Nanotube Fibers can Bridge Damaged Heart Tissues

A new study has confirmed that thin and flexible fibers composed of carbon nanotubes can bridge damaged heart tissues and provide the electrical signals required to keep those hearts beating.

At Texas Heart Institute (THI), researchers performed several studies in which biocompatible fibers developed at Rice University were used. These studies revealed that when these fibers are directly sewn into the damaged tissue, they helped restore electrical function in hearts.

Instead of shocking and defibrillating, we are actually correcting diseased conduction of the largest major pumping chamber of the heart by creating a bridge to bypass and conduct over a scarred area of a damaged heart.

Dr Mehdi Razavi, Cardiologist and Director of Electrophysiology Clinical Research and Innovations, THI

Dr Razavi co-headed the study with Matteo Pasquali, a chemical and biomolecular engineer at Rice University.

“Today there is no technology that treats the underlying cause of the No. 1 cause of sudden death, ventricular arrhythmias,” Dr Razavi stated. “These arrhythmias are caused by the disorganized firing of impulses from the heart’s lower chambers 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.”

The study results on preclinical models appeared as an open-access Editor’s Pick in the American Heart Association’s journal, Circulation: Arrhythmia and Electrophysiology. The study received a 2015 grant from the American Heart Association.

The new study emerges from the groundbreaking 2013 invention by Pasquali’s laboratory that involved making flexible, conductive fibers from carbon nanotubes. While the initial threadlike fibers developed by the lab measured a quarter of the thickness of a human hair, they contained an unlimited number of tiny nanotubes.

In addition, the fibers are being analyzed for use in cochlear implants, for electrical interfaces with the brain, for aerospace and automotive applications, and as flexible antennas.

The experiments demonstrated that the nontoxic, polymer-coated fibers—with their ends exposed to act as electrodes—effectively restored the function during month-long tests in both rodents and large preclinical models, regardless of whether the initial conduction was blocked, severed, or slowed, stated the scientists. The team also found that the fibers served their purpose either with or without the presence of a pacemaker.

In the rodent study, conduction disappeared once the fibers were removed, the researchers wrote.

The reestablishment of cardiac conduction with carbon nanotube fibers has the potential to revolutionize therapy for cardiac electrical disturbances, one of the most common causes of death in the United States.

Mark McCauley, Co-Lead Author, The University of Illinois College of Medicine

McCauley performed many experiments as a postdoctoral fellow at THI. Currently, he is an assistant professor of clinical medicine at the University of Illinois College of Medicine.

“Our experiments provided the first scientific support for using a synthetic material-based treatment rather than a drug to treat the leading cause of sudden death in the U.S. and many developing countries around the world,” added Razavi.

According to Pasquali, several questions remain before the process can be tested on humans. A method should be established by the researchers that would allow them to sew the fibers in place with the help of a minimally invasive catheter. These fibers should also be sufficiently strong and flexible to serve a continuously beating heart over the long term.

Pasquali further stated that the researchers should also establish the length and width of the fibers, the amount of electricity that needs to be carried by these fibers, and the way they would perform in the developing hearts of young patients.

“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,” stated Pasquali, who has appointments at Wiess School of Natural Scand Rice’s Brown School of Engineering.

Good interfacial contact is also critical to pick up and deliver the electrical signal. In the past, multiple materials had to be combined to attain both electrical conductivity and effective contacts. These fibers have both properties built in by design, which greatly simplifies device construction and lowers risks of long-term failure due to delamination of multiple layers or coatings.

Matteo Pasquali, Chemical and Biomolecular Engineer, Rice University

Razavi observed that while several effective antiarrhythmic drugs are available, they are usually contraindicated in patients following a heart attack.

“What is really needed therapeutically is to increase conduction,” he stated. “Carbon nanotube fibers have the conductive properties of metal but are flexible enough to allow us to navigate and deliver energy to a very specific area of a delicate, damaged heart.”

Co-lead authors of the paper are Rice alumna Flavia Vitale, currently an assistant professor of neurology and of physical medicine and rehabilitation at the University of Pennsylvania, and Stephen Yan, a graduate student at Rice University.

The paper’s co-authors are Julia Coco and Colin Young of Rice University; Brian Greet of THI and Baylor St. Luke’s Medical Center; Marco Orecchioni and Lucia Delogu of the Città della Speranza Pediatric Research Institute, Padua, Italy; Abdelmotagaly Elgalad, Mathews John, Doris Taylor and Luiz Sampaio, all from THI; and Srikanth Perike of the University of Illinois at Chicago.

Pasquali is the A.J. Hartsook Professor of Chemical and Biomolecular Engineering, a professor of materials science and nanoengineering and of chemistry.

The study was supported by the American Heart Association, the Welch Foundation, the Air Force Office of Scientific Research, the National Institutes of Health, and Louis Magne.