Process of making a resorbable implantation device

• US 5,290,494 A
• Filed: 07/16/1992
• Issued: 03/01/1994
• Est. Priority Date: 03/05/1990
• Status: Expired due to Fees

• Current Assignee: Board of Regents of the University of Texas System (University of Texas System)
• Original Assignee: Board of Regents of the University of Texas System (University of Texas System)
• Inventors: Boyan, Barbara D., Coombes, Allan G. A., Heckman, James D.
• Primary Examiner(s): Tentoni, Leo B.
• Application Number:
  US07/914,992
• Time in Patent Office: 593 Days
• Field of Search: 264/41, 264/49, 264/216, 264/344
• US Class Current: 264/41
• CPC Class Codes: A61F 2/28 Bones joints A61F2/30
• CPC Class Codes: A61F 2/3094 Designing or manufacturing processes
• CPC Class Codes: A61F 2002/2835 Bone graft implants for filling a bony defect or an endoprosthesis cavity, e.g. by synthetic material or biological material
• CPC Class Codes: A61F 2002/30004 the prosthesis being made from materials having different values of a given property at different locations within the same prosthesis
• CPC Class Codes: A61F 2002/30062 (bio)absorbable, biodegradable, bioerodable, (bio)resorbable, resorptive
• CPC Class Codes: A61F 2002/30065 thermoplastic, i.e. softening or fusing when heated, and hardening and becoming rigid again when cooled
• CPC Class Codes: A61F 2002/30113 circular
• CPC Class Codes: A61F 2002/302 toroidal, e.g. rings
• CPC Class Codes: A61F 2002/30225 Flat cylinders, i.e. discs
• CPC Class Codes: A61F 2002/30677 Means for introducing or releasing pharmaceutical products, e.g. antibiotics, into the body
• CPC Class Codes: A61F 2002/30772 Apertures or holes, e.g. of circular cross section
• CPC Class Codes: A61F 2002/30785 parallel
• CPC Class Codes: A61F 2210/0004 bioabsorbable
• CPC Class Codes: A61F 2210/0071 thermoplastic
• CPC Class Codes: A61F 2230/0006 circular
• CPC Class Codes: A61F 2230/0065 toroidal, e.g. ring-shaped, doughnut-shaped
• CPC Class Codes: A61F 2230/0069 cylindrical
• CPC Class Codes: A61F 2250/0014 having different values of a given property or geometrical feature, e.g. mechanical property or material property, at different locations within the same prosthesis
• CPC Class Codes: A61L 27/18 obtained otherwise than by reactions only involving carbon-to-carbon unsaturated bonds
• CPC Class Codes: A61L 27/52 Hydrogels or hydrocolloids
• CPC Class Codes: A61L 27/58 : Materials at least partially resorbable by the body
• CPC Class Codes: C08J 2367/04 : Polyesters derived from hydroxy carboxylic acids, e.g. lactones C08J2367/06 takes precedence
• CPC Class Codes: C08J 9/28 : by elimination of a liquid phase from a macromolecular composition or article, e.g. drying of coagulum
• CPC Class Codes: C08L 67/04 : Polyesters derived from hydroxycarboxylic acids, e.g. lactones C08L67/06 takes precedence
• CPC Class Codes: Y10T 428/249979 : Specified thickness of void-containing component [absolute or relative] or numerical cell dimension

Abstract

Resorbable materials and their preparation based on gelling a solution of a single polylactide enantiomer. The gel may be dried to produce solid materials, or may be extracted with a nonsolvent prior to drying to make microporous materials. Physical and mechanical properties of the material may be varied by varying the molecular weight of the gelling polymer, or by blending the gelling solution with other polymers or fillers. The resorbable materials can be used to make biodegradable implantation devices.

Claims

1. A method for making a resorbable implantation device, comprising the steps of:

dissolving an independently-gelling single polylactide enantiomer in a solvent to form a polymer solution;

casting the polymer solution in a mold;

allowing the polymer solution to cool to form a gel capable of substantially retaining the shape of the mold upon removal therefrom and handling thereof; and

drying the gel to form a resorbable implantation device.

6. The method of claim 1 or 2, wherein the solvent is acetone or ethyl acetate.

7. The method of claim 1 or 2, wherein the independently-gelling single polylactide enantiomer is dissolved in the solvent to a concentration of from about 1 to about 10% weight/volume.

8. The method of claim 1 or 2, wherein the independently-gelling single polylactide enantiomer is dissolved in the solvent to a concentration of from about 2.5 to about 10% weight/volume.

9. The method of claim 1 or 2, wherein the independently-gelling single polylactide enantiomer is dissolved in the solvent to a concentration of from about 7 to about 9% weight/volume.

10. The method of claim 1 or 2, wherein the independently-gelling single polylactide enantiomer is based on L-lactide.

11. The method of claim 1 or 2, wherein the independently-gelling single polylactide enantiomer is poly L-lactide).

12. The method of claim 1 or 2, wherein the independently-gelling single polylactide enantiomer is based on D-lactide.

13. The method of claim 1 or 2, wherein the independently-gelling single polylactide enantiomer is poly(D-lactide).

14. The method of claim 1 or 2, wherein the independently-gelling single polylactide enantiomer is a copolymer of lactide and another alpha-hydroxy acid.

15. The method of claim 14, wherein the other alpha-hydroxy acid comprises glycolic acid.

16. The method of claim 1 or 2, wherein the independently-gelling single polylactide enantiomer has a weight average molecular weight of between about 50,000 and 200,000.

17. The method of claim 1 or 2, wherein the independently-gelling single polylactide enantiomer has a weight average molecular weight of around 100,000.

18. The method of claim 1 or 2, wherein a second material is dissolved in the solvent before the gel forming step.

19. The method of claim 18, wherein the ratio of the independently-gelling single polylactide enantiomer to the second material is at least about 1:

9.

20. The method of claim 18, wherein the second material comprises a polymer.

21. The method of claim 20, wherein the second polymer comprises a polymer of an alpha-hydroxy acid, a polymer of a lactone, a copolymer at least one alpha-hydroxy acid, a polyethylene oxide, or a copolymer containing a thermoplastic elastomer.

22. The method of claim 1 or 2, wherein a filler material is added to the solvent before the gel forming step.

23. The method of claim 1 or 2, wherein the molded gel has a minimum thickness of at least about 2 mm.

24. The method of claim 1 or 2, wherein the molded gel has a minimum thickness of at least about 5 mm.

25. The method of claim 1 or 2, wherein the molded gel has a minimum thickness of at least about 10 mm.

26. The method of claim 1, wherein the drying step comprises:

partially drying the gel;

extracting the solvent molecules with water to form a microporous material; and

drying the water extracted microporous material.

30. The method of claim 1 or 28, further comprising the step of forming at least one bore in the gel.

32. The method of claim 1, 2, 28, or 29, further comprising the step of incorporating a bioactive material into the resorbable implantation device.

2. A method for making a resorbable implantation deice, comprising the steps of:

dissolving an independently-gelling single polylactide enantiomer in a solvent to form a polymer solution;

casting the polymer solution in a mold;

allowing the polymer solution to cool to form a gel capable of substantially retaining the shape of the mold upon removal therefrom and handling thereof;

extracting the solvent with a nonsolvent such that the polymer precipitates to form a substantially microporous material; and

drying the microporous material to form a resorbable implantation device.

3. The method of claim 2, wherein the nonsolvent is organic.

4. The method of claim 3, further comprising the step of, after the extracting step and before the drying step, immersing the microporous material in water to extract the organic nonsolvent molecules.

5. The method of claim 2, wherein the nonsolvent is water.

27. The method of claim 2, wherein the drying step comprises:

partially drying the microporous material;

extracting the nonsolvent molecules with water; and

drying the water extracted microporous material.

31. The method of claim 2 or 29, further comprising the step of forming at least one bore in the microporous material.

28. A method for making a resorbable implantation device, comprising the steps of:

heating an independently-gelling single polylactide enantiomer, having a weight average molecular weight of between about 50,000 and 200,000, in acetone or ethyl acetate, such that said enantiomer dissolves in the acetone or ethyl acetate to form a polymer solution;

casting the polymer solution in a mold;

allowing the polymer solution to cool to form a gel capable of substantially retaining the shape of the mold upon removal therefrom and handling thereof; and

drying the gel to form a resorbable implantation device.

29. A method for making a resorbable implantation device, comprising the steps of:

heating an independently-gelling single polylactide enantiomer, having a weight average molecular weight of between about 50,000 and 200,000, in acetone or ethyl acetate, such that said enantiomer dissolves in the acetone or ethyl acetate to form a polymer solution;

casting the polymer solution in a mold;

allowing the polymer solution to cool to form a gel capable of substantially retaining the shape of the mold upon removal therefrom and handling thereof;

extracting the acetone or ethyl acetate with a nonsolvent such that the polymer precipitates to form a substantially microporous material; and

drying the microporous material to form a resorbable implantation device.