Touching surfaces- antibacterial surfaces for spaceflight and clinical applications

The International Space Station (ISS) is a unique environment with its microbiome originating mostly from the inhabiting crew. Due to its remoteness and the extreme conditions, such as increased radiation and microgravity, the ISS represents an ideal testing ground for studying microbial adaptation in confined habitats. On the ISS, but similarly also in other restricted areas such as intensive care units, fomites can be niches for opportunistic pathogens, which are then further spread via contact. To reduce bacterial contamination on surfaces, antibacterial surfaces can be implemented.

In the Cosmic Kiss project "Touching Surfaces" novel copper- based antibacterial surfaces were tested under real spaceflight conditions, in schools, and in clinical settings. The surfaces combine chemically antibacterial properties through the use of copper and brass as a copper-alloy as well as topographic properties to enhance antibacterial efficacy. Three different metals were implemented: Stainless steel as inert reference surface and copper as well as brass as antibacterial metals. Using Ultrashort Pulsed Direct Laser Interference Patterning (USP- DLIP) micro- and nanometer structures were created in each metal. The micro-structures were supposed to enhance the contact between surface and bacteria, thereby increasing the antibacterial activity of copper. Whereas the nanostructures were employed to hamper adhesion of bacteria to the surface. The surfaces were inserted into spaceflight hardware, so-called "Touch Arrays". These were then installed in schools in Germany as part of a citizen science project, a university hospital, and on the ISS, where they were touched frequently over a defined timeframe.

After the experiment duration, surfaces were tested for their robustness against frequent touching using electron microscopy. Results showed that structured surfaces remained intact despite frequent contact and organic contamination. Additionally, the microbial community was analyzed using culture-dependent and independent approaches. All copper surfaces and nanostructured brass surfaces in particular showed reduced microbial contamination.