JP3592920B2 - Method for producing organic-inorganic oriented composite material - Google Patents

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a method for producing an organic-inorganic oriented composite material comprising collagen and calcium phosphate. Such an organic-inorganic oriented composite material has a similar composition to a living body, is a molded product of a hard tissue material compatible with the living body, and is used as an artificial bone or the like.
[0002]
[Prior art]
Conventional biomaterials to be implanted into living bodies made of inorganic materials have low bone replacement and tissue reconstruction ability due to insufficient osteoconductivity or cell activity of inorganic materials, making it difficult to obtain sufficient medical effects. Met. In addition, when only an organic material is used, the strength is low and adhesion to surrounding tissues occurs, and reconstruction of a living tissue such as a bone tissue is delayed in the tissue-guided regeneration method.
[0003]
As a solution to this problem, Japanese Patent Application Laid-Open No. Hei 7-101708 discloses that a mixed solution obtained by adding phosphoric acid to a collagen solution is gradually added to a suspension of calcium hydroxide, and the resulting precipitate is filtered and dried. There is disclosed a technique for obtaining a molded article having a Young's modulus of 2 GPa to 100 MPa and a physical property similar to that of a biological bone (composite of apatite which is an inorganic substance and collagen which is an organic substance) by pressure molding. Also, 12th J.M. -K. Seminar Ceram. 485 (1995) discloses that a hydroxyapatite / collagen complex having a Young's modulus of 5.5 Pa can be obtained by a similar technique.
[0004]
These techniques reduce the Young's modulus to a level close to that of living bone by complexing calcium phosphate (apatite) with collagen, but the Young's modulus of living bone varies from site to site and ranges from 4 GPa to 30 GPa. Are distributed. Therefore, according to the conventional technique, a composite having a Young's modulus similar to that of soft living bone can be obtained, but a composite having a Young's modulus similar to that of hard living bone cannot be obtained.
[0005]
[Problems to be solved by the invention]
The fact that the composite obtained by the conventional technique has a Young's modulus as low as that of soft living bone, although it is compositionally similar to that of living bone, is because the orientation of this composite is Probably because it is worse than bone.
Accordingly, an object of the present invention is to provide a method for producing an organic-inorganic oriented composite material that can obtain a composite having excellent orientation of collagen and calcium phosphate.
[0006]
[Means for Solving the Problems]
As a result of the inventor's intensive studies, in the prior art, a mixed solution obtained by adding phosphoric acid to a collagen solution (about pH 3) is gradually added to a suspension of calcium hydroxide (about pH 12). Therefore, it has been found that a large change in the pH of the reaction system from an alkali side to an acidic side is a cause of hindering the orientation of the complex. Therefore, instead of adding the other solution to one solution, if a method of simultaneously dropping both solutions is adopted, it is thought that the pH can be controlled and a composite with excellent orientation can be obtained, The present invention has been completed.
[0007]
That is, the present invention provides the following configurations.
(1) A method for producing an organic-inorganic oriented composite material comprising collagen and calcium phosphate, wherein an aqueous solution of phosphoric acid containing collagen and an aqueous solution of calcium salt are simultaneously dropped in a reaction vessel to form a mixture of calcium phosphate and collagen. A method for producing an organic-inorganic oriented composite material, which comprises subjecting the obtained precipitate to pressure molding after coprecipitation.
(2) The method for producing an organic-inorganic oriented composite material according to (1), wherein the pH of the reaction solution in the reaction vessel is in the range of 7 to 11, and the range of change is within 1 or less.
(3) The method for producing an organic-inorganic oriented composite material according to (1) or (2), wherein pressure molding is performed while applying ultrasonic waves.
(4) The method for producing an organic-inorganic oriented composite material according to any one of (1) to (3), wherein pepsin-treated collagen is used as the collagen.
(5) The method for producing an organic-inorganic oriented composite material according to any one of (1) to (4), wherein the pressure molding is performed in a temperature range of 0 ° C to 110 ° C.
[0008]
BEST MODE FOR CARRYING OUT THE INVENTION
The collagen used in the present invention is not particularly limited, but if the molecular size of the collagen is large, the strength of the complex does not appear due to steric hindrance. It is preferable to use collagen treated with pepsin. Pepsin-treated collagen also has the advantage of low antigenicity.
[0009]
As the aqueous phosphoric acid solution containing collagen used in the present invention, the weight of collagen relative to the weight of phosphoric acid is preferably in the range of 0.001 to 10,000, more preferably in the range of 0.1 to 5. . If the amount of phosphoric acid is too small, the Young's modulus of the obtained composite decreases and the strength decreases. On the other hand, when the amount of collagen is too small, the strength of the composite is reduced and the composite becomes brittle.
[0010]
Examples of the calcium salt used in the present invention include calcium hydroxide and calcium carbonate. The aqueous solution containing the calcium salt of the present invention may be a suspension. For example, after calcining calcium carbonate, it is ground in a mortar or the like to obtain calcium hydroxide, and water is added thereto to obtain a suspension of calcium hydroxide. The concentration of the calcium salt in the aqueous solution or suspension is preferably in the range of 1 to 20% by weight, more preferably in the range of 6 to 12% by weight. If the calcium salt concentration is too low, the Young's modulus will decrease. On the other hand, if the calcium salt concentration is too high, the strength will decrease.
[0011]
In the present invention, the ratio of the aqueous solution of phosphoric acid containing collagen to the aqueous solution containing calcium salt is preferably in the range of 3: 1 to 1: 3. When the amount of the aqueous phosphoric acid solution containing collagen is small, the composition becomes excessive in calcium and the strength decreases. When the amount of the aqueous solution containing the calcium salt is small, calcium deficiency occurs, the Young's modulus is reduced, and the strength is sometimes reduced.
[0012]
In the present invention, simultaneous dropping of an aqueous solution of phosphoric acid containing collagen and an aqueous solution containing calcium salt into a reaction vessel does not only mean a form of dropping exactly at the same time, but a small amount (0.01 to 5 ml). This also includes a form in which the solution is alternately dropped one by one. Both solutions may be dropped continuously or intermittently. At this time, it is desirable to drop the reaction solution so that the pH of the reaction solution is in the range of 7 to 11 and the change width is within 1 or less. More preferably, the pH is in the range of 7 to 9 and the range of change is in the range of 0.5 or less. Native collagen precipitates at the isoelectric point in the pH range of 7 to 11 and regenerates fibers.In addition, calcium phosphate easily precipitates in this pH range. The collagen orientation is excellent. If the pH exceeds 11, the collagen will be in a dissolved state and water molecules will be hydrated around the collagen molecules, and it will be difficult for the water molecules to separate even in the subsequent pressure molding step. There is a possibility that it will be hindered and the strength will decrease. On the other hand, when the pH is less than 7, both calcium phosphate and collagen are less likely to precipitate. On the other hand, if the width of the change exceeds 1, the nucleation of calcium phosphate on collagen will be disturbed, and the orientation will be poor. In order to perform such pH control, it is convenient to use a pH controller. The pH controller is provided with a means for measuring the pH of the reaction solution and a means for adjusting the amount of the solution to be dropped, and a certain range with respect to the pH (eg, 10) set as an expected value. (For example, ± 0.3), the dropping amounts of both solutions are adjusted based on the pH values of both solutions. In the case of the present invention, when the pH becomes lower than the expected value, the dropping of the aqueous solution of phosphoric acid containing collagen is temporarily stopped, and only the dropping of the aqueous solution containing calcium salt is performed. Conversely, when the pH becomes higher than the expected value, the dropping of the aqueous solution containing the calcium salt is temporarily stopped, and only the dropping of the phosphoric acid aqueous solution containing the collagen is performed. At this time, it is preferable to carry out the reaction while constantly stirring both the solution and the reaction solution so that the pH of the reaction solution is not biased.
[0013]
The precipitate generated from the reaction solution is filtered, dried, and then press-molded, whereby the organic-inorganic oriented composite material of the present invention, which is a complex in which calcium phosphate microcrystals and a collagen polymer are oriented and bonded in a self-assembled manner, obtain.
The pressure molding is preferably performed in a temperature range of 0 ° C. or more and 110 ° C. or less and a pressure range of 10 MPa to 5 GPa. This is because, when pressure molding is performed in this temperature range, most of the water contained in the precipitate is rapidly released. The temperature is preferably in the range of 25 ° C. or more and 60 ° C. or less where the amount of released water is large, and particularly preferably in the range of 35 ° C. or more and 45 ° C. or less. FIG. 2 shows the relationship between the pressure molding temperature and the amount of released water. In addition, by performing the treatment while applying ultrasonic waves, the orientation can be further improved. FIG. 1 shows an example of a pressure processing apparatus that can be used for pressure molding in the present invention. The apparatus includes a hydration water squeezing unit 2 for attaching a sample 1, a sample heating unit 3, and an ultrasonic generator 4 for applying ultrasonic waves to the sample 1.
[0014]
The organic-inorganic oriented composite material obtained according to the present invention has a strength and a composition close to that of a living bone, and since the constituents collagen and calcium phosphate are both biosoluble, a drug sustained release effect, or an osteoinductive or osteoconductive property. Has ability. When implanted in bone tissue, it quickly bonds to bone tissue, and after about 12 weeks, the interface between the donor-side hard tissue and the composite material obtained by the present invention can be completely integrated. Furthermore, for example, the effect of tissue reconstruction of bone marrow, liver, and the like is expected by culturing tissue in a living body-like environment or in a living body to which dynamics, electricity, etc. are added using a substrate containing a cytokine having high physiological activity. For the reconstruction of resected bone such as osteosarcoma, the use of a composite material obtained by the present invention impregnated with an anticancer agent can prevent cancer recurrence and induce living hard tissue. Therefore, the use of the complex obtained by the present invention includes the use as a living bone replacement type bone reconstruction material having osteoinductive and osteoconductive ability, bioactivity used in tissue engineering containing amino acids, carbohydrates, and cytokines. Substrates, and their use as biocompatible drug sustained-release substrates such as anticancer agents can be mentioned. Specifically, artificial bones, artificial joints, bonding materials between tendons and bones, dental implant materials, Percutaneous terminals for catheters, sustained drug release substrates, bone marrow induction chambers, tissue reconstruction chambers / substrates, and the like can be mentioned.
[0015]
【Example】
Hereinafter, the present invention will be described in more detail by way of examples, but the present invention is not limited thereto.
Example 1
1.5 L of pure water and 15 g of phosphoric acid were added to 1389 ml of pepsin-treated collagen (concentration 0.72%, 5 mM phosphoric acid aqueous solution) to form a mixed solution. Separately, 2 L of pure water was added to 48 g of calcium hydroxide finely ground in a mortar after calcining calcium carbonate at 900 ° C. for 10 hours to obtain a suspension.
[0016]
Both liquids were mixed with vigorous stirring while pumping both liquids so that the pH was maintained at 10 ± 0.3 with a pH controller. The resulting precipitate was filtered and dried. This was sealed in a capsule of a pressure device, and was held for 15 hours while being subjected to ultrasonic treatment at 30 ° C. and 300 MPa to perform pressure molding.
After the obtained composite was air-dried, the physical properties were measured, whereby the flexural strength was 90 MPa, the Young's modulus was 8 GPa, and the compressive strength was 150 MPa.
Example 2
1.5 L of pure water and 15 g of phosphoric acid were added to 1389 ml of collagen having a molecular weight of 300,000 (concentration 0.72%, 5 mM phosphoric acid aqueous solution) to prepare a mixed solution. Separately, 2 L of pure water was added to 48 g of calcium hydroxide finely ground in a mortar after calcining calcium carbonate at 900 ° C. for 10 hours to obtain a suspension.
[0017]
Both liquids were pumped and mixed with vigorous stirring so that the pH was maintained at 8.5 ± 0.3 with a pH controller. The resulting precipitate was filtered and dried. This was sealed in a capsule of a pressure device, and held at a temperature of 37 ° C. immediately below collagen gelatinization at a pressure of 500 MPa and ultrasonic waves for 15 hours to perform pressure molding.
[0018]
After the obtained composite was air-dried, the physical properties were measured, whereby the flexural strength was 120 MPa, the Young's modulus was 26 GPa, and the compressive strength was 180 MPa.
Comparative Example 1.5 L of pure water and 15 g of phosphoric acid were added to 1389 ml of pepsin-treated collagen (0.72% concentration, 5 mM aqueous phosphoric acid solution) to form a mixed solution. Separately, 2 L of pure water was added to 48 g of calcium hydroxide finely ground in a mortar after calcining calcium carbonate at 900 ° C. for 10 hours to obtain a suspension.
[0019]
While vigorously stirring the calcium hydroxide suspension, a phosphoric acid / collagen mixed solution was gradually dropped into the suspension to obtain a precipitate.
After the obtained composite was air-dried, the physical properties were measured, whereby the flexural strength was 50 MPa, the Young's modulus was 5.5 GPa, and the compressive strength was 75 MPa.
[0020]
【The invention's effect】
According to the present invention, since the pH can be controlled, an organic-inorganic oriented composite material having an excellent orientation between collagen and calcium phosphate can be obtained. Therefore, a composite having a Young's modulus comparable to that of hard living bone can be obtained.
[Brief description of the drawings]
FIG. 1 is a diagram showing an example of a pressure processing device that can be used for pressure molding in the present invention.
FIG. 2 is a graph showing the relationship between the pressure molding temperature and the amount of released water.

Claims (5)

A method for producing an organic-inorganic oriented composite material comprising collagen and calcium phosphate, wherein a phosphoric acid aqueous solution containing collagen and an aqueous solution containing calcium salt are simultaneously dropped into a reaction vessel to co-precipitate calcium phosphate and collagen. A method for producing an organic-inorganic oriented composite material, wherein the obtained precipitate is subjected to pressure molding after performing. The method for producing an organic-inorganic oriented composite material according to claim 1, wherein the pH of the reaction solution in the reaction vessel is within the range of 7 to 11, and the range of change is within one. 3. The method for producing an organic-inorganic oriented composite material according to claim 1, wherein pressure molding is performed while applying ultrasonic waves. The method for producing an organic-inorganic oriented composite material according to any one of claims 1 to 3, wherein pepsin-treated collagen is used as the collagen. The method for producing an organic-inorganic oriented composite material according to any one of claims 1 to 4, wherein the pressure molding is performed in a temperature range of 0C to 110C.

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