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Electrical response overlaid on the inner aortic wall. Image: Jiangy Li, University of Washington
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The heart's inner workings are mysterious, perhaps even more
so with a new finding. Engineers at the University of Washington
have discovered an electrical property in arteries not seen before in mammalian
tissues.
The researchers found that the wall of the aorta, the largest
blood vessel carrying blood from the heart, exhibits ferroelectricity, a
response to an electric field known to exist in inorganic and synthetic
materials. The findings are being published in Physical Review Letters.
"The result is exciting for scientific reasons," said lead
author Jiangyu Li, a UW associate professor of mechanical engineering. "But it
could also have biomedical implications."
A ferroelectric material is an electrically polar molecule
with one side positively charged and the other negatively charged, whose
polarity can be reversed by applying an electrical field.
Ferroelectricity is common in synthetic materials and used for
displays, memory storage, and sensors. (Related research by Li and colleagues
seeks to exploit ferroelectric materials for tiny low-power, high-capacity
computer memory chips.)
In the new study, Li collaborated with co-author Katherine
Zhang at Boston University to explore the phenomenon in
biological tissues. The only previous evidence of ferroelectricity in living
tissue was reported last year in seashells. Others had looked in mammal tissue,
mainly in bones, but found no signs of the property.
The new study shows clear evidence of ferroelectricity in a
sample of a pig aorta. Researchers believe the findings would also apply to
human tissue.
In subsequent work, yet to be published, they divided the
sample into fibrous collagen and springy elastin and studied each one on its
own. Pinpointing the source of the ferroelectricity may answer questions about
how or whether it plays a role in the body.
"The elastin network is what gives the artery the mechanical
property of elasticity, which of course is a very important function," Li said.
Ferroelectricity may therefore play a role in how the body
responds to sugar or fat.
Diabetes is a risk factor for hardening of the arteries, or
atherosclerosis, which can lead to heart attack or stroke. The team is
investigating the interactions between ferroelectricity and charged glucose
molecules, in hopes of better understanding sugar's effect on the mechanical
properties of the aortic walls.
Another possible application is to treat a condition in which
cholesterol molecules stick to the inside of the channel, eventually closing it
off.
"We can imagine if we could manipulate the polarity of the artery
wall, if we could switch it one way or the other, then we might, for example,
better understand the deposition of cholesterol which leads to the thickening
and hardening of the artery wall," Li said.
He cautions that medical applications are still speculations,
and require more research.
"A lot of questions remain to be answered, that’s an exciting
aspect of the result," Li said.
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