Interstellar microbes could become earthly pathogens, which is why NASA is interested in new sterilization technologies. As space research advances, so do questions about how to prevent interplanetary contamination, or the flow of microbes from space to earth—and vice versa.
Existing space program sterilization technologies are either costly, cumbersome, take too long, or are harsh on sensitive spacecraft equipment. But a Gainesville-based technology business, SurfPlasma, Inc., has some ideas on how to fix these limitations.
Their concept for a compact, portable plasma reactor, or CPPR for short, was promising enough that NASA recently provided $131,000 in seed funding to prove it out.
Principal investigator Bhaswati Choudhury, a research scientist with SurfPlasma, says that tests to measure its effectiveness at killing microbes will be carried out at the EPI, which is partnering on the project.
“What we are doing is seeing if this technology can be used to achieve decontamination in space missions,” Choudhury says. “We are trying to make a decontamination chamber which will sterilize using ozone but in much less time and without causing material damage, compared to other existing methods.”
Choudhury is working with UF research scientist John Lednicky, a professor in the College of Public Health and Health Professions, to investigate the use of plasma in killing SARS-CoV-2. Their work often brings them to UF’s Emerging Pathogens Institute, to use its biosecure laboratories and library of pathogenic agents to conduct experiments.
How it works
The CPPR uses ionized air and ozone generation to kill a broad selection of bacteria and viruses. Preliminary work shows it is effective against both gram-negative and gram-positive bacteria, such as Escherichia coli, Vibrio cholera, Listeria, Pseudomonas aeruginosa and Yersinia enterocolitica for sterilization.
The device is based on a fundamental plasma reactor concept. It uses a few watts of electricity to ionize air across electrodes separated by an insulating mechanism. The ionized air results in the generation of ozone, which is made of three oxygen atoms and is highly reactive. A built-in catalytic ozone decomposition system in the decontamination chamber will safely process toxic waste gasses produced from oxidative reactions.
Ozone occurs naturally in the Earth’s atmosphere where it plays an important role in shielding the planet from harmful ultraviolet radiation. But ozone can also be made synthetically, and it has been shown to be useful in killing or inactivating microorganisms. When ozone atoms contact the outer surface of a microbe, a reaction called an oxidative burst happens. This creates a small hole in the cell wall.
Now imagine thousands of ozone atoms carpet bombing a bacterium over a few seconds or minutes. It won’t take long before the bacterium’s surface is riddled with holes, it loses its shape, and the organism dies.
The NASA grant is an extension of Choudhury’s doctoral research. She completed her Ph.D. in mechanical and aerospace engineering at UF under the advisement of Subrata Roy in 2020. Roy is both the president of SurfPlasma and a professor in UF’s Herbert Wertheim College of Engineering Department of Mechanical and Aerospace Engineering.
Choudhury was first introduced to the concept of using plasma to kill pathogens by Judith A. Johnson, a retired researcher and faculty member at UF’s College of Medicine Department of Pathology, Immunology and Laboratory Medicine and the Emerging Pathogens Institute.
Proof of concept testing
The new NASA-funded project seeks to determine the most time-efficient exposure needed to kill 99% of the bacteria in a sample. To do this, researchers will time exposures of Bacillus subtilis and E. coli to the CPPR and then attempt to grow the exposed pathogens on culture mediums. The idea is to find the right exposure that kills the most bacteria, without having the exposure time be unnecessarily long.
These microbes were chosen for testing because they tend to be resistant and endure in harsh environments, says Támara Revazishvili, an EPI researcher who is leading the institute’s involvement in the project. They can even enter dormant states that allow them to grow once conditions turn favorable. Revazishvili will oversee the experiments carried out at the EPI.
“Bhaswati defended her thesis on plasma decontamination very successfully and went to work in industry,” Revazishvili says. “And now, we need to help NASA. It’s very exciting.”
The CPPR device that SurfPlasma envisions making will be battery-operated, compact, lightweight and portable. It will also be safe to use around sensitive electronics, digital screens and computers. This would fill an important need, Choudhury says, because current sterilization techniques rely on chemicals, such as vaporized hydrogen peroxide, or dry heat, both of which can be harsh or destructive on electronics used in spacecraft development.
The project seeks to verify that the concept works. If it does, additional funding will be needed to devise how to manufacture the device and produce it at scale.
“It is great to be a part of the NASA Jet Propulsion Laboratory’s space program for enabling end-to-end sample return functions to assure containment and pristine preservation of materials gathered on NASA missions,” says Roy, SurfPlasma’s president. “This plasma technology can be useful for ground-based contamination control even for testing operations and eventually for in-flight cross-contamination control.”