CAREER:Genetic approaches to establish design rules for implantable neurotechnology

脑细胞通过产生和传输电信号进行交流。神经系统疾病，如帕金森氏病和阿尔茨海默氏病，以及脑细胞网络之间的错误或中断信号可能导致损伤。植入式电极是一种能够向大脑“写入”或从大脑“读出”电信号的医疗设备，其发展显著改善了对这些神经疾病和损伤的治疗和理解。 然而，在植入后，身体将植入的器械识别为异物。对植入物的组织反应通常导致疤痕组织的积聚和装置周围的信号产生细胞的损失。这反过来被认为会导致植入物随时间推移而丧失功能。该CAREER项目旨在回答关于植入大脑的电极的组织反应的基本问题：对长期器械性能影响最大的关键生物事件是什么，以及它们如何受到电极设计特征的影响？为了回答这些问题，将应用分子生物学中的新技术来揭示可以预测器械性能的生物标志物;然后将系统地测试器械设计选择，以确定材料和尺寸对这些标志物的影响。 因此，该项目预计将为如何设计具有优化生物相容性和性能的植入电极提供新的理解。 该项目的补充教育目标是，通过对该方案的成功进行新的评估，加强密歇根州立大学生物医学工程的新研究生课程，同时为有兴趣进入生物医学工程领域的女本科生设立一个新的同行指导方案。 研究者的长期研究目标是创建完全集成的神经电极-组织界面。 为了实现这一目标，这个CAREER项目的目标是开发新的方法来理解和控制大脑植入物的生物反应，这被认为是设备功能，稳定性和寿命的关键限制。 研究计划有三个目标。 第一个目标是通过RNA测序识别器械-组织相互作用的生物标志物。 将使用激光捕获显微镜（LCM）切除脑组织的选定部分，以提取RNA并进行后续测序，从而全面了解植入成年大鼠运动皮质的单柄、非功能性硅基器械诱导的基因表达可能发生的变化。 将结果与仅接受插入损伤的对侧组织样本进行比较（以控制“刺伤”效应），这将能够鉴定一组基因，这些基因将被进一步筛选为长期慢性性能的潜在关键生物标志物。 第二个目的是通过敲低三种基因表达来测试生物标志物对信号检测的影响，所述三种基因表达在第一个目的中相对于对照在界面处差异表达最高。 敲除将通过稳定的病毒介导的表达周围的功能，16通道，单柄硅微电极阵列植入大鼠的运动皮层。 与用空向量治疗的对侧对照组织相比，将根据每个设备检测到的“单位”数量、检测到的单位活动的寿命、信噪比（SNR）以及单位和局部场电位的幅度来评估变化。 第三个目标是通过电极材料和特征尺寸的系统测试来定义设计规则。 平面型、单柄阵列将由硅、聚对二甲苯、多晶金刚石和聚二甲基硅氧烷制成。 将测试器械尺寸、杨氏模量、弯曲刚度和特征尺寸对传统组织学测量和前两个目标中识别的生物标志物表达的影响。这些结果将为优化电极与大脑的生物整合提供设计参数的指导。该奖项反映了NSF的法定使命，并通过使用基金会的知识价值和更广泛的影响审查标准进行评估，被认为值得支持。

Brain cells communicate through the generation and transmission of electrical signals. Neurological diseases, such as Parkinson’s disease and Alzheimer’s disease, and injuries can result from faulty or interrupted signaling between networks of brain cells. The development of implanted electrodes, which are medical devices capable of “write-in” or “read-out” of electrical signals to and from the brain, has significantly improved the treatment and understanding of these neurological diseases and injuries. However, following implantation, the body recognizes the implanted device as a foreign object. The tissue response to the implant often results in a build-up of scar tissue and loss of signal-generating cells surrounding the device. This, in turn, is believed to contribute to a loss of function of the implant over time. This CAREER project seeks to answer fundamental questions regarding the tissue response to electrodes implanted in the brain: what are the critical biological events that most strongly impact long-term device performance, and how are they influenced by design features of the electrodes? To answer these questions, new techniques in molecular biology will be applied to reveal biological markers that can predict device performance; then device design choices will be systematically tested to determine the influence of materials and dimensions on these markers. As a result, the project is expected to deliver new understanding of how to design implanted electrodes with optimized biocompatibility and performance. The complementary educational objectives of the project are to strengthen the new graduate curricula in biomedical engineering at Michigan State University through the development of novel assessments of the success of the program, while creating a new peer-mentoring program for undergraduate women interested in entering the field of biomedical engineering. The Investigator’s long-term research goal is to create fully integrated neural electrode-tissue interfaces. Towards this goal, the goal of this CAREER project is to develop new approaches to understand and control biological responses to brain implants, which are believed to be a key limitation to device function, stability, and lifespan. The Research Plan is organized under three objectives. The FIRST Objective is to identify biomarkers of device-tissue interaction through RNA-sequencing. Laser capture microscopy (LCM) will be used to excise selected portions of brain tissue for extraction of RNA and subsequent sequencing to provide a comprehensive view of possible changes in gene expression induced by single shank, non-functional silicon-based devices implanted in the motor cortex of adult rats. Results will be compared to contralateral tissue samples receiving an insertion injury only (to control for “stab” wound effects), which will enable identification of a subset of genes that will be further screened as potentially key biomarkers of long-term chronic performance. The SECOND Objective is to test biomarker effects on signal detection through knockdown of the three gene expressions that were the most highly differentially expressed at the interface relative to control in the first objective. Knockdown will be via stable, viral-mediated expression surrounding functional, 16-channel, single-shank silicon microelectrode arrays implanted in the motor cortex of rats. Changes will be assessed in terms of the number of “units” detected per device, longevity of detected unit activity, signal-to-noise ratio (SNR), and amplitude of units and local field potentials, in comparison to contralateral control tissue treated with an empty vector. The THIRD Objective is to define design rules via systematic tests of electrode materials and feature sizes. Planar style, single shank arrays, will be fabricated from silicon, Parylene, polycrystalline diamond and polydimethylsiloxane. The impact of device dimensions, Young’s modulus, bending stiffness, and feature size on both traditional histological measures and the expression of biomarkers identified in the first two objectives will be tested. These results will provide guidance on design parameters that should be pursued to optimize the biointegration of electrodes with the brain.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.