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Coatings for medical devices comprising a therapeutic agent and a metallic material

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Coatings for medical devices comprising a therapeutic agent and a metallic material


The invention relates generally to an implantable medical device for delivering a therapeutic agent to the body tissue of a patient, and a method for making such a medical device. In particular, the invention pertains to an implantable medical device, such as an intravascular stent, having a coating comprising a first coating composition comprising a therapeutic agent and, optionally, a polymer; and a second coating composition comprising a metallic material.

Browse recent Boston Scientific Scimed, Inc. patents - Maple Grove, MN, US
Inventor: Pu Zhou
USPTO Applicaton #: #20120323308 - Class: 623 116 (USPTO) - 12/20/12 - Class 623 
Prosthesis (i.e., Artificial Body Members), Parts Thereof, Or Aids And Accessories Therefor > Arterial Prosthesis (i.e., Blood Vessel) >Stent Structure >Having Multiple Connected Bodies

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The Patent Description & Claims data below is from USPTO Patent Application 20120323308, Coatings for medical devices comprising a therapeutic agent and a metallic material.

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FIELD OF THE INVENTION

The invention relates generally to implantable medical devices for delivering a therapeutic agent to the body tissue of a patient, and methods for making such medical devices. In particular, the invention pertains to implantable medical devices, such as intravascular stents, having a coating comprising a first coating composition comprising a therapeutic agent and a second coating composition comprising a metallic material.

BACKGROUND OF THE INVENTION

Medical devices have been used to deliver therapeutic agents locally to the body tissue of a patient. For example, intravascular stents comprising a therapeutic agent have been used to locally deliver therapeutic agents to a blood vessel. Often such therapeutic agents have been used to prevent restenosis. Examples of stents comprising a therapeutic agent include stents that comprise a coating containing a therapeutic agent for delivery to a blood vessel. Studies have shown that stents having a coating with a therapeutic agent are effective in treating or preventing restenosis.

Even though medical devices having a coating with a therapeutic agent are effective in preventing restenosis, many coated medical devices, in addition to being coated with a therapeutic agent, are also coated with a polymer. The benefits of using a polymer in such coatings include easier loading of therapeutic agents onto the surface of a medical device and the ability to control or regulate the rate of release of the therapeutic agent.

However, the use of polymers in medical device coatings can also have some disadvantages. For example, depending on the type of polymer used to coat the medical device, some polymers can cause inflammation of the body lumen, offsetting the effects of the therapeutic agent. Additionally, some polymers may also cause thrombosis.

Accordingly, there is a need for coatings for a medical device that prevent or at least reduce the disadvantages associated with polymer coatings, such as inflammation caused by contact with the body lumen. Moreover, there is a need for a coating for medical devices that can control or regulate the release rate of a therapeutic agent without the use of polymer coatings. There is also a need for methods of making such medical devices.

SUMMARY

OF THE INVENTION

These and other objectives are accomplished by the present invention. The present invention provides a medical device, such as an implantable, intravascular stent comprising a coating. The coating is designed to eliminate or at least reduce the amount of polymer contact with the body tissue, such as a body lumen, while still providing a suitable release rate of the therapeutic agent. The coating comprises a first coating composition comprising a therapeutic agent and a second coating composition comprising a metallic material. Optionally, the first coating composition can further comprise a polymer.

The coating can comprise a first coating composition comprising a therapeutic agent, disposed on the surface of a medical device; and a second coating composition, which comprises a metallic material and which is substantially free of any polymer, disposed on at least a portion of the first coating composition. Metallic materials are materials containing a metal including but not limited to, metals alloys and oxides. As used herein and unless otherwise defined the phrase “substantially free of any polymer” means having less than or equal to 50% of polymer by volume of the composition. With such coatings, polymer contact with the body lumen is reduced or eliminated.

For example, the present invention is directed to an implantable intravascular stent comprising: (a) a stent sidewall structure having a surface; and (b) a coating comprising: (i) a first coating composition comprising a therapeutic agent disposed upon at least a portion of the surface of the stent sidewall structure, wherein the first coating composition, when disposed on the portion of the surface of the stent sidewall structure, has an outer surface; and (ii) a second coating composition comprising a metallic material disposed on at least a portion of the first coating composition, wherein the second coating composition is substantially free of any polymer when applied to the portion of the first coating composition; and wherein after the second coating composition is applied to the portion of the first coating composition the second coating composition comprises an outer surface and a plurality of pores, in which the pores extend from the outer surface of the first coating composition to the outer surface of the second coating composition. In certain embodiments of the present invention the second coating composition is disposed on less than the entire outer surface of the first coating composition. Additionally, the second coating composition can also be further disposed on a portion of the surface of the stent sidewall structure.

The stent sidewall structure can be an abluminal surface or an adluminal surface. In certain embodiments, the coating is disposed on at least a portion of the abluminal surface. In other embodiments, the first coating composition is disposed on at least a portion of the abluminal surface and the second coating composition is disposed on at least a portion of the first coating composition disposed on the adluminal surface. In still other embodiments, the first coating composition is disposed on at least a portion of the abluminal surface and the adluminal surface is free of the second coating composition.

Additionally, the stent sidewall structure can comprise a plurality of struts wherein the surface of the stent sidewall structure is the abluminal surface or adluminal surface of at least one of the struts. When the stent sidewall structure comprises a plurality of struts, the coating can be disposed on at least a portion of the abluminal or adluminal surface of at least one of the struts. For example, the present invention is directed to an implantable intravascular stent comprising: (a) a stent sidewall structure comprising a plurality of struts each having an abluminal surface and an adluminal surface (b) a first coating disposed on the abluminal surface of at least one strut comprising: (i) a first coating composition comprising as anti-restenosis agent disposed upon at least a portion of the abluminal surface of the strut, wherein the first coating composition, when disposed on the portion of the surface of the abluminal surface of the strut has an outer surface; and (ii) a second coating composition comprising a metallic material disposed on at least a portion of the first coating composition, wherein the second coating composition is substantially free of any polymer; and wherein after the second coating composition is applied to the portion of the first coating composition the second coating composition comprises an outer surface and a plurality of pores, in which the pores extend from the outer surface of the first coating composition to the outer surface of the second coating composition; and (c) a second coating disposed on at least a portion of the adluminal surface of the at least one strut comprising the first coating composition.

In certain embodiments, the first coating composition is disposed on at least a portion of the adluminal surface of at least one of the struts and at least a portion of the adluminal surface of at least one of the struts is free of the second coating composition. In other embodiments, the first coating composition is disposed on at least a portion of the adluminal surface of at least one of the struts and the second coating composition is disposed on at least a portion of the first coating composition that is disposed on the adluminal surface.

In certain embodiments, the stent sidewall structure can further comprise a plurality of openings therein. When the stent sidewall structure has a plurality of openings, the first and second coating compositions can conform to the stent sidewall structure to preserve the openings in the stent sidewall structure. For example the present invention includes an implantable intravascular stent comprising: (a) a stent sidewall structure comprising (1) a plurality of struts each having an abluminal surface and an adluminal surface, and (2) openings in the stent sidewall structure; (b) a first coating disposed on the abluminal surface of at least one strut comprising: (i) a first coating composition comprising an anti-restenosis agent disposed upon at least a portion of the abluminal surface of the strut, wherein the first coating composition, when disposed on the portion of the surface of the abluminal surface of the strut, has an outer surface; and (ii) a second coating composition comprising a metallic material disposed on at least a portion of the first coating composition, wherein the second coating composition is substantially free of any polymer; and wherein after the second coating composition is applied to the portion of the first coating composition, the second coating composition comprises an outer surface and a plurality of pores, in which the pores extend from the outer surface of the first coating composition to the outer surface of the second coating composition; and (c) a second coating disposed on at least a portion of the adluminal surface of the at least one strut comprising the first coating composition, wherein the adluminal surface of the at least one strut is free of the second coating composition; and wherein the first and second coatings conform to the stent sidewall structure to preserve the openings therein.

Also the present invention is directed to an implantable intravascular stent comprising: (a) a stent sidewall structure having a surface; and (b) a coating comprising (i) a first coating composition comprising a therapeutic agent disposed upon at least a portion of the surface of the stent sidewall structure wherein the first coating composition has a first thickness; and (ii) a second coating composition comprising a metallic material disposed upon at least a portion of the surface of the stent sidewall structure, wherein the second coating composition has a second thickness and is substantially free of any polymer; and wherein the first thickness of the first coating composition is not greater than the second thickness of the second coating composition. The first coating composition can also further comprise a polymer.

In certain embodiments, the second thickness of the second coating composition can be greater than the first thickness of the first coating composition. Alternatively, the first thickness of the first coating composition can be equal to the second thickness of the second coating composition. Moreover, the second coating composition can be disposed adjacent to the first coating composition on the surface of the stent side wall structure.

In any of the embodiments described above, the first thickness of the first coating composition can be about 1 micron to about 30 microns and the second thickness of the second coating composition can be about 0.1 microns to about 50 microns.

The therapeutic agent in the first coating composition can comprise an agent that inhibits smooth muscle cell proliferation. The therapeutic agent in the first coating composition can also comprise an anti-thrombogenic agent, anti-angiogenesis agent, anti-proliferative agent, antibiotic, anti-restenosis agent, growth factor, immunosuppressant or radiochemical. For example the therapeutic agent can comprise paclitaxel, sirolimus, tacrolimus, pimecrolimus, everolimus or zotarolimus.

Additionally, the first coating composition further comprises at least one polymer. Suitable polymers include, but are not limited to, styrene-isobutylene copolymers, polylactic acid and poly(methylmethacrylate-butyl acrylate-methyl methacrylate).

The metallic material of the second coating composition can be selected from the group consisting of stainless steel, nickel, titanium, chromium and alloys thereof.

BRIEF DESCRIPTION OF THE DRAWINGS

The present invention will be explained with reference to the following drawings.

FIG. 1 shows a cross-sectional view of an embodiment of a coating disposed on at least a portion of a medical device.

FIG. 2 shows a cross-sectional view of another embodiment of a coating disposed on at least a portion of a medical device.

FIG. 3 shows a portion of a medical device that is suitable for use in the present invention.

FIG. 4 shows a cross-sectional view of a stent.

FIG. 4a shows a cross-sectional view of a strut of a stent having a coating thereon.

FIG. 4b shows a cross-sectional view of another embodiment of a strut of a stent having a coating thereon.

FIG. 5 shows a perspective view of an embodiment of a coating disposed on at least a portion of a stent.

FIG. 6 shows a perspective view of another embodiment of a coating disposed on at least a portion of a stent.

FIG. 7 shows a perspective view of yet another embodiment of a coating disposed on at least a portion of a stent.

FIG. 8 shows a perspective view of yet another embodiment of a coating disposed on at least a portion of a stent.

FIG. 9 shows a cross-sectional view of another embodiment of a coating disposed on at least a portion of a medical device.

FIG. 10 shows a cross-sectional view of yet another embodiment of a coating disposed on at least a portion of a medical device.

FIG. 11 shows a cross-sectional view of yet another embodiment of a coating disposed on at least a portion of a medical device.

DETAILED DESCRIPTION

The present invention is directed to a medical device comprising a coating comprising a first coating composition containing a therapeutic agent and optionally a polymer. The medical device also includes a second coating composition containing a metallic material and is substantially free of any polymer.

In certain embodiments, the coating comprises a first coating composition comprising a therapeutic agent disposed on the surface of the medical device and a second coating composition comprising a metallic material disposed on the first coating composition. The second coating composition is substantially free of any polymer. Also, after the second coating composition is disposed on the first coating composition, wherein the second coating composition comprises a plurality of pores that extend from the outer surface of the first composition to the outer surface of the second coating composition.

FIG. 1 shows a cross-sectional view an embodiment of a coating disposed on at least a portion of a medical device such as a stent. In this embodiment, medical device 10 has a surface 12 and a coating 20. Coating 20 includes a first coating composition 22 comprising a therapeutic agent 30 disposed on at least a portion of the surface 12 of the medical device 10. When disposed on the surface 12, the first coating composition 22 has an outer surface 22a. The coating also includes a second coating composition 24 disposed on at least a portion of the first coating composition 22. The second coating composition 24 comprises a metallic material and is substantially free of any polymer. The second coating composition 24 can be disposed on a portion of or the entire first coating composition 22.

As shown in FIG. 1, the second coating composition 24 after being applied to the first coating composition 22 has an outer surface 24a and also has a plurality of pores 42. At least some of the pores 42 extend from the outer surface 22a of the first coating composition 22 to the outer surface 24a of the second coating composition 24. The pores 42 can be partially or completely filled with the first coating composition 22. In either case having the pores that extend from the outer surface 22a of the first coating composition 22 to the outer surface 24a of the second coating composition 24 allows the therapeutic agent 30 to be released from the first coating composition 22 underlying the second coating composition 24. Additionally, having pores 42 that allow for fluid communication between the outer surfaces 22a and 24a can aid in vascularization, provide long term non-inflammation and minimize or eliminate thrombosis. Furthermore, some or all of the pores 42 in the second coating composition 24 can be interconnected to other pores 42 within the second coating composition 24. In some embodiments, the pores 42 may be disposed in a desired pattern.

In addition, the pores 42 in the second coating composition 24 may have any shape. For example, the pores 42 can be shaped like channels, void pathways or microscopic conduits, spheres or hemispheres. Additionally, the pores 42 in the second coating composition 24 may have any size or range of sizes. In some instances, the pores 42 can be micropores or nanopores. Also, in some embodiments, it may be preferable that the width or diameter of the pores 42 is between about 1 nm and about 10 μm.

The size of the pores 42 can also be used to control the release rate of the therapeutic agent 30. For example, pores 42 having a larger width will allow the therapeutic agent 30 to be released more quickly than pores 42 with a smaller width. Also, the number of pores 42 in the second coating composition 24 can be adjusted to better control the release rate of the therapeutic agent 30. For example, the presence of more pores 42 per unit volume or weight of the second coating composition 24 can allow for a higher release rate of the therapeutic agent 30 than a material having fewer pores 42 therein.

In other embodiments, the coating comprises a first coating composition comprising a therapeutic agent and a polymer disposed on the surface of a medical device and a second coating composition comprising a metallic material disposed on the first coating composition. The second coating composition is substantially free of any polymer. Also, the after the second coating composition is disposed on the first coating composition, the second coating composition comprises a plurality of pores that extend from the outer surface of the first composition to the outer surface of the second coating composition.

FIG. 2 shows a cross-sectional view of another embodiment of a coating disposed on at least a portion of a surface of a medical device. In this embodiment medical device 10 has a surface 12 and a coating 20. Coating 20 has a first coating composition 22 comprising a therapeutic agent 30 and a polymer 32 disposed on the surface 12 of the medical device 10. The first coating composition 21 when disposed on the surface 12 has an outer surface 22a. A second coating composition 24 comprising a metallic material 40 is disposed on at least a portion of the first coating composition 22. As shown in FIG. 2, the second coating composition 24, when applied on the first coating composition 22, has an outer surface 24a and a plurality of pores 42. Like FIG. 1, the pores 42 extend from the outer surface 22a of the first coating composition 22 to the outer surface 24a of the second coating composition 24.

As shown in FIGS. 1 and 2, the first and second coating compositions can be disposed on the surface of a medical device in the form of layers. The coating can comprise one layer of each of the first and second coating compositions, as shown in FIGS. 1 and 2. However, more than one layer of each of the first and second coating compositions can be disposed on the surface of a medical device.

In other embodiments, the first coating composition disposed on the surface of medical device in a layer can have a thickness of about 1 micron to about 30 microns or about 1 micron to about 10 microns. Preferably, the first coating composition can have a thickness of about 3 microns to about 15 microns or about 0.8 microns to about 3.5 microns. In some instances, a relatively thicker layer may be preferred to incorporate greater amounts of the therapeutic agent. In addition, a relatively thicker layer may allow a greater amount of a therapeutic agent to be released over time.

The second coating composition comprising a metallic material, when disposed on the first coating composition, can have a thickness of about 0.1 micron to about 30 microns. Preferably, the second coating composition comprising a metallic material, when disposed on the first coating composition, can have a thickness of about 1 micron to about 10 microns. In addition, a relatively thicker film may allow the therapeutic agent to be released more slowly over time.

For the second coating composition, suitable metallic materials include any material that includes a metal such as, but not limited to metals, metal alloys or metal oxides that are biocompatible. Such metallic materials include, but are not limited to, metals and alloys based on titanium (such as nitinol, nickel titanium alloys, thermo-memory alloy materials); stainless steel; tantalum; tungsten; molybdenum; nickel-chrome; or certain cobalt alloys including cobalt-chromium-nickel alloys such as Elgiloy® and Phynox®; PERSS (Platinum EnRiched Stainless Steel) and Niobium. Metallic materials also include clad composite filaments, such as those disclosed in WO 94/16646. Preferred, metallic materials include, platinum enriched stainless steel and zirconium and niobium alloys. Additionally, combinations of more than one metal or alloy can be used in the coatings of the present invention.

In some embodiments, the metallic material comprises at least 5%, at least 10%, at least 20%, at least 30%, at least 40%, at least 50%, at least 60%, at least 70%, at least 80%, at least 90%, at least 95%, at least 97%, at least 99% or more by weight of the second coating composition. Preferably, the metallic material is about 1% to about 80% by weight of the first coating composition. More preferably, the metallic material is about 50% to about 100% by weight of the second coating composition.

The second coating composition is substantially free of any polymer, i.e. contains less than about 50% of polymer by weight of the second coating composition. In some embodiments, the second coating composition is free of any polymer.

The coating can be disposed on the entire surface of the medical device or the coating can be disposed on a portion of the medical device. For example, if a medical device, such as a stent, that has an abluminal surface, i.e. the surface that contacts the body tissue, and an adluminal surface i.e. the surface that faces the lumen of the stent and is opposite the abluminal surface, the coating can be disposed on the abluminal surface while the adluminal surface can be free of the coating.



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stats Patent Info
Application #
US 20120323308 A1
Publish Date
12/20/2012
Document #
13596729
File Date
08/28/2012
USPTO Class
623/116
Other USPTO Classes
623/142, 623/143
International Class
61F2/82
Drawings
13



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