Soft, bioresorbable coolers for reversible conduction block of peripheral nerves

Abstract

Implantable devices capable of targeted and reversible blocking of peripheral nerve activity may provide alternatives to opioids for treating pain. Local cooling represents an attractive means for on-demand elimination of pain signals, but traditional technologies are limited by rigid, bulky form factors; imprecise cooling; and requirements for extraction surgeries. Here, we introduce soft, bioresorbable, microfluidic devices that enable delivery of focused, minimally invasive cooling power at arbitrary depths in living tissues with real-time temperature feedback control. Construction with water-soluble, biocompatible materials leads to dissolution and bioresorption as a mechanism to eliminate unnecessary device load and risk to the patient without additional surgeries. Multiweek in vivo trials demonstrate the ability to rapidly and precisely cool peripheral nerves to provide local, on-demand analgesia in rat models for neuropathic pain.

Cooling away the pain

After injury due to an accident or medical procedure, various forms of pain relief may be required. These can include analgesic medications or local injections to dull the pain receptors, but may also be as simple as applying something cold to the location causing the pain, such as ice packs for sore or bruised joints or muscles. Reeder et al . developed a soft, miniaturized, implantable cooler to temporarily block nerve conduction using a liquid-to-gas phase transition as the cooling mechanism (see the Perspective by Jiang and Hong). They borrowed the design of electrical nerve cuff and substituted electrical wires with a microfluidic channel carrying a microliter volume of bioinert coolant. A thermal thin-film sensor integrated within the cuff enabled monitoring of the temperature in real time, thus enabling closed-loop control. —MSL

Abstract

Implantable nerve coolers with onboard temperature monitoring enable targeted, on-demand pain relief.