Method to increase radial strength of a bioresorbable scaffold

Patent metadata

Field	Value
Publication number	US-10099431-B2
Application number	US-201514832283-A
Country	US
Kind code	B2
Filing date	Aug 21, 2015
Priority date	Aug 21, 2015
Publication date	Oct 16, 2018
Grant date	Oct 16, 2018

Abstract

Methods of fabricating a polymer scaffold with increased radial strength including steps of elongation or strain of a biaxially oriented tube and annealing or thermal processing of the strained tube at a constant strain are disclosed. The steps of elongation and thermal processing increase axial direction chain orientation and lamellar crystal growth, increase radial strength, and decrease the thickness of the tube. The method allows fabrication of a scaffold with thinner struts which provide sufficient radial strength.

First claim

What is claimed is:

1. A method of a fabricating a scaffold comprising:
forming a tube having an initial diameter made of a bioresorbable polymer by extrusion;
after forming the tube, radially expanding the tube from the initial diameter to an expanded diameter, wherein the radial expansion step increases a crystallinity of the tube, and wherein the expanded tube has a thickness;
elongating the expanded tube to a predetermined axial strain along its cylindrical axis by applying a tensile force to the expanded tube along its cylindrical axis, wherein the elongating decreases the thickness of the tube;
thermally processing the elongated tube while the tube is fixed at the predetermined axial strain for a selected time at a temperature between a glass transition temperature (Tg) of the polymer and a melting temperature (Tm) of the polymer, wherein the thickness of the tube after the thermal processing is less than the thickness of the expanded tube,
wherein the thermal processing increases the thickness of the tube to a desired thickness of 80 to 120 microns,
wherein the predetermined axial strain is adjusted so that the decrease in thickness from the elongating and the increase in thickness from the thermal processing results in the desired thickness; and
cutting a scaffold pattern in the thermally processed tube to form the scaffold.

2. The method of claim 1 , wherein the elongating is performed at a temperature between Tg and Tm of the polymer.

3. The method of claim 1 , wherein the selected time is 5 min to 20 min.

4. The method of claim 1 , wherein a weight average molecular weight (Mw) of the polymer is 200 to 600 kDa.

5. The method of claim 1 , wherein an Mw of the polymer is 600 to 1500 kDa.

6. The method of claim 1 , wherein the thickness of the expanded tube is between 140 and 180 microns.

7. The method of claim 1 , wherein the crystallinity of the tube prior to elongating is 20 to 50%.

8. The method of claim 1 , wherein the elongating and thermal processing increase the crystallinity of the polymer by 1 to 10%.

9. The method of claim 1 , wherein the elongating and thermal processing increase a strength and modulus of the polymer.

10. The method of claim 1 , wherein the predetermined axial strain is 5 to 25%.

11. The method of claim 1 , wherein the expanded diameter of the tube is fixed during the elongating and thermal processing.

12. The method of claim 1 , wherein the expanded diameter of the tube decreases by no more than 1% during the elongating and thermal processing.

13. The method of claim 1 , wherein the expanded diameter of the tube decreases by at least 1 and no more than 10% during the elongating and thermal processing.

14. The method of claim 1 , further comprising disposing the expanded tube over a mandrel having a diameter less than the expanded diameter, wherein the expanded diameter of the tube decreases to the diameter of the mandrel during the elongating and thermal processing.

15. The method of claim 1 , wherein the polymer is poly(L-lactide) (PLLA).

16. The method of claim 1 , wherein the polymer is a blend of PLLA and poly(L-lactide-co-caprolactone).

Assignees

• Abbott Cardiovascular Systems Inc

Inventors

• Hossainy Syed F A
• Gada Manish B

Classifications

• A61F2240/001

  Designing or manufacturing processes · CPC title

• A61F2002/91558

  connected peak to peak · CPC title

• B29K2995/0088

  Molecular weight · CPC title

• A61F2002/91533

  characterised by the phase between adjacent bands · CPC title

• B29K2995/0056

  Biocompatible, e.g. biopolymers or bioelastomers · CPC title