So why are researchers from Vanderbilt University spending their time messing about with cotton candy and jello molds? Because, as it turns out, these tools may be our best shot at solving the problem.
One of the bottlenecks that exist with building functioning organs is that cells need to be roughly within a hair’s thickness of a blood vessel to get the nutrients that they need. Put them too far away from a supply of oxygenated blood and they will die. What this means is that if you want to build tissue that is thicker than a human hair, you need to build in artificial vasculature which can provide all the cells in a tissue with the nutrients and oxygen that they need.
The smallest blood vessels are called capillaries, fine branching blood vessels which make up a complex network between arterioles and venules. The size of a capillary? Around 10 times smaller than a human hair.
That is no good for 3D printing, which is often considered the answer for regenerative medicine thanks to the enormous possibilities of bioprinting. “3D printing certainly has its place for larger features, but I’m not aware of a 3D printing approach that’s able to produce features on the capillary scale in 3D,” Dr. Leon Bellan told Digital Trends.
What he and colleague Hak-Joon Sung have come up with is a novel method of “spinning” capillary-sized polymer fibers using a regular cotton candy machine.
“It turns out that if you take a cotton candy machine and spin fibers from it, that fibrous mesh contains three-dimensional fibers which are roughly 10 times thinner than a human hair,” Bellan continued. “It’s very hard to pattern something at that scale and with that complexity using a 3D printer.”
In terms of where the jello mold comes into play, Bellan said that the polymer fibers are next hardened in a jelly-like material called hydrogel and then dissolved away, leaving just the capillary-style chambers themselves for cells to grow around.
“Getting cotton candy inside hydrogel is somewhat difficult, but it’s important because it’s most similar to the natural cellular matrix that cells like to live in,” he said. “We’ve spent a lot of time working out how to put cotton candy inside of a jello mold. To do this, we now don’t make the cotton candy from sugar, but instead materials that don’t dissolve in hot water but only in cold water. By playing games with the temperature we were able to achieve our goal.”
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