CH667394A5 - ARTIFICIAL BONE-BUILDING BIOMATERIAL AND IMPLANTATION MATERIAL THEREOF. - Google Patents

Description

DESCRIPTION

The invention relates to an artificial bone-forming biomaterial which contains a bone-forming factor and to an implantation material which contains a shaped body serving as a carrier and loaded with the biomaterial. The implant material is suitable for use in surgery, such as orthopedic surgery and maxillofacial surgery, as well as methods for producing the biomaterial and the implant material.

Until now, it has been common practice when a missing part of a bone in a living body should be artificially replaced, to take a part from a certain area of the bone of the same living body and to transplant that part to where a part of the bone was missing. Such an autoplastic transplant represents the optimum due to the excellent biological compatibility with the bone for which replacement is to be created.

However, it is obvious that the amount of bone available for autoplastic transplantation is limited and the need to "collect" the bone increases the size of the surgery and causes severe pain to the patient. For this reason, in cases where large areas within a bone were missing, an artificial biomaterial with an affinity for the living body, such as metal or ceramic, was used to fill in the defect and to attach material to the defect in the bone.

However, such biomateial had the disadvantage that it was difficult to connect the biomaterial to the bone quickly and sufficiently firmly. This difficulty is believed to be caused mainly by the fact that insufficient bone is formed. Accordingly, it is difficult to quickly obtain a hard and hard tissue of the living body by surgery using conventional artificial biomaterial.

The object of the invention is therefore to eliminate the disadvantages inherent in the conventional artificial biomaterial described.

The object is achieved by means of the biomaterial according to claim 1. This consists of a mixture of a bone-forming factor and a carrier material for this factor. The carrier material is selected from the group consisting of collagens, their hydrolysis products and denaturation products, in particular gelatin. The bone-forming factor can be a bone-forming factor from the mouse, one from Dunn's osteosarcoma

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or a bone-forming factor separated and prepared from human osteosarcoma. Such bone-forming factors were previously known as bone-forming components in biomedical circles. The factor is firmly bound by means of the carrier material, so that it can cause the formation of bones in the living body and the carrier material itself is adsorbed by the living body.

Furthermore, the invention relates to an implantation material according to claim 8. The shaped body serves to ensure mechanical reinforcement within the living body. If the implantation material is used to replace and fix missing parts of a broken or otherwise injured bone, then thanks to the content of the biomaterial, it promotes rapid growth and rapid restoration of the bone by allowing new bone substance to be formed with sufficient strength.

An essential component of the artificial biomaterial according to the invention is a bone-forming factor. This factor is a substance that has long been thought to be present in a living body.

It is believed that the function of the bone-forming factor is to act extracellularly on undifferentiated mesenchymal cells and to induce the phenotype of the cells in chondrocytes and osteoblasts, so as to locally form bone tissue. After years of research, a method for separating a bone-forming factor (bone-forming factor from the mouse) from Dunn's osteosarcoma and subsequently cleaning the factor was developed. This method and the substance produced with it have been described in Biomedicai Research, 2 (1981) (5) 466/471. The substance is a basic and hydrophobic polypeptide with a molecular weight of approximately 20,000. Furthermore, it has recently been possible to separate and purify a similar bioactive bone-forming factor from humans from a human osteosarcoma, by means of transplantation on animals using a «genera- tion-to-generation »transplant.

The human bone-forming factor has essentially the same biochemical properties as the bone-forming factor obtainable from the osteosarcoma mentioned above. Accordingly, this human bone-forming factor is preferred for the inventions in terms of antigenicity.

In this way, the human bone-forming factor develops a bone-forming effectiveness in the living body. However, this requires a certain type of carrier material, which can form an embedding, in order to direct the factor into a specific region of the living body and to cause bone formation there. The extent of bone formation is regulated by the amount of the carrier material, which includes and transports the factor. This effect is achieved by the shaped body made of a ceramic material, e.g. ceramic hydroxyapatite, a metal or a synthetic resin. Accordingly, in order to ensure that the bone-forming factor is transported in the living body, the following carrier materials are provided.

The carrier material contains and transports the bone-forming factor and enables it to form a bone, while the carrier is a shaped body on or in which the carrier material is held and which has the shape required in individual cases in connection with the necessary strength.

It is necessary that the carrier material has the following properties:

1) it should not cause a foreign body reaction when embedded in a living body;

2) it should have an affinity for bone;

3) it should always be available on an industrial scale quickly and at a low price;

4) there should be a stable bond with the bone-forming factor without destroying its properties and be miscible with it in any ratio;

5) it should ultimately be able to be absorbed by the living body; and

6) it should be easy to bind to the shaped body serving as a carrier.

It is necessary that the carrier has the following properties:

1) it should have the properties of the carrier material mentioned under numbers 1 to 4;

2) the properties of the vehicle should remain unchanged for a long time;

3) it should easily form a physical bond with the substrate; and

4) it should have great mechanical strength. Various studies on materials for the

Carrier material led to the result that collagens, their hydrolysis products and denaturing products, in particular gelatin, can meet the requirements.

Incidentally, it is well known that collagen, including its hydrolysis and denaturation products, is a protein with generally low antigenicity; furthermore, it is known that the main cause of the antigenicity of collagen is in the terminal peptide portion, which forms a peripheral end portion of the molecule. Accordingly, solubilized collagen, which has essentially no telopeptide content and which is obtained by dissolving and processing cowhide by subjecting it to a known enzyme treatment and treatment with alkalis, is preferred as a carrier material for the biomaterial according to the invention. However, the carrier material is not limited to solubilized collagen. It is easy to understand that gelatin, which is a denaturing product of collagen, including its degradation products and derivatives, is also suitable for the practice of the invention.

Of the materials which can be used for the shaped body serving as the carrier and which meet the above-mentioned requirements, for example ceramic materials, special metals and synthetic resins come into consideration. These materials are known to be outstandingly suitable for this purpose, since they do not cause any foreign body reactions in the living body, have an affinity for the living body and have high mechanical strength. Of the materials mentioned above, the ceramic materials are distinguished by an extraordinarily good affinity for the living body; they are listed in Table I.

For the production of the biomaterial according to claim 1, as described below in Examples 1 and 3, the bone-forming factor is mixed with the carrier material, while for the production of the implant material, as described below in Examples 2 and 4, the shaped body with the mixture mentioned above is loaded. The mixture can either be adsorbed on the surface or preferably serve as an impregnation.

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Of the ceramic materials listed in Table I, the various types of aluminum oxide ceramics have the broadest application spectrum, do not exert any harmful influence on the living body and are distinguished by a high affinity for it. Materials with high affinity and high mechanical strength are sapphire (Al ^ Oj) and zirconium oxide ceramic (ZrCh). Other materials, such as calcium phosphate (Ca3 (P04) 2) and hydroxylapatite (Cai0 (PO4) 6 (OH)), which are closely related to the living body, have a somewhat lower mechanical strength, but are opposed by their excellent assimilability and their adherence Marked bones of the living body. Which of these ceramic materials are optimally suited depends on the location and the type of use. Depending on the intended use, ceramic materials of the dense type or of the porous type can be used. The minimum required proportion of the bone-forming factor in the biomaterial according to the invention differs depending on the degree of purity of the bone-forming factor. With the factors obtainable according to the method described in the literature, bone formation with a weight ratio of collagen: factor = 100: 0.5 is possible, OK. However, in order to increase and ensure the effectiveness in relation to bone formation, it is desirable to have a weight ratio of collagen : Set the bone-forming factor in the range from 100: 1 to 100: 10. However, the weight ratio should not be set in this range.

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Table I

Physical properties Flexural strength Hardness

(N. mm2)

Type of ceramic material

Density Resistance to (without water) chemical, 95% H2SO4, in boiling liquid (mg / cm2 / day)

Alumina ceramics

32,640

1000 to

3.6 to

0.1

(A1; 0.,)

2300

4.0

Sapphire (AI2O3)

71 400

2300 (H V) *

3.97

0.1

Zirconium oxide (ZrOi)

102,000

1250 (H V) *

5.9

0.8

Silicon carbide (SiC)

51000

94 (HRC) **

2.2 to 3.1

0.04

Silicon nitride (SÌ3N4)

51,000

87 to 91

2.9 to soluble in acid.

(HRC) **

3.3

0.42

Calcium phosphate

14 280

-

3.0 to soluble in acid,

CA, (P04):

3.05

poorly soluble in base

Hydroxyapatite

6 120 to

400 to 600

3.06 to as above

(Cai0 (PO4) 6 (OH2)

20 400

3.13

Glass ceramic

15 300 to

600 to 700

about like above

(Hydroxyapatite

17 340

3.5

containing)

* Vickers hardness

** Rockwell hardness (diamond cone)

40

The invention is explained below using exemplary embodiments.

example 1

The skin layer of the skin of a young cattle was cut into small pieces after cleaning and opening using a chopping machine. A hydrochloric acid solution was added to the skin layer so crushed and the pH was adjusted to 3. Thereafter, this solution was treated with pepsin in an amount of 2% by weight, based on the dry substance. added and the solution thus obtained digested at 20 C for 48 hours. The solution was filtered and sodium hydroxide was added to the filtrate to adjust the pH to 10 to deactivate the pepsin. The pH of the solution was then adjusted to 7. The precipitates formed were separated from the solution, collected, washed thoroughly with water and redissolved in a pH 3 hydrochloric acid solution. The solution was filtered and adjusted to pH 7 by adding sodium hydroxide again. The precipitates formed were separated from the solution, collected and washed with water. Thereafter, the precipitates were redissolved in a pH 3 hydrochloric acid solution to obtain a purified collagen at a concentration of 3.0 mg / ml.

Thereafter, a purified human bone-forming factor obtained by the method described in the above-mentioned literature was dissolved in 0.01N hydrochloric acid to obtain a solution having a concentration of 1.0 mg / ml. 0.2 ml of the solution obtained was placed in a test tube, 1.0 ml of the collagen solution was added and the mixture was thoroughly mixed. The mixture was freeze-dried and sterilized with ethylene oxide gas to obtain a biomaterial.

The biomaterial was implanted in the back muscle of a mouse. After 3 weeks, the implanted biomaterial was removed and it was found that the biomaterial had been replaced by 20 mg (wet weight) of bone.

Example 2

A square shaped body made of hydroxylapatite, but lacking four corners, with a side length of 5 mm, a thickness of 2 mm and a porosity of 40%, or a disk made of aluminum oxide ceramic was placed in 1.2 ml of the one in Example 1 described mixed solution of collagen and bone-forming factor immersed and subjected to a vacuum treatment in order to achieve a good penetration of the ceramic molded body with the mixed solution. Thereafter, the shaped body was freeze-dried and subjected to gas sterilization in order to obtain a biomaterial suitable for a transplant. The biomaterial obtained in this way was implanted in the back muscle of a mouse, whereupon

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the implanted material was removed after 3 weeks. Bone tissue growth was found to have occurred on the surface of the second support. In this case, the result obtained using hydroxyapatite was essentially the same as using aluminum oxide ceramic.

Example 3

Gelatin obtained from bovine bones using normal lime treatment (viscosity:

44 mPa x s; Gelatin resistance: 253 bloom; pH: 5.8; Moisture: 11%) was dissolved in treated water to obtain a gelatin solution with a concentration of 50 mg / ml.

0.2 ml of hydrochloric acid solution of the bone-forming factor described in Example 1 was thoroughly mixed with 1.0 ml of the gelatin solution and left overnight in a refrigerator to gel the mixed solution. The gelled material was immersed in 100 ml of a phosphoric acid buffer solution (pH 7.2) containing 0.1% glutaraldehyde, held there at 16 ° C. for 16 hours and then subjected to a crosslinking treatment. The gelled material was then removed from the buffer solution, washed with treated water and then subjected to freeze drying and gas sterilization in order to obtain a biomaterial suitable for transplantation.

The biomaterial was implanted in the back muscle of a mouse, with essentially the same result as in Example 1.

Example 4

The shaped body made of hydroxylapatite or aluminum oxide ceramic used in Example 2 was immersed in 1.2 ml of a mixed solution of bone-forming factor and gelatin produced in the manner described in Example 3 and subjected to a vacuum treatment in order to achieve a good impregnation of the shaped ceramic body with the mixed solution . Thereafter, the molded article impregnated with the solution was left to stand in a refrigerator overnight in order to convert the gelatin in the ceramic molded article into a gel. The gelled material containing the ceramic molded body was treated with a phosphoric acid buffer solution containing glutaraldehyde in the same manner as described in Example 3, washed with water, freeze-dried and subjected to gas sterilization to obtain a biomaterial suitable for transplantation. The biomaterial obtained in this way gave the same result as that from Example 2.

As can be seen from the exemplary embodiments described above, it was shown that in the case of the artificial bone-forming biomaterial and the implantation material containing it, the biological function of the bone-forming factor has only a low species-specificity. Based on these examples, it can be assumed that the invention will have a great impact in the clinical areas of orthopedic surgery and maxillofacial surgery.

Incidentally, in Examples 2 and 4, embodiments were described by way of example in which the shaped body serving as the carrier was impregnated and loaded with a mixed solution which contains the carrier material and the bone-forming factor; however, there is the possibility that instead of impregnation and loading of the shaped body with the mixed solution, the latter is only adsorbed on the shaped body. This adsorption corresponds to the state in which the mixed solution is only bound to the surface of the shaped body, while in the case of impregnation and loading, a state results in which the mixed solution not only on the surface of the shaped body but also in its interior, i.e. in bulk, is bound. The difference between the two states is only a difference in the extent of bone formation.

In addition to the embodiments described in the examples, numerous further configurations are possible within the scope of the invention.

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Claims (20)

667 394 1. As an artificial bone-forming biomaterial, a mixture of a bone-forming factor and a carrier material for this factor, this carrier material being selected from the group consisting of collagens, their hydrolysis products and their denaturing products. 2. Biomaterial according to claim 1, characterized in that the bone-forming factor is a bone-forming factor separated and prepared from Dunn's osteosarcoma or from human osteosarcoma. 2nd PATENT CLAIMS 3. Liquid solution of a biomaterial according to claim 1. 4. Liquid hydrochloric acid solution of a biomaterial according to claim 3, characterized in that the bone-forming factor is a bone-forming factor from humans. 5. Liquid hydrochloric acid solution of a biomaterial according to claim 3, characterized in that the carrier material is collagen or gelatin. 6. Biomaterial according to claim 3, characterized in that it is in the form of a lyophilisate. 7. Biomaterial according to claim 1, characterized in that it is in the form of a gelled liquid mixture. 8. Containing implant material for osteosynthesis - an artificial bone-forming biomaterial according to claim 1; and - A carrier for this biomaterial, which carrier is a shaped body made of a ceramic material, a metal or a synthetic resin and is loaded with the biomaterial. 9. Implantation material according to claim 8, characterized in that the carrier is a shaped body made of ceramic hydroxyapatite or made of aluminum oxide ceramic. 10. Implantation material according to claim 8, characterized in that the carrier is impregnated with the biomaterial. 11. Implantation material according to claim 8, characterized in that the carrier contains the biomaterial adsorbed on its surface. 12. A method for producing a biomaterial according to claim 1, characterized in that the carrier material in the form of a liquid is mixed with the bone-forming factor in the form of a liquid. 13. The method according to claim 12, characterized in that collagen in hydrochloric acid solution or gelatin in aqueous solution is used as the carrier material and a bone-forming factor obtained from human osteosarcoma by separation and preparation in dissolved form is used as the bone-forming factor. 14. The method according to claim 12 or 13, characterized in that one carries out a freeze-drying of the liquid mixture which contains the carrier material and the bone-forming factor. 15. The method according to claim 12 or 13, characterized in that the liquid mixture containing the carrier material and the bone-forming factor is converted into a gel. 16. A method for producing the implantation material according to claim 8, characterized in that the shaped body serving as a support made of ceramic, metal or synthetic resin with a bone-forming biomaterial according to claim 1, which is produced by the method according to claim 12 and in the form of the mixture of liquids mentioned in claim 12 is present, brings together such that the carrier is loaded with the biomaterial. 17. The method according to claim 16, characterized in that a shaped body made of ceramic hydroxylapatite or aluminum oxide ceramic is used as the carrier. 18. The method according to claim 16 or 17, characterized in that the carrier is impregnated by immersion in the liquid mixture containing the biomaterial and optionally vacuum treatment and then the mixture forming the impregnation is converted into a gel and freeze-dried. 19. The method according to any one of claims 16 to 18, characterized in that sterilization is carried out using ethylene oxide gas as the last process step. 20. Implantation material according to claim 8, produced by the method according to claim 18.