Long-term changes in the material properties of brain tissue at the implant-tissue interface.
Long-term changes in the material properties of brain tissue at the implant-tissue interface.
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DOI：
10.1088/1741-2560/10/6/066001
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发表时间：
2013-12
影响因子：
4
通讯作者：
Muthuswamy J
中科院分区：
文献类型：
--
作者：
Sridharan A;Rajan SD;Muthuswamy J
大脑组织在植入后几周内，在植入-组织界面经历了戏剧性的分子和细胞重塑。这种重塑对界面的生物力学影响尚不清楚。在这项研究中，我们旨在评估慢性植入微电极后脑-电极界面力学性质的变化。分别于1d(n=4)、10~14d(n=4)、4周(n=4)、6~8周(n=7)将微电极植入鼠脑皮质，深度1 mm。在初始注入时间后，以10μm/s的恒定速度将微电极再向下移动1 mm。在运动过程中和运动终止后测量微电极所感受到的力。使用两个独立的模型--两参数Mooney-Rivlin超弹性模型和具有二阶Prony序列的粘弹性模型--根据测定力-位移曲线来评估界面脑组织的生物力学特性。7只动物中有6只用二阶粘弹性模型估算的剪切模数从植入第1天的0.5~2.6kPa升至植入4周的25.7~59.3kpa，6~8周后降至0.8~7.9kpa。弹性模量值由植入当天的4.1~7.8kpa增加到4周后的24~44.9kpa。7只动物中有6只在植入后6-8周的弹性模量值为6.8-33.3kPa.上述估计表明，微电极周围的脑组织在植入4周后从具有最大剪切和弹性模量的刚性基质演变为具有不同机械性能的两层复合材料-在植入的第一周，坚硬致密的内层被较软的脑组织包围，其生物力学类似于脑组织。微电极上的组织微动应力在植入当天占微电极稳态应力的12%~55%(n=4)，在植入4周后占稳态应力的2%~21%(n=4)，在植入6~8周时占稳态应力的4%~10%(n=7)。了解脑-微电极界面的生物力学行为对于植入式神经假体和微电极阵列的长期成功是必要的。这种对电极-组织界面动态变化的定量物理表征将(A)推动更多机械优化的慢性脑植入物的设计和开发，(B)将导致对关键细胞和分子事件的新见解，例如脑植入物附近的神经元黏附、迁移和功能。
Brain tissue undergoes dramatic molecular and cellular remodeling at the implant-tissue interface that evolves over a period of weeks after implantation. The biomechanical impact of such remodeling on the interface remains unknown. In this study, we aim to assess the changes in mechanical properties of the brain-electrode interface after chronic implantation of a microelectrode. Microelectrodes were implanted in the rodent cortex at a depth of 1 mm for different durations - 1 day (n=4), 10-14 days (n=4), 4 weeks (n=4), 6 - 8 weeks (n=7). After the initial duration of implantation, the microelectrodes were moved an additional 1 mm downward at a constant speed of 10 μm/sec. Forces experienced by the microelectrode were measured during movement and after termination of movement. The biomechanical properties of the interfacial brain tissue were assessed from measured force-displacement curves using two separate models — a 2-parameter Mooney-Rivlin hyperelastic model and a viscoelastic model with a 2nd order prony series. Estimated shear moduli using a 2nd order viscoelastic model increased from 0.5 - 2.6 kPa (day 1 of implantation) to 25.7 - 59.3 kPa (4 weeks of implantation) and subsequently decreased to 0.8 - 7.9 kPa after 6-8 weeks of implantation in 6 of 7 animals. Estimated elastic moduli increased from 4.1-7.8 kPa on the day of implantation to 24 - 44.9 kPa after 4 weeks. The elastic moduli was estimated to be 6.8-33.3 kPa in 6 of 7 animals after 6-8 weeks of implantation. The above estimates suggest that the brain tissue surrounding the microelectrode evolves from a stiff matrix with maximal shear and elastic moduli after 4 weeks of implantation into a composite of two different layers with different mechanical properties – a stiff compact inner layer surrounded by softer brain tissue that is biomechanically similar to brain tissue during the first week of implantation. Tissue micromotion induced stresses on the microelectrode constituted 12-55% of the steady-state stresses on the microelectrode on the day of implantation (n=4), 2-21% of the steady-state stresses after 4 weeks of implantation (n=4), and 4 - 10% of the steady-state stresses after 6-8 weeks of implantation (n=7). Understanding the biomechanical behavior at the brain-microelectrode interface is necessary for long-term success of implantable neuroprosthetics and microelectrode arrays. Such quantitative physical characterization of the dynamic changes in the electrode-tissue interface will (a) drive design and development of more mechanically optimal, chronic brain implants and (b) will lead to new insights into key cellular and molecular events such as neuronal adhesion, migration and function in the immediate vicinity of the brain implant.
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影响因子：
5
作者：
Capadona, Jeffrey R.;Tyler, Dustin J.;Weder, Christoph
通讯作者：
Weder, Christoph
影响因子：
4
作者：
McConnell, G. C.;Butera, R. J.;Bellamkonda, R. V.
通讯作者：
Bellamkonda, R. V.
影响因子：
4.6
作者：
Jensen, W;Yoshida, K;Hofmann, UG
通讯作者：
Hofmann, UG
影响因子：
14
作者：
Karumbaiah, Lohitash;Norman, Sharon E.;Bellamkonda, Ravi V.
通讯作者：
Bellamkonda, Ravi V.
DOI：
10.3389/fneng.2010.00010
发表时间：
2010-01-01
期刊：
Frontiers in neuroengineering
影响因子：
--
作者：
Jackson, Nathan;Sridharan, Arati;Muthuswamy, Jit
通讯作者：
Muthuswamy, Jit