Methods for improved stent retention

Abstract

Methods for improved stent retention on an expandable member during delivery are disclosed. Methods include fabricating delivery systems including a degradable or water soluble sheath over the stent, the expandable member, or both for improving retention of the stent on the expandable member during delivery.

1 . A method of fabricating a stent delivery assembly, comprising:
 disposing a sheath over a stent positioned over a support member, the sheath comprising a degradable or water soluble polymeric material, wherein the stent is a scaffolding made from a polymeric scaffolding material, wherein the sheath fits loosely over the stent; and   heating the sheath to cause the sheath to shrink radially over the stent so that the sheath can retain the stent on the support member during delivery of the stent within a bodily lumen.   
     
     
         2 . The method of  claim 1 , wherein the support member is an expandable member. 
     
     
         3 . The method of  claim 1 , wherein the polymeric scaffolding material comprises a biostable polymer. 
     
     
         4 . The method of  claim 1 , wherein the polymeric scaffolding material comprises a biodegradable polymer. 
     
     
         5 . The method of  claim 1 , wherein the polymeric material of the sheath has a lower Tg or Ts than the polymeric material of the scaffolding. 
     
     
         6 . The method of  claim 1 , wherein the polymeric material of the sheath has a higher Tg or Ts than the polymeric material of the scaffolding. 
     
     
         7 . The method of  claim 1 , wherein the sheath shrinks radially over the stent so that the sheath is in contact with the stent to provide a tight fit over the stent. 
     
     
         8 . The method of  claim 1 , wherein the sheath is heated to a temperature to cause the sheath to stick to the stent. 
     
     
         9 . The method of  claim 1 , wherein the sheath is heated to a temperature close to or at a Tg or a Ts of the polymeric material of the sheath. 
     
     
         10 . The method of  claim 1 , wherein the sheath is heated to a temperature above a Tg or a Ts of the polymeric material of the sheath. 
     
     
         11 . The method of  claim 1 , wherein the sheath has an axial length shorter than the stent. 
     
     
         12 . The method of  claim 1 , wherein the sheath has an axial length longer than the stent. 
     
     
         13 . The method of  claim 1 , wherein the sheath has an axial length the same as the stent. 
     
     
         14 . The method of  claim 1 , wherein the sheath wall is flexible enough such that the sheath wall protrudes through gaps in the scaffolding. 
     
     
         15 . The method of  claim 1 , wherein the sheath comprises an active agent including an anti-inflammatory agent, anti-proliferative agent, antithrombogenic agent, or combinations thereof. 
     
     
         16 . The method of  claim 1 , wherein the sheath comprises a degradable polymeric material. 
     
     
         17 . The method of  claim 1 , wherein the polymeric material of the sheath has a Tg or Ts less than an ambient temperature. 
     
     
         18 . The method of  claim 1 , wherein the polymeric material of the sheath has a Tg between ambient and body temperature. 
     
     
         19 . The method of  claim 1 , wherein the polymeric material of the sheath has a Tg between body temperature and a Tg of the polymeric material of the scaffolding. 
     
     
         20 . The method of  claim 1 , wherein the polymeric material of the sheath is selected from the group consisting of Polyglycolide (PGA), Poly(L-lactide) (PLLA), Poly(DL-lactide) (PDLLA), Polycaprolactone (PCL), Polydioxanone (PDO), Poly(glycolide-trimethylene carbonate) (P(GA-TMC), 85/15 PDLLA-PGA Blend, 75/25 PDLLA-PGA Blend, 65/35 PDLLA-PGA Blend, 50/50 PDLLA-PGA Blend, PCL, PTMC, PDO, PHB, PCL-co-PTMC, PCL-co-PDO, PCL-co-PDLA, PCL-co-PTMC, PCL-co-PEG-co-PCL, and combinations thereof. 
     
     
         21 . The method of  claim 1 , wherein the polymeric material of the scaffolding is PLLA. 
     
     
         22 . The method of  claim 1 , wherein the polymeric material of the sheath is selected from the group consisting of water soluble polyurethane adhesives made from a reaction of a diisocyanate with poly(ethylene oxide), poly(vinylmethylether) or poly(2-ethyl-2-oxazoline); polymers and copolymers of crylamide, acrylic acid, malelic acid, vinyl acetate, crotonic acid, vinylimidazole, maleic anhydride and vinylpyrrolidone, polysaccharides, hydroxyethylcelluloses, carboxymethylcelluloses, polymeric salts, polyvinyl alcohol, polyethylene glycol, polyethylene oxide, glucose, dextran, dextrose, lactose, gamma globulin, ambumin, and combinations thereof.