Department of Materials Science and Engineering, The Ohio State University, 4020 Fontana Labs, 140 W. 19th Avenue, Columbus, OH 43210, USA.
Department of Neurosurgery, Pusan National University Hospital, Biomedical Research Institute, Busan, Republic of Korea.
Acta Biomater. 2022 Sep 15;150:442-455. doi: 10.1016/j.actbio.2022.07.040. Epub 2022 Jul 29.
Squeeze casting of biodegradable Mg-4Zn-0.5Ca-xMn (x = 0, 0.4 or 0.8 all in weight %) alloys is a process intended to improve mechanical properties (i.e., strength and ductility), corrosion performance (i.e., resistance), and biocompatibility (i.e., little to no cytotoxicity). In this study, we found that an increased Mn content causes the dendritic microstructure of squeeze-cast Mg-4Zn-0.5Ca-xMn to become more refined and uniform, while the volume fraction of the CaMgZn phase simultaneously increases. Squeeze-cast Mg-4Zn-0.5Ca-0.8Mn presents the best yield strength, ultimate tensile strength, and elongation of the alloys tested. An electrochemical corrosion test in Hanks' solution at 36.5°C demonstrates that the corrosion resistance of squeeze-cast Mg-4Zn-0.5Ca-xMn alloys show improvement at higher Mn levels. Additionally, squeeze-cast Mg-4Zn-0.5Ca alloys containing Mn exhibit favorable biocompatibility, as evidenced by cell viability studies with MC3T3-E1 cells and a local lymph node assay test. Squeeze-cast alloy specimens implanted into the skull and spine of Sprague-Dawley rats for four weeks showed no serious cytotoxicity or foreign body response; however, swelling was observed in the implantation areas of Mn-free squeeze-cast Mg-4Zn-0.5Ca alloy, while no swelling was observed in rats implanted with Mn-containing Mg-4Zn-0.5Ca alloy. These findings indicate potential applications of biodegradable, Mn-containing, squeeze-cast Mg-4Zn-0.5Ca specimens in bone-reconstruction devices given their biocompatibility, mechanical properties, and degradation profiles. STATEMENT OF SIGNIFICANCE: Bioresorbable magnesium alloys have recently gained attention as viable biomaterials for skeletal reconstruction implants. Extensive research on biodegradable Mg alloy design, synthesis, and as-cast versus post-processed material properties useful for medical applications have been reported. The squeeze-casting technique used in this study can improve the mechanical properties (i.e., strengthening) and corrosive performance (reduced rate) of bioresorbable Mg-Zn-Ca-Mn alloys. Squeeze-casting of these alloys is also expected to improve specimen microstructure, near-net-shape manufacturing, and cost (i.e., reduced). This study provides an in vitro and in vivo assessment of squeeze-cast Mg-Zn-Ca-Mn alloys for biomedical applications.
挤压铸造可生物降解 Mg-4Zn-0.5Ca-xMn（x=0、0.4 或 0.8 均为重量%）合金是一种旨在改善力学性能（即强度和延展性）、腐蚀性能（即耐腐蚀性）和生物相容性（即细胞毒性低）的工艺。在这项研究中，我们发现 Mn 含量的增加导致挤压铸造 Mg-4Zn-0.5Ca-xMn 的枝晶微观结构变得更加细化和均匀，同时 CaMgZn 相的体积分数也同时增加。挤压铸造 Mg-4Zn-0.5Ca-0.8Mn 表现出所测试合金中最佳的屈服强度、极限拉伸强度和伸长率。在 36.5°C 的 Hank's 溶液中的电化学腐蚀测试表明，随着 Mn 水平的提高，挤压铸造 Mg-4Zn-0.5Ca-xMn 合金的耐腐蚀性得到改善。此外，含有 Mn 的挤压铸造 Mg-4Zn-0.5Ca 合金表现出良好的生物相容性，这可以通过 MC3T3-E1 细胞的细胞活力研究和局部淋巴结测定试验来证明。在 Sprague-Dawley 大鼠的颅骨和脊柱中植入挤压铸造合金 4 周后，没有观察到严重的细胞毒性或异物反应；然而，在不含 Mn 的挤压铸造 Mg-4Zn-0.5Ca 合金的植入区域观察到肿胀，而在植入含 Mn 的 Mg-4Zn-0.5Ca 合金的大鼠中没有观察到肿胀。这些发现表明，具有生物降解性、含 Mn、挤压铸造的 Mg-4Zn-0.5Ca 标本在骨骼重建装置中具有潜在的应用前景，因为它们具有生物相容性、机械性能和降解特性。
可生物降解的镁合金作为骨骼重建植入物的可行生物材料，最近受到了关注。已经报道了大量关于可生物降解镁合金设计、合成以及对医疗应用有用的铸态与后处理材料性能的研究。本研究中使用的挤压铸造技术可以提高可生物降解的 Mg-Zn-Ca-Mn 合金的力学性能（即强化）和腐蚀性（降低速率）。挤压铸造这些合金也有望改善试件的微观结构、近净成形制造和成本（即降低）。本研究对用于生物医学应用的挤压铸造 Mg-Zn-Ca-Mn 合金进行了体外和体内评估。
