An electrode that is injected into a patient as a liquid before curing inside the body could make neuromodulation therapies more reliable, less invasive and more economical.
This is the claim of University of Wisconsin-Madison biomedical engineers and their collaborators whose creation – dubbed the injectrode – is described in a paper published online in Advanced Healthcare Materials.
Neuromodulation therapies involve electrically stimulating nerves to reduce epileptic seizures, soothe chronic pain, and treat depression and a host of other health conditions without the use of conventional drugs like opioids.
According to the team, current neuromodulation treatments rely on surgically implanted devices that can cost up to six figures, require complex procedures to install, and often fail as they are rigid devices attempting to mesh with soft biological tissue.
“Typical implants are really stiff, and so as the body moves, they wear and tear and break down,” said Kip Ludwig, a UW-Madison professor of biomedical engineering and neurological surgery.
According to Ludwig, the liquid can be injected around the nerve, which then cures to create a wired contact.
“The result is much closer to the normal elasticity of tissue,” he said in a statement. “You can actually stretch it and increase its size 150 per cent to 200 per cent without losing its conductivity.”
To create the injectrode, the researchers mixed a silicone base with small metal particles to make the liquid conductive.
They put their device through US Food and Drug Administration preclinical tests and used it to induce heart rate changes in pigs by stimulating their vagus nerve, an approach that’s shown promise for treating heart failure, hypertension and other conditions.
“We essentially went through the standard repertoire of electrochemical tests to show this acts like a standard wire electrode that could be used to stimulate the nerve,” said James Trevathan, a postdoctoral fellow in Ludwig’s lab and first author on the study.
Ludwig co-authored the study and co-founded Neuronoff, a company based on the injectrode, with Case Western Reserve University biomedical engineering professor Andrew Shoffstall and Neuronoff CEO Manfred Franke.
The team recently secured a $2m grant from the US National Institutes of Health to further develop the system to stimulate spinal nerves as a non-opioid alternative to treating chronic back pain.
As part of the NIH grant, the researchers will inject the fluid around the nerve, then extrude a thin insulated string of the material back to just underneath the surface of the skin, where they will inject more of the composite material. Then they can use a basic transcutaneous electrical nerve stimulation (TENS) unit to stimulate the nerve from the surface of the skin, making the whole setup less expensive and more adaptable compared to traditional implanted electrodes.
“We’re making a bypass from the surface of the skin to the location we want to stimulate,” said Ludwig. “As we learn more and more about how to interface with the nervous system, we’re not limited to what we’ve implanted through an invasive surgical procedure. We can actually change how we stimulate, how we talk to the nerve, because we’re essentially just routing our connection to this deep nerve back to the surface of the skin.”