Biology subjects

Duret, G.

Publications and source records attributed to Duret, G..

7 recordsLinked to original sources

bioRxiv2025

High-Power Dual-Channel Chamber for High-Frequency Magnetic Neuromodulation

ObjectiveSeveral novel methods, including magnetogenetics and magnetoelectric stimulation, use high frequency alternating magnetic fields to precisely manipulate neural activity. To quantify the behavioral effects of such interventions in a freely moving mouse, we developed a dual-channel magnetic chamber, specifically designed for rate-sensitive magnetothermal-genetic stimulation, and adaptable for other uses of alternating magnetic fields. ApproachThrough an optimized coil design, the system allows independent control of two spatially orthogonal uniform magnetic fields delivered at different frequencies within a 10 x 10 x 6 cm3 chamber suitable for mouse studies. The two channels have nominal frequencies of 50 and 550 kHz with peak magnetic field strengths of 88 and 12.5 mT, achieved with resonant coil drives having peak voltages of 1.6 and 1.8 kV and currents of 1.0 and 0.26 kA, respectively. Additionally, a liquid cooling system enables magnetic field generation for second-level durations, and an observation port and camera allow video capture of the animals behavior within the chamber. Main ResultsThe system generates high-amplitude magnetic fields across two widely separated frequency channels with negligible interference (< 1%). Relatively uniform magnetic field distribution ({+/-}10% across 94% of the chamber volume) is maintained throughout the chamber, and temperature increase of the inner side of the coil enclosure during the operation is limited to < 0.35 {degrees}C/s to ensure in vivo safety. Using cobalt-doped and undoped iron oxide nanoparticles, we demonstrate channel-specific heating rates of 3.5 {degrees}C/s and 1.5 {degrees}C/s, respectively, validating frequency-selectivity. Both channels can run continuously for 4 seconds stably. SignificanceWe present a novel magnetic stimulation platform that combines high-frequency, high-power capability with two independently-controlled channels generating different frequencies, along with a real-time behavioral observation system for freely moving animals. The system supports frequency-multiplexed stimulation strategies for precise modulation of neural activity, making it a versatile tool for advancing magnetogenetics, neural circuit interrogation, and noninvasive stimulation approaches in neuroscience and bioengineering.

bioengineering↗

bioRxiv2025

Magnetic activation of electrically active cells

Magnetic control of cell activity has applications ranging from non-invasive neurostimulation to remote activation of cell-based therapies. Unlike other methods of regulating cell activity like heat and light, which are based on known receptors or proteins, no magnetically gated channel has been identified to date. As a result, effective approaches for magnetic control of cell activity are based on strong alternating magnetic fields able to induce electric fields or materials that convert magnetic energy into electrical, thermal, or mechanical energy to stimulate cells. In our investigations of magnetic cell responses, we found that a spiking HEK cell line with no other co-factors responds to a magnetic field that reaches a maximum of 500 mT within 200 ms using a permanent magnet. The response is rare, approximately 1 in 50 cells, but is fast and reproducible, generating an action potential within 200 ms of magnetic field stimulation. The magnetic field stimulation is over 10,000 times slower than the magnetic fields used in transcranial magnetic stimulation (TMS) and the induced electric field is more than an order of magnitude lower than necessary for neuromodulation, suggesting that induced electric currents do not drive the cell response. Instead, our calculation suggests that this response depends on mechanoreception pathways activated by the magnetic torque of TRP-associated lipid rafts. Despite the relatively rare response to magnetic stimulation, when cells form gap junctions, the magnetic stimulation can propagate to nearby cells, causing tissue-level responses. As an example, we co-cultured spiking HEK cells with beta-pancreatic MIN6 cells and found that this co-culture responds to magnetic fields by increasing insulin production. Together, these results point toward a method for the magnetic control of biological activity without the need for a material co-factor such as synthetic nanoparticles. By better understanding this mechanism and enriching for magneto-sensitivity it may be possible to adapt this approach to the rapidly expanding tool kit for wireless cell activity regulation.

biophysics↗

bioRxiv2023

Relationship between neural activity and neuronal cell fate in regenerating Hydra revealed by cell-type specific imaging

Understanding how neural circuits are regenerated following injury is a fundamental question in neuroscience. Hydra is a powerful model for studying this process because it has significant and reproducible regenerative abilities, a simple and transparent body that allows for whole nervous system imaging, and established methods for creating transgenics with cell-type-specific expression. In addition, cnidarians such as Hydra split from bilaterians (the group that encompasses most model organisms used in neuroscience) over 500 million years ago, so similarities with other models likely indicates deeply conserved biological processes. Hydra is a long-standing regeneration model and is an emerging model for neuroscience; however, relatively little is known regarding the restoration of neural activity and behavior following significant injury. In this study, we ask if regenerating neurons reach a terminal cell fate and then reform functional neural circuits, or if neural circuits regenerate first and then guide the constituent cells toward their terminal fate. To address this question, we developed a dual-expression transgenic Hydra line that expresses a cell-type-specific red fluorescent protein (tdTomato) in ec5 peduncle neurons, and a calcium indicator (GCaMP7s) in all neurons. This transgenic line allowed us to monitor neural activity while we simultaneously track the reappearance of terminally differentiated ec5 neurons as determined by the expression of tdTomato. Using SCAPE (Swept Confocally Aligned Planar Excitation) microscopy, we tracked both calcium activity and expression of tdTomato-positive neurons in 3D with single-cell resolution during regeneration of Hydras aboral end. We observed tdTomato expression in ec5 neurons approximately four hours before the neural activity begins to display synchronized patterns associated with a regenerated neural circuit. These data suggest that regenerating neurons undergo terminal differentiation prior to re-establishing their functional role in the nervous system. The combination of dynamic imaging of neural activity and gene expression during regeneration make Hydra a powerful model system for understanding the key molecular and functional processes involved in neuro-regeneration following injury.

neuroscience↗

bioRxiv2022

Molecular machines stimulate intercellular calcium waves and cause muscle contraction

Intercellular calcium waves (ICW) are complex signaling phenomena that control many essential biological activities, including smooth muscle contraction, vesicle secretion, gene expression, and changes in neuronal excitability. Accordingly, the remote stimulation of ICW may result in versatile new biomodulation and therapeutic strategies. Here, we demonstrate that light-activated molecular machines (MM), molecules that rotate and perform mechanical work on the molecular scale, can remotely stimulate ICW. Live-cell calcium tracking and pharmacological experiments reveal that MM-induced ICW are driven by the activation of inositol triphosphate (IP3) mediated signaling pathways by unidirectional, fast-rotating MM. We then demonstrated that MM-induced ICW can be used to control muscle contraction in vitro in cardiomyocytes and animal behavior in vivo in Hydra vulgaris. Consequentially, this work demonstrates a new strategy for the direct control of cell signaling and downstream biological function using molecular-scale devices.

bioengineering↗

bioRxiv2021

Sub-second multi-channel magnetic control of select neural circuits in behaving flies

Precisely timed activation of genetically targeted cells is a powerful tool for studying neural circuits and controlling cell-based therapies. Magnetic control of cell activity or "magnetogenetics" using magnetic nanoparticle heating of temperature-sensitive ion channels enables remote, non-invasive activation of neurons for deep-tissue applications and studies of freely behaving animals. However, the in vivo response time of thermal magnetogenetics is currently tens of seconds, which prevents the precise temporal modulation of neural activity similar to light-based optogenetics. Moreover, magnetogenetics has not provided a means to selectively activate multiple channels to drive behavior. Here we produce sub-second behavioral responses in Drosophila melanogaster by combining magnetic nanoparticles with a rate-sensitive thermoreceptor (TRPA1-A). Furthermore, by tuning the properties of magnetic nanoparticles to respond to different magnetic field strengths and frequencies, we can achieve sub-second, multichannel stimulation, analogous to multi-color optogenetic stimulation. These results bring magnetogenetics closer to the temporal resolution and multiplexed stimulation possible with optogenetics while maintaining the minimal invasiveness and deep-tissue stimulation only possible by magnetic control.

bioengineering↗

bioRxiv2020

MiniFAST: A sensitive and fast miniaturized microscope for in vivo neural recording

Observing the activity of large populations of neurons in vivo is critical for understanding brain function and dysfunction. The use of fluorescent genetically-encoded calcium indicators (GECIs) in conjunction with miniaturized microscopes is an exciting emerging toolset for recording neural activity in unrestrained animals. Despite their potential, current miniaturized microscope designs are limited by using image sensors with low frame rates, sensitivity, and resolution. Beyond GECIs, there are many neuroscience applications which would benefit from the use of other emerging neural indicators, such as fluorescent genetically-encoded voltage indicators (GEVIs) that have faster temporal resolution to match neuron spiking, yet, require imaging at high speeds to properly sample the activity-dependent signals. We integrated an advanced CMOS image sensor into a popular open-source miniaturized microscope platform. MiniFAST is a fast and sensitive miniaturized microscope capable of 1080p video (1920x1080 pixels), 1.5 {micro}m resolution, frame rates up to 500 Hz (achieved with windowing: 1920 x 55 pixels height) and high gain ability (up to 70 dB) to image in extremely low light conditions. We report results of [~]300 Hz in vivo imaging of freely behaving transgenic Thy1-GCaMP6f mice, high speed 500 Hz in vitro imaging of a GEVI and in vivo GEVI imaging in head-fixed mice. Our results extend miniaturized microscope capabilities in high-speed imaging, high sensitivity and increased resolution, opening the door for the open-source community to use fast and dim neural indicators.

neuroscience↗

bioRxiv2017

Magnetic Entropy as a Gating Mechanism for Magnetogenetic Ion Channels

Magnetically sensitive ion channels would allow researchers to better study how specific brain cells affect behavior in freely moving animals; however, recent reports of \"magnetogenetic\" ion channels have been questioned because known biophysical mechanisms cannot explain experimental observations. Here we show that magnetic fields can produce a change in the magnetic entropy of biogenic nanoparticles, which in turn may generate sufficient heat to gate temperature-sensitive ion channels. This magnetocaloric effect provides a rational approach for developing future magnetogenetic channels.

neuroscience↗