Controlled bacterial interaction to increase the antimicrobial efficiency of copper surfaces

通过使用抗菌铜合金，可以显著减少医院等公共设施接触表面的细菌负荷，从而降低感染疾病的传播，特别是由多重耐药细菌引起的疾病。含铜表面的抗菌效果与其表面性质密切相关，表面性质对细菌的杀灭可能是有益的，也可能是有抑制作用的。本课题的目的之一是量化表面的形貌和化学性质对铜及其合金的抗菌效果的影响。细菌为什么以及如何附着在改性的铜表面，以及这与底物的抗菌效果之间的联系，需要彻底调查。激光辅助表面处理可以同时调节表面形貌和化学成分。由此，地形接触力学效应补充了纯电化学法杀菌机理。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，以便选择性地增加或减少它们与底物的接触面积。使用不同的脉冲持续时间(10^-9到10^-15 S)可以改变由于不同的激光/材料相互作用(烧蚀或熔化)而导致的表面化学变化，而不会显著改变所产生的表面形貌。利用高分辨率显微结构和化学表征定量分析了这一过程对润湿性的影响，并与表面的杀菌效率进行了关联。为了更好地了解细菌与底物之间的相互作用，通过使用AFM中的单细菌探针记录力/距离曲线，检查了细菌在不同改性表面上的粘附性。评估细菌产生的风险，这些细菌正在对改性铜表面产生抵抗力，这是本研究的另一个目标。在实验期间对铜产生抗药性的细菌菌株，被测试其特有的致病特性的变化，如生存能力、增殖和毒力。这些检查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。所获得的关于铜合金表面特性与其抗菌效率之间关系的知识将使这些材料能够在抗菌应用中得到更有针对性和更有效的利用。

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.