Flexible Multifunctional Fiber-Based Optoacoustic Emitter for Non-Genetic Bidirectional Neural Communication

Bidirectional communication with neural circuits is essential not only for facilitating a deeper understanding of the nerve system, such as brain, spinal cord and peripheral nerve, but also is a prerequisite of closed-loop stimulation therapies for neurological disorders and neurodegenerative diseases¹. To avoid the interference, integrating multiple modalities of interaction with neurons for recording and stimulating are desired. For example, artifacts induced by electrical stimulus occur in the electrophysiological recording and often corrupt the subsequent analysis of the neural activities². A successful strategy for avoiding interference for bidirectional interfaces is combining electrical recording with optogenetics, which has showed great potentials in achieving sophisticated control over both neural dynamics and animal behaviors. However, the requirement of genetical encoding narrows the application scenarios of those powerful devices and especially obstacles its translation from bench to patients.<br/>Optoacoustic neural modulation is an emerging non-genetic light-mediated technique allows temporally and spatially precise control of neural activity. The optoacoustic process is initiated by delivering a pulsed laser on the absorber, and then broadband acoustic waves will be generated by the transient heating and thermal expansion. In this work, we combined modalities of optoacoustic neural stimulation and electrical recording to avoid opsins transfection required by current optrode devices. An optoacoustic coating was precisely deposited on the center core of a multifunctional fiber using a 3D micromanipulator and nano-injector. We demonstrated the multifunctional fiber-based optoacoustic emitter (mFOE) for simultaneous optoacoustic stimulation and neural recording in vivo. Specifically, after one month, chronic implanted mFOE still showed a comparable performance as day 3, validating its ability in long-term stimulation and recording as a stable interface with brain. Repeatable neural responses (&gt; 0.5 mV in local field potential recording) were induced by optoacoustic stimulation and simultaneously recorded. Moreover, as a flexible and biocompatible device, the histological assessment of tissue response to the mFOE confirmed its biocompatibility. By utilizing optoacoustic neural stimulation, mFOE reduces the difficulties of opsins transfection associated with conventional optrodes and paves the foundations of future closed-loop brain stimulation for both neuroscience research and neurological disease treatment.<br/>Reference<br/>1 Frank, J. A., Antonini, M. J. & Anikeeva, P. Next-generation interfaces for studying neural function. Nat Biotechnol 37, 1013-1023, doi:10.1038/s41587-019-0198-8 (2019).<br/>2 Heffer, L. F. & Fallon, J. B. A novel stimulus artifact removal technique for high-rate electrical stimulation. J Neurosci Methods 170, 277-284, doi:10.1016/j.jneumeth.2008.01.023 (2008).