Stent fabrication via tubular casting processes

• US 10,646,359 B2
• Filed: 05/21/2012
• Issued: 05/12/2020
• Est. Priority Date: 06/20/2008
• Status: Active Grant

• Current Assignee: Razmodics, LLC
• Original Assignee: Amaranth Medical Pte.
• Inventors: Ramzipoor, Kamal, Chia, Alfred N. K., Wang, Liwei
• Primary Examiner(s): Eastwood, David C
• Application Number:
  US13/476,853
• Publication Number:
  US 20120232643A1
• Time in Patent Office: 2,913 Days
• CPC Class Codes: A61F 2/07 Stent-grafts
• 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 2/82 Devices providing patency to, or preventing collapsing of, tubular structures of the body, e.g. stents stent-grafts for tubular structures of the body other than blood vessels A61F2/04; stent-grafts for blood vessels A61F2/07; instruments specially adapted for placement or removal of stents or stent-grafts A61F2/95; for closing wounds, or holding wounds closed A61B17/04 - A61B17/115; dilators A61M29/00
• CPC Class Codes: A61F 2002/30062 (bio)absorbable, biodegradable, bioerodable, (bio)resorbable, resorptive
• CPC Class Codes: A61F 2002/30535 Special structural features of bone or joint prostheses not otherwise provided for
• CPC Class Codes: A61F 2210/0004 bioabsorbable
• CPC Class Codes: A61F 2210/0019 operated at only one temperature whilst inside or touching the human body, e.g. constrained in a non-operative shape during surgery, another temperature only occurring before the operation
• CPC Class Codes: A61F 2240/004 Using a positive or negative model, e.g. moulds
• CPC Class Codes: A61L 31/04 Macromolecular materials
• CPC Class Codes: A61L 31/06 obtained otherwise than by reactions only involving carbon-to-carbon unsaturated bonds A61L31/041 takes precedence
• CPC Class Codes: A61L 31/14 Materials characterised by their function or physical properties , e.g. injectable or lubricating compositions, shape-memory materials, surface modified materials
• CPC Class Codes: A61L 31/148 Materials at least partially resorbable by the body
• CPC Class Codes: A61L 31/16 Biologically active materials, e.g. therapeutic substances A61L31/047 takes precedence
• CPC Class Codes: B29C 41/003 characterised by the choice of material
• CPC Class Codes: B29C 41/14 Dipping a core B29C41/10 takes precedence
• CPC Class Codes: B29C 49/00 Blow-moulding, i.e. blowing a preform or parison to a desired shape within a mould; Apparatus therefor
• CPC Class Codes: B29K 2105/0035 Medical or pharmaceutical agents
• CPC Class Codes: B29K 2995/0056 Biocompatible, e.g. biopolymers or bioelastomers
• CPC Class Codes: B29L 2031/7532 Artificial members, protheses

Abstract

Tubular casting processes, such as dip-coating, may be used to form substrates from polymeric solutions which may be used to fabricate implantable devices such as stents. The polymeric substrates may have multiple layers which retain the inherent properties of their starting materials and which are sufficiently ductile to prevent brittle fracture. Parameters such as the number of times the mandrel is immersed, the duration of time of each immersion within the solution, as well as the delay time between each immersion or the drying or curing time between dips and withdrawal rates of the mandrel from the solution may each be controlled to result in the desired mechanical characteristics. Additional post-processing may also be utilized to further increase strength of the substrate or to alter its shape.

Claims

1. A polymeric stent, comprising:

an implantable stent scaffold formed from a polymeric substrate, wherein the polymeric substrate is formed from repeatedly immersing a mandrel in a polymeric solution comprising a bioabsorbable polymer and a solvent,

wherein the bioabsorbable polymer is a polylactide having a molecular weight greater than 9.80×

10⁵ g/mol,

wherein the polymeric substrate is a tubular member formed as multiple dip-coated layers of the polymeric solution on the mandrel, wherein the multiple dip-coated layers comprise a first dip-coated layer formed by dipping the mandrel in a first dipping direction in the polymeric solution such that the polylactide is molecularly oriented in a first linearly oriented direction and a second dip-coated layer formed by dipping the mandrel in a second dipping direction opposite the first dipping direction in the polymeric solution such that the polylactide is molecularly oriented in a second linearly oriented direction opposite the first linearly oriented direction, and

wherein the implantable stent scaffold is formed by further processing the tubular member, and wherein a degree of crystallinity of the first dip-coated layer and the second dip-coated layer is between about 20% and 40%.

2. The stent of claim 1 wherein the stent is adapted to exhibit a percent reduction in diameter of between 5% to 70% without fracture formation when placed under a compressive load.

3. The stent of claim 1 wherein the stent is adapted to expand in diameter between 5% to 70% without fracture formation.

4. The stent of claim 1 wherein the stent is adapted to curve up to 180°

about a 1 cm curvature radius without fracture formation.

5. The stent of claim 1 wherein the stent is adapted to exhibit a percent reduction in axial length of between 10% to 30% without fracture formation when placed under an axial load.

6. The stent of claim 1, wherein the implantable stent scaffold is formed by expanding the polymeric substrate to the first expanded diameter at a temperature above the glass transition temperature of the polymeric substrate and subsequently cooling the expanded polymeric substrate below the glass transition temperature.

7. The stent of claim 1, wherein the second dip-coated layer is external to the first dip-coated layer.

8. The stent of claim 1, wherein the polylactide of the first dip-coated layer is poly-L-lactide (PLLA).

9. The stent of claim 1, wherein the solvent from the polymeric solution is removed by drying and heating the polymeric substrate at or above a glass transition temperature of the polylactide.