Drug-releasing stent with ceramic-containing layer

Abstract

A vascular or endoluminal stent is adapted to be implanted in a vessel, duct or tract of a human body to maintain an open lumen. The stent includes a base layer of a biologically compatible metal. An intermediate metal particle layer of substantial greater radiopacity overlies the base layer, with particles bonded to the base layer and to each other to leave interstices therebetween as a repository for retaining and dispensing drugs or other agents for time release therefrom. The particles are composed primarily of a noble metal—. Exposed surfaces of the particle layer are coated with ceramic-like iridium oxide or titanium nitrate, as a biocompatible material to inhibit irritation of tissue at the inner lining of the vessel when the stent is implanted.

What is claimed is: 
     
         1 . A vascular or endoluminal stent adapted to be implanted in a selected vessel, duct or tract of a human body to maintain an open lumen at the site of the implant, comprising an open-ended tubular structure having a base layer of metal that is biologically compatible with the blood and tissue of the human body, and a metal particulate layer of substantially greater radiopacity than the base layer overlying and composed of particles bonded to the base layer and to each other with interstices therebetween for retention of drugs to be time released therefrom after the stent is implanted, to assist the stent in maintaining said lumen open. 
     
     
         2 . The stent of  claim 1 , wherein the particles comprise a noble metal. 
     
     
         3 . The stent of  claim 2 , wherein the noble metal comprises an alloy including platinum and iridium. 
     
     
         4 . The stent of  claim 1 , wherein the particulate layer has a thickness in a range from about 4 to about 8 μm. 
     
     
         5 . The stent of  claim 1 , wherein the particles are of substantially spherical shape with larger particle spheres bonded to the at least one surface and progressively smaller spheres are present from and bonded to the larger particle spheres and to each other up to the surface of the metal particulate layer. 
     
     
         6 . The stent of  claim 1 , wherein the particles range in diameter from about 50 to about 500 nanometers, and the metal particulate layer is in a range of thickness from about 4 to about 8 μm. 
     
     
         7 . The stent of  claim 1 , wherein at least one drug selected from a group consisting of anti-thrombotic, anti-platelet, anti-inflammatory and anti-proliferative drugs is present in said interstices. 
     
     
         8 . The stent of  claim 7 , wherein said at least one drug is incorporated in a biodegradable material for time release of the drug. 
     
     
         9 . The stent of  claim 1 , wherein exposed surfaces of the metal particulate layer are coated with a ceramic-like material to inhibit irritation to tissue at the inner lining of said vessel, duct or tract when the stent is implanted therein in contact with said inner lining. 
     
     
         10 . The stent of  claim 9 , wherein said ceramic-like material is selected from a group consisting of iridium oxide or titanium nitrate. 
     
     
         11 . The stent of  claim 9 , wherein the ceramic like material is coated to a thickness in a range from approximately 50 to 500 nanometers. 
     
     
         12 . The stent of  claim 9 , wherein the ceramic-like material coating is of insufficient thickness to fill or substantially block said interstices, and at least one drug selected from a group consisting of anti-thrombotic, anti-platelet, anti-inflammatory and anti-proliferative drugs is present in said interstices. 
     
     
         13 . The stent of  claim 1 , wherein the particles of the metal particulate layer are bonded together in a pattern such that the interstices therebetween produce a timed release of a drug present therein when the stent is implanted. 
     
     
         14 . A method of fabricating a multi-layer vascular or endoluminal stent for deployment in a human body to hold a natural duct or tract thereof open for passage of fluids or solids therethrough, comprising steps of applying a porous layer of substantially spherical metal particles atop surfaces of a base metal of the stent, said metal particles at the base metal surfaces being bonded thereto and said metal particles throughout the porous layer being bonded together with voids therebetween forming a reservoir for retention and dispensing of drugs from the stent when deployed, said metal particles having a radiopacity that substantially exceeds that of the base metal for high visibility viewing of the stent by fluoroscopy when deployed in the body, and coating exposed surfaces of the metal particles with a ceramic-like material while leaving said voids therebetween substantially intact and unblocked so that said reservoir remains available for infusing drugs therein. 
     
     
         15 . The method of  claim 14 , wherein the base metal is from a group including stainless steel, chromium, nickel, titanium, iridium, and nickel-titanium alloy, wherein the metal particles are composed of platinum-iridium alloy with diameters ranging from about 50 to 500 nanometers, and the porous layer is applied to a thickness in a range from approximately 4 to 8 microns atop surfaces of the base metal, and wherein the ceramic-like material is selected from a group consisting of iridium oxide and titanium nitrate, and is coated on surfaces of the metal particles to a thickness in a range from approximately 50 to 500 nanometers. 
     
     
         16 . The method of  claim 15 , further including the step of infusing in said reservoir at least one drug selected from a group including anti-thrombotic, anti-platelet, anti-inflammatory and anti-proliferative drugs. 
     
     
         17 . The method of  claim 16 , further including infusing a biodegradable carrier for said at least one drug in said reservoir, for timed release of the drug therefrom. 
     
     
         18 . A vascular or endoluminal stent adapted to be implanted in a selected vessel, duct or tract of a human body to maintain an open lumen at the site of the implant, comprising an open-ended tubular structure having a base layer of metal constituting a sidewall which is biologically compatible with the fluids and tissue of the human body, an intermediate layer of substantially greater radiopacity than the base layer overlying and bonded to the base layer, and a ceramic-like material coating on and adherent to exposed surfaces of the intermediate layer to inhibit irritation to tissue at the inner lining of said vessel, duct or tract when the stent is implanted therein in contact with said inner lining. 
     
     
         19 . The stent of  claim 18 , wherein the intermediate layer comprises a noble metal. 
     
     
         20 . The stent of  claim 18 , wherein said ceramic-like material is selected from a group consisting of iridium oxide or titanium nitrate.