Impedance optimization by electrophoretic deposition of laser-generated colloidal nanoparticles on the surface of platinum-iridium macroelectrodes for deep brain stimulation and platinum-tungsten microelectrodes for recording of neural activity

在治疗性或诊断性神经外科干预期间，电极通常用于慢性刺激或记录神经元活动。这些电极的质量受到其阻抗的严重影响。在慢性脑深部刺激(DBS)中，为了减少能量消耗，需要低而稳定的阻抗，而为了获得良好的信噪比，记录神经元活动需要高阻抗。在这个项目中，我们的目标是检验由铂和氧化钨纳米颗粒(NP)组成的涂层是否可以用于调节阻抗，并阐明涂层属性(表面覆盖率、颗粒大小、材料)和电极的体外和体内电物理特性之间的系统相关性。在我们联合提案的第一个任期内，我们成功地开发了一种基于电泳沉积(EPD)的涂层工艺，使用激光制造的无配体纳米颗粒，并在体外确定阻抗与纳米颗粒表面覆盖率、表面电荷和新电极的表面氧化呈正相关。长期的大鼠脑深部刺激实验表明，涂有铂纳米颗粒的电极具有显著的阻抗稳定作用。此外，涂层耐机械撕裂，不会对生物相容性产生负面影响。在我们建议的第二阶段，我们打算探索电极在体外的初始阻抗与随后的体内阻抗变化之间的相关性。我们将使用针对低阻抗而优化的涂层参数，在临床上适用于慢性刺激。此外，长期的体外刺激实验将被用来探索所报道的阻抗随时间的变化是仅源于电极还是由于电极-组织的相互作用。除了PTIR电极外，该项目还将进一步专注于PTW记录电极，该电极将涂覆氧化钨和铂NP以实现高阻抗。连续的活体记录实验将验证相应的涂层是否可以改善神经元信号的质量，即信噪比。包衣在体内应用的一个重要问题是包衣的稳定性。因此，将对纳米颗粒在电极上的结合状态进行详细的检查，并对生物相容性进行彻底的评估。该项目将得到基于粒子的EPD过程模拟的补充，以便更精确地将电极特性与涂层参数相关联。

Electrodes are routinely used for chronic stimulation or recording of neuronal activity during therapeutic or diagnostic neurosurgical interventions. The quality of these electrodes is critically affected by their impedance. While low and stable impedance is needed for reduced energy consumption during chronic deep brain stimulation (DBS), high impedance is required for recording of neuronal activity in order to achieve good signal to noise ratios. In this project we aim to examine if coatings composed of platinum and tungsten oxide nanoparticles (NP) can be used to tune the impedance and to elucidate a systematic correlation between coating properties (surface coverage, particle size, material) and electrophysical characteristics of the electrodes in vitro and in vivo. During the first term of our joint proposal we successfully developed a coating process based on electrophoretic deposition (EPD) using laser-fabricated, ligand-free nanoparticles and determined in vitro that impedance positively correlates with nanoparticle surface coverage, surface charge and surface oxidation of the new electrodes. Long term in vivo deep brain stimulation experiments in rats revealed that coating the electrodes with Pt NP significantly stabilizes impedance. Furthermore, the coatings endured mechanical tear and did not negatively affect biocompatibility. During the second phase of our proposal, we intend to explore the correlation between the initial impedance of the electrode in vitro and the subsequent alteration of impedance in vivo. We will use coating parameters optimized for low impedance, clinically relevant for chronic stimulation. Furthermore, long term in vitro stimulation experiments will be used to explore whether reported changes in impedance with time originate from the electrode alone or they are due to electrode-tissue interactions. In addition to PtIr electrodes, the project will further focus on PtW recording electrodes, which will be coated with tungsten oxide and platinum NP for high impedance. Consecutive in vivo recording experiments will verify whether the corresponding coating can improve the quality of the neuronal signal, i.e., the signal to noise ratio. An important issue during in vivo applications of coated is the stability of the coating. Therefore, detailed examinations of the binding state of the nanoparticles on the electrode as well as thorough evaluations of biocompatibility will be conducted. The project will be complemented by particle-based simulations of the EPD process in order to more precisely correlate electrode properties with coating parameters.