Soft Bioresorbable Implant Controls Pain by Cooling Nerves

A team of engineers at Northwestern University led by John Rogers, the person responsible for many advances in flexible electronics, created a drug-free implant that can control pain by cooling nerves. The soft implant is intended to be wrapped around a nerve during surgical procedures that would typically involve opioid-based analgesia afterwards. As a drug-free technology, the implant could help to avoid the addiction and side-effects that opioids frequently cause. The implant contains a liquid coolant that undergoes controlled evaporation at the target site, resulting in a cooling effect that slows down neurotransmission and reduces pain. In a final flourish, the researchers designed the implant to be completely bioresorbable, meaning that it dissolves away over time, avoiding the need for a follow-up procedure to remove it.

Pain relief is a thorny issue, with some of the most effective drugs, opioids, coming with significant drawbacks in terms of their addictive potential. Consequently, researchers are developing new strategies that take addiction out of the equation. This latest drug-free approach relies on cooling peripheral nerves so that they cannot transmit pain signals to the brain.

“Although opioids are extremely effective, they also are extremely addictive,” said John Rogers in a press release. “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.”

The device contains a perfluoropentane coolant and nitrogen gas that are contained within separate microfluidic channels. When a user wishes to receive pain relief they can control an external pump that causes the coolant and gas to mix together in a chamber within the implant, making the coolant rapidly evaporate, and resulting in a cooling effect on the wrapped nerve.

“As you cool down a nerve, the signals that travel through the nerve become slower and slower — eventually stopping completely,” said Matthew MacEwan another of the developers of the new implant. “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.”

See a video of the device dissolving below.