In silico assessment of electrophysiological neuronal recordings mediated by magnetoelectric nanoparticles

Abstract

Magnetoelectric materials hold untapped potential to revolutionize biomedical technologies. Sensing of biophysical processes in the brain is a particularly attractive application, with the prospect of using magnetoelectric nanoparticles (MENPs) as injectable agents for rapid brain-wide modulation and recording. Recent studies have demonstrated wireless brain stimulation in vivo using MENPs synthesized from cobalt ferrite (CFO) cores coated with piezoelectric barium titanate (BTO) shells. CFO–BTO core–shell MENPs have a relatively high magnetoelectric coefficient and have been proposed for direct magnetic particle imaging (MPI) of brain electrophysiology. However, the feasibility of acquiring such readouts has not been demonstrated or methodically quantified. Here we present the results of implementing a strain-based finite element magnetoelectric model of CFO–BTO core–shell MENPs and apply the model to quantify magnetization in response to neural electric fields. We use the model to determine optimal MENPs-mediated electrophysiological readouts both at the single neuron level and for MENPs diffusing in bulk neural tissue for in vivo scenarios. Our results lay the groundwork for MENP recording of electrophysiological signals and provide a broad analytical infrastructure to validate MENPs for biomedical applications.

Modeling of core-shell magneto-electric nanoparticles for biomedical applications: Effect of composition, dimension, and magnetic field features on magnetoelectric response

“…The analysis of ME response to weak and near-DC time variant magnetic field (see Fig 5) suggests that the "memory effect" of some materials with hysteresis allows to keep the induced alternating electric fields at levels comparable to the ones induces by strong DC bias magnetic field. These results, not only corroborate experimental results where MENPs stimulated by low amplitude AC frequencies are successfully and safely used [27,[29][30][31][32][33][34], but also provide a basis for understanding the ME effect elicited by low energy external magnetic fields and tuning the corresponding electric output.…”

“…As extensively discussed in literature [18,24,25,27,28,53,57], the structure of the boundary surface, including its extension, indeed strongly affects the ME effect in a way such that higher ME coefficient will require large core-shell ratios. Our analysis on variable MENP core and shell size (Fig 4) further reinforces this concept and reveals that is possible to maximize the ME effect by increasing the magnetostrictive phase content and by reducing the shell thickness.…”

“…In particular this study relies on the following peculiar experimental findings on, even different, ME composites for tuning the ME coupling coefficient: a) the hysteresis loop of ME composites can be leveraged to induce the ME effect even when the DC magnetic field, which is used to magnetize them, is removed ("self-biased" ME composites) [24][25][26]. As a consequence, different core materials, with different hysteretic properties, differently affect the ME coefficient; b) core volume and surface shell thickness, as well as their relative dimensions, [14,18,19,27,28] play a crucial role in all the phases of magnetoelectric process (i.e. core magnetization and magnetostriction, strain mediated coupling at the core-shell interface, piezoelectric response); c) even low amplitude applied AC magnetic fields at frequencies far from the acoustic resonance (> 5 GHz), as in the near-DC frequency where most of biomedical applications operate, yield a strong ME effect.…”

Nanomedicine and nanobiotechnology applications of magnetoelectric nanoparticles

“…A supporting theoretical study was conducted by Bok et al to build a strain-based finite element magnetoelectric model of the above core-shell MENPs and apply the model to quantify the magnetization change in response to an electric field due to neural activity (Bok et al, 2022). They calculated MENPs-medicated electrophysiological readouts at the single neuron level as well as accounted for MENPs' diffusion in bulk neural tissue under different in vivo scenarios.…”

Wireless-Powering Deep Brain Stimulation Platform Based on 1D-Structured Magnetoelectric Nanochains Applied in Antiepilepsy Treatment

“…Magnetoelectric nanomaterials cause strain in the magnetostrictive phase, resulting in applied strain in the piezoelectric phase, thereby inducing a charge separation and thus enabling noninvasive miniature neural stimulators under magnetic stimuli. That is, when exposed to magnetic stimuli, magnetoelectric nanoparticles (NPs) can redistribute surface charges and generate electrical output, causing plasma membrane depolarization and activation of nerve cells in the vicinity, which consequently trigger biophysical and biochemical processes. , In a previous study, magnetoelectric NPs were used for local subthalamic modulation, which can facilitate modulation in other regions comprising the basal ganglia circuitry, leading to behavioral changes in mice . Meanwhile, several magnetoelectric NPs such as Fe 3 O 4 @BaTiO 3 , which possess better biocompatibility, are reported to exhibit promising bioapplications in wireless electrical modulation, indicating the bright prospect of neural modulation by magnetoelectric NPs.…”