Using Microparticles to Measure Oxygen in Tissues

By | July 28, 2019

The field of tissue engineering is rapidly progressing, in large part thanks to hydrogel scaffolds that provide a comfortable home for new cells. A major issue that researchers bump against is tracking how well oxygen reaches freshly grown cells within such scaffolds, which can indicate how well the new cells are generally functioning.

Now, researchers at Rice University have developed special microparticles, that are soft and non-toxic to living cells, that glow in relation to how oxygenated their environment is. These microparticles are particularly well suited to measuring oxygen within three-dimensional structures, such as hydrogels because they’re relatively bright and can be seen from outside such constructs.

The particles include a fluorescent molecule, containing palladium and a reference fluorophore, that works in the presence of oxygen. They also have a good deal of dye added, since the fluorescent molecules aren’t bright enough for imaging through tissue. “The problem with using oxygen-responsive fluorophores in three-dimensional cultures is their signal isn’t bright enough to measure reliably,” said Reid Wilson, the lead author of the study appearing in journal ACS Biomaterials Science & Engineering. “So we loaded the microparticles with high concentrations of dye, which allowed more reproducible measurements of the oxygen concentration.”

When the researchers placed the new microparticles along with living cells inside hydrogel structures, they showed that the cells were unaffected and continued prospering. When they tested the oxygen measuring properties of the microparticles, the team was able to detect their fluorescent glow as deep as two millimeters below the surface, an impressive achievement. “That’s small, but oxygen diffusion limits are usually tiny,” said Jane Grande-Allen, in whose lab the research was conducted. “Some cells are quite close to a blood supply, with a high oxygen level brought in by blood cells with hemoglobin. But some bacteria in the microbiome are normally anaerobic and survive better without oxygen.” The microparticles are able to remain stable within the hydrogels and continue working over long periods of time.

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Though the technology is designed for use in growing new tissues, it may help researchers to understand how native tissues, such as cartilage, are able to obtain enough oxygen without the presence of nearby blood vessels.

Study in ACS Biomaterials Science & Engineering: Monitoring oxygen levels within large, tissue-engineered constructs using porphyin-hydrogel microparticles.

Via: Rice University