Department of Bioengineering, Swanson School of Engineering, University of Pittsburgh, Pittsburgh, USA.
J Biomater Appl. 2019 Mar;33(8):1080-1093. doi: 10.1177/0885328218824775. Epub 2019 Feb 4.
Airway obstruction conditions are relatively rarely observed in clinical settings but nevertheless, extremely challenging to handle, especially when observed in pediatric patients. Several surgical procedures, including tracheal resection, end-to-end tracheal anastomosis, and tracheoplasty, have been developed and practised of late, to treat airway obstruction. However, the clinical outcome is typically not satisfactory due to airway restenosis conditions that develop following surgery. Various types of stents are currently available for airway stenting ranging from non-degradable silicone tubes and bio-inert metallic stents (bare or coated with polymer matrix) to hybrid silicone tubes strengthened by metallic cores, but none of the stents provides the satisfactory long-term effectiveness. Therefore, there is a significant clinical need for a biodegradable airway stent that would maintain airway patency and totally degrade over time after meeting the desired objectives. The present study aims to investigate biodegradable magnesium-aluminum-zinc-calcium-manganese (AZXM) alloy as a potential tracheal stent. The new AZXM alloy was fabricated by partially replacing aliminum in commercial AZ31 alloy with calcium. The present study demonstrates that calcium preferentially segregates along the grain boundaries as intermetallic phases (MgCa) and is homogeneously distributed in the magnesium matrix. The extruded AZXM alloy showed less pitting, higher corrosion resistance in Hank's Balanced Salt Solution (HBSS) compared to the as-cast and solution-treated AZXM alloys and exhibited optimized mechanical properties. In vitro cytotoxicity evaluation using human trachea epithelial cells demonstrated excellent cyto-compatibility of AZXM alloys compared to pure Mg and commercial AZ31 validated by a very preliminary rabbit in vivo tracheal model study. Preliminary results show that the approach to use biodegradable AZXM alloys as a tracheal stent is indeed promising, although further alloy processing is required to improve the ductility needed followed by a more exhaustive in vivo study to demonstrate full viability for stent applications.
气道阻塞的情况在临床环境中相对较少见，但处理起来极具挑战性，尤其是在儿科患者中。为了治疗气道阻塞，最近已经开发并实践了几种手术程序，包括气管切除术、端端气管吻合术和气管成形术。然而，由于手术后出现气道再狭窄的情况，临床结果通常并不令人满意。目前有多种类型的支架可用于气道支架，包括不可降解的硅酮管和生物惰性金属支架（裸支架或聚合物基质涂层）以及由金属芯强化的混合硅酮管，但没有一种支架能提供令人满意的长期效果。因此，临床上迫切需要一种可生物降解的气道支架，它能在达到预期目标后保持气道通畅，并随着时间的推移完全降解。本研究旨在探讨可生物降解的镁-铝-锌-钙-锰（AZXM）合金作为一种潜在的气管支架。新型 AZXM 合金是通过部分用钙替代商用 AZ31 合金中的铝来制备的。本研究表明，钙优先沿晶界偏析形成金属间化合物相（MgCa），并均匀分布在镁基体中。与铸态和固溶处理的 AZXM 合金相比，挤压的 AZXM 合金表现出更少的点蚀，在 Hank's Balanced Salt Solution（HBSS）中具有更高的耐腐蚀性，并表现出优化的机械性能。体外细胞毒性评估用人气管上皮细胞表明，与纯镁和商用 AZ31 相比，AZXM 合金具有优异的细胞相容性，这一点已通过初步的兔体内气管模型研究得到验证。初步结果表明，使用可生物降解的 AZXM 合金作为气管支架的方法确实很有前途，尽管需要进一步的合金加工来提高所需的延展性，然后进行更详尽的体内研究，以证明支架应用的完全可行性。
