Revolutionizing Stent Coverings: How Sutureless Lamination Outperforms Traditional ePTFE Sintering

For decades, expanded polytetrafluoroethylene (ePTFE) has been the gold standard for covering stents. Its biocompatibility and durability make it ideal for treating aneurysms, fistulas, and other vascular conditions. However, the method used to attach the ePTFE to the bare metal stent plays a critical role in the device's clinical success.

Historically, manufacturers have relied on sintering and encapsulation to secure the polymer to the metal struts. But as endovascular procedures become more complex, the limitations of these traditional methods are becoming apparent.

Enter Medibrane’s sutureless lamination, powered by the proprietary Adhera™ surface activation platform. This innovative approach is redefining what is possible in covered stent design, solving some of the most persistent engineering and clinical challenges in the field.

Here is a deep dive into how Medibrane’s sutureless lamination compares to traditional sintering and why it matters for the future of medical devices.

The Limitations of Traditional Sintering and Encapsulation

Traditional ePTFE covering relies on a process where the bare metal stent is sandwiched between two layers of ePTFE. These layers are then heated (sintered) so they bond to each other through the open cells of the stent, effectively encapsulating the metal struts.

While widely used, this method presents several significant drawbacks:

• Excessive Wall Thickness: Because the process requires both an inner and outer layer of ePTFE to encapsulate the stent, the overall profile of the device is inherently thick.

• Restricted Expansion: Sintered ePTFE is relatively rigid. The sintering process alters the material's mechanical properties, allowing for a maximum radial expansion of only 50% to 70%. This limits the stent's ability to conform to varied vessel anatomies.

• The "Void" Problem and Clinical Risks: The most critical flaw of encapsulation is the lack of a true chemical (covalent) bond between the ePTFE and the metal struts. During the harsh process of crimping and loading the stent into a delivery system, and later during natural vascular pulsation in situ, the ePTFE layers can shift slightly. This shifting creates microscopic voids or pockets near the metal struts. Blood can become trapped in these voids, leading to stagnation, thrombus formation, or excessive tissue growth (hyperplasia), ultimately increasing the risk of restenosis.

The Medibrane Difference: Adhera™ and Sutureless Lamination

Medibrane's approach fundamentally changes the physics and chemistry of stent covering. Utilizing the Adhera™ surface activation platform, Medibrane treats the metal stent to create a strong, covalent bond directly between the bare metal and the ePTFE.

Because the polymer bonds directly to the metal, there is no longer a need to "sandwich" the stent.

Key Advantages of Sutureless Lamination:

• Single-Sided Covering (ID or OD): The Adhera platform allows engineers to bond the ePTFE to only the internal diameter (ID) or only the external diameter (OD) of the stent.

• Ultra-Thin Profiles: By eliminating the need for a second encapsulating layer, Medibrane reduces the ePTFE wall thickness down to an incredibly low 10 to 15 microns. This ultra-low profile allows for smaller delivery systems, making navigation through tortuous anatomy much easier for physicians.

• Unmatched Radial Expansion: Sutureless lamination enables Medibrane to use highly elastic, extruded ePTFE sleeves rather than rigid sintered sheets. These extruded sleeves boast an impressive elongation capacity of over 300% (compared to the 50% to 70% limit of sintered ePTFE). This ensures excellent vessel conformability and allows for aggressive post-dilation if required.

• Elimination of Voids: Because the Adhera platform forms a robust covalent bond between the polymer and the metal, the ePTFE moves with the struts during crimping, deployment, and physiological pulsation. No shifting means no void creation. By eliminating these dead spaces, the risk of blood pooling, thrombus formation, and subsequent restenosis is drastically minimized.

Head-to-Head Comparison: Traditional Sintering vs. Medibrane Lamination

Feature / Characteristic	Traditional Sintering & Encapsulation	Medibrane Sutureless Lamination
Covering Method	Double-layer encapsulation (requires ID & OD)	Single-sided bonding (ID or OD)
Bonding Mechanism	Polymer-to-polymer (mechanical sandwich)	Direct covalent bond to metal struts
ePTFE Wall Thickness	Thicker (due to double layers)	Ultra-thin (10 – 15 microns)
Material Format	Sintered ePTFE sheets	Extruded ePTFE sleeves & Sintered ePTFE
Radial Expansion	Limited (50% – 70%)	Highly elastic (> 300%)
Void Formation Risk	High (layers shift during crimping/pulsation)	Eliminated (ePTFE moves securely with struts)
Clinical Profile	Higher risk of blood pooling and restenosis	Minimized risk due to a flush, void-free surface

References :

Li, Y., et al. (2023). Research and clinical translation of trilayer stent-graft of expanded polytetrafluoroethylene... Regenerative Biomaterials.

Sun, Y., et al. (2023). Biaxial stretching of polytetrafluoroethylene in industrial scale to fabricate medical ePTFE membrane with node-fibril microstructure. Journal of Polymer Research, 30(7), 263.

Meghezi, S., et al. (2022). Review of Polymeric Biomimetic Small-Diameter Vascular Grafts to Tackle Intimal Hyperplasia. Bioengineering, 9(7), 309.