Chronically Implanted, Nafion-Coated Ag/AgCl Reference Electrodes for Neurochemical Applications
Chronically Implanted, Nafion-Coated Ag/AgCl Reference Electrodes for Neurochemical Applications
复制标题
DOI：
10.1021/cn2000684
复制
发表时间：
2011-11-01
影响因子：
5
通讯作者：
Wightman, R. Mark
中科院分区：
文献类型：
--
作者：
Hashemi, Parastoo;Walsh, Paul L.;Wightman, R. Mark
碳纤维微电极上的快速扫描循环伏安法可用于测量自由活动大鼠脑细胞外液中与行为相关的多巴胺变化。这些实验采用长期注入的Ag/AgCl参比电极。当在植入后4天进行多巴胺测量时，在多巴胺的循环伏安图中的阳极和阴极峰中通常存在电位偏移，通常大于+0.2V。在这项工作中，我们优化了一种方法，用全氟聚合物Nafion涂覆烧结Ag/AgCl参比电极，以防止这种偏移。我们发现，我们可以稳定参比电极长达28天。植入部位周围组织的免疫组织化学显示裸器械和Nafion涂层器械周围均存在广泛的神经胶质包囊。然而，裸电极周围的损伤具有粗糙的纹理，这意味着这些细胞被强烈地吸附到裸参比电极上，而Nafion涂覆的电极周围的损伤显示细胞更完整，这意味着它们吸附不那么强烈。电极表面的能量色散X射线光谱和扫描电子显微镜分析通过仅在裸电极上观察到有机性质的斑块的大量积聚来证实这一点。阻抗谱表明裸露和Nafion涂层的Ag/AgCl电极的阻抗之间没有差异，表明胶质封装不会导致工作电极和参比电极之间的未补偿电阻增加。因此，电化学位移一定是由于参比电极周围独特的化学微环境改变了氯化物平衡，而Nafion涂层阻止了这一过程。
Fast-scan cyclic voltammetry at carbon-fiber microelectrodes can be used to measure behaviorally correlated dopamine changes in the extracellular fluid of the brain of freely moving rats. These experiments employ a chronically implanted Ag/AgCl reference electrode. When dopamine measurements are taken 4 days after implantation, there is often a potential shift, typically greater than +0.2 V, in the anodic and cathodic peaks in the cyclic voltammogram for dopamine. In this work, we optimized a method to coat sintered Ag/AgCl reference electrodes with the perfluorinated polymer, Nafion, to prevent this shift. We find that we can stabilize reference electrodes for up to 28 days. Immunohistochemistry of the tissue around the implant site shows extensive glial encapsulation around both bare and Nafion-coated devices. However, the lesion around bare electrodes has a rough texture implying that these cells are strongly adsorbed onto the bare reference electrode, while the lesion around a Nafion-coated electrode shows that cells are more intact implying that they adsorb less strongly. Energy dispersive X-ray spectroscopy and scanning electron microscopy analysis of the surface of the electrodes confirms this by visualizing a heavy buildup of plaques, organic in nature, only on bare electrodes. Impedance spectroscopy indicates no difference between the impedance of bare and Nafion-coated Ag/AgCl electrodes, indicating that glial encapsulation does not lead to an increase in uncompensated resistance between the working and reference electrodes. The electrochemical shift therefore must be due to the unique chemical microenvironment around the reference electrode that alters the chloride equilibrium, a process that the Nafion coating prevents.