As the famous TV ad said, four out of five dentists recommend Colgate toothpaste … on Earth. But, what about in space?
Researchers from UNLV’s College of Engineering and School of Dental Medicine have teamed with NASA and Colgate-Palmolive to find out just how effective the personal care brand’s oral health products might be on periodontal disease or cavity-causing bacteria growing in the mouths of Earthlings working — and maybe even one day living — among the cosmos.
On June 3, an International Space Station-bound rocket, SpaceX CRS-22, will blast off from Cape Canaveral, Fla. carrying on board oral bacteria and saliva gleaned from the mouths of 30 UNLV dental clinic patients contained in 25 kits developed by UNLV engineers. These kits, which contain 3D-printed, battery-powered microfluidic pump devices, will test the germs’ growth and treatment with Colgate toothpastes, mouthwashes, and other disease-fighting products. The test kits will be returned in July for analysis in a UNLV lab alongside similar bacterial specimens grown on Earth for comparison purposes.
“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 project collaborator Jeffrey Ebersole, an immunologist and associate dean for research at UNLV’s School of Dental Medicine. “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.”
The project has been two years in the making and, like many things of late, was temporarily stalled and continually challenged in development by the COVID-19 pandemic.
In 2019, Colgate-Palmolive, working in conjunction with NASA’s Center for the Advancement of Science in Space, approached UNLV about growing oral biofilms on the International Space Station. The UNLV researchers’ proposal was accepted by Colgate and NASA following a rigorous review process and development phase that was made lengthier by pandemic restrictions that slowed the acquisition of U.S. and overseas parts needed for fabrication and development. What’s more, university scientists, Colgate microbiologists, and a payload implementation team from Teledyne-Brown Engineering were unable to conduct onsite office and lab work for months.
However, UNLV engineering professors Shengjie (Patrick) Zhai and Hui Zhao, who designed the testing kits — which include 3D-printed components — say it was worth the wait. They believe the multi-channel microfluidic devices are the first such instruments that both operate automatically without human intervention (via battery power) and dispense fluids at an ultra-low flow rate, which mimic conditions that would occur inside the human mouth.
How It Works
UNLV dental clinical researchers, Dr. John Gallob and Lacey Rahmig, collected saliva and three different kinds of bacteria — microbes that constitute a healthy oral environment, as well as germs that cause cavities and gum disease — from the mouths of 30 Las Vegas patients.
On Earth, bacteria in our mouths grow attached to the surface of our teeth (that’s why you brush and floss — to remove the accumulated bacteria, more commonly known as plaque). On the space station, 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. The microfluidic devices designed by UNLV Engineering will hold the hydroxyapatite and allow liquid nutrients needed for bacterial growth to continuously flow over the chips. Each test will run for 48 hours, and help researchers evaluate whether conditions in space impact the bacteria’s response to the microgravity environment, as well as the effect of the treatment agents to block the bacteria’s abilities to metabolize the nutrients and form biofilms that could destroy gum tissues and tooth enamel.
In order to ensure safety among and easy manipulation by the space crew, 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, and requires 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,” 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.”
Up, Up, and Away
Both Ebersole and Zhai are traveling this week to Florida to be on site for the launch of SpaceX CRS-22.
Zhai is excited about the potential for the project to attract young future scientists. He will be on hand to answer NASA personnel questions about test kit operations. Throughout the week, Ebersole — who has enjoyed his crash course in space radio traffic lingo — will be available at odd hours (the flight crew operates on Greenwich Mean Time) to communicate with astronauts in real-time through video feeds from the space station as they work through the experiments.
For these two UNLV scientists, the project represents dreams coming true for society, and themselves.
“Along with firefighter and dinosaur hunter, astronaut seems to be on every child’s list of dream jobs,” Zhai said. “Now, my astronaut dream has come true in another way."