Controlled bacterial interaction to increase the antimicrobial efficiency of copper surfaces

通过使用抗菌铜合金，可以显著降低医院等公共设施接触表面的细菌负荷，从而降低感染性疾病的传播，特别是由多重耐药细菌引起的感染性疾病。含铜表面的抗菌效果与其表面性质密切相关，表面性质可能对细菌的杀灭产生有益或抑制作用，本项目的目的之一是量化表面形貌和化学性质对铜及其合金抗菌效果的影响。细菌为什么以及如何附着在改性铜表面，以及这是如何与基板的抗菌效果需要彻底调查。激光辅助表面处理能够调节表面形貌和化学性质。通过这种方式，纯电化学杀菌机制被地形接触机械效应补充。通过直接激光干涉图案化（DLIP）产生与细菌相似规模的表面结构，以选择性地增加或减少它们与基材的接触面积。使用不同的脉冲持续时间（10^-9至10^-15 s），可以通过改变激光/材料相互作用（烧蚀或熔化）来改变表面化学性质，而不会显著改变所产生的表面形貌。这个过程对润湿性的影响进行了定量分析，使用高分辨率的微观结构和化学表征，并与表面的杀菌效率。为了更好地了解细菌和基板之间的相互作用，细菌在不同的改性表面上的粘附性通过记录力/距离曲线使用单细菌探针在AFM检查。评估细菌，这是开发对改性铜表面的电阻所产生的风险是本研究的另一个目的。在实验过程中对铜产生抗性的细菌菌株，被测试其特征性致病特性的变化，如活力，增殖和毒力。考试还包括通过基因组和转录组论文分析分离的突变菌株的铜抗性机制。关于铜合金的表面性质和其抗菌效率之间的联系所获得的知识将使这些材料在抗菌应用中得到更集中和有效的利用。

The bacterial load on contact surfaces in public facilities such as hospitals can be reduced significantly by utilising antimicrobial copper alloys, which are lowering the spreading of infection diseases, particularly those caused by multi-resistant germs. The antimicrobial efficiency of copper containing surfaces is closely linked to their surface properties, which might have a beneficial or inhibitive effect on the bacterial killing.One objective of this project is to quantify the influence of the topographical and chemical properties of the surface on the antimicrobial efficiency of copper and its alloys. Why and how bacteria adhere to modified copper surface as well as how this is linked to the antimicrobial effect of the substrate needs to be thoroughly investigated. Laser-assisted surface processing enables the modulation of both surface topography and chemistry. By this, the purely electro-chemical bacteria killing mechanism is supplemented by topographical contact mechanic effects. Surface structures of similar scale as the bacteria are generated by Direct Laser Interference Patterning (DLIP) in order to selectively increase or reduce their contact area to the substrate. Using different pulse durations (10^-9 to 10^-15 s) provides the possibility to alter the surface chemistry due to varying laser/material interactions (ablation or melting) without significantly changing the produced surface topographies. The influence of this process on the wettability is quantitatively analysed using high-resolution microstructural and chemical characterisation and correlated to the bacterial killing efficiency of the surfaces. In order to achieve a better understanding of the interactions between the bacteria and the substrate, the adhesion of the germs on different modified surfaces is examined by recording force/distance curves using single-bacteria probes in AFM.Assessing the risk emanating from bacteria, which are developing resistances towards modified copper surfaces represents an additional objective of this study. Bacterial strains, which grew resistant to copper during the experiments, are tested for changes in their characteristic pathogenic properties like viability, proliferation and virulence. The examinations are also including the analysis of copper resistance mechanisms of isolated mutated strains by genome- and transcriptome essays. The knowledge gained about the connection of surface properties of copper alloys and their antimicrobial efficiency shall enable a more focused and efficient utilisation of these materials in antimicrobial applications.