METHODS OF CONDITIONING SHEET BIOPROSTHETIC TISSUE

• US 20130116676A1
• Filed: 09/17/2012
• Published: 05/09/2013
• Est. Priority Date: 03/23/2010
• Status: Active Grant

• Current Assignee: Edwards Lifesciences Corporation
• Original Assignee: Edwards Lifesciences Corporation
• Inventors: Tian, Bin, Schneider, Ralph, Dove, Jeffrey S., Cohen, Jeff, Jankovic, Ivan, Migliazza, John F., Wright, Gregory A., Young, James, Campbell, Louis A.
• Granted Patent: US 9,498,287 B2
• Time in Patent Office: Days
• US Class Current: 606/14
• CPC Class Codes: A61B 18/20 using laser
• CPC Class Codes: A61F 2/02 Prostheses implantable into the body closure means for urethra or rectum or for artificial body openings therefor A61F2/0004
• CPC Class Codes: A61F 2/24 Heart valves ; Vascular valves, e.g. venous valves; Heart implants, e.g. passive devices for improving the function of the native valve or the heart muscle; Transmyocardial revascularisation [TMR] devices; Valves implantable in the body
• CPC Class Codes: A61F 2/2409 Support rings therefor, e.g. for connecting valves to tissue annuloplasty rings A61F2/2442
• CPC Class Codes: A61F 2/2415 Manufacturing methods
• CPC Class Codes: A61F 2/2418 Scaffolds therefor, e.g. support stents
• CPC Class Codes: A61F 2002/30324 differing in thickness
• CPC Class Codes: A61F 2250/0036 differing in thickness
• CPC Class Codes: A61L 2300/60 characterised by a special physical form
• CPC Class Codes: A61L 2430/20 for reconstruction of the heart, e.g. heart valves
• CPC Class Codes: A61L 27/3604 characterised by the human or animal origin of the biological material, e.g. hair, fascia, fish scales, silk, shellac, pericardium, pleura, renal tissue, amniotic membrane, parenchymal tissue, fetal tissue, muscle tissue, fat tissue, enamel
• CPC Class Codes: A61L 27/3625 Vascular tissue, e.g. heart valves
• CPC Class Codes: A61L 27/3691 characterised by physical conditions of the treatment, e.g. applying a compressive force to the composition, pressure cycles, ultrasonic/sonication or microwave treatment, lyophilisation
• CPC Class Codes: A61L 27/507 for artificial blood vessels apparatus for applying cells on a blood vessel prosthesis A61F2/062
• CPC Class Codes: B65B 55/18 by liquids or gases B65B55/14 takes precedence
• CPC Class Codes: B65B 63/02 for compressing or compacting articles or materials prior to wrapping or insertion in containers or receptacles

Abstract

Methods for the conditioning of bioprosthetic material employ bovine pericardial membrane. A laser directed at the fibrous surface of the membrane and moved relative thereto reduces the thickness of the membrane to a specific uniform thickness and smoothes the surface. The wavelength, power and pulse rate of the laser are selected which will smooth the fibrous surface as well as ablate the surface to the appropriate thickness. Alternatively, a dermatome is used to remove a layer of material from the fibrous surface of the membrane. Thinning may also employ compression. Stepwise compression with cross-linking to stabilize the membrane is used to avoid damaging the membrane through inelastic compression. Rather, the membrane is bound in the elastic compressed state through addition cross-linking. The foregoing several thinning techniques may be employed together to achieve strong thin membranes.

Claims

1. A method for preparing bioprosthetic tissue membrane material, comprising:

selecting a tissue membrane having a fibrous side and a smooth side and a non-uniform thickness;

cross-linking the selected membrane;

removing material from the fibrous side of the cross-linked membrane to smooth the fibrous side; and

subjecting the cross-linked and smoothed membrane to a glycerin-based drying process.

2. The method of claim 1, wherein the tissue membrane is mammalian pericardial membrane.

3. The method of claim 1, further including, after the glycerin-based drying process, treating with a capping agent and a reducing agent.

4. The method of claim 1, further including, after the glycerin-based drying process, a second step of removing material from the fibrous side of the treated membrane to obtain regions of different thickness.

5. The method of claim 4, wherein the second step of removing material is accomplished by ablating with a laser.

6. The method of claim 1, wherein the step of removing material is accomplished by shearing or milling with a mechanical device.

7. The method of claim 1, wherein the step of removing material is accomplished by ablating with a very short pulse duration laser.

8. The method of claim 1, wherein the tissue membrane is bovine pericardial membrane, and the membrane before material removal has a thickness of 250-700 microns, and the step of removing reduces the thickness of at least a portion of the membrane to less than 250 microns.

9. A method for fabricating a heart valve leaflet, comprising:

selecting a bioprosthetic tissue membrane having opposite sides and a non-uniform thickness;

cross-linking the selected membrane;

removing material from at least one of the sides of the cross-linked membrane to render the thickness more uniform;

subjecting the cross-linked and more uniform membrane to a glycerin-based drying process; and

forming a heart valve leaflet from the membrane after the glycerin-based drying process to have an arcuate cusp edge and a free edge opposite the cusp edge, both of which surround a central region.

10. The method of claim 9, further including, after the glycerin-based drying process, a second step of removing material from one of the sides of the treated membrane to obtain regions of different thickness.

11. The method of claim 10, wherein the second step of removing material reduces the thickness in a central region of the leaflet to a greater degree than at the cusp edge.

12. The method of claim 11, wherein the tissue membrane is bovine pericardial membrane, and after the second step of removing material the thickness at the cusp edge is between 250-700 microns, and the thickness in the central region is less than 250 microns.

13. The method of claim 10, wherein the second step of removing material also reduces the thickness in the central region to a greater degree than at the free edge.

14. The method of claim 10, wherein the second step of removing material reduces the thickness in the central region between generally uniform width strips that extend radially from the center of the free edge to the cusp edge.

15. The method of claim 10, wherein transitions between the regions of different thickness are gradual.

16. The method of claim 10, wherein the second step of removing material is accomplished by ablating the conditioned material with a very short pulse duration laser.

17. The method of claim 9, further including treating the cross-linked membrane with a capping agent and a reducing agent.

18. The method of claim 9, wherein the step of removing material is accomplished by shearing or milling with a mechanical device.

19. The method of claim 9, wherein the tissue membrane has a fibrous side and a smooth side, and the material removal is done on the fibrous side to smooth the fibrous side.

20. A method for fabricating a heart valve with bioprosthetic tissue leaflets, comprising:

selecting a bioprosthetic tissue membrane having a fibrous side and a smooth side and a non-uniform thickness;

cross-linking the membrane;

removing material from the fibrous side of the membrane to smooth the fibrous side;

subjecting the cross-linked and smoothed membrane to a glycerin-based drying process;

forming a heart valve leaflet from the smoothed membrane after the glycerin-based drying process to have a peripheral edge region, a free edge opposite the peripheral edge region, and a central region surrounded by the peripheral edge region and free edge; and

attaching a plurality of the heart valve leaflets to a structural stent by connecting the peripheral edge regions of each leaflet to the structural stent.

21. The method of claim 20, wherein the step of removing material from the fibrous side of each heart valve leaflet reduces the thickness of at least a portion of the central region relative to the peripheral edge region.

22. The method of claim 21, wherein the peripheral edge region of each leaflet defines an arcuate cusp edge opposite the free edge, and a portion of the peripheral edge region that is thicker than the adjacent reduced thickness central region extends in a generally uniform width strip along the cusp edge.

23. The method of claim 20, wherein the structural stent is configured to be radially collapsible to a collapsed or crimped state for introduction into the body on a delivery catheter and radially expandable to an expanded state for implanting the valve at a desired location in the body.

24. The method of claim 20, wherein the step of removing material from the fibrous side of each heart valve leaflet reduces the thickness of at least a portion of the central region relative to the peripheral edge region, wherein the peripheral edge region of each leaflet defines an arcuate cusp edge opposite the free edge, wherein the heart valve includes three of the leaflets connected to each other at adjacent cusp edges in a tricuspid arrangement to form a leaflet assembly, and wherein the portions of the peripheral edge regions in each leaflet that are thicker than the adjacent reduced thickness central regions collectively define a ribbon that extends along a lower edge portion of the inside surface of the leaflet assembly and connects to the structural stent with sutures.

25. The method of claim 20, wherein the step of removing material from the fibrous side of each heart valve leaflet is done prior to the step of cross-linking.

26. The method of claim 20, wherein the step of removing material is accomplished by shearing or milling with a mechanical device.