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Heart attacks are a devastating occurrence. Each year,
approximately 1.5 million heart attacks occur in the United States and cause 500,000
deaths. A new technology, developed by researchers at MIT and Children's
Hospital Boston, could someday help these millions of sufferers.
A heart attack occurs when blood flow to part of the heart is blocked long enough to cause part of the heart muscle to become
damaged or die.
Heart Attack.
Image Credit: MedicineNet.com
The new nano-technology is a cardiac patch studded with
tiny gold nanowires. The patch is used to help create pieces of tissue where
the cells all beat in time, mimicking the dynamics of natural heart muscle. This
product could also be used to help other types of tissues - such as muscles,
vascular tissues and neurons - to heal and grow.
Current cardiac patches have difficulty achieving enough
conductivity to ensure a smooth, continuous "beat" throughout the whole piece
of tissue. Duke University has created a stem-cell-based heart patch which has
successfully grown and seeded heart cells (cardiomyocytes), but it blocks the
electrical signals shared by calcium ions that dictate when the cells contract.
Without a uniform beat, the tissue won't grow or function properly.
Daniel Kohane, a professor
in the Harvard-MIT Division of Health Sciences and Technology (HST) and senior author of the paper
published in the journal Nature Nanotechnology, describes the heart as a sophisticated piece of electrical machinery.
Click here to watch a video: New cardiac patch uses gold nanowires to enhance
electrical signaling
The Discovery
New tissue is regenerated using a miniature scaffold made
of a porous material so that the cells can grow into a specific shape. The
scaffold materials being used in research now are materials like polylactic
acid or alginate. These materials are insulators, which prevent cardiomyocytes
from receiving the needed electrical signals to coordinate their movement. This
patch is made of a new scaffold material that allows electrical signals to pass
through.
The material is made of a base alginate, an organic
gum-like substance often used for tissue scaffolds, and a solution containing
gold nanowires, which are 1mm long (diameter 30nm). The solution creates a
composite scaffold with billions of tiny metal structures running through it. The nanowires are able to bridge the pores of
the alginate and improve electrical communication between adjacent
cardiomyocytes. "In healthy, native
heart tissue, you're talking about conduction over centimeters," Timko says.
Previously, tissue grown on pure alginate showed conduction over only a few
hundred micrometers, or thousandths of a millimeter. But the combination of
alginate and gold nanowires achieved signal conduction over a scale of "many
millimeters," Timko says.
A wider SEM
image of the nanowire-alginate composite scaffolds.
Image courtesy of the Disease Biophysics Group, Harvard University
A Heart of Gold
Scientists had to first grow the nanowires and then the
heart cells to test the new machine. Heart cells are hard to grow in a lab
because they must develop the proper beating motion. So researchers collected cardiomyocytes
from rat embryos and seeded them on to the alginate. The calcium levels were labeled
so their electrical conductivity could be monitored. Scientists looked at the amount
of calcium present in different areas of the tissue to determine if there was
an electrical signal. Compared to a
typical scaffold system, the gold nanowire cells' conductivity improved by
three orders of magnitude. Kohane said it was "night and day." Over
time, the scaffold degrades and the nanowires are left embedded within the new
tissue.
The next step is for researchers to do in vivo studies to
observe the composite - grown tissue function when implanted into live hearts.
Future research will look at applying the technology into other cellular systems.
Resources
http://www.allheartattack.com/statistics.php
http://www.rsc.org/chemistryworld/News/2011/September/27091101.asp
http://web.mit.edu/newsoffice/2011/gold-nanowire-heart-0926.html
http://www.ncbi.nlm.nih.gov/pubmedhealth/PMH0001246/
http://www.innovationnewsdaily.com/nanowire-heart-of-gold-cardiac-victims-2280/
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