US20190159884A1 - Biodegradable composite yarn structure and method - Google Patents

Abstract

The techniques of this disclosure generally relate to prosthesis formed from a biodegradable composite yarn. The biodegradable composite yarn includes a permanent core and a biodegradable shell. The biodegradable shell slowly dissolves over a period of time when placed in a vessel. As the biodegradable shell dissolves, openings are created in the prosthesis that are filled with tissue from the vessel wall of the vessel. The integration of the tissue into the prosthesis provides biological fixation of prosthesis in the vessel and prevents endoleaks and migration of prosthesis.

Description

CROSS-REFERENCE TO RELATED APPLICATIONS
• This application claims the benefit of U.S. Provisional Application No. 62/591,601, filed on Nov. 28, 2017, entitled “ADVANCED GRAFT MATERIALS FOR ENDOVASCULAR APPLICATIONS” of Borglin et al., which is incorporated herein by reference in its entirety.
FIELD
• The present technology is generally related to an intra-vascular device and method. More particularly, the present application relates to a device for treatment of intra-vascular diseases.
BACKGROUND
• A conventional stent-graft typically includes a radially expandable reinforcement structure, formed from a plurality of annular stent rings, and a cylindrically shaped layer of graft material defining a lumen to which the stent rings are coupled. Stent-grafts are well known for use in tubular shaped human vessels.
• To illustrate, endovascular aneurysmal exclusion is a method of using a stent-graft to exclude pressurized fluid flow from the interior of an aneurysm, thereby reducing the risk of rupture of the aneurysm and the associated invasive surgical intervention.
• The graft material of traditional stent-grafts is extremely hydrophobic and presents a hostile environment for the recruitment and proliferation of cells. The inability of tissue to integrate into the graft material prevents the biological fixation of the stent-graft in vessels and makes the stent-graft susceptible to endoleaks and migration.
SUMMARY
• The techniques of this disclosure generally relate to prosthesis formed from a biodegradable composite yarn. The biodegradable composite yarn includes a permanent core and a biodegradable shell. The biodegradable shell slowly dissolves over a period of time when placed in a vessel. As the biodegradable shell dissolves, openings are created in the prosthesis that are filled with tissue from the vessel wall of the vessel. The integration of the tissue into the prosthesis provides biological fixation of prosthesis in the vessel and prevents endoleaks and migration of prosthesis.
• In one aspect, the present disclosure provides a prosthesis having a biodegradable composite yarn including a permanent core and a biodegradable shell.
• In another aspect, the disclosure provides an assembly including a vessel having a vessel wall and a prosthesis in contact with the vessel wall. The prosthesis includes a permanent core and a biodegradable shell.
• In yet another aspect, the disclosure provides a method including forming a biodegradable composite yarn having a permanent core and a biodegradable shell. The biodegradable composite yarn is combined to form a prosthesis having a biodegradable composite graft material.
• The details of one or more aspects of the disclosure are set forth in the accompanying drawings and the description below. Other features, objects, and advantages of the techniques described in this disclosure will be apparent from the description and drawings, and from the claims.
BRIEF DESCRIPTION OF DRAWINGS
• FIG. 1 is a perspective view of a biodegradable composite yarn stent-graft in accordance with one embodiment.
• FIG. 2 is a cross-sectional view of a biodegradable composite yarn used to fabricate the stent-graft ofFIG. 1 in accordance with one embodiment.
• FIG. 3 is a plan view of the biodegradable composite yarn ofFIG. 2 in accordance with one embodiment.
• FIG. 4 is an enlarged plan view of the region IV of the stent-graft ofFIG. 1 in accordance with one embodiment.
• FIG. 5 is a cross-sectional view of the graft material along the line V-V ofFIG. 4 in accordance with one embodiment.
• FIG. 6 is an enlarged plan view of a section of the graft material including two horizontal biodegradable composite yarns interlaced with two vertical biodegradable composite yarns prior to dissolution of the biodegradable shells in accordance with one embodiment.
• FIG. 7 is a cross-sectional view of the graft material along the line VII-VII ofFIG. 6 upon initial deployment on a vessel wall in accordance with one embodiment.
• FIG. 8 is an enlarged plan view of the section of the graft material ofFIG. 6 after dissolution of the biodegradable shells in accordance with one embodiment.
• FIG. 9 is a cross-sectional view of the graft material along the line IX-IX ofFIG. 8 after a period of time after deployment on the vessel wall in accordance with one embodiment.
• FIG. 10 is a cross-sectional view of a vessel assembly including the stent-graft ofFIG. 1 after initial deployment within a vessel having a dissection in accordance with one embodiment.
• FIG. 11 is an enlarged cross-sectional view of a region XI of the vessel assembly ofFIG. 10.
• FIG. 12 is a cross-sectional view of the region XI of the vessel assembly ofFIG. 10 after a period of time after deployment of the stent-graft within the vessel in accordance with one embodiment.
• FIG. 13 is a cross-sectional view of a vessel assembly including a stent-graft in accordance with one embodiment.
DETAILED DESCRIPTION
• FIG. 1 is a perspective view of a biodegradable composite yarn stent-graft100 in accordance with one embodiment. Referring now toFIG. 1, stent-graft100, sometimes called a prosthesis, includes a biodegradable compositeyarn graft material102 and one or morestent rings104 coupled tograft material102. Illustratively,stent rings104 are self-expanding stent rings, e.g., nickel titanium alloy (NiTi), sometimes called Nitinol, or self-expanding members. The inclusion ofstent rings104 is optional and in oneembodiment stent rings104 are not included. In another embodiment,stent rings104 are balloon expandable stents.
• In accordance with this embodiment,graft material102 includes aproximal opening106 at aproximal end108 ofgraft material102 and adistal opening110 at adistal end112 ofgraft material102.
• Further, stent-graft100 includes a longitudinal axisL. A lumen114 is defined bygraft material102, and generally by stent-graft100.Lumen114 extends generally parallel to longitudinal axis L and betweenproximal opening106 anddistal opening110 of stent-graft100.
• As used herein, the proximal end of a prosthesis such as stent-graft100 is the end closest to the heart via the path of blood flow whereas the distal end is the end furthest away from the heart during deployment. In contrast and of note, the distal end of the catheter is usually identified to the end that is farthest from the operator/handle while the proximal end of the catheter is the end nearest the operator/handle.
• For purposes of clarity of discussion, as used herein, the distal end of the catheter is the end that is farthest from the operator (the end furthest from the handle) while the distal end of stent-graft100 is the end nearest the operator (the end nearest the handle), i.e., the distal end of the catheter and the proximal end of stent-graft100 are the ends furthest from the handle while the proximal end of the catheter and the distal end of stent-graft100 are the ends nearest the handle. However, those of skill in the art will understand that depending upon the access location, stent-graft100 and the delivery system descriptions may be consistent or opposite in actual usage.
• Graft material102 is cylindrical having a substantially uniform diameter. However, in other embodiments,graft material102 varies in diameter, is bifurcated atdistal end112, and/or is a multi-limbed device for branching applications.Graft material102 includes aninner surface116 and an oppositeouter surface118, e.g., cylindrical surfaces in accordance with this embodiment.
• Graft material102 includes biodegradable composite yarns which are woven, knitted, sewn, or otherwise combined to creategraft material102. In one embodiment, yarns are long string like members, sometimes called threads, fibers, or filaments.
• FIG. 2 is a cross-sectional view of abiodegradable composite yarn200 used to fabricate stent-graft100 ofFIG. 1 in accordance with one embodiment.FIG. 3 is a plan view ofbiodegradable composite yarn200 ofFIG. 2 in accordance with one embodiment.
• Referring toFIGS. 2 and 3 together,biodegradable composite yarn200 includes apermanent core202 and abiodegradable shell204. InFIGS. 2 and 3,biodegradable shell204 as indicated in a dashed line to allow visualization ofpermanent core202 for clarity. For example, in the view ofFIG. 3,permanent core202 would be entirely encased withinbiodegradable shell204 and would not be visible.
• In one embodiment,biodegradable composite yarn200 is formed by coextrudingpermanent core202 and abiodegradable shell204 at the same time.Permanent core202 is completely enclosed and encased inbiodegradable shell204.
• In one embodiment,permanent core202 is permanent, e.g., will last in the human body for an extended period of time such as 10 years or more.Permanent core202 is sometimes called non-absorbable, persistent, or an inner non-absorbable fiber. In one embodiment,permanent core202 is polyester terephthalate (PET), expanded polyester terephthalate (ePET), or other permanent graft material or textile.
• In contrast topermanent core202,biodegradable shell204 is a biodegradable material, i.e., is biodegradable.Biodegradable shell204 is sometimes called an outer biodegradable layer. As used herein, biodegradable means capable of being broken down in the human body, e.g., through contact with fluid such as blood and/or tissue such as a vessel wall. Examples ofbiodegradable shell204 include polymer polyglycolic-lactic acid (PLGA), poly(glycerol sebacate) (PGS), Polyglycolic acid (PGA), or Poly Lactic Acid (PLA).
• Permanent core202 provides long term mechanical strength whilebiodegradable shell204 provides acute strength and impermeability to prevent endoleaks. As discussed in further detail below, asbiodegradable shell204 degrades, the drop in textile density creates openings, sometimes called ingress channels, through which tissue grows.
• In one embodiment,permanent core202 is a long cylindrical structure, e.g., a string like member, having a diameterD. Permanent core202 includes a longitudinal axis L1 at a center ofpermanent core202.Permanent core202 includes a cylindricalouter surface206.
• Biodegradable shell204 is an annular cylinder, sometimes called a hollow cylinder, that surrounds and encasespermanent core202.Biodegradable shell204 also includes longitudinal axis L1 such thatbiodegradable shell204 andpermanent core202 are coaxial.Biodegradable shell204 includes a cylindricalinner surface208 and a cylindricalouter surface210. Cylindricalinner surface208 is separated from cylindricalouter surface210 by a thickness T1, sometime called the outer radius ofbiodegradable shell204. Cylindricalinner surface208 ofbiodegradable shell204 is directly on cylindricalouter surface206 ofpermanent core202.
• FIG. 4 is an enlarged plan view of the region IV of stent-graft100 ofFIG. 1 in accordance with one embodiment. Referring now toFIGS. 1 through 4 together,graft material102 includes a plurality of biodegradablecomposite yarns200. Biodegradablecomposite yarns200 are illustrated as including a plurality of vertical biodegradablecomposite yarns200V and a plurality of horizontal biodegradablecomposite yarns200H interlaced with one another. This arrangement of biodegradablecomposite yarns200 is illustrative only and in light of this disclosure those of skill in the art will understand that biodegradablecomposite yarns200 can be combined in any one of a number of different fashions to formgraft material102. For example, biodegradablecomposite yarns200 are woven, knitted, sewn, or otherwise combined to creategraft material102.
• FIG. 5 is a cross-sectional view ofgraft material102 along the line V-V ofFIG. 4 in accordance with one embodiment. Referring out ofFIGS. 4 and 5 together, in accordance with this embodiment,biodegradable shell204 has a greater elasticity thanpermanent core202. This elasticity ofbiodegradable shell204 allows a tight interlacing of biodegradablecomposite yarns200.
• For example, a vertical biodegradablecomposite yarns200V contacts a horizontal biodegradablecomposite yarns200H as illustrated inFIG. 5. At the point ofcontact502,biodegradable shells204 of each of biodegradablecomposite yarns200H,200V are pressed into one another and deform due to the elasticity ofbiodegradable shells204. Accordingly, the un-deformed standard thickness T1 ofbiodegradable shells204 is reduced to a lesser thickness T2 at point ofcontact502.
• Due to this elasticity and deformation ofbiodegradable shells204, biodegradablecomposite yarns200 are tightly interlaced minimizing the porosity ofgraft material102. This, in turn, minimizes and essentially eliminates leaks throughgraft material102, e.g., type IV endoleaks.
• Over time,biodegradable shells204 biodegrade and dissolve. This creates/enlarges openings, sometimes called ingress channels, ingraft material102 to encourage tissue integration therein. An example of how the dissolution ofbiodegradable shells204 and tissue integration is set forth below in reference toFIGS. 6-9.
• FIG. 6 is an enlarged plan view of a section ofgraft material102 including two horizontal biodegradablecomposite yarns200H interlaced with two vertical biodegradablecomposite yarns200V prior to dissolution ofbiodegradable shells204 in accordance with one embodiment.FIG. 7 is a cross-sectional view ofgraft material102 along the line VII-VII ofFIG. 6 upon initial deployment on avessel wall702 in accordance with one embodiment.
• Referring now ofFIGS. 1, 6 and 7 together, stent-graft100 is deployed within a vessel including thevessel wall702. For example, stent-graft100 is deployed to treat an abdominal aortic aneurysm, a thoracic aortic aneurysm, a dissection, or other medical condition.
• Upon initial deployment,biodegradable shells204 remain in their original form and are undissolved. As discussed above, prior to dissolution ofbiodegradable shells204,graft material102 is essentially impermeable.
• InFIGS. 6 and 7, apore602, e.g., a small space, is illustrated. For example, pore602 is defined by two adjacentvertical yarns200V and two adjacenthorizontal yarns200H. Theother pores602 ingraft material102 are defined in a similar manner.Pores602 are typically formed due to the overlapping nature ofyarns200 and the inability to makeyarns200 completely flush with one another along the entire length ofyarns200. Although apore602 is illustrated, in other embodiments,graft material102 has an absence of pores and is completely impermeable.
• Paying particular attention toFIGS. 1 and 7 together, stent-graft100contacts vessel wall702. Accordingly, fluid flows though stent-graft100, i.e., throughlumen114. Due to the impermeability of stent-graft100,vessel wall702 including any defect associated therewith, e.g., a dissection or aneurysm, are excluding from the pressurized fluid flow through stent-graft100.
• FIG. 8 is an enlarged plan view of the section ofgraft material102 ofFIG. 6 after dissolution ofbiodegradable shells204 in accordance with one embodiment.FIG. 9 is a cross-sectional view ofgraft material102 along the line IX-IX ofFIG. 8 after a period of time after deployment onvessel wall702 in accordance with one embodiment.
• Referring now ofFIGS. 1, 8-9 together, after a period of time, biodegradable shells204 (seeFIGS. 6-7) dissolve. However,permanent cores202 remain in the same configuration as when initially deployed or approximately there so.
• Biodegradable shells204 slowly dissolve fromouter surface210 toinner surface208 over a period of time. Asbiodegradable shells204 dissolve,openings902 are created betweenpermanent cores202.Openings902 increase in size over time asbiodegradable shells204 dissolve.
• Over time,biodegradable shells204 are replaced withtissue904 fromvessel wall702 that integrates within and throughopenings902 as illustrated inFIG. 9.Tissue904 encasespermanent core202 and fillsopenings902 preventing leakage throughopenings902 in accordance with this embodiment. The integrate oftissue904 intograft material102 provides biological fixation of stent-graft100 in vessels and prevents endoleaks and migration of stent-graft100. Generally, stent-graft100 becomes integrated with the vessel includingvessel wall702.
• As discussed below in reference toFIGS. 10-13, stent-graft100 is used to cover and treat various defects in a vessel.
• FIG. 10 is a cross-sectional view of avessel assembly1000 including stent-graft100 ofFIG. 1 after initial deployment within avessel1002 having a dissection in accordance with one embodiment.FIG. 11 is an enlarged cross-sectional view of a region XI ofvessel assembly1000 ofFIG. 10. InFIG. 10, stent-ring104 is not illustrated for simplicity.
• Referring toFIGS. 1, 10-11 together, a dissection is a condition in which aninner layer1006 ofvessel1002 tears to have adissection opening1008. Fluid, e.g., blood, flows throughdissection opening1008 and into afalse lumen1010 betweeninner layer1006 and one or more otherouter layers1012 ofvessel1002. Left untreated,false lumen1010 can ruptureouter layers1012 ofvessel1002 leading to serious complications and often death.
• In accordance with this embodiment, stent-graft100 is deployed to cover and excludedissection opening1008. As discussed above, when initially deployed, stent-graft100 is impermeable thus sealingdissection opening1008 and preventing pressurized fluid flow throughfalse lumen1010.
• FIG. 12 is a cross-sectional view of region XI ofvessel assembly1000 ofFIG. 10 after a period of time after deployment of stent-graft100 withinvessel1002 in accordance with one embodiment. Referring now toFIGS. 1, 10-12, due to the covering and exclusion of the dissection with stent-graft100,dissection opening1008 heals and closes andfalse lumen1010 collapses. At the same time,biodegradable shells204 dissolve allowingtissue904 integration intoopenings902 of stent-graft100 including betweenpermanent cores202.
• FIG. 13 is a cross-sectional view of avessel assembly1302 including a stent-graft1300 in accordance with one embodiment. Stent-graft1300 ofFIG. 13 is similar to stent-graft100 ofFIG. 1 and only the significant differences are discussed below. Stent-graft1300 is illustrated with an absence of stent-rings104 for simplicity but includes stent-rings104 in other embodiments.
• In accordance with this embodiment, agraft material102A and more generally stent-graft1300 includes at least threezones1304,1306,1308 in accordance with this embodiment.Proximal seal zone1304 extends fromproximal end108 toexclusion zone1306.Exclusion zone1306 extends fromproximal seal zone1304 todistal seal zone1308.Distal seal zone1308 extends fromexclusion zone1306 todistal end112.
• Proximal seal zone1304 anddistal seal zone1308 include biodegradable compositeyarn graft material102 similar to that discussed. More particularly, onlyproximal seal zone1304 anddistal seal zone1308 include biodegradablecomposite yarns200 havingpermanent cores202 andbiodegradable shells204.
• However,exclusion zone1306 is formed of non-biodegradable material, is permanent, and impermeable. For example, in accordance with various embodiments,exclusion zone1306 is polyester terephthalate (PET), expanded polyester terephthalate (ePET), or other similar graft material or textile.
• Stent-graft1300 is deployed into avessel1310 to exclude ananeurysm1312 using any one of a number of techniques well known to those of skill in the art. More particularly,proximal seal zone1304 anddistal seal zone1308 are deployed proximally and distally toaneurysm1312, respectively.
• Proximal seal zone1304 anddistal seal zone1308 directly contact avessel wall1314 ofvessel1310. Over time,biodegradable shells204 ofproximal seal zone1304 anddistal seal zone1308 dissolve. This allows tissue integration intoproximal seal zone1304 anddistal seal zone1308 of stent-graft1300 in a manner similar to that discussed above. This, in turn, prevents leakage aroundproximal seal zone1304 anddistal seal zone1308 and migration of stent-graft1300.
• Further,exclusion zone1306 is deployed overaneurysm1312, i.e., to excludeaneurysm1312. Accordingly, blood flows throughexclusion zone1306 and more generally through stent-graft1300 thus excludinganeurysm1312. Asexclusion zone1306 may not contactvessel wall1314 butspan aneurysm1312,exclusion zone1306 does not include biodegradable material such that openings, e.g., seeopenings902 ofFIGS. 8-9, are not created in stent-graft1300 inexclusion zone1306.
• It should be understood that various aspects disclosed herein may be combined in different combinations than the combinations specifically presented in the description and accompanying drawings. It should also be understood that, depending on the example, certain acts or events of any of the processes or methods described herein may be performed in a different sequence, may be added, merged, or left out altogether (e.g., all described acts or events may not be necessary to carry out the techniques). In addition, while certain aspects of this disclosure are described as being performed by a single module or unit for purposes of clarity, it should be understood that the techniques of this disclosure may be performed by a combination of units or modules associated with, for example, a medical device.
• In one or more examples, the described techniques may be implemented in hardware, software, firmware, or any combination thereof. If implemented in software, the functions may be stored as one or more instructions or code on a computer-readable medium and executed by a hardware-based processing unit. Computer-readable media may include non-transitory computer-readable media, which corresponds to a tangible medium such as data storage media (e.g., RAM, ROM, EEPROM, flash memory, or any other medium that can be used to store desired program code in the form of instructions or data structures and that can be accessed by a computer).
• Instructions may be executed by one or more processors, such as one or more digital signal processors (DSPs), general purpose microprocessors, application specific integrated circuits (ASICs), field programmable logic arrays (FPGAs), or other equivalent integrated or discrete logic circuitry. Accordingly, the term “processor” as used herein may refer to any of the foregoing structure or any other physical structure suitable for implementation of the described techniques. Also, the techniques could be fully implemented in one or more circuits or logic elements.

Claims (20)

What is claimed is:

1. A prosthesis comprising:

a biodegradable composite yarn comprising:

a permanent core; and

a biodegradable shell.

2. The prosthesis ofclaim 1 further comprising:

a biodegradable composite yarn graft material comprising the biodegradable composite yarn combined together.

3. The prosthesis ofclaim 2 wherein the permanent core and the biodegradable shell are coextruded to form the biodegradable composite yarn.

4. The prosthesis ofclaim 1 wherein the permanent core is encased within the biodegradable shell.

5. The prosthesis ofclaim 1 wherein the permanent core is permanent when placed in the human body, and the biodegradable shell biodegrades in the human body.

6. The prosthesis ofclaim 1 wherein the permanent core is cylindrical and the biodegradable shell is an annular cylinder.

7. The prosthesis ofclaim 6 wherein the permanent core and the biodegradable shell are coaxial.

8. The prosthesis ofclaim 1 wherein the biodegradable shell has a greater elasticity than the permanent core.

9. The prosthesis ofclaim 1 further comprising:

a biodegradable composite yarn graft material comprising the biodegradable composite yarn; and

at least one stent-ring coupled to the biodegradable composite yarn graft material.

10. The prosthesis ofclaim 1 further comprising a graft material comprising a proximal seal zone, an exclusion zone, and a distal seal zone, wherein only the proximal seal zone and the distal seal zone comprises the biodegradable composite yarn.

11. The prosthesis ofclaim 1 wherein the exclusion zone consists of a permanent material.

12. An assembly comprising:

a vessel comprising a vessel wall;

a prosthesis in contact with the vessel wall, the prosthesis comprising:

a permanent core; and

a biodegradable shell.

13. The assembly ofclaim 12 wherein the prosthesis further comprises a biodegradable composite yarn comprising the permanent core and the biodegradable shell.

14. The assembly ofclaim 12 wherein over time the biodegradable shell biodegrades.

15. The assembly ofclaim 12 wherein the vessel comprises a dissection, the prosthesis being deployed over a dissection opening of the dissection.

16. The assembly ofclaim 12 wherein the vessel comprises an aneurysm, the prosthesis being deployed to exclude the aneurysm.

17. A method comprising:

forming a biodegradable composite yarn comprising a permanent core and a biodegradable shell; and

combining the biodegradable composite yarn to form a prosthesis comprising a biodegradable composite graft material.

18. The method ofclaim 17 further comprising:

deploying the prosthesis within a vessel, wherein upon initial deployment, the biodegradable composite graft material is impermeable to fluid.

19. The method ofclaim 18 wherein over time, the biodegradable shell biodegrades creating openings in the biodegradable composite graft material.

20. The method ofclaim 19 wherein tissue from the vessel fills the openings and encases the permanent core.

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