Endovascular graft coatings

Abstract

An endovascular graft, e.g., having both an expandable stent portion and a stent cover portion positioned within and/or surrounding the expandable portion, the graft itself and/or a stent cover portion being coated with a bioactive agent adapted to promote initial thrombus formation, preferably followed by long term fibrous tissue ingrowth. The endovascular graft addresses concerns regarding endoleaking by permitting the graft to be deployed and used in a manner that promotes a short term hemostatic effect in the perigraft region. This short term effect can, in turn, be used to promote or permit long term fibrous tissue ingrowth. Particularly where the stent cover portion is prepared from a porous material selected from PET and ePTFE, the bioactive agent can include a thrombogenic agent such as collagen covalently attached in the form of a thin, conformal coating on at least the outer surface of the stent cover. An optimal coating of this type is formed by the activation of photoreactive groups provided by either the cover material itself, by the bioactive agent itself, and/or by a linking agent.

1 . An expandable stent having an inner surface and an outer surface, wherein at least one surface of the stent is coated with a hemostatic bioactive agent, wherein the bioactive agent comprises collagen type I or an active domain or portion thereof covalently attached to the stent surface by the activation of photoreactive groups provided by the stent surface, the bioactive agent, and/or by a linking agent.  
   
   
       2 . A stent according to claim  27  wherein the bioactive agent is immobilized in a range of about 0.01 μg/cm 2  to about 50 μg/cm 2 .  
   
   
       3 . A stent according to claim  28  wherein the bioactive agent is immobilized in a range of about 0.01 μg/cm to about 10 μg/cm 2 .  
   
   
       4 . A stent according to claim  27  wherein the bioactive agent is immobilized in a manner that promotes the growth of endothelial cells on the inner surface of the stent.  
   
   
       5 . A stent according to claim  27  wherein the photoreactive group is provided on the bioactive agent itself.  
   
   
       6 . A stent according to claim  27  wherein the photoreactive group is provided on the stent surface.  
   
   
       7 . A stent according to claim  27  wherein the stent is comprised of a shape memory alloy.  
   
   
       8 . A stent according to claim  27  wherein the coating is provided on at least the inner surface of the stent.  
   
   
       9 . A stent according to claim  27  wherein the coating is provided on at least the outer surface of the stent.  
   
   
       10 . A method of preparing a stent comprising the step of coating at least the outer surface of the stent with collagen type I or an active domain or portion thereof that is covalently attached by the activation of photoreactive groups provided by the stent surface, the hemostatic agent itself, and/or by a linking agent.  
   
   
       11 . The method of claim  36  wherein the coating is in the form of a thin conformal coating.  
   
   
       12 . The method of claim  36  wherein the coating does not add more than 25% to the original thickness of the stent.  
   
   
       13 . The method of claim  36  wherein the collagen type I is immobilized in a range of about 0.01 μg/cm2 to about 50 μg/cm 2 .  
   
   
       14 . The method of claim  39  wherein the collagen type I is immobilized in a range of about 0.01 μg/cm 2  to about 10 μg/cm 2 .  
   
   
       15 . The method of claim  36  wherein the photoreactive group is provided on the bioactive agent itself.  
   
   
       16 . An expandable stent comprising an inner and an outer surface wherein at least one surface is coated with a hemostatic bioactive agent covalently attached to the at least one surface via activation of photoreactive groups provided on the hemostatic bioactive agent.  
   
   
       17 . The stent of claim  42  wherein the hemostatic bioactive agent comprises type I collagen.  
   
   
       18 . The stent of claim  43  wherein the type I collagen is immobilized in a range of about 0.01 μg/cm2 to about 50 μg/cm 2 .  
   
   
       19 . The stent of claim  42  wherein at least the inner surface is coated with the hemostatic agent.  
   
   
       20 . The stent of claim  42  wherein at least the outer surface is coated with the hemostatic agent.