Biodegradable endoprosthesis and methods for their fabrication
The disclosure provides biodegradable implantable devices such as a stent comprising a biodegradable polymeric wherein the polymeric material is treated to control crystallinity and/or Tg. The stent is capable to expand at body temperature in a body lumen from a crimped configuration to a deployed diameter and have sufficient strength to support a body lumen.
1. An expandable biodegradable stent, comprising:
a tubular biodegradable polymeric material, said expandable stent at body temperature being expandable from a crimped configuration to a deployed configuration in a body lumen and having sufficient strength to support the body lumen after an inward recoil of the stent from said deployed configuration, wherein the stent further self expands after said recoil to a second larger configuration.
2. The expandable stent of claim 1 wherein the polymeric material is treated to control one or more of crystallinity, transition temperature (T g ), or molecular weight.
3. The expandable stent of claim 2 wherein the polymeric material has a T g between 37° C. and 44° C.
4. The expandable stent of claim 2 wherein the polymeric material has a molecular weight between 30 kDa and 700 kDa.
5. The expandable stent of claim 2 , wherein the treatment comprises at least one of heating, heating and cooling, cooling, solvent removal, solvent incorporation, pressurization with gas, exposure to radiation, or expansion of the polymeric material to about 1 to 1.5 times a stent deployed diameter.
6. The expandable stent of claim 5 wherein the treatment comprises heating and cooling.
7. The expandable stent of claim 6 wherein the heating temperature is above Tg of the polymeric material.
8. The expandable stent of claim 2 wherein the polymeric material does not exhibit substantial phase separation after treatment.
9. The expandable stent of claim 2 wherein the crystallinity is controlled at a level between 5%-30%.
10. The expandable stent of claim 1 wherein the expandable stent expands to the second larger configuration within about 24 hours.
11. The expandable stent of claim 1 wherein the polymeric material comprises at least one co-polymer.
12. The expandable stent of claim 11 wherein the polymeric material further comprises from 0.1 to 10% (by weight) of monomer or polymer.
13. The expandable stent of claim 12 wherein the polymeric material comprises 1 to 100 micrograms of monomer or polymer per milligram of polymeric material.
14. The expandable stent of claim 12 , wherein the further monomer or polymer is blended with the at least one co-polymer of the polymeric material.
15. The expandable stent of claim 12 , wherein the further monomer or polymer is at least one of: lactide, glycolide, polylactide-co-glycolide, caprolactone, polylactide-co-caprolactone, or polyglycolide-co-caprolactone.
16. The expandable stent of claim 1 wherein the polymeric material is selected from the group consisting of a polymer of lactic acid; a polymer of polyglycolic acid; a polymer of polylactic glycolic acid; a copolymer of a lactide and a glycolide; a copolymer of lactide and caprolactone; a copolymer of glycolide and caprolactone; a copolymer of a lactide, a glycolide and caprolactone; a blend of a lactide and a glycolidel a blend of lactide and caprolactone; a blend of a glycolide and caprolactone; and a blend of a lactide, a glycolide and caprolactone.
17. The expandable stent of claim 16 wherein the polymeric material comprises 80-99% by weight of a lactide.
18. The expandable stent of claim 16 wherein the polymeric material further comprises 1-20% by weight of a caprolactone.
19. The expandable stent of claim 16 wherein the polymeric material further comprises 1-20% by weight of a glycolide.
20. The expandable stent of claim 1 wherein the polymeric material further comprises between 0.1% and 10% (by weight) of at least one solvent.
21. The expandable stent of claim 1 wherein the stent self expands prior to expansion to the deployed configuration.
22. The expandable stent of claim 1 wherein the stent has inward recoil from the deployed configuration between 3% and 10%.
23. The expandable stent of claim 1 wherein the stent has a nominal expanded configuration with a transverse dimension and the deployed configuration has a transverse dimension that is 1 to 1.5 times the transverse dimension of the nominal expanded configuration.
24. The expandable stent of claim 1 wherein the transverse dimension of the deployed configuration ranges from 3 mm to 25 mm.
25. The expandable stent of claim 1 wherein the stent is expanded to the deployed configuration by balloon expansion.
26. The expandable stent of claim 1 wherein the second larger configuration has a transverse dimension of at least 5% greater than the transverse dimension of the deployed configuration.
27. The expandable stent as in claim 1 wherein the stent expands to the second larger configuration between 1 month and 1 year.
28. The expandable stent of claim 1 wherein the polymeric material has an elastic modulus ranging from 0.35 GPa to 1.5 GPa.
29. The expandable stent of claim 1 mounted on a balloon of a balloon catheter in the crimped configuration.