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Strut Thickness and Species-Specific Healing Are Key Considerations in Developing Zinc-Based Biodegradable Arterial
Lea M Morath1, Shebeer A Rahim2,3, Cole A Baker4
1Department of Biomedical Engineering, Michigan Technological University, Houghton, Michigan, USA.
Summary
Refined zinc-based alloys with smaller wire diameters show promise for biodegradable vascular stents, exhibiting low thrombogenicity and favorable biocompatibility in rats, but caution is advised for mouse models.
Area of Science:
- Biomaterials Science
- Vascular Engineering
- Materials Science
Background:
- Biodegradable stents are crucial for temporary vascular support, aiming to reduce complications like thrombosis and restenosis.
- Zinc-based alloys are emerging as promising candidates for biodegradable stents due to their potential biocompatibility and degradation profiles.
Purpose of the Study:
- To evaluate the microstructure, mechanical properties, thrombogenicity, and in vivo biocompatibility of three novel zinc-based alloys (AMZ, ACMZ, CMM) with reduced wire diameters (0.12 mm).
- To compare the performance of these alloys against existing materials and assess the impact of reduced strut dimensions on biological response.
Main Methods:
- Alloys were processed via cold drawing and heat treatment to achieve ultra-fine-grained structures.
- Microstructure and elemental composition were analyzed using Energy Dispersive Spectroscopy (EDS) and X-ray Diffraction (XRD).
- Mechanical properties, in vitro hemocompatibility (thrombogenicity assays), ex vivo blood-material interactions, and in vivo biocompatibility (implantation in mice and rats) were assessed.
Main Results:
- Ultra-fine-grained structures (<1 μm) with strengthening intermetallic phases were achieved, and heat treatment improved ductility without compromising strength.
- In vitro and ex vivo tests indicated low thrombogenicity, with reduced fibrin and FXIIa generation compared to controls.
- In vivo studies revealed species-specific immune responses: significant inflammation in mice, but mild inflammation and controlled healing in rats. Smaller 0.12 mm wires showed less neointimal growth than 0.25 mm wires in rats.
Conclusions:
- Refined zinc-based alloys with reduced wire diameters demonstrate potential for next-generation biodegradable stents, offering good hemocompatibility and favorable tissue response in rat models.
- The observed species-specific inflammatory differences highlight the importance of careful model selection in preclinical testing of biomaterials.
