What’s he building in there?
EVERY CELL THAT makes up our body carries genetic information needed to create a human being. Before birth, those cells become specialized—some cells are blood cells, some are kidney cells, some are neurons, and some are stem cells that have the freedom to become any cell the body needs.
Cellular signalling summons stem cells to injuries, but doesn’t completely control the type of cell they turn into. The local environment plays a part in the process, deciding what the stem cells will become. Temperature, acidity, and material properties of the injury are essential to the stem cells. They will act differently whether the site is stiff, elastic, or immersed in a bodily fluid. Adding to the complexity, unless it’s blood or bone, our body’s contents are not pure solid or liquid—they’re something in-between, like jello or honey.
Shane Scott, a master’s student in the physics department at the Univeristy of Ottawa, studies the properties of these complex fluids. He is a rheologist—he studies materials that both stretch and flow, like gels or molasses.
To make stem cells in a lab, you grow them in protein gel. This gel can mimic the properties of different parts of the body. The gel is easy to tweak, and scientists like Scott can add binding domains that act like docking bays for cells to attach to, making them perfect cellular scaffolds.
The behaviour of those cells depends on the rheological properties of the gel, making it necessary to categorize the gel before you start growing cells.
Scott’s proteins are random coils with a helix cap at both ends, which means when he mixes these proteins into a solution, the coils tangle together and form a gel. If he wants a more permanent gel, Scott chemically links the proteins into a network.
Scott characterized protein gels that were part physically tangled and part chemically linked for different temperatures, acidity, and concentrations. Scott showed when a binding domain was added to the gel to turn it into a cellular scaffold, the rheological properties didn’t change, meaning biologists don’t have to worry about stem cells behaving differently because making a protein gel into a cellular scaffold altered their environment.
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