Evaluation of Carbon Nanotube Electrodes for Neural Stimulation

描述（由申请人提供）：该项目的目标是评估碳纳米管（CNTs）作为低阻抗、更小的神经刺激电极，使用深部脑刺激（DBS）作为测试案例。电极-组织界面的低阻抗导致更低的功耗，因为需要更小的电压来实现相同的电荷注入。低功耗延长了电池寿命，减小了电池的尺寸，从而减小了植入装置的尺寸。刺激电极的大小受到有效刺激所需的最小电荷注入和电极-组织界面阻抗的限制。此外，电极的尺寸是电极产生的插入损伤和可刺激体积的特异性的重要因素。更低的阻抗和更小的电极将导致更少的破坏性电极和更小、更持久的电池组合。我们将使用体外定量测量来比较碳纳米管电极与AIROF和传统铂电极的性能。我们期望在水电解窗口内将可逆电荷注入容量Qinj（以C/cm2计）比相同尺寸的Pt电极增加230%，并将AIROF电极的可逆电荷注入容量增加200%，或者在保持相同电荷注入容量的同时将电极的尺寸从标准的0.06 cm2减小到0.026 cm2，或两者的组合。我们期望与相同尺寸的铂电极相比将阻抗Z降低65%，与AIROF电极相比降低40%。本项目的具体目标是：(1)量化碳纳米管形态（长度、密度、取向）对电荷注入和界面阻抗的影响，并确定那些增加电荷注入和降低界面阻抗的组合。电荷注入能力将通过测量体外电流脉冲刺激时的电压瞬变来确定，电荷注入机制将通过循环伏安法来确定。用电化学阻抗谱法在体外测量界面阻抗。(2)使用Aim #1中的最佳电极配置，评估碳纳米管表面的化学修饰，例如氧官能团，例如=O和-COOH，以进一步增加电荷注入能力并降低阻抗。(3)在体外用大鼠神经组织测试Aim #2中前5种电极配置的神经胶质反应，评估CNT电极在神经组织存在下的性能（Qinj， Z，功耗），并将其性能与铂电极和AIROF电极进行比较。此外，电极将在溶液中进行慢性脉冲测试，以评估电荷注入能力和界面阻抗的稳定性。这个项目的结果将是对碳纳米管进行全面的体外评估，用铂催化剂生长，作为高效的神经刺激电极。如果实现，它将导致更小的神经刺激电极，限制插入损伤，并消耗更少的功率，从而减小电池的尺寸并延长电池的使用寿命。

DESCRIPTION (provided by applicant): The goal of this project is to evaluate carbon nanotubes (CNTs) as lower impedance, smaller electrodes for neurostimulation, using deep brain stimulation (DBS) as a test case. Lower impedance of the electrode-tissue interface results in lower power consumption, as a smaller voltage is required to achieve the same charge injection. Low power consumption extends battery life and decreases the size of the batteries and thus of the implanted device. The size of stimulating electrodes is limited by the minimum charge injection required for effective stimulation and the impedance of the electrode-tissue interface. As well, the size of the electrode is an important factor in the insertion damage created by the electrode and the specificity of the volume that can be stimulated. Lower impendence and smaller electrodes will lead to less damaging electrodes and a combination of smaller and longer lasting batteries. We will compare the performance of CNT electrodes to AIROF and traditional platinum electrodes using quantitative in vitro measurements. We expect to increase the reversible charge injection capacity, Qinj, (in ¿C/cm2) by 230% over the same-sized Pt electrode and exceed AIROF electrodes by 200% in the water electrolysis window, or to reduce the size of the electrode from a standard 0.06 cm2 to 0.026 cm2 while maintaining the same charge injection capacity, or a combination thereof. We expect to reduce the impedance, Z, by 65% vs a platinum electrode and 40% vs an AIROF electrode of the same size. The specific aims of this project are: (1) Quantify the effect of CNT morphology (length, density, orientation) on charge injection and interfacial impedance, and identify those combinations that increase charge injection and reduce interfacial impedance. The charge injection capacity will be determined by measuring voltage transients during in vitro current pulse stimulation, and the charge injection mechanisms will be determined by cyclic voltammetry. The interfacial impedance will be measured in vitro by electrochemical impedance spectroscopy. (2) Using the best electrode configuration from Aim #1, evaluate chemical modification of the CNT surface, such as oxygen functional groups, e.g., =O and -COOH, to further increase the charge injection capacity and decrease the impedance. (3) Test the top 5 electrode configurations from Aim #2 in vitro with rat neural tissue for a glial response and assess the CNT electrode performance (Qinj, Z, power consumption) in the presence of neural tissue and compare the performance to platinum and AIROF electrodes. Further, the electrodes will undergo chronic pulse testing in solution to evaluate the stability of charge injection capacity and interfacial impedance. The outcome of this project will be a comprehensive in vitro assessment of carbon nanotubes, grown with a platinum catalyst, as highly efficient neural stimulation electrodes. If realized, it will lead to neural stimulation electrodes that are smaller, limiting insertion damage, and consume less power, thereby reducing the size and increasing the lifetime of batteries. PUBLIC HEALTH RELEVANCE: Carbon nanotube-based electrodes for neural stimulation will allow the creation of neural electrodes to alleviate symptoms of Parkinson's disease, Essential tremor, and potentially other neural stimulation applications. These electrodes will be smaller, causing less damage to the brain, and have lower power consumption, so batteries will last longer and need to be replaced less frequently.