INJECTABLE CALCIUM PHOSPHATE-BASED BONE GRAFT COMPOSITION HAVING HIGH ELASTICITY AND PREPARATION METHOD THEREOF

Abstract

Provided are a bone graft composition and a preparation method thereof, and more particularly, a bone graft composition provided in the form of a putty formulation by mixing calcium phosphate compound particles with hydrogel, having excellent physical properties, which is easy to inject, and which maintains its structure even in an in vivo environment after implantation, thereby enabling sustained release of a drug loaded therein.

Claims

1. An injectable bone graft composition comprising: more than 55 wt % (% by weight) and 80 wt % or less of calcium phosphate compound particles; and 20 wt % or more and less than 45 wt % of biodegradable hydrogel.

2. The injectable bone graft composition of claim 1, wherein the calcium phosphate compound is any one or a combination of two or more selected from the group consisting of hydroxyapatite, tricalcium phosphate (TCP, Ca.sub.3(PO.sub.4).sub.2), tetracalcium phosphate (Ca.sub.4(PO.sub.4).sub.2O), brushite (CaHPO.sub.4.2H.sub.2O), dicalcium diphosphate (Ca.sub.2P.sub.2O.sub.7), calcium tripolyphosphate (Ca.sub.5(P.sub.3O.sub.10).sub.2), Mg-containing apatite, Mg-containing TCP, Sr-containing apatite, and fluorapatite.

3. The injectable bone graft composition of claim 1, wherein the calcium phosphate compound particles are porous particles having a size of 45 μm to 100 μm and 200 μm to 6,000 μm in mean diameter.

4. The injectable bone graft composition of claim 3, wherein the porous particles have porosity of 60 vol % (% by volume) or more.

5. The injectable bone graft composition of claim 1, wherein the hydrogel includes one or more selected from the group consisting of a poloxamer, collagen, hyaluronic acid, gelatin, a PEG/PPG/PEG block copolymer, and cellulose.

6. The injectable bone graft composition of claim 5, wherein the hydrogel is a material having a non-crosslinked structure without a swelling property.

7. The injectable bone graft composition of claim 1, further comprising a physiologically active substance.

8. The injectable bone graft composition of claim 7, wherein the physiologically active substance is one or more selected from the group consisting of bone morphogenetic proteins, bone morphogenetic peptides, extracellular matrix proteins, and tissue growth factors.

9. The injectable bone graft composition of claim 1, wherein the injectable bone graft composition is used in bone grafting, maxillary sinus lifting, lumbar interbody fusion, cervical interbody fusion, or upper & lower extremity fracture fusion.

10. The injectable bone graft composition of claim 1, wherein the injectable bone graft composition is a putty formulation.

11. A kit for bone implantation, the kit comprising the bone graft composition of claim 1 and an injection tool.

12. The kit of claim 11, wherein the injection tool includes a mixing syringe or a vial transport device.

13. The kit of claim 11, wherein the bone graft composition further comprises a physiologically active substance.

14. The kit of claim 13, wherein the physiologically active substance is one or more selected from the group consisting of bone morphogenetic proteins, bone morphogenetic peptides, extracellular matrix proteins, and tissue growth factors.

15. The kit of claim 11, wherein the bone graft composition is used in bone grafting, maxillary sinus lifting, lumbar interbody fusion, cervical interbody fusion, or upper & lower extremity fracture fusion.

Description

DESCRIPTION OF DRAWINGS

[0054] FIG. 1 shows actual appearances of various sizes (r) of calcium phosphate-based compound particles;

[0055] FIG. 2 shows appearances of compositions prepared by mixing various sizes of calcium phosphate-based compound particles with hydrogel at predetermined ratios;

[0056] FIG. 3 shows an exemplary formulation of a composition according to one exemplary embodiment of the present invention, wherein the left shows the use of the composition filled in a putty-type syringe which is used in dentistry, and the right shows the use of the composition filled in a case which is used in spine fusion surgery;

[0057] FIG. 4 shows elasticity and/or texture of the composition according to one exemplary embodiment of the present invention;

[0058] FIG. 5 shows shape retention ability of bone graft materials under in vivo mimetic conditions, the bone graft materials composed of the compositions which were prepared by mixing various sizes of calcium phosphate-based compounds with hydrogel at predetermined ratios;

[0059] FIG. 6 shows sustained drug release of bone graft materials under in vivo mimetic conditions, the bone graft materials composed of the compositions which were prepared by mixing various sizes of calcium phosphate-based compounds with hydrogel at predetermined ratios;

[0060] FIG. 7 shows shear strain vs. shear stress of the bone graft material prepared according to one exemplary embodiment of the present invention in a fluid environment (black solid line), wherein as a control (blue solid line), a bone graft composition of Comparative Example 6 was used; and

[0061] FIG. 8 shows changes in compressive strength according to the sizes of the calcium phosphate compound particles of the bone graft materials prepared according to one exemplary embodiment of the present invention.

MODE FOR INVENTION

[0062] Hereinafter, the configuration and effects of the present invention will be described in more detail with reference to exemplary embodiments. However, these exemplary embodiments are for illustrative purposes only, and the scope of the present invention is not intended to be limited by these exemplary embodiments.

PREPARATION EXAMPLE 1: Preparation of calcium phosphate Compound Particle Powder 1

[0063] Pure β-TCP powder (Cerectron Co., Korea) was spray-dried to prepare a spherical shape. Then, the spherical β-TCP powder was sintered at 1050° C., and the sintered particles were classified in the range of 45 μm to 75 μm.

PREPARATION EXAMPLE 2: Preparation of calcium phosphate Compound Particle Powder 2

[0064] Calcium phosphate compound particles having a distribution in the range of 200 μm to 6,000 μm were prepared with reference to the method disclosed in Korean Patent No. 10-0401941.

EXAMPLE 1: Preparation of High-Elasticity calcium phosphate-Based Bone Graft Material

[0065] First, HPMC and poloxamer 407 were mixed using a high-speed vacuum mixer to produce hydrogel, and then the β-TCP powder prepared according to Preparation Example 1 was uniformly mixed therewith to obtain a hydrogel complex.

[0066] Subsequently, the prepared hydrogel complex was mixed with the hydroxyapatite ceramic granules having a size of 0.6 mm to 6 mm prepared according to Preparation Example 2 to prepare a bone graft material of a putty formulation. The mixing was performed using a specialized mixing syringe so that the hydroxyapatite granules were pulverized.

COMPARATIVE EXAMPLES 1 to 4: Various Sizes of Calcium Phosphate-Based Compound Particles

[0067] Particle-type calcium phosphate-based compounds having a size in the range of less than 100 μm, 600 μm to less than 1,000 μm, 1,000 μm to less than 3,000 μm, and 3,000 μm to 6,000 μm were prepared using the samples of Comparative Examples 1 to 4, respectively.

COMPARATIVE EXAMPLES 5 to 7: Bone Graft Composition Including Controlled Contents of calcium phosphate-based Compound Microparticles and Hydrogel

[0068] Calcium phosphate-based compound particles having a size of less than 100 μm and hydrogel were mixed at a weight ratio of 30:70, 50:50, and 70:30 to prepare bone graft compositions of Comparative Examples 5 to 7, respectively.

COMPARATIVE EXAMPLE 8: Bone Graft Composition Including Controlled Contents of Calcium Phosphate-Based Compound Macroparticles and Hydrogel

[0069] Calcium phosphate-based compound particles having a size of 1,000 μm to less than 3,000 μm and hydrogel were mixed at a weight ratio of 50:50 to prepare a bone graft composition of Comparative Example 8.

EXPERIMENTAL EXAMPLE 1: Appearance and Physical Properties of Bone Graft Composition

[0070] The shapes of the calcium phosphate-based compound particles of Comparative Examples 1 to 4 were observed with the unaided eye and photographed, and are shown in FIG. 1. As shown in FIG. 1, when the calcium phosphate-based compounds were used alone, it was difficult to process the compounds into a desired shape because they were composed of particles, and thus their use as a bone graft material was very limited.

[0071] Further, appearance and features of the bone graft compositions of Comparative Examples 5 to 8 and Example 1 are shown in FIG. 2. As shown in FIG. 2, the bone graft compositions composed of calcium phosphate-based compound particles having a size of less than 100 μm and hydrogel showed the difference in appearance according to the composition ratio of these components, which was visible to the unaided eye. When the content of the calcium phosphate-based compound was as low as 30% (Comparative Example 5), the particle loading amount was insufficient, and thus the physical properties closer to the hydrogel were maintained. However, when the content of the calcium phosphate-based compound was 50% (Comparative Example 6, Excelos Inject), particles agglomerated well with the hydrogel to form and maintain a clay-like shape, similar to Example 1, when examined with the unaided eye. Meanwhile, in the composition (Comparative Example 8), which was prepared by mixing calcium phosphate-based compound particles having a size of 1,000 μm to less than 3,000 μm and hydrogel at a weight ratio of 50:50, although the particles agglomerated into a single mass, a structure with a rough surface was formed due to individual particles. Furthermore, as in the composition of Example 1, when the content of the calcium phosphate-based compound was increased by 70% (Comparative Example 7), only microparticles with a size of less than 100 μm could not agglomerate into a single mass and crumbled due to the excessive loading amount of particles. Meanwhile, as in Comparative Example 7, even though the content of the calcium phosphate-based compound was as high as 70%, when macroparticles having a size of 200 μm or more were further included in addition to calcium phosphate-based compound microparticles having a size of less than 100 μm, they were found to aggregate with the hydrogel to form a single mass, as in Comparative Example 6. This suggests that a bone graft composition having a higher content of calcium phosphate compound may be provided by using a mixture of microparticles and macroparticles.

[0072] As described, the bone graft composition of Example 1, which was prepared by including the high 70% content of the calcium phosphate-based compound, was formulated into various preparations, and the clinical applicability thereof was tested. The test results are shown in FIGS. 3 and 4. As shown in FIG. 3, the bone graft composition of Example 1 could be injected using a dental putty-type syringe, and it was easily filled in a cage used for spinal fusion. Further, as shown in FIG. 4, when the shape was deformed by pressing it even with fingers, the composition could be easily deformed into a desired shape and did not stick to the fingers, and it was advantageous in controlling, with no concern about loss. As described above, since the bone graft composition of the present invention has enough fluidity to be injected using a syringe, it may be directly injected into a defect where it is difficult to accomplish a desired shape. It is also easy to obtain a desired shape by hand or using a predetermined cast, and the corresponding shape may be maintained. Thus, it may be used for bone regeneration.

EXPERIMENTAL EXAMPLE 2: Shape Retention Ability and Sustained Drug Release Under In Vivo Mimetic Conditions

[0073] To examine properties of the bone graft materials under in vivo mimetic conditions, each of the compositions of Comparative Examples 4 to 8 and Example 1 was put in a cage and immersed in physiological saline at 37° C. After 5 minutes and 24 hours of immersion, their shape retention was examined. The results are shown in FIG. 5. Furthermore, in order to examine the release patterns of the bone graft materials when a drug was loaded therein, a red dye was loaded instead of the drug so that each sample was visually identified and then treated as described above. The color of the solution was examined before immersing in physiological saline and after 5 minutes of immersion, and the results are shown in FIG. 6.

[0074] As shown in FIG. 5, when the macroparticle-type calcium phosphate-based compound was used alone (Comparative Example 4), even at 24 hours after being immersed in physiological saline similar to the body temperature, no change in the shape was visually observed. When the content of the calcium phosphate-based compound was as low as 30% (Comparative Example 5), the shape was actually maintained until 5 minutes after being immersed in physiological saline, but after 24 hours, it was completely decomposed, and the shape could not be identified. This indicates that no strong physical bond was formed between the calcium phosphate-based compound particles and the hydrogel. When the content of the calcium phosphate-based compound was 50% (Comparative Example 6, Excelos Inject), an almost intact shape was maintained until 5 minutes after being immersed in physiological saline. However, after 24 hours, most of the particles were decomposed and only partly remained. This indicates that the particles still failed to form a bond strong enough to withstand the in vivo mimetic conditions. Meanwhile, when the content of the calcium phosphate-based compound was as high as 70% (Comparative Example 7), the desired shape could not be obtained because the particles were not sufficiently combined as they are, and thus additional experiments were not possible, as confirmed in Experimental Example 1. Furthermore, the composition including 50% of the calcium phosphate-based compound macroparticles (Comparative Example 8) exhibited excellent shape retention ability, as compared with the composition of Comparative Example 6 including the same amount of the microparticles, but a significant portion thereof was decomposed. In contrast, the composition of Example 1, which was prepared by including 70% of both the microparticles and the macroparticles, maintained the existing shape without structural decomposition even after 24 hours. This suggests that the graft material composed of the composition of Example 1 is a material suitable for use as a bone graft material, which is able to maintain its structure even in a practical surgical environment such as bone implantation and/or spinal fusion.

[0075] As shown in FIG. 6, the graft materials of Comparative Examples 4 to 6 and 8, excluding Comparative Example 7, in which experimentation was impossible, began to release the dye which was clear enough to be identified with the unaided eye, immediately after being immersed in physiological saline, and after 5 minutes, most dye was released. In detail, as compared with Comparative Example 4, in which the calcium phosphate-based compound particles were used alone, when a predetermined amount of hydrogel was included, the degree was slightly reduced. In particular, in the composition of Comparative Example 5 including the hydrogel at as high as 70%, initial release was considerably inhibited, indicating that diffusion of the dye was physically inhibited by the hydrogel. In contrast, the graft material of Example 1 released a small amount of dye, but the degree was insignificant, and the released amount was significantly smaller than the results of other Comparative Examples. This result was also confirmed from FIG. 5, showing that the color of the graft material became pale. Taken together, in the composition of Example 1, even though the content of hydrogel was slightly low at 30%, the release of the dye was overall inhibited, suggesting that when a drug is loaded in the composition of Example 1, sustained release thereof may be achieved.

EXPERIMENTAL EXAMPLE 3: Comparison of Yield Stress in Fluid

[0076] The same force (shear stress) was applied using a rheometer to the graft material composed of the composition of Comparative Example 6, which is a commercially available product, and the graft material composed of the composition of Example 1, in which calcium phosphate-based compound macroparticles were additionally included to increase the content thereof. At this time, the shear strain of each formulation was measured and shown in FIG. 7. As shown in FIG. 7, it was confirmed that when the same force was applied, the deformation of the control group was more severe than that of the specimen of Example 1. This indicates that the formulation of Example 1 is able to maintain its shape without structural decomposition, when in contact with water or blood flow in the in vivo environment in which it is implanted, that is, when a physical force is applied, and therefore, a drug, e.g., BMP-2, loaded therein may be sustained-released.

EXPERIMENTAL EXAMPLE 4: Comparison of Strength According to Particle Size of calcium phosphate Compound

[0077] In order to examine changes in the strength of the composition of Example 1 in which the content of calcium phosphate-based compound was increased by additionally including macroparticles in addition to calcium phosphate-based compound microparticles, the composition of Example 1 in which the content of the calcium phosphate-based compound was increased to 70% by including both microparticles and macroparticles, the composition of Comparative Example 6 in which the content of the calcium phosphate-based compound was 50% by including only microparticles, and the composition of Comparative Example 8 in which the content of the calcium phosphate-based compound was 50% by including only macroparticles were measured for compressive strength, and the results are shown in FIG. 8. In detail, specimens of 8 mm×10 mm in size were prepared by using each composition, and deformation under compression was measured, as shown at the top of FIG. 8. As shown in FIG. 8, when Comparative Examples 6 and 8 were compared with each other, Comparative Example 8 showed remarkably improved strength, in which the composition had the same content, but the particle had the larger size. In contrast, the composition of Example 1 including both microparticles and macroparticles showed improved strength due to the increased content thereof, because even though microparticles were included, they were mixed with the macroparticles, as compared to that of Comparative Example 8.

[0078] Based on the above description, it will be understood by those skilled in the art that the present disclosure may be implemented in a different specific form without changing the technical spirit or essential characteristics thereof. Therefore, it should be understood that the above embodiment is not limitative, but illustrative in all aspects. The scope of the disclosure is defined by the appended claims rather than by the description preceding them, and therefore all changes and modifications that fall within metes and bounds of the claims or equivalents of such metes and bounds are therefore intended to be embraced by the claims.