JP2006174985A - Calcium phosphate/polymer hybrid material - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a calcium phosphate/polymer hybrid material which is a biological material combining easiness in invasion into the cells, tissues and the like as a porous body while improving the brittleness or the strength of the calcium phosphate based porous body and is especially excellent in osteogenesis and osteoinduction. <P>SOLUTION: In the hybrid material comprising a calcium phosphate based ceramics porous body and a biodegradable polymer, the calcium phosphate based ceramics material comprises a porous structure with spherical pores communicating therethrough entirely. The porosity of the porous body is 60% or more to 80% or less, the average pore diameter is 100 μm or more to 300 μm or less, the diameter of the communication part between the pores is 20 μm or more to 100 μm or more. The porous body is filled with the biodegradable polymer at a rate of 85% or more to 95% or less of the pores to hybridize. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a calcium phosphate / polymer hybrid material suitable for a biomaterial in which a calcium phosphate ceramic having excellent biocompatibility and a biodegradable polymer are combined.

Since calcium phosphate ceramics such as hydroxyapatite (HAp) and tricalcium phosphate (β-TCP) are close to the original bone composition, artificial bones are currently used in surgical and dental treatments. It is clinically applied as a material suitable for artificial joints, artificial tooth roots and the like.
This calcium phosphate ceramic is not harmful to the living body and is excellent in biocompatibility, and when it is embedded in the living body, rapid bone repair is performed using the ceramic as a scaffold, and directly bonded to the new bone, Alternatively, it has been recognized that it has the property of being degraded in vivo and gradually replacing new bone. That is, it has an excellent feature that it is possible to replace it with autologous bone only after it is once buried in the bone defect part in the operation.
In particular, by adopting a porous structure, cells and the like can easily enter into the calcium phosphate ceramics, and more excellent substituteability for autologous bone is exhibited.

  However, although the calcium phosphate ceramic porous body has an elastic modulus close to that of living bone due to its high porosity, it is brittle and inferior in strength compared to a dense body. In a portion where a load is applied, such as around a hole through which it passes, there is a drawback that it is likely to be lost or damaged.

  Therefore, an artificial bone made of a calcium phosphate-based ceramic porous body needs to have a structure that allows easy entry of cells, tissues, etc. into the inside, but also requires a certain degree of strength. It was done.

Therefore, in order to make the calcium phosphate porous body suitable for the artificial bone as described above, for example, the surface of the calcium phosphate porous body or the porous granule as disclosed in Patent Documents 1 and 2 and the like is placed on the living body. A method of coating with an absorbent organic material or a highly biocompatible material or applying a concentrated body fluid has been proposed.
JP 2003-10310 A JP 2004-159971 A

However, the calcium phosphate based porous material described in Patent Document 1 is a granular filler having a particle size of about several millimeters used for filling the bone defect portion of the skull, and the bone defect portion is used as one member. It was not intended to be embedded in the material, and strength was not considered.
Moreover, the ceramic porous body described in Patent Document 2 has not been sufficiently improved in strength around the pores.

  The present invention has been made to solve the above technical problem, and is intended to improve the brittleness and strength of the calcium phosphate porous body, and to facilitate the entry of cells, tissues, etc. into the porous body. In particular, an object of the present invention is to provide a calcium phosphate / polymer hybrid material excellent in bone formation and osteoinduction promoting action.

The calcium phosphate / polymer hybrid material according to the present invention comprises a calcium phosphate ceramic porous body and a biodegradable polymer, and the calcium phosphate ceramic porous body has a porous structure in which spherical pores are communicated with each other, and has a porosity of 60. % To 80%, the average pore diameter is 100 μm to 300 μm, the diameter of the communication part between each pore is 20 μm to 100 μm, and 85% to 95% of the pores are filled with the biodegradable polymer. It is characterized by that.
Thus, by combining the calcium phosphate ceramic porous body and the biodegradable polymer, the brittleness and strength of the porous body at the time of implantation are improved, and bone formation and bone induction at the initial stage of the implant are promoted.

The calcium phosphate ceramic is preferably HAp or β-tricalcium phosphate β-TCP.
Both HAp and β-TCP are excellent in biocompatibility and biocompatibility, are also suitable as cell scaffolds, and are suitable materials as bone prosthetic materials.

The porosity of the calcium phosphate / polymer hybrid material as a whole is preferably 5% or more and 10% or less.
The overall porosity is related to the filling rate of the biodegradable polymer, and it is preferable that the porosity is small. However, it is difficult to completely fill the biodegradable polymer in the micropores. If the porosity is within the above range, sufficient strength can be obtained.

Furthermore, it is preferable that the biodegradable polymer is collagen, and at least one of an extracellular matrix component, a bone morphogenetic factor, and a bone growth factor is introduced into the collagen.
By introducing an extracellular matrix component or the like into the collagen, effects such as cell migration and connective tissue formation promotion in the hybrid material can be further enhanced.

The biodegradable polymer preferably has a molecular weight of 10,000 to 50,000.
As the molecular weight of the biodegradable polymer to be filled increases, the strength of the ceramic porous body improves, but the degradation rate in vivo becomes slow, and it becomes difficult to fully utilize the characteristics of the porous body. It is preferable to be within the range.

As described above, the calcium phosphate / polymer hybrid material according to the present invention improves the brittleness and strength of the calcium phosphate based porous body, and also has the ease of entry of cells, tissues, etc. into the porous body. In particular, it has excellent bone formation and bone induction promoting action.
Therefore, the calcium phosphate / polymer hybrid material can be suitably used for biomedical members including bone prosthetic materials.

Hereinafter, the present invention will be described in more detail.
The calcium phosphate / polymer hybrid material according to the present invention is such that a biodegradable polymer is filled in the pores of a calcium phosphate ceramic porous body.
Both the calcium phosphate ceramic porous body and the biodegradable polymer are materials that are not harmful to living organisms, and the hybrid material can be suitably used as a living body member.
In addition, since the biodegradable polymer is decomposed and absorbed at the initial stage of implant, new bone, living tissue and the like can enter the porous ceramic body, and maintain the characteristics as a porous body. Is.

The inside of the calcium phosphate ceramic porous body has a structure in which a large number of spherical pores are distributed three-dimensionally and pores in which adjacent pores communicate with each other.
Since the pores communicate with each other, the invasion of cells and the like into the porous body is promoted, so that the formation of bone can be promoted.
The spherical pores are not limited to strictly spherical shapes, but also include pores having a shape such as a shape in which the true sphere is slightly flattened or distorted.

The calcium phosphate ceramic porous body has a porosity of 60% or more and 80% or less in terms of surface area in the porous body, permeability of blood and body fluids, invasion and adhesion of cells, etc. A thing with a hole diameter of 100 micrometers or more and 300 micrometers or less is used.
When the average pore diameter is less than 100 μm, it becomes difficult for cells, tissues and the like to enter the inside of the porous body, and it is not possible to sufficiently promote the formation of bone inside the pores.
On the other hand, when the average pore diameter exceeds 300 μm, since the space is too large, the cells that have entered the pores are difficult to be anchored, and it is difficult to sufficiently settle. In this case, too, bone formation inside the pores The promotion effect is insufficient.

Moreover, it is preferable that the diameter of the communication part between the adjacent pores of the porous body is 20 μm or more and 100 μm or less.
If it is a communication part which has the magnitude | size within the said range, a cell and a biological tissue can penetrate | invade and it can aim at formation promotion of the bone inside a porous body.
In addition, the diameter of the communicating part between the pores can be obtained from pore diameter distribution measurement using a mercury porosimeter.

The calcium phosphate ceramic is preferably HAp or β-TCP.
HAp is a main component of bone, and application to the human body has already been recognized, and is preferable from the viewpoints of assimilation with bone, adhesion, early recovery, and relatively high strength. It is also suitable as a cell scaffold.
Similarly, β-TCP is also a suitable material excellent in biocompatibility and biocompatibility.

The calcium phosphate ceramic porous body having the porous structure as described above can be easily produced by a method of stirring and foaming a slurry containing a calcium phosphate ceramic material.
In addition, the porous body which consists of a HAp sintered compact manufactured in this way is marketed by the product name of NEOBONE (trademark).
The porous body in which pores are formed by stirring and foaming has a dense skeleton that defines the pores, the pores are almost spherical, and high strength can be obtained, and cells, blood, etc. penetrate through capillarity. Easy to handle. Furthermore, it has excellent characteristics such as a large surface area per unit volume and a suitable property as a scaffold for invading cells.

The pores of the ceramic porous body are filled with a biodegradable polymer at a filling rate of 85% to 95%.
Thus, by combining the calcium phosphate ceramic porous body and the biodegradable polymer, the brittleness and strength of the porous body at the time of implantation are improved, and bone formation and bone induction at the initial stage of the implant are promoted.

When the filling rate of the biodegradable polymer is less than 85%, for example, the three-point bending strength is less than 30 MPa, and sufficient strength required at the time of implantation cannot be obtained.
For this reason, it is preferable that the filling rate is high, but it is difficult to fill 100% of the biodegradable polymer into the micropores, and about 95% is the limit.

As described above, the calcium phosphate / polymer hybrid material obtained by filling the biodegradable polymer preferably has a total porosity of 5% to 10%.
The overall porosity is related to the filling rate of the biodegradable polymer. For the same reason, if the overall porosity is within the above range, sufficient strength can be obtained.

Examples of the biodegradable polymer filled in the pores include collagen, polylactic acid, caprolactone, and polyvinyl alcohol. Among these, collagen is preferably used because of its high safety against living bodies.
Collagen is a structural protein and is also a typical extracellular matrix fiber component.

  Extracellular matrices include cell adhesion glycoproteins such as fibronectin, bidronectin, and laminin, and complex carbohydrates such as proteoglycan and glycosaminoglycan, which are used to promote cell migration and connective tissue formation. It may be introduced into the collagen.

In addition to the extracellular matrix, the collagen may carry bone forming factors, growth factors, and the like.
Here, the bone morphogenetic factor and the growth factor are cells and activated substances for promoting bone formation and growth. For example, chondrocytes, osteoblasts, fibroblasts, endothelial cells, epithelial cells, myoblasts, adipocytes, hepatocytes, nerve cells, or precursors thereof, mesenchymal stem cells or embryonic stem cells (ES cells) ) And the like.
These may be one type or a plurality of types.
In addition, the collagen may be loaded with a drug such as an antibiotic for infectious disease countermeasures.

The biodegradable polymer preferably has a molecular weight of 10,000 to 50,000.
When the molecular weight of the biodegradable polymer is less than 10,000, the strength of the ceramic porous body cannot be sufficiently improved.
The molecular weight is preferably larger in order to improve the strength of the ceramic porous body. However, when the molecular weight exceeds 50000, the degradation rate in vivo becomes slow, and the characteristics of the porous body are sufficiently obtained. It becomes difficult to make use of it.

The filling method of the biodegradable polymer into the pores of the calcium phosphate ceramic porous body is not particularly limited as long as it can satisfy the filling rate within the above range and the porosity of the entire hybrid material.
For example, when collagen is used as the biodegradable polymer, a collagen gel into which the extracellular matrix component described above is introduced is prepared, and this is repeatedly vacuum-frozen and spontaneously thawed together with the ceramic porous body, It can be filled by introducing a collagen gel into a hybrid material.
In the above method, it is preferable that after the filling, a cross-linking treatment or the like is performed to prevent the collagen gel from flowing out and to obtain a stable hybrid material.

EXAMPLES Hereinafter, although this invention is demonstrated more concretely based on an Example, this invention is not restrict | limited by the following Example.
[Example 1]
A slurry was prepared by adding 327.27 g of a 15 wt% polyethyleneimine aqueous solution as a dispersion medium to 400.00 g of HAp raw material powder having an average particle diameter of 1 μm and mixing for 48 hours by a ball mill.
As a foaming agent, 0.24 g of polyoxyethylene lauryl ether was added to 100.00 g of the obtained slurry, and a foamy slurry was obtained by mechanical stirring.
To this foamy slurry, 1.96 g of sorbitol polyglycidyl ether as a crosslinking agent was added and mixed, then cast into a mold and demolded to obtain a porous gelled body.
The demolded porous gelled body was dried overnight in a humidified dryer at 30 ° C. and 90% humidity to obtain a molded body (dried body).
This molded body was fired at 1200 ° C. for 1 hour to obtain a ceramic porous body.

  On the other hand, collagen is dissolved in 0.5 M acetic acid to prepare a 0.5 wt% acidic collagen solution, and sodium chloride is added to this to gel, laminin and BMP-2 which is an osteogenic factor are introduced. A collagen gel was obtained.

The collagen gel and the ceramic porous body were placed in a flask, depressurized to 10 ⁻² Torr in a vacuum line, and frozen using liquid nitrogen. After natural thawing in a reduced pressure state, the pressure was returned to normal pressure. This operation was repeated three times to deaerate the pores of the ceramic porous body and introduce a collagen gel.
Thereafter, a crosslinking treatment with glutaraldehyde was performed to prepare a calcium phosphate / polymer hybrid material.

A test piece having a square pyramid shape having an upper base of 10 mm, a lower base of 15 mm, and a height of 5 mm, and a through-hole having a diameter of 1 mm formed at a half height, is prepared from the hybrid material. A tensile strength test was conducted.
In the test, a surgical thread was tied through the through hole of the hybrid material specimen, the specimen was fixed, the thread was pulled in an oblique direction, and the breaking strength of the specimen was measured.
In addition, three-point bending strength was also measured.

[Comparative Example 1]
As a blank, the same strength test as in Example 1 was performed on a test piece having the same shape made only of the ceramic porous body in Example 1.

As a result of the strength test, the average tensile strength of the porous specimen alone (blank) was 3 kg, while the hybrid specimen was an average of 8 kg.
The three-point bending strength was 10 MPa for the blank, whereas it was 50 MPa for the hybrid material specimen.

From the above test results, the tensile strength is improved by introducing collagen, which is a biodegradable polymer, into the hydroxyapatite ceramic porous body, the surgical thread bites into the porous body, the corners of the hybrid material are missing, It was recognized that damage or the like can be prevented.
Further, it was confirmed that the hybrid material exhibits high mechanical strength that can be applied also as a bone filling material in a portion where a large load is applied such as a vertebral body.

[Example 2]
A calcium phosphate / polymer hybrid material produced in the same manner as in Example 1 was processed into a columnar shape having a diameter of 6 mm and a height of 10 mm to obtain a bone grafting material, which was embedded in the femur of a Japanese white mature rabbit weighing approximately 3 kg.
After 1, 3 and 6 weeks after the operation, the incision was made again to remove the femur, and a non-decalcified polished specimen was prepared from the tissue around the bone prosthesis, and histological evaluation was performed by HE staining. .

In the first week after the operation, collagen was eluted from the surface layer of the bone grafting material, and formation of new bone around it was partially observed.
At 3 weeks, collagen was eluted inside the porous material of the bone grafting material, and active formation of new bone was observed around it, but formation of new bone marrow was not observed.
At 6 weeks, collagen elution was observed in the deep part of the porous material of the bone grafting material, and active formation of new bone and new bone marrow was confirmed even in the deep part of the porous material.

[Reference example]
The porous ceramic body in Example 1 was used as a bone prosthetic material in the same manner as in Example 2, embedded in the femur of a rabbit, and after 1, 3, and 6 weeks after the operation, the tissue around the bone prosthetic material was evaluated. went.
In the first week after the operation, new bone entered into the pores of the porous material of the bone filling material, and more new bone was invaded than in Example 2.
In the third week, bone formation was observed in the deep part of the porous material of the bone filling material, and formation of new bone marrow could be confirmed in part.
In the sixth week, formation of new bone with new bone marrow was confirmed in the deep part of the porous material of the bone grafting material, and it was observed that the amount of new bone increased over time.

From the above results, the hybrid material in which collagen was introduced and composited (Example 2) was slightly delayed in bone formation at the initial stage of the implant compared to the case of the ceramic porous body alone (Reference Example). The body can be prevented from being damaged, and the collagen part, which is a biodegradable polymer, is decomposed and absorbed at an early stage, so that new bone and living tissue can enter the porous body. It was recognized that
In addition, it was confirmed that the bone forming ability equivalent to that in the case of the porous body alone (reference example) was shown in the sixth week after the operation by loading the bone forming factor and the growth factor on the collagen.

Claims (5)

It consists of a calcium phosphate ceramic porous body and a biodegradable polymer,
The calcium phosphate-based ceramic porous body has a porous structure in which spherical pores communicate with each other, and has a porosity of 60% or more and 80% or less, an average pore size of 100 µm or more and 300 µm or less, and a diameter of a communication portion between the pores. A calcium phosphate / polymer hybrid material, which is 20 μm or more and 100 μm, and 85% or more and 95% or less of the pores are filled with the biodegradable polymer.   2. The calcium phosphate / polymer hybrid material according to claim 1, wherein the calcium phosphate ceramic is hydroxyapatite or β-tricalcium phosphate.   A calcium phosphate / polymer hybrid material having a total porosity of 5% to 10%.   The biodegradable polymer is collagen, and at least one of an extracellular matrix component, an osteogenic factor, and a bone growth factor is introduced into the collagen. The calcium phosphate / polymer hybrid material according to claim 3.   The calcium phosphate / polymer hybrid material according to any one of claims 1 to 4, wherein the biodegradable polymer has a molecular weight of 10,000 to 50,000.