Image: New device could provide an alternative to opioids and other highly addictive drugs (Photo Courtesy of Northwestern University)
Researchers have developed a small, soft, flexible implant that relieves pain on demand without the use of drugs. The first device of its kind could provide a much-needed alternative to opioids and other highly addictive drugs. The biocompatible, water-soluble device works by gently wrapping itself around nerves to deliver precise, targeted cooling, which numbs nerves and blocks pain signals to the brain. An external pump allows the user to activate the device remotely and then increase or decrease the intensity. After the device is no longer needed, it is naturally absorbed into the body, eliminating the need for surgical extraction. The researchers believe the device will be most valuable for patients undergoing routine surgeries or even amputations that often require postoperative medication. Surgeons may implant the device during the procedure to help manage the patient’s postoperative pain.
The new device, developed by a team of researchers from Northwestern University (Evanston, IL, USA) uses a simple, common concept that everyone knows: evaporation. Similar to how evaporative sweat cools the body, the device contains a liquid coolant that is induced to vaporize at the specific location of a sensory nerve. To create a cooling effect, the device contains tiny microfluidic channels. One channel contains the liquid coolant (perfluoropentane), which is already clinically approved as an ultrasound contrast agent and for pressurized inhalers. A second channel contains dry nitrogen, an inert gas. When the liquid and gas flow into a shared chamber, a reaction occurs that causes the liquid to evaporate instantly. At the same time, a small integrated sensor monitors the nerve’s temperature to make sure it doesn’t get too cold, which can cause tissue damage.
While other cooling therapies and nerve blockers have been tested experimentally, they all have limitations that the new device overcomes. For example, researchers previously investigated cryotherapies, which are injected with a needle. Rather than targeting specific nerves, these imprecise approaches cool large areas of tissue, potentially leading to unwanted effects such as tissue damage and inflammation. At its widest point, Northwestern’s tiny device is just five millimeters wide. One end is curled into a cuff that gently wraps around a single nerve, with no stitches required. By targeting only the affected nerve, the device saves surrounding regions from unnecessary cooling, which could lead to side effects. All components of the device are biocompatible and will naturally absorb into the body’s biofluids over days or weeks without the need for surgical extraction. The bioresorbable device is completely harmless – similar to absorbable sutures.
“The technology reported here uses mechanisms that have some similarities to those that cause your fingers to go numb when they’re cold. With our implant, that effect can be produced in a programmable manner, directly and locally on targeted nerves, even those deep in the surrounding soft tissues,” said John A. Rogers of Northwestern, who led the development of the device. “In addition, you might want the device to just disappear after it’s no longer needed, to avoid delicate and risky surgical removal procedures.”