Cardiac arrhythmias are heart rhythm disturbances that occur because the heart beats too fast or too slow. Their prognosis is generally good, but they can become complicated and lead to heart failure, a stroke, or even sudden death. To treat arrhythmia, a pacemaker can be placed that detects if the heartbeat is not normal and corrects the rhythm with electrical stimulation. Now, a new graphene heart implant that incorporates major improvements could replace the pacemaker.
Graphene is a two-dimensional super material and extremely strong, very light and with conductive properties, while the pacemaker is rigid and can limit the natural movements of the heart, damage soft tissues, cause discomfort from time to time and cause some complications, such as blood clots, swelling with pain, perforations or infections, among others.
A team of scientists led by researchers from the University of Texas at Austin and Northwestern University have developed the implantable derivative of graphene-based wearable electronic tattooing, or e-tattoo: the graphene biointerface, which has become the world’s thinnest heart implant. until now and that, in addition, is transparent, which allows an external optical light source to be used to record and stimulate cardiac activity.
“The graphene tattoo is compatible with the human body, light and transparent, making it a more natural solution for people with heart problems”
The researchers carried out tests to verify that the graphene tattoo was able to detect irregular heart rhythms and emit pulses to generate electrical stimulation without limiting or altering the natural movements of the heart. “It is very exciting to harness our electronic tattoo technology for use as an implantable device inside the body,” said Dmitry Kireev, a postdoctoral research associate in Professor Deji Akinwande’s lab at UT Austin. “The fact that it is much more compatible with the human body, light and transparent, makes this a more natural solution for people with heart problems.”
Graphene: a biocompatible material with the heart
The new implant resembles the stickers or temporary tattoos children get and is thinner than a hair. It is biocompatible and, being so thin and flexible, it conforms to the contours of the heart, but it is also strong and elastic enough to withstand its beating.
“One of the challenges for current pacemakers and defibrillators is that they are difficult to place on the surface of the heart,” said Northwestern’s Igor Efimov, professor of biomedical engineering in the McCormick School of Engineering and co-leader of the study. “Defibrillator electrodes, for example, are essentially coils made of very thick wires, which are not flexible and break. Rigid interfaces with soft tissues such as the heart can cause various complications. By contrast, our soft, flexible device is unobtrusive and fits seamlessly directly over the heart to provide more precise measurements.”
Efimov and his colleagues’ goal was to develop a biocompatible device ideally suited to adapt to soft and dynamic tissues. After evaluating various materials, they chose graphene, an atomically thin form of carbon. The biocompatibility of graphene makes it especially interesting for medical purposes. “Carbon is the basis of life, so it is a safe material that is already used in various clinical applications. It is also flexible and smooth, which works well as an interface between electronics and a smooth, mechanically active organ,” says Efimov.
Akinwande and his team had spent years developing graphene electronic tattoos, which had different functions, such as monitoring body signals. Flexible and weightless, the electronic tattoos they have created adhere to the skin to continuously monitor vital signs, including blood pressure and the electrical activity of the brain, heart and muscles.
However, it is one thing to place them on the skin, and another inside the body, so the researchers developed a completely new technique. First, they encapsulated the graphene inside a flexible, elastic silicone membrane, with a hole drilled to give access to the graphene electrode inside. They then placed gold tape (with a thickness of 10 microns) over the encapsulation layer to serve as the electrical interconnect between the graphene and the external electronics used to measure and stimulate the heart. Finally, they placed it over the heart. The total thickness of all the bonded layers is around 100 microns.
This new device was stable for 60 days with an actively beating heart at body temperature, which is equivalent to the duration of temporary pacemakers used to transition to permanent pacemakers or rhythm control after surgical intervention or other therapies.
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