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Nanotube Fibers Configured for Heart Repair

Inspecting a fiber

Matteo Pasquali, left, and Mehdi Razavi inspect a spool of carbon nanotube fiber. (Texas Heart Institute)

14 Aug. 2019. Medical and engineering researchers developed fibers made with nanoscale carbon tubes that in lab animals conducted electrical signals and repaired heart damage. A team from Texas Heart Institute and Rice University in Houston describe their findings with the fibers in the 12 August issue of the journal Circulation: Arrhythmia and Electrophysiology.

The biocompatible fibers are a result of work by electro-physiologist Mehdi Razavi at Texas Heart Institute and engineering professor Matteo Pasquali at Rice University. The researchers are seeking better treatment methods for ventricular tachycardia, arrhythmias or irregular heart rhythms caused by abnormal electrical signals from the ventricles, the lower chambers of the heart. Current treatments use implanted defibrillators, drugs, or ablation that can improve heart pacing, but do not address the slowing heart beat velocity. And more recent advances with stem cells and gene therapy are still in very early stages.

The team’s solution is fibers made of nanoscale carbon tubes with a protective polymer coating, developed in Pasquali’s lab, used like sutures to repair damaged heart tissue. The carbon nanotubes carry electrical signals, with the polymer coating stripped off the ends allowing them to act like electrodes.

“These arrhythmias are caused by the disorganized firing of impulses from the heart’s lower chambers,” says Razavi in a joint statement, “and are challenging to treat in patients after a heart attack or with scarred heart tissue due to such other conditions as congestive heart failure or dilated cardiomyopathy.” Pasquali adds that the flexibility of the fibers make them good candidates for this task. “Flexibility is important because the heart is continuously pulsating and moving, so anything that’s attached to the heart’s surface is going to be deformed and flexed.”

The researchers tested the fibers in sheep, whose hearts are similar in size and function to humans, induced with abnormal heart rhythms. The results show that sheep with the carbon nanotube sutures improved their heart rhythms, compared to similar sheep using silk sutures, and maintained normal rhythms for a month.

The team also tested the carbon nanotube fibers on mice and rats induced with both acute heart damage, such as a heart attack, and chronic heart disorders. The results show the carbon nanotube sutures restored normal heart pacing in rodents with both acute and chronic heart conditions, although animals with chronic heart disorders also required pacemakers. Postmortem tests with the mice and rats show no evidence of toxicity from the fibers.

While the animal tests are encouraging, the authors note that techniques are needed, such as insertion or implantation by minimally-invasive catheters, are still needed before carbon nanotube fibers can be tested in humans. Several authors filed for a patent on the carbon nanotube technology, and started the company NanoLinea Inc. in Houston to take it to market. Colin Young, a co-author of the paper is NanoLinea’s CEO.

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