is possible to obtain a hybrid artificial pancreas having a gel coating of several mm.

[0019]

[Operation] Since the antithrombotic immobilizing material layer is provided to cover at least the inner surface of the artificial blood vessel, the formation of blood clots within the artificial blood vessel is prevented. A fixation material layer is provided to cover at least the inner surface of the artificial blood vessel, and the pancreatic islets are encased and fixed in the fixation material layer. It is easy to embed into.

[0020]

[Explanation of Examples] The present invention will be further clarified by describing non-limiting examples and comparative examples of the present invention.

Example 1 Photocrosslinkable polyvinyl alcohol (degree of polymerization: 500, degree of saponification: 100%, proportion of styrylpyridinium substituents;
1.4 mol%, manufactured by Toyo Gosei Kogyo Co., Ltd.) was dissolved in Eagle's MEM solution so that the polymer concentration was 10% by weight. Further, an artificial blood vessel made of polyester mesh having an inner diameter of 8 mm, a length of 3 cm, and a wall thickness of about 500 μm was prepared, and the artificial blood vessel was immersed in the polymer solution and sterilized by heating at 121° C. for 20 minutes in an autoclave. Next, the artificial blood vessel was taken out from the polymer solution and irradiated with light for about 30 seconds using a spot light source device HX-200S (manufactured by Avic Shokai) to create a film of photocrosslinked gel on the surface of the artificial blood vessel. As a result, the wall thickness of the artificial blood vessel is approximately 1
It became mm.

Separately, photocrosslinked polyvinyl alcohol (degree of polymerization: 500, degree of saponification: 100%, proportion of styrylpyridinium substituents: 1.4 mol%) was mixed with Eagle so that the polymer concentration was 10% by weight. 's MEM
In addition to the solution, the mixture was heated in an autoclave at 121°C for 20 minutes to dissolve the photocrosslinkable polyvinyl alcohol at the same time as sterilization, and then kept at 40°C. Approximately 1,000 pancreatic islets isolated from dog pancreas by collagenase treatment were added to 1 ml of this photocrosslinkable polyvinyl alcohol solution.
A solution dispersed in about 0.1 ml of e's MEM solution was added and stirred. Next, this stirred solution was applied to the outside of the artificial blood vessel on which the photocrosslinked gel coating had been formed using a spatula. Next, in the same manner as in the formation of the photocrosslinked gel film, light was irradiated to gel the photocrosslinkable polyvinyl alcohol, thereby forming a photocrosslinked gel film with a thickness of about 1 mm. A hybrid artificial pancreas was manufactured.

Example 2 30 g of a mixture of 70 mol % isopropylacrylamide and 30 mol % 2-hydroxyethyl methacrylate
and polymerization initiator 2,2-azobisisobutyramide 0.2
Dissolve 13 g in 60 ml of dioxane, and after degassing and sealing the tube,
Radical polymerization was performed at 70°C for 1.5 hours. After polymerization, the copolymer was recovered by dropping the polymerization solution into hot water, and the copolymer was freeze-dried to obtain isopropylacrylamide-2.
-Hydroxyethyl methacrylate (30 mol%) copolymer was obtained.

Obtained isopropylacrylamide-2
-Hydroxyethyl methacrylate (30 mol%) copolymer was added to Eagl so that the polymer concentration was 5% by weight.
It was added to e's MEM solution and stirred for one week in a constant temperature bath at 4°C to dissolve. About 1,000 pancreatic islets isolated from dog pancreas by collagenase treatment were added to about 0.1 ml of Eagle's MEM solution to 1 ml of the obtained solution.
The mixture was added under cooling and stirred. Next, the stirred solution was poured into a four
The hybrid artificial pancreas of Example 2 was manufactured by applying it to the entire inner surface of a fluoroethylene artificial blood vessel with a spatula and gelling it by heating it to 37° C. to form a gel coating with a thickness of about 1 mm.

Comparative Example 1 Photocrosslinkable polyvinyl alcohol (degree of polymerization: 500, degree of saponification: 100%, proportion of styrylpyridinium substituents;
1.4 mol%) was added to Eagle's MEM solution so that the polymer concentration was 10% by weight, and heated in an autoclave at 121°C for 20 minutes to dissolve the photocrosslinkable polyvinyl alcohol at the same time as sterilization. It was kept at 40°C. Approximately 1,000 pancreatic islets isolated from dog pancreas by collagenase treatment were added to 1 ml of the resulting solution.
s Dispersed in about 0.1 ml of MEM solution was added and stirred. This stirred solution was applied to the outside of a hollow fiber (inner diameter: 450 μm) made of Amicon XM-50 (polyacrylonitrile-vinyl chloride copolymer, molecular weight cut off 50,000), and irradiated with light in the same manner as in Example 1. , by gelling photocrosslinkable polyvinyl alcohol, the thickness is approximately 1.
A hybrid artificial pancreas of Comparative Example 1 was manufactured in which a gel coating of mm thick was formed.

Transplantation test The hybrid artificial pancreases of Examples 1 and 2 and Comparative Example 1 were connected to the abdominal aorta of a dog by suturing (each example was carried out on 3 dogs), and the hybrid artificial pancreas was gradually removed over time. The pancreas was removed, and thrombus formation and viability of pancreatic islets were observed. Thrombus formation was visually observed. In addition, the viability of pancreatic Ra islets was evaluated as follows. First, the removed hybrid artificial pancreas was fixed in a 10% neutral formalin solution, washed with water, and immersed in 60% and 70% alcohol. Next, Tissue Tech III (
Paraffin embedding was performed using Miles Sankyo Co., Ltd.). Further, sections were prepared using a microtome, stained with hematoxylin and eosin, and viability was observed using a microscope.

[0027]

[Table 1]

As is clear from Table 1, even after 14 days, almost no thrombus was formed in the hybrid artificial pancreas of Examples 1 and 2, and the pancreatic islets remained well alive. I understand. On the other hand, in the hybrid artificial pancreas of Comparative Example 1, a blood clot was already formed and occluded on the 3rd day after installation, and pancreatic islets died every 3rd, 7th, and 14th day. It can be seen that the number of

[0029]

According to the present invention, since at least the inner surface of the artificial blood vessel is coated with an immobilizing material having antithrombotic properties, a blood clot is not formed within the artificial blood vessel when connected to a biological blood vessel. It is possible to reliably prevent this from occurring. Also,
Since pancreatic Ra islets are entrappingly immobilized in an immobilized material that is permeable to insulin, insulin can be rapidly released into the blood in response to changes in blood sugar levels. Furthermore, since the pancreatic Ra islets are comprehensively immobilized using the immobilization material, direct contact between the pancreatic Ra islets and immunocompetent cells can be prevented, and therefore the function of the pancreatic Ra islets can be maintained for a long period of time. ing.

[0030] Furthermore, the hybrid artificial pancreas of the present invention has a structure in which a fixing material layer is formed to cover at least the inner surface of the artificial blood vessel. Since it does not require a container or chamber, it can not only be easily connected to blood vessels in vivo, but also easily implanted in vivo. Therefore, the present invention makes it possible to realize an implantable hybrid artificial pancreas.

Claims (1)

[Claims] 1. An artificial blood vessel, and an immobilization material layer provided to cover at least the inner surface of the artificial blood vessel and entrapping pancreatic Langerhans islets, the immobilization material layer comprising: A hybrid artificial pancreas composed of an immobilized material that has antithrombotic properties and is insulin permeable.