Title: Enhanced magnetic transduction of neuronal activity by nanofabricated inductors quantified via finite element analysis
Legend: Model of single-neuron magnetic fields enhanced by nanofabricated coils. (A) A patch clamped primary cortical rat neuron microinjected with fluorescently labeled biocytin, traced digitally for use in the model. Scale bar: 30 μm. (B) Neuron growing on top of a nanofabricated coil (green: calcein AM, grayscale: differential interference contrast). Scale bar: 30 μm. Inset: a neurite interfaced with a mushroom-shaped cell-adhesion protrusion nanofabricated at the interface pad at the center of the coil. (Scale bar: 30 μm). (C), (D) top (XY) views of the model of the naïve (C) and nanocoil-enhanced (D) neuron. Surface color plot, electrical field strength. Slice color plot, magnetic field strength. Inset arrow plot, magnetic flux.
Citation: Phillips, J., Glodowski, M., Gokhale, Y., Dwyer, M., Ashtiani, A., & Hai, A. (2022). Enhanced magnetic transduction of neuronal activity by nanofabricated inductors quantified via finite element analysis. Journal of neural engineering, 19(4), 10.1088/1741-2552/ac7907. https://doi.org/10.1088/1741-2552/ac7907
Abstract: Objective – Methods for the detection of neural signals involve a compromise between invasiveness, spatiotemporal resolution, and the number of neurons or brain regions recorded. Electrode-based probes provide excellent response but usually require transcranial wiring and capture activity from limited neuronal populations. Noninvasive methods such as electroencephalography and magnetoencephalography offer fast readouts of field potentials or biomagnetic signals, respectively, but have spatial constraints that prohibit recording from single neurons. A cell-sized device that enhances neurogenic magnetic fields can be used as anin situsensor for magnetic-based modalities and increase the ability to detect diverse signals across multiple brain regions.Approach.We designed and modeled a device capable of forming a tight electromagnetic junction with single neurons, thereby transducing changes in cellular potential to magnetic field perturbations by driving current through a nanofabricated inductor element. Main results – We present detailed quantification of the device performance using realistic finite element simulations with signals and geometries acquired from patch-clamped neuronsin vitroand demonstrate the capability of the device to produce magnetic signals readable via existing modalities. We compare the magnetic output of the device to intrinsic neuronal magnetic fields (NMFs) and show that the transduced magnetic field intensity from a single neuron is more than three-fold higher at its peak (1.62 nT vs 0.51 nT). Importantly, we report on a large spatial enhancement of the transduced magnetic field output within a typical voxel (40 × 40 × 10µm) over 250 times higher than the intrinsic NMF strength (0.64 nT vs 2.5 pT). We use this framework to perform optimizations of device performance based on nanofabrication constraints and material choices. Significance – Our quantifications institute a foundation for synthesizing and applying electromagnetic sensors for detecting brain activity and can serve as a general method for quantifying recording devices at the single cell level.
Keywords: device; magnetic fields; methods; recording; signals; single neuron; transduction.
About the Lab: The Hai Lab focuses on engineering minimally invasive tools to access the nervous system for neurobiological studies of brain function.
Investigator: Aviad Hai, PhD