NEW YORK – Through studies on how bubbles form in liquid samples in space and on Earth, University of Notre Dame researcher Tengfei Luo has been developing sample enrichment methods that could be used to aid the early detection of cancers and other diseases.
His team has reported that the approach to sample enrichment could be used to enhance disease detection, cancer diagnosis, and environmental monitoring applications for astronauts and people living on Earth. Because the enrichment effect is greater in the microgravity of space than at labs on the Earth's surface, though, Luo thinks that shipments of droplet-size blood samples could someday be flown to the International Space Station (ISS) or future commercial space stations to screen for, for example, difficult-to-detect biomarkers of asymptomatic cancers.
Luo studies the physics of energy and mass transport at molecular and nano scales through his lab, which has been developing methods of concentrating target substances including DNA and nanoplastic particles onto small areas of testing surfaces so that they can be more easily detected. The team sent a shoebox-sized experiment to the ISS in August aboard a resupply flight, with the results expected to be returned in November. It is the group's third experiment flown on the ISS since 2021.
That study is supported by a $726,000 grant issued in 2022 by the National Science Foundation. In an award abstract, researchers from Luo's lab wrote that the low concentrations of certain biological targets can be difficult to detect in a liquid sample even with the highly sensitive biosensors that have emerged in recent years. They said that those target molecules, however, can be more easily detected by using lasers to heat target sites and create bubbles that collect materials as fluid flows across on the bubble surface.
The bubbles are allowed to cool and shrink, and they leave behind concentrated deposits of various materials including potential biomarkers of disease.
The most recent study involved the use of plasmonic gold nanoparticles as surrogates for biological targets to comply with safety protocols for the space station. He said that his lab is also collaborating with biochemical engineers at Notre Dame on terrestrial studies for the use of the enrichment methods with Raman spectroscopy for the detection of lipids that are released by cancer cells, and those ongoing studies involve finding the limits of detection for that approach.
Prior to Luo's experiments on the ISS, researchers from his lab reported in 2020 in Advanced Materials Interfaces that they used laser-created bubbles and gold nanoparticles to capture and concentrate single-stranded DNA targets on a glass substrate.
Luo said that the results of subsequent studies aboard the ISS showed that larger, longer-lived bubbles could form in microgravity without detaching from a substrate.
"We're using the surface of the bubble as a target collector," he said. "The higher the surface area that we have, then the more of the target that we can collect."
As a result, he thinks that those larger bubbles could be used to aid the identification of smaller concentrations of target substances than is possible with the tests that are typically used within terrestrial labs.
His team reported early this year in the Nature journal NPJ Microgravity that bubbles that were formed on a heated surface aboard the ISS grew far more quickly and reached sizes 10 to 20 times larger on the ISS than in samples on Earth because of the absence in microgravity of thermal convective flow and buoyancy force. In connection with a separate study, his team also wrote in Science Advances that they used lasers to generate bubbles in ocean water samples, concentrate suspended microplastics onto the bubble surface, and deposit those targets onto a substrate for detection and characterization.
Luo said that his research team is already analyzing videos from the third experiment aboard the ISS to understand some interesting bubble formation and fluid flow dynamics. The scientists will also study the volumes of particles that were deposited by the bubbles and the potential to use the methods for more sensitive and efficient biosensing.
Luo acknowledged that the idea of flying samples up to a space station for routine testing might raise some eyebrows, but he thinks that the cost of space-based diagnostic testing would come down if there is a market and a need, especially as the commercial spaceflight industry grows.
"Space can be an integral part of our daily life," he said.