Covers with Selective Bonding
Stent-grafts and scaffold-based medical applications are used to treat a variety of medical conditions in cardiology, gastroenterology, neurology, urology, pulmonology, etc. Many Medical devices require covering for a variety of clinical outcomes, such as; sealing, leak prevention, tissue ingrowth or tissue restriction, etc. At Medibrane, we use polymers that are clinically investigated and have a long history of use in the medical device industry, such as; medical grade Silicone, Dacron, ePTFE, and a variety of thermoplastic Polyurethanes. The selected polymer and covering technology influence the cover parameters and determine the thickness, radial strength, crimping profile, as well as porous or non-porous nature of the cover.
Biocompatible Polymers Used for Stent Covering
Biocompatibility is defined as “the ability of a material to perform with an appropriate host response in a specific application” (Williams, 2008). However, biocompatibility is determined according to the device parameters, not only according to the material, and thus, the implant site, duration, and intended use should be carefully considered.
Medibrane’s Unique Adhesion Platform
Medibrane’s engineers improve adhesion forces as the first step for all covering options since the metal scaffold and polymeric cover are two materials that do not normally bond together. The first step is surface activation; changing the chemistry of the metal surface to provide better mechanical attachment between the cover and the stent. The second step is encapsulation coating; the polymeric coating encircles the stent’s struts to form a closed loop. The polymer cover is then implemented onto this closed-loop, or what we call a thin tie layer. This generates a very strong connection between the cover and the encapsulated polymer.
Lamination Covering Technology
Polymers can be laminated onto the inner diameter of the stent, the outer diameter, or on both inner and outer diameter. Lamination technology uses temperature and pressure to connect the cover to the metal frame. Lamination of 2 layers generates a “sandwich-like” cover, as the 2 layers adhere with a strong connection in the overlap area. This technique is suitable in situations when an increase in thickness and crimping profile does not pose a problem. Medibrane’s Innovative sutureless lamination technology overcomes the challenge of covering with only 1 layer of polymer without sutures while maintaining strong adhesion forces between the polymer cover and the metal stent. The ability to maintain strong adhesion forces with only 1-layer of cover is achieved due to Medibarne’s unique adhesion platform. For this reason, it can be used in cases where the cover thickness and crimping profile are crucial. Another advantage of this technique is the ability to generate a cover with selective bonding.
Selective Bonding Cover
Years back, the medical industry has shifted to the use of minimally invasive procedures using self-expandable and balloon-expandable stents. This shift caused a change in the polymers and technologies used for stent covering. This change is due to the fact that the stent grafts have to be crimped and inserted into narrow delivery systems, and so, properties such as crimping force and loading force become essential. This trend increases the use of polymers and technologies enabling low cover thickness and a low crimping profile.
Cover thickness reduction can be achieved by covering the stent with only 1-layer of polymer, on the inner diameter or outer diameter. Another option is choosing materials that will allow the generation of ultra-thin covers as Polyurethane. Selectively bonding is an innovative technique developed by our engineering team; it allows them to obtain a reduction of the crimping profile and cover thickness. Using a selective bonding, the membrane is attached to the stent only at specific regions. This leads to a reduction of the radial force, and thus, the reduction of the crimping profile.
- Polymer Lamination