Stent-grafts and scaffold-based medical devices treat various conditions in cardiology, gastroenterology, neurology, urology, pulmonology, and more. These devices often require covers for multiple clinical outcomes, such as sealing, leak prevention, tissue ingrowth, or tissue restriction. At Medibrane, we use clinically investigated polymers with a long history in the medical device industry, including medical-grade silicone, Dacron, ePTFE, and thermoplastic polyurethanes. The selected polymer and covering technology influence critical cover parameters, such as thickness, radial strength, crimping profile, and whether the cover is porous or non-porous.

Biocompatible Polymers Used for Stent Covering

Biocompatibility is the ability of a material to perform with an appropriate host response in a specific application (Williams, 2008). However, biocompatibility depends not only on the material but also on the device parameters. Therefore, the implant site, duration, and intended use must be carefully considered.

Medibrane’s Unique Adhesion Platform

Our engineers focus on improving adhesion forces as the first step for all covering options. Metal scaffolds and polymer covers typically do not bond easily, so we begin by activating the metal surface, changing its chemistry to enhance mechanical attachment between the cover and stent. The second step is encapsulation coating, where the polymeric coating wraps around the stent’s struts to form a closed loop. The polymer cover is then applied onto this loop, creating a strong connection between the cover and the encapsulated polymer.

Lamination Covering Technology

We use lamination technology to bond polymers to the inner or outer diameter of the stent, or both. By applying temperature and pressure, we connect the cover to the metal frame. Lamination of two layers generates a “sandwich-like” structure, creating a strong bond in the overlap area. This technique is suitable when increased thickness and crimping profile are not problematic. Medibrane’s innovative sutureless lamination technology addresses the challenge of covering with a single polymer layer, while maintaining strong adhesion forces between the polymer cover and the metal stent. This technology is especially useful when cover thickness and crimping profile are critical. One of its advantages is the ability to generate a cover with selective bonding.

Selective Bonding Cover

The medical industry has shifted to minimally invasive procedures using self-expandable and balloon-expandable stents. This shift has driven changes in the polymers and technologies used for stent coverings. As stent grafts must be crimped and inserted into narrow delivery systems, properties such as crimping force and loading force are essential. The trend towards minimizing cover thickness and crimping profile has increased the use of polymers and technologies that enable low cover thickness.

Reducing cover thickness can be achieved by using only one layer of polymer on the inner or outer diameter. Another option is choosing materials like polyurethane to create ultra-thin covers. Selective bonding, a technique developed by our engineering team, enables the reduction of crimping profile and cover thickness. With selective bonding, the membrane attaches to the stent only at specific regions, reducing radial force and crimping profile.

Covering Technologies:

• Polymer Lamination

Covering Materials:

• TPU
• ePTFE
• Dacron