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Multiple scaffold design and coating thereof

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20130035753 patent thumbnailZoom

Multiple scaffold design and coating thereof


A multiple stent structure including a plurality of stent bodies arranged end to end in which adjacent stent bodies of the structure are connected by a severable connecting portion disposed between the adjacent stent bodies is disclosed. A method of coating a plurality of stents including depositing a coating on the multiple stent structure and severing the severable connecting portions to disconnect the plurality of stent bodies is disclosed.
Related Terms: Scaffold Disconnect

Browse recent Abbott Cardiovascular Systems Inc. patents - Santa Clara, CA, US
USPTO Applicaton #: #20130035753 - Class: 623 116 (USPTO) - 02/07/13 - 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

Inventors: Yung-ming Chen, Henjen Ho

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The Patent Description & Claims data below is from USPTO Patent Application 20130035753, Multiple scaffold design and coating thereof.

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BACKGROUND

Stents act as scaffoldings, functioning to physically hold open and, if desired, to expand the wall of the passageway of a target vessel. Stents are often used in the treatment of atherosclerotic stenosis and/or restenosis in blood vessels. “Stenosis” refers to a narrowing or constriction of the diameter of a bodily passage or orifice. Typically, stents are capable of being compressed, so that they can be inserted through small cavities via catheters, and then expanded to a larger diameter once they reach their target vessel. Mechanical intervention via stents has reduced the rate of restenosis; restenosis, however, is still a significant clinical problem. “Restenosis” refers to the reoccurrence of stenosis in a blood vessel or heart valve after it has been treated (as by balloon angioplasty or valvuloplasty) with apparent success. Accordingly, stents have been modified to perform not only as a mechanical scaffolding, but also to provide biological therapy.

Biological therapy can be achieved by medicating a stent, typically referred to as a drug delivery stent. Drug delivery stents provide for the local administration of a therapeutic substance at the diseased site. In contrast, systemic administration of a therapeutic substance may cause adverse or toxic side effects for the patient because large doses are needed in order for the therapeutic substance to have an efficacious effect at the diseased site. Thus, local delivery is a preferred method of treatment in that smaller total levels of medication are administered in comparison to systemic dosages, but are concentrated at a specific site. Local delivery therefore produces fewer side effects and achieves more favorable results.

Stents may be made of biostable materials that remain at an implant site permanently. However, the clinical need for a stent at an implant site may be temporary. Once treatment is complete, which may include structural tissue support and/or drug delivery, it may be desirable for the stent to be removed or disappear from the treatment location. One way of having a stent disappear may be by fabricating a stent in whole or in part from materials that erode or disintegrate through exposure to conditions within the body. Stents fabricated from bioresorbable, biodegradable, bioabsorbable, and/or bioerodable materials such as bioresorbable polymers can be designed to completely erode only after the clinical need for them has ended.

A typical method for medicating an implantable device includes, for example, applying a composition containing a polymer, a solvent, and a therapeutic substance to the implantable device using conventional techniques, such as spray-coating or dip-coating. The method further includes removing the solvent, leaving on the implantable device surface a coating of the polymer with the therapeutic substance impregnated in the polymer.

In a typical spray-coating method, a stent is mounted on a mandrel of a spray-coating device. Generally, the stent will rest on, or contact components of, a mandrel (or the mandrel itself) which supports the stent and allows it to rotate during a spray-coating process. The contact between the portions of the mandrel and stent, however, inevitably cause coating defects. These defects can include cob-webbing, tearing, bridging, clumping and/or lack of coating on portions of the stent. The embodiments of the present invention are intended to address coating defect issues caused by conventional mandrel designs.

Another issue with conventional stent coating operations is one of efficiency and cost. Stent coating is typically performed one stent or scaffold at a time. For each stent coated, the coating equipment must be set up. In addition, each stent or scaffold must be loaded prior to coating and unloaded after coating. Thus, machine utilization is limited by coating only one stent for machine set-up, loading, and unloading processes.

SUMMARY

Various embodiments of the present invention include a medical device comprising: a structure comprising a plurality of stent bodies arranged end to end, wherein adjacent stent bodies of the structure are connected by a severable connecting portion disposed between the adjacent stent bodies, wherein at least one of the stent bodies at an end of the structure comprises a severable end portion at the end of the structure.

Further embodiments of the present invention include a method of coating a plurality of stents comprising: providing a structure comprising a plurality of stent bodies arranged end to end, wherein adjacent stent bodies along the structure are connected by a severable connecting portion disposed between the adjacent stent bodies; and depositing a coating on the plurality of stent bodies; and severing the severable connecting portions to disconnect the plurality of stent bodies.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 illustrates an exemplary stent.

FIG. 2 illustrates a method of coating a stent with a spray-coating device.

FIGS. 3A-B illustrates an alternative manner of supporting a stent during the coating process.

FIG. 4A depicts an exemplary multiple stent structure composed of two stent bodies connected by a severable portion.

FIG. 4B depicts a close-up view of the severable portion of FIG. 4A.

FIG. 4C depicts a close-up view of the proximal end of a multiple stent structure.

FIG. 5A depicts a strut that is a portion of a stent that is connected to a tab by a gate.

FIG. 5B depicts an alternative embodiment of stent bodies connected to a tab by gates.

FIG. 6 depicts a portion of a stent showing a side wall, an inner surface, and an outer surface of a strut.

FIG. 7A depicts a mandrel designed to support a multiple stent structure as shown in FIG. 4A.

FIG. 7B depicts a longitudinal cross section of the mandrel of FIG. 7A.

FIG. 8A depicts a multiple stent structure-mandrel assembly.

FIG. 8B depicts an axial cross section of assembly of FIG. 8A.

FIG. 9 depicts one embodiment of system for coating a multiple stent structure.

FIG. 10 illustrates one form of a method using the multiple stent structure described in FIG. 4A with a modified version of the spray-coating device of FIG. 2.

DETAILED DESCRIPTION

The implantable medical device used in conjunction with the present invention may be any implantable medical device, examples of which include self-expandable stents, balloon-expandable stents, micro-depot or micro-channel stents, stent-grafts and grafts. Examples of stents include neurological, coronary, peripheral and urological stents. In some embodiments, the underlying structure of the implantable medical device can be virtually any design.

FIG. 1 illustrates a stent 10, which in various embodiments may be metallic or polymeric. In either form, the stent 10 can include a plurality of struts 12 linked by connecting elements 14, with the struts 12 and connecting elements 14 surrounding or partially surrounding interstitial spaces 16. The plurality of struts 12 can be configured in an annular fashion in discrete “rows” such that they form a series of “rings” throughout the body of the stent 10. Thus, the stent 10 can include a proximal ring 18, a distal ring 20 and at least one central ring 22.

A stent such as stent 10 may be fabricated from a polymeric tube or a sheet by rolling and bonding the sheet to form the tube. A tube or sheet can be formed by extrusion or injection molding. A stent pattern, such as the one pictured in FIG. 1, can be formed in a tube or sheet with a technique such as laser cutting or chemical etching. The stent can then be crimped on to a balloon or catheter for delivery into a bodily lumen.

An implantable medical device of the present invention can be made partially or completely from a biodegradable, bioresorbable, bioabsorbable, or biostable polymer. A polymer for use in fabricating an implantable medical device can be biostable, bioresorbable, bioabsorbable, biodegradable or bioerodable. Biostable refers to polymers that are not biodegradable. The terms biodegradable, bioresorbable, bioabsorbable, and bioerodable are used interchangeably and refer to polymers that are capable of being completely degraded and/or eroded into different degrees of molecular levels when exposed to bodily fluids such as blood and can be gradually resorbed, absorbed, and/or eliminated by the body. The processes of breaking down and absorption of the polymer can be caused by, for example, hydrolysis and metabolic processes.

A stent made from a bioresorbable polymer is intended to remain in the body for a duration of time until its intended function of, for example, maintaining vascular patency and/or drug delivery is accomplished. After the process of degradation, erosion, absorption, and/or resorption has been completed, no portion of the biodegradable stent, or a biodegradable portion of the stent will remain. In some embodiments, very negligible traces or residue may be left behind.

A therapeutic coating may be formed over a stent by applying a composition containing a polymer, a solvent, and a therapeutic substance to the stent using techniques, such as spray-coating or dip-coating. The solvent is then removed leaving a coating on the stent surface including the polymer with the therapeutic substance impregnated in the polymer.

FIG. 2 illustrates a prior art spray-coating device 100 and process for coating single stent. The spray-coating device 100 can include the following elements: a stent movement and rotating device 102, a support member 104 and a stent holding device 106 for rotation and movement of the stent 10 before, during and/or after the coating process; a nozzle 108 with an air shroud device 110 for spray-coating the stent 10; and an exhaust system 112 to remove excess spray from the target area on the stent 10. In some applications, the stent 10 can be mounted onto the stent holding device 106 forming an assembly thereof. The assembly can then be mounted into a socket of the support member 104 for coating with composition 114 from the air shroud 110 of the nozzle 108. In some applications, the stent movement and rotating device 102 can move the assembly in a linear direction (arrow 116) to achieve a targeted or uniform coating. In some applications, the support member 104 can rotate the assembly (arrow 118) to achieve a targeted or uniform coating. In some applications, a combination of linear and rotational movements can be used to coat the stent 10. The exhaust system 112 can function to remove excess composition during the spray-coating process.

In the spray-coating method described previously, there are contact areas between the stent 10 and the stent holding device 106. Depending on the stent and its holding device, contact areas are the source of the coating defects, in the form of cob-webbing, tearing, bridging, clumping and/or lack of coating on portions of the stent.

FIGS. 3A-B illustrates an assembly used in supporting a stent during the coating process. FIG. 3A depicts a core mandrel assembly 200 which contains a core wire 206 slanted collets 202 and 204 and mini coils 207 and 209. FIG. 3B is to show placement of a stent (arrow 212) and the final assembly with a stent 208. Coils 207 and 209 are used to provide minimal contact surface area to loosely support the stent 208 during the coating process. Mandrel assembly 200 rotates 210 during deposition of a coating composition on stent 208, but the stent is not rotating in one to one ratio compared to the mandrel assembly. Coils 207 and 209 have diameters and lengths significantly smaller than stent 208. Nevertheless, the contact of coils 207 and 209 can create coating defects in the stent\'s 208 inner surface, thus it leads to suboptimal coating quality.

Embodiments of the present invention solve both of the problems of the conventional coating methods by eliminating the contact defects and allowing coating of more than one stent during a coating process. The embodiments of the present invention include coating a multiple stent structure, which including a plurality of stent bodies arranged end to end in which adjacent stent bodies are connected by a severable support element disposed between the adjacent stent bodies. “End-to-end” is defined generally as with the end of one object in arranged lengthwise, such as along a cylindrical axis in the case of tubular objects, with the end of another object. “Adjacent stent bodies” refer to stent bodies in an end to end arrangement in the structure that are connected by a connecting portion and which have no intervening stent bodies between them. In further embodiments, the ends of stent bodies at one or both ends of the structure may also include severable portions or support elements.

In certain embodiments, the multiple stent structure is disposed over a stent support system. A coating is deposited on the multiple stent structure that is disposed over the stent support system. As described below, the multiple stent structure can include one or more of the severable portions or support elements that can engage the stent support system to allow deposition of coating material on the structure FIG. 7A-B and FIG. 8A-B. After the coating is formed over the structure and after an optional drying step, the severable portions are severed or removed to disconnect the plurality of stent bodies from one another to provide a plurality of disconnected coated stent bodies.

In some embodiments, a finished coating can be formed directly over the multiple stent structure composed of the plurality of stent bodies without unloading the stent structure from the support system. Therefore, the embodiments described allow coating multiple stent bodies without loading and unloading the stent bodies for each stent body. The plurality of stent bodies are coated in one coating operation. A coating operation refers to forming a coating over the stent structure which involves loading and unloading the stent structure on a support system. A stent body refers to a longitudinal section of a repeating pattern of struts, as described above, that is intended to be implanted into a patient and that does not include the severable support elements or the other stent bodies.

FIG. 4A depicts an exemplary multiple stent structure 230 composed of two stent bodies 232 and 234 connected by a severable portion or support element 240. Structure 230 includes a stent body 232 and a stent body 234. Stent body 232 has a proximal end 232A and a distal end 232B and stent body 234 has a proximal end 234A and a distal end 234B. Stent bodies 232 and 234 each are scaffolds and each is made up of a pattern composed of interconnected structural elements. Specifically, stent bodies 232 and 234 include undulated cylindrical rings 236 and 249 connected by linking elements 238.

FIG. 4B depicts a close-up view of severable portion 240, the severable portion 240 of multiple stent structure 230 includes a connecting band, ring, or tube 242 (terms which are used interchangeably unless otherwise used specifically). Severable portion 240 can alternatively include a tab. Tube 242 has a width W1.

Severable portion 240 also includes at least one “gate”, flange or bar 244 (terms which are used interchangeably unless otherwise used specifically). Gate 244 connects tube 242 to distal end 232B of stent 232, specifically, to crest 246 of distal ring 248 of stent 232. Gate 250 connects tube 242 to proximal end 234A of stent 234, specifically, to crest 252 of proximal ring 254 of stent 234.

As indicated above, the ends of stent bodies at one or both ends of the multiple stent structure may also include severable support portions or elements. Referring to FIG. 4A, a proximal end 256 and a distal end 258 of multiple stent structure 230 include severable portions 260 and 262, respectively. FIG. 4C depicts a close-up view of proximal end 256 of multiple stent structure 230. Severable portion 260 includes an end tube 264 and at least one gate 266 that connects tube 264 to proximal end 232A of stent 232, specifically, to crest 268 of proximal ring 270 of stent 232. In FIG. 4A, severable portion 262 likewise includes end tube 272 and gate 274 connects tube 272 to distal end 234B of stent 234. Tubes 264 and 272 have a width W2.

As an alternative to a tube or band at the ends of the multiple stent structure and for connecting adjacent stent bodies, the severable portion may have at least one tab. FIG. 5A depicts a strut 280 and strut 286 that are a portions of adjacent stents in a multiple stent structure. Struts 280 and 286 are at two different circumferential positions of the multiple stent structure. Line A-A corresponds to the cylindrical axis of the multiple stent structure. Strut 280 is connected to a tab 282 by a gate 284. Strut 286 of the adjacent stent is connected to a tab 288 by a gate 290. The tabs have a width W3.

FIG. 5B depicts an alternative embodiment in which the adjacent stent pattern is configured so that the crests of the adjacent struts 292 and 294 are at the same or slightly different circumferential position. Strut 292 is connected to tab 296 by gate 298 and strut 294 is connected to the same tab 296 by gate 300.

FIG. 6 depicts a portion 310 of a stent. A gate may be attached to a strut at a side wall 312, an inner surface 314, an outer surface 316 or any combination thereof of a stent.

In some embodiments, the stent bodies and one or more of the connecting tubes or tabs between adjacent stent bodies and end tubes at the proximal and distal ends of the structure can be monolithic. That is, when the stent pattern is originally cut or etched from a flat sheet or from a tube, the tubes or tabs of the pattern remain attached to the stent pattern by the at least one gate. Stent patterns can be formed by a variety of methods, including but not limited to, laser cutting and etching, such as chemical etching. Other stent pattern formation techniques may be utilized and are known by those skilled in the art.

In some embodiments, the end tubes or connecting tubes may be attached to the stent by a secondary process, such as, for example, by biocompatible glue or solder. In the process in which the stent pattern is cut into a flat sheet (as opposed to directly on a tube), the attaching may be done either after the cutting or after the cut pattern is rolled into a tube forming a stent thereof. In some embodiments, the severable portion can include, for example, a tab or tube attached to some portion of a stent body that is part of a multiple stent structure. Thus, FIG. 4A illustrates an embodiment in which a tube is attached to the sidewall (not shown in this figure) of a ring adjacent to the tube by a gate. In another alternative embodiment, the tube or tab is attached to at least one ring that is not adjacent to the tab or ring by an attachment, for example attaching tube 242 to a ring 249 in FIG. 4A. In any embodiment, the tubes or tabs can be attached monolithically or by secondary processes as explained above. Therefore, the at least one gate can be made from the same material as the stent body or made of different material. In some embodiments, the material for a gate, a tube, and a tab can be any of the polymeric and/or metallic materials disclosed below. For example, the gate can be made of the polymers from which the stent is made and/or coated.

The connecting and end portion(s) of the multiple stent structure, which may be at least one end tube or at least one tab, may function as the connecting support of the multiple stent structure to the spray-coating device (such as those illustrated in FIG. 2) before, during or after the spray-coating process and optionally a drying stage. The connecting portions are severable via the at least one gate on both sides of the connecting portions. For example, gates 244 that connect tube 242 to stent body 232 and gates 250 that connect tube 242 to stent body 234 in FIG. 4A are severed. Additionally, the end portions are severable via the at least one gate connecting the end portions to the proximal and distal ends of the multiple stent structure. For example, gates 266 that connect tube 264 to stent body 232 are severed in FIG. 4C. The gates can be very thin so that they can be easily removed after a spray-coating process. For example, the thickness (or width) of a gate can be between 0.0005″ and 0.0035″, typically 0.002″. In some embodiments, the gates can be perforated about a width segment thereof so as to facilitate breaking off of the gates from the stent bodies of the multiple stent structure. Such perforations can be positioned along any surface of the gate, such as adjacent to the sidewall 312 such that no portion of the gate is left behind after the breaking thereof. In addition, the number of gates can number between one and ten, typically two. Because the weight of the stent is very low (between 1 mg and 50 mg), the number of gates should be minimized to reduce any rough areas caused by severing the connecting and end portion(s) at the at least one gate(s) after a spray-coating process.

In some embodiments, the multiple stent structure can be supported by a mandrel during the coating process. The mandrel may support the structure by engaging the one or more of the severable portion(s). The mandrel may be configured to engage or contact only the severable portion(s) and to make no contact with any of the stent bodies. Additionally, no other portion of the coating device may make contact with the stent bodies which eliminates defects arising from contact points.

In some embodiments, the mandrel may include an elongate member and one or more support portions along its length with a larger diameter than the elongate to provide more rigid support to avoid the deformation to the stent body during the coating process. For example, the diameter of the elongate member may be between 10 and 50% of the support portions. The support portions are adapted to support a multiple stent structure during coating. The elongate member has a diameter less than an inner diameter of a multiple stent structure so that there is no contact between the elongate member and a stent structure mounted on the mandrel. The one or more support portions have an outer diameter the same as the inner diameter of the multiple stent structure. The support portions may have an outer diameter slightly less than the inner diameter of the multiple stent structure, for example, up to 5% less. The support portions may be disks with a width less than or equal to a width of a tube or tab of the end portions or connecting portions. The disk width may be larger than these portions, but not wide enough to contact a stent body.

FIG. 7A depicts a mandrel 320 designed to support a multiple stent structure 230 (see FIG. 4A). Mandrel 320 has an elongate member 322 and three disks 324A, 324B, and 324C disposed along the axis of the elongate member. Elongate member 322 has two end sections 322A and 322B axially proximal and distal from disks 324A and 324C, respectively. Elongate member 322 has a section 322C between disks 324A and 324B and has a section 322D between disks 324B and 324C. As illustrated in FIG. 8A, disks 324A, 324B, and 324C are spaced apart to support multiple stent structure 230 by engaging tubes 264, 242, and 272, respectively.



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stats Patent Info
Application #
US 20130035753 A1
Publish Date
02/07/2013
Document #
13195729
File Date
08/01/2011
USPTO Class
623/116
Other USPTO Classes
427/225
International Class
/
Drawings
10


Scaffold
Disconnect


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