Yang Chung-Wei, Wang Guan-Kai
Department of Materials Science and Engineering, National Formosa University, No. 64, Wunhua Road, Huwei, Yunlin 63201, Taiwan.
Materials (Basel). 2020 Jan 27;13(3):591. doi: 10.3390/ma13030591.
The biomedical applications of Mg-based alloys are limited by their rapid corrosion rate in the body fluid. In this study, the hydrothermal synthesis is employed to produce protective bioactive hydroxyapatite coating (HAC) and strontium-substituted hydroxyapatite coating (Sr-HAC) to further enhance the corrosion resistance and in vitro biocompatibility of biodegradable AZ91D Mg alloy in physiological environments. For comparison, the brucite Mg(OH) prepared by the alkaline pre-treatment is designated as a control group. Experimental evidences of XRD and XPS analysis confirm that Sr ions can be incorporated into HA crystal structure. It is noted that the hydrothermally synthesized Sr-HAC conversion coating composed of a specific surface topography with the nanoscaled flake-like fine crystallites is constructed on the AZ91D Mg alloy. The hydrophilicity of Mg substrate is effectively enhanced with the decrease in static contact angles after performing alkaline and hydrothermal treatments. Potentiodynamic polarization measurements reveal that the nanostructured Sr-HAC-coated specimens exhibit superior corrosion resistance than HAC and alkaline pre-treated Mg(OH). Moreover, immersion tests demonstrate that Sr-HAC provides favorable long-term stability for the Mg alloy with decreasing concentration of released Mg ions in the SBF and the reduced corrosion rate during the immersion length of 30 days. The cells cultured on Sr-HAC specimens exhibit higher viability than those on the alkaline-pre-treated Mg(OH) and HAC specimens. The Sr-substituted HA coating with a nanostructured surface topography can help to stimulate the cell viability of osteoblastic cells.
镁基合金的生物医学应用受到其在体液中快速腐蚀速率的限制。在本研究中，采用水热合成法制备保护性生物活性羟基磷灰石涂层（HAC）和锶取代羟基磷灰石涂层（Sr-HAC），以进一步提高可降解AZ91D镁合金在生理环境中的耐腐蚀性和体外生物相容性。作为对比，将通过碱性预处理制备的水镁石Mg(OH)₂指定为对照组。XRD和XPS分析的实验证据证实锶离子可以掺入HA晶体结构中。值得注意的是，在AZ91D镁合金上构建了由具有纳米级片状微晶的特定表面形貌组成的水热合成Sr-HAC转化涂层。经过碱性和水热处理后，随着静态接触角的减小，镁基体的亲水性得到有效增强。动电位极化测量表明，纳米结构的Sr-HAC涂层试样比HAC和碱性预处理的Mg(OH)₂具有更好的耐腐蚀性。此外，浸泡试验表明，Sr-HAC为镁合金提供了良好的长期稳定性，在模拟体液（SBF）中释放的镁离子浓度降低，且在30天的浸泡期内腐蚀速率降低。在Sr-HAC试样上培养的细胞比在碱性预处理的Mg(OH)₂和HAC试样上培养的细胞具有更高的活力。具有纳米结构表面形貌的锶取代HA涂层有助于刺激成骨细胞的细胞活力。
