Fast corroding, thin magnesium coating displays antibacterial effects and low cytotoxicity

Bacterial colonisation and biofilm formation are characteristics of implant-associated infections. In search of candidates for improved prosthetic materials, fast corroding Mg-based coatings on titanium surfaces were examined for their cytotoxic and antimicrobial properties. Human osteoblasts and <i>Staphylococcus epidermidis</i> were each cultured on cylindrical Ti samples coated with a thin layer of Mg/Mg₄₅Zn₅Ca, applied <i>via</i> magnetron sputtering. Uncoated titanium samples served as controls. <i>S. epidermidis</i> was quantified by counting colony forming units. The biofilm-bound fraction was isolated <i>via</i> ultrasonic treatment, and the planktonic fraction <i>via</i> centrifugation. Biofilm-bound <i>S. epidermidis</i> was significantly decreased by approximately four to five orders of magnitude in both Mg- and Mg₄₅Zn₅Ca-coated samples after seven days compared to the control. The osteoblast viability was within the tolerance threshold of 70% stated in DIN EN ISO 10993-5:2009-10 for Mg (~80%) but not for Mg₄₅Zn₅Ca (~25%). Accordingly, Mg-coated titanium was identified as a promising candidate for an implant material with antibacterial properties and low cytotoxicity levels. The approach of exploiting fast corrosion contrasts with existing methods, which have generally focused on reducing corrosion.

细菌定植与生物膜形成是植入物相关感染的典型特征。为筛选可优化修复材料的候选方案，本研究针对钛表面的快速腐蚀型镁基涂层开展了细胞毒性与抗菌性能评估。研究人员将人成骨细胞与表皮葡萄球菌（Staphylococcus epidermidis）分别接种于经磁控溅射（magnetron sputtering）法制备的Mg/Mg₄₅Zn₅Ca薄层涂层圆柱形钛（Titanium, Ti）样品表面，未涂层的钛样品作为对照组。通过菌落形成单位（colony forming units）计数法对表皮葡萄球菌进行定量分析：通过超声处理分离生物膜结合的细菌组分，通过离心分离浮游细菌组分。培养7天后，相较于对照组，Mg涂层与Mg₄₅Zn₅Ca涂层样品中的生物膜结合型表皮葡萄球菌数量均显著降低约4~5个数量级。根据DIN EN ISO 10993-5:2009-10标准中规定的70%细胞活性耐受阈值，Mg涂层样品的成骨细胞活性约为80%，符合耐受要求；而Mg₄₅Zn₅Ca涂层样品的成骨细胞活性仅约25%，未达标准。据此，镁涂层钛材被认定为兼具抗菌性能与低细胞毒性的极具应用前景的植入材料候选方案。本研究采用的快速腐蚀策略，与现有多数旨在降低腐蚀速率的植入材料改性方法形成鲜明对比。