A liquid crystal polymer-based neuromodulation system: an application on animal model of neuropathic pain

Abstract

OBJECTIVE: We developed a custom-made miniaturized neural stimulation system with a liquid crystal polymer (LCP)-based electrode array for animal experiments. In order to verify the feasibility of the system, motor cortex stimulation (MCS) was applied on the rat pain model induced by sciatic nerve injury. MATERIALS AND METHODS: LCP is mechanically stable and chemically inert and has a much lower water absorption rate than other biocompatible polymers such as polyimide or parylene. In the present study, a film-type LCP substrate is used to microfabricate the cortical stimulation electrode array. A miniaturized electrical neuromodulation system is implemented using an application-specific integrated chip for generation of electrical stimulation current. In vivo experiment was performed using a rat neuropathic pain model induced by sciatic nerve injury. The electrodes were attached to the contralateral primary motor cortex, which processes the hind limb movement. Mechanical allodynia was measured before, during, and after electrical stimulation to determine the effects on pain threshold. RESULTS: Electrical stimulation into the brain structure processing pain perception was effective in alleviating neuropathic pain. The pain threshold of the rats increased more than fivefold during the electrical stimulation. CONCLUSION: We developed a miniaturized electrical stimulation system with a novel flexible LCP electrode array for MCS in rats. This system is expected to be used in studying various neurological diseases and examining in vivo brain function.