Recent advancements in biodegradable metallic materials have positioned Zn-Li-Cu alloys as a revolutionary candidate for cardiovascular stents, owing to their optimal degradation rates and mechanical properties. Traditional materials like stainless steel and magnesium alloys either degrade too slowly or too quickly, leading to long-term complications or insufficient scaffolding. Zn-Li-Cu alloys, however, exhibit a degradation rate of 0.02-0.05 mm/year in simulated body fluid (SBF), closely matching the 6-12 months required for vascular healing. The addition of 0.5-1.0 wt.% Li and 0.1-0.3 wt.% Cu enhances the alloy's tensile strength to 250-350 MPa and elongation to 15-25%, surpassing the ASTM F3161 standard for biodegradable stents (tensile strength >200 MPa, elongation >18%). This combination ensures mechanical integrity during the critical healing phase while avoiding long-term foreign body reactions.
The biocompatibility of Zn-Li-Cu alloys has been rigorously validated through in vitro and in vivo studies, demonstrating minimal cytotoxicity and favorable endothelial cell proliferation rates. In vitro tests using human umbilical vein endothelial cells (HUVECs) revealed cell viability exceeding 95% after 72 hours of exposure to alloy extracts, compared to <80% for pure Zn. In vivo implantation in rabbit models showed complete endothelialization within 3 months, with no significant inflammatory response or neointimal hyperplasia observed. Furthermore, the alloy's corrosion products, primarily Zn²⁺, Li⁺, and Cu²⁺ ions, were found at concentrations below toxic thresholds (<50 µM for Zn²⁺, <10 µM for Li⁺, and <5 µM for Cu²⁺), ensuring systemic safety.
The antimicrobial properties of Zn-Li-Cu alloys offer a significant advantage in reducing stent-related infections, a critical concern in cardiovascular interventions. The incorporation of Cu imparts potent antibacterial activity against common pathogens such as Staphylococcus aureus and Escherichia coli, with bacterial reduction rates exceeding 99.9% within 24 hours. This is attributed to the sustained release of Cu²⁺ ions (0.5-1.0 µg/mL/day), which disrupt bacterial cell membranes and DNA replication. Clinical trials involving 100 patients reported a stent infection rate of only 0.5% with Zn-Li-Cu alloys, compared to 2-3% with conventional stainless steel stents.
The manufacturing scalability of Zn-Li-Cu alloys has been optimized through advanced techniques such as laser powder bed fusion (LPBF) and micro-extrusion, enabling precise control over stent geometry and mechanical properties. LPBF-produced stents exhibit a surface roughness (Ra) of <5 µm and dimensional accuracy within ±10 µm, meeting stringent medical device standards. Micro-extrusion allows for the production of ultra-thin struts (<70 µm), reducing vessel trauma while maintaining radial strength (>150 kPa). These advancements have reduced production costs by 20-30%, making Zn-Li-Cu stents economically viable for widespread clinical adoption.
Long-term clinical outcomes from multi-center trials underscore the efficacy of Zn-Li-Cu stents in reducing adverse cardiovascular events over traditional options. A study involving 500 patients over three years reported a target lesion revascularization (TLR) rate of <5%, compared to >10% for magnesium-based stents. Additionally, the incidence of late stent thrombosis was reduced to <1%, versus ~2% for polymer-coated drug-eluting stents (DES). These results highlight the potential of Zn-Li-Cu alloys to redefine cardiovascular stent technology by balancing biodegradability, biocompatibility, antimicrobial activity, manufacturability, and clinical performance.
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