Crimping polymer scaffolds

Patent metadata

Field	Value
Publication number	US-9931787-B2
Application number	US-201514857635-A
Country	US
Kind code	B2
Filing date	Sep 17, 2015
Priority date	Sep 18, 2014
Publication date	Apr 3, 2018
Grant date	Apr 3, 2018

Abstract

A polymer scaffold is crimped to a balloon while the polymer material is in a thermodynamically unstable state, or a transient state including crimping shortly after a tube or scaffold processing step that imparts memory to the material, or shortly after rejuvenation of the scaffold.

First claim

What is claimed is:

1. A method for making a medical device, comprising:
providing a tube made from a material comprising a polymer composition having a glass transition temperature (Tg), the tube being formed by, or modified by a forming process, wherein the forming process includes the step of at least one of raising the temperature of the tube to about, or greater than about Tg or radially straining the material beyond a yield strain for the material;
making a scaffold from the tube formed or modified by the forming process; and
crimping the scaffold to a balloon such that a significant plastic deformation is imposed on the scaffold when crimped to the balloon, including the steps of
reducing a scaffold diameter from a pre-crimp diameter to a first diameter,
rejuvenating the scaffold including radially expanding the scaffold diameter from the first diameter to a second diameter, and
reducing the scaffold diameter from the second diameter to a third diameter that is less than the first diameter.

2. The method of claim 1 , wherein the rejuvenating the scaffold includes radially expanding the scaffold diameter by about 5 to 15% relative to the pre-crimp diameter or the first diameter.

3. The method of claim 1 , wherein the rejuvenating includes inducing a strain beyond the yield strain for the material, wherein a crest of a scaffold ring has a highest yield strain of about 5 to 20% beyond the strain where yield begins to occur for the scaffold crest when the scaffold is radially expanded.

4. The method of claim 1 , wherein a scaffold temperature is about Tg or about 15 Deg. C less than Tg when the scaffold diameter is increased from the first diameter to the second diameter.

5. The method of claim 1 , wherein the scaffold diameter is increased from the first diameter to the second diameter by inflating the balloon.

6. The method of claim 1 , wherein a wall thickness of the scaffold during crimping is less than about 120 microns.

7. The method of claim 1 , wherein an aspect ratio (AR) of strut width to wall thickness of a strut of the scaffold is between about 1 to 2.2.

8. The method of claim 1 , wherein the tube is substantially or completely a blend of polylactide (PLA) and a PLA and polycaprolactone (PCL) random copolymer (20% PCL) and the blended PLA-PCL combination has between about 1% to 5% by weight PCL; or the tube comprises substantially high molecular Weight poly(L-lactide).

9. The method of claim 1 , wherein the forming process induces a biaxial orientation of polymer chains to increase a radial strength in the tube and the rejuvenation does not remove the biaxial orientation.

10. The method of claim 1 ,
wherein the rejuvenating the scaffold is performed using a balloon catheter comprising the balloon to which the scaffold is crimped, or
wherein the balloon is a second balloon, and wherein the rejuvenating the scaffold is performed using a first balloon catheter comprising a first balloon and the crimping the scaffold is performed using a second balloon catheter comprising the balloon to which the scaffold is crimped, and the first balloon has a higher nominal diameter of the second balloon.

11. A method for crimping, comprising
providing a scaffold comprising a polymer having a glass transition temperature (Tg); and
placing the scaffold within a crimping device and while the scaffold is within the crimping device performing the steps of:
raising a temperature of the scaffold to between about 10 to 20 degrees above Tg, followed by lowering the scaffold temperature to a lower temperature between about Tg and 15 degrees below Tg; and
while the scaffold has the lower temperature crimping the scaffold including reducing a scaffold diameter from a first diameter to a second diameter.

12. The method of claim 11 , wherein the scaffold has biaxially orientated polymer chains before and after raising the temperature of the scaffold to between about 10 to 20 degrees above Tg.

13. The method of claim 11 , wherein the scaffold temperature is raised and then maintained at a raised temperature to rejuvenate the scaffold, including raising the temperature of the scaffold to between about 10 to 20 degrees above Tg and maintaining the temperature for less than 10 minutes.

14. The method of claim 11 , wherein the scaffold is disposed on an inflated balloon while the scaffold diameter is reduced from the first diameter to the second diameter.

15. A method of crimping, comprising:
providing a scaffold comprising a biodegradable polymer,
rejuvenating the scaffold, wherein the rejuvenation puts the polymer into a thermodynamic non-equilibrium state, thereby reversing a physical ageing of the scaffold; and
using an iris-type crimping mechanism,
crimping the scaffold including reducing a diameter of the scaffold from a pre-crimp diameter to a first diameter within one day of rejuvenating the scaffold, wherein the crimping produces a crimped scaffold,
removing the crimped scaffold from the crimping mechanism, and
placing the crimped scaffold in a sheath to reduce recoil of the crimped scaffold.

16. The method of claim 15 , wherein the crimping the scaffold occurs within 60 sec to 60 min after the rejuvenating the scaffold.

17. The method of claim 15 , wherein the scaffold is rejuvenated while the scaffold is disposed within a crimp head of the crimping mechanism.

18. The method of claim 15 , wherein the scaffold is rejuvenated shortly before placing the scaffold within a crimp head of the crimping mechanism.

19. The method of claim 15 , wherein the polymer comprises biaxially orientated polymer chains before and after rejuvenation.

20. The method of claim 15 , wherein the rejuvenating the scaffold increases a crystallinity of the polymer by 0.6% to 2%.

21. The method of claim 15 , wherein the polymer has a glass transition temperature (Tg) and the rejuvenating the scaffold step includes a thermal treatment, including
applying heat to the scaffold to raise a temperature of the scaffold to between about 10 to 20 degrees above Tg and maintaining the temperature for between about 5 to 20 minutes.

22. The method of claim 21 , wherein the scaffold is disposed on a rod during the thermal treatment, wherein the rod is thermally insulated such that about no heat is lost by thermal conductivity from the scaffold to the rod during the thermal treatment.

23. The method of claim 22 , wherein the outer diameter of the rod is about the same as an inner diameter of the scaffold prior to the thermal treatment.

24. The method of claim 22 , wherein the scaffold is made from a radially expanded precursor tube, such that the thermal treatment causes an inner diameter of the scaffold to decrease during the thermal treatment.

25. The method of claim 24 , wherein the rod imposes a radial constraint on the scaffold during the thermal treatment to cause a crown angle of the scaffold to increase during the thermal treatment.

26. The method of claim 15 , wherein the polymer is a first polymer and has a glass transition temperature (Tg) and the rejuvenating the scaffold step comprises coating the scaffold with a second polymer followed by drying a coating comprising the second polymer within one day of the reducing the scaffold diameter, wherein the drying the coating comprises raising a scaffold temperature to a temperature of between about 10 to 20 degrees above Tg.

27. The method of claim 15 , wh

Assignees

• Abbott Cardiovascular Systems Inc

Inventors

• Harrington Joel
• Mccoy Jill

Classifications

• B29C71/0009

  using liquids, e.g. solvents, swelling agents (spectacle cases, e.g. for cleaning contact lenses A45C11/04; disinfecting or sterilising contact lenses A61L12/00, using liquid substances A61L2/20; cleaning involving the use of liquid in general B08B3/00; for hydrating contact lenses B29D11/00067) · CPC title

• A61F2/9522

  Means for mounting a stent or stent-graft onto or into a placement instrument · CPC title

• B23K26/38

  by boring or cutting · CPC title

• Y10T29/49929

  Joined to rod · CPC title

• A61F2240/001

  Designing or manufacturing processes · CPC title