Medical

Scientists knit new artery grafts out of collagen and synthetic fibers

Scientists knit new artery gra...
A circular knitting machine creates an artery graft out of a hybrid yarn
A circular knitting machine creates an artery graft out of a hybrid yarn
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A circular knitting machine creates an artery graft out of a hybrid yarn
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A circular knitting machine creates an artery graft out of a hybrid yarn
A microscope image of the hybrid yarn, composed of collagen and synthetic polylactic acid fibers
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A microscope image of the hybrid yarn, composed of collagen and synthetic polylactic acid fibers

Heart attack patients often need replacements for damaged or blocked sections of coronary arteries, which are usually taken from their own leg veins. But in a new proof-of-concept study, scientists knitted a prototype graft out of hybrid synthetic and biological yarn, forming a scaffold for the patients own cells to grow around and repair the artery.

The method of replacing damaged coronary arteries with one from elsewhere in a patient’s body is currently the best option. But not only is it invasive, some patients don’t have viable vessels available. That’s what encouraged the researchers on the new study, from North Carolina State University and Case Western Reserve University, to investigate alternatives.

“There is a need to find an alternative solution for this kind of patient,” says Fan Zhang, first author of the study. “That’s why we’re looking to use tissue-engineered vascular grafts.”

The team combined two types of fibers into one hybrid yarn, and used a circular knitting machine to fashion it into an artery replacement. One fiber was collagen, while the other was a synthetic fiber made of polylactic acid. Together, the finished artery substitute was able to expand and contract just like the real thing.

A microscope image of the hybrid yarn, composed of collagen and synthetic polylactic acid fibers
A microscope image of the hybrid yarn, composed of collagen and synthetic polylactic acid fibers

But it’s not made to be a permanent implant – instead, it’s a scaffold to help the patient’s own cells build a new artery. Those endothelial cells, which normally line the insides of arteries, stick to the scaffold and begin growing.

The collagen helped those cells stick better, with the hybrid yarn increasing cell adhesion by 10 fold at the beginning and boosting the eventual cell population by 3.2 times, compared to a version made only of the synthetic material.

“We’re not designing a prototype that is a ‘final product,’ we’re putting in the ingredients that will allow the patient to heal, and use this construct to heal and function as a coronary artery,” says Martin King, senior author of the study. “The fibers would eventually degrade and be absorbed into the body.”

That includes the synthetic fibers, which become lactic acid, a common chemical in the body that’s well tolerated in low amounts.

The main issue at the moment, the team says, is that the material is too porous in its current form, leading to blood leakage. That’s the first target to tackle for future improvements, before working to get it ready for tests in animals and eventually, humans.

“With this combination of materials, we have been able to balance the mechanical performance with the biological response,” says King. “We were also able to manufacture the prototype graft using high speed textile production machinery, which will facilitate future manufacturing scale-up and translation to a commercial graft and the clinic.”

The research was published in the journal Materials Science and Engineering: C.

Source: NC State University

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