Miniature Implantable Nerve Coolers Allow Targeted Pain Relief


A flexible, implantable cooling device could provide targeted, on-demand pain relief by directly cooling nerves, blocking the transmission of pain signals through peripheral nerves to the brain.

The concepts and design presented in a new studypublished in the July 1 issue of Scienceoffer a promising path towards creating a class of analgesic devices for the long-term management of pain without opioids, especially after surgery or amputation.

Pain management is a pressing health concern for many, affecting approximately one in five adults worldwide. Often, those suffering from acute or short-term pain, such as that felt after surgery or injury, for example, turn to opioid painkillers. Although this class of strong painkillers is very effective, opioids are also highly addictive and misuse can lead to addiction and fatal overdose. According to the US Centers for Disease Control and Prevention, deaths from prescription opioid overdoses outmoded 13,000 in 2021.

This has made the search for effective non-opioid alternatives for pain management an important goal, and several techniques, including the use of non-narcotic drugs, electrical stimulation, acupuncture, and cognitive behavioral therapy, have been explored.

Cool the pain

Another such approach to relieving acute pain is analgesic nerve cooling. Like putting ice on a sore joint or muscle, the targeted application of cold temperature directly to the nerves can block the conduction of pain signals, providing temporary relief on demand.

“Temperature plays a critical role in biological function,” said Jonathan Reeder, assistant professor at the University of Oregon and lead author of the study. “When the temperature of a nerve drops, the rate of the electrochemical processes that allow the conduction of signals through the nerve slows to the point where the transmission of neural signals ceases.”

Cooling a nerve to a moderate temperature of 15 degrees Celsius (59°F) has been shown to block the transmission of acute pain signals through the peripheral nervous system.

However, current cooling devices such as thermoelectric coolers are bulky, rigid, power-hungry, and produce waste heat, and are therefore not well suited for interfacing with delicate soft tissues like nerves. They also lack precise control over where and how much cooling is applied, which opens the door to unintended temperature-induced tissue damage. According to Reeder, these issues preclude the use of local nerve cooling as a practical approach for temporary pain management.

“An implantable cooling device with local analgesia on demand will be a game-changer for long-term pain management,” said Stanford researchers Shan Jiang and Huosong Hong. write in a related field Science Perspective.

A cooling device for precise analgesia

To address this need, Reeder and his colleagues developed a soft, miniaturized, and implantable nerve cooling system based on state-of-the-art microfluidic and flexible electronic technologies.

The thin, elastic device, which borrows its design from electrical nerve cuffs used to stimulate or monitor peripheral nerves, wraps around a nerve fiber, forming a tight interface between the device and tissue to facilitate heat transfer.

Encased in the thin ribbon of water-soluble, biocompatible materials, a system of tiny microfluidic channels directs biocompatible coolant – rapidly cooled by evaporative cooling – throughout the device, delivering targeted cooling directly to the nerve. An adjacent integrated thin-film temperature sensor provides real-time temperature monitoring and precise control of operating temperatures.

“This localizes the cooling effect to the footprint of the microfluidic channel,” down to the millimeter scale, Reeder said.

Additionally, since the device is made from biocompatible and bioabsorbable materials, it dissolves in the body within a month, reducing the risk of unnecessary surgery.

Reeder and researchers tested the device in rat models with neuropathic pain and found it was able to rapidly and precisely cool peripheral sciatic nerves to provide local, on-demand pain relief in animals. freely moving for several weeks after implantation.

“There may be clinical use cases [in humans] for opioid-free management where postoperative pain signals in peripheral nerves are well defined and nerves are already isolated and identified,” said Reeder. “For example, after amputations, nerve grafts or spinal decompression surgeries.

However, nerves cannot be cooled indefinitely without causing tissue damage.

“An important next step is the development of a dosing and titration schedule for nerve cooling that maximizes analgesic effects without damaging the nerve,” Reeder said.


Comments are closed.