Polymer-based stent assembly
Methods for preparing a polymer-based stent assembly comprising an inflatable balloon catheter and a polymer-based stent resistant to relaxation-related negative recoil are provided. The methods comprise heating a polymeric cylindrical device which is at a final predetermined shape and diameter to a temperature sufficiently above the glass transition temperature (Tg) of the polymer and for a time sufficient to erase any memory of previous processing of the polymeric cylindrical device and then quenching the polymeric cylindrical device to provide an educated polymeric cylindrical device having a memory of the final predetermined diameter and shape, mounting the educated cylindrical device on an inflatable balloon catheter, reducing the diameter of the educated cylindrical device by heating to a temperature at or slightly above the Tg of the polymer while evenly applying pressure on the exterior surface of the wall of the cylindrical device, and then cooling the cylindrical device below the Tg of the polymer to provide a stent assembly comprising an inflatable balloon catheter and an expandable, educated, polymeric stent snugly and stably disposed thereon. Assemblies comprising an inflatable balloon and a polymer based stent that is substantially resistant to relaxation related recoil mounted snugly on the balloon are also provided.
1. A degradable and bioresorbable polymeric stent that is substantially resistant to relaxation-related negative recoil when expanded mechanically to a final predetermined diameter in a lumen of a tube, duct, or vessel of a mammalian subject, said polymeric stent being formed by the following steps:
(a) heating a polymeric stent, which is at the final predetermined diameter to a temperature sufficiently above the Tg of a polymeric material that forms said polymeric stent, for a time sufficient to erase memory of previous processing of said polymeric stent; and
wherein said polymeric stent has a wall defining a first open end, a second open end, and a channel connecting said first and second open ends;
wherein said polymeric stent is mounted on a solid support for maintaining said polymeric stent at the final predetermined diameter;
(b) rapidly cooling said polymeric stent at a temperature below the Tg of the polymeric material to quench said polymeric stent and provide a polymeric stent that lacks any former process-related memory and has a memory of the final predetermined diameter.
2. The polymeric stent of claim 1 , further comprising the step of:
(c) forming slits, voids, or open spaces in the wall of said polymeric stent prior to step (a) or after step (b) to provide a polymeric stent that is substantially resistant to relaxation-related negative recoil when mechanically expanded to the final predetermined diameter by inflation of a balloon that has been inserted into said channel of said polymeric stent and implanted in the lumen of a tube, duct, or vessel of a mammalian subject or stored at 37° C. for 4 weeks or more.
3. The polymeric stent of claim 1 , wherein said polymeric stent is prepared before it is mounted on a balloon catheter.