Method for extending shelf-life of constructs of semi-crystallizable polymers

• US 7,297,758 B2
• Filed: 08/02/2005
• Issued: 11/20/2007
• Est. Priority Date: 08/02/2005
• Status: Expired due to Fees

• Current Assignee: Advanced Cardiovascular Systems Incorporated
• Original Assignee: Advanced Cardiovascular Systems Incorporated
• Inventors: Kleine, Klaus, Huang, Bin, Hossainy, Syed Faiyaz Ahmed, Gale, David C.
• Primary Examiner(s): BOYKIN, TERRESSA M
• Application Number:
  US11/195,974
• Publication Number:
  US 20070032634A1
• Time in Patent Office: 840 Days
• Field of Search: 264/176.1, 264/219, 424/422, 424/426, 528/480, 606/108, 623/1.15
• US Class Current: 528/480
• CPC Class Codes: A61L 31/06 obtained otherwise than by reactions only involving carbon-to-carbon unsaturated bonds A61L31/041 takes precedence
• CPC Class Codes: A61L 31/148 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 3/005 Processes for mixing polymers
• CPC Class Codes: C08L 2666/02 Organic macromolecular compounds, natural resins, waxes or and bituminous materials
• CPC Class Codes: C08L 67/04 Polyesters derived from hydroxycarboxylic acids, e.g. lactones C08L67/06 takes precedence

Abstract

This invention relates to a method of extending the shelf-life of constructs, in particular bioabsorbable stents, comprising semi-crystalline polymers by increasing the crystallinity of the polymers.

Claims

1. A method of extending the shelf-life of a polymeric construct comprising:

providing a polymeric construct comprising at least one semi-crystalline polymer;

determining a glass transition temperature (T_g) of each semi-crystalline polymer of the polymeric construct;

determining a melting temperature (T_m) of each semi-crystalline polymer of the polymeric construct;

heating the polymeric construct to a temperature between T_g and T_m of at least one of the semi-crystalline polymers;

holding the polymeric construct at the temperature until one or more of the polymers independently is above about 25% crystalline and,

removing the polymeric construct from the source of heat.

2. The method of claim 1, wherein the temperature is from about T_g+0.05(T_m−

T_g) to about T_g+0.4(T_m−

T_g).

3. The method of claim 2, wherein the temperature is from about T_g+0.17(T_m−

T_g) to about T_g+0.21(T_m−

T_g).

4. The method of claim 1, wherein the polymeric construct is held at the temperature until at least one of the semi-crystalline polymers comprising the polymeric construct is from about 40% to about 60% crystalline.

5. The method of claim 1, wherein the polymeric construct is held at the temperature until at least one of the semi-crystalline polymers comprising the polymeric construct is from about 45% to about 55% crystalline.

6. The method of claim 1, wherein one of the semi-crystalline polymers comprising the polymeric construct is poly(lactic acid).

7. The method of claim 6, wherein the polymeric construct is heated at from about 70°

C. to about 100°

C.

8. The method of claim 7, wherein the polymeric construct is heated at from about 75°

C. to about 95°

C.

9. The method of claim 8, wherein the polymeric construct is held at from about 75°

C. to about 95°

C. for from about 5 minutes to about 15 minutes.

10. The method of claim 9, wherein the polymeric construct is held at from about 75°

C. to about 95°

C. for from about 4 to about 7 minutes.

11. The method of either claim 9 or claim 10, wherein the poly(L-lactic acid) is from about 40% to about 45% crystalline after heating at.

12. The method of claim 1, wherein the construct is a medical device.

13. The method of claim 12, wherein the medical device is an implantable medical device.

14. The method of claim 13, wherein the implantable medical device is a stent.

15. The method of claim 1, wherein the polymeric construct comprises a layer of polymer(s), at least one of which is a semi-crystalline polymer, coated on an implantable medical device.

16. The method of claim 15, wherein one of the semi-crystalline polymers comprising the layer of polymer(s) is poly(lactic acid).

17. The method of claim 16, wherein the implantable medical device is a stent.

18. The method of claim 1, wherein crystallinity is determined by differential scanning calorimetry.