Magnetic Stimulation of Neuronal Fibers: From Macroscopic Dorsal Column Neuromodulation for Sciatica to Microscopic L1 Circuit Activation for Connectome Studies

Abstract

Magnetic neuromodulation offers a compelling alternative to pharmacologic therapy and conventional electrode-based stimulation by enabling contactless activation of neural tissue across multiple spatial scales. In this talk, I will present a multiscale engineering framework for magnetic stimulation spanning macroscopic activation of spinal pathways to microscopic manipulation of local neural circuits in the rat.

At the systems level, we developed a high-frequency trans-spinal magnetic stimulation (HF-TSMS) platform designed for noninvasive treatment of chronic neuropathic back pain. The stimulator operates in quasi-resonant mode to generate multi-kA current pulse trains at 10 kHz, driving a custom ribbon-based figure-of-eight coil to induce spatially confined electric fields within the spinal cord. Electromagnetic simulations were used to optimize coil geometry and field distribution for rodent anatomy. In spared nerve injury models, HF-TSMS produced behavioral improvements and modulation of BOLD fMRI responses compared with sham controls, providing preliminary evidence for therapeutic efficacy and supporting future translational development.

At the microscopic scale, we engineered a silicon-based micro-magnetic stimulation (µMS) device (200 × 400 × 7 µm³) fabricated using advanced microfabrication techniques. The µMS coil was deployed in rat cortex and driven with high-current, short-duration pulses to generate highly localized magnetic fields. Neuronal activation was quantified using optical glutamate sensing via fiber photometry in combination with local field potential recordings. µMS elicited stimulus-locked increases in glutamate release in vivo that were absent post-euthanasia, confirming biological specificity. Quantitative analyses demonstrated significant increases in peak amplitude and integrated glutamate response during stimulation epochs.

Together, these results demonstrate that magnetic stimulation can be engineered to operate across anatomical scales—from dorsal column modulation to focal microcircuit activation—using physics-based design, microfabrication, and multimodal validation. This multiscale approach establishes a foundation for next-generation magnetic neuromodulation technologies that are noninvasive at the systems level yet capable of highly localized circuit control.

Bio

Dr. Giorgio Bonmassar is an Associate Professor of Radiology at Harvard Medical School and Director of the Analog Brain Imaging (ABI) Laboratory at the Athinoula A. Martinos Center for Biomedical Imaging at Massachusetts General Hospital. For more than two decades, his research has focused on bioelectromagnetic modeling and the design of MRI-compatible electrophysiology and neuromodulation technologies. His work integrates engineering, physics, and neuroscience to develop safe, high-performance systems that operate seamlessly within the MRI environment, advancing both fundamental brain research and clinical translation. Dr. Bonmassar is internationally recognized for pioneering multimodal neurostimulation platforms, including the first low-frequency focused ultrasound (LiFU) system for spinal cord neuromodulation and a novel high-frequency trans-spinal magnetic stimulation (HF-TSMS) system funded by the NIH. His laboratory develops non-invasive magnetic and ultrasound approaches aimed at transforming the treatment of chronic pain and neurological disorders. In parallel, he has led the design of MRI-conditional deep brain stimulation (DBS) and electrocorticography (ECoG) systems based on metamaterial and resistively tapered technologies, substantially reducing RF-induced heating and imaging artifacts. Earlier contributions include the first demonstration of simultaneous visual evoked potentials and fMRI, MRI-invisible microelectrodes, and polymer-based high-density EEG systems (InkCap and InkNet) that enable safe EEG-fMRI at high field strengths. As Principal Investigator on multiple NIH awards (including U01, R01, SBIR, and BRAIN Initiative mechanisms), Dr. Bonmassar leads interdisciplinary efforts spanning computational modeling, device fabrication, safety validation, and preclinical translation. His work is unified by a central mission: to engineer next-generation neurotechnology platforms that are safe, imaging-compatible, and capable of precise, multimodal control of neural circuits.

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Bioengineered Hydrogels for Regenerative Medicine

Abstract

Hydrogels, highly hydrated cross-linked polymer networks, have emerged as powerful synthetic analogs of extracellular matrices for basic cell studies as well as promising biomaterials for regenerative medicine applications. A critical advantage of these synthetic matrices over natural networks is that bioactive functionalities, such as cell adhesive sequences and growth factors, can be incorporated in precise densities while the substrate mechanical properties are independently controlled. We have engineered poly(ethylene glycol) [PEG]-maleimide hydrogels for local delivery of therapeutic proteins and cells in several regenerative medicine applications. For example, synthetic hydrogels with optimal biochemical and biophysical properties have been engineered to direct human stem cell-derived intestinal organoid growth and differentiation, and these biomaterials serve as injectable delivery vehicles that promote organoid engraftment and repair of intestinal wounds. In another application, hydrogels presenting immunomodulatory proteins induce immune acceptance of allogeneic pancreatic islets and reverse hyperglycemia in models of type 1 diabetes. Finally, photopatterned hydrogel-based microfluidic platforms have been developed using human organoids to model lymphoid-gut interactions. These studies establish these biofunctional hydrogels as promising platforms for basic science studies and biomaterial carriers for cell delivery, engraftment and enhanced tissue repair.

Bio

Andrés J. García is the Executive Director of the Petit Institute for Bioengineering and Bioscience and Regents’ Professor at the Georgia Institute of Technology. Dr. García’s research program integrates innovative engineering, materials science, and cell biology concepts and technologies to create cell-instructive biomaterials for regenerative medicine and generate new knowledge in mechanobiology. This cross-disciplinary effort has resulted in innovative biomaterial platforms that elicit targeted cellular responses and tissue repair, human stem cell technologies, and mechanistic insights into the interplay of mechanics and cell biology. In addition, his research has generated intellectual property and licensing agreements with start-up and multi-national companies. He is a co-founder of 5 start-up companies. He has received several distinctions, including the Young Investigator Award, the Clemson Award for Basic Science, and the Founders Award from the Society for Biomaterials; the International Award from the European Society for Biomaterials; the Biomaterials Global Impact Award; and Georgia Tech’s Outstanding Interdisciplinary Activities Award and the Class of 1934 Distinguished Professor Award. He is an elected Fellow of Biomaterials Science and Engineering, Fellow of the American Association for the Advancement of Science, Fellow of the American Society of Mechanical Engineers, and Fellow of the American Institute for Medical and Biological Engineering. He served as President for the Society for Biomaterials in 2018-2019. He is an elected member of the National Academy of Engineering, the National Academy of Medicine, and the National Academy of Inventors.

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Please join us for the annual BME Jaharis Lecture.

Dr. Omid Veiseh from Rice University presents "Bioengineering Cell-based Therapeutics"

Abstract: Cell-based therapeutics are an emerging modality that can potentially treat many currently intractable diseases through uniquely powerful modes of action. Our group is innovating new biomaterials and cellular constructs for medicine and biology by combining chemical biology, cellular engineering, and multi-scale fabrication. We have pioneered innovative approaches to synthesizing and in vivo screening of large libraries of biomaterial formulations for tailored applications in immunology and medicine. In my talk, I will describe our advances in discovering immunomodulatory biomaterials that can interact appropriately with the host immune system for localized immunomodulation. I will highlight our efforts to develop “cytokine factories” locally activating the innate and adaptive immune response to generate systemic immunotherapy and eradicate metastatic cancer. This approach has advanced to phase I/II human clinical trials for treating recurrent, refractory ovarian cancer.

Bio: Dr. Omid Veiseh, Ph.D., is a Professor and CPRIT Scholar in Cancer Research in the Departments of Bioengineering and Chemical and Biomolecular Engineering at Rice University. He is also the Director of Rice University's Biotech Launch Pad, a new initiative with a mission to accelerate the translation of Rice University discoveries and technologies into clinical practice to provide rapid patient access to leading-edge therapeutic products. He leads an interdisciplinary translational research program to engineer and commercialize next-generation cell-based therapeutics for various human diseases. His team leverages the latest techniques in synthetic biology, immunoengineering, and materials science to develop innovative cell-based platforms for real-time and feedback-regulated production of biologics. Throughout his career, he has authored or co-authored more than 80 peer-reviewed publications, including those in Nature, Nature Biotechnology, Nature Materials, Nature Medicine, and Nature Biomedical Engineering. He is an inventor on more than 50 pending or awarded patents. He is also a serial entrepreneur who has co-founded multiple biotechnology companies, collectively attracting ~ $500M in private and public investment capital. Dr. Veiseh has been elected as a fellow of the Controlled Release Society and a member of the National Academy of Inventors.

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