Patent Application
20090319026
Not Applicable
Not Applicable
In some embodiments this invention relates to implantable medical devices, materials used for such devices, and their manufacture. Some embodiments of the invention are directed more specifically to stents used to deliver drugs and other beneficial agents into a bodily lumen.
The use of stents in bodily lumen is well known. A stent is typically delivered in an unexpanded state to a desired location in a bodily lumen via a stent delivery device such as a catheter. Once the stent is at the desired bodily location, it is either expanded with a balloon or other suitable device or allowed to expand, for example, by withdrawing a restraining sheath. Because the stent needs to, in some way, be expanded at the desired location, the stent structure must be flexible.
Typically stents are constructed using either a solid wire member or a thin-walled tubular member made of polymers, organic fabrics, shape memory alloys (such as nitinol), or biocompatible metals (such as stainless steel, gold, silver, titanium, tantalum). In some designs, the stents are formed with such members that act as connectors and struts. These connectors and struts create a repeating or non-repeating pattern to allow for the expansion of the stent while also providing structural support.
In addition to providing structural support in the bodily lumen, stents have been used to supply a wide variety of treatments by delivering drugs and other beneficial agents to a desired bodily location. Such agents can be coated on the stent, or can be contained within the stent with holes for the drug to elute at the proper location.
While surface coatings provide an efficient means of manufacturing a stent to deliver an agent, they have several disadvantages. Surface coatings can provide very little control over the release of the drug into the lumen; the drugs might breakdown too easily, or not easily enough, depending on certain conditions. While the rapid breakdown of the surface coating can be improved by increasing the thickness of the surface coat, this increases the thickness of the stent as a whole, which can lead to increased trauma to the lumen during implantation, reduced flow rates, and increased vulnerability of the coating to damage or failure. In addition because the surface coating can erode, unwanted space may be created between the vessel wall and the stent, allowing for undesirable motion between the stent and the wall. In addition, many types of drugs and beneficial agents cannot currently be delivered using a surface coating, so treatment options with a surface coated stent are limited.
Another well-known means of drug delivery is to manufacture the stent with a plurality holes or other openings in the stent to allow for controlled release of the agent. The stent openings or holes are loaded with the desired beneficial agent, and the stent is implanted in the lumen. This design allows the stent to better achieve a desired agent delivery profile and allows the stent to deliver a relatively large volume of an agent, but also has its drawbacks. Unlike the surface coated stents, creating holes and other openings can negatively affect the structural integrity of the stent.
Accordingly, it would be desirable to have a drug delivery device that would provide an effective means of releasing the beneficial agent while also maintaining the structural integrity of the device.
All US patents and applications and all other published documents mentioned anywhere in this application are incorporated herein by reference in their entirety.
Without limiting the scope of the invention a brief summary of some of the claimed embodiments of the invention is set forth below. Additional details of the summarized embodiments of the invention and/or additional embodiments of the invention may be found in the Detailed Description of the Invention below.
A brief abstract of the technical disclosure in the specification is provided as well for the purposes of complying with 37 C.F.R. 1.72.
In at least one embodiment the present invention involves merging various materials to create a composite structure for a stent such that the stent can provide various means of drug delivery while maintaining its overall structure. The composite structure is made of two or more layers of materials fused, bonded, or joined in some way. The outer layers and/or inner layers may have holes, reservoirs, or openings that allow for the delivery of drugs.
In at least one embodiment, the stent structure has three layers where the center layer remains solid and holes, reservoirs or openings are made in the outer and/or inner layer of the stent for drug delivery. These reservoirs only extend to the solid inner layer so that the stent maintains its structure, while allowing the reservoir to be maximized in size. The layers can be of the same or different materials.
In at least one embodiment, the center layer can have a pattern such as checks, braids, or slots such that at least some of the openings in the outer layer effectively extend through the entire wall thickness of the stent. In some embodiments the stent structure is provided with two or more layers with holes, reservoirs, or openings through one, several or all of the layers.
In at least one embodiment the invention is directed to a method of manufacturing a composite stent. An example of one method comprises the use of laser, mechanical, water jet, etc. or other mechanisms to cut, drill, bore or otherwise form holes or reservoirs with at least one opening in the desired layer or layers and then join the layers into a single composite sheet. The sheet is later rolled and the ends welded together to form a tube of composite material from which a stent may be cut. Another method of manufacturing the composite stent is to coat, wrap or otherwise affix the material to a wire or other structural member. Once the structural member or wire is coated with the material, reservoirs could be cut into the material.
Additional details and/or embodiments of the invention are discussed below. These and other embodiments which characterize the invention are pointed out with particularity in the claims annexed hereto and forming a part hereof. However, for further understanding of the invention, its advantages and objectives obtained by its use, reference should be made to the drawings which form a further part hereof and the accompanying descriptive matter, in which there is illustrated and described embodiments of the invention.
A detailed description of the invention is hereafter described with specific reference being made to the drawings.
a-2d show cross sections of the composite structure stent of four different embodiments.
a-3d show a cross sectional views of the composite stent walls of four different embodiments.
While this invention may be embodied in many different forms, there are described in detail herein specific embodiments of the invention. This description is an exemplification of the principles of the invention and is not intended to limit the invention to the particular embodiments illustrated.
For the purposes of this disclosure, like reference numerals in the figures shall refer to like features unless otherwise indicated.
In one embodiment, the invention is directed to a stent such as that shown generally at 100 in
As such, a wide variety of materials are suitable for use in the construction of the wall 12. For example, in some embodiments the support layer 30 is constructed from any of a variety of metals including, but not limited to: stainless steel, titanium, cobalt, chromium, platinum, and/or alloys thereof (i.e. cobalt chromium, platinum chromium, etc.). In some embodiments layers 20 and 40 are constructed of any of a variety of biocompatible polymer materials. Examples of suitable polymer materials include but are not limited to: polyurethane, polyethylene (an/or blends thereof), polylactic acid (PLA), poly(lactic-co-glycolic acid) (PLGA), polycarbonate blends, etc.
In some embodiments one or both of the first and second layers 20 and 40 are constructed of a biocompatible metal similar or different than the material of the support layer 30.
Each layer 20, 30, 40 has a given thickness 25, 35, 45. Thicknesses 25, 35, 45 may or may not be equal (e.g. thickness 25 of first layer 20 may or may not be the same as thickness 45 of second layer 40, and thicknesses 25, 45 may or may not be the same as thickness 35 of support layer 30). Together, thicknesses 25, 35, 45 equal the overall thickness 15 of the wall 12.
Again referring to
The depth 65 of the reservoir 50 may or may not penetrate through the entire thickness 25 of first layer 20, and furthermore depth 65 may or may not penetrate through overall stent thickness 15. In other words, each reservoir 50 is not necessarily a throughhole, and depth 65 may or may not be equivalent to thickness 25 or overall stent thickness 15. Depth 65 is only limited by overall stent thickness 15 and is not limited by thickness 25, 35, 45 of layer 20, 30, 40.
In some embodiments, the sides 60 of the reservoirs 50 are defined by first layer 20 or second layer 40, and the bottom 62 of the reservoir 50 is defined by the support layer 30. In such embodiments, the support layer 30 can be of a material that is porous, or of a lose braid, or may be made of a pattern (including but not limited to checks, braids, or slots) such that openings 50 on opposing sides of the support layer 30 may have some degree of fluid communication, thereby allowing the opening 50 to act as a throughhole without compromising the structural integrity of the support layer 30 and the stent member 17.
Referring now to
An opening in the stent 100 of inner diameter 120 must remain so that a balloon or other device can be used to expand the stent and also to allow for fluid flow in the vessel. In addition, inner diameter 120 can remain constant or may vary throughout stent 100. Outer diameter 140 also can remain constant or may vary throughout stent 100.
Still referring to
Referring to
In some embodiments, the support layer, first layer, or second layer can be constructed of one or more wires or wire-like members.
In order to manufacture the composite structure and create the stent, several embodiments are presented below, but are not limited to these embodiments.
Referring to
Referring now to
Another method of creating the composite sheet 360 involves depositing layers of material directly onto a first layer or a support layer. The material can be deposited using techniques such as those, described in U.S. Pat. No. 4,485,387 to Drumheller and incorporated herein by reference, to create the walls of the reservoirs for the first layer, or can be sequentially deposited using techniques such as vapor deposition. Sintering and/or molding can also be used to create multiple-layered composite tubes depending on the material. The composite tube can also be made by starting with a first layer shaped into a tube and filling the tube with another material. After that material solidifies, it can be bored out to create a tube of two materials. This process can be repeated again for tubes of more than two materials, again by either boring out or gun drilling out the center area in order to make a tubular structure.
Another embodiment would be to cut a first inner layer with drug reservoirs from a tube using conventional stent processing techniques as laser cutting. A support layer could then be wrapped around and joined to the first layer. A second layer could then be wrapped around and joined to the support layer. Preferably the second layer would be laser cut with drug reservoirs prior to bonding to the support layer, but if the second layer remained solid the reservoirs could be removed prior to the stent pattern being cut. Once the various layers are joined together the stent pattern could then be cut out.
Another method for manufacturing the device is to start with a wire or other tubular member of some material and then coat the wire or wrap the wire with another material to form a first layer. Once coated, reservoirs could be cut into the first outer layer. The wire or tubular member could then be shaped into stent undulation columns. The undulation columns could be joined together by welding, securing together with another material such as sutures, or attached by other methods such as adhesives.
In some embodiments the stent includes one or more areas, bands, coatings, members, etc. that is (are) detectable by imaging modalities such as X-Ray, MRI, ultrasound, etc. In some embodiments at least a portion of the stent and/or adjacent assembly is at least partially radiopaque. The imaging modality may be included into one or more of the various layers of the stent 100, such as the support layer, first layer, second layer, etc.
The above disclosure is intended to be illustrative and not exhaustive. This description will suggest many variations and alternatives to one of ordinary skill in this art. The various elements shown in the individual figures and described above may be combined or modified for combination as desired. All these alternatives and variations are intended to be included within the scope of the claims where the term “comprising” means “including, but not limited to”.
Further, the particular features presented in the dependent claims can be combined with each other in other manners within the scope of the invention such that the invention should be recognized as also specifically directed to other embodiments having any other possible combination of the features of the dependent claims.
This completes the description of the preferred and alternate embodiments of the invention. Those skilled in the art may recognize other equivalents to the specific embodiment described herein which equivalents are intended to be encompassed by the claims attached hereto.
