Stent Coating For Eluting Medication

• US 20060200231A1
• Filed: 01/27/2006
• Published: 09/07/2006
• Est. Priority Date: 01/28/2005
• Status: Active Grant

• Current Assignee: Greatbatch Limited (Greatbatch Incorporated)
• Original Assignee: Greatbatch Incorporated
• Inventors: O'Brien, Robert C., Frysz, Christine A.
• Granted Patent: US 8,057,543 B2
• Time in Patent Office: Days
• US Class Current: 623/1.420
• CPC Class Codes: A61F 2/91 made from perforated sheet material or tubes, e.g. perforated by laser cuts or etched holes
• CPC Class Codes: A61F 2250/0067 Means for introducing or releasing pharmaceutical products into the body
• CPC Class Codes: A61F 2250/0068 the pharmaceutical product being in a reservoir
• CPC Class Codes: A61L 2300/108 Elemental carbon, e.g. charcoal
• CPC Class Codes: A61L 31/084 Carbon; Graphite
• CPC Class Codes: A61L 31/146 Porous materials, e.g. foams or sponges
• CPC Class Codes: A61L 31/16 Biologically active materials, e.g. therapeutic substances A61L31/047 takes precedence
• CPC Class Codes: Y10T 29/49885 with coating before or during assembling

Abstract

A vascular stent comprising a drug-eluting outer layer of a porous sputtered columnar metal having each column capped with a biocompatible carbon-containing material is described. This is done by placing the stent over a close-fitting mandrel and rotating the assembly in a sputter flux. The result is a coating that is evenly distributed over the outward-facing side of the stent'"'"'s wire mesh while preventing the sputtered columnar coating from reaching the inward facing side where a smooth hemocompatible surface is required. The stent is then removed from the mandrel, exposing all surfaces, and finally coated with a layer of carbon such as amorphous carbon or diamond-like carbon. The carbonaceous coating enhances biocompatibility without preventing elutriation of a therapeutic drug provided in the porosity formed between the columnar structures. The result is a stent that is adapted to both the hemodynamic and the immune response requirements of its vascular environment.

Claims

1. A biocompatible coating for contact with body tissue, the coating comprising:

a) a substrate;

b) an intermediate coating adhered to the substrate and comprising a plurality of columnar structures having a sidewall extending between a proximal end adhered to the substrate and a distal end spaced therefrom, wherein the sidewalls of immediately adjacent columns do not contact each other to thereby provide porosity there between;

c) a cap of a carbon-containing material provided on the distal end of each of the plurality of columnar structures; and

d) wherein the porosity provided between each of the plurality of columnar structures is adapted for receiving an elutable material therein.

2. The biocompatible coating of claim 1 wherein the intermediate coating is selected from the group consisting of carbides, oxides, nitrides, oxynitrides, and carbonitrides of titanium, boron, aluminum, calcium, gold, hafnium, iridium, molybdenum, niobium, platinum, rhenium, ruthenium, silicon, silver, tantalum, titanium, tungsten, yttrium, zirconium.

3. The biocompatible coating of claim 1 wherein the carbon-containing coating is selected from an amorphous carbon and a diamond-like carbon.

4. The biocompatible coating of claim 1 wherein the intermediate coating is adhered to the substrate and the carbon-containing coating is provided as the cap on the distal end of each of the plurality of columnar structures by one of the deposition techniques selected from the group consisting of sputtering, chemical vapor deposition, pulsed laser deposition, reactive evaporation, and as a thermal spray.

5. The biocompatible coating of claim 1 wherein the plurality of columnar structures comprising the intermediate coating each have a length of about 0.1 μ

m to about 20 μ

m.

6. The biocompatible coating of claim 1 wherein the carbon-containing coating has a thickness of about 0.05 μ

m to about 2.0 μ

m.

7. A stent for insertion and expansion in a vasculature to support its adjacent vasculature region, the stent comprising:

a) a plurality of wires forming an elongated and selectively expandable and constrictable hollow tube, each wire providing a substrate having a cross-section comprising an outside-facing surface portion and an inside-facing surface portion facing a lumen formed by the hollow tube;

b) an intermediate coating adhered to the outside-facing surface portion of each substrate wire and comprising a plurality of columnar structures having a sidewall extending between a proximal end adhered to the substrate and a distal end spaced therefrom, wherein the sidewalls of immediately adjacent columns do not contact each other to thereby provide porosity there between;

c) a cap of a carbon-containing material provided on the distal end of each of the plurality of columnar structures; and

d) wherein the porosity provided between each of the plurality of columnar structures is adapted for receiving an elutable material therein.

8. The stent of claim 7 wherein the carbon-containing material provides a thin film on the inside-facing surface portion of the wire substrate.

9. The stent of claim 7 wherein the intermediate coating is selected from the group consisting of carbides, oxides, nitrides, oxynitrides, and carbonitrides of titanium, boron, aluminum, calcium, gold, hafnium, iridium, molybdenum, niobium, platinum, rhenium, ruthenium, silicon, silver, tantalum, titanium, tungsten, yttrium, zirconium.

10. The stent of claim 7 wherein the carbon-containing coating is selected from an amorphous carbon and a diamond-like carbon.

11. The stent of claim 7 wherein the intermediate coating is adhered to the substrate and the carbon-containing coating is provided as the cap on the distal end of each of the plurality of columnar structures by one of the deposition techniques selected from the group consisting of sputtering, chemical vapor deposition, pulsed laser deposition, reactive evaporation, and as a thermal spray.

12. The stent of claim 7 wherein the plurality of columnar structures comprising the intermediate coating each have a length of about 0.1 μ

m to about 20 μ

m.

13. The stent of claim 7 wherein the carbon-containing coating has a thickness of about 0.05 μ

m to about 2.0 μ

m.

14. A method for providing a stent suitable for insertion and expansion into a vasculature to support an adjacent vasculature region, comprising the steps of:

a) providing a plurality of wires forming an elongated and selectively expandable and constrictable hollow tube, each wire providing a substrate having a cross-section comprising an outside-facing surface portion and an inside-facing surface portion;

b) adhering an intermediate coating to the outside-facing surface portion of each substrate wire, the intermediate coating comprising a plurality of columnar structures having a sidewall extending between a proximal end adhered to the substrate wire and a distal end spaced therefrom, wherein the sidewalls of immediately adjacent columns do not contact each other to thereby provide porosity there between;

c) capping the distal end of each of the plurality of columnar structures with a carbon-containing material; and

d) filling an elutable material into the porosity provided between each of the plurality of columnar structures.

15. The method of claim 14 including expanding the stent to near an elastic stress limit of the plurality of wires prior to providing the intermediate coating thereon.

16. The method of claim 14 including providing the stent comprising a nickel titanium shape memory alloy heated to near an elastic stress limit of the plurality of wires prior to providing the intermediate coating thereon.

17. The method of claim 16 including heating the nickel titanium shape memory alloy to near its elastic stress limit in a sputter chamber.

18. The method of claim 14 including providing the an elutable material as a medication filled into the porosity between the columnar structures and comprising a polymer selected from the group consisting of polyurethane, silicone, polyesters, polycarbonate, polyethylene, polyvinyl chloride, polypropylene methylacrylate, para-xylylene, and mixtures thereof.

19. The method of claim 14 including providing a polymeric material covering the carbonaceous caps.

20. The method of claim 14 including adhering the intermediate coating to the substrate and capping the distal end of each of the plurality of columnar structures with the carbon-containing coating by one of the deposition techniques selected from the group consisting of sputtering, chemical vapor deposition, pulsed laser deposition, reactive evaporation, and as a thermal spray.

21. A method for providing a stent suitable for insertion and expansion into a vasculature to support an adjacent vasculature region, comprising the steps of:

a) providing a plurality of wires comprising a shape memory alloy forming an elongated and selectively expandable and constrictable hollow tube, each wire providing a substrate having a cross-section comprising an outside-facing surface portion and an inside-facing surface portion;

b) heating the shape memory alloy to near its elastic stress limit;

c) adhering an intermediate coating on the outside-facing surface portion of each substrate wire, the intermediate coating comprising a plurality of columnar structures having a sidewall extending between a proximal end adhered to the substrate wire and a distal end spaced therefrom, wherein the sidewalls of immediately adjacent columns do not contact each other to thereby provide porosity there between;

d) capping the distal end of each of the plurality of columnar structures with a carbon-containing material formed thereon; and

e) filling an elutable material into the porosity provided between each of the plurality of columnar structures.

22. The method of claim 21 including providing the stent comprising a nickel titanium shaped memory alloy.