JP2002011090A - Absorbing vital material and its manufacturing method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve the strength at the trimming and the strength in vivo environment in the absorbing vital material and delays sufficiently the absorbing speed in vivo. SOLUTION: This is an absorbing vital material that contains calcium and is made of chitin derivative cross-linked by epoxy compound.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

[0001] The present invention relates to an absorbable biomaterial to be used for filling bone tissue and cartilage defects lost due to diseases, accidents, old age, etc., and a method for producing the same.

[0002]

2. Description of the Related Art Conventionally, as an absorbable biomaterial, carboxymethyl chitin (hereinafter referred to as C) thermally crosslinked without using a chemical crosslinking agent has been used.
In some cases, calcium phosphate-based materials such as granular hydroxyapatite and tricalcium phosphate (hereinafter abbreviated as TCP) were dispersed in a porous matrix of M chitin). Since this resorbable biomaterial is a material such as a sponge as a whole, it was possible to trim it with scissors or the like in accordance with the shape of the bone defect to be filled, and to fit the shape of a predetermined portion and pack it. . Therefore, there is no risk of falling off from the filling point,
Permeation and absorption of a large amount of liquid components into the pores of the CM chitin matrix while the granules of the calcium phosphate-based material are retained by the CM chitin matrix during the unstable period until a full-scale bone formation reaction occurs To provide an environment in which various cells are stored. Under this environment, the granules of the calcium phosphate-based material cause new bone, and the CM chitin is replaced with new bone in parallel with the degradation and absorption of CM chitin.

Further, as a relatively new biomaterial recently presented at a conference, a gel-like substance obtained by cross-linking CM chitin into which calcium salt has been introduced with divinylsulfone is immersed in a simulated body fluid to obtain a surface. Has been reported to be capable of forming apatite ("Spontaneous Form
ation of Bonelike Apatite on Carboxymethyl-Chitin
Gel in Simulated Body Fluid "Sixth World biomateri
als Congress Transaction). No specific use is mentioned for this CM chitin.

[0004]

Among the above-mentioned conventional bioabsorbable biomaterials, the former is capable of promoting efficient new bone replacement by retaining calcium phosphate granules. Due to the low mechanical strength, great care had to be taken during trimming and filling. Furthermore, the rate of absorption into the living body in the in-vivo environment may be relatively high, and in such a case,
Bone formation tended to be inactive.

On the other hand, the biomaterials presented at the above-mentioned conferences are:
Consisting of CM chitin cross-linked with divinylsulfone, such materials do not provide sufficiently large mechanical strength and sufficiently slow bioabsorption rates.

An object of the present invention is to solve the above-mentioned problems of the prior art, to improve the strength at the time of trimming and the strength in a living body environment, and to make the absorption rate in a living body sufficiently slow. It is an object of the present invention to provide an absorbent biomaterial and a method for producing the same.

[0007]

Means for Solving the Problems In order to solve the above problems, the absorbent biomaterial of the present invention is characterized by comprising a chitin derivative containing calcium and crosslinked by an epoxy compound.

According to this structure, the chitin derivative containing calcium and cross-linked by the epoxy compound has extremely excellent elasticity and has shape retention during trimming or in a living body environment. Very easy to handle during surgery. In addition, since the chitin derivative has a sufficiently low absorption rate in the living body, bone formation can be activated. In addition, since calcium ions remain in the absorbable biomaterial, they become nuclei that cause calcification in the vicinity and in the material, and can promote early bone repair. As a result, it is possible to maximize the amount of bone repair.

[0009] As a method for producing the absorbable biomaterial, the production method of the present invention comprises dissolving a chitin derivative having at least one of a carboxymethyl group, a sulfate group and a phosphate group in a calcium salt aqueous solution, The method is characterized by including a step of pouring a solution obtained by adding an epoxy compound to the solution to a mold and freeze-drying, and a step of heat-treating the freeze-dried molded product.

According to this structure, the chitin derivative having at least one of a carboxymethyl group, a sulfate group and a phosphate group as a functional group is water-soluble, so that calcium can be easily dissolved by dissolving the chitin derivative in a calcium salt aqueous solution. Can be introduced.

[0011]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, embodiments of the present invention will be described in detail.

The absorbable biomaterial of the present invention comprises a chitin derivative containing calcium and crosslinked with an epoxy compound. Since the resorbable biomaterial is a material such as sponge, it can be trimmed to a desired shape with scissors or the like according to the shape of the bone defect to be filled, and can be packed in a predetermined location.

As the chitin derivative, any one of carboxymethyl group, sulfate group and phosphate group such as carboxymethyl chitin, chitin sulfate, chitin phosphate, carboxymethyl sulfate chitin and carboxymethyl phosphate chitin,
Alternatively, there are water-soluble chitin derivatives having two or more kinds of functional groups.

The epoxy compounds include ethylene glycol diglycidyl ether, polyethylene glycol diglycidyl ether, glycerol polyglycidyl ether, polyglycerol polyglycidyl ether,
Examples include compounds in which two or more epoxy groups such as sorbitol polyglycidyl ether are introduced into a molecule.

Since the resorbable biomaterial is in the form of a sponge as described above, it can carry a calcium phosphate-based material and / or a physiologically active substance having an ability to induce bone formation. Thereby, bone formation can be made more active. Biologically active substances are proteins involved in biochemical reactions, such as by binding to cell surface receptors, and are used to differentiate undifferentiated mesenchymal cells present in bone tissue into osteoblasts. Bone Morphogenetic Protein (BMP) and Transforming Growth Factor β (TGF
β) or fibroblast growth basic factor (bFGF) or Ins
There are functional proteins that indirectly induce bone formation, such as ulin-like growth factor (IGF). It is also possible to use a chemically synthesized (recombinant) bone morphogen as a physiologically active substance.

[0016] Such an absorbent biomaterial is produced as follows. That is, a chitin derivative having at least one of carboxymethyl group, sulfate group, and phosphate group, or a chitin derivative having two or more functional groups is dissolved in an aqueous solution of calcium salt, and an epoxy compound is added to the solution and stirred. And freeze-dried. Then, the freeze-dried molded product is heat-treated.

As the calcium salt, a water-soluble calcium salt such as calcium hydroxide or calcium chloride can be used.

Preferably, the concentration of the chitin derivative in the solution obtained by dissolving the chitin derivative in an aqueous calcium salt solution is 20 wt% or less. This is because it may be difficult to prepare an aqueous solution at a concentration of more than 20 wt%.

The amount of the epoxy compound is preferably 3 to 30% based on the weight of the chitin derivative.
If the added weight of the epoxy compound is less than 3%, the effect of improving the mechanical strength and slowing the absorption rate in the living body tends to decrease, while if it exceeds 30%, the living body may cause a foreign substance reaction. is there.

After the epoxy compound is added to the solution and stirred, powder of a calcium phosphate-based material and / or a physiologically active substance may be further added. By these additions, functions such as bone formation ability can be improved.

The weight of the powder of the calcium phosphate-based material or the physiologically active substance is preferably 10% to 200% with respect to the weight of the solution containing the epoxy compound. If it is less than 10%, the effect of improving the function of bone formation tends to be small, while if it exceeds 200%,
This is because the resulting absorbable biomaterial becomes brittle and may easily lose its shape.

Further, after the heat treatment, it is preferable that unreacted calcium salts and epoxy compounds are washed off and then freeze-dried again. This is because the remaining monomer components and the like of the epoxy compound can be removed in the washing step, and the risk of foreign substance reaction in the living body can be reduced.

The heat treatment temperature is 110 ° C. to 16 ° C.
Preferably it is 0 ° C. At 110 ° C., there is a tendency that crosslinking takes a long time and the production cannot be performed efficiently.
In the heat treatment at 60 ° C. or higher, chitin derivative molecules are reduced in molecular weight, and as a result, in the early stage of implantation, a strong inflammatory reaction may be caused due to a large amount of low molecular components being eluted.

Next, specific examples and comparative examples of the present invention, experimental examples using these examples and comparative examples, and the results of the experiments will be described. Examples Absorbable biomaterials (Example products) of the present invention were prepared in the following order. CM chitin powder having a carboxymethylation degree of 75% was converted to Ca (O
H) Dissolved in ₂ aqueous solution to prepare a 5 wt% solution.

1 to 30 watts based on the weight of CM chitin
A t% epoxy compound-based chemical crosslinking agent, ethylene glycol polyglycidyl ether (product name: Denacol, manufactured by Nagase Kasei Kogyo Co., Ltd.) was added and stirred.

Α-TCP powder was mixed with an equal weight or 1/5 times the weight of the above solution, and the mixture was stirred with a stirrer.

An aqueous solution not mixed with α-TCP powder was also prepared. An appropriate amount of the above solution is poured into a metal, hard glass or polypropylene container,
(−80 ° C.), and shaped into a shape having a diameter of 4 mm and a thickness of 2 to 3 mm. The above molded product was freeze-dried for 24 hours. The dried product was subjected to a vacuum heat treatment at 110 ° C. for 2 hours to complete the reaction of the crosslinking agent. The above was immersed in distilled water to wash the residual crosslinking agent and Ca (OH) ₂ . (Change water every 8 hours for 24 hours). Freezing and freeze-drying were performed again. Comparative Example An absorbent biomaterial as a comparative example product was prepared in the following order. CM chitin powder having a carboxymethylation degree of 75% was dissolved in distilled water to prepare a 5 wt% aqueous solution. An appropriate amount of the above aqueous solution is poured into a metal, hard glass or polypropylene container,
(−80 ° C.), and formed into a shape having a diameter of 4 mm and a thickness of 2 to 3 mm. The above molded product was freeze-dried. The dried product was subjected to a vacuum heat treatment at a temperature of 160 ° C. for 24 hours to perform thermal crosslinking. The above was immersed in distilled water for washing, and then frozen and freeze-dried again.

An experiment was performed using the product of the example and the product of the comparative example in the following manner. Experimental Example 1 A compressive strength experiment in a dry state was performed to confirm the strength characteristics of the absorbent biomaterial when trimming into a desired shape. It was compressed until the thickness in the compression direction became half, and the stress value at that time was defined as the compressive strength. Experimental Example 2 Assuming a case where an absorbable biomaterial is embedded in a living tissue,
In order to confirm the strength characteristics of the material, a compressive strength experiment in a water-containing state was performed.

After the absorbent biomaterial was immersed in distilled water for 5 minutes, it was taken out of the water and compressed until the thickness in the compression direction became half, and the stress value at that time was taken as the compressive strength. Experimental Example 3 Calcium ions remain in the absorbable biomaterial, become nuclei causing calcification in the vicinity and in the material, and promote early bone repair. Therefore, the retention rate was determined by the following procedure as an index of the amount of stored calcium ions in the absorbent biomaterial.

The absorbent biomaterial was immersed in distilled water for 24 hours, and the amount (A) of eluted calcium ions was measured by ICP. Furthermore, after the immersed absorbent biomaterial was dissolved in an aqueous solution of sodium hydroxide, the amount of calcium ions (B) in the solution was measured by ICP. The calcium ion retention was calculated by the following equation. Retention rate of calcium ion (%) = A / (A + B) × 10
0 Experimental Example 4 In order to compare the degradability of chitin derivatives in vivo,
Enzymatic degradation was confirmed using lysozyme, an enzyme that mainly degrades chitin derivatives in vivo.

[0031] Phosphate buffer (p
H: The absorbent biomaterials of Example and Comparative Examples were immersed in 7.4) for 24 hours, and the weight loss was measured. Residual rate as an indicator of enzymatic degradability is the weight before immersion (α) and the weight after immersion
It was calculated by the following equation using (β).

Residual rate of chitin derivative (%) = (β / α) × 100 Experimental Example 5 An example product mixed with α-TCP powder (average particle diameter 10 μm) and a comparative example product were rabbit tibia Bone defect formed in diaphysis (animal experiment 1), femoral joint surface (animal experiment 2)
Implanted bioabsorbable biomaterial in the bone formed in the cartilage defect,
The bone was repaired over time.

In each of the examples containing no α-TCP and those containing α-TCP, the epoxy compound was added at 5% by weight based on the weight of CM chitin. Also, α-TC
In the example product containing P, α-TCP was added in an amount equal to the weight of the CM chitin / epoxy compound solution.

The procedure of this animal experiment will be described below. 1. Under general anesthesia, the tibial shaft and femoral knee joint surface of a rabbit (New Zealand white, 12 weeks old, male) were exposed. 2. A hole having a diameter of 4 mm and a depth of 10 mm was formed by drilling in the longitudinal direction of the femur from the exposed portion of the tibial shaft and the center of the joint surface. Here, the reason why the diameter is set to 4 mm is to set a size of 4 mm, which exceeds the natural healing limit of the rabbit cartilage layer, and to clearly grasp the cartilage repair effect of the example product and the comparative example product. 3.Example product adjusted to 4mm in diameter and 10mm in length, α-
An example product and a comparative example product mixed with TCP powder were embedded respectively. 4. After implantation of the absorbable biomaterial, the joint capsule and skin were sutured. In addition, the thing which sutured as it was, without embedding an absorptive biomaterial after forming a hole was made into the natural healing (blank) example. In addition, a case in which no treatment was performed without forming a hole was regarded as a non-treatment example. Experimental Results Table 1 shows the results of the tests of Experimental Examples 1 to 4.

[0035]

[Table 1]

As is clear from Table 1, the strength in the dry state of the product of the example is higher than that of the product of the comparative example. As for the amount of the epoxy compound added, up to 20 wt%, the higher the added amount, the higher the strength. showed that. Also, the higher the amount of α-TCP added, the higher the strength. From the viewpoint of operability at the time of trimming, it is understood that it is desirable to increase the addition amount of the epoxy compound and α-TCP. However, even if the epoxy compound is added in an amount of 20% or more, the strength does not increase and 20 to 20%.
Extreme values tend to be between 30%.

The compressive strength when containing water shows the same tendency as when drying. It has been found that it is desirable to increase the amount of the epoxy compound to be added up to 20% by weight also in the strength in a living body environment. In addition, after measuring the compressive strength of all the products of Examples, when the compressive stress was removed, it was confirmed that the original shape was completely restored when the compressive stress was removed. This restoring force contributes to conforming to the shape of the defect site when the absorbent biomaterial is implanted.

With respect to the calcium retention and the chitin derivative residual rate, when the cross-linking agent is added up to 5 wt%, the rate increases as the addition amount increases, but when the addition amount exceeds 5 wt%, the addition amount increases. The rate change was small.

Regarding the (chitin derivative) residual rate as an index of the absorption rate of the absorbable biomaterial in the living body, the results of all the examples were slower than those of the comparative examples crosslinked by thermal crosslinking. Was.

Comprehensively considering the results of Experimental Examples 1 to 4, the amount of epoxy compound added was 20 to 30 wt.
% Is particularly preferred.

Next, the results of Experimental Example 5 are shown in Tables 2 to 4. In these tables, the sample a) was obtained by the sample 3 in Table 1, the sample b) was obtained by the sample 8 in Table 1 containing the α-TCP, and the sample c) was obtained by the comparative example described above. Samples 9 and d) in Table 1 were blanks (examples of natural healing defect) which were sewn as they were without embedding an absorbable biomaterial after forming a hole in bone. No formation was performed and no treatment was performed.

[0042]

[Table 2]

[0043]

[Table 3]

[0044]

[Table 4]

As is apparent from Table 2, in a large defect part which is reported to be difficult to heal naturally, see [Sample d blank (example of natural healing defect)], Sample a) Example product and Sample b) α-TCP In the containing example product, sample c) leads to new bone formation at an extremely early stage as compared with the comparative example product,
The state of osteoclast was achieved, and finally cortical bone regeneration equivalent to the bone thickness of the sample e) untreated sample was confirmed.

As can be seen from Table 3, the samples a) and b) α-TC
In the example product containing P, the sample c) led to early osteogenesis of cancellous bone and subchondral bone in the joint as compared with the comparative example product. As is clear from Table 4, the cartilage layer containing a large amount of hyaline cartilage at the same time. Playback was also confirmed.

The cartilage tissue is a mixture of glass cartilage and fibrous cartilage, and a state containing a large amount of glass cartilage can be said to be a more normal healing.

[0048] In Tables 2 to 4, the reason that the value of the sample e) untreated example slightly changed at 2, 4 and 8 weeks is due to the difference between individuals in rabbits and the degree of growth. . Further, in the eighth week of Table 3, the value of the α-TCP containing example product was larger than the value of the non-treated example because the tissue was formed excessively first in the process of tissue repair, and thereafter, It is common to settle down to an appropriate amount, and the value at the 8th week is the stage at which the tissue is excessively formed.

[0049]

As described above, according to the absorptive biomaterial of the present invention, a chitin derivative containing calcium and cross-linked by an epoxy compound has extremely excellent elasticity, and can be used in trimming or in an in vivo environment. Since it has a shape retention property, intraoperative handling is very easy. In addition, since the chitin derivative has a sufficiently low absorption rate in the living body, bone growth can be activated. In addition, since calcium ions remain in the absorbable biomaterial, they become nuclei that cause calcification in the vicinity and in the material, and can promote early bone repair. As a result, it is possible to maximize the amount of bone repair.

Further, according to the method for producing an absorbent biomaterial, a chitin derivative having at least one of a carboxymethyl group, a sulfate group and a phosphate group as a functional group is water-soluble and can be dissolved in a calcium salt aqueous solution. , Calcium can be easily introduced.

Claims (8)

[Claims] 1. An absorbent biomaterial comprising a chitin derivative containing calcium and crosslinked by an epoxy compound. 2. The absorbable biomaterial according to claim 1, wherein the chitin derivative supports a calcium phosphate-based material and / or a physiologically active substance. 3. A chitin derivative having at least one of a carboxymethyl group, a sulfate group and a phosphate group as a functional group is dissolved in an aqueous solution of calcium salt, and a solution obtained by adding an epoxy compound to the solution is poured into a mold and freeze-dried. A method for producing an absorbable biomaterial, comprising: a step of subjecting the freeze-dried molded product to a heat treatment. 4. The method for producing an absorbable biomaterial according to claim 3, wherein the weight of the epoxy compound is 3 to 30% based on the weight of the chitin derivative. 5. The method according to claim 3, further comprising adding a calcium phosphate-based material and / or a powder of a physiologically active substance after adding the epoxy compound to the solution.
A method for producing the absorbable biomaterial according to the above. 6. The method according to claim 5, wherein the weight of the calcium phosphate-based material and / or the physiologically active substance is 10 to 200% by weight based on the weight of the solution to which the epoxy compound is added. A method for producing an absorbable biomaterial. 7. The method for producing an absorbable biomaterial according to claim 3, wherein after the heat treatment, unreacted calcium salts and epoxy compounds are washed and removed, and then freeze-dried again. 8. The method for producing an absorbent biomaterial according to claim 3, wherein said heat treatment temperature is 110 ° C. to 160 ° C.