Method of making a poly(L-lactide) stent with tunable degradation rate

Patent metadata

Field	Value
Publication number	US-9844612-B2
Application number	US-201715597962-A
Country	US
Kind code	B2
Filing date	May 17, 2017
Priority date	Jul 21, 2009
Publication date	Dec 19, 2017
Grant date	Dec 19, 2017

Abstract

Methods of treating with a biodegradable polymeric stent made from poly(L-lactide) and a low concentration of L-lactide monomer is disclosed. The concentration of L-lactide is adjusted to provide a degradation behavior that is suitable for different treatment applications including coronary, peripheral, and nasal.

First claim

What is claimed is:

1. A method of making a stent for treating a diseased section of a blood vessel, comprising:
extruding a polymer composition comprising poly(L-lactide) to form a tube;
processing the extruded tube to increase crystallinity of the tube to between 20-50%; and
laser cutting the processed tube to form a stent comprising a scaffolding, wherein the scaffolding comprises greater than 95 wt % poly(L-lactide) and between 0.05 to 0.5 wt % L-lactide monomer mixed, dispersed, or dissolved within the poly(L-lactide).

2. The method of claim 1 , wherein the processing comprises heating and radially expanding the extruded tube to induce orientation in the polymer.

3. The method of claim 2 , wherein the extruded tube is radially expanded to a degree of radial expansion of between 200-500%.

4. The method of claim 2 , wherein the extruded tube is heated to a temperature between 70° C. and 95° C. prior to expansion.

5. The method of claim 1 , wherein the scaffolding is composed of a pattern of struts, the pattern including a plurality of cylindrical rings connected by linking struts.

6. The method of claim 5 , wherein the struts have a rectangular cross-section, the cross-sectional area being between 20,000 and 25,000 μm 2 .

7. The method of claim 1 , wherein the number average molecular weight of the poly(L-lactide) of the scaffolding is between 60,000 and 300,000, relative to polystyrene standards.

8. The method of claim 1 , further comprising mixing the L-lactide monomer with the poly(L-lactide).

9. The method of claim 8 , wherein the mixing comprises mechanically blending the L-lactide monomer with the poly(L-lactide).

10. The method of claim 8 , wherein the L-lactide monomer is mixed with the poly(L-lactide) using solvent blending.

11. The method of claim 10 , wherein the solvent blending comprises:
making a master batch of the poly(L-lactide) and the L-lactide monomer having a concentration of the L-lactide monomer larger than a target concentration, wherein the master batch is made by dissolving the L-lactide monomer and the poly(L-lactide) in a solvent and evaporating the solvent to form the master batch which is a mixture of the poly(L-lactide) and the L-lactide monomer; and
making the polymer composition by mixing the master batch with an amount of the poly(L-lactide) that is sufficient to obtain the target L-lactide monomer concentration in the polymer composition.

12. The method of claim 1 , further comprising:
preparing a solution of the L-lactide monomer dissolved in a solvent;
spraying the solution on pellets of the poly(L-lactide);
removing the solvent to leave the L-lactide monomer deposited on the pellets; and
using the polymer with the deposited L-lactide monomer as the polymer composition for the extruding step.

Assignees

• Abbott Cardiovascular Systems Inc

Inventors

• Wang Yunbing
• Ma Xiao
• Oberhauser James

Classifications

• A61L31/148 Primary

  Materials at least partially resorbable by the body · CPC title

• A61K9/1647

  Polyesters, e.g. poly(lactide-co-glycolide) · CPC title

• A61F2/958

  Inflatable balloons for placing stents or stent-grafts · CPC title

• C09D167/04

  Polyesters derived from hydroxycarboxylic acids, e.g. lactones (C09D167/06 takes precedence) · CPC title

• B29L2031/7534

  Cardiovascular protheses · CPC title