Researchers in the US have developed the first cardiac implant made from graphene – a two-dimensional super material with ultra-strong, lightweight and conductive properties.
Similar in appearance to a child’s temporary tattoo, the new graphene “tattoo” implant is thinner than a single strand of hair but still functions just like a classical pacemaker.
Senior author Igor Efimov, professor of biomedical engineering at Northwestern University’s McCormick School of Engineering and professor of medicine at Northwestern University Feinberg School of Medicine, said:
“One of the challenges for current pacemakers and defibrillators is that they are difficult to affix onto the surface of the heart.
“Defibrillator electrodes, for example, are essentially coils made of very thick wires.
“These wires are not flexible, and they break. Rigid interfaces with soft tissues, like the heart, can cause various complications.
“By contrast, our soft, flexible device is not only unobtrusive but also intimately and seamlessly conforms directly onto the heart to deliver more precise measurements.”
After implanting the device into a rat model, the researchers demonstrated that the graphene tattoo could successfully sense irregular heart rhythms before delivering electrical stimulation through a series of pulses without constraining or altering the heart’s natural motions.
The technology also is optically transparent, allowing the researchers to use an external source of optical light to record and stimulate the heart via the device, which is the thinnest known cardiac implant to date.
The researchers developed an entirely new technique to encase the graphene tattoo and adhere it to the surface of a beating heart.
Firstly, they encapsulated the graphene inside a flexible, elastic silicone membrane — with a hole punched in it to give access to the interior graphene electrode.
They then gently placed gold tape (with a thickness of 10 microns) onto the encapsulating layer to serve as an electrical interconnect between the graphene and the external electronics used to measure and stimulate the heart.
Finally, the researchers placed it onto the heart. The entire thickness of all layers together measures around 100 microns in total.
The resulting device was stable for 60 days on an actively beating heart at body temperature, which is comparable to the duration of temporary pacemakers used as bridges to permanent pacemakers or rhythm management following surgery or other therapies.
Efimov and his team performed optocardiography — using light to track and modulate heart rhythm — in the animal study.
Not only does this present a new way to diagnose and treat heart ailments, the approach also opens new possibilities for optogenetics, a method to control and monitor single cells with light.
While electrical stimulation can correct a heart’s abnormal rhythm, optical stimulation is a more precise method.
Using light, researchers can track specific enzymes as well as interrogate specific heart, muscle or nerve cells.
“We can essentially combine electrical and optical functions into one biointerface.
“Because graphene is optically transparent, we can actually read through it, which gives us a much higher density of readout.”
Image: Ning Liu/University of Texas at Austin