Biomaterials-associated infections are most frequently caused by the colonization of microorganisms on the materials’ surface. In the form of biofilms, bacterial cells are highly resistant against biocides and mechanical stress. Previously, it was shown that titanium surfaces with a nano-roughness in the range of 2 – 6 nm have the potential to reduce microbial adhesion. The nano-roughness of our previous approach is limited due to the instrumental restriction of physical vapor deposition (PVD). We aim to extend this research by examining the previously uninvestigated roughness range of Ra= 2 – 16 nm. Therefore, we modified the previous approach to a combination of PVD and wet etching. Additionally, we wish to understand how the nano-roughness influences microbial adhesion as well as protein adsorption.
Titanium thin films, as prepared by PVD, were consequently treated in NaOH solution with tunable concentration, in order to achieve surfaces with an extended nano-roughness range from 6 to 24 nm. Through a second titanium layer prepared by the PVD, uniform chemical properties of the different rough surfaces have been ensured. Atomic force microscopy (AFM), scanning electron microscopy (SEM) as well as x-ray photoelectron spectroscopy (XPS) were used to characterize the surfaces in terms of roughness, morphology and chemical properties. Also bacterial adhesion tests with Escherichia coli for different adhesion times and protein (albumin and fibrinogen) adsorption tests with different concentrations were done. Fluorescence microscopy and SEM were used to characterize the bacterial adhesion tests and AFM and µBCA were used to measure the protein adsorption.
We present a summary of our results of nano-rough titanium thin films produced with this method. It is possible to create roughness through etching in the predefined range. The SEM images show similar morphologies to surfaces prepared only by the PVD. Similarly, the chemical properties are the same after the second round of PVD. Also we present our first results of the microbial adhesion and protein adsorption tests.
These results show that this method is suitable to produce nano-rough titanium surfaces in the required range. This is the foundation for investigating the influence of nano-rough surfaces on microbial adhesion.
We thank the DFG for funding of our project: “Antimicrobial Effect of Nano-rough Titanium surfaces: Reduction of Microbial Adhesion and Mechanisms of Reduction” AOBJ: 622946.