In Vitro and in Vivo Evaluation of Multiphase Ultrahigh Ductility Mg–Li–Zn Alloys for Cardiovascular Stent Application

Abstract

Magnesium alloys have been extensively studied as a novel biodegradable metallic material for cardiovascular stent application. However, the ductility limitation of magnesium alloy has been a key issue for biodegradable stents applications. In this study, two different multiphase ultrahigh ductility Mg–Li–Zn alloys, LZ61 and LZ91, are fabricated in the form of extruded rods and evaluated both in vitro and in vivo. The microstructure, mechanical properties and in vitro degradation are evaluated as well as in vitro cytotoxicity. The in vivo degradation, tissue response, and systematic toxicity are evaluated in a mouse subcutaneous model. Measurements show that LZ61 and LZ91 exhibit more than 40% elongation at fracture without significantly compromising the strength. Both in vitro and in vivo degradation showed low degradation rates for LZ61 but high degradation rate for the LZ91 alloy. Excellent biocompatibility is observed both in vivo and in vitro for LZ61 and LZ91. In summary, this study successfully demonstrates that the ultraductility multiphase Mg–Li–Zn alloy has the potential to be used for stent applications. Compared to LZ91, the LZ61 alloy shows better balance of mechanical properties, corrosion resistance, and biocompatibility, indicating its promise for cardiovascular stent applications.

In-vivo efficacy of biodegradable ultrahigh ductility Mg-Li-Zn alloy tracheal stents for pediatric airway obstruction

“…Therefore, LZ61-KBMS were better protected under the flow environment, displaying a much slower corrosion rate. Figure 7 summarizes the corrosion rates of LZ61-KBMS alloy and AZ31 alloy under different tests based on the current study and our previous publications 31 . Since AZ31 stents were not implanted in vivo herein, no results of AZ31 in vivo stent degradation rates are plotted in Fig.…”

“…In vitro degradation of LZ61 stent in a bioreactor. We earlier published the degradation of our novel LZ61 alloy matching AZ31 under static environments 31 . However, in vivo, tracheal stents are exposed to a dynamic fluid environment with moving mucus consistently cleaning the airway.…”

“…The biomechanical performance and ability of the stent to maintain airway patency over time was well controlled by the LZ61-KBMS alloy corrosion in turn controlled by the alloy chemical composition, the surrounding electrolyte, and the prevalence of external stress. We have reported the impact of alloy chemical composition and surrounding electrolyte on Mg-Li-Zn alloy corrosion 31 . However, the impact of the flow-induced shear stress and internal stress on corrosion of the LZ61-KBMS stent was not studied.…”

“…Herein, for the first time, we demonstrate the superior response of a balloon-expandable ultra-high ductility (UHD) biodegradable magnesium tracheal stent contrasted with traditional nondegradable stents. We reported implantation success of prototype magnesium alloy stent in a rat tracheal bypass model 30 and Mg-Li-Zn multiphase UHD alloys for stent application 31 with Mg-6Li-1Zn (LZ61) demonstrating greatest clinical application potential owing to its superior mechanical properties, low degradation rate, UHD of~50% and excellent biocompatibility. Hence, the LZ61-KBMS (Kumta Bioresorbable Magnesium Stents) alloy series of tracheal stents were fabricated and tested both in vivo and in vitro.…”

Corrosion Behavior of Hydrotalcite Film on AZ31 Alloy in Simulated Body Fluid

“…The in vitro result reported by Cheng et al indicated that Mg does not present any cytotoxic effects on L929 and ECV304 cells [4]. The in vivo study also showed that Mg/Mg alloys are biocompatible [5]. (2) Good mechanical properties: Mg alloys have similar strength and elastic modulus with natural bones, and have the potential to minimize stress shielding [6,7].…”