Bioresorbable endoluminal prosthesis for medium and large vessels
Inventors
Bocks, Martin • Drelich, Jaroslaw • Goldman, Jeremy • Mostaed, Ehsan
Assignees
Case Western Reserve University • Michigan Technological University
Publication Number
US-12337081-B2
Publication Date
2025-06-24
Expiration Date
2041-08-14
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Abstract
An endoluminal prosthesis includes an implantable scaffold and/or stent substrate which is convertible from a compressed first geometric shape to a radially dilated dimensionally stable second tubular second geometric shape, the scaffold and/or stent substrate comprising a bioresorbable zinc alloy, the zinc alloy including at least at least four alloying elements selected from the group consisting of silver (Ag) in an amount of about 1.0 wt. % to about 6.0 wt. %, manganese (Mn) in an amount of about 0.1 wt. to about 2.0 wt. %, zirconium (Zr) in an amount of about 0.05 wt. % to about 1.0 wt. %, copper (Cu) in an amount of about 0.5 wt. % to about 1.2 wt. %, and optionally titanium (Ti) in an amount of 0 to about 0.4 wt. %, with the balance of the alloy being zinc and incidental impurities.
Core Innovation
The invention relates to an endoluminal prosthesis that includes an implantable scaffold and/or stent substrate, which can be converted from a compressed first tubular geometric shape to a radially expanded, dimensionally stable second tubular geometric shape. The scaffold and/or stent substrate is made from a bioresorbable zinc alloy containing at least four alloying elements selected from silver, manganese, zirconium, copper, and optionally titanium, with the balance being zinc and incidental impurities. This zinc alloy is engineered to provide optimal tensile strength while maintaining ductility and elongation to allow the stent to be radially expanded from a small sheath-compatible size to an outer diameter of about 4 mm to about 12 mm.
The background highlights the problem of current bare metal stents (BMS) causing growth restriction in pediatric patients as well as ongoing complications in adults such as late thrombus formation and restenosis due to permanent stent materials. Previously developed zinc alloys, such as those with magnesium or aluminum, have shown inadequate mechanical properties like decreased elongation and low strength, making them unsuitable for large-diameter, bioresorbable vascular stents, especially for pediatric and certain adult conditions.
The core innovation overcomes these challenges by providing a bioresorbable zinc alloy with enhanced mechanical properties, such as ultimate tensile strength greater than about 250 MPa and elongation to failure above 25%. The stent substrate maintains ductility and vessel patency for at least 6 months—critical for both pediatric growth and adult vascular healing. The invention also includes manufacturing processes to achieve a uniform microstructure with finely distributed intermetallic particles and optional coatings to tailor degradation or release therapeutic agents.
Claims Coverage
There are two independent claims in this patent, each covering a distinct inventive feature related to bioresorbable endoluminal prostheses and stent structures.
Endoluminal prosthesis comprising a stent or scaffold substrate formed from a specific bioresorbable zinc alloy
The inventive feature is a prosthesis with an implantable stent and/or scaffold substrate that is convertible between compressed and radially expanded forms. The substrate is made of a bioresorbable zinc alloy including at least four alloying elements chosen from: - Silver (Ag) in an amount of about 1.0 wt.% to about 6.0 wt.% - Manganese (Mn) in an amount of about 0.1 wt.% to about 2.0 wt.% - Zirconium (Zr) in an amount of about 0.05 wt.% to about 1.0 wt.% - Copper (Cu) in an amount of about 0.5 wt.% to about 1.2 wt.% - Titanium (Ti) in an amount of 0 to about 0.4 wt.% (optional) The remainder of the alloy is zinc and incidental impurities (less than about 0.01 wt.% each). The zinc alloy has a substantially uniform microstructure with Zn grain size of about 0.1 μm to about 10 μm and a plurality of uniformly distributed intermetallic particles at the grain boundaries.
Tubular stent or scaffold framework made of the specified bioresorbable zinc alloy
This inventive feature is a scaffold and/or stent comprising a tubular framework of interconnected stent struts fabricated from a bioresorbable zinc alloy. The framework is convertible from a compressed to a radially expanded, dimensionally stable tubular geometric shape. The bioresorbable zinc alloy includes: - At least four alloying elements selected from the group consisting of: - Silver (Ag) about 1.0 wt.% to about 6.0 wt.% - Manganese (Mn) about 0.1 wt.% to about 2.0 wt.% - Zirconium (Zr) about 0.05 wt.% to about 1.0 wt.% - Copper (Cu) about 0.5 wt.% to about 1.2 wt.% - Optional Titanium (Ti) about 0 to about 0.4 wt.% - The balance being zinc and incidental impurities below about 0.01 wt.% The alloy is characterized by a substantially uniform microstructure with Zn grain size about 0.1 μm to about 10 μm and a plurality of uniformly distributed intermetallic particles at the grain boundaries.
The claims primarily cover an endoluminal prosthesis and stent scaffolds made from a specific multi-element bioresorbable zinc alloy with unique microstructural characteristics that enable conversion between compressed and radially expanded tubular forms.
Stated Advantages
The bioresorbable zinc alloy provides optimal tensile strength while maintaining ductility and elongation, enabling the stent to expand from a small delivery sheath to a larger diameter suitable for medium and large vessels.
The stent can be delivered through small introducer sheaths, making it usable even for infants and small children.
The alloy enables therapeutic maintenance of vessel patency at the expanded target size and maintains ductility after exposure to vascular pulsatility and during degradation.
Radial strength and mechanical characteristics allow treatment of lesions requiring larger diameter stents, expanding applications beyond coronary arteries to pediatric and adult conditions.
The alloy's degradation products, such as Zn2+ and Cu2+, have anti-inflammatory and NIH inhibitory effects, reducing platelet activation and smooth muscle cell response without the need for antiproliferative agents.
The stent maintains necessary support for at least 6 months to allow vessel healing or growth, then is gradually resorbed to avoid long-term complications associated with permanent stents.
Manufacturing processes allow formation of thin-walled tubes without mechanical cracks, enabling a small crossing profile.
Optional coatings can further tailor degradation rates and provide controlled delivery of therapeutic agents.
Documented Applications
Infant/pediatric pulmonary artery stenosis (about 4 mm to about 12 mm diameter).
Infant/pediatric aortic coarctation (about 4 mm to about 12 mm diameter).
Neonatal patent ductus arteriosus stenting (about 6 mm to about 8 mm diameter).
Infant right ventricular outflow tract (RVOT) stenting (about 4 mm to about 8 mm diameter).
Pulmonary vein stenosis/occlusion (about 4 mm to about 10 mm diameter).
Adult peripheral artery disease (about 4 mm to about 12 mm diameter).
Adult coronary artery disease (about 4 mm to about 5 mm diameter).
Adult carotid artery disease (about 6 mm to about 10 mm diameter).
Adult renal artery stenosis (about 4 mm to about 10 mm diameter).
Adult and children venous and arterial thrombosis recanalization (about 4 mm to about 12 mm diameter).
Any type of bodily lumen including coronary artery, superficial femoral artery, popliteal artery, neural vessels, and the sinuses.
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