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 retention layer 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:
 providing a stent including a stent substrate with a retention layer comprising a polymeric material,   wherein the stent substrate is composed of a pattern of interconnecting struts,   the retention layer disposed over the luminal surface and the sidewall surface of the struts with the abluminal surface of the struts free of the retention layer;   disposing the stent over an expandable member, wherein the stent disposed on the expandable member comprises a delivery assembly; and   heating the delivery assembly to increase the temperature of the retention layer, wherein the retention layer is heated to a temperature close to, at or above a Tm, a Tg, or a Ts of the polymeric material of the retention layer, the retention layer facilitating adhesion of the stent to the expandable member.   
     
     
         2 . The method of  claim 1 , wherein the stent substrate comprises a biostable polymer, biodegradable polymer, or a combination thereof. 
     
     
         3 . The method of  claim 2 , wherein the polymeric material of the retention layer has a lower Tg or Ts than the polymeric material of the stent substrate. 
     
     
         4 . The method of  claim 1 , wherein the expandable member comprises a polymeric material, wherein the polymeric material of the retention layer has a lower Tg or Ts than the polymeric material of the expandable member. 
     
     
         5 . The method of  claim 1 , wherein disposing the stent over the expandable member comprises crimping the stent over the expandable member. 
     
     
         6 . The method of  claim 5 , wherein the crimping device performs the heating of the delivery assembly. 
     
     
         7 . The method of  claim 1 , wherein the delivery assembly is heated by a heated fluid conveyed into the expandable member. 
     
     
         8 . The method of  claim 1 , wherein the expandable member further comprises a retention layer comprising a polymeric material, wherein the expandable member retention layer facilitates adhesion of the stent to the expandable member. 
     
     
         9 . The method of  claim 1 , wherein the retention layer polymeric material 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. 
     
     
         10 . The method of  claim 1 , wherein portions of the expandable member protrude through gaps in the pattern of the stent and adhere to the retention layer on the sidewall surface of the struts facilitating retention of the stent on the balloon. 
     
     
         11 . A method of fabricating a stent delivery assembly, comprising:
 providing a stent including a stent substrate;   disposing the stent over an expandable member, the expandable member including a retention layer comprising a polymeric material,   the retention layer disposed selectively over the surface of the expandable member as rings around the circumference of the expandable member,   wherein the stent disposed on the expandable member comprises a delivery assembly; and   heating the delivery assembly to increase the temperature of the retention layer, wherein the retention layer is heated to a temperature close to, at or above a Tm, a Tg, or a Ts of the polymeric material of the retention layer, the retention layer facilitating adhesion of the stent to the expandable member.   
     
     
         12 . The method of  claim 11 , wherein the stent substrate comprises a biostable polymer, biodegradable polymer, or a combination thereof. 
     
     
         13 . The method of  claim 12 , wherein the polymeric material of the retention layer has a lower Tg or Ts than the polymeric material of the stent substrate. 
     
     
         14 . The method of  claim 11 , wherein the polymeric material of the retention layer has a lower Tg or Ts than the polymeric material of the expandable member. 
     
     
         15 . The method of  claim 12 , wherein disposing the stent over the expandable member comprises crimping the stent over the expandable member. 
     
     
         16 . The method of  claim 15 , wherein the crimping device performs the heating of the delivery assembly. 
     
     
         17 . The method of  claim 15 , wherein the delivery assembly is heated by a heated fluid conveyed into the expandable member. 
     
     
         18 . The method of  claim 11 , wherein the retention layer polymeric material 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. 
     
     
         19 . The method of  claim 11 , wherein the stent comprises a stent retention layer comprising a polymeric material, the stent retention layer including a polymeric material that facilitates adhesion of the stent to the expandable member. 
     
     
         20 . The method of  claim 11 , wherein the stent substrate is composed of a plurality of rings composed of struts, wherein the retention layer rings are disposed so as to maximize contact of the luminal surface of the rings of the stent.