Electrospun material covered medical appliances and methods of manufacture

Abstract

A medical appliance or prosthesis may comprise one or more layers of electrospun nanofibers, including electrospun polymers. The electrospun material may comprise layers including layers of polytetrafluoroethylene (PTFE). Electrospun nanofiber mats of certain porosities may permit tissue ingrowth into or attachment to the prosthesis.

1 . A covered stent, comprising:
 a frame comprising a midbody and a flare zone; and   a cover coupled to the frame,   wherein the cover comprises an electrospun polytetrafluoroethylene (PTFE) material, and   wherein the frame and the cover are configured to promote biocompatibility of the stent.   
     
     
         2 . The stent of  claim 1 ,
 wherein the midbody comprises a first apex to apex length,   wherein the flare zone comprises a second apex to apex length,   wherein the first apex to apex length is less than the second apex to apex length, and   wherein a resistance to radial compression of the midbody is greater than a resistance to radial compression of the flare zone.   
     
     
         3 . The stent of  claim 2 , wherein the flare zone is configured to engage with healthy tissue of a blood vessel and minimize trauma to the healthy tissue. 
     
     
         4 . The stent of  claim 2 ,
 wherein the first apex to apex length ranges from 2.0 mm to 30.0 mm, and   wherein the second apex to apex length ranges from 2.1 mm to 30.1 mm.   
     
     
         5 . The stent of  claim 1 ,
 wherein an end of the flare zone comprises an alternating pattern of long apexes and short apexes about a perimeter of the frame,   wherein the alternating pattern is configured to distribute an outwardly directed force along a length of a vessel wall, and   wherein the end of the flare zone is configured to be a-traumatic to healthy tissue of the vessel wall.   
     
     
         6 . The stent of  claim 1 ,
 wherein the cover includes a scallop shaped end,   wherein the scallop shaped end is configured to reduce infolding of tissue of a vessel wall when an outside diameter of the stent is greater than an inside diameter of a vessel.   
     
     
         7 . A covered stent, comprising:
 a frame; and   a cover coupled to the frame,   wherein the cover comprises an electrospun PTFE material, and   wherein an inner layer and an outer layer of the cover are each configured to be cell permeable.   
     
     
         8 . The covered stent of  claim 7 ,
 wherein the inner layer is configured to promote attachment of a coating of epithelial cells,   wherein the coating is configured to prevent thrombosis within a lumen of the stent, and   wherein the outer layer is configured to permit healing of tissue adjacent the stent.   
     
     
         9 . The covered stent of  claim 7 , wherein a porosity of the inner layer and a porosity of the outer layer each range from 30% to 80%. 
     
     
         10 . The covered stent of  claim 7 , wherein an average pore size of the inner layer and an average pore size of the outer layer each range from 1 micron to 12 microns. 
     
     
         11 . The covered stent of  claim 7 , wherein a thickness of the inner layer and a thickness of the outer layer each range from 20 micrometers to 100 micrometers. 
     
     
         12 . The covered stent of  claim 7 ,
 wherein the inner layer and the outer layer comprise a plurality of fibers, and   wherein an average diameter of the plurality of fibers ranges from 50 nanometers to 3 micrometers.   
     
     
         13 . The covered stent of  claim 7 , wherein the inner layer and the outer layer are each configured to allow an average cell penetration depth of greater than 98% of a thickness of the layer. 
     
     
         14 . The covered stent of  claim 7 , wherein the inner layer and the outer layer are configured to produce an average fibrous capsule thickness of less than 35 micrometers. 
     
     
         15 . The covered stent of  claim 7 , wherein the cover is configured to filter blood, wherein the inner layer and the outer layer are configured to permit transmural migration of blood plasma and to prevent transmural migration of red blood cells. 
     
     
         16 . The covered stent of  claim 15 ,
 wherein a middle layer is configured to prevent transmural migration of cells, and   wherein the middle layer is configured to prevent restenosis of a vessel.   
     
     
         17 . The stent of  claim 16 , wherein the middle layer is configured to prevent transmural fluid migration, and wherein the middle layer is configured to contain a fluid within the stent. 
     
     
         18 . A method of promoting biocompatibility of a stent, comprising:
 promoting endothelial cell growth on a luminal surface of the stent;   reducing a tissue inflammatory response to the stent; or   resisting fibrous capsule formation adjacent the stent;   wherein the stent comprises a cover comprising an electrospun PTFE material, the cover comprising:
 a porosity ranging from 30% to 80%; 
 an average pore size ranging from 1 micron to 12 microns; 
 a thickness ranging from 20 micrometers to 100 micrometers; and 
 a plurality of fibers having an average diameter ranging from 50 nanometers to 3 micrometers. 
   
     
     
         19 . The method of  claim 18 , wherein promoting endothelial cell growth comprises reducing turbulent flow within the stent. 
     
     
         20 . The method of  claim 18 , wherein reducing an inflammatory response comprises reducing macrophage and foreign body giant cell counts adjacent the stent. 
     
     
         21 . The method of  claim 20 , wherein reducing macrophage and foreign body giant cell counts is configured to comprises an H-score of less than 100. 
     
     
         22 . The method of  claim 18 , wherein resisting fibrous capsule formation comprises a fibrous capsule having a thickness of any one of less than 35 micrometers, less than 30 micrometers, less than 25 micrometers, less than 20 micrometers, and less than 15 micrometers.