Over-pulsing degrades activated iridium oxide films used for intracortical neural stimulation
Over-pulsing degrades activated iridium oxide films used for intracortical neural stimulation
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DOI：
10.1016/j.jneumeth.2004.02.019
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发表时间：
2004-08-30
影响因子：
3
通讯作者：
McCreery, DB
中科院分区：
文献类型：
--
作者：
Cogan, SF;Guzelian, AA;McCreery, DB
微电极使用活化的氧化铱（AIROF）电荷注入涂层已在猫皮层中的水平从近阈值的神经兴奋的报告在体外电化学电荷注入限制的AIROF脉冲。微电极经受连续的双相电流脉冲，使用0.4V（相对于Ag\AgO 2]）阳极偏压，具有相等的阴极和阳极脉冲宽度，在50 Hz或100 Hz的频率下持续长达7 h的时间。在电荷密度为3 mC/cm（2）时，组织学显示在电荷注入部位附近的组织中存在含铱沉积物，对固定电极进行扫描电子显微镜检查发现AIROF涂层增厚且粘附性差。以2 mC/cm（2）或更低的脉冲微电极保持完整，组织中没有非生物沉积物的组织学证据。在体外相同脉冲条件下挑战的AIROF微电极的反应相似，以3 mC/cm（2）脉冲的电极在100 Hz脉冲（总共10，000个脉冲）仅100 s后显示出AIROF分层的证据，而以2 mC/cm（2）在50 Hz脉冲7 h（总共1.3 x 106个脉冲）的电极没有显示出损坏的证据。在缓冲生理盐水中的体外电化学电势瞬态测量表明，将AIROF极化超过水电解的电势窗口（相对于AglAgO 2为-0.6至0.8V）导致观察到的降解。(C)2004 Elsevier B. V.保留所有权利。
Microelectrodes using activated iridium oxide (AIROF) charge-injection coatings have been pulsed in cat cortex at levels from near-threshold for neural excitation to the reported in vitro electrochemical charge-injection limits of AIROF. The microelectrodes were subjected to continuous biphasic current pulsing, using an 0.4 V (versus Ag\AgC]) anodic bias with equal cathodal and anodal pulse widths, for periods up to 7 h at a frequency of either 50 Hz or 100 Hz. At charge densities of 3 mC/cm(2), histology revealed iridium-containing deposits in tissue adjacent to the charge-injection sites and scanning electron microscopy of explanted electrodes revealed a thickened and poorly adherent AIROF coating. Microelectrodes pulsed at 2 mC/cm(2) or less remained intact, with no histologic evidence of non-biologic deposits in the tissue. AIROF microelectrodes challenged in vitro under the same pulsing conditions responded similarly, with electrodes pulsed at 3 mC/cm(2) showing evidence of AIROF delamination after only 100 s of pulsing at 100 Hz (10,000 pulses total), while electrodes pulsed at 2 mC/cm(2) for 7 h at 50 Hz (1.3 x 106 pulses total) showed no evidence of damage. In vitro electrochemical potential transient measurements in buffered physiologic saline indicate that polarizing the AIROF beyond the potential window for electrolysis of water (-0.6 to 0.8 V versus AglAgC]) results in the observed degradation. (C) 2004 Elsevier B.V. All rights reserved.