An implantable device that blocks pain by cooling the nerves has been (successfully) tested


An implantable device that blocks pain by cooling the nerves has been (successfully) tested
Written by aquitodovale

from Cristina Marrone

The device, made of biodegradable materials, cools the nerves up to 10 °. Tested so far on mice with success with the aim of not abusing drugs. Research published in Science

A team of researchers led by Northwestern University has developed a small, soft and flexible implant that relieves pain (on request) without the need to use drugs. The first device of its kind, created with biodegradable materials which over time are absorbed by the body, could provide ato

Limportant alternative to opioids
and other drugs that can be addictive. The prototype has so far been successfully tested in mice and the study was published in the July 1 issue of the journal Science.

Remote and drug-free activation

The device works by gently wrapping the nerves: it causes a precise and targeted cooling
up to 10 °that numbs the nerves and blocks pain signals to the brain. An external pump allows the patient to remotely activate the device, increasing or decreasing the intensity according to the need of the moment. When the device is no longer needed, it is absorbed by the body without having to resort to surgery for extraction. The researchers point out that the device can prove very useful for patients undergoing routine surgery or even amputations that require massive doses of post-operative medications to manage pain. “While opioids are extremely effective, they are also highly addictive,” says John A. Rogers of Northwestern, who led the development of the device. “As engineers, we are motivated by the idea of ​​treating pain without drugs, with devices that can be turned on and off instantly, with direct user control over the intensity of relief. Our implant reproduces the effect that is felt when the hands, due to being too cold, become numb but it is applied in a targeted way to the nerves, even those deep inside the soft tissues ».

Tests on mice

To test its functionality, the device was iimplanted around the sciatic nerve of the legs of three mice. Then injuries were caused to the legs, so that they became more sensitive. Three weeks later, each time the mouse’s sore paw was pressed using a particular device, seven times the force was required for the animals to retract the paw when the device was on, a sign that thelimb was numb. Six months later the device was reabsorbed by the body and no nerve damage was observed. “We will now have to test the implant in animals to figure out how many nerves can be cooled and for how long, without causing damage,” says Rogers, pioneer of bioelectronics Professor of Materials Science and Engineering, Biomedical Engineering and Neurological Surgery at McCormick School of Engineering. and Northwestern University Feinberg School of Medicine.

How does it work

While the new device may sound like science fiction, it takes advantage of a simple and common concept everyone is familiar with: theevaporation
. Just as the evaporation of sweat cools the body, the device contains a coolant which is induced to evaporate when placed on a nerve. To induce the cooling effect, the device contains tiny microfluidic channels. One channel contains the coolant (perfluoropentane), already clinically approved as a contrast agent for ultrasound and pressurized inhalers. A second channel contains dry nitrogen, an inert gas. When liquid and gas flow into a shared chamber, one occurs reaction that causes the liquid to evaporate quickly. At the same time, a tiny built-in sensor monitors the nerve’s temperature to make sure it doesn’t get too cold, which could lead to tissue damage. “Excessive cooling can damage the nerve and the fragile tissues surrounding it,” Rogers explains. «The duration and temperature of the cooling must therefore be precisely controlled. The work in progress tries to define the complete set of time and temperature thresholds below which the process remains completely reversible ».

The other attempts

Many previous pain-relieving approaches that have worked in rats have not been successful in people, and cooling of the nerves is well known to block their function. Previously, researchers have also explored injection cryotherapy. But instead of targeting specific nerves, these imprecise approaches cool large areas of tissue, potentially leading to unwanted effects such as tissue damage and inflammation. Even the electrical stimulation to silence painful stimuli has limitations because the activation of the device creates pain and muscle contractions, not ideal from the patient’s point of view.

The advantages

The new device instead has the advantage of being really tiny, only 5 millimeters wide at its widest point. By precisely targeting only the affected nerve, the device does not involve surrounding regions from unnecessary cooling, which could cause side effects. “We do not want to inadvertently cool nerves or tissues unrelated to the nerve that transmits painful stimuli to the brain – underlines Matthew McEwan, of the Washington University School of Medicine in St. Louis and co-author of the study. “We want to block the pain signals, not the nerves that control motor function and allow, for example, to use the hand.”

July 1, 2022 (change July 1, 2022 | 16:37)

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