Department of Bioengineering, College of Chemical and Environmental Engineering, Shandong University of Science and Technology, Qingdao 266590, China.
College of Materials Science and Engineering, Shandong University of Science and Technology, Qingdao 266590, China.
Acta Biomater. 2019 Oct 15;98:196-214. doi: 10.1016/j.actbio.2019.05.069. Epub 2019 May 31.
A Zinc-loaded montmorillonite (Zn-MMT) coating was hydrothermally prepared using Zn ion intercalated sodium montmorillonite (Na-MMT) upon magnesium (Mg) alloy AZ31 as bone repairing materials. Biodegradation rate of the Mg-based materials was studied via potentiodynamic polarization curves, electrochemical impedance spectroscopy (EIS) and hydrogen evolution tests. Results revealed that both Na-MMT and Zn-MMT coatings exhibited better corrosion resistance in Dulbecco's modified eagle medium (DMEM) + 10% calf serum (CS) than bare Mg alloy AZ31 counterparts. Hemolysis results demonstrated that hemocompatibility of the Na-MMT and Zn-MMT coatings were 5%, and lower than that of uncoated Mg alloy AZ31 pieces. In vitro MTT tests and live-dead stain of osteoblast cells (MC3T3-E1) indicated a significant improvement in cytocompatibility of both Na-MMT and Zn-MMT coatings. Antibacterial properties of two representative bacterial strains associated with device-related infection, i.e. Escherichia coli (E. coli) and Staphylococcus aureus (S. aureus), were employed to explore the antibacterial behavior of the coatings. The measured inhibitory zone and bacterial growth rate confirmed that Zn-MMT coatings exhibited higher suppression toward both E. coli and S. aureus than that of Na-MMT coatings. The investigation on antibacterial mechanism through scanning electron microscopy (SEM) and lactate dehydrogenase (LDH) release assay manifested that Zn-MMT coating led to severe breakage of bacterial membrane of E. coli and S. aureus, which resulted in a release of cytoplasmic materials from the bacterial cells. In addition, the good inhibition of Zn-MMT coatings against E. coli and S. aureus might be attributed to the slow but sustainable release of Zn ions (up to 144 h) from the coatings into the culture media. This study provides a novel coating strategy for manufacturing biodegradable Mg alloys with good corrosion resistance, biocompatibility and antibacterial activity for future orthopedic applications. STATEMENT OF SIGNIFICANCE: The significance of the current work is to develop a corrosion-resistant and antibacterial Zn-MMT coating on magnesium alloy AZ31 through a hydrothermal method. The Zn-MMT coating on magnesium alloy AZ31 shows better corrosion resistance, biocompatibility and excellent antibacterial ability than magnesium alloy AZ31. This study provides a novel coating on Mg alloys for future orthopedic applications.
一种负载锌的蒙脱石（Zn-MMT）涂层通过将锌离子嵌入钠蒙脱石（Na-MMT），然后在镁（Mg）合金 AZ31 上进行水热合成，用作骨修复材料。通过动电位极化曲线、电化学阻抗谱（EIS）和析氢试验研究了 Mg 基材料的生物降解速率。结果表明，在杜氏改良伊格尔培养基（DMEM）+10%小牛血清（CS）中，Na-MMT 和 Zn-MMT 涂层均比裸 Mg 合金 AZ31 具有更好的耐腐蚀性。溶血结果表明，Na-MMT 和 Zn-MMT 涂层的血液相容性为 5%，低于未涂层的 Mg 合金 AZ31 片。体外 MTT 试验和成骨细胞（MC3T3-E1）死活染色表明，Na-MMT 和 Zn-MMT 涂层的细胞相容性均有显著提高。两种与器械相关感染相关的代表性细菌菌株，即大肠杆菌（E. coli）和金黄色葡萄球菌（S. aureus）的抗菌性能，用于探索涂层的抗菌行为。通过测量抑菌圈和细菌生长率证实，Zn-MMT 涂层对大肠杆菌和金黄色葡萄球菌的抑制作用均高于 Na-MMT 涂层。通过扫描电子显微镜（SEM）和乳酸脱氢酶（LDH）释放试验研究抗菌机制表明，Zn-MMT 涂层导致大肠杆菌和金黄色葡萄球菌的细胞膜严重破裂，导致细胞质物质从细菌细胞中释放出来。此外，Zn-MMT 涂层对大肠杆菌和金黄色葡萄球菌的良好抑制作用可能归因于涂层缓慢但持续向培养基中释放 Zn 离子（长达 144 小时）。本研究为制造具有良好耐腐蚀性、生物相容性和抗菌活性的可生物降解 Mg 合金提供了一种新的涂层策略，为未来的骨科应用提供了一种新的策略。
