JPH04198007A - Hydroxyapatite and production thereof - Google Patents

Abstract

PURPOSE:To suppress elution of alkali component by treating purified fish bone with an enzyme to remove protein, treating the resulting substance with an alkali, primarily burning the prepared crude hydroxyapatite, cleaning the burnt hydroxyapatite with a solution of specific pH and further secondarily burning. CONSTITUTION:Purified fish bone is boiled in pure water and treated with 0.1-2wt.% based on protein in the fish bone, of protease at 50-70 deg.C into <=10wt.% content of residual organic substance. The resulting substance is treated with 1-4wt.% aqueous solution of NaOH at 90-98 deg.C while stirring to decompose the residual organic substance and to suppress formation of Ca3(PO4)2 during burning. After alkali treatment is over, the bone component is separated and washed with water to give purified hydroxyapatite. Then the hydroxyapatite is primarily burnt in an oxidizing atmosphere at 350-1,200 deg.C and cleaned with an aqueous cleaning solution having pH2-12 for a given time. Then, the hydroxyapatite is secondarily burn oxidizing atmosphere to give hydroxyapatite not eluting an alkali component.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Field of Application] The present invention relates to an alkali-insoluble hydroxyapatite suitable for biomaterials such as bone filling materials and a method for producing the same.

[Prior Art] Hydroxyapatite is a major component of biological hard tissue that constitutes the bones and teeth of moving animals. Therefore, it is attracting attention as a ceramic material with excellent biocompatibility, and it is used for artificial bones,
Applications to biomaterials such as artificial tooth roots, artificial teeth, and bone fillers are being actively pursued.

Normally, hydroxyapatite is produced using calcium salts and phosphates as raw materials, (1) reacting at a high temperature of about 1000°C in a steam atmosphere as necessary (dry method), (2) reacting in a solution with a specific pH about It can be synthesized by reacting at a temperature of 100°C (wet method), or (3) reacting in water vapor at a high temperature of approximately 400°C and under high pressure of several thousand atmospheres or more (hydrothermal synthesis method).

The hydroxyapatite synthesized in this way is extremely pure and does not contain trace metals other than calcium and phosphorus that are found in hard tissues such as natural bones and teeth, so it has better biocompatibility than natural bone. Inferior 6 On the other hand, the development of hydroxyapatite derived from natural bones is progressing, but the method of using livestock bones as a raw material does not necessarily have a clean environment in which livestock grow.
Livestock bones have a fundamental problem when applied to biomaterials: they contain harmful elements.

The present inventors have conducted extensive research in order to provide natural bone-derived hydroxyapatite using fish bones that grow in a clean environment, and have used purified fish bones as a raw material, enzyme-treated and alkali-treated to produce protein. proposed a method for producing hydroxyapatite by removing the components and firing at a temperature of 1200° C. or lower (Japanese Patent Application No. 306051/1999).

However, it has been found that when the hydroxyapatite powder or granules obtained by this method are dispersed in water, a phenomenon occurs in which alkaline components are eluted from the hydroxyapatite and the pH of the liquid increases. Such alkali elution phenomenon becomes an obstacle when used as a biomaterial.
There is a demand for the development of hydroxyapatite made from fish bones that does not cause this phenomenon.

[Problems to be Solved by the Invention] The present invention has been made in view of the above circumstances, and an object of the present invention is to provide an excellent biocompatible material that does not cause alkali elution using fish bones as a raw material. An object of the present invention is to provide hydroxyapatite and a method for producing the same.

[Means for Solving the Problems] The present invention provides alkali-insoluble hydroxyapatite made from 5R fish bones.

The hydroxyapatite of the present invention is powder or granule 1
The pH of a dispersion prepared by dispersing 1 part by weight in 10 parts by weight of water is 10.
less than

Such hydroxyapatite that does not elute alkaline components can be produced by the method of the present invention.

That is, in the method for producing hydroxyapatite of the present invention, purified fish bones are treated with enzymes to remove remaining proteins, and then treated with alkali and washed with water. After baking, cleaning with an aqueous cleaning solution with a pH of 2 or more and less than 10,
It is characterized by secondary firing at a temperature of 350°C to 600°C.

As the fish bones used in the present invention, bones of pollock, sardines, mackerel, saury, etc., which have a large and stable supply of raw materials, are suitable.In particular, bones of pollock, which have clean growing waters and contain almost no harmful components, are suitable. Bone is preferred.

In the present invention, purified fish bones are used as a raw material. Purified fish bones are obtained by enzymatically treating the fish bones with fish meat attached to remove as much of the fish meat and protein as possible, and then sterilizing them, for example by boiling them in a 0.5 to 3% hydrogen peroxide solution for 20 to 180 minutes. It is a purified fish bone product obtained by thorough washing with water and drying, which has an organic matter content of about 30% or less, has a low number of viable bacteria, and has a good shelf life.

The purified fish bone is further treated with a proteolytic enzyme to remove remaining proteins.

That is, after putting purified fish bones in pure water and boiling it,
Lower the temperature to 50-70°C and purify the proteolytic enzyme while stirring. 0.1% to 2% by weight of the protein in the fish bone.
Preferably, it is added in an amount of 0.4 to 1.0% by weight for reaction. As the peptide bonds in the protein are broken down by the action of the protease, the reaction solution becomes acidic and the pH decreases, so add an aqueous sodium hydroxide solution as appropriate to maintain the pH at 7 to 9 to maintain enzyme activity. .

As the proteolytic enzyme, those originating from animals, plants, and microorganisms can be used. Among these proteases, alkaline protease or neutral protease is preferred. Further, it is preferable that the optimum temperature is 35°C or higher.

By enzymatically treating purified fish bones again, the amount of residual organic matter is reduced to 10% or less. If the amount of residual organic matter is too large, it becomes impossible to properly control the temperature in the next firing step, which is undesirable because accidents of excessive temperature rise occur frequently.

After enzymatically treating purified fish bones, they are treated with alkali to obtain crude hydroxyapatite.

In the alkaline treatment, when the decomposition reaction by the proteolytic enzyme becomes slow, an aqueous sodium hydroxide solution is added to the reaction solution to make the sodium hydroxide concentration 1 to 4% by weight, and the temperature of the solution is adjusted to 90°C to 98°C. C. and stirring for about 30-60 minutes.

Alkaline treatment not only deactivates enzymes and decomposes residual organic matter, but also has the effect of suppressing the formation of tricalcium phosphate during the subsequent firing process. This alkali treatment can reduce the tricalcium phosphate content of hydroxyapatite after firing to 15% or less, preferably 10% or less, and more preferably 5% or less.

After the alkaline treatment is completed, the reaction solution is cooled, the bones are separated and thoroughly washed with pure water to obtain crude hydroxyapatite.

The crude hydroxyapatite obtained as described above is subjected to a primary firing treatment.

The primary firing treatment is carried out to completely incinerate and remove the small amount of organic matter remaining in the crude hydroxyapatite, and to adjust the physical properties of the final target hydroxyapatite, such as porosity, specific surface area, and crystallinity, to predetermined values. be done.

The primary firing temperature is appropriately selected within the temperature range of 350°C to 1200°C. If the calcination temperature is too low, the removal of organic matter by incineration will be incomplete and the final product will not be suitable as a biomaterial.
On the other hand, if the firing temperature is too high, hydroxyapatite will decompose and tricalcium phosphate will be produced, which is not preferable. Firing time is usually about 30 to 300 minutes.

The firing step is performed in an oxidizing atmosphere, that is, an atmosphere containing a large amount of oxygen gas, for example, in an air atmosphere. The oxygen concentration is 5% or more, preferably 1% at all stages of the firing process.
It is 5% or more. If the oxygen concentration is less than 5%, residual organic matter cannot be completely incinerated during firing, and unburned organic matter and carbon remain, which is not preferable.

The pH of the hydroxyapatite after primary firing is 2 or more and less than 10, preferably 3 to 8, and more preferably
3. Clean with aqueous cleaning solution from step 5 to step 5. This cleaning process has the surprising effect of preventing alkaline components from eluting from the hydroxyapatite that is finally obtained.6 If the pH of the cleaning solution is too low than 2, the hydroxyapatite will dissolve, which is undesirable; When it is 10 or more, the effect of cleaning treatment cannot be obtained.

The cleaning treatment is carried out by dispersing the hydroxyapatite in water after the secondary calcination treatment and leaving it standing or stirring, and then adding an inorganic acid, an organic acid, or a mixture thereof so that the pH of the liquid remains at a predetermined value. It is done as follows.

The washing treatment is preferably carried out under stirring, and it is effective to use a ball mill or the like to stir and simultaneously disperse and pulverize.

An inorganic acid, an organic acid, or a mixture thereof is added to keep the cleaning solution at a predetermined pH, but acetic acid, oxalic acid,
It is desirable to add only organic acids such as formic acid and citric acid.

The cleaning process is such that the pH of the cleaning solution changes even without adding acid.
It is necessary to perform the cleaning until the specified pH is maintained constant, and the cleaning time varies depending on the conditions, but it is approximately 10 to 100 minutes.
It is a minute.

After the cleaning treatment, the hydroxyapatite is subjected to secondary firing.

Secondary firing is carried out to completely remove organic acids, inorganic acids, etc. that inevitably adhere during the cleaning process by heating, and is usually at a temperature of 350 to 600°C, preferably 400 to 500°C, and usually about 30 to 30°C. It will be held for 300 minutes. If the secondary calcination temperature exceeds the primary calcination temperature, it will not only impose a heavy economic burden but also change the physical properties of the final product, so the secondary calcination temperature is preferably lower than the primary calcination temperature.

The secondary firing is also performed in an oxidizing atmosphere like the primary firing.

In the hydroxyapatite thus obtained, elution of alkaline components into water is suppressed. That is,
The pH of a dispersion prepared by dispersing 1 part by weight of the hydroxyapatite powder or granules in 10 parts by weight of water is less than 10.

The hydroxyapatite made from purified fish bones of the present invention can be used as it is as a powder or classified granules for bone filling materials, bone bulking materials, and the like. Furthermore, the usual ceramic forming method, either as it is or after finely pulverizing,
For example, it can be shaped by casting, press molding, extrusion, etc., then degreased and filled into a dense or porous body, which can be used for artificial bones, artificial teeth, artificial tooth roots, etc. can.

[Effects of the Invention] As described above, the hydroxyapatite made from fish bones of the present invention does not elute alkaline components, so it is suitable for use as a biological bone substitute material for treatment, and the method of the present invention - By washing with an aqueous cleaning solution with a pH of 2 or more and less than 10 after the secondary calcination treatment, and further performing the secondary calcination treatment, it is possible to produce hydroxyapatite without the elution of alkaline components using purified fish bones as a raw material. be.

[Example] Next, the present invention will be explained in more detail by reference examples and examples.

Reference Example Walleye pollock was cut into three pieces, and the obtained fish bones with the fish meat attached were added to a 0.3% aqueous solution of the natural enzyme Discrin-PT in a weight ratio of 1=3, and the temperature of the solution was lowered. 50℃
After stirring for 20 minutes and boiling for an additional 2 hours, the bones were taken out and washed with water. Next, this was immersed in a 1% aqueous hydrogen peroxide solution and boiled for 2 hours, and then the bones were taken out and washed with water.
Purified fish bones were prepared by drying at ℃ for 4 hours.

Example 1 The purified fish bones obtained in Reference Example were once boiled in pure water, and after 5 minutes, the temperature was lowered to 50°C, and 0.5% by weight of the fish bones was added with Disclin-NT. The mixture was stirred for 2 hours while maintaining the pH at 8 by appropriately adding -NaOH.

Next, sodium hydroxide was added to the reaction system in an amount of 3% by weight, and the mixture was maintained at 95° C. for 1 hour.

After cooling, the bones were taken out, washed with water, and dried at 105° C. for 4 hours to produce crude hydroxyapatite.

The crude hydroxyapatite thus produced was primarily fired at 900° C. for 2 hours using a gas furnace.

The hydroxyapatite obtained after the primary firing was washed with an aqueous washing solution as follows.

That is, hydroxyapatite is produced in a ball mill (T)
Mix H with an aqueous cleaning solution adjusted to the specified value shown in Table 1 with acetic acid or aqueous ammonia so that the weight ratio is 1=10, stir for 1 hour, separate the solid content, and wash with pure water. te1
It was dried at 05°C for 4 hours. In addition, when preparing the aqueous solution of pH 2 shown in Table 1, nitric acid was added together with acetic acid.

After the cleaning treatment, the hydroxyapatite was heat-treated at 400° C. for 2 hours using a gas furnace to perform secondary firing.

The obtained hydroxyapatite and the hydroxyapatite that was not subjected to the above washing treatment and secondary firing (No.
, 1), an alkali elution test was conducted as follows.

That is, 1 part by weight of hydroxyapatite was added to 10 parts by weight of pure water, and after stirring for 1 hour, the pH of the supernatant liquid was measured. p)] values of 8 or less were determined as (-), those with a value higher than 8 and lower than 10 were determined as (±), and those with a value of 10 or more were determined as (+). The results obtained are shown in Table 1.

As shown in Table 1, when hydroxyapatite was not subjected to cleaning treatment and the pH of the aqueous cleaning solution was 10, the elution test result was ten, and when the pH of the aqueous cleaning solution was less than 10, this was the limit for increasing the cleaning effect. There was found. Also,
When the pH of the aqueous cleaning solution was 2, some dissolution of hydroxyapatite was observed during the cleaning process. Therefore, the pH of the aqueous cleaning solution must be 2 or more and less than 10, preferably 3-8, more preferably 3.5-5.

Example 2 Hydroxyapatite was produced in the same manner as in Example 1, except that crude hydroxyapatite was primarily fired at a predetermined temperature shown in Table 2 and secondly fired at 450°C. In Experiments No. 009 and No. 11, no cleaning treatment was performed. The obtained hydroxyapatite was subjected to an alkali elution test in the same manner as in Example 1, and the physical properties were measured by the BET method for specific surface area and by the mercury porosimetry method, and the results are shown in Table 2.

As is clear from Table 2, the physical properties of the final hydroxyapatite hardly change even after the cleaning treatment after the second firing.

Claims (2)

[Claims] (1) Alkali-insoluble hydroxyapatite made from purified fish bones. (2) Purified fish bones are treated with enzymes to remove remaining proteins, then treated with alkali and washed with water. The crude hydroxyapatite obtained is first calcined at a temperature of 350°C to 1200°C, and then an aqueous solution with a pH of 2 or more and less than 10 A method for producing hydroxyapatite, which comprises washing with a washing liquid and performing secondary firing at a temperature of 350°C to 600°C.