The hybrid microfluidic and electronic system for cooling and simultaneously measuring nerve temperature could help reduce pain when implanted, researchers say. Photo courtesy of Northwestern University
June 30 (UPI) -- In a new bid to alleviate opiate misuse, scientists said in a new study they have developed and implanted tiny "nerve coolers" in rats that provide targeted, on-demand pain relief. They anticipate the device could be used in humans within several years.
"All existing pain management strategies rely on drugs," but this offers an "engineering alternative," John A. Rogers, professor of biomedical engineering at Northwestern University/Feinberg School of Medicine and a co-author of the study, told UPI.
The study, published Thursday in the journal Science, found that miniaturized, dissolvable implants -- designed to eliminate pain signals in peripheral nerves without the side effects associated with opioids and other analgesics -- produced highly localized cooling when tested on rats with neuropathic pain.
Separately, a Rice University-led team of researchers in March unveiled their work developing an implantable "bioelectronic" device to stimulate peripheral nerves for disorders resistant to traditional drug therapies.
Such "high-frequency nerve stimulation can also serve as a block and we have some of our own research in that direction," Rogers said of the Rice-led study. "The problem is that the stimulation itself can often cause a pain response."
He said the tiny embedded "nerve cooler" devices developed by his team are seen as most useful in the context of postoperative pain management, "inserted as the final step of a surgery that was already needed to treat a patient condition."
Researchers said the device might be used after amputations, nerve grafts or spinal decompression surgeries, for example.
They explained that targeted application of cold temperature directly to nerves, similar to putting ice on a sore joint or muscle, can rapidly and precisely block conduction of pain signals and give temporary relief.
However, the scientists said, conventional nerve-cooling devices are "bulky and rigid with non-specific cooling and high-power requirements" -- qualities that prevent their practical clinical use.
"We're happy with the engineering aspects of these devices," Rogers said, explaining that the researchers' immediate focus "is in careful, systematic studies of temperature thresholds and durations and recovery periods."
"The timeline would involve transition to larger animal models, then non-human primates then first in man studies," Rogers explained. He noted that any new implantable device must pass through a rigorous regulatory process at the Food and Drug Administration to assess efficacy and safety.
"There are no predicates for a device of this type. As a result, I estimate seven years before use in humans, if things go well," Rogers said.
The device is described as a soft, miniaturized, implantable nerve cooling system that is based on "state-of-the-art microfluidic and flexible electronic technologies."
"Borrowing from electrical nerve cuffs," the researchers "use a liquid-to-gas phase transition within microfluidic channels in an elastic band that wraps around peripheral nerves to provide targeted cooling."
The device contains an integrated thermal thin film sensor that provides real-time temperature monitoring and control. It is made from water-soluble, "biocompatible" materials it can absorb into the body over time, thus reducing surgery risk.
According to Rogers, the devices are "fully bioresorbable, with an operational lifetime of a few weeks and a time to complete dissolution of a few months."
He described the size and the mechanical properties as "roughly those of a wide rubber band."
How are they placed? "The known anatomical distribution of nerve bundles and fibers define the location of the cooling needed to address pain that originates from a particular body region or location," Rogers said.
Rogers explained that the flow rates of the coolant define the cooling power. Flow rates "can be modulated up or down as necessary, and the flow can be turned off when pain relief is no longer necessary," he said.