Duan Y Y, Clark G M, Cowan R S C
Co-operative Research Centre for Cochlear Implant and Hearing Aid Innovation, The Bionic Ear Institute, 2F/32 Gisborne Street, East Melbourne, Vic. 3002, Australia.
Biomaterials. 2004 Aug;25(17):3813-28. doi: 10.1016/j.biomaterials.2003.09.107.
This paper presents methods, results and analysis for measurements of the electrochemical impedance of platinum electrodes (approximately 0.43 mm2) over a 6-month implantation in the cat cochlea. The study aimed to improve our understanding of the effects of tissue response on impedance behaviour. An increase in impedance in the post-operative period was evident with a rise of the distorted arc at high frequencies in the complex plane, correlating to anomalous charge transport at the electrode-tissue interface. The impedance at low frequencies generally showed a capacitive dispersion modelled as a constant phase element, indicating a blocking characteristic of the electrodes. The study suggests that a reduction and changes in composition of perilymph or extracellular fluid adjacent to the electrodes, as a consequence of tissue response, causes the elevated "contact impedance". This affects the efficiency and quality of neural stimulating electrodes and neural recording electrodes. The finding of the crucial role of perilymph or extracellular fluid thin layer provides a new strategy for surface materials of neural electrodes, which is discussed in the paper. The interface characteristics must be considered during interpretation of studies undertaken in vitro or in acute experiments in vivo, where physiological fluid is abundant.
本文介绍了对铂电极（约0.43平方毫米）在猫耳蜗中植入6个月期间电化学阻抗测量的方法、结果及分析。该研究旨在增进我们对组织反应对阻抗行为影响的理解。术后阻抗增加明显，复平面中高频处畸变弧上升，这与电极 - 组织界面处异常的电荷传输相关。低频处的阻抗通常表现为以常相位元件建模的电容性弥散，表明电极具有阻断特性。该研究表明，由于组织反应，电极附近外淋巴或细胞外液的减少及成分变化导致了“接触阻抗”升高。这影响了神经刺激电极和神经记录电极的效率及质量。外淋巴或细胞外液薄层关键作用的发现为神经电极表面材料提供了一种新策略，本文对此进行了讨论。在解释体外或体内急性实验（其中生理液体丰富）的研究时，必须考虑界面特性。
