Collaborative Research: ISS: Biofilm Inhibition with Germicidal Light Side-Emitted from Nano-enabled Flexible Optical Fibers in Water Systems

Bacteria grow on surfaces as thin, slimy biofilms in nearly anything that contains water. Over 90% of microorganisms present in water exist within biofilms, compared to less than 10% in the flowing water. Biofilms can adversely impact water quality by harboring pathogens, such as Legionella pneumophila, that can be released back into water, or adversely impact water system operations (e.g., mediating surface corrosion, reducing heat transfer, clogging of valves or sensors).

Biofilms exist and cause problems in medical devices, industrial manufacturing, and drinking water systems, including those upon which astronauts rely. For example, in the International Space Station, biofilm formation jeopardizes key equipment including spacesuits, water recycling units, radiators, and navigation windows. Chemical strategies to control biofilms require transport, storage and input of high-strength disinfecting solutions that may bring other problems.

This project aims to understand and demonstrate how germicidal ultraviolet light delivered using nano fibers, which behave like “disinfecting glowsticks”, to surfaces where biofilms might grow. The germicidal ultraviolet light kills any bacteria that stick to or grow on a surface. Although the same types of bacteria grow on Earth and in the water systems on the International Space Station, the lack of gravity in space can influence how bacteria communities grow, providing key insights.

The research team will conduct parallel experiments on Earth and on the International Space Station to understand if ultraviolet light influences biofilms differently because of gravity effects. Comparing biofilm growth and response to germicidal ultraviolet light in microgravity versus earth-gravity will enhance our ability to create healthy human habitats.

The research team will work with high school students, explaining the roles of biofilms in everyday life through a four-part biofilm module. This module will be developed using chemical-free disinfection solutions enabled by nanotechnology.

Currently, the sensitivity of biofilms to germicidal ultraviolet light in microgravity is unknown. This project involves the Center for the Advancement of Science in Space, the entity responsible for managing the International Space Station National Lab. Experiments will study effects of germicidal ultraviolet light (265 to 285 nanometers) on the inhibition of biofilms in water systems using five bacterial species that reportedly are present in biofilms in International Space Station water systems.

First, the germicidal ultraviolet light biofilm inhibition experiments on the International Space Station will demonstrate impacts of germicidal light on biofilm formation on materials relevant to those used in International Space Station water systems. The feasibility of this approach as a chemical-free, long-duration biofilm control strategy in an extreme environment (microgravity) will be compared against otherwise identical ground controls on Earth.

The influence of microgravity is important to understand since the growth and final density of some bacteria, and associated biofilm formation, can differ in microgravity, as compared to earth gravity. Second, experiments in a water-filled reactor equipped with side-emitting optical fibers decorated using different types of nanoparticles will be operated under earth-gravity to study the effects of two mechanisms (photolysis versus oxidation) to mitigate biofilm formation.

Germicidal light is produced from mercury-free light emitting diodes, which enters unique nanotechnology enabled optical fibers that attach directly on surfaces and side-emit ultraviolet light. State of the art nanomaterial, chemical and biological methods and models will be applied to study biofilms. Duty-cycling of light emitting diode operation will be studied to reduce power requirements, and correspondingly the thermal load that requires management while achieving biofilm mitigation.

The PIs will develop and apply quantitative polymerase chain reaction primers to identify each bacteria comprising the consortia for monitoring population levels. Additionally, the researchers will apply fluorescent viability stain with confocal microscopy plus image analysis to assess changes in biofilm viability and architecture upon ultraviolet light exposure.

The broader impacts include developing a new four part biofilm module focusing on chemical free solutions enabled by nanotechnology, that will be co-developed and used with high school teachers and in public outreach activities. The project will advance the fundamental understanding of biocidal treatment efficiency in microgravity environments, where bacterial growth and biofilm formation can differ as compared to Earth.

Comparing biofilm growth and response to UV-C light in microgravity versus earth-gravity will advance our ability to create healthy human habitats.

This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.