Bacterial attachment on sub-nanometrically smooth titanium substrata

Despite the volume of work that has been conducted on the topic, the role of surface topography in mediating bacterial cell adhesion is not well understood. The primary reason for this lack of understanding is the relatively limited extent of topographical characterisation employed in many studies. In the present study, the topographies of three sub-nanometrically smooth titanium (Ti) surfaces were comprehensively characterised, using nine individual parameters that together describe the height, shape and distribution of their surface features. This topographical analysis was then correlated with the adhesion behaviour of the pathogenic bacteria Staphylococcus aureus and Pseudomonas aeruginosa, in an effort to understand the role played by each aspect of surface architecture in influencing bacterial attachment. While P. aeruginosa was largely unable to adhere to any of the three sub-nanometrically smooth Ti surfaces, the extent of S. aureus cell attachment was found to be greater on surfaces with higher average, RMS and maximum roughness and higher surface areas. The cells also attached in greater numbers to surfaces that had shorter autocorrelation lengths and skewness values that approached zero, indicating a preference for less ordered surfaces with peak heights and valley depths evenly distributed around the mean plane. Across the sub-nanometrically smooth range of surfaces tested, it was shown that S. aureus more easily attached to surfaces with larger features that were evenly distributed between peaks and valleys, with higher levels of randomness. This study demonstrated that the traditionally employed amplitudinal roughness parameters are not the only determinants of bacterial adhesion, and that spatial parameters can also be used to predict the extent of attachment.尽管该领域已有大量研究积累，但表面形貌在介导细菌细胞黏附过程中所发挥的调控作用仍未得到充分阐明。造成这一认知空白的主要原因，在于诸多现有研究中所采用的表面形貌表征手段相对有限。本研究针对三种亚纳米级平整钛（Ti）表面开展了全面形貌表征，选用9项独立参数共同描述其表面形貌的高度、形态与分布特征。随后将该形貌分析结果与病原菌金黄色葡萄球菌（Staphylococcus aureus）、铜绿假单胞菌（Pseudomonas aeruginosa）的黏附行为进行关联，以期阐明表面结构的各维度特征对细菌附着的调控作用。尽管铜绿假单胞菌几乎无法在这三种亚纳米级平整钛表面发生黏附，但研究发现，当表面的平均粗糙度、均方根（RMS）粗糙度与最大粗糙度更高、表面积更大时，金黄色葡萄球菌的细胞附着量也随之增加。此外，细胞在自相关长度更短、偏度值趋近于0的表面附着数量更多，这表明金黄色葡萄球菌更偏好表面有序性更低、峰高与谷深围绕平均平面均匀分布的形貌。在所测试的亚纳米级平整表面范围内，研究证实金黄色葡萄球菌更易附着于特征尺寸更大、峰谷分布更均匀且随机性更高的表面。本研究表明，传统所采用的振幅粗糙度参数并非决定细菌黏附的唯一因素，空间参数同样可用于预测细菌附着程度。