PROCESSES FOR MAKING CRUSH RECOVERABLE POLYMER SCAFFOLDS

• US 20120073733A1
• Filed: 04/19/2011
• Published: 03/29/2012
• Est. Priority Date: 09/23/2010
• Status: Active Grant

• Current Assignee: Abbott Cardiovascular Systems Incorporated (Abbott Laboratories)
• Original Assignee: Abbott Cardiovascular Systems Incorporated (Abbott Laboratories)
• Inventors: Ngo, Michael H., Trollsas, Mikael, Papp, John E., Nguyen, Hung T., Jayasinghe, Dudley, Orr, Gregory C., Farnbach, Ron, Smith, Joshua, Xie, Yongjin, Ku, Yu-Chun
• Granted Patent: US 9,345,602 B2
• Time in Patent Office: Days
• US Class Current: 156/196
• CPC Class Codes: A61F 2/844 folded prior to deployment
• CPC Class Codes: A61F 2/89 the wire-like elements comprising two or more adjacent rings flexibly connected by separate members
• CPC Class Codes: A61F 2/915 with bands having a meander structure, adjacent bands being connected to each other
• CPC Class Codes: A61F 2/9522 Means for mounting a stent or stent-graft onto or into a placement instrument
• CPC Class Codes: A61F 2/958 Inflatable balloons for placing stents or stent-grafts
• CPC Class Codes: A61F 2002/91566 connected trough to trough
• CPC Class Codes: A61F 2002/91575 connected peak to trough
• CPC Class Codes: A61F 2002/91583 by a bridge, whereby at least one of its ends is connected along the length of a strut between two consecutive apices within a band
• CPC Class Codes: A61F 2002/9583 Means for holding the stent on the balloon, e.g. using protrusions, adhesives or an outer sleeve
• CPC Class Codes: A61F 2210/0071 thermoplastic
• CPC Class Codes: A61F 2230/0054 V-shaped
• CPC Class Codes: A61F 2230/0056 W-shaped, e.g. M-shaped, sigma-shaped
• CPC Class Codes: B23K 2103/42 Plastics B23K2103/16 takes precedence
• CPC Class Codes: B23K 2103/50 Inorganic material, e.g. metals, not provided for in B23K2103/02 – B23K2103/26
• CPC Class Codes: B23K 26/361 for deburring or mechanical trimming B23K26/351 takes precedence
• CPC Class Codes: B23K 26/362 Laser etching
• CPC Class Codes: B23K 26/402 involving non-metallic material, e.g. isolators
• CPC Class Codes: B29C 2793/0009 Cutting out
• CPC Class Codes: B29C 2949/08 Preforms made of several individual parts, e.g. by welding or gluing parts together
• CPC Class Codes: B29C 49/071 Preforms or parisons characterised by their configuration, e.g. geometry, dimensions or physical properties
• CPC Class Codes: B29C 49/08 : Biaxial stretching during blow-moulding
• CPC Class Codes: B29C 55/26 : biaxial
• CPC Class Codes: B29K 2067/046 : PLA, i.e. polylactic acid or polylactide
• CPC Class Codes: B29L 2031/753 : Medical equipment; Accessories therefor bloodbags, medical bags B29L2031/7148; artificial eyes B29L2011/0008
• CPC Class Codes: B29L 2031/7534 : Cardiovascular protheses
• CPC Class Codes: Y10T 156/1002 : with permanent bending or reshaping or surface deformation of self sustaining lamina

Abstract

Methods for making scaffolds for delivery via a balloon catheter are described. The scaffold, after being deployed by the balloon, provides a crush recovery of about 90% after the diameter of the scaffold has been pinched or crushed by 50%. The scaffold structure has patterns that include an asymmetric or symmetric closed cell, and links connecting such closed cells.

Claims

1. A method for making a medical device including a scaffold crimped to a balloon-catheter, comprising

biaxially expanding a polymer precursor to form an expanded tube;

forming a scaffold from the expanded tube using a laser;

crimping the scaffold to a balloon-catheter at a crimping temperature between about 1 to 20 degrees less than the glass transition temperature of the polymer material; and

fitting a removable sheath over the scaffold immediately following crimping to limit recoil of the crimped scaffold;

wherein the crimped scaffold, when deployed, is capable of regaining at least 90% of its diameter after being crushed to at least 75% of its diameter.

2. The method of claim 1, wherein the polymer is PLLA, and the expansion temperature is between about 110 degrees and 120 degrees Celsius so that the polymer'"'"'s crystal nucleation rate is higher than its crystal growth rate during the biaxial expansion.

3. The method of claim 1, wherein the polymer is PLLA, a polymer made from at least 80% L-lactide, a blockcopolymer with a PLLA block, or a polymer blend comprising PLLA.

4. The method of claim 1, wherein the scaffold has a wall thickness of more than 0.008 inches and a scaffold pattern is cut using a pico-second green light laser, wherein the forming step further includes making two passes with the laser based on the wall thickness of at least 0.008 inches.

5. The method of claim 1, wherein the crimping step reduces the diameter of the scaffold by a factor of 2:

1, 3;

1 or more than 3;

1.

6. The method of claim 1, wherein the sheath includes tabs to facilitate removal of the sheath from the crimped scaffold by a health professional following a packaging and sterilization of the medical device.

7. The method of claim 1, wherein the scaffold is capable of regaining more than 90% of its diameter after being crushed to about 50% of its diameter.

8. A method for making balloon-expandable medical device for being implanted in a peripheral vessel of the body, comprising:

biaxially expanding a polymer precursor to from an expanded tube; and

forming a scaffold from the expanded tube, including forming

struts joined at crowns to form rings,

a zero angle radius at the crowns, and

symmetric closed cells formed by the rings and links connecting the rings;

wherein the scaffold is capable of regaining more than 90% of its diameter after being crushed to about 50% of its diameter.

9. The method of claim 8, wherein the scaffold has a wall thickness of at least 0.011 and the forming step includes cutting a pattern using a green-light pico-second laser.

10. The method of claim 9, wherein the zero angle corresponds to the minimum angle that the laser is capable of forming.

11. The method of claim 9, the forming step further including forming radiopaque marker depots on links, the marker depots being arranged vertically to minimize the change in link length needed to accommodate depots.

12. A method for crimping a balloon-expandable medical device, comprising:

forming a pre-crimp scaffold, including the steps of

biaxially expanding a PLLA precursor to form an expanded tube including the steps of applying a pressure of about 100-120 psi, a heating nozzle rate of about 0.5-0.9 mm/sec and a temperature of about 230-240 Deg Fahrenheit, and

using a pico-second laser, forming a scaffold from the expanded tube, including forming struts forming ring structures connected by longitudinal links, where there are no more than four links connecting adjacent rings; and

crimping the scaffold to a balloon, including the steps of using a crimping temperature between about 5 to 20 degrees less than the glass transition temperature of PLLA, and maintaining an inflated delivery balloon during crimping to support the scaffold during crimping;

wherein the scaffold is capable of regaining more than 90% of its diameter after being crushed to about 50% of its diameter.

13. The method of claim 12, wherein an aspect ratio (AR) of the width to wall thickness of the strut or link is between 0.4 and 1.4.

14. The method of claim 13, wherein the AR is between 0.4 to 0.9, the scaffold wall thickness is between about 0.008 inches and 0.014 inches and the scaffold expanded diameter is between about 5 mm and 8 mm.

15. The method of claim 13, wherein the AR is between 0.8 to 1.4, the scaffold wall thickness is between 0.008 inches and 0.014 inches and the scaffold expanded diameter is between 5 mm and 8 mm.

16. The method of claim 13, wherein the struts are connected via crowns, and the crowns have a maximum crown angle between about 90 degrees and 115 degrees when the scaffold has the expanded diameter.

17. The method of claim 12, wherein a ring is reduced in diameter by articulation of struts about crowns, wherein there are no more than 9 crowns in a ring and 3 links connecting the ring to an adjacent ring;

and

wherein in an as-fabricated state;

the scaffolding has an outer diameter of 8 to 10 mm, the crown angles for rings of the scaffold are between 90 and 115 degrees, and the scaffold has a wall thickness of at least 0.008 in.

18. The method of claim 17, further including after forming a scaffold from the expanded tube or after forming the expanded tube, elevating the scaffold temperature to about 47 Deg Celsius for a period of about 1 to 3 weeks.