Hybrid stent and method of making

Abstract

A stent is formed by encasing or encapsulating metallic rings in an inner polymeric layer and an outer polymeric layer. At least one polymer link connects adjacent metallic rings. The stent is drug loaded with one or more therapeutic agent or drug, for example, to reduce the likelihood of the development of restenosis in the coronary arteries. The inner and outer polymeric materials can be of the same polymer or different polymer to achieve different results, such as enhancing flexibility and providing a stent that is visible under MRI, computer tomography and x-ray fluoroscopy.

What is claimed: 
     
         1 . A stent, comprising:
 a plurality of metallic rings aligned along a stent longitudinal axis;   an outer layer of a first polymeric material covering an outer surface of the metallic rings;   an inner layer of a second polymeric material covering an inner surface of the metallic rings; and   at least one link connecting adjacent metallic rings, the links being formed by the outer layer and the inner layer.   
     
     
         2 . The stent of  claim 1 , wherein the first polymeric material is EVOH. 
     
     
         3 . The stent of  claim 1 , wherein the second polymeric material is PEEK. 
     
     
         4 . The stent of  claim 3 , wherein the PEEK is radiopaque. 
     
     
         5 . The stent of  claim 2 , wherein the EVOH is radiopaque. 
     
     
         6 . The stent of  claim 1 , wherein the first and second polymeric materials are taken from the group of polymers consisting of polyetheretherketone (PEEK), ethyl vinyl alcohol (EVOH), polyetherketone, polymethylmethacrylate, polycarbonate, polyphenylenesulfide, polyphenylene, polyvinylfluoride, polyvinylidene fluoride, polypropylene, polyethylene, poly(vinylidene fluoride-co-hexafluoropropylene), poly(ethylene-co-hexafluoropropylene), poly(tetrafluoroethyelene-co-hexafluoropropylene), poly(tetrafluoroethyelene-co-ethylene), polyethyleneterephthalate, polyimides, polyetherimide, ePTFE, polyurethanes, polyetherurethanes, polyesterurethanes, silicone, thermoplastic elastomer, polyether-amide thermoplastic elastomer, fluoroelastomers, fluorosilicone elastomer, styrene-butadiene-styrene rubber, styrene-isoprene-styrene rubber, polybutadiene, polyisoprene, neoprene, ethylene-propylene elastomer, chlorosulfonated polyethylene elastomer, butyl rubber, polysulfide elastomer, polyacrylate elastomer, nitrile rubber, a family of elastomers composed of styrene, ethylene, propylene, aliphatic polycarbonate polyurethane, polymers augmented with antioxidants, polymers augmented with image enhancing materials, polymers having a proton (H+) core, butadiene and isoprene and polyester thermoplastic elastomer and a di-block co-polymer of PET and caprolactone. 
     
     
         7 . The stent of  claim 1 , wherein the metallic rings are formed of a metal alloy taken from the group of metal alloys consisting of stainless steel, titanium, tantalum, nickel-titanium, cobalt-chromium, and tungsten. 
     
     
         8 . The stent of  claim 1 , wherein one or both of the first and second polymeric materials are loaded with a therapeutic drug. 
     
     
         9 . The stent of  claim 8 , wherein the therapeutic drug is taken from the group of drugs including one or more of everolimus, rapamycin, actinomycin D (ActD), or derivatives and analogs thereof; synonyms of actinopmycin D including dactinomycin, actinomycin IV, actinomycin l1, actinomycin X1, and actinomycin C1; antiproliferative substances including antineoplastic, antinflammatory, antiplatelet, anticoagulant, antifibrin, antithomobin, antimitotic, antibiotic, antioxidant substances, taxol (paclitaxel and docetaxel), anticoagulants, antifibrins, sodium heparin, low molecular weight heparin, hirudin, argatroban, forskolin, vapiprost, prostacyclin and prostacyclin analogs, dextran, D-phe-pro-arg-chloromethylketone (synthetic antithrombin), dipyridamole, glycoprotein, llb/llla platelet membrane receptor antagonist, recombinant hirudin, thrombin inhibitor methotrexate, azathioprine, vincristine, vinblastine, fluorouracil, adriamycin, mutamycin; angiopeptin, angiotensin converting enzyme inhibitors; calcium channel blockers; colchicine fibroblast growth factor (FGF) antagonists; fish oil (omega 3-fatty acid); histamine antagonist; monoclonal antibodies (such as PDGF receptors); nitroprusside; phosphodiesterase inhibitors; prostaglandin inhibitor (a PDGF antagonist); serotonin blockers; steroids; thioprotease inhibitors; triazolopyrimidine (a PDGF antagonist); and nitric oxide. 
     
     
         10 . The stent of  claim 1 , wherein a radiopaque marker is positioned between the first polymeric material and the second polymeric material. 
     
     
         11 . The stent of  claim 1 , wherein the outer layer of the first polymeric material has a thickness in the range of 0.001 mm to 2.5 mm. 
     
     
         12 . The stent of  claim 11 , wherein the outer layer has a uniform thickness. 
     
     
         13 . The stent of  claim 11 , wherein the outer layer has a variable thickness. 
     
     
         14 . The stent of  claim 1 , wherein the inner layer of the second polymeric material has a thickness in the range of 0.001 mm to 2.5 mm. 
     
     
         15 . The stent of  claim 14 , wherein the inner layer has a uniform thickness. 
     
     
         16 . The stent of  claim 14 , wherein the inner layer has a variable thickness. 
     
     
         17 . The stent of  claim 1 , wherein the metallic rings have an undulating pattern. 
     
     
         18 . The stent of  claim 17 , wherein the undulating pattern includes U-shaped elements. 
     
     
         19 . The stent of  claim 1 , wherein the stent is configured so that it is visible under any of x-ray fluoroscopy, computer tomography, or MRI. 
     
     
         20 . The stent of  claim 1 , wherein a cavity is formed between the first polymeric material and the second polymeric material so that a therapeutic drug can be releasably contained within the cavity. 
     
     
         21 . The stent of  claim 1 , wherein the metallic rings are formed of struts, the struts having a substantially uniform radial thickness. 
     
     
         22 . The stent of  claim 1 , wherein the metallic rings are formed of struts, the struts having a variable radial thickness. 
     
     
         23 . The stent of  claim 1 , wherein the first polymeric material is a shape memory polymer. 
     
     
         24 . The stent of  claim 23 , wherein the shape memory polymer includes the family of polymers oligo (e-caprolactone) dimethacrylate combined with n-butyl acrylate. 
     
     
         25 . A method of making a hybrid stent, comprising:
 laser cutting a tubular member to form a pattern of metallic rings;   mounting a first polymeric tube onto mandrel and positioning the metallic rings over the polymeric tube;   mounting a second polymeric tube over the metallic rings and the first polymeric tube;   fusing the first polymeric tube to the second polymeric tube with the metallic rings therebetween; and   removing the fused first polymeric tube and the second polymeric tube from the mandrel.   
     
     
         26 . The method of  claim 25 , wherein prior to fusing the polymeric tubes, positioning a shrink tubing over the second polymeric tubing and applying heat to the shrink tubing so that the shrink tubing tightly compresses onto the second polymeric tube, the heat being sufficient to fuse at least a portion of the first polymeric tube to the second polymeric tube. 
     
     
         27 . The method of  claim 26 , wherein the heat is provided by a laser. 
     
     
         28 . The method of  claim 25 , wherein an adhesive is applied to an outer surface of the first polymeric tube prior to mounting the second polymeric tube to assist in fusing the tubes together. 
     
     
         29 . The method of  claim 28 , wherein the adhesive is heat activated. 
     
     
         30 . The method of  claim 25 , wherein after the stent is removed from the mandrel, forming a pattern by removing portions of the fused first and second polymeric tubes. 
     
     
         31 . The method of  claim 30 , wherein the portions of the fused first and second polymeric tubes are removed by laser ablation. 
     
     
         32 . The method of  claim 31 , wherein links for connecting the metallic rings are formed by laser ablation of the fused first and second polymeric tubes. 
     
     
         33 . The method of  claim 25 , wherein a therapeutic drug is loaded into either or both of the first and second polymeric tubes. 
     
     
         34 . The method of  claim 32 , wherein the first and second polymeric tubes are drug loaded after laser ablation. 
     
     
         35 . A method of making a hybrid stent, comprising:
 coating a mandrel with a first polymer to form a first polymeric tube;   mounting a plurality of metallic rings over the first polymeric tube;   applying a second polymeric material over the metallic rings and the first polymeric tube to form the stent; and   removing the stent from the mandrel.   
     
     
         36 . The method of  claim 35 , wherein the first polymeric tube is formed by dip-coating the mandrel in a first polymeric material. 
     
     
         37 . The method of  claim 35 , wherein the second polymeric material is applied to the rings and the first polymeric tube by dip-coating. 
     
     
         38 . The method of  claim 35 , wherein the second polymeric material is sprayed onto the metallic rings and the first polymeric tube. 
     
     
         39 . The method of  claim 35 , wherein portions of the first and second polymeric materials are removed by laser ablation. 
     
     
         40 . The method of  claim 39 , wherein links for connecting the metallic rings are formed by laser ablation of the first and second polymeric materials. 
     
     
         41 . The method of  claim 35 , wherein a therapeutic drug is loaded into either or both of the first and second polymeric materials.