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Last Updated: March 28, 2024

Claims for Patent: 9,119,903


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Summary for Patent: 9,119,903
Title:Porous composite with graded bioabsorbability, artificial bone using the same, and manufacturing method thereof
Abstract: The object of the present invention is to provide a calcium phosphate-collagen fiber composite which has an excellent mechanical property, can induce bone replacement by rapid bone remodeling, and can be used in a high-load region. The object can be solved by a porous composite comprising a calcium phosphate crystal and a collagen fiber at a weight ratio of 80:20 to 20:80, wherein (1) a bioabsorbability of the porous composite is graded, and (2) the density of the porous composite determined by gravimetric method is 300 to 1500 mg/cm.sup.3.
Inventor(s): Tanaka; Junzo (Tokyo, JP), Ikoma; Toshiyuki (Tokyo, JP), Yoshioka; Tomohiko (Tokyo, JP), Yoshida; Takashi (Tokyo, JP)
Assignee: TOKYO INSTITUTE OF TECHNOLOGY (Tokyo, JP)
Application Number:14/130,841
Patent Claims:1. A porous composite comprising a calcium phosphate crystal and a collagen fiber at a weight ratio of 80:20 to 20:80, wherein (1) a bioabsorbability of the porous composite is graded, and (2) the density of the porous composite determined by gravimetric method is 300 to 1500 mg/cm.sup.3.

2. The porous composite according to claim 1, wherein the gradation of bioabsorbability is represented by a strength ratio of two points in the porous composite, determined by an indentation test using a cylindrical probe with a diameter of 2 mm, and the strength ratio of the two points at a distortion rate of 30% is 1.5 or more.

3. The porous composite according to claim 1, wherein the bioabsorbability is continuously or discontinuously varied, the first piece of the composite having a higher bioabsorbability and the second piece of the composite having a lower bioabsorbability can be cut out of the porous composite, the gradation of bioabsorbability is represented by a ratio of bioabsorbabilities of the first piece to the second piece, and the ratio is 1.5 times or more.

4. The porous composite according to claim 3, wherein the bioabsorbability is a biodegradation rate determined by collagenase digestion, the biodegradation rate is represented by the following equation (I): Biodegradation rate=(W.sub.0-W.sub.t)/W.sub.0.times.100 (I) (wherein W.sub.0 and W.sub.t is both a dry weight before immersion and after immersion respectively, when the pieces of the porous composite are immersed in a collagenase solution of 2 unit/mL for 6 hours or in a collagenase solution of 200 units/mL for 30 minutes), the first piece is cut out of a region of 30% by weight of the porous composite having a higher biodegradation rate, the second piece is cut out of a region of 30% by weight of the porous composite having a lower biodegradation rate, and a ratio of biodegradation rates of the first piece to the second piece is 1.5 times or more.

5. The porous composite according to claim 3, wherein the bioabsorbability is denoted by a swelling ratio, the swelling ratio is represented by the following equation (II): Swelling ratio=(W.sub.w-W.sub.d)/W.sub.d.times.100 (II) (wherein W.sub.d and W.sub.w is a dry weight (W.sub.d) before immersion and a wet weight (W.sub.w) after immersion respectively, when the pieces of the porous composite are immersed in a phosphate-buffered saline for 24 hours), the first piece is cut out of a region of 30% by weight of the porous composite having a higher swelling ratio, the second piece is cut out of a region of 30% by weight of the porous composite having a lower swelling ratio, and a ratio of swelling ratios of the first piece to the second piece is 1.5 times or more.

6. The porous composite according to claim 1, wherein calcium phosphate is at least one calcium phosphate selected from the group consisting of hydroxyapatite, monocalcium phosphate anhydrous, monocalcium phosphate hydrate, dicalcium phosphate anhydrous, dicalcium phosphate hydrate, octacalcium phosphate, and tricalcium phosphate.

7. An artificial bone comprising the porous composite according to claim 1.

8. A method for preparing a porous composite, comprising the steps of: (A) forming a porous material containing calcium phosphate and collagen, and (B) cross-linking the porous material in a gradient manner through a cross-linking treatment capable of varying cross-link density, to obtain a porous composite having at least two regions wherein the ratio of bioabsorbabilities thereof is 1.5 times or more.

9. The method for preparing a porous composite according to claim 8, wherein the porous material forming step (A) comprises the steps of: (1) crystallizing calcium phosphate, to obtain a suspension of crystals or surface-modified crystals of calcium phosphate, (2) forming a collagen fibril from a soluble collagen in a collagen solution, to obtain a collagen fiber suspension, (3) mixing the collagen fibers suspension and the suspension of calcium phosphate crystals, to obtain a mixed suspension of calcium phosphate crystals and collagen fibers, and (4) forming the porous material from the mixed suspension of calcium phosphate crystals and collagen fibers.

10. The method for preparing a porous composite according to claim 8, wherein the porous material forming step (A) is a step of mixing calcium phosphate-collagen composite fibers, and a buffered solution, to gelate and form a porous material.

11. The method for preparing a porous composite according to claim 8, wherein the cross-linking in the gradient cross-linking step (B) is a cross-linking by a glutaraldehyde vapor deposition method, and a diffusion amount of glutaraldehyde gas into the porous material is varied, to prepare the porous composite having at least two regions wherein the ratio of bioabsorbabilities thereof is 1.5 times or more.

12. The method for preparing a porous composite according to claim 8, wherein the cross-linking in the gradient cross-linking step (B) is a cross-linking via irradiation, and the amount of irradiation to the porous material is varied under wet conditions, to prepare the porous composite having at least two regions wherein the ratio of bioabsorbabilities thereof is 1.5 times or more.

13. The method for preparing a porous composite according to claim 12, wherein the surface of the calcium phosphate crystal is modified with molecules with vinyl groups.

14. The method for preparing a porous composite according to claim 12, wherein calcium phosphate is at least one calcium phosphate selected from the group consisting of hydroxyapatite, monocalcium phosphate anhydrous, monocalcium phosphate hydrate, dicalcium phosphate anhydrous, dicalcium phosphate hydrate, octacalcium phosphate, and tricalcium phosphate.

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