Stent covers can be made porous or impermeable and the porosity may vary depending on the medical device’s requirements based on its function, target area, tissue ingrowth, etc. A key benefit of porous covers is that it allows communication between the blood and the blood vessel wall, and it enables tissue ingrowth, and so, prevent stent migration from the target area. ePTFE and a variety of fabrics such as Dacron, have such a porous structure, and are used for covering medical devices such as structural heart device or stent grafts for blood vessels larger than 10mm.
ePTFE and Fabric Covering Technologies
ePTFE and fabrics are commonly used in the medical device industry for covering of a variety of medical devices such as stent grafts, heart occluders, heart valves, left atrial appendage devices, etc. In order to reduce the cover thickness and crimping profile most of these applications are covered with only 1-layer, either on the inner diameter or on the outer diameter of the stent, leaving bare metal on the other side. For this reason, these polymers are usually sutured to the stent-based device using a manual, time consuming, and non-repetitive procedure. Another disadvantage of this technique lies in the sutures themselves that increase the cover thickness in the sutured region and could lead to an increased crimping profile compared to a sutureless 1-layer cover.
Medical device applications can also be covered with ePTFE or fabric using lamination technology. Lamination technology uses temperature and pressure to connect the cover to the metal stent. In most cases, these stents will be covered with 2 layers to achieve good adhesion between the metal stent and the polymer cover. Lamination with only 1-layer without any surface activation of the metal stent may lead to delamination with time. Lamination of 2 layers generates a “sandwich-like” cover as the 2 layers adhere with a strong connection in the overlap area. Another form of 2-layer lamination is the sintering process in which 2 layers of ePTFE sleeves are sintered onto each other and are then adhered to the metal stent. This process requires higher temperatures compared to the usual lamination process, up to 400⁰C. The effect on the thermal properties on the nitinol stent should be carefully considered before using this process. The 2-layer lamination techniques disadvantages are higher cover thickness, and thus, high crimping profile due to the 2 cover layers required. For most self-expandable or balloon expandable stents, thickness and crimping profile are very important issues to be considered.
Medibrane’s Advanced Sutureless Lamination Technology
Medibrane’s engineers overcame this challenge by developing the advanced 1-layer sutureless lamination technology. This innovative technology is based on Medibrane’s unique development, the adhesion platform.
Medibrane’s Adhesion platform was developed to improve adhesion between the metal stent and the polymeric cover, two materials that do not normally bond together. The adhesion platform is composed of two stages: surface activation and encapsulation coating. The first stage of the platform is activation of the metal scaffold’s surface, preparing it for bonding. The second phase of the platform is generating an encapsulation coating that fully encircles the stent’s metal struts with a polymer to form a closed loop that generates a very strong attachment between the polymer and the metal stent. Another advantage of using this platform is that the stent’s struts are fully coated, even when the polymeric cover is attached only to the inner diameter or outer diameter of the stent.
After using the adhesion platform, the cover is implemented onto the stent by lamination. The strong bond generated enables the use of only 1-layer of cover while maintaining strong adhesion, thereby reducing the cover thickness and the crimping profile. Another advantage of this technology is that covering stents using sutureless lamination rather than suturing enables the usage of an automated, repetitive, cost-effective and scalable process.
The sutureless lamination technology revolutionized the medical covering industry by enabling lamination of only 1-layer, with no sutures, while maintaining good adhesion.
Sutureless Lamination Technology Advantages:
Low cover thickness
Low crimping profile
Low friction forces during delivery
Automated and scalable Process
Fast manufacturing time
Sutureless Lamination Is Suitable For:
Abdominal aortic aneurysm deevices
Left atrial appendage implants
Acute heart failure device