Process of making a stent
View Patent ↗A stent or other prosthesis may be formed by coating a single continuous wire scaffold with a polymer coating. The polymer coating may consist of layers of electrospun polytetrafluoroethylene (PTFE). Electrospun PTFE of certain porosities may permit endothelial cell growth within the prosthesis.
1. A method of constructing a stent, the method comprising:
electrospinning a first tube of PTFE onto a rotating mandrel;
heating the first tube to between 360° C. to 400° C.;
applying a scaffolding structure around the first tube after the first tube has been heated;
applying a fluorinated ethylene propylene (FEP) layer around the first tube and the scaffolding structure; and
applying a second tube of porous PTFE around the FEP layer;
applying a compressive wrap around the second tube; and
heat-treating the stent above the melting temperature of FEP but below 325° C. while the compressive wrap is disposed around the second tube;
wherein the first tube of PTFE is an innermost tube of he stent that is configured for contact with bodily fluid.
2. The method of claim 1 , wherein the FEP partially coats fibers of the first and second tubes.
3. The method of claim 1 , wherein the second tube comprises electrospun PTFE formed by a method comprising:
electrospinning the second tube of PTFE onto a rotating mandrel; and
sintering the second tube.
4. The method of claim 1 , wherein electrospinning the first tube of PTFE comprises:
mixing a PTFE dispersion with PEO, wherein the PEO is dissolved in water to form a mixture; and
discharging the mixture from an orifice onto the rotating mandrel.
5. The method of claim 4 , wherein the PEO is dissolved in water to form a mixture before the PEO and water mixture is mixed with the PTFE dispersion.
6. The method of claim 1 , wherein at least one of the first and second tubes of PTFE have an average pore size between about 2 microns and about 8 microns.
7. The method of claim 1 , wherein at least one of the first and second tubes of PTFE have an average pore size between about 3 microns and about 5 microns.
8. The method of claim 1 , wherein at least one of the first and second tubes of PTFE have an average pore size of about 1.5 microns or less.
9. The method of claim 1 , further comprising coupling a cuff adjacent an end of the stent, wherein the cuff is configured to promote rapid cellular ingrowth into the cuff.
10. The method of claim 1 , wherein the FEP layer is substantially impermeable to tissue ingrowth.
11. The method of claim 1 , wherein at least one of the first and second tubes of PTFE is configured to permit tissue growth.
12. The method of claim 1 , wherein all the PTFE in the stent comprises electrospun PTFE.
13. A method of constructing a stent covering, the method comprising:
electrospinning a first tube of PTFE onto a rotating mandrel;
heating the first tube to between 360° C. to 400° C.;
applying a tie layer around the first tube after the first tube has been heated;
applying a second tube of PTFE around the tie layer;
applying a compressive wrap around the second tube; and
heat-treating the stent covering above the melting temperature of the tie layer but below the 325° C. while the compressive wrap is disposed around the second tube;
wherein the first tube of PTFE is an innermost tube of the stent that is configured for contact with bodily fluid.
14. The method of claim 13 , wherein the tie layer comprises fluorinated ethylene propylene (FEP).
15. The method of claim 14 , wherein the second tube of PTFE is formed by a method comprising:
electrospinning the second tube of PTFE onto a rotating mandrel; and
sintering the second tube.
16. The method of claim 13 , wherein electrospinning the first tube of PTFE comprises:
mixing a PTFE dispersion with PEO, wherein the PEO is dissolved in water to form a mixture before the PEO and water mixture is mixed with the PTFE dispersion; and
discharging the mixture from an orifice onto the rotating mandrel.