Shape memory bioresorbable polymer peripheral scaffolds
Bioabsorbable scaffolds having high crush recoverability, high fracture resistance, and reduced or no recoil due to self expanding properties at physiological conditions are disclosed. The scaffolds are made from a random copolymer of PLLA and a rubbery polymer such as polycaprolactone.
1. A stent, comprising:
a scaffold formed from a polymer tube and configured for being crimped to a balloon,
the scaffold having a pattern of interconnected struts, and
the scaffold having an expanded diameter when expanded from a crimped state by the balloon,
wherein the scaffold attains greater than about 80% of the expanded diameter after being crushed to at least 50% of the expanded diameter; and
wherein the scaffold is made from a shape memory random copolymer of poly(L-lactide) (PLLA) and a rubbery polymer that is 0.1 to 10 wt % or mol % of the copolymer, and
wherein the scaffold exhibits self-expanding properties at 37 degrees C. in physiological conditions;
wherein the struts form undulating rings having crowns and the rings are interconnected by longitudinally extending links, wherein the crowns include W-crowns, Y-crowns, and free crowns;
wherein a first link connects a first ring to an adjacent ring, the first link forms with the first ring a W-crown, and the first link forms with the adjacent ring a Y-crown;
wherein a free crown is not connected to a link; and
wherein a ring comprises a sequence of immediately adjacent crowns arranged about a circumference of the ring and in the following order: W-crown, 3 free crowns, Y-crown, 3 free crowns, and W-crown.
2. The stent of claim 1 , wherein a glass transition temperature (Tg) of the copolymer is between 37 degrees C. and 55 degrees C.
3. The stent of claim 1 , wherein the rubbery polymer has a Tg less than 25 degrees C.
4. The stent of claim 1 , wherein a glass transition temperature (Tg) of the copolymer changes by less than 15% from a dry to a wet state.
5. The stent of claim 1 , wherein the rubbery polymer is polycaprolactone.
6. The stent of claim 1 , wherein the rubbery polymer comprises monomeric, oligomeric, or polymeric units from the group consisting of polyhydroxyalkanoates (PHA), poly(4-hydroxybutyrate) (P4HB), poly(trimethylene carbonate) (PTMC), poly(butylene succinate) (PBS), polyurethanes, polyethylene glycol (PEG), and poly(p-dioxanone) (PDO).
7. The stent of claim 1 , wherein a weight average molecular weight of the copolymer is between 60 and 150 kDa.
8. The stent of claim 1 , wherein in an as-fabricated state:
the scaffold has an outer diameter of 8 to 10 mm, crown angles for the rings are between 90 and 115 degrees, and the scaffold has a wall thickness of at least 0.008 in.
9. The stent of claim 1 , wherein the scaffold pattern includes a plurality of rings and links connecting one ring to another ring, wherein the scaffold pattern forms closed cells, wherein a closed cell has 12 free crowns, a Y crown and a W crown, and wherein the Y crown is aligned with the W crown.
10. The stent of claim 1 , and wherein any of the crowns have a maximum crown angle of between about 90 degrees and 115 degrees when the scaffold has the expanded diameter.
11. The stent of claim 10 , wherein the scaffold has a wall thickness of between 0.008 inches and 0.014 inches and a diameter of between 5 to 10 mm.