Lithium-Induced Optimization Mechanism for an Ultrathin-Strut Biodegradable Zn-Based Vascular Scaffold.

To reduce incidences of in-stent restenosis and thrombosis, the use of a thinner-strut stent has been clinically proven to be effective. Therefore, the contemporary trend is toward the use of ultrathin-strut (≤70 µm) designs for durable stents. However, stents made from biodegradable platforms have failed to achieve intergenerational breakthroughs due to their excessively thick struts. Here, microalloying is used to create an ultrathin-strut (65 µm) zinc (Zn) scaffold with modified biodegradation behavior and improved biofunction, by adding lithium (Li). The scaffold backbone consists of an ultrafine-grained Zn matrix (average grain diameter 2.28 µm) with uniformly distributed nanoscale Li-containing phases. Grain refinement and precipitation strengthening enable it to achieve twice the radial strength with only 40% of the strut thickness of the pure Zn scaffold. Adding Li alters the thermodynamic formation pathways of products during scaffold biodegradation, creating an alkaline microenvironment. Li2 CO3  may actively stabilize this microenvironment due to its higher solubility and better buffering capability than Zn products. The co-release of ionic zinc and lithium enhances the beneficial differential effects on activities of endothelial cells and smooth muscle cells, resulting in good endothelialization and limited intimal hyperplasia in porcine coronary arteries. The findings here may break the predicament of the next-generation biodegradable scaffolds.