Optically-Controlled 'Living Electrodes' with Long-Projecting Axon Tracts for a Synaptic Brain-Machine Interface

Abstract

Achievements in intracortical brain-machine interfaces are compromised by limitations in long-term performance and information transfer rate. A biological intermediary between devices and the brain based on synaptic integration may offer a specificity and permanence that has eluded neural interfaces to date. Accordingly, we have developed the first living electrodes comprised of implantable axonal tracts protected within soft hydrogel cylinders to enable biologically-mediated monitoring and modulation of brain activity. Here we demonstrate the controlled fabrication, rapid axonal outgrowth, reproducible cytoarchitecture, and axonal conduction of these engineered constructs in vitro. We also present simultaneous optical stimulation and recording of neuronal activity in vitro, transplantation in rat cortex, and their survival, integration, and activity over time in vivo as a proof-of-concept for this neural interface paradigm. The creation and functional validation of living electrodes is a critical step towards developing a new class of neural interfaces using targeted, synaptic-based integration with native circuitry.