Evidence that physiologically relevant forces orchestrate cortical neuron function

Abstract

Growing evidence indicates that neurons within the brain are mechanosensitive. The relationship between mechanical forces and neuronal function remains largely unknown, and what potential these mechanical interactions provide for modulating brain function remains undiscovered. These unknowns result from insufficient tools to mechanically probe neuronal function at the circuit scale. To address these challenges, we delivered magnetic nanoparticle-mediated mechanical forces through large-scale magnetic gradient manipulation from permanent magnetic fields to cultured neurons. We show that pN mechanical forces delivered by neuron- internalized magnetic nanoparticles manipulate the structural alignment of neuronal growth cones in the direction of the magnetic field while specifying the neurons as axonal through cytoskeletal regulation. Using microelectrode arrays, we show that these nanomagnetic-guided networks present with increased functional connectivity in the direction of forces and that neuronal activity is enhanced in the direction of forces. We then exposed a nanomagnetic force- driven calcium influx in formed cortical networks with internalized magnetic nanoparticles. This modulation was dependent on the internalization of the nanoparticles and dependent on the magnetic nanoparticle interaction and exposure time with the neurons. Employing these forces across dense cortical networks highlighted a lasting and irreversible suppression in network-wide synchrony while not impacting cell health. Finally, to investigate this interaction further, we employed multi-modal recordings through both calcium and microelectrode array recordings to map the functional responses to forces. With the multi-modal recording, we uncover a time, force, and nanoparticle-dependent calcium and electrophysiological excitation to pN nanomagnetic forces, highlighting that modulated neurons can present with high electrophysiological activity without the cytosolic calcium influx. Altogether, these results indicate that the pN nanomagnetic forces provoked by the magnetic nanoparticle assay reshaped neuronal circuit function by guiding structural networks or shifting the activity profiles of formed networks.