World-first implant relieves pain without drugs, absorbed into body

A study on the implant titled "Soft, bioresorbable coolers for reversible conduction block of peripheral nerves" has been published in the journal Science.

Researchers from Northwestern University have created a small, flexible, biocompatible device that can be implanted into a patient to provide pain relief as an alternative to painkilling medications like opioids, circumventing any problems arising from the highly addictive properties of such drugs. The device softly wraps around nerves and cools them, numbing them and preventing pain signals from being sent to the brain, and the patient can adjust it to provide more or less relief with an external pump.

The implant is water-soluble and bioresorbable, meaning when it is no longer needed, the body can absorb it, bypassing the need for it to be extracted with surgery. It contains perfluoropentane, a liquid coolant it releases from one small channel to mix in a shared chamber with nitrogen gas from a second channel. The mixing causes the perfluoropentane to evaporate, cooling the nearby nerve, while an integrated temperature sensor protects against tissue damage by ensuring the nerve doesn't get too cold.

"As you cool down a nerve, the signals that travel through the nerve become slower and slower-eventually stopping completely. We are specifically targeting peripheral nerves, which connect your brain and your spinal cord to the rest of your body. These are the nerves that communicate sensory stimuli, including pain. By delivering a cooling effect to just one or two targeted nerves, we can effectively modulate pain signals in one specific region of the body," said study coauthor Dr. Matthew MacEwan of Washington University School of Medicine in St. Louis.

"Although opioids are extremely effective, they also are extremely addictive. As engineers, we are motivated by the idea of treating pain without drugs-in ways that can be turned on and off instantly, with user control over the intensity of relief. The technology reported here exploits mechanisms that have some similarities to those that cause your fingers to feel numb when cold. Our implant allows that effect to be produced in a programmable way, directly and locally to targeted nerves, even those deep within surrounding soft tissues," said Northwestern's John A. Rogers, who led the device's development.

You can read more from the study here.