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September 1, 2006 Vol.77, no. 3F
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| NANOENGINEERING: BioE
graduate student Craig Hashi (left) and assistant professor
Song Li with a nanograft. PEG
SKORPINSKI PHOTO
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Architects of arterial scaffolding
BioE researchers use tissue engineering
to combat heart disease.
BioE Ph.D. student Craig Hashi understands the heart of the matter: Cardiovascular disease is the number one killer in the United States, according to the American Heart Association. To treat serious cases of it, Hashi explains, surgeons graft a blood vessel around the blocked one, allowing the blood to flow freely again via the new path. In the United States, more than half a million coronary bypass surgeries are performed each year.
However, the procedure isn’t without problems. In many cases, surgeons use a replacement vein or artery harvested from another part of the body. But — especially in patients needing multiple grafts — there is a limited availability of such vessels and a 40 percent or more failure rate within 10 years. In other cases, surgeons use synthetic vascular grafts, but only to replace veins with inside diameters of five millimeters or larger because smaller ones invite complications such as thrombosis, or clotting and obstruction of a blood vessel.
Hashi and his team, led by BioE assistant professor Song Li, have a better solution: Help the body build itself a new blood vessel through tissue engineering. “We’ve developed a combination of technologies called nanografts that, when inserted into the body, essentially remodel and integrate themselves,” Hashi explains. They provide a structure for the body to grow a new vein, he says.
This little bit of biological magic begins with the team’s technique for producing nanofibrous scaffolding, which becomes the vessel’s foundation. “The nanofibers are made from polymer and spun into sheets, somewhat like a spider’s web,” Hashi says.
The next step is key. Hashi seeds the sheets with adult stem cells harvested from the patient. The stem cells take the form of whatever environment they’re in, stimulating native cell infiltration into the graft and aren’t rejected from the host. The stem cells make the nanografts possible, enabling the body to accept the graft as its own. Then Hashi rolls the sheet around a rod, much like rolling pie dough around a rolling pin. Take out the rod, and voila! a ready-to-graft tube. Once in place, the graft slowly biodegrades while the body remodels the nanograft to form a blood vessel. Patients end up with a natural replacement.
The beauty of nanografts and what makes them different from competitors, says Hashi, is their customizability. They’re made for each patient, but at a reasonable cost, just $200 per graft. That’s a bargain compared to the cost of the second surgery that would be needed to harvest a replacement vein. With baby boomers aging, the market can only grow.
All signs point to success. Results from a year’s worth of testing in rats show great promise, the team says, and plans are in the works for large animal testing with the hope of moving into clinical trials in the next couple years. The team has applied for a patent, put together a business plan and christened itself NanoGraft Technologies. And it’s already received accolades. It recently won first place in the national Biomedical Engineering Innovation, Design and Entrepreneurship Award Competition and walked away with a $10,000 cash prize.
For more on Song and Hashi’s work, go to http://ctelab.berkeley.edu/.
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