Polymer-based neural ion probe developed by Tohoku University — Simultaneous in vivo measurement of multiple ion concentrations

The accurate regulation of ion concentrations is crucial in many physiological processes, including development, metabolism, immune response, and neurotransmission. Meanwhile, abnormalities in ion concentration balance are associated with various diseases, including hypertension, epilepsy, depression, Parkinson's disease, and Alzheimer's disease. However, methods for measuring ion dynamics in the brain have been limited. A research team led by Associate Professor Yuanyuan Guo of the Frontier Research Institute for Interdisciplinary Sciences and Professor Tatsuo Yoshinobu and Graduate Student Jingxuan Wu of the Graduate School of Biomedical Engineering at Tohoku University has developed a flexible polymer-based neural ion probe and confirmed its high sensitivity, selectivity, and stability in an artificial cerebrospinal fluid (aCSF) environment. The probe can simultaneously monitor sodium, potassium, and chloride ions, solving the problems of miniaturization and multifunctionality of conventional neurological device technology. These findings are expected to contribute to the elucidation of ion dynamics in brain and neurological diseases and were published in Talanta.

Conventional monitoring technologies have faced challenges in monitoring the dynamics of multiple ions in biological tissues and simultaneously achieving device miniaturization and flexibility. To solve these challenges, the research group synthesized a composite carbon material of carbon nanofiber (CNF) and graphene and fabricated a novel multifunctional fiber with four integrated carbon electrodes using a thermal drawing technique, in which multiple fibers are combined and then stretched.

While fabricating the neural ion probe, sensitivity and stability of the carbon electrodes were improved by laser machining for precise structural adjustments of a flexible multifunctional fiber with four micro-scale electrodes. Moreover, an ion-selective membrane was used to impart sodium, potassium, and chloride ion selectivity to the electrodes for achieving the ability to monitor these ions simultaneously with high precision. Furthermore, to implement a multifunctional design, one electrode was reserved for recording electrophysiological signals.

They evaluated the performance of the developed neural ion probe under the aCSF environment and confirmed that the probe had high sensitivity and selectivity for sodium, potassium, and chloride ions and sufficient stability and durability as a sensor. As this probe is flexible and has high biocompatibility, it is expected to serve as a new technological basis for elucidating multi-ion dynamics in research on the brain and neurological diseases and for future medical applications.

The newly developed multifunctional neural ion probe based on thermal drawing and ionophore modification technologies has potential as a new platform in brain and neurological disease research as well as in medical diagnostic technology.

Future research will aim to improve the probe for long-term use and clinical application by further improving biocompatibility and imparting additional functions. The group will also begin developing a design to allow for simultaneous measurement of other physiological signals (temperature, pH and metabolite concentrations) in addition to the ion monitoring function. Furthermore, by taking advantage of this flexible structure, the probe is expected to be useful in personalized medicine and preventive medical care by, for example, incorporating it into clothing or headbands for health monitoring in daily life.

Journal Information
Publication: Talanta
Title: Advancing multiplexed ion monitoring techniques: The development of integrated thermally drawn polymer fiber-based ion probes
DOI: 10.1016/j.talanta.2024.127249