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Wang S, Jiang Q, Liu H, Yu C, Li P, Pan G, Xu K, Xiao R, Hao Y, Wang C, Song J. Mechanically adaptive and deployable intracortical probes enable long-term neural electrophysiological recordings. Proc Natl Acad Sci U S A 2024; 121:e2403380121. [PMID: 39331412 PMCID: PMC11459173 DOI: 10.1073/pnas.2403380121] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/17/2024] [Accepted: 09/03/2024] [Indexed: 09/28/2024] Open
Abstract
Flexible intracortical probes offer important opportunities for stable neural interfaces by reducing chronic immune responses, but their advances usually come with challenges of difficult implantation and limited recording span. Here, we reported a mechanically adaptive and deployable intracortical probe, which features a foldable fishbone-like structural design with branching electrodes on a temperature-responsive shape memory polymer (SMP) substrate. Leveraging the temperature-triggered soft-rigid phase transition and shape memory characteristic of SMP, this probe design enables direct insertion into brain tissue with minimal footprint in a folded configuration while automatically softening to reduce mechanical mismatches with brain tissue and deploying electrodes to a broader recording span under physiological conditions. Experimental and numerical studies on the material softening and structural folding-deploying behaviors provide insights into the design, fabrication, and operation of the intracortical probes. The chronically implanted neural probe in the rat cortex demonstrates that the proposed neural probe can reliably detect and track individual units for months with stable impedance and signal amplitude during long-term implantation. The work provides a tool for stable neural activity recording and creates engineering opportunities in basic neuroscience and clinical applications.
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Affiliation(s)
- Suhao Wang
- Department of Engineering Mechanics, Soft Matter Research Center, and Key Laboratory of Soft Machines and Smart Devices of Zhejiang Province, Zhejiang University, Hangzhou310027, China
- Nanhu Brain-Computer Interface Institute, Hangzhou311100, China
- State Key Laboratory of Brain Machine Intelligence, Zhejiang University, Hangzhou310027, China
| | - Qianqian Jiang
- Department of Engineering Mechanics, Soft Matter Research Center, and Key Laboratory of Soft Machines and Smart Devices of Zhejiang Province, Zhejiang University, Hangzhou310027, China
| | - Hang Liu
- Department of Engineering Mechanics, Soft Matter Research Center, and Key Laboratory of Soft Machines and Smart Devices of Zhejiang Province, Zhejiang University, Hangzhou310027, China
| | - Chaonan Yu
- Nanhu Brain-Computer Interface Institute, Hangzhou311100, China
| | - Pengxian Li
- Department of Engineering Mechanics, Soft Matter Research Center, and Key Laboratory of Soft Machines and Smart Devices of Zhejiang Province, Zhejiang University, Hangzhou310027, China
| | - Gang Pan
- State Key Laboratory of Brain Machine Intelligence, Zhejiang University, Hangzhou310027, China
- College of Computer Science and Technology, Zhejiang University, Hangzhou310027, China
| | - Kedi Xu
- Nanhu Brain-Computer Interface Institute, Hangzhou311100, China
- State Key Laboratory of Brain Machine Intelligence, Zhejiang University, Hangzhou310027, China
- Department of Biomedical Engineering, Qiushi Academy for Advanced Studies, Key Laboratory of Biomedical Engineering of Education Ministry, and Zhejiang Provincial Key Laboratory of Cardio-Cerebral Vascular Detection Technology and Medicinal Effectiveness Appraisal, Zhejiang University, Hangzhou310027, China
| | - Rui Xiao
- Department of Engineering Mechanics, Soft Matter Research Center, and Key Laboratory of Soft Machines and Smart Devices of Zhejiang Province, Zhejiang University, Hangzhou310027, China
| | - Yaoyao Hao
- Nanhu Brain-Computer Interface Institute, Hangzhou311100, China
- State Key Laboratory of Brain Machine Intelligence, Zhejiang University, Hangzhou310027, China
- Department of Biomedical Engineering, Qiushi Academy for Advanced Studies, Key Laboratory of Biomedical Engineering of Education Ministry, and Zhejiang Provincial Key Laboratory of Cardio-Cerebral Vascular Detection Technology and Medicinal Effectiveness Appraisal, Zhejiang University, Hangzhou310027, China
| | | | - Jizhou Song
- Department of Engineering Mechanics, Soft Matter Research Center, and Key Laboratory of Soft Machines and Smart Devices of Zhejiang Province, Zhejiang University, Hangzhou310027, China
- Nanhu Brain-Computer Interface Institute, Hangzhou311100, China
- State Key Laboratory of Brain Machine Intelligence, Zhejiang University, Hangzhou310027, China
- Huanjiang Lab, Zhuji311800, China
- Department of Rehabilitation Medicine, The First Affiliated Hospital, School of Medicine, Zhejiang University, Hangzhou310003, China
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Oh S, Lee S, Kim SW, Kim CY, Jeong EY, Lee J, Kwon DA, Jeong JW. Softening implantable bioelectronics: Material designs, applications, and future directions. Biosens Bioelectron 2024; 258:116328. [PMID: 38692223 DOI: 10.1016/j.bios.2024.116328] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/18/2024] [Revised: 03/30/2024] [Accepted: 04/22/2024] [Indexed: 05/03/2024]
Abstract
Implantable bioelectronics, integrated directly within the body, represent a potent biomedical solution for monitoring and treating a range of medical conditions, including chronic diseases, neural disorders, and cardiac conditions, through personalized medical interventions. Nevertheless, contemporary implantable bioelectronics rely heavily on rigid materials (e.g., inorganic materials and metals), leading to inflammatory responses and tissue damage due to a mechanical mismatch with biological tissues. Recently, soft electronics with mechanical properties comparable to those of biological tissues have been introduced to alleviate fatal immune responses and improve tissue conformity. Despite their myriad advantages, substantial challenges persist in surgical handling and precise positioning due to their high compliance. To surmount these obstacles, softening implantable bioelectronics has garnered significant attention as it embraces the benefits of both rigid and soft bioelectronics. These devices are rigid for easy standalone implantation, transitioning to a soft state in vivo in response to environmental stimuli, which effectively overcomes functional/biological problems inherent in the static mechanical properties of conventional implants. This article reviews recent research and development in softening materials and designs for implantable bioelectronics. Examples featuring tissue-penetrating and conformal softening devices highlight the promising potential of these approaches in biomedical applications. A concluding section delves into current challenges and outlines future directions for softening implantable device technologies, underscoring their pivotal role in propelling the evolution of next-generation bioelectronics.
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Affiliation(s)
- Subin Oh
- School of Electrical Engineering, Korea Advanced Institute of Science and Technology (KAIST), Daejeon, 34141, Republic of Korea
| | - Simok Lee
- School of Electrical Engineering, Korea Advanced Institute of Science and Technology (KAIST), Daejeon, 34141, Republic of Korea
| | - Sung Woo Kim
- School of Electrical Engineering, Korea Advanced Institute of Science and Technology (KAIST), Daejeon, 34141, Republic of Korea
| | - Choong Yeon Kim
- School of Electrical Engineering, Korea Advanced Institute of Science and Technology (KAIST), Daejeon, 34141, Republic of Korea
| | - Eun Young Jeong
- School of Electrical Engineering, Korea Advanced Institute of Science and Technology (KAIST), Daejeon, 34141, Republic of Korea
| | - Juhyun Lee
- School of Electrical Engineering, Korea Advanced Institute of Science and Technology (KAIST), Daejeon, 34141, Republic of Korea
| | - Do A Kwon
- School of Electrical Engineering, Korea Advanced Institute of Science and Technology (KAIST), Daejeon, 34141, Republic of Korea; Department of Materials Science and Engineering, Korea Advanced Institute of Science and Technology (KAIST), Daejeon, 34141, Republic of Korea
| | - Jae-Woong Jeong
- School of Electrical Engineering, Korea Advanced Institute of Science and Technology (KAIST), Daejeon, 34141, Republic of Korea; KAIST Institute for Health Science and Technology, Daejeon, 34141, Republic of Korea.
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Pal A, Park H, Ramamurthy A, Asan AS, Bethea T, Johnkutty M, Carmel JB. Spinal cord associative plasticity improves forelimb sensorimotor function after cervical injury. Brain 2022; 145:4531-4544. [PMID: 36063483 PMCID: PMC10200304 DOI: 10.1093/brain/awac235] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/24/2021] [Revised: 06/10/2022] [Accepted: 06/17/2022] [Indexed: 01/06/2023] Open
Abstract
Associative plasticity occurs when two stimuli converge on a common neural target. Previous efforts to promote associative plasticity have targeted cortex, with variable and moderate effects. In addition, the targeted circuits are inferred, rather than tested directly. In contrast, we sought to target the strong convergence between motor and sensory systems in the spinal cord. We developed spinal cord associative plasticity, precisely timed pairing of motor cortex and dorsal spinal cord stimulations, to target this interaction. We tested the hypothesis that properly timed paired stimulation would strengthen the sensorimotor connections in the spinal cord and improve recovery after spinal cord injury. We tested physiological effects of paired stimulation, the pathways that mediate it, and its function in a preclinical trial. Subthreshold spinal cord stimulation strongly augmented motor cortex evoked muscle potentials at the time they were paired, but only when they arrived synchronously in the spinal cord. This paired stimulation effect depended on both cortical descending motor and spinal cord proprioceptive afferents; selective inactivation of either of these pathways fully abrogated the paired stimulation effect. Spinal cord associative plasticity, repetitive pairing of these pathways for 5 or 30 min in awake rats, increased spinal excitability for hours after pairing ended. To apply spinal cord associative plasticity as therapy, we optimized the parameters to promote strong and long-lasting effects. This effect was just as strong in rats with cervical spinal cord injury as in uninjured rats, demonstrating that spared connections after moderate spinal cord injury were sufficient to support plasticity. In a blinded trial, rats received a moderate C4 contusive spinal cord injury. Ten days after injury, they were randomized to 30 min of spinal cord associative plasticity each day for 10 days or sham stimulation. Rats with spinal cord associative plasticity had significantly improved function on the primary outcome measure, a test of dexterity during manipulation of food, at 50 days after spinal cord injury. In addition, rats with spinal cord associative plasticity had persistently stronger responses to cortical and spinal stimulation than sham stimulation rats, indicating a spinal locus of plasticity. After spinal cord associative plasticity, rats had near normalization of H-reflex modulation. The groups had no difference in the rat grimace scale, a measure of pain. We conclude that spinal cord associative plasticity strengthens sensorimotor connections within the spinal cord, resulting in partial recovery of reflex modulation and forelimb function after moderate spinal cord injury. Since both motor cortex and spinal cord stimulation are performed routinely in humans, this approach can be trialled in people with spinal cord injury or other disorders that damage sensorimotor connections and impair dexterity.
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Affiliation(s)
- Ajay Pal
- Department of Orthopedics, Columbia University, New York, NY 10032, USA
| | - HongGeun Park
- Department of Orthopedics, Columbia University, New York, NY 10032, USA
| | - Aditya Ramamurthy
- Department of Orthopedics, Columbia University, New York, NY 10032, USA
| | - Ahmet S Asan
- Department of Orthopedics, Columbia University, New York, NY 10032, USA
| | - Thelma Bethea
- Department of Orthopedics, Columbia University, New York, NY 10032, USA
| | - Meenu Johnkutty
- Department of Orthopedics, Columbia University, New York, NY 10032, USA
| | - Jason B Carmel
- Department of Orthopedics, Columbia University, New York, NY 10032, USA
- Department of Neurology, Columbia University, New York, NY 10032, USA
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