Testing laser-patterned antimicrobial surfaces against bacterial biofilm formation in the ISS experiment "BIOFILMS"

Kurzfassung

A major problem in human space missions is microbial contamination. Biofilms in particular pose a potential hazard as they damage equipment and pose a health risk to astronauts. Biofilm formation can be reduced or inhibited by using antimicrobial active metal surfaces, such as copper surfaces. Previous studies have shown that the antimicrobial efficacy of copper surfaces can even be enhanced by additional surface functionalization using direct laser interference patterning with ultrashort pulses (USP-DLIP). The effectiveness of these functionalized surfaces under altered gravity conditions is being investigated in the "BIOFILMS" space experiment on board the International Space Station (ISS). Copper and brass (CuZn37) were selected as antimicrobial surfaces for the experiment, while stainless steel is used as an inert reference. All three surfaces were tested with and without surface functionalization. Using the Kubik facility in the Columbus laboratory on board the ISS, the antimicrobial efficacy of these surfaces is tested under three different gravity conditions (µg, 0.4 x g, 1 x g). Staphylococcus capitis, Cupriavidus metallidurans and Acinetobacter radioresistens were selected as bacterial model organisms. The bacteria were incubated with the different surfaces in a special hardware that allowed biofilm formation under controlled conditions. In total, the BIOFILMS experiment consisted of three flights to the ISS to accommodate all sample configurations (metal type, surface functionalization, bacteria, gravity conditions). The first BIOFILMS flight took place in August 2021, the second in June 2022, and the last flight in March 2023. We present here preliminary results of the experiment. However, post-flight analysis of all samples from the three flights is ongoing. The results of the experiment will help make spaceflight safer and more sustainable by providing new insights into appropriate surfaces and functionalization processes that help reduce bacterial biofilm formation.