Rice University and Texas Heart Institute: Damaged Hearts Rewired with Nanotube Fibers

Today we want to share the following press release from Rice University in order to shine a spotlight on a newly-published paper about an exciting medical application of carbon nanotube fibers! This work was done by a collection of researchers at Rice University and the Texas Heart Institute in Houston, the University of Illinois at Chicago, and the Città della Speranza Pediatric Research Institute in Padua, Italy. Rice alumnus Colin Young, one of the co-authors on the paper, is currently a member of the DexMat team!

Damaged hearts rewired with nanotube fibers

Texas Heart doctors confirm Rice-made, conductive carbon threads are electrical bridges

HOUSTON – (Aug. 13, 2019) – Thin, flexible fibers made of carbon nanotubes have now proven able to bridge damaged heart tissues and deliver the electrical signals needed to keep those hearts beating.

Scientists at Texas Heart Institute (THI) report they have used biocompatible fibers invented at Rice University in studies that showed sewing them directly into damaged tissue can restore electrical function to hearts.
Rice University Professor Matteo Pasquali, left, and Dr. Mehdi Razavi of the Texas Heart Institute check a thread of carbon nanotube fiber invented in Pasquali's Rice lab. They are collaborating on a method to use the fibers as electrical bridges to restore conductivity to damaged hearts. (Credit: Texas Heart Institute)

Rice Professor Matteo Pasquali, left, and Dr. Mehdi Razavi of the Texas Heart Institute check a thread of carbon nanotube fiber invented in Pasquali’s Rice lab. They are collaborating on a method to use the fibers as electrical bridges to restore conductivity to damaged hearts. Courtesy of the Texas Heart Institute

“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,” said Dr. Mehdi Razavi, a cardiologist and director of Electrophysiology Clinical Research and Innovations at THI, who co-led the study with Rice chemical and biomolecular engineer Matteo Pasquali.

“Today there is no technology that treats the underlying cause of the No. 1 cause of sudden death, ventricular arrhythmias,” Razavi said. “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.”

Results of the studies on preclinical models appear as an open-access Editor’s Pick in the American Heart Association’s Circulation: Arrhythmia and Electrophysiology. The association helped fund the research with a 2015 grant.

The research springs from the pioneering 2013 invention by Pasquali’s lab of a method to make conductive fibers out of carbon nanotubes. The lab’s first threadlike fibers were a quarter of the width of a human hair, but contained tens of millions of microscopic nanotubes. The fibers are also being studied for electrical interfaces with the brain, for use in cochlear implants, as flexible antennas and for automotive and aerospace applications.

The experiments showed the nontoxic, polymer-coated fibers, with their ends stripped to serve as electrodes, were effective in restoring function during monthlong tests in large preclinical models as well as rodents, whether the initial conduction was slowed, severed or blocked, according to the researchers. The fibers served their purpose with or without the presence of a pacemaker, they found.
(Credit: James Philpot/Texas Heart Institute)

Illustration by James Philpot/Texas Heart Institute

In the rodents, they wrote, conduction disappeared when the fibers were removed.

“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,” said co-lead author Mark McCauley, who carried out many of the experiments as a postdoctoral fellow at THI. He is now 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,” Razavi added.

Many questions remain before the procedure can move toward human testing, Pasquali said. The researchers must establish a way to sew the fibers in place using a minimally invasive catheter, and make sure the fibers are strong and flexible enough to serve a constantly beating heart over the long term. He said they must also determine how long and wide fibers should be, precisely how much electricity they need to carry and how they would perform in the growing hearts of young patients.
Researchers at Texas Heart Institute and Rice University have confirmed that flexible, conductive fibers made of carbon nanotubes can bridge damaged tissue to deliver electrical signals and keep hearts beating despite congestive heart failure or dilated cardiomyopathy or after a heart attack. (Credit: Texas Heart Institute)

Researchers at Texas Heart Institute and Rice University have confirmed that flexible, conductive fibers made of carbon nanotubes can bridge damaged tissue to deliver electrical signals and keep hearts beating despite congestive heart failure or dilated cardiomyopathy or after a heart attack. Courtesy of the Texas Heart Institute

“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,” said Pasquali, who has appointments at Rice’s Brown School of Engineering and Wiess School of Natural Sciences.

“Good interfacial contact is also critical to pick up and deliver the electrical signal,” he said. “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.”

Razavi noted that while there are many effective antiarrhythmic drugs available, they are often contraindicated in patients after a heart attack. “What is really needed therapeutically is to increase conduction,” he said. “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.”

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

Co-authors are Colin Young and Julia Coco of Rice; 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 of 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 American Heart Association, the Welch Foundation, the Air Force Office of Scientific Research, the National Institutes of Health and Louis Magne supported the research.

Read the paper at https://www.ahajournals.org/doi/full/10.1161/CIRCEP.119.007256

This news release can also be found online at https://www.texasheart.org/news/ and https://news.rice.edu/2019/05/29/damaged-hearts-rewired-with-nanotube-fibers/

 

Source: Rice University News & Media

Carbon nanotube yarn taps nerves for electroceutical treatments and diagnostics

(Nanowerk News) Ingested or injected pharmaceuticals can target specific molecules involved in disease processes, but get distributed throughout the body where they can cause unwanted side effects. An approach known as electroceuticals aims to avoid systemic exposure by using small wires to electrically monitor and manipulate individual nerves that control organ function and carry information about disease. Despite the promise of electroceuticals, it has been challenging to develop long-term therapies due to the lack of biocompatible wires.
Now, NIBIB-funded researches have spun carbon nanotubes into flexible, nerve-sized wires or yarns capable of high-fidelity long-term connections in live animals. The development of these biocompatible yarns opens the possibility of new bioelectric diagnostics and therapies through regulation of internal organ function at the single nerve level.
Individual carbon nanotubes are pulled from a substrate and spun into the flexible carbon nanotube yarn
Individual carbon nanotubes are pulled from a substrate and spun into the flexible carbon nanotube yarn. (© NPG)
All the organs of the body such as the heart, lungs, liver, and kidneys are automatically controlled by nerves that stretch from the brainstem to each organ. These nerves control organ functions such as heartbeat, breathing rates, and blood pressure, making constant adjustments in response to environmental and physiological changes. Variations in the electrical activity in this area of the brain, known as the autonomic nervous system, can also be predictors, indicators or causes of disease development.
“Monitoring and manipulating the autonomic nervous system to both understand and potentially treat disease has been an intriguing yet understudied approach to medicine,” explains Michael Wolfson, Ph.D., director of the NIBIB program in Rehabilitation Engineering and Implantable Medical Devices. “This is largely due to technical limitations in being able to insert wires into nerves that can reliably and safely record electrical activity over long periods of time and under different physiological conditions.”
In a study reported in the journal Scientific Reports (“Chronic interfacing with the autonomic nervous system using carbon nanotube (CNT) yarn electrodes”), bioengineers at Case Western Reserve University in Cleveland, Ohio describe the development of highly flexible carbon nanotube (CNT) yarn electrodes that were capable of months-long electrical recording in major nerves of the autonomic nervous system in rats.
The CNT yarns are essentially, just that, yarns made from a “forest” of hundreds of carbon nanotubes that are pulled from the metal surface they are grown on and spun into a highly flexible, highly conductive wire 1/100th the size of a human hair.
carbon nanotube yarn is wound around a tungsten needle for insertion into a nerve
The carbon nanotube yarn is wound around a tungsten needle for insertion into a nerve. The coiling of the yarn causes it to remain solidly embedded in the nerve after the needle is withdrawn. Actual needle and yarn (top). Diagram showing detail of how yarn is wrapped around the needle for insertion (bottom). (© NPG)
Current technologies for recording electrical signals from nerves include relatively large stiff tungsten needles used by neurologists to obtain readings from single nerves of patients for several hours, but must be removed before causing lasting nerve damage. Other wire electrode technologies can record nerve signals for short periods but because of their dimensions and stiff mechanical properties they are not suitable for long-term recording in small nerves.
“The currently available electrode technologies simply do not match the mechanical properties of nerves,” explains Dominique Durand, Ph.D., Professor of Biomedical Engineering at Case Western and senior researcher on the CNT yarn work. “With those types of electrodes, it’s often like sticking glass into spaghetti. Our CNT yarns are similar in size and flexibility to actual nerves. These properties allow them to be stealthily inserted into specific nerves and remain there for months without destroying the tissue or inducing an attack by the immune system.”
The combination of the biocompatibility of the CNT yarns and their outstanding ability to carry an electrical signal that is 10 times stronger than current technologies makes them ideal for long term recording of specific nerve signals. Finally, the lack of nerve damage keeps the surrounding axons intact, which helps to eliminate background noise. Thus, the CNT yarns have an excellent signal to noise ratio (SNR), which is critical for this type of research.
The group tested the CNT yarns in two major nerves in the autonomic system in rats. One study involved the vagus nerve, which stretches throughout the body to connect to numerous organs. The nerve is known to control and monitor a range of functions including heart rate, digestive tract movement, sweating, and immune response.
CNT yarn electrodes were also inserted into the glossopharyngeal nerve. The nerve is connected to a number of organs including the carotid artery, and parts of the ear, tongue and salivary glands where it is known to be involved in swallowing.
Carbon nanotube yarn embedded into the vagus nerve of a rat
Carbon nanotube yarn embedded into the vagus nerve of a rat. (© NPG)
In both nerves, recordings of stable electrical activity were maintained over a 10-week period. Pulses of nerve activity were also monitored while the animal responded to physiological challenges. The challenges included distension of the rat’s stomach with saline solution, and short durations where the rats were in low oxygen environments. In each case, the physiological changes induced by the challenge resulted in easily detectable changes in electrical activity that were recorded using the CNT yarn implants over the entire 10-week period of the experiments.
“Although this is early research, we believe the results demonstrate that this technology can be used for reliable long term electrical monitoring of physiological functions,” says Durand. “This is an important step in pursuing monitoring of disease progression through the nerves that control the function of the diseased organ.”
Durand explains that the goal is to learn what electrical signatures or profiles are indicative of disease development and to use that for early intervention, potentially by electrical stimulation or even blocking of the nerve. For example, one therapy for severe hypertension is the cutting of the renal nerve. This is obviously irreversible. Durand, explained that CNT yarn electrodes could be used to block the nerve impulse without cutting the nerve, making the treatment reversible.
The group is also excited about the potential of this recording method to improve prosthetics. “When an arm has been amputated there are tens of thousands of neurons remaining,” said Durand. “The approach would be to insert the CNT yarns into individual nerves and record the electrical signals that are created as the individual thinks about moving the missing arm—essentially learning the electrical signals that are formed by the intention to move the arm.” The ultimate goal is to develop neural interfaces capable of translating those electrical signals into better control of the prosthetic by the user.
Source: National Institute of Biomedical Imaging and Bioengineering

Gamma-ray shielding performance of carbon nanotube film material

This paper aims to explore the shielding potential of light-weight carbon nanotube (CNT) film materials against gamma-ray generated from americium-241 (241Am) and caesium-137 (137Cs). The influence factors of gamma mass attenuation coefficient of CNT film laminates were investigated to reveal structure-property relationship. The results showed that CNT film materials had bigger mass attenuation coefficients than carbon fiber reinforced composites, suggesting stronger radiation interaction induced by CNT’s cylindrical nanostructure. CNT alignment was proved to be conducive to the improvement of mass attenuation coefficient and gamma attenuation ratio. Aligned CNT film laminate with the thickness of 10 mm had a mass attenuation coefficient of 0.086 cm2 /g and attenuation ratio of 4.9% against gamma-ray exposed to 137Cs, which were higher than those of aluminum, iron or copper sheets. CNT film material demonstrated its potential for the application of light-weight gamma-ray safety equipment and devices.

Download full paper at: https://houstontx.library.ingentaconnect.com/content/asp/me/2016/00000006/00000005/art00010