ON JUNE 3, the SpaceX CRS-22 rocket took off for the International Space Station-bound from Cape Canaveral, Florida.
On board was unusual cargo: oral bacteria and saliva.
The idea is to test germs and the saliva and how they behave after treatment with toothpastes, mouthwashes, and other disease-fighting products in space.
Bacterial growth, for example, will be monitored.
Both bacteria that are healthy to the oral environment and microbes that cause cavities and gum disease were collected from the mouths of 30 dental clinic patients at the University of Nevada, Las Vegas (UNLV).
The germs and saliva were then placed in 25 kits developed by UNLV engineers.
The kits contain 3D-printed, battery-powered microfluidic pump devices that dispense fluids at an ultra-low flow rate. The devices mimic conditions inside the human mouth.
Dr. John Gallob and Lacey Rahmig, clinical researchers at the UNLV School of Dental Medicine, collected the bacteria and saliva samples. Engineering professors Shengjie (Patrick) Zhai and Hui Zhao of UNLV’S College of Engineering designed the testing kits.
The test kits returned to Earth in July for analysis in a UNLV lab. For comparison, similar bacterial specimens grown on Earth will also be tested.
“There are many great oral hygiene products. But if you think about long-term space travel, there’s no guarantee that the Earth methods will work in zero gravity,” said Dr. Jeffrey Ebersole, an immunologist and Associate Dean for Research at UNLV’s School of Dental Medicine and project collaborator.
“This experiment will help push the envelope on understanding how one deals with oral health — both maintaining quality oral care and treating diseases— in space,” he said.
The experiment took two years to organize, from the time in 2019 when Colgate-Palmolive approached UNLV to draft a research proposal on studying oral biofilms (or dental plaque) in the International Space Station. It will be a collaborative work with NASA’s Center for the Advancement of Science in Space.
After a review process, Colgate and NASA accepted the UNLV proposal.
In space, the bacteria will be grown at the average human body temperature of 98.6°F on 5 mm hydroxyapatite chips, a hard substance that resembles the structure of teeth. This is to replicate the way bacteria grow as dental plaque on the surface of teeth.
The microfluidic devices that hold the hydroxyapatite will dispense liquid nutrients needed for bacterial growth over the chips.
Each test will run for 48 hours. It will help researchers evaluate whether space conditions affect the bacteria’s response to microgravity.
The tests will also determine the effects of the treatment agents on bacterial growth and the way they metabolize the nutrients and form biofilms. On Earth, biofilms could impact on gum tissues and tooth enamel.
Each of the 25 kits is organized with color-coded fluid bags and matching tubing, self-contained in 10-inch x 10-inch NASA-approved zip lock bags. This ensures safety for the space crew because the kits require minimal handling by astronauts.
“That was one of the bigger challenges we had: How do we do this outside of our standard lab environment, package it safely, and make it as simple as possible for the crew to conduct the science,” Dr. Ebersole said.
“For example, a liquid drop that escapes in zero gravity floats around with nothing to stop it and could end up in a crew member’s eye, so you had to think through all these different experimental processes.”
Drs. Ebersole and Zhai were in Florida for the launch of SpaceX CRS-22.
Dr. Zhai answered queries from NASA personnel about test kit operations. Dr. Ebersole communicated with astronauts in real-time through video feeds.
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Dr. Joseph D. Lim is the former Associate Dean of the UE College of Dentistry, former Dean of the College of Dentistry, National University, past president and honorary fellow of the Asian Oral Implant Academy, and honorary fellow of the Japan College of Oral Implantologists. Honorary Life Member of Thai Association of Dental Implantology. For questions on dental health, e-mail jdlim2008@gmail.com or text 0917-8591515./PN
